the international exploration of mars

4th COSMIC STUDY OF THE IAA

THE INTERNATIONALEXPLORATION OF MARS

Compiled by theInternational Academy of Astronautics (IAA)

Committee on International Space Plans and PoliciesSubcommittee on the International Exploration of Mars

INTERNATIONAL ACADEMY OF ASTRONAUTICSBP 1268-16

75766 Paris Cedex 16

IAA Mars Cosmic Study Report 2

France


TABLE OF CONTENTS

page

FOREWORD v

INTERNATIONAL EXPLORATION OF MARS SUBCOMMITTEE CHARTER vi

IAA MARS COSMIC STUDY REPORT PRIMARY CONTRIBUTORS vii

INTERNATIONAL EXPLORATION OF MARS SUBCOMMITTEE MEMBERS viii

IAA MARS COSMIC STUDY REPORT LIST OF CONTACTS ix

IAA MARS COSMIC STUDY REPORT SCHEDULE x

PREFACE xi

IAA MARS COSMIC STUDY REPORT EXECUTIVE SUMMARY xii

Chapter 1 INTRODUCTION 1

Chapter 2 WHY MARS? 11

Chapter 3 WHY INTERNATIONAL? 19

Chapter 4 MARS AUTOMATED MISSIONS AND PRECURSORS 28

Chapter 5 OPTIONS FOR HUMAN EXPEDITIONS TO MARS 40

Chapter 6 MARS SURFACE SYSTEMS AND OPERATIONS 61

Chapter 7 HUMAN FACTORS AND PHYSIOLOGICAL ASPECTS 79

Chapter 8 MARS PROGRAM ORGANIZATION AND LEGAL ASPECTS 93

Chapter 9 ECONOMIC AND RESOURCE CONSIDERATIONS 100

Chapter 10 CONCLUSIONS AND RECOMMENDATIONS 108

REFERENCES 111

Addendum I UPDATE OF MARS EXPLORATION PROGRAMS - c1995 117

Addendum II MARS DIRECT : A PRACTICAL LOW-COST APPROACH TO

NEAR-TERM PILOTED MARS MISSIONS

125

Addendum III MISSION PLANNING AND MARS ARCHITECTURE

TRADE-OFFS

136

Appendix A A SHORT GUIDE TO MARS 144

Appendix B INTERNATIONAL EXPLORATION OF MARS SURVEY - c1992 151

Appendix C INTERNATIONAL SPACE EXPLORATION INSTITUTE 160

Appendix D ADDITIONAL BIBLIOGRAPHY ON EXPLORATION OF MARS 165


LISTING OF FIGURES

pageFigure 1.1: U.S. Viking Mars Lander 4Figure 1.2: USSR Phobos Probe 4Figure 1.3: Original Concept of Space Exploration Program Proposed by

W. von Braun6

Figure 2.1: Mars 11Figure 4.1: U.S. NASA Mars Observer 30Figure 4.2: Mars Satellite Network 30Figure 4.3: Russian Mars 98 Mission Balloon Station 31Figure 4.4: Mars Crew plus Cargo Lander Concept 34Figure 4.5: Russian Mars 98 Mission Rover 35Figure 4.6: Mars Pathfinder (MESUR) Microrover 36Figure 5.1: Mars Mission Drivers 41Figure 5.2: Opposition and Conjunction Profiles 43Figure 5.3: Venus Swing-by Profiles 44Figure 5.4: Split Cycler System - Inbound Split Cycler Trajectory 45Figure 6.1: Conceptual Illustration of the Strategic Approach 62Figure 6.2: Possible Basing Options 62Figure 6.3: Derived Requirements for the Mars Surface Systems 67Figure 6.4: Implementation of Operational Concept 68Figure 6.5: A Possible Implementation of the Outpost Subphase 70Figure 6.6: A Possible Implementation of the Base Subphase 71Figure 6.7: Placement of Footpads 3 and 2 of Viking Lander 72Figure 6.8: Surface Payload Unloading and Deployment 74Figure 6.9: Power Module Nuclear Reactor 74Figure 6.10: Buried Structure and Shielding with Regolith Bags 76Figure 7.1: Centers Initiated by NASA to Investigate Life Science Space

Flight Issues82

Figure 7.2: EVA and EHA Spacesuit Issues 91Figure 8.1. Space Activities Over The Next 25 Years 97Figure 9.1: World Funding Availability for the International Mars Mission 102Figure 9.2 Real GNP Growth per Person 103Figure 9.3: Cost Growth Factor for Parallel Contractor Organizations 105Figure 9.4: Program Costs 107Figure II.1: An Iconographic Depiction of the Mars Semi-Direct Mission Sequence 128Figure II.2: Average Trip Time Outbound to Mars for the Years 2003-2011 130Figure II.3: Transit Times from Mars to Earth for the Years 2007-2013 130

1.1

1.2

2.1

4.1

4.2

4.3

4.4

4.5

4.6

5.2

5.3

5.4

6.1

6.2

6.6

6.7.a

6.7.b

6.8

6.9

7.2

9.3


LISTING OF TABLES

pageTable 5.1: Typical High-Thrust Abort Options by Mission Phase 48Table 6.1: Allocation of Goals to Functional Implementation Categories 64Table 7.1: Potential Medical Consequences From Long-Duration

Exposure To Space Flight Factors83

Table 7.2: Three Scenarios For a One-Way Trip To Mars: Severity Of Possible Biomedical Changes

84

Table 9.1: Cost and Payload Size for Some Large Launch Systems 101Table 9.2: U.S. Real Economic Growth 1800 to 1985 102Table I.1: Members of IMEWG 118Table I.2: Scientific Observations to be Made by PLANET-B 120Table II.1: Payload Delivery to Martian Surface via 200-tonne-to-LEO HLLV 131Table II.2: Cargo and Piloted Payloads for the Mars Semi-Direct Mission 132Table II.3: Consumable Requirements for Mars Semi-Direct Mission with

Crew of 4133

Table II.4: Mass Allocations for Two-Launch Mars Semi-Direct Mission Plan 133Table III.1: Launch Costs 138Table A.1: Dynamical Properties 145Table A.2: Physical Data 145Table A.3: Mars Opposition Distances Through 2050 146Table A.4: Characteristics of Phobos and Deimos 146Table A.5: Elemental Composition of the Viking 1 Lander Site 147Table A.6: Chemistry of the Viking 1 Lander Site 147Table A.7: Properties of the Mars Top-Regolith 148Table A.8: Comparison of Viking 1 Landing Site and Lunar Soil Properties 148Table A.9: Composition of the Martian Lower Atmosphere 148Table A.10: Summer, Mid-Latitude, Daily-Mean Atmosphere of Mars 149Table A.11: Isotope Ratios in Atmospheric Gases 150Table A.12: Meteorological Properties 150Table A.13: Durations of Seasons on Mars 150Table B.1: Tabulation of IAA International Mars Exploration Questionnaire 156Table B.2: Replies and Average Scores for Each Question 158


FOREWORD

The IAA Subcommittee on the International Exploration of Mars convened for its first meeting in October 1991, at the 42nd International Astronautical Congress in Montreal, Canada. A Mars Exploration Workshop was subsequently held in Cannes, France, May 17-22, 1992, hosted by Aerospatiale Co. The Workshop produced a first draft Mars Report* of the Subcommittee on the International Exploration of Mars. The mission environment in which the Subcommittee worked, and the general human planetary exploration assumptions under which the Subcommittee's Report was developed, were those prevalent at that time. In Europe, the studies then going on in the European Space Agency (ESA) included examination of the Hermes (spaceplane), Aerospatiale's Marsnet, and Columbus. In Russia, the Mars '94 and '96 Missions were in planning. In the United States, President George Bush had already proclaimed the Space Exploration Initiative (SEI) which included a return to the Moon, "this time to stay," followed by unmanned precursors and robotic explorers of Mars, and, ultimately, by human exploration of Mars.

The political climate was that following the collapse of the Berlin Wall and the cessation of the Cold War, with significant political and economic changes in the West and in the former Soviet Eastern bloc countries. The World was expecting a "peace dividend" which might be utilized for societal benefits, for a number of major "grand challenges" on behalf of all humanity, and for the improvement of life here on Earth. The Subcommittee suggested strongly in its 1993 Mars Report that automated and human Mars exploration activity could be a major benefit for humanity and would provide focusing opportunities for the World to learn to work together and to de-emphasize confrontation, hostility and wars.

Unfortunately, the ensuing years have seen major financial deficit problems in all of the developed and developing countries of the globe, leading to corresponding cutbacks in space budgets. Particularly hard hit were the budgets for long term human space exploration beyond the assembly of the International Space Station (ISS) in low Earth orbit. As a consequence, the work and research of the Subcommittee embodied in this Mars Report must look to a future time period for its full realization.

In the meantime, additional highly sophisticated automatic vehicles are under development for exploration of the planetology and atmosphere of Mars. At the same time, mission planners have identified more austere human Mars exploration projects reminiscent of the early human explorations of the North Pole and the Antarctica. In those cases, small groups of people took calculated risks to bring back singular information for humanity that has had a wide impact on our understanding of the Earth. In that spirit, a number of imaginative and sophisticated concepts have come forth which suggest the possibility of direct exploration of Mars with subsequent development of bases depending on some of the outcomes and relying heavily on in situ resources. The Subcommittee thus presents in this booklet its Mars Cosmic Study on The International Exploration of Mars, augmented with Addenda that describe updates and subsequent contributions. This Mars Cosmic Study Final Report contains four parts:

¥ IAA Mars Cosmic Study - The International Exploration of Mars;¥ Addendum I: Update Of Mars Exploration Programs - c1995;¥ Addendum II: Mars Direct: A Practical Low-Cost Approach To Near-Term

Piloted Mars Missions;

* Published in Acta Astronautica, Vol. 31, pp. 1- 126, 1993, and presented to the IAA at the 44th World Space Congress, Graz, Austria, October 16, 1993.


¥ Addendum III: Mission Planning and Mars Architecture Trade-Offs.

The present era is a time when it cannot be predicted accurately which automated Mars probes and which human Mars expedition architecture will ultimately be implemented. It has been the goal of this study to present a variety of credible architectures and to emphasize the desirability of establishing an International Space Institute to get on with the international exploration of Mars planning. It was felt to be important, however, to summarize the various Mars exploration concepts in this Mars Cosmic Study and to identify the management, political, and leadership issues which must be resolved to achieve success, as well as to identify the present state of planetary exploration technology. It is important to know what must yet be done in research and development to achieve this major goal of humanity. In this spirit, this Mars Cosmic Study is placed before the IAA and before the leaders of the world's space organizations in the hopes that it will keep alive the age-old Mars exploration goals of mankind so that they may be realized at the earliest possible time.

George W. MorgenthalerProfessor, Aerospace Engineering Sciences, University of Colorado at BoulderChair, Subcommittee on the International Exploration of Mars

INTERNATIONAL EXPLORATION OF MARS SUBCOMMITTEE CHARTER

¥ The Subcommittee shall collect, condense, organize, and disseminate all relevant information and the available options for a project leading to an "International Exploration of Mars."

¥ The Subcommittee shall hold a planning session on October 5, 1991, at the 42nd Congress of the International Astronautical Federation in Montreal, Canada.

¥ The Subcommittee shall organize a working session during the 1992 World Space Congress at Washington, D.C., U.S.A.

¥ The Subcommittee shall draft an IAA position paper by November 1994 IAA Meeting, with a preliminary report due by August 1992, with the objective to show the ways and means on how an international program of flight to Mars could be initiated, with the ultimate goal to establish a Mars base.

¥ Members of the IAA shall be encouraged to make contributions during the development of this paper and opportunity shall be given for IAA members to voice their opinions.

¥ The Subcommittee will not choose specific Mars projects; it will illustrate credible Mars exploration alternatives and advocate an International Exploration Initiative to begin now.

¥ Prof. Dr. George W. Morgenthaler, Aerospace Engineering Sciences Department, University of Colorado, Boulder, Colorado, USA, has been appointed chairman of this Subcommittee by the President of the IAA, Dr. George E. Mueller.


IAA MARS COSMIC STUDY REPORT PRIMARY CONTRIBUTORS

Editors: George W. Morgenthaler, Gerald J. Smith

PrefaceGeorge E. Mueller

Chapter 1 : IntroductionGeorge W. Morgenthaler, Maria A. Perino, Wendell Mendell

Chapter 2 : Why Mars?Marcello Coradini, Michael B. Duke, Harald Hoffman, Michel Mabile, Philippe Masson

Chapter 3 : Why International?Uwe Apel, Ivan Bekey, Jacques Collet, Jean-Michel Contant, Michael B. Duke, Dale Fester, Harald Hoffman, Maria A. Perino, Ian Pryke, William C. Schneider

Chapter 4 : Mars Automated Missions and PrecursorsJacques Blamont, Michel Cathala, Ben Clark, Marcello Coradini, Ralph Eberhardt, Dale Fester, Francis Giovagnoli, Mikhail Marov, Wendell Mendell, Josette Runavot

Chapter 5 : Options for Human Expeditions to MarsMax Grimard, Jerry Sellers, Gordon Woodcock

Chapter 6 : Mars Surface Systems and OperationsLarry Bell, Alessandro Bichi, Chris McKay, Barney B. Roberts, Francis Theillier

Chapter 7 : Human Factors and Physiological AspectsCarl Case, Bob Cheung, Michael Fry, Victoria Garshnek, Ken Money, Gerald J. Smith, John Uri, Francis Winisdoerffer

Chapter 8 : Mars Program Organization and Legal AspectsAlvaro Azcarraga, Richard Barnes, Michel Bignier, Richard Boudreault, Jean Loup Chretien, Marcello Coradini, Michael Duke, Hal Emigh, Chen Fangyun, Eilene Galloway, Max Grimard, James Harford, Yang Jiachi, Jack Leeming, Joseph Loftus, Yasunori Matogawa, Chris McKay, George W. Morgenthaler, Charles Ordahl, Maria A. Perino, Ian Pryke, Gerald J. Smith, William Smith, James J. Spaeth, Seishi Suzuki, Ernesto Vallerani

Chapter 9 : Economic and Resource ConsiderationsGeorge W. Morgenthaler, Ivan Bekey

Chapter 10 : Conclusions and RecommendationsWendell Mendell, George W. Morgenthaler

Addendum I : Update of Mars Exploration Programs - c1995Ben Clark, Michael B. Duke, Mikhail Marov, Ichiro Nakatani, Josette Runavot, Donna Shirley

Addendum II : Mars Direct: A Practical Low-Cost Approach to Near-Term Piloted Mars Missions


Robert Zubrin

Addendum III : Mission Planning and Mars Architecture Trade-OffsGordon Woodcock

Appendix A : A Short Guide to MarsChristopher P. McKay

Appendix B : International Exploration of Mars Survey Results - c1992Gerald J. Smith and Edward Barrett

Appendix C : International Space Exploration InstituteGeorge E. Mueller

Appendix D : Additional Bibliography on Exploration of MarsMarcia Smith and Michael B. Duke

Editorial Advisory PanelRoger Bourke, Ben Clark, Jean-Michel Contant, Michael B. Duke, Dale Fester, Hermann Koelle, Douglas A. O'Handley, Frederick I. Ordway III, Harry Ruppe, Gordon Woodcock, Robert Zubrin

Student Assistants: Ted Barrett, Juan Esguerra, Scott Georgi, Russ Riecken

Special thanks to Aerospatiale for their assistance in hosting Subcommittee Workshops and for reproduction and distribution of the various draft versions of this Report.

INTERNATIONAL EXPLORATION OF MARS SUBCOMMITTEE MEMBERS

(All Subcommittee Members contributed to this Report, but are not individually responsible for, or in accord with, every statement therein.)

Alvaro Azcarraga (Spain) Peter Bainum (U.S.)Richard J.H. Barnes (U.S.)Alexander Basilevsky (Russia)Patrick Baudry (France) Ivan Bekey (U.S.)Larry Bell (U.S.)Lev Belyaev (Ukraine)Franco Bevilacqua (Italy)Alessandro Bichi (France)John Billingham (U.S.)Jacques Blamont (France)Richard Boudreault (Canada)Roger D. Bourke (U.S.)Jim Burke (U.S.)Michael Carr (U.S.)

Carl M. Case (U.S.)Ben Clark (U.S.)Aaron Cohen (U.S.)Jacques Collet (France)Jean-Michel Contant (France)Marcello Coradini (France)Donald DeVincenzi (U.S.)K.H. Doetsch (Canada)Michael B. Duke (U.S.)Bryan Erb (Canada)John Fabian (U.S.)Dale Fester (U.S.)Michael Fry (U.S.)Nobuyoshi Fugono (Japan)Alexis A. Galeev (Russia)Eilene Galloway (U.S.)

Francis Giovagnoli (France)Gottfried Greger (Germany)Max Grimard (France)Luciano Guerriero (Italy)James J. Harford (U.S.)Hiroshi Hieda (Japan)Harald Hoffman (Germany)James D. Van Hofton (U.S.)Steven D. Howe (U.S.)William G. Huber (U.S.)Yoshihiro Ishizawa (Japan)Shigeyuki Itow (Japan)K. Kasturirangan (India)Jean-Pierre Kernevez (France)Larkin Kerwin (Canada)Dietrich E. Koelle (Germany)


Hermann Koelle (Germany)Wiley Larson (U.S.)Joseph P. Loftus, Jr. (U.S.) Jean-Marie Luton (France)Michel Mabile (France)Mikhail Marov (Russia)Philippe Masson (France)Takefumi Matsui (Japan)Shinji Matsumoto (Japan)Chris McKay (U.S.)Richard Meehan (U.S.)Wendell W. Mendell (U.S.)Angelo Miele (U.S.)

Ken Money (Canada)George W. Morgenthaler (U.S.)Gerhard Neukum (Germany)Douglas A. O'Handley (U.S.)Charles A. Ordahl (U.S.)Alain Pave (France)Lubos Perek (CSFR)Maria A. Perino (Italy)Robert Pfeiffer (Netherlands)Ian Pryke (U.K.)Barney B. Roberts (U.S.)Francis Rocard (France)Josette Runavot (France)

Harry O. Ruppe (Germany)Willy Z. Sadeh (U.S.)William C. Schneider (U.S.)Jerry Jon Sellers (U.S.)Oleg N. Shishkin (Russia)S. Fred Singer (U.S.)Vladimir Smetannikov (Russia)Tasuku Tanaka (Japan)Francis Theillier (France)Francis Winisdoerffer (France)Gordon R. Woodcock (U.S.)Tatsuo Yamanaka (Japan)Michael I. Yarymovych (U.S.)


IAA MARS COSMIC STUDY REPORT LIST OF CONTACTS

Chair: George W. Morgenthaler** University of Colorado, Eng. Center, C/B 0429, Boulder, CO 80309-0429 USA

(ph) 303-492-3633, (fax) 303-492-5514

Secretary: Wendell Mendell** NASA Johnson Space Center, Bldg. 31, Rm. 149, Mail SN14, Houston, TX 77058 USA

(ph) 713-483-5064, (fax) 713-483-5347

Panel Leaders(Please direct specific correspondence to Chair, with copies to individual Panel Leaders)

Why Mars?: Michael B. Duke** Lunar and Planetary Institute, 2262 Gemini Dr., Houston TX 77058 USA

(ph) 713-244-2036, (fax) 713-244-2006

Why International?: Ivan Bekey *, Ian Pryke **, William C. Schneider* NASA Headquarters, Mail Code XZ, Washington, D.C. 20546 USA

(ph) 202-358-4561, (fax) 202-358-2921;** ESA Washington Office, 955 L'Enfant Plaza,

Washington, D.C. 20024 USA(ph) 202-488-4158, (fax) 202-488-4930

Mars Automated Missions Precursors: Mikhail Marov *, Ben Clark* Keldysh Inst. of Applied Mathematics, Miusskaya Square 4, Moscow 125047 Russia

(ph) 7-095 250 0485, (fax) 7-095 972 0737

Options for Human Expeditions to Mars: Gordon Woodcock *, Harry Ruppe* Boeing Defense and Space Group, 499 Boeing Blvd., M/S JW-21,

P.O.Box 240002, Huntsville, AL 35824-6402 USA(ph) 205-461-3954, (fax) 205-461-2730

Mars Surface Systems and Operations: Barney B. Roberts** Futron Corp., 1120 NASA Road 1, Suite 310, Houston, TX 77058 USA

(ph) 713-333-0190, (fax) 713-333-0192

Human Factors and Physiological Aspects: Ken Money** Canadian Space Agency / DCIEM, P.O.Box 2000, Downsview, Ontario Canada M3M3B9

(ph) 416-635-2121, (fax) 416-635-2104

Mars Program Organization and Legal Aspects: James Harford** 601 Lake Drive, Princeton, NJ 08540 USA

(ph) 609-683-5542, (fax) 609-683-5542

Addendum I: Ben Clark** Lockheed Martin, P.O. Box 179, Mail Stop B0560, Denver, CO 80201 USA

(ph) 303-971-9007, (fax) 303-971-9141


Addendum II: Robert Zubrin** Pioneer Astronautics, P.O. Box 273, Indian Hills, CO 80454 USA

(ph) 303-980-0890, (fax) 303-980-0753

Addendum III: Gordon Woodcock** (see above)


IAA MARS COSMIC STUDY REPORT SCHEDULE

April/May 1991 Selection of Subcommittee Chair (George W. Morgenthaler).Selection of Subcommittee Panel Leaders and Members.

October 1991 Mars Subcommittee Planning Session held at the 42nd Congress of the International Astronautical Federation, Montreal, Canada (Oct. 5).

February 1992 Progress report given at IAA Board of Trustees Meeting, Bordeaux, France; Version 1.0 of Mars Cosmic Study Report presented.

May 1992 Version 2.0 of Mars Report compiled and mailed to Subcommittee.

May 1992 Workshop in Cannes, France (May 17-22).

June 1992 Cannes Version 3.0 circulated to Workshop participants (~40).

August 1992 Version 4.0 & 4.1 circulated to IAA Board of Trustees and Subcommittee.Two International Exploration of Mars Subcommittee Workshops held.Presentation of Mars Study at National Academy of Sciences and 43rd World Space Congress, Washington, D.C., USA (Aug. 27 - Sept. 1).

October 1992 Panel Leaders submit section updates to Mars Subcommittee Chair.

December 1992 Mars Subcommittee Chair submits Version 5.0 to IAA HQ, Paris.IAA mails Version 5.0 to International Space Plans and Policies Committee members and IAA Board of Trustees for review.

February 1993 Reviewers submit comments to Subcommittee Chair and Panel Leaders.Panel Leaders submit revised sections to Mars Subcommittee Chair.

March 1993 Presentation to IAA Board of Trustees and IAA Committee on International Space Plans and Policies in Paris, France; Mars Subcommittee Workshop held 30 March 1993.

April 1993 Editorial Advisory Panel submits comments to Mars Subcommittee Chair.Mars Subcommittee Chair submits Version 6.0 to IAA HQ, Paris for publication in Acta Astronautica.

July 1993 Version 6.0 published in Acta Astronautica, Vol. 31, and circulated to IAA membership as an IAA Position Paper.

October 1993 Presentation to IAA Board of Trustees at Academy Day and reviewed by Rapporteurs at 44th International Astronautical Congress, Graz, Austria.

October 1994 Revised and updated at 45th International Astronautical Congress, Jerusalem, Israel (Oct. 24).

October 1995 Version 7.0 presented for publication as an IAA Mars Cosmic Study at


46th International Astronautical Congress, Oslo, Norway (Oct. 3).

December 1995 Final comments submitted to Mars Subcommittee Chair.

August 1996 Final Version 7.1 submitted to IAA HQ, Paris.


PREFACE

"Provide ship or sails adjusted to the heavenly breezes, and there will be some unafraid even of that empty void [of space]. So, for those who will come shortly to attempt this journey, let us establish the astronomy: Galileo you of Jupiter, I of the Moon." - open letter to Galileo Galilei from Johannes Kepler, 19 April 1610.

Over the years, space discoveries and space activities have generated broad public support and acclaim. The implementation of an evolutionary series of space exploration projects can provide short-term (3 to 4 year) spectacular results while forcing the creation of leading edge technologies and laying the foundation for viable international collaboration.

Thus the International Academy of Astronautics has embarked on a series of "Cosmic Studies," designed to fully explore the many aspects of the implementation, impact, and rewards of cooperative international programs for the exploration and ultimate possible habitation of the Solar System and beyond. In these Cosmic Studies the IAA is attempting to provide International leaders and decision makers of the spacefaring countries of the world an unbiased scientific and technological basis for their commitment to multinational space programs. These Cosmic Studies are designed to provide a knowledgeable technical perspective and assessment of proposed programs as a basis for governmental decisions. This Mars Cosmic Study examines the possibilities and implications of establishing an international robotic and human space exploration program leading to the establishment of an International Mars Base.

The International Academy of Astronautics and the International Exploration of Mars Subcommittee thanks Aerospatiale, Boeing, the University of Colorado and other companies, agencies, and universities that have supported the participation of its experts in the preparation of this Mars Cosmic Study. Comments on this Study should be sent to IAA Headquarters in Paris at the address shown on the cover page.

George E. MuellerPresidentInternational Academy of Astronautics


IAA MARS COSMIC STUDY REPORT EXECUTIVE SUMMARY

Chapter 1 - IntroductionThe journey to Mars is discussed in this IAA Mars Cosmic Study. The time has now come to lay plans for an intensified international robotic exploration of Mars, leading to an International Human Mars Exploration Project. It is the purpose of this Mars Cosmic Study to review the background for such an international robotic/human Mars program and to press for action. The advancement of knowledge, including the further unraveling of the mysteries of the cosmos, is a human endeavor, yielding to those willing to invest appropriate intellectual and physical resources. Resultant discoveries enter the repository of human understanding, benefiting all inhabitants of the planet. As space exploration has matured, the scientific community has become more international in its collaborations, and political constraints are viewed more and more as impediments to progress. The explosive growth of space activities, previously driven by political competition, is now beginning to react to economics.

The IAA position is that an international project of expanded robotic and human space exploration of Mars can provide a vision of new beginnings with fresh perspectives. Robotic spacecraft generally have acquired data according to the preprogrammed expectations of their creators. This limitation will change with future automated spacecraft, but currently only a human space explorer can acquire knowledge through creative, real-time organization of information, while also learning to live and work in space. The cost of human exploration of Mars raises questions of cost/benefit. Mars offers a rich menu of scientific exploration opportunities, but the potential cost of human Mars exploration demands more than just science return. Human Mars exploration would teach us how to create small, self-sufficient, closed-cycle biospheres. The resulting knowledge and technology will help us protect Earth's natural biosphere.

The benefits, especially the cultural ones, are best realized by an international program. It is up to us to find a mission architecture and pace of development for a feasible international program that does not too strongly compete with Earthly needs for scarce resources. If the program uses existing aerospace facilities and personnel resources, e.g., surplus resources from declining military programs, and spreads the costs internationally, then additional resource costs may be affordable. Participation in such a program at an appropriate level will also help developing countries create technological and industrial infrastructures capable of enhancing worldwide sustainable economic growth.

We are confident that we can extend our capabilities to human interplanetary journeys. Such voyages of discovery can be undertaken before we fully understand the long-term response of a human being to the environment present in the crew quarters of the space habitat, but at some risk to the crew. We shall gain a significant amount of data regarding human adaptation to microgravity and isolation on long space missions such as a human mission to Mars. We shall also learn to design and build-in true long-term reliability of our mechanical and electronic systems.

Chapter 2 - Why Mars?Mars, the next planet out from the Sun beyond the Earth, although cold and wind-swept, is still the most Earth-like of all the other Solar System planets. On its surface are huge volcanoes, deep canyons, vast flood channels, and extensive sand seas. The diameter of Mars is a little over half that of the Earth and gravity at the surface of Mars is .38 that of the Earth. The atmosphere is thin and consists mostly of carbon dioxide. The pressure at the surface is about 1/100 that at the Earth's surface, and it changes with the Martian season as part of the carbon dioxide in the atmosphere


freezes out on the pole to form a polar ice cap during winter. At the equator, surface temperatures range from about -90¡C at night to +20¡C at noon, overlapping temperature conditions found on Earth. On the carbon dioxide polar caps, temperatures can drop to -120¡C. It is of great scientific importance to explore, document, and analyze the processes that have turned Mars into a barren, inhospitable domain.

Some space scientists believe that all Mars resource expenditures should be confined to robotic exploration of Mars, at least through the first half of the 21st Century, and that to implement a human expedition to Mars would be too costly. They believe that a human expedition would severely drain funds and "starve" research efforts in robotic space exploration, aeronautics, basic science research, and industrial research. Others feel that space exploration for science alone is too narrow a goal. They believe that human progress overall would be stimulated and even scientific and basic research objectives would be attained faster if a mix of robotic and human space exploration is performed in parallel. Humanity reveres and supports science, but society also values exploratory journeys of the human spirit. The point of view of this Mars Cosmic Study Report is that an international program of automated Mars probes and precursors in parallel with human missions to Mars will best serve humanity.

Mars has special significance for what it may reveal about the origin and evolution of Earth-like planets and the origin of life. Although Mars is compositionally similar to the Earth, it has evolved quite differently. While the Earth is a fertile, tectonically and volcanically active planet, Mars evolved into a frigid, relatively inactive and sterile body. Why did the two planets evolve so differently? Part of the answer will come from further intense studies of the Earth. But such studies should be accompanied by complementary intense studies of Mars.

Because of the implications for life and global change on the Earth, the climatic history of Mars is of particular interest. Liquid water cannot exist on the surface of the present-day Mars. Surface conditions are such that it will freeze or sublime. Yet ancient surface features show abundant evidence of water erosion. Orbiter pictures of the surface show numerous ancient, branching dry river valleys, seemingly cut by running water. The valleys attest to both the abundance of water during those former times, and to climatic conditions that permitted liquid water to flow across the surface. What were the climatic conditions during those times and why did the climate change? If conditions on Mars were similar to the early Earth, did life arise on Mars as well?

Few scientific questions, such as whether life ever existed on Mars, will be answered by one simple experiment. Only by addressing a range of interrelated geological, atmospheric and biological issues will the major questions ultimately be resolved. Some of the principal research areas are the following:

Composition and internal structureThe level of our current knowledge of Mars is quite primitive. For example, we do not know the mineralogy or chemical composition of its principal rock types, and thus we do not know the planet's bulk composition.

Geological evolution and agesThe relative chronology of Mars' major surface features is known in a general way; however, absolute ages can only be gained through the analysis of samples.

External processes


The Mars system (including Phobos and Deimos) was bombarded throughout geological time by the same population of meteoroids and the same radiation environment encountered by the Moon and Earth. What were the specific effects for Mars?

Composition and dynamics of the atmosphereThe Mars atmosphere, although much thinner than the Earth's, is a natural planetary laboratory in which to test models of atmospheric processes that are applicable to Earth.

Water in Martian historyMars is of great interest because it exhibits evidence of past surface water and this hints at Mars having had different atmospheric conditions in the past than today. We have much speculation, but little hard evidence, pertaining to questions such as the relative roles of water erosion, mass wasting (landslides), wind erosion and wind deposition.

Existence of past or present life on MarsPerhaps the most important single question that can be asked about Mars is, "Did life ever exist there?" The past existence of life on Mars is made plausible by the evidence of water in early epochs. And, if life got a foothold on Mars in its early history, there is a possibility that life exists now, perhaps in some energy-rich environment, protected from the oxidizing effect of the current surface environment. Volcanic fumaroles or warm brines that may exist below permafrost zones are commonly cited as potential life-supporting habitats. The success of strategies for discovering evidence for past or present life on Mars depends significantly on our ability to control the contamination of Mars by terrestrial biological materials, which could confuse the interpretation of sample analyses. The fate of terrestrial organic material introduced into the Mars environment must be understood early in the exploration program.

Mars is the only planet beyond the Earth-Moon system where permanent settlement seems remotely feasible. One of the primary objectives of early Mars exploration should be to determine how practical human settlement really is. Although Mars is more hospitable than any planetary body other than the Earth, it is still very inhospitable. The atmosphere is too thin and of the wrong composition to sustain humans, radiation levels are high, temperatures are low, and the availability of water and other resources are unknown. Early expeditions to the planet should, therefore, include among their goals an assessment of usable resources such as water, oxygen, building materials and thermal energy. A Mars base (or long-term outpost) may require growing food on Mars. Various means of growing food on Mars must therefore be assessed.

It is not possible to foresee in advance exactly what the scientific return from Mars exploration will be. It is because we know so little about Mars that its scientific exploration is so interesting. Each successive automated Mars mission has shown new surprises. Challenging projects, such as a Mars exploration mission, also become vehicles for technology development and demonstration. Robotic missions to Mars must develop greater autonomous capability. Human missions must perform well for time durations that are significantly longer and more demanding than any previous human space flights. Accomplishing these missions can be the focus of sustained interest and investment in technological advancement, thereby providing motivation for humans to excel in technical fields.

Among the more important challenges that will drive technological advancement and that can produce benefits on Earth are: propulsion and power; human health and adaptation; life support system development, resource utilization, and ecological technologies; increased reliability and lifetime of hardware and systems; automation and robotics; and improvements in new sensors.


Historically, the lack of perspective and challenge in societies often resulted in their stagnation and dissolution. An important characteristic of healthy societies has been the stimulation of innovative ideas to fulfill a challenging vision. Education should involve not merely the acquisition of skills, but an increase in perspective and the elevation of the human spirit. The prospect of the spreading of civilization into the cosmos offers humanity the superb opportunity to achieve continuance, expansion, prosperity and knowledge. Large national challenges such as undertaking space programs and increasing educational opportunities are positively linked historically.

Chapter 3 - Why International?An International Mars Exploration Program, including human missions, is the next step in a series of what has been mostly nationalistic explorations that began in low Earth orbit, sent humans to the Moon, and sent robotic probes to the farthest reaches of the Solar System. An ambitious robotic Mars program is already underway, based on national programs, but with international contributions. Europe, Russia, Japan, and the United States all have, or intend to have, robotic Mars exploration programs. Most will feature a degree of international cooperation.

This document urges the extension of this cooperative international robotics program into a formal International Mars Exploration Program which includes human missions. Past and current studies show that human missions will involve major technological and life support problems, and will require significantly increased resources. Because of the magnitude of this undertaking, coupled with the current geopolitical world situation, humanity should seriously consider making such an extension in a primarily international, rather than primarily national, context.

The rationale for an international context for a Mars Exploration Program is based on philosophical, technological, financial, scientific, and educational factors. All nations stand to gain from participation in the development of fundamentally new technologies. A Mars Program can be so designed that access to knowledge and technology spin-offs is readily available for those nations currently possessing lesser technological capability. Also, when the funds come from several countries, the multiplicity of supporters can sustain the program cash flows through a difficult economic or political period experienced by one individual supporter. Global markets historically emerge for the aerospace products of each participating country.

The Mars Program can have a major impact on education. The training of additional professors, scientists, engineers, and technologists is both necessary to provide the technical depth for a Mars Program, and will be the byproduct of its undertaking. Since education is fundamental to the rise of civilizations and the increase of standards of living, the contributions of the Mars Program to education are among the primary reasons why it should be undertaken.

There are a number of significant challenges that must be overcome if the vision is to be accomplished. The Mars Program may be the most ambitious single peacetime technical project ever undertaken by humanity. Quite apart from the technical challenges that must be solved, a Mars Exploration Program with many nations as participants must nonetheless be managed as an integrated whole. There are a number of models that could be candidates for setting up the required management structure, including some adaptation of the management functional structure of the U.N., ESA, Intelsat, NATO, International Space Station (ISS), Antarctic Base, and others.

The financing of the Mars exploration program will be the next greatest challenge to be faced. To a great extent, the mechanism for obtaining the funds will depend on the management structure


chosen. Consideration will also have to be given to the developing nations. The intent of making the Mars program truly global will have to be balanced against each country's ability to fund its share of the enterprise. Thus the question of some developing nations providing funds versus providing contributed value (such as headquarters sites, launch sites, tracking/communications sites, materials, or human resources) could become important.

Sharing control is a sensitive issue that cuts to the heart of the viability of any international venture. To participate in any international program, each participant must give up some of the management control it normally exercises over its national programs.

A number of benefits would be expected to accrue from an international Mars exploration program. History teaches that the cost of the program's share to any one nation can be smaller, particularly if the program has strong management lines of control. One of the chief benefits of its existence would be the effect on world stability. Historically, programs which involve major international commitments have proved more resistant to adverse political pressures within the undertaking nations. A case can usually be made that space programs brought more long-term return to their nation's economy in the form of goods and services in all industries and sectors than was actually expended on them, with return-on-investment ratios near 7:1, or higher.

There are several reasons why the exploration of Mars is important at this point in the history of the world. These include our perception of the need of the world to have positive beneficial goals that bind nations together, thus creating capabilities to address global technological, economic and environmental problems. Many nations must deal with the problems of converting armament industries to peaceful uses, while retaining technical expertise both for future commercial benefit and for maintaining national defense capability. The wide range of systems and technologies required for Mars exploration, including electronics, power, automation, robotics, materials, propulsion, life support, and others, are among the most productive for national technological advancement.

Chapter 4 - Mars Automated Missions And PrecursorsA great deal of information has already been obtained from the Mariner, Mars, Viking and Phobos spacecraft, but it is necessary to extend those findings to answer new questions in planetary science, comparative planetology and cosmology, and to allow the formulation of a detailed scientific basis for future human flights.

Robotic missions should continue to improve our scientific understanding of Mars and to demonstrate new robotic technology. Scientific robotic missions should be continued even after human landing on Mars. However, robotics can also be used for testing and verification of the human spacecraft systems and other relevant hardware, for development of the strategy and scenario of the initial human mission phase, and for preliminary logistics of cargo delivery. From this point of view, they can be considered as precursors for future human flights to Mars.

The automated missions should collect the basic information in the disciplines of Martian geology, geochemistry, atmospheric sciences, climatology, and exobiology, etc., but also data on the performance of the engineering subsystems. The precursor missions can be the backbone of a Mars scientific program, and in their development of robotic technologies, can complement future human exploration. The automated missions can help in landing site selection and site preparation for human exploration and can be an important part of the human Mars mission development program. Their dual role is not only desirable, but essential to ensure that the effort and expense of getting to


Mars yields valuable scientific results and reduces the risk and cost of human exploration. Robotic precursor missions can also establish the degree to which human presence is a requirement for a more efficient and elaborate study of Mars, and what role automation might be called upon to play in assisting human exploration.

Chapter 5 - Options for Human Expeditions to MarsOnce a crew-carrying Mars ship is in Earth orbit and ready to be launched towards Mars, the sequence is straightforward: interplanetary transfer to Mars, capture in Mars orbit; direct descent to the surface using a lander; surface mission operations; ascent to Mars orbit; possible rendezvous with an orbiting ship; interplanetary transfer back to Earth; capture in Earth orbit; and finally, Earth landing. An automated mission, if it returns a sample to Earth, generally follows the same sequence. If an automated Mars surface mission does not return to Earth, then the sequence ends with the Mars surface mission, just as it did for the Viking spacecraft.

While the basic mission sequence is simple enough, the complexity arises from the choice of mission profile and the choice of interplanetary propulsion system(s). There are two basic mission profiles - a slow, minimum energy transfer; and a much more costly (in terms of propellant required) high energy "fast" transfer, each of which again has several variations. The selection of a mission profile hinges on the selection of a propulsion system or systems. There are currently three propulsion options potentially available to the designer: chemical rockets, nuclear thermal rockets, and electric engines using nuclear or solar power. Of these, only chemical rockets have been safely demonstrated for human missions. Aerobraking and aerocapture into planetary orbit, after an interplanetary trip, can be used with any of these options, adding further choices.

Selection of technical alternatives for missions to Mars must respond to a set of constraints and objectives collectively called "mission drivers." Deciding on the mission and system design is a compromise among conflicting requirements and desires. Engineers must make trade-offs between competing performance requirements. Failure to carefully define priorities between these requirements only leads to potentially harmful compromises and needlessly drives up costs.

Mission objectives affect mission design and system selection through requirements such as crew size, scientific vs. operations cargo characteristics, stay time at Mars, surface site access, and the potential desire for building towards a continuous presence at Mars (e.g., a permanent Mars base). Analysis of skill mix needs indicates a minimum crew number of five to eight for a Mars mission. Greater demands for primary science skills as well as needs for international representation could lead to a larger rather than smaller number of crew. The size and cost of a mission are directly driven by crew size. In recent studies, cost considerations have tended to drive the number of crew to the lower limits of what is believed by the study authors to be a safe and reasonable crew complement.

For an international project, it is essential that the space systems development, production, operations and associated ground and support systems be internationally shared. A Mars mission lends itself well to this end, since there are many major components and a large number of minor ones to be assigned or subcontracted to the international partners.

Chapter 6 - Mars Surface Systems and OperationsThe role of the Mars Surface System is ultimately to provide (with a modest start) a complete spectrum of capability for realization of the international exploration community's goals for robotic and human exploration and possible future settlement of Mars. This robotics/human exploration


capability may include pre-programmed and autonomous robotic systems, teleoperated rovers, stationary geophysical stations, initial Mars human expeditionary outposts, self-supporting human bases, and Mars-based space transportation systems. To plan the Mars Surface System, it is necessary to examine fundamental top level goals, to derive the next level of requirements, and then to conceptualize a set of temporal relationships, interactions, and phase transitions that best describe a strategic approach which ensures accomplishment of those goals.

Goals of Mars exploration require the Mars Surface System to support the collecting of scientific data that increases our understanding of Mars on a global scale and supports the development and verification of Mars as a future abode for humans. Upon examining those two primary goals, the subsidiary goals were categorized under "Exploration", and "Human Expansion". These categories require different implementation schemes. Exploration generally emphasizes "global" Mars coverage with temporary human presence at any single site, and Human Expansion emphasizes growth and evolution outward from a single site with permanent human presence.

A characteristic of the planetary Exploration goal is that it is ultimately desirable to visit a multiplicity of sites. This implies either the capability to travel great distances across the surface of Mars using a mobile "base" concept, or that many sites can be visited from an orbital base or through several separate expeditions to Mars. Elements that provide temporary support associated with limited means and short durations are most appropriate. On the other hand, the Human Expansion goal requires a different approach in that a human settlement begins with a unique landing site from which a surface base infrastructure may grow outward. Within the framework of the Human Expansion goal, it is expected that increasing capability may be provided by utilization of local resources that will enable much longer surface stays, support other goals, and open the way to long-range surface exploration capabilities.

The implementation and operations concepts must not preclude either approach, but rather must provide for the simultaneous implementation of both through the utilization and exploitation of common assets. Indeed, the Human Expansion implementation must evolve through a growth approach that utilizes the Exploration assets. From the other viewpoint, the Exploration assets must not preclude, and wherever possible, must facilitate future growth.

An analysis of the mission-level requirements in Chapter 2, "Why Mars?", has yielded the following basic requirements for the Mars Surface System:

Mars Scientific Goals¥ Understand the composition and internal structure of the planet Mars;¥ Determine the geological evolution and ages of Martian surface features;¥ Determine the composition and dynamics of the Martian atmosphere;¥ Determine the origin and history of water on the surface of Mars;¥ Determine the existence and evolution of life on Mars, extinct and extant.

Mars Habitation Goals¥ Determine the practicality of permanent human settlements on Mars;¥ Determine and evaluate methods to make the human settlements self-sufficient and less

dependent on Earth resupply.

The next step in the requirements analysis process is to assign the above mission level goals to potential functional hardware categories so that the surface system assets can be further defined in


subsequent studies. This is done in the Mars Cosmic Study Report through an iterative process and those goals are allocated to major Mars Surface System functional categories that may contain a number of hardware assets.

The basic strategic approach is to design each phase and sub-phase to be interdependent and supportive of each subsequent phase and sub-phase. This approach results in no "dead-ended" hardware, and, in the long run, should reduce costs in that fewer original development programs will be needed. Although each sub-phase depends on the others, the decision to implement any phase is an independent activity. The sub-phase to sub-phase dependency is implemented through the design process by ensuring the availability of the additional performance capability required to support the subsequent phases when, or if, the decision to advance is made based on international resource availability and priorities. The potential implementation concepts can vary widely depending on the detailed analyses of the requirements and the special interests of the international partners involved. The implementation concepts presented in the IAA Mars Cosmic Study Report are only to demonstrate that there exists at least one solution to the problem.

Chapter 7 - Human Factors and Physiological AspectsAn interplanetary space flight or inhabiting a foreign planet for long durations can subject the crew to debilitating, injurious and possibly fatal stresses. Some of these stresses are radiation, hypogravity, isolation/confinement, toxicity, and mission specific environmental conditions. To be sure that the mission has a high probability of succeeding, it will be necessary to expand human knowledge of these stresses and their human effects over time before undertaking such a flight. Much can be learned by inhabiting and working aboard the International Space Station (ISS).

The planning for the mission should also include consideration of crew selection and performance, habitability of the environments, sociological issues, life support, environmental health, and management of crises and illnesses. The accepted level of risk needs to be decided. We must realize that, inherently, risk cannot be totally eliminated and should not be denied; missions should be designed with prudent levels of risk (possibly a 3% risk of catastrophe). The best way to manage the levels of risk for a mission is to understand the environment and the conditions of that mission, including how a human will be affected and will perform in that environment, and the mitigating benefits of possible control measures.

Human factors and physiological problems will probably not delay the human exploration of Mars, provided the quest for problem solutions begins now. The selection of the crew will be based on physiological, psychological, sociological, and task considerations, and cross training for stable relationships. A significant amount of preliminary work still needs to be performed in the areas of radiation, hypogravity, and isolation/confinement to understand the effects of these stresses. The biological effects of the radiation anticipated en route, on Mars surface, and in case of an abort flight, should be precisely determined. The timing, shielding, and countermeasures should be such that the hazard is acceptable and the effects should be mitigated as much as reasonably possible. For long duration missions, a 1-g environment for the astronauts (preferably using a long tether and low rate of rotation) would eliminate the potentially mission-defeating effects of hypogravity. Sufficient knowledge of the effects of prolonged hypogravity and zero-g should be acquired and separately addressed to ensure crew survival in case of failure of the 1-g system and to deal with the reduced gravity on Mars. The psychological effects of isolation and confinement should be reduced by the careful selection and training of crew members. The environments provided should be carefully designed for habitability, and crew activities should be carefully planned and provisioned.


Chapter 8 - Mars Program Organization and Legal AspectsThe International Exploration of Mars Program should reflect the premise that the Project will be an adventure benefiting all of humanity, and should welcome the participation of all nations and cultures. Strategies for designing the organization and its leadership body, task forces, committees, staff selection, funding, headquarters location, operations, standards, language protocol, and venues should reflect this premise.

However, it should be recognized that, while the International Exploration of Mars Program is an inspirational and a logical objective for many space professionals, it may not have high priority for other global citizens. In these times of deep economic, environmental and social concerns, some may consider such a Mars program an unwise use of technical talent and money. Therefore, a primary task, especially during the organizational phase, should be the education of the public through the world media (print, radio, television, film, Internet) and through lectures to schools, civic groups, professional organizations, etc., on the economic, environmental, motivational, scientific, political and technological justification for exploring Mars.

The Mars Cosmic Study suggests that a mixed public/private International Mars Exploration Forum (IMEF) be initially established to provide the focus for the organizational phase. Coordinated scientific and operations planning have enabled the participants in previous international efforts to optimize the scientific return from each spacecraft and to share in the resulting measurements from all spacecraft. As an open forum, the IMEF by itself would probably not be effective in coordinating or melding national plans or developing regulatory, technology-transfer, or trade policies. While general space policies have been negotiated in the United Nations Committee on the Peaceful Uses of Outer Space, these have been slowed by national political agendas and hence those policies specific to the Mars activities might be negotiated only between the countries involved.

The IMEF's purposes would be to:¥ promote the concept of internationally cooperative space exploration;¥ motivate governments to participate in international Mars missions;¥ identify humanitarian, economic and technical benefits of Mars exploration which will

motivate governments to participate in international Mars missions;¥ educate professional groups, the public and the media on space exploration benefits;¥ identify opportunities to coordinate and, where feasible, to combine existing national Mars

exploration plans;¥ gather technical and scientific data relevant to international Mars missions;¥ make recommendations for further investigations;¥ propose technical plans which will provide a foundation for international Mars missions.

The IMEF would provide:¥ a clearinghouse of historically relevant information, data and reports on Mars exploration;¥ access to a Mars database and reports on the results of the investigations and

recommendations;¥ a report recommending the structure of a more permanent IMEF administrative organization

and the regulations and policies governing the venture;¥ a report recommending a program designed to stimulate international public support.


The robotic space exploration community has successfully shown the way by forming the International Mars Exploration Working Group (IMEWG), which is an organization containing representatives from the space agencies of the various spacefaring nations.

There are no legal or treaty barriers to international Mars exploration. Multidisciplinary problems that can be expected to develop when exploring Mars will be subject to legal provisions of treaties formulated by nations since l967 to ensure that outer space and celestial bodies are used for peaceful purposes for the benefit of all humanity. International cooperation and national responsibility are expected to maintain conditions essential for preventing harmful influences, and for the conduct of safe, orderly operations (including the prevention of planetary contamination).

The sources of space law which are relevant to Mars exploration are:¥ international law in general, including international customary law;¥ treaties, conventions and agreements formulated within and outside the UN;¥ statutes of international space organizations outside the UN, e.g., Intelsat, Inmarsat, ESA,

etc.;¥ space-related regulations of the UN specialized agencies, e.g., the International

Telecommunication Union, the World Meteorological Organization, etc.;¥ interpretations of UN resolutions, negotiating histories, expert analyses and the Vienna

Convention on the Law of Treaties; and¥ national space laws and their implementing regulations.

All space activities must comply with a set of basic policies adopted by many nations. Fundamental concepts ratified by 93 nations are in the l967 "Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies." Explorations and usage are to be performed for the benefit of all countries without discrimination; states are required to encourage and facilitate international cooperation. Whenever advances in space science and technology create new situations, provisions of the l967 Outer Space Treaty have been expanded into new treaties providing for assistance and return of astronauts and space objects, liability for damage, and registration of objects launched into outer space.

As of Oct. 20, 1995, the so-called Moon Treaty, "The Agreement Governing the Activities of States on the Moon and Other Celestial Bodies," offered by the United Nations to States for consideration in l979 and entered into force on July 11, 1984, has been ratified by only nine nations (Australia, Austria, Chile, Mexico, Morocco, Netherlands, Pakistan, Philippines, and Uruguay). France, Guatemala, India, Peru, and Romania have signed the Agreement but have not ratified it as of that time.

Some attention should be given to treaty provisions governing the relation between the Moon and Mars because legal provisions for the Moon have been drawn in such a manner that they also apply to Mars. In addition, a study should be initiated as to whether international agreements need to be made specifically for Mars because it differs so much from the Moon.

Chapter 9 - Economic and Resource ConsiderationsThis Mars Cosmic Study is not directed mainly at the aerospace engineer or the space scientist who may already be committed to space exploration. Rather it is intended for the informed citizen and the members of governing bodies of societal institutions who collectively decide on the expenditure and application of global resources. While perhaps intrigued and favorably disposed towards the advancement of knowledge about our Solar System and our galactic home, these readers will ask to


know the costs and the benefits of Mars exploration. They must compare and justify the applications of resources to space exploration versus applying those same resources to the many problems of the planet - hunger, education, disease, pollution, etc. In the end, it is an informed and objective cost/benefit study that they desire.

Foremost, it must be recognized that all space funds are spent on Earth; spent on the development and application of advanced technology. Much progress has been made in modern engineering and manufacturing in estimating the cost of products to be competitive in their respective market niches. The major problem in applying costing techniques to the estimating of Mars exploration costs is that a large part of the project remains in the R&D and "unknown" input realm. One of the main cost uncertainties has been the availability of low-cost launch vehicles to deliver the Mars vehicle (possibly in segments) to Earth orbit and to provide Mars mission logistic support.

Various human Mars mission designs have been postulated and rough, order-of-magnitude costs have been estimated. One postulated "off-the-shelf" technology plan lands a crew on Mars 19 years after the initial start, and includes a backup second mission landing, for a 30 year program. The cost in 1992 U.S. dollars was estimated at $170 billion, with an average annual cost burden of $6 billion and annual costs that vary between a minimum of $1 billion to a maximum of $13 billion. Another recent study estimates that a Mars Exploration Program consisting of three missions has a 90% probability of costing less than $110 billion. An international Mars Exploration Program can spread the costs so that no participating country need spend more than a small fraction of 1% of its GNP to participate.

Chapter 10 - Conclusions and RecommendationsThe IAA Mars Exploration Subcommittee concluded that international space exploration uniquely offers humanity access to an exciting frontier of new knowledge. Discoveries on new worlds in new environments by robotic explorers add to our knowledge of the Solar System, but they also explore the possibilities for extension of human life beyond our fragile Earth. We believe that demonstration of the reality or, conversely, of the impossibility of human habitation of other planets will have a profound influence on the ability to establish international controls for safeguarding our own planet in the 21st Century.

The planet Mars is the most natural objective for this grand exploration. Its geologic evolution has been similar to that of Earth in many ways. In its atmosphere and on its surface, we find water, carbon, and nitrogen - all required for the existence of life. Martian landforms include volcanoes and extensive channels, apparently formed by large amounts of flowing water. Today, the atmospheric pressure on Mars is only one percent that of Earth, and temperatures are seldom higher than zero degrees Celsius. It is important to discover what events led to these bleak conditions, because the answer may have implications for changes on our own planet.

Travel to Mars is technically challenging, and operations on its surface are difficult. Therefore, a comprehensive program of Martian exploration should include both robotic and human missions. A principal issue of programmatic strategy is the proper balance between automated and crewed missions. The IAA International Mars Exploration Subcommittee recommends a focused robotic precursor effort with an ongoing effort of robotic missions to assist the emplacement of the human Mars outposts and to continue human scientific exploration.

In this Mars Cosmic Study Report we present a variety of alternative approaches to mission architectures but do not recommend any particular choice. The form of the Mars exploration


program will be influenced by the nature of the organization created to implement it. In this work, we have argued strongly for an international effort. We favor an approach that begins with informal, non-official consultations and conferences under the auspices of an International Mars Exploration Forum (IMEF) to establish the technical and political issues for an international cooperative exploration program. As consensus is achieved, at first informally, the Forum evolves in stages to a formal activity, the International Commission for the Exploration of Mars (ICEM), for achieving human presence on Mars. Financially, the sharing of costs among the nations of the world in a truly global effort will make the percentage of GNP required from each country affordable.

Additional Sections in the IAA Mars Cosmic Study Report

Addendum I : Update of Mars Exploration Programs - c1995An update of Mars robotic/automated probe missions from several countries.

Addendum II : Mars Direct: A Practical Low-Cost Approach to Near-Term Piloted Mars Missions

A study investigating human expeditions to Mars by utilizing existing or near-term technology.

Addendum III : Mission Planning and Mars Architecture Trade-OffsThis review addresses the evaluation of Mars exploration architectures and discusses appropriate steps for IAA to develop a "preferred" International Mars Program.

Appendix A : A Short Guide to MarsPhysical descriptions of Mars.

Appendix B : International Exploration of Mars Survey - c1992Results of a questionnaire circulated to members of the IAA in 1992 to determine the membership's views on a proposed international mission for Mars exploration.

Appendix C : International Space Exploration InstituteDescription of a postulated space exploration organization.

Appendix D : Additional Bibliography on Exploration of Mars


Chapter 1INTRODUCTION

"On July 16, 1969, Apollo 11 was launched on its epic voyage, sent off by the largest group of media people and equipment ever assembled. The world watched as Mike Collins circled the Moon and Neil Armstrong and Buzz Aldrin landed on the Moon on July 20, 1969. This moment, shared by more of the people on Earth than had ever witnessed a single event before, brought space and space travel to every nation on Earth. No earthbound citizen of the world, watching these exciting technological developments on TV, could have foreseen, having reached the frontier of the Moon and begun its exploration, that for the next twenty-five years we would retreat to the confines of Earth's gravity." - from The Case for an International Lunar Base, IAA Lunar Base Cosmic Study, Preface, October 1990. [1]

The first Cosmic Study of the IAA, The Case for an International Lunar Base, published in 1990, outlined how an International Lunar Base might be accomplished. Some analysts, but not all, believe that the Moon might become a launching port or an oxygen re-supply station, and thus assist in humanity's journey to Mars.

It is the journey to Mars that is discussed in this Cosmic Study. Mars exploration has long been imagined by the early pioneers in astronautics. Several major conferences have explored the nature and technical possibilities of such a trip. The time has now come to lay plans for an intensified international robotic exploration of Mars, leading to an International Human Mars Exploration Project. It is the purpose of this Mars Cosmic Study to review the background for such an international Mars program and to press for action.

1.1 SPACE EXPLORATION: INTERNATIONAL BY NATURE

An orbit, the fundamental element of spacecraft motion, ignores political boundaries. Since the launch of Sputnik I as part of the International Geophysical Year, political entities have acceded to the overhead passage of spacecraft and instruments of other political entities.

A thin shell of space called low Earth orbit (LEO) contains most of the mass of objects launched by the nations of the world. Its lower bound is set by friction in the atmosphere, which shortens the orbital lifetime of satellites. Its upper bound is set by the radiation belts surrounding the Earth; long-term radiation effects are inimical to life and to spacecraft semiconductor electronics.

International space treaties contain very general provisions about protecting the space environment, but spacefaring nations have not yet been able to agree among themselves on rules for limiting spacecraft launches in order to preserve low Earth or geosynchronous orbits for future users. There are as yet no agreed upon rules on the creation of space debris, which is a major threat to future use. But there are agreements in place on dumping fuel from spent stages in orbit to prevent potential explosions, and the International Telecommunications Union (ITU) has procedures for coordinating communication satellites and for the allocation of frequencies. So while some dialogue and cooperation among nations have been initiated on some of the basic aspects of space use, a significant amount of work remains.

Scientific exploration of space tends to ignore politics. The advancement of knowledge, including the unraveling of the mysteries of the cosmos, is a human endeavor, yielding to anyone willing to invest appropriate intellectual and physical resources. Resultant discoveries enter the repository of


human understanding, benefiting all inhabitants of the planet. As space exploration has matured, the scientific community has become more international in its collaborations, and political constraints are viewed more and more as impediments to progress.

Politicization of space may be inevitable. It was originally driven by the great military confrontations beginning in the middle of the 20th century. Since space exploration depended on government investment, the most ambitious and successful achievements had political roots. The technical and scientific communities feeding on these large projects derived sustenance from the political systems and incorporated political motivations and constraints. The explosive growth of space activities, previously driven by political competition, is now beginning to react to economics.

The collapse of the Soviet Union and the sudden disappearance of Cold War imperatives has left the major political systems confused. The motivation for "conspicuous consumption" of new space adventures must rest on new grounds in the future. "Balkanization" of the World community and reemergence of ethnic boundaries is on the rise. The large space organizations are now examining their political raison d'ﾐ tre in the context of an undetermined and still-developing new World Order.

The search for redefinition naturally turns to the global nature and planetary context of space exploration. Inspiration is provided by the increasing interdependence of society and the growing public awareness of the finitude and fragility of Planet Earth. Not coincidentally, both of these powerful movements are creatures of the Space Age - consequences of the revolution in communications and of the scientific view of the Earth as a geologic and biospheric organism being modified by the cosmic environment.

Space technology is commonly accepted to be an important tool for addressing global environmental problems. The many facets of this idea are collected under the aegis of "Mission to Planet Earth." But can space capability, with its natural global perspective, also contribute to the development of international institutions for constructive action on global problems? We believe so.

Many believe that the military competition of the 20th century will give way to economic competition in the 21st. At the present time, the world's most powerful political institutions are designed to protect national capabilities in competitiveness and in technological leadership. Paradoxically, the agents of national economic competitiveness - the powerful private corporations - are becoming internationalized to take advantage of market and production efficiencies in the global economy. Thus, the power for technological advance is moving toward a transnational private sector, bypassing a regulation-bound public sector working from obsolescent assumptions. This tension will likely lead to a reformation of national political systems (e.g., into trading blocs), but the final institutional forms cannot now be predicted.

Nevertheless, this reformation will probably take place through increasing international cooperation, dialogue, and problem-solving. At first, the problems addressed will be politically neutral because the participants are, by nature, politically self-serving. Issues of this kind are already appearing on the international agenda: the environment, the conquest of disease, disaster relief, the mitigation of famine. However, these issues fall into the category of societal maintenance and repair. What about progress, growth, and hope for a better future?

The IAA position is that an international project of expanded robotic and human space exploration of Mars can provide a vision of new beginnings with fresh perspectives. Robotic spacecraft generally have acquired data according to the preprogrammed expectations of their creators. This


limitation will change with future automated spacecraft, but currently only a human space explorer can acquire knowledge through real-time, creative organization of information, while also learning to live and work in space. Space robotic and human exploration together innately expand the boundaries of human experience and enhance the possibility of embarking toward new worlds.

The cost of human exploration of Mars raises questions of cost/benefit. These are always raised regarding human exploration, but merit a set of answers specific to Mars. We may aspire to create industries that would use the Moon and its resources to deliver products and/or services useful on Earth or in cislunar space. In the case of Mars, this does not presently seem practical because Mars is so distant and the transportation energy is so large. Mars offers a rich menu of scientific exploration opportunities, but the potential cost of human Mars exploration demands more than just science return. Human exploration of Mars would teach us how to create small, self-sufficient, closed-cycle biospheres. The resulting knowledge and technology will help us protect Earth's natural biosphere.

The benefits, especially the cultural ones, are best realized by an international program. It is up to us to find a mission architecture and pace of development for a feasible international program that does not too strongly compete with Earthly needs for scarce resources. If the program uses existing aerospace facilities and personnel resources, e.g., surplus resources from declining military programs, and spreads the costs internationally, then the additional resource costs may be affordable. Further, it is better to have these resources committed to non-military programs. Finally, note that participation in such a program at an appropriate level will also help developing countries create technological and industrial infrastructures capable of enhancing worldwide sustainable economic growth. The challenge of Mars is a worthy challenge to world space development capabilities, both for developing and developed nations.

Currently, we are able to sustain a simple existence in hypogravity in near-Earth space for a few months to a year or more. We have traveled somewhat tentatively to another world, our Moon, beyond the natural radiation shield provided by the Earth's magnetosphere. These adventures are akin to the coastal excursions by the students of Prince Henry, the Navigator, who provided the expertise for the voyages of exploration to the New World after its "discovery" by Columbus.

We are confident that we can extend our capabilities to human interplanetary journeys. Such voyages of discovery can be undertaken before we fully understand the long-term response of a human being to the environment present in the crew quarters of the space habitat, but at some risk to the crew. We shall gain a significant amount of data regarding human adaptation to microgravity and isolation on long space missions such as a human mission to Mars. We shall also need to develop sufficient confidence in the long-term reliability of our mechanical and electronic systems. The ability to build the necessary large spacecraft is more certain than creating the habitat necessary to sustain humans on a voyage to Mars. The human Mars expedition has a scale of operations beyond our current experience.

Taken together, these challenges to engineering, science, medicine, and the human spirit could overtax even a mighty nation. Shared by the world, these same tasks can inspire and nourish the intellectual and spiritual growth that springs from great achievements. The difference lies in matching the scale of the problem with the scale of available resources. Great benefit lies with the successful organization of worldwide resources to meet a global goal.


Humans now possess the power and the numbers to alter the Earth on a planetary scale. Such power demands understanding of its consequences and demands responsible utilization. Space science can provide the data needed for better understanding our planet, but responsible behavior will require the creation of new and effective international institutions. We believe that the international teamwork required to explore Mars and the Solar System will sow the seeds of cooperation and trust necessary to deal with the extraordinarily difficult conflicts of enlarged human societies that lie ahead.

1.2 PAST AND FUTURE MARS EXPLORATION MISSIONS

The first U.S. Mariner spacecraft flight to Mars was launched in 1964. Since then there have been two successful U.S. flybys and three U.S. Mars orbiters that mapped the planet and helped locate the site for the two Viking Landers, which touched down in 1976. The Viking automated laboratories were completely successful and returned much scientific information about the Martian topography, soils, atmosphere, and weather (Figure 1.1). However, the experiment employed to search for Earth-like life did not result in positive detection of such life forms. The United States proposed a Mars Environmental Survey program (MESUR) [2], to establish a network of small stations on Mars. The MESUR Program has since evolved into the U.S. Pathfinder program (landing technology and surface exploration) and Mars Global Surveyor (MGS) orbiter. The European Space Agency (ESA) also proposed a Mars surface network called MARSNET [3], which has since evolved into the ESA INTERMARSNET program. (See Addendum I for mission updates.)

Japan proposes to send the Planet B probe to Mars in 1998 to study the Martian upper atmosphere and its interaction with the solar wind, and to further the development of advanced technology for future planetary missions. In its study of the structure and dynamics of the Martian upper atmosphere, the mission will focus on the structures and compositions of the Mars ionosphere and neutral atmosphere, the dynamics of the ionosphere, the effects of direct interaction with the solar wind, particle acceleration in the Martian magnetosphere, the escape of atmospheric constituents, the effects of meteorological phenomena, and optical phenomena in the atmosphere. Other scientific objectives of the Planet B mission are: determining the structure of the Martian magnetosphere, measuring the intensity of the intrinsic magnetic field, studying interaction of the solar wind with the magnetic field, measuring the dust in the Martian atmosphere, observing the dust rings along the orbits of Phobos and Deimos, and investigating dust-plasma interaction.

The Soviet Union made 17 Mars exploration attempts and, as recently as 1988, launched two probes to Phobos, one of Mars' moons (Figure 1.2). These probes did not achieve all of their mission objectives. However, additional data and understanding of Mars and its moons were obtained.

(~3 meters across) (~4 meters across)

Figure 1.1: U.S. Viking Mars Lander [4] Figure 1.2: USSR Phobos Probe [5]

There have been some recent setbacks in the exploration of Mars. The U.S. Mars Observer spacecraft was launched in September, 1992, with the intention of performing a mapping mission while orbiting Mars. Unfortunately, upon approaching Mars, contact with the spacecraft was lost. A Russian spacecraft, MARS 94, was designed to drop small stations equipped with scientific probes onto the surface of Mars. Two years later, after the arrival of the first Russian spacecraft, a


second Russian spacecraft, MARS 96, was scheduled to bring an additional set of surface measurement experiments, a rover, and Martian atmospheric balloons. The balloons were to be equipped with cameras for taking close-up pictures of the Mars surface during the balloon's trip in the Martian atmosphere. These Russian programs have been delayed by at least two years. By shipping a set of the so-called Mars Balloon Relay telemetry equipment with the U.S. Mars Observer spacecraft, French scientists had hoped to provide a redundant link to collect and transmit the balloon-measured scientific data to Earth.

Mars exploration definition studies have been or are being performed by a number of major space agencies. These studies range in scope from simple orbiters, to Rover/Sample Return Missions, to the highly technological, complex and more costly exploration of Mars by humans. Along with the intrinsic scientific return, many of the Mars missions prior to the exploration by humans can be designed and implemented as precursor missions to perform detailed imaging, mapping, monitoring and "pathfinder" activities for achieving the goals of sample return and facilitating the exploration by humans. See Addendum I for an update of the current automated probes of Mars.

1.2.1 Studies of Human Mars Exploration in the United StatesAs far as the United States approach to the problem of human exploration of Mars is concerned, many initiatives have been taken during the past several years to improve the present knowledge and to develop the enabling technology to support these future missions. Delivering humans to Mars is not a new idea, however. In 1953, W. von Braun published a comprehensive study on a manned expedition to Mars (10 spaceships with 7 crew members per craft) [6]. Twenty-five years earlier, the first serious studies regarding manned Mars missions were published by W. Hohmann and H. Oberth [7,8].

Between 1961 and 1966, NASA awarded as many as 60 contracts to aerospace companies requesting investigations of methods and technologies for human excursions to Mars. As early as 1962, and lasting for a decade, specific hardware systems were examined for a Mars-Venus flyby by humans during the 1970-1972 time frame. This project came under the name EMPIRE, an acronym for Early Manned Planetary/Interplanetary Round-Trip Expedition. In 1963, the American Astronautical Society held an International Symposium in Denver, Colorado on the Manned Exploration of Mars, attended by 800 scientists and engineers [9].

By the mid-60's, NASA studies indicated that the capabilities for a human Mars mission could be initiated utilizing Apollo-class technologies, although such a mission would be quite expensive, highly complex, and would have a long round-trip time. In 1969, a Space Task Group appointed by the President of the United States endorsed a Space Program recommended by Dr. W. von Braun, including a human Mars landing mission for 1982, which would utilize systems and experience from the Apollo lunar program [10]. This Mars mission was scaled down from the earlier concept (see Figure 1.3). The convoy consisted of only two redundant Mars spaceships with 6 crew members each; the vehicles utilized nuclear thermal propulsion. The overall plan was an integrated science and technology plan prepared by the NASA Office of Manned Space Flight (OMSF), which included a lunar colony, "a mission to planet Earth," and an eventual Mars colony.

Since the end of the Apollo program these projects have been held in abeyance. Throughout the 1970's, NASA did not have a long-term strategy into which all of these activities could organically fit. The whole U.S. space program then concentrated on the Space Shuttle development, which required almost all of the available resources. This phase lasted until the Space Shuttle Challenger


accident, which was a major setback. Recently, new projects have gotten a slightly better reception, since that incident is now more than a decade in the past.

In the late 1980's and early 1990's, enthusiasts supporting human exploration of Mars held a series of conferences under the title "The Case for Mars" at the University of Colorado. The proceedings of these conferences contain a great deal of information and a number of concepts for Earth-Mars transportation and settlement [11,12,13,14]. Stanford University's Center for International Cooperation in Space has also hosted several conferences on Mars.

In 1984, NASA Administrator James Beggs again had NASA look at human Mars missions. In 1986, NASA, in collaboration with the Los Alamos National Laboratory, published a collection of professional papers on technical topics related to human missions to Mars. These papers were produced during an agency-wide, coordinated review of the topic [15,16].


Figure 1.3: Original Concept of Space Exploration Program Proposed by W. von Braun [10]


A general reflection about possible U.S. future space activity led to a re-stated plan for the American space program and in 1986 the National Commission on Space, led by Dr. Thomas O. Paine, published its report, "Pioneering the Space Frontier" [17]. The Commission was charged to formulate a visionary agenda to lead America's civilian space enterprises into the 21st century. The Commission recommended a bold plan for the next half century in space "to lead the exploration and development of the space frontier, advancing science, technology, and enterprise, and building institutions and systems that make accessible vast new resources and support human settlements beyond Earth orbit, from the highlands of the Moon to the plains of Mars."

Later in 1986, in a response to the National Commission on Space Report, the scientist/astronaut Sally Ride was asked by the NASA Administrator, James Fletcher, to lead a NASA-wide task force to define and evaluate the potential long-range goals for the United States civilian space program, building on earlier related technical studies. The Ride task force report, "Leadership and America's Future in Space," released in August, 1987, identified and analyzed four potential initiatives: Mission to Planet Earth, Robotic Exploration of the Solar System, Outpost on the Moon, and Humans to Mars [18].

NASA's Office of Exploration was established in June, 1987 to develop and coordinate studies examining potential approaches to human exploration of the Solar System, based on the Outpost on the Moon and Humans to Mars initiatives [19,20]. For several years, a number of potential strategies were examined: Apollo-type expeditions to Mars and its moons, evolutionary plans for permanent human presence on the Moon and Mars, and establishing scientific observatories on the Moon.

In January, 1988, U.S. President Ronald Reagan announced a National Space Policy that included Solar System exploration and the Mars trip. In 1989, the 20th anniversary of Apollo 11, U.S. President George Bush announced a new vision for America in the 21st century - "... back to the Moon, back to the future. And this time, back to stay. And ... a journey into tomorrow ... a manned mission to Mars." [21]

Following this declaration, NASA released the "Report of the 90-Day Study on Human Exploration of the Moon and Mars" [22], summarizing the status of planning for this initiative, comparing possible approaches, and highlighting the main critical areas to be addressed. A specific section was dedicated to considerations of possible forms of international cooperation in such enterprises. The Administrator of NASA subsequently requested an independent assessment of NASA's ability to meet these goals. This resulted in the Augustine Report [23] which developed the concept of "go as you pay" instead of "pay as you go" as a guide to scheduling and controlled funding of large-scale, long-term space programs, i.e., a funding-paced program instead of a schedule-paced program.

In December 1989, U.S. Vice President Dan Quayle, realizing the complexity and the challenge of the Space Exploration Initiative program, requested NASA "...to cast a net widely to find the most innovative ideas in the country." These ideas were formally solicited by the Administrator of NASA, R.H. Truly, through an Outreach Program of personal letters and public announcements. A group of senior members from government offices, NASA, academia, and industry formed the Synthesis Group, chaired by Astronaut and Air Force General Thomas P. Stafford (Ret.). The Synthesis Group analyzed and synthesized the recommendations of this Outreach Program and presented the findings in the report, "America at the Threshold" [24].


The growing U.S. interest in human Mars missions is highlighted by the intensive effort put forth by U.S. sources other than NASA, as indicated by publications such as:

¥ World Space Foundation "Mission Strategy and Spacecraft Design for a Mars Base Program" [25];¥ Martin Marietta "Mars Direct: Humans to the Red Planet by 1999" [26], "A Straight Arrow Approach for the Near Term Human Exploration of Mars" [27];¥ General Dynamics "Analysis of Alternative Infrastructures for Lunar and Mars Exploration" [28], "Deimos: The Key to Colonization" [29];¥ Ball Aerospace Corporation "Mars 2000 - Why Wait?" [30];¥ Lawrence Livermore National Laboratory "The Great Exploration" [31], "A Technology Development and Demonstration Program, Mission Strategy for Human Mars Exploration" [32];¥ B.M. Cordell "Manned Mars Mission Overview" [33].

The current Administrator of NASA, Dan Goldin, in a July 15, 1995 speech at the National Academy of Sciences said,

Mars may be our next destination in space. Its secrets, and what it could tell us about our own planet are intriguing. We've learned from our robotic travels that Mars is the likeliest planet to have developed life. It also has surface conditions the most like our own. If Mars is humankind's next destination, we should launch in 2018. That's when it would take the least amount of energy to launch. We have time to plan. We have time to do it right. [34]

1.2.2 European StudiesIn 1925, Walter Hohmann published his famous book on "Planetary Trajectories" identifying the Hohmann minimum trajectory concept [7]. Prof. Karl Oberth followed with his 1929 classic "Wege zur Raumshiffahrt" [8]. In connection with Hohmann's book, Oberth's method of "Combination of Thrust Periods" was developed. These German studies laid the foundation for space mission planning.

The rapidly evolving international interest in automated and human Mars missions caused the European Space Agency to develop a capability to respond quickly and flexibly to opportunities in the field of Mars exploration. The Agency set up a Mars Exploration Study Team (MEST), whose task has been to identify possible scenarios for European participation in the exploration of Mars, taking into account such important factors as the need for major scientific return, reliance on technology currently or soon to be available, and limited budgets.

The Mars-dedicated ESA studies refer to automatic missions to Mars planned to improve the knowledge of the characteristics of the planet and to prepare for future missions by humans. The ESA Future Scientific Program Study Office published a Phase A study, KEPLER, in 1982, dedicated to developing a Mars Orbiter [35]. In 1985, an updated version of the same study was issued in the context of a European component of a Mars Dual Orbiter Mission, in collaboration with NASA.


In 1987, the ESA Long Term Program Office started a series of studies dedicated to investigating the development of a European Manned Space Infrastructure in low Earth orbit (EMSI), including its role in supporting future missions to the Moon and Mars [36,37,38,39]. In 1990, the European Space Agency identified Mars orbiter instrumentation, a Mars surface network, and a Mars rover mission as potential options in its future Mars exploration strategy [40]. In 1991, ESA published an assessment study, in consultation with NASA, which focused on the investigation of the Martian surface (MARSNET) [3]. At a national level, various European companies have produced internal studies dedicated to strategic and technological aspects related to future Mars exploration missions [41,42,43,44].

1.2.3 Studies in the Former USSR and CISThe Soviet commitment to future human space missions was clearly demonstrated by the Mir space station program. During 1980-85, the NPO Lavotchkin Design Bureau performed a series of studies dedicated to technological problems connected with human Mars missions. Major fields such as nuclear/electric propulsion [45], possible mission architectures, and vehicle configurations were examined to check the feasibility of implementing a human mission to Mars.

In the mid-1980's, the Soviets shifted the emphasis of their robotic exploration program from Venus, where they had been very successful, to Mars. A significant part of the Soviet space program was devoted to supporting the idea of a Mars mission to increase the interest in space activities, to have a long-term plan for technological enterprises, and to provide an adequate task for the heavy-lift launcher Energia or an updated version of the same. At the Planetary Society's Space Bridge Conference in July 1987, Soviet scientists and engineers stated that the purpose of their long-duration flights in the Salyut and Mir space stations was to prepare for a piloted mission to Mars. According to their plans, a detailed automated exploration of Mars has to be performed before a human flight is possible. A series of robotic missions, now to be performed by Russia, have been planned for the years 1996 and 1998. The missions will provide major advancement of the scientific study of Mars and the basic information for future human missions to the Red Planet.

As far as human missions to Mars are concerned, extensive studies and analyses of a possible Martian Mission Complex (MMC) design configuration have been performed [46,47,48,49,50,51,52]. The envisioned spaceship will consist of the following elements:

¥ Martian Orbital Module (MOM), where the crew lives and works during the major part of the mission;

¥ Martian Landing Vehicle (MLV), used to land part of the crew on the Martian surface and to return them to the MOM;

¥ Earth-Reentry Vehicle (ERV), used to return the crew to Earth.The different elements might be launched to low Earth orbit by Energia, where they will be assembled. Information concerning more current Russian Mars plans can be obtained from ANSER Corporation [53] and from Addendum I.

1.2.4 Japanese StudiesThe currently ongoing Japanese space activities are performed mainly under government leadership. Japan is pursuing both national space exploration and cooperation with other countries. Their space exploration will focus on autonomous flights (Japanese launchers, satellites and space probe development), while the cooperation with other countries will include participation in the International Space Station (ISS).


For the first years of the next century, an ambitious picture of the Japanese space scene includes the utilization of a Japanese national space station to support Lunar missions and long duration flights towards Mars and other planets (See Addendum I). The Japanese Institute of Space and Astronautical Science (ISAS) is planning to send an automated spacecraft to Mars in 1998. The objective of the mission is to study the Martian atmospheric composition and the extraction of oxygen from the atmosphere [54].

The National Space Development Agency of Japan (NASDA) is currently studying five different robotic missions to Mars [55,56]:

¥ Mars Exploration Satellite (MESA) ¥ Mars Landing Explorer (MALE)¥ Mars Moon Sample Return (MMSR) ¥ Mars Sample Return (MASER)¥ Mars Mobile Explorer (MAME)

These missions are to be launched by the H-II rocket, which is currently under development. A design concept for a human mission to Mars has been developed by Obayashi Corporation [57].

1.2.5 Canadian StudiesThe Canadian Space Agency is committed to ensuring that Canada maintains a position of excellence in the worldwide scientific exploration of space. Though the Canadian Space Agency is heavily focused on Earth satellite communications and observations and the supplying of the robotic arm manipulator for the International Space Station (ISS), a Moon-Mars working group was established in March 1990 to identify opportunities for further Canadian SEI participation [58]. The Long Term Space Plan Committee of the Canadian Space Agency has made preliminary plans for a contribution to the exploration of Mars, and is investigating contributions in scientific instruments, communications, remote sensing, and manipulators and robotics for Mars surface rover missions.

1.2.6 International Mars Mission Design Project/International Space UniversityAn International Mars Mission (IMM) conceptual design project was completed by approximately 130 graduate students from 25 different countries at the International Space University (ISU) Summer Session in Toulouse, France, 1991. This design project represents the first truly international effort to study the feasibility of an international human mission to Mars from the beginning, using an interdisciplinary, international perspective [59]. It is encouraging to note that the next generation is showing the way.


Chapter 2WHY MARS?

2.1 THE MARS IMPERATIVE

Mars, the next planet out from the Sun beyond the Earth, although cold and windswept, is the most Earth-like of all the other Solar System planets. On its surface are huge volcanoes, deep canyons, vast flood channels, and extensive sand seas (Fig. 2.1). The diameter of Mars is a little over half that of the Earth and gravity at the surface of Mars is .38 that of the Earth. The atmosphere is thin and consists mostly of carbon dioxide. The pressure at the surface is about 1/100 that at the Earth's surface, and it changes with the Martian season as part of the carbon dioxide in the atmosphere freezes out on the pole to form a polar ice cap during winter. At the equator, surface temperatures range from about -90¡C at night to +20¡C at noon, overlapping temperature conditions found on Earth. On the carbon dioxide polar caps, temperatures can drop to -120¡C (see Appendix A for further characteristics). As will be discussed in this Chapter, it is of great scientific importance, hence imperative, to explore, document, and analyze the processes that have turned Mars into a barren, inhospitable domain.

Figure 2.1: Mars [courtesy U.S. Geological Survey & NASA]

Some space scientists believe that all resource expenditures should be confined to robotic exploration of Mars, at least through the first half of the 21st Century, and that to implement a human expedition to Mars would be too costly. They believe that a human expedition would severely drain funds and "starve" research efforts in robotic space exploration, aeronautics, basic science research, and industrial research. Others feel that space exploration for science alone is too narrow a goal. They believe that human progress overall would be stimulated, and even scientific and basic research objectives attained faster, if a mix of robotic and human space exploration is performed in parallel. This latter concept is the point of view of this Chapter.

Using existing technology, humans have already landed on the Moon and could proceed to land on the surface of Mars, the moons of Mars, and on a few selected planetoids. Later technology might add the dark side surface of Mercury, a few moons of Jupiter or other outer planets, and would allow a human to orbit Venus. These seem to be the extent of possible human space exploration endeavors in the foreseeable future.

The exploration and eventual settlement of Mars by humans is a modern dream rooted in ancient wonderings about the "red planet". We find a confluence of reasons why Mars exploration now would be productive, timely, and inspirational. In this section, we describe the principal objectives of Mars exploration, the benefits we believe will result from exploration, and the timeliness and societal importance of Mars exploration. Reasons given for Mars exploration include: to gain basic scientific knowledge; as a driver to develop technologies which will improve the quality of life here on Earth; to motivate education; to locate extraterrestrial resources; for economic stimulation; and to add environmental knowledge via comparative planetology.

The possibility that humans could permanently inhabit Mars is also a central technical theme of Mars exploration. We also believe that the uplifting of the human spirit associated with the first


truly international mission of human exploration of the Solar System provides the primary rationale for the timeliness of Mars exploration.

2.2 SCIENTIFIC SIGNIFICANCE OF MARS

2.2.1 Understanding Planetary Evolution and the Origin of LifeMars has special significance for what it may reveal about the origin and evolution of Earth-like planets and the origin of life. Although Mars is compositionally similar to the Earth, it has evolved quite differently. While the Earth is a fertile, tectonically and volcanically active planet, Mars evolved into a frigid, relatively inactive and sterile body. Why did the two planets evolve so differently? Part of the answer will come from further intense studies of the Earth. But such studies should be accompanied by complementary intense studies of Mars. We are fortunate that Mars appears to preserve an almost continuous geologic record from its formation to the present day, in contrast to the Earth, where the early record is largely erased. We should, therefore, be able to reconstruct how Mars was formed and evolved, then compare that data with what we learn from the Earth and the Moon, and from this construct a general model of how the inner planets were formed.

Because of the implications for life and global change on the Earth, the climatic history of Mars is of particular interest. Liquid water cannot exist on the surface of the present-day Mars. Surface conditions are such that it will freeze or sublime. Yet ancient surface features show abundant evidence of water erosion. Orbiter pictures of the surface show numerous ancient, branching dry river valleys, seemingly cut by running water. The valleys attest to both the abundance of water during those former times, and to climatic conditions that permitted liquid water to flow across the surface. What were the climatic conditions during those times and why did the climate change? Recent studies of the SNC meteorites (Shergottite, Nakhlite, and Chassignite), thought to be igneous rocks from Mars, suggest that the total amount of water outgassed from Mars corresponds to a global Martian water depth on the order of 200 meters [60]. In more recent, controversial findings, a NASA-Stanford University research team has reported that "the chemical structure of yellowish carbonate mineral globules found in Mars meteorite ALH84001 [found in Antarctica] suggests formation some 3.6 billion years ago by bacteria-like organisms" [61]. Were the more clement climatic conditions restricted to the very early history of the planet, or did they recur periodically throughout the planet's history? These questions have profound implications for understanding global climate changes on Earth and for the possibility of early life on Mars.

Evidence from fossils indicates that life started on Earth before 3.5 billion years ago. At that time the Earth appears to have had a warm, wet climate, a CO2-N2 atmosphere, standing bodies of water, and high rates of volcanism. All these conditions may have also prevailed on Mars at that time.

Recent work in molecular biology suggests that the most primitive life forms on Earth are bacteria that live in hydrothermal environments, in volcanically-driven thermal springs. There appears to have been abundant water and abundant volcanic activity on early Mars, so we should expect abundant hydrothermal activity had been there also. But later in Mars' evolution, the planet surface dried. On Earth, the embryos of some primitive organisms such as the brine shrimp, Artemia, can survive extreme drying and anoxic (oxygenless) conditions by entering a state of metabolic and developmental dormancy [62]. Viable copepod and rotifer eggs, apparently dormant for 5 - 40 years, have been found in anoxic/hypoxic conditions in marine sediment, while viable copepod eggs found deep in the sediment of a lake have been estimated to be as old as 332 years [63]. These organisms shut down many of their metabolic processes, such as energy intensive protein synthesis, as they dry or encounter anoxic conditions. An oxygenless environment (Mars' thin atmosphere is


only ~0.13% oxygen) will prevent the oxidation of the organism's proteins, which are not being replaced. An organism may also limit its own protein replacement processes that degrade its proteins. The dry, oxygen-deprived environment of Mars is well suited for preserving organisms having this anhydrobiotic (life without water) capability.

The overlap of conditions on the two planets at the time that life began on Earth is impressive. Did life ever start on Mars? Did life start and then fail because of global climate change? Is there life on Mars today, possibly dormant? Does evidence of extinct life await us on Mars? These questions are among the highest priority science questions that future exploration of Mars must address.

2.2.2 Mars Scientific ObjectivesFew scientific questions, such as whether life ever existed on Mars, will be answered by one simple experiment. Only by addressing a range of interrelated geological, atmospheric and biological issues will the major questions ultimately be resolved [64,65,66,67]. Some of the principal research areas are the following:

Composition and internal structureThe level of our current knowledge of Mars is quite primitive. For example, we do not know the state of differentiation of Mars. What is the nature of its crust, mantle or core? We do not know the mineralogy or chemical composition of its principal rock types, and thus we do not know the planet's bulk composition. Neither do we know the amount of heat flowing from its surface, and hence we can only speculate about its previous thermal history and internal fractionations. How does it function as a dynamo? Mars is intermediate in size between the Moon and the Earth, and comparisons may allow us to determine whether these planetary bodies have been formed by common processes [4,68,69].

Geological evolution and agesThe relative chronology of Mars' major surface features is known in a general way; however, absolute ages can only be gained through the analysis of samples. This has not been accomplished, unless the SNC meteorites are demonstrated conclusively to be Martian in origin. As mentioned earlier, these SNC meteorites, found on Earth, are hypothesized to be of Martian origin based on experimental and theoretical arguments; however, the evidence is currently of a circumstantial nature. Even if the SNC meteorites prove to be Martian, other samples from known Martian locations will need to be dated before the timing of the major features can be fully determined. In turn, the chronology of surface features is related to both internal processes (volcanism, tectonism) and external processes (meteorite impacts) and can assist in understanding those processes through time.

External processes The Mars system (including Phobos and Deimos) has been bombarded throughout geological time by the same population of meteoroids and the same radiation environment encountered by the Moon and Earth. The absence of a thick Martian atmosphere means that the interactions have a different character on Mars than on either the Moon or the Earth. Whereas micrometeoroids have played a major role in the evolution of the Moon's regolith, micrometeoroids cannot penetrate the Martian atmosphere; however, larger meteoroids are not significantly slowed, and have interacted with the Martian surface to produce characteristic, but poorly understood crater forms. The atmosphere of Mars only partly protects the planet from intense radiation. Currently, the planet may not have a magnetic field, which would deflect solar wind and create an ionosphere. However, evidence that


the Moon had an early magnetic field suggests that Mars may also have had one in the past, which could modify our models of its early surface environment.

Composition and dynamics of the atmosphereThe Mars atmosphere, although much thinner than the Earth's, is a natural planetary laboratory in which to test models of atmospheric processes that are applicable to Earth [70]. Circulation patterns, thermal properties, response to changes of energy input, changes in surface albedo, and other properties of the Martian atmosphere, are common to the models that need to be built to understand and predict Earth atmosphere variability (climate and weather).

Water in Martian historyMars is of great interest because it exhibits evidence of past surface water and this hints at Mars having had different atmospheric conditions. We have much speculation, but little hard evidence, pertaining to questions such as the relative roles of water erosion, mass wasting (landslides) and wind erosion and deposition. We know little of the weathering reactions that have altered the surface composition and produced the red iron-oxide rich material that characterizes the Red Planet. The history of water is closely associated with the history of the atmosphere. If the planet had a thicker atmosphere in previous times, those volatile materials must now be somewhere else, probably in the weathered surface materials or in frozen form in the regolith. Past atmospheric composition and pressure may be studied in trapped components in meteorite impact melts and compared with other evidence of the distribution of volatiles in the present and past to form a more complete model for the evolution of the Martian atmosphere.

Existence of past or present life on MarsPerhaps the most important single question that can be asked about Mars is, "Did life ever exist there?" The past existence of life on Mars is made plausible by the evidence of water in early epochs. And, if life got a foothold on Mars in its early history, there is a possibility that life exists now, perhaps in some energy-rich environment, protected from the oxidizing effect of the current surface environment. Volcanic fumaroles or warm brines that may exist below permafrost zones are commonly cited as potential life-supporting habitats.

However, even on Earth, the search for evidence of ancient life is not easy. A strategy for resolving the issues will probably include searching for areas where it can be demonstrated that standing water existed for significant periods of time. In these areas we could examine the distribution of reduced, possibly organic carbon in sedimentary rocks, looking for telltale chemical and isotopic clues that life once existed. Finally, we could search for direct fossil evidence of life. This latter search is likely to be very difficult. The search for existing life will not be any easier.

The success of strategies for discovering evidence for past or present life on Mars depends significantly on our ability to control the contamination of Mars by terrestrial biological materials, which could confuse the interpretation of sample analyses. The fate of terrestrial organic material introduced into the Mars environment must be understood early in the exploration program.

2.2.3 Future Human HabitationMars is the only planet beyond the Earth-Moon system where permanent settlement seems remotely feasible. The extreme day-time heat of Mercury, the crushing atmospheric pressure on Venus and the frigid conditions of the outer Solar System bodies surely rule out human presence in these places in the foreseeable future. But, the natural tendency for biological species to probe and extend their


boundaries makes expansion into the Solar System appear inevitable to many. So, the challenge to achieve this can best be met through the exploration of Mars. And that challenge is one that can draw all humanity together in a common cause.

One of the primary objectives of early Mars exploration should be to determine how practical human settlement really is [71]. Although Mars is more hospitable than any planetary body other than the Earth, it is still very inhospitable. The atmosphere is too thin and of the wrong composition to sustain humans, radiation levels are high, temperatures are low and the availability of water and other resources is unknown. Early expeditions to the planet should, therefore, include among their goals an assessment of usable resources such as water, oxygen, building materials and thermal energy. Settlement will also require insulation from the local environment, including protection from radiation. Methods of providing shelter should therefore be explored. Long-term settlement may necessitate growing food on Mars. Various means of growing food on Mars must therefore be assessed. Only when we have done these exploration tasks, will we be able to determine whether the habitability of Mars by humans is a practical reality.

2.3 BENEFITS FROM MARS EXPLORATION

2.3.1 Scientific knowledgeThe scientific investigation of Mars by automated and piloted space missions will provide the opportunity to gain knowledge of the existing environment, the composition, the geologic history, the evolution, and the origin of this planet. We shall understand the nature and the ongoing processes of the Martian atmosphere while the geologic history and isotopic composition will give us access to the paleoclimate and the evolution of the atmosphere on Mars.

So far, humans have only been able to examine our own planet in detail. In order to understand the origin and evolution of our blue/green planet, we need to understand the history of all planets through the study of comparative planetology. The detailed examination of the Red Planet based on robotic exploration together with human field work will yield information about the nature and processes by which the Solar System formed. The onset of an International Mars Exploration Program will enable us to test our theories of planetary differentiation, of the origin of an intrinsic magnetic field, of planetary crusts, and the internal structure of terrestrial planets. The cratering history of Mars will help to better understand the collision history and variations in the flux of impacting bodies in the Solar System. Scientists now suspect that major events in the history of the Earth, including the formation of the Moon and the mass extinction at the end of the Cretaceous period when the dinosaurs disappeared, are due to collisional events. Therefore, the timing and the intensity of impacts is very relevant to understanding the history of the Earth and life on Earth.

The comparative study of different planetary atmospheres, such as the one on Mars, will give hints to the ongoing processes in the terrestrial atmosphere. The presence of global dust storms on Mars provides the possibility of investigating the effects of having an aerosol-laden atmosphere on the energy budget of a planetary surface. A comparable situation on Earth could occur as the consequence of a large meteoroid/asteroid impact or during a "nuclear" winter.

During the last decade, humanity has speculated that many challenging atmospheric problems on Earth are most likely to have been caused by humanity. Some scientists claim that humanity has begun to destroy the ozone layer and to influence local and global climatic changes. Surface feature evidence indicates that Mars had surface water in the past, and therefore may have experienced a dramatic change in climate during its evolutionary history. Consequently, the existing desert-like


habitat of the Martian surface may represent a worst-case example of global atmospheric changes. A better knowledge of the processes responsible for such changes will help us to understand the climate on Earth, to predict its future behavior, and how to help protect the future of human life on Earth.

A comprehensive study of the Martian surface and atmosphere are also necessary in order to verify how and whether human beings could survive on Mars. It is the prerequisite for answering the questions of whether Mars will provide access to exploitable resources and whether Mars is a reasonable and habitable candidate for human expansion.

One of the major objectives of an International Mars Exploration Program will be the search for ancient ecosystems. The possible finding of life different from that on Earth, will have an enormous impact on human self-understanding as well as the mechanisms by which life begins. The discovery of current life on Mars, even if it is limited to single-celled organisms, would have great impact on science and philosophy.

Human and robotic missions to Mars will also provide the platform for increased knowledge in other scientific disciplines not necessarily related to Mars planetology (plasma, interplanetary dust, solar activity, etc.). During the long interplanetary cruise phase out to Mars, it will be possible to perform experiments under zero-gravity conditions (material science, life science, etc.) that can never be accomplished on an orbiting space station.

It is not possible to foresee in advance exactly what the scientific return from Mars exploration will be. It is because we know so little about Mars that its scientific exploration is so interesting. Each successive automated Mars mission has shown new surprises. There is no reason to believe that future automated/human missions will be any different.

2.3.2 Mars Exploration as a Technology DriverChallenging projects, such as a Mars exploration mission, become vehicles for technology development and demonstration. Robotic missions to Mars must develop greater autonomous capability. Human missions must perform well for time durations that are significantly longer and more demanding than any previous human space flights. Accomplishing these missions can be the focus of sustained interest and investment in technological advancement, thereby providing motivation for humans to excel in technical fields.

Among the more important challenges that will drive technological advancement and that can produce benefits on Earth are:

Propulsion and PowerFor a program of repeated visits or long term occupancy of Mars settlements, more effective propulsion and power systems are required than are now available. Nuclear propulsion can reduce the trip time, and nuclear power plants are more strongly favored over solar power as the distance from the Sun increases. The development of the megawatt power systems needed for these applications may provide important advances in design and safety of small nuclear systems for application on Earth or in other space applications.

Human Health and AdaptationExtended Mars missions in isolated circumstances will require advancements in the understanding of human physiology, in prediction of health, and in provision of medical care. These will have


obvious applications to providing health services to people in remote places on Earth, to improving the effectiveness of remote diagnosis and treatment, and to improving our general understanding of the behavior of biological systems.

Life Support System Development, Resource Utilization, and Ecological TechnologiesThe future settlement of Mars depends upon the development of life systems that recycle essential resources that are in short supply on Mars (O2, H2O, etc.), otherwise those essential elements must be obtained from the Martian environment. The progress in recycling will complement the development of ecological technologies to a large extent. Research is needed on the adaptation and performance of plants in the artificial environments created on Mars, and such research is significant to plant and animal research for Earth applications.

Reliability and Extended Life of Hardware and SystemsThe reliability requirements for Mars missions and for long duration settlements are more severe than for any human space missions yet attempted. The development of equipment, particularly machinery that must actively interact with the environment (pumps, airlocks, vehicles, life support systems, etc.), will require new approaches to design, failure prediction and detection, and preventive maintenance to maximize their utility over the life of the missions. These advances are similar to advances sought by both industry and consumers in our economy.

Automation and RoboticsImprovement of existing technologies and the development of new technologies for automation and robotics are required for the successful robotic/precursor exploration of Mars. In order to preserve crew time for those tasks that uniquely require people, many routine tasks associated with a human mission to Mars might be performed by machines. Because of the great distance between Mars and Earth and the associated communications difficulties, most remote control of robotic activities on Mars may be supervised by the crew. The development of new generations of computer and machine capabilities incorporating neural networks, expert systems, and the ability to make some types of decisions, should be expected as part of the technology development for Mars exploration.

Improvements in SensorsModels of Mars indicate that a large amount of water may lie beneath the surface in the form of ground ice. There are three main forms of ice expected to be found on Mars: ice lenses; permafrost; and ice layers. Chappell has suggested a Mars subsurface radar mapper that can probe the Martian subsurface in the search for ice and geologic information [72]. This and other instruments, prodded by the intense interest in Mars exploration, will have corresponding valuable uses on Earth.

2.3.3 The Challenge and Educational Impetus of Mars ExplorationHistorically, the lack of perspective and challenge in societies often resulted in their stagnation and dissolution. An important characteristic of healthy societies has been the stimulation of innovative ideas to fulfill a challenging vision.

Education should involve not merely the acquisition of skills, but an increase in perspective and the elevation of the human spirit. The prospect of the spreading of civilization into the cosmos offers humanity the superb opportunity to achieve continuance, expansion, prosperity and knowledge. Large space programs and increased educational opportunities are linked historically. In the years following President Kennedy's announcement of the United States intention to go to the Moon, more technical Ph.D. degrees were awarded per year in the United States than at any time before or since.


A similar commitment to an ongoing, automated and human Mars Exploration program would undoubtedly stimulate education, research and development.

2.4 RETURN ON INVESTMENT IN SCIENCE AND TECHNOLOGY

Much remains to be learned about Mars. When the currently planned robotic missions have fulfilled their objectives, the level of knowledge of Mars should be similar to that of the Moon before the Apollo program. From the remotely sensed information about the surface, many ideas and questions will remain to be resolved by detailed studies. These studies can be performed only with the further collection and analysis of well-documented samples, the establishment of more sophisticated long-duration surface stations, and more detailed surface investigations.

The knowledge and capability to implement successful human missions to Mars is at a stage where the technology required can be envisioned and its performance requirements can be specified, but where significant development is still necessary. The growth of capability will be in direct proportion to the investment in technology development. In particular, the reliability of systems to perform their mission and to launch or operate on-time [73], so as to assure complex rendezvous and assembly operations, must be significantly increased. Such reliability has been demonstrated for the electronic systems associated with robotic planetary missions, but not yet for the systems needed for human flight (e.g., life support systems) or for extended operations of hundreds of days, as required for Mars surface systems. Many of these technology developments will have applications and economic benefits to the near-term problems on Earth.

2.5 ENVIRONMENTAL PROBLEMS OF MARS AND EARTH

Another emerging world concern to which Mars exploration is relevant is that of maintaining Earth's ecological environment. Mars is important for understanding Earth's environmental problems in two ways. First, Mars' environment has changed through time. Understanding the reasons for that change is relevant to understanding the past and future of Earth's climate and the manner in which humans may be changing it. Thus, a Mars program can be synergistic with the "Mission to Planet Earth" which addresses Earth environmental science. Second, the human exploration of Mars will have to solve problems of conservation, recycling of materials and utilization of local resources that have symbolic and practical importance to Earth's ecological concerns. Just as the first views of the Earth from beyond Earth's orbit stimulated worldwide concern with the environment, focusing on the preservation of human life in the harsh Martian environment can reemphasize concern with protecting and preserving Earth's environment.

2.6 UTILIZATION OF INDIGENOUS MARS RESOURCES

Mission planners intend to use Mars soil for radiation and meteoroid shielding of habitats, for building permanent structures, and for resource extraction [74]. The use of the Martian atmosphere to produce propellants, oxygen, and water is also possible [26,75]. Extensive astronautical literature exists regarding the mining of minerals and water from asteroids, extraction of helium 3 from lunar soil, and other extraterrestrial resource extraction and utilization. We do not currently know whether there are any unusually valuable deposits of minerals on Mars or its moons that will make their extraction and importation to Earth worthwhile [76]. The great distance and high cost of transportation of resources from Mars or its moons to Earth preclude this from near-term implementation. However, for this same reason, it is cost-beneficial to consider utilization of Mars surface resources for the development of a Mars base or colony. If a permanent Mars base or colony


were established, the required Earth-Mars round-trips for supply replenishment could create the opportunity to return valuable Martian minerals to Earth and lessen the costs of sustaining the base.


Chapter 3WHY INTERNATIONAL?

3.1 MAKING THE CASE

We live in a rapidly changing world, one in which technology is advancing at an unprecedented pace. The space program is both a cause and the result of this situation. The space age is quite new, yet space activity is already commonplace. Because most elementary space endeavors have already been accomplished, the very nature of many future space undertakings renders them very ambitious, technologically complex, and increasingly costly.

An International Mars Exploration Program, including human missions, is the next step in a series of what has been mostly nationalistic explorations that began in low Earth orbit, sent humans to the Moon, and sent robotic probes to the farthest reaches of the Solar System. An ambitious robotic Mars program is already underway, based on national programs, but with international contributions. Europe, Russia, Japan, and the United States all have, or intend to have, robotic Mars exploration programs. Most will feature a degree of international cooperation.

This document urges the extension of this cooperative international robotic program into a formal International Mars Exploration Program that includes human missions. Past and current studies show that human missions will involve major technological and life support problems, and will require significantly increased resources. Because of the magnitude of this undertaking, coupled with the current geopolitical world situation, humanity should seriously consider making such an extension in a primarily international, rather than primarily national, context. Indeed, the American Astronautical Society's National Committee on Space for America states,

International cooperation in space provides several important tangible and intangible benefits. It helps share the costs, risks, and benefits of space activities; it helps bind humanity into a world community; and it helps enhance world peace and prosperity. The United States, therefore, should continue to actively seek international cooperation in as many space activities as possible. [77]

The American Institute of Aeronautics and Astronautics also concluded,

In the longer term, human exploration missions beyond low Earth orbit probably will require an integrated, cooperative approach among several nations because of their magnitude and cost. [78].

There are some precedents for international ventures of the magnitude of a human and robotic Mars Exploration Program, in which complex technological, financial, and political aspects have had to be managed for a common purpose over a considerable period of time. The alliances formed during periods of international conflict, such as in World War II, and under the U.N. flag in the recent Gulf War, are possible analogies in their need to manage and coordinate vast resources in a diverse environment for the common good.

Among technological programs, projects such as the particle accelerator at CERN, ITER, Intelsat, Ariane, the formation of the European Space Agency (ESA) and the International Antarctic Base effort are relevant successful examples. In short, if the benefits of large international ventures have


been perceived as worth their undertaking, their inherent complexity did not deter their being undertaken as international activities.

This Chapter examines the rationale for making the Mars exploration program with human missions an international endeavor. We shall examine the challenges and benefits that such a "Mars Program" could bring. Some authors see both the lunar base and the International Exploration of Mars as steps in a "Global (international) Solar System Exploration Program" [79].

3.2 RATIONALE FOR AN INTERNATIONAL MARS PROGRAM

The rationale for an international context for a Mars Exploration Program is based on philosophical, technological, financial, scientific, and educational factors.

3.2.1 Philosophical RationaleThe world we live in has changed dramatically in recent years. The U.S. and the newly independent Republics of the former Soviet Union, prior Cold War adversaries, are beginning to mutually destroy their weapons. They are now more concerned with internal and world economics, and are beginning cooperative ventures for the common good. Europe has been heading toward a unified economic structure. Commercial ventures are increasingly international in both funding and scope. Communication is instantaneous and worldwide, making global industries and projects possible. Isolated, hidden despotism is becoming more difficult, and the UN is attempting to perform peacekeeping military actions, although with mixed success.

New nations and new democracies are being created at an ever-increasing rate. All have an interest in ensuring the continued evolution of the World Order into a more peaceful set of societies with a healthy international commerce.

Industrialization, which raises the standards of living of people, is at various stages throughout the world. In many developing nations the gross domestic product is woefully low and poverty and famine are all too common [71]. In the industrialized nations, problems center more around maintaining the quality of life. All nations face increasing problems in overpopulation, crime, and environment preservation. Some countries, such as those that ascribe to the Western democratic model, have a stake in helping to raise the standards of living worldwide while ensuring that the quality of life does not suffer in those nations that already have a comfortable living standard. Large technological public programs that encourage innovation and capital formation can help movement in that direction. It is within this context that we shall eventually have to justify an International Mars Exploration Program.

Regardless of their economic status, people have envisioned humans walking on other planets once the nature of the planets was known. The reaching of the Moon by men and machines was a "global" experience in the history of humanity. And so it will be with Mars. The subject of many scientific speculations and fiction writings, generations have dreamt of adventures on Mars. NASA Administrator Dan Goldin envisions, "People will see on their televisions what our rovers see on the surface of Mars. People of all ages and backgrounds all over the world will fly with a balloon across the Martian surface. They'll look out over the Martian landscape like they were in a jet liner flying over the Earth." [34].

The Viking missions' findings, that Mars is neither teeming with creatures nor has obvious signs of advanced life forms, dealt a blow to many romantic imaginings and thus to some early motivations


for Mars exploration. Quite aside from the possibility of finding future fossil evidence of life there, these same missions showed that Mars is an incredibly diverse planet with huge volcanoes, immense canyons, and former river beds, which invite humans from Earth to explore an entire new planet. Unlike the early Spanish, Portuguese, and other nations' commercially motivated exploration of the New World, such Mars exploration cannot be considered the province of any single nation on Earth, but the province of all humanity, without national imperatives.

3.2.2 Technological Synergism RationaleIt is well known that the world's resources are not equally distributed. This also holds for the distribution of technological skill and laboratory facilities. While a great overlap exists in common knowledge, there are specific technologies in which specific nations excel. If properly pooled, these skills, technologies, and expertise could become more effective than the sum of their parts. There would be synergistic benefit from access to the best available technological resources of the world. For example, the former Soviets have advanced propulsion, launch vehicle, and life support technology. Other nations might contribute excellent launch and tracking sites [80]. This would be particularly beneficial for the Mars Program, which analysis has already shown to benefit greatly from the application of advanced technologies.

All nations stand to gain from participation in the development of fundamentally new technologies. Furthermore, a Mars Program can be so designed that access to knowledge and technology spin-offs is readily available for those nations currently with lesser technological capability. Such benefits might not accrue from other than a focused, cooperative venture.

The undertaking of a Mars Program would stimulate the establishment of a global space infrastructure. In turn, such an infrastructure would act as a driver for international standards, by which the infrastructure of participating nations will be made more compatible. This would encourage commerce and facilitate further joint activity in Earth orbit and Moon Base missions.

3.2.3 Financial Cost-Sharing RationaleMost preliminary studies have shown that human Mars exploration and a Mars base will be quite expensive, even in the context of the normally high cost of space programs. The cost will surely be measured in billions of dollars per year over a period of 10 - 30 years. Although the funds required are quantitatively large, they are expected to be significantly less as a percentage of Gross World Product than either the United States or Soviet lunar programs of the 1960's were as a percentage of the Gross National Products of those countries (see Chapter 9, "Economic and Resource Considerations").

While there are a few nations and consortia that might be able to afford such expenditures as purely national activities if their entire space programs were to be focused on Mars, economic and political variables make a unilateral human Mars expedition very unlikely for the foreseeable future. Even if deemed affordable and started, it will be very difficult to maintain stable political support for a Mars Program that will probably last a decade or more. The Mars Program will be in competition with other domestic and environmental programs and will be vulnerable to unforeseen economic crises of the future.

Solutions for programs that are too expensive are to drastically reduce the scope of their activity, or to stretch them out over a longer time, or both; this reduces the yearly budget needs and thus makes them more affordable on a year-to-year basis. However, in the case of human missions to Mars, this approach will not work since even the simplest mission will be a large and complex undertaking. A


Mars mission will not be viable below a certain monetary activity level because interplanetary spaceships must be assembled and serial launch windows must be met.

While international cost sharing may actually increase the total cost of a human Mars exploration program, as explained in Section 9.3, individual costs to supporting countries will probably be reduced. Support from multiple countries also has financial benefits for the program itself. When the funds come from several countries, the multiplicity of supporters can sustain the program cash flows through a difficult economic or political period experienced by one individual supporter. Also, global markets are created for the aerospace products of each participating country [80].

3.2.4 Scientific and Educational RationaleThe Mars Program can have a major impact on education. The training of additional professors, scientists, engineers, and technologists is both necessary to provide the technical depth for a Mars Program, and will be the byproduct of its undertaking. Since education is fundamental to the rise of civilizations and the increase of standards of living, the contributions of the Mars Program to education are among the primary reasons why it should be undertaken. A high visibility exploration program, driving science and technology, will provide a major stimulus to students pursuing diverse relevant disciplines, and will encourage young students to take up such studies.

There are scientific reasons why a Mars Program should be undertaken; they are detailed in the previous section. Science, like education, is inherently international. The thirst for knowledge has never known any geopolitical boundaries, and the scientific communities of the entire Earth are already engaged. Contributions have and will continue to be made by unique experts regardless of their own or their nations' economic status, as witness the effect of Operation Paperclip that brought Wernher von Braun and his team to the U.S. after WWII [80].

The Mars Program can also be a primary impetus to the disciplines of human relations, which are often ignored in many scientific quests. The psycho-social aspects of the selection, training, and support of an international Mars crew (who are in an inaccessible location, subject to alternating stress and boredom, and isolated for long periods in confined quarters) will greatly challenge the world body of knowledge also in the behavioral sciences.

3.3 CHALLENGES TO ACHIEVING AN INTERNATIONAL MISSION

While the above may make compelling arguments that a Mars Program should be undertaken as an international endeavor, there are a number of significant challenges that must be overcome if the vision is to be accomplished. The most salient ones are discussed below.

3.3.1 Management StructureThe Mars Program may be the most ambitious single peacetime technical project ever undertaken by humanity. Quite apart from the technical challenges that must be solved, a Mars Exploration Program with many nations as participants must nonetheless be managed as an integrated whole.

The management structure for such an undertaking must be carefully thought through. If it is organized along mission elements with each contributor managing its own parts, then how is the integration managed? Is there a "World Mars Program Office"? Is there an "Integrating Entity" reporting to this Office, or does it operate through the National Space Program Offices of each country? How is authority assigned and delegated? Will National Program Offices be responsive to


the World Office? If an integration problem arises, where are the mechanisms to ensure resolution without resorting to diplomatic channels?

The Apollo lunar program's greatest contribution is said to have been the creation of management techniques for implementing large and complex technological undertakings. Yet the Apollo was a wholly U.S. program, smaller in scope, less complex, and easier to manage than an international Mars program will be. Realistically, though, the Apollo program created a bureaucracy that grew too large and was slow to change. Drastic measures were required to maintain the NASA organization as a viable entity. The management of an international Mars Program will challenge human organizational ability as nothing else has done.

There are a number of models that could be candidates for setting up the required management structure, including some adaptation of the management functional structure of the U.N., ESA, Intelsat, NATO, International Space Station (ISS), Antarctic Base, and others. These are considered in more depth in Chapter 8, "Mars Program Organization and Legal Aspects".

3.3.2 Financing ArrangementsThe financing of the Mars exploration program will be the next greatest challenge to be faced. To a great extent, the mechanism for obtaining the funds will depend on the management structure chosen. For instance, if the ESA model is followed, the funds might be solicited from the participating nations by a "World Mars Program Office", with a guarantee that (approximately) the fraction of funds underwritten by any nation would be returned to it in the form of program element contracts. If other models are followed, the financing arrangements could be entirely different.

But there are key financial questions regardless of the management mode chosen. If the money is to be raised by loans, who will make the loans? Who guarantees the loans? Are treaties required to bind the commitments? Who administers defaults? How? Is insurance required?

Consideration will also have to be given to the developing nations. The intent to make the Mars program truly global will have to be balanced against each country's ability to fund its share of the enterprise. Thus the question of some developing nations providing funds versus providing contributed value (such as headquarters sites, launch sites, tracking/communication sites, materials, or personnel) could become important. Alternatively, the industrialized nations could consider the underwriting of a portion of the developing nations' share for the sake of uniting the globe.

3.3.3 Sharing ControlThis is a sensitive issue that cuts to the heart of the viability of any international venture. To participate in any international program, each participant must give up some of the management control it normally exercises over its national programs.

It is essential to acknowledge that the control-sharing provisions of an international Mars program, at least in the development phase, must somewhat reflect the relative financial stakes of the partners. In space enterprises, as in entrepreneurial ventures, the "golden rule" might be expected to apply, "He who has the gold, makes the rules."

The original Space Station Freedom management arrangement provides an example of the complexities of control-sharing [80]. Although the basic management principle was consensus among the four partners (U.S., ESA, Japan, and Canada), the U.S., as 70% owner, retained the ability to make critical project decisions if consensus could not be reached. At the same time, it was


essential to include provisions in the management arrangements that protect "minority shareholders" against possible arbitrary action. The International Space Station (ISS) faces similar management and control challenges. Solutions may be different for the development phase than for the operational phase. The degree to which this balance between the requirements of management efficiency and junior partner protection is adequately achieved will likely spell success or failure for an International Mars Exploration Program.

3.3.4 Technology Transfer LimitationsWe live in a world that is increasingly economically competitive on a global scale. A nation's ability to compete successfully in international trade depends to a large and increasing extent on its technological "stock in trade". It is for this reason that many nations have imposed some controls on their internal organizations and individuals to limit the kinds and amounts of technologies that can be disclosed or traded, and thus transferred, to other nations.

In an international program where different nations provide different elements (vehicles, science payloads, boosters, habitats, rovers, etc.), there will be fears that vital national technologies used in such elements, particularly those which have potential military use, could be copied or otherwise transferred to other member nations during integration, inspection, testing, or repairing of the elements.

Thus, the International Mars Exploration Program may need to devise protections that will be sufficiently satisfying to the national participants that they would be willing to include their advantageous but sensitive or dual-use technologies among their contributed products. However, the program will also have to be structured such that the pooling of advanced technologies provides a net benefit by way of technology sharing to all the participants.

3.3.5 International Program Cost Increases With Respect to a National ProgramThe large cost of a Mars Program, and the necessity of spreading cost among a number of nations if it is to be affordable, is often cited as one of the most compelling reasons for internationalizing a program. However, there are some examples in which the hoped-for savings to major participants either did not materialize or were considerably smaller than anticipated.

The reasons for such shortfalls in savings have included: the increased complexity of the physical interfaces requires much greater coordination effort; increased complexity of standards to allow for different systems to function as one; increased needs for multi-lingual personnel to staff functions abroad; increased funds required for expensive foreign travel; excessively long decision times; and even contributed funds to correct overrun errors or inadequacies of partner nations.

Thus, while there are many advantages of undertaking international programs, with individual national cost savings being among the top, the management will be challenged to keep the inherent inefficiency of such undertakings from erasing the financial advantages that might otherwise accrue. Success will require delegating significant authority to a World Mars Program Office.

3.3.6 Technical InterfacesThe roles of the various contributors in an international program must be carefully defined lest the interfaces that these roles imply create an overly complex technical program that is excessively difficult to manage, and whose intended cost savings evaporate.


At the one extreme, the World Mars Program Office will have to decide whether a given nation supplies a major system element such as a launcher, landing craft, habitat, etc., or whether the nation supplies only subsystems within a major element, such as guidance, instrumentation, propulsion, etc. At the other extreme, a large nation might provide a complete functional portion of the mission, such as a habitat landed on Mars ready for occupancy by a subsequently landed human crew.

The provision of separate but independent mission portions would result in the least complex sovereignty management interfaces, but would limit the partners to those very few having such capability. Smaller nations could provide subsystems of these macro systems in various arrangements. The provision of subsystems would provide many nations an opportunity to join in the Program with a meaningful role, but would create very complex technical interfaces that would make the Program difficult, expensive, and lengthy. Thus the choice of the levels at which the technical interfaces are performed is a primary driver of the nature and feasibility of an International Mars Program.

3.3.7 Political StabilityThe International Mars Program will be virtually open-ended, with the first human landing occurring at least a decade or two after Mars Program inception. It is difficult to maintain political support for a large, expensive, and possibly controversial program within a purely national context over periods longer than the average lifetimes of political administrations. Difficulties are increased substantially in maintaining such support for an international program in a changing world subject to differing political alliances, economic partnerships and competitions, and undergoing an evolving World Order. Also, the orbital assembly schedule to meet Earth-Mars launch windows will require the ability to continue mission implementation despite a degree of political turmoil in any given country.

While the very existence of an international Mars program may make a contribution to world stability, it will far from rule-out political crises and change. The Mars program must therefore be established under a set of international treaties that are as resistant and robust as possible to the inevitable political and economic forces that will arise in an unknown, and unknowable, world political future.

3.3.8 Roles for "Non-Spacefaring" NationsIn order for the Mars program to be truly international, and to function as the intended unifying world force replacing division, subversion, and armed conflict with a common endeavor, all nations, including developing nations, should be encouraged to participate to whatever extent they are able. This may take more time and may cost more, but the IAA Mars Subcommittee believes it a worthwhile objective.

3.4 BENEFITS ACCRUE FROM MEETING THE CHALLENGES

The foregoing discussion of the challenges that must be met is not meant to discourage an International Mars Program, but rather to ensure that it is entered into with open eyes. A number of benefits would be expected to accrue from such an undertaking.

3.4.1 Reduced Financial BurdenHistory teaches that the cost of the Program's share to any one nation can be smaller, particularly if the program has strong management lines of control. This reduced financial burden to any one


nation may be extremely significant. It could spell the difference in enabling the Mars Program to proceed at all.

3.4.2 Stabilizing EffectNotwithstanding the difficulties in creating an effective International Mars Exploration Program, one of the chief benefits of its existence would be the effect on world stability. Historically, programs that involve major international commitments have proved more resistant to adverse political pressures within the undertaking nations. This international commitment has been a major factor in the very survival of some programs. The political price of pulling out from a Mars partnership will be so high for any one participant, hopefully, that the program should survive all but the most extreme national crisis. Without this international dimension, the desired program would be more vulnerable to changing domestic priorities and might prove short-lived.

3.4.3 Products, Technologies, and Spin-offsMany benefits accrue from government programs that develop new technologies. In the case of space programs, the field is rife with good examples (fault-tolerant computers, miniaturized medical equipment, and advanced avionics) and some more trivial ones (Teflon frying pans). In looking back on past national space programs, a case can usually be made that these space programs brought more long-term return to their nation's economy in the form of goods and services in all industries and sectors than was actually expended on them, with return-on-investment ratios near 7:1 [80], or higher.

While most critics agree that such new products, technologies, and so-called spin-offs are extremely beneficial, it is not possible to predict accurately the specifics that may result from the Mars investment. Unquestionably, the Mars Program will provide such benefits in large quantities. Even if the details cannot yet be predicted, these benefits will be significantly more widespread than just for those who take part in the program itself. Another factor is that the products and technological benefits may be much more relevant to some nations than to others, and may be particularly important to some developing nations. Thus, this broader measure of benefits must be kept in mind when weighing the true worth of the program compared to its cost.

3.5 TIMELINESS OF INTERNATIONAL MARS EXPLORATION

There are several reasons why the exploration of Mars is important at this point in the history of the world. These include our perception of the need of the world to have positive beneficial goals that bind nations together, thus creating capabilities to address global technological, economic and environmental problems.

3.5.1 International Mars Exploration and a Positive World OutlookThere is a pervasive attitude represented by the worldwide media that emphasizes conflict and failure, rather than creativity and success. This negative media bias contributes to a worldwide sense of stress and hopelessness. The international exploration of Mars can provide an alternative to this view, which can be understood by all people. Whereas the scientific knowledge gained by a particular mission will be understood by only a few technically trained people, a program to place humans on another planet and to follow their exploits can be appreciated by all peoples. It will be recognized as a mark of the progress of humanity, and therefore can contribute to a sense of hopefulness rather than hopelessness. It can also counteract the feeling that technology is impersonal and destructive, a view held by many of the people of the world. The worldwide appreciation of the Apollo Moon landings could be recaptured by the International Mars Program.


3.5.2 Opportunities in a Changing World Political ClimateThe world political climate is rapidly changing and provides both opportunity and motivation for Mars exploration. Many nations must deal with the problems of converting armament industries to peaceful uses, while retaining technical expertise both for future commercial benefit and for maintaining national defense capability. The wide range of systems and technologies required for Mars exploration, including electronics, power, automation, robotics, materials, propulsion, life support, and others, are among the most productive for national technological advancement. Education and training in high technology disciplines will be fostered, which will be beneficial to all participants.

With the recent changes of world politics, movements toward market economies in Eastern Europe, and emergence of regional economic structures, the world should become economically stronger. Recent developments show that the path to this stronger economic future is fraught with difficulty and may slow the day of Mars exploration.

3.5.3 The Current Focus on the Exploration of MarsMars has been a target for the Soviet (Russian) and United States space programs since the beginning of the space age, with robotic missions in current development. The European Space Agency and Japan are also working toward robotic Mars exploration missions in this decade. Mars Observer, launched in 1992, was going to undertake the systematic high resolution mapping of the planet upon arrival; however, contact with the Mars Observer was lost. The Russian Mars '94/'96 missions were to emphasize surface stations and the operation of a balloon in the atmosphere, but they have slipped two years. The Japanese Planet B mission, planned for 1998, will explore the upper atmosphere and ionosphere. The U.S. Pathfinder mission, planned for the latter years of the 1990's, will demonstrate atmospheric entry, landing, and exploration technologies, while the U.S. Mars Global Surveyor Orbiter will fly most of the original experiments flown on Mars Observer. The ESA INTERMARSNET mission, planned for the early years of the 2000's, will emplace a network of long-duration dispersed surface stations. The International Mars Exploration Group (IMEWG) exists and meets periodically to foster automated Mars exploration. Thus, a loosely coordinated interest in joint Mars robotic exploration already exists, which provides a timely basis for a larger effort that can lead ultimately to international human exploration of the planet. (See Addendum I for additional mission information).

The Russian Mir station has already accumulated information on long-duration human space flight. The missions utilizing the Spacelab on the U. S. Space Shuttle and the International Space Station (ISS) will contribute further to the experience and knowledge of international long-term space flight. What we propose here is to strongly support the national programs and to use this solid basis for the initiation of an even greater international effort that should follow.

3.6 ALTERNATIVES TO A GLOBAL INTERNATIONAL MARS PROGRAM

3.6.1 Nationalistic Mars ProgramsArguments could and will probably be made that a purely national program will be simpler, easier to manage, and will have more readily controllable interfaces. Opponents might claim that the total Mars Program cost on a national basis would be lower than otherwise, and that a purely national program might be pared down and stretched out so that its yearly cost to a nation would be just as low as its share of a more ambitious international program. The strongest arguments for a purely national program that could be made, however, are: a) the resulting benefit to that nation's


competitive position in the world and the promotion of national prestige that ensues; and b) a complex interdependent international Mars program depends on each nation honoring its commitments, something that is inherently unenforceable. These are powerful arguments in favor of a national Mars program, providing that it is feasible for one nation to undertake so vast a project.

There are, however, two countervailing arguments that mitigate the effect of nationalistic arguments. The first is that a Mars program with human missions will be so large and complex that paring it down and stretching it out to exist within national resources might not result in a viable program at all. That is, all that would ensue would be an investment in national technological capability, with no human Mars missions ultimately being successfully flown.

The second argument is that if a major nation decided to boycott an international human Mars initiative and to go it alone (if it was feasible to do so), the fallout of that action might lead to negative foreign image ramifications for that nation. As an example of this argument, consider that the only planetary exploration program involving human activities to date has been Apollo. Apollo was carried out as the United States entry in a competition between two superpowers, with the rest of the world as the audience. In a new "World Order" in which that adversarial and competitive relationship does not exist, a purely national human exploration program might not be seen by the rest of the world as a positive accomplishment, but rather as one nation flaunting its technological and financial might while others are in dire need.

3.6.2 Spacefaring NationsIf international cooperation were not chosen, the result would likely be no human Mars Program at all, or a buildup of rivalries and attitudes reminiscent of the cold war. A small group of spacefaring nations would emerge. This is not a desirable prospect.

3.7 CONCLUSIONS AND RECOMMENDATIONS

In the modern world, the gap in the standard of living between developed and developing countries has been widening, while through space communication and advanced technology world interdependence has increased. A global international Mars Exploration challenge with participation by all could help reduce this gap in the standard of living. Government and private ventures are increasingly international out of necessity, not because of artificial mandates.

While there are many benefits in undertaking an International Mars Exploration Program, there will also be many challenges that will have to be met for such a program to go forward. Nationalistic motivations will make mustering the political forces necessary to undertake the International Mars Program difficult at best. The alternative to international cooperation, to undertake purely national programs, may be more or less difficult but may not be a viable option for any one nation for both financial and foreign policy reasons. It is therefore recommended by the IAA Mars Subcommittee that the Mars Exploration Program proceed as an international initiative. This project will have political, technological, educational and other benefits for all of humanity.


Chapter 4MARS AUTOMATED MISSIONS AND PRECURSORS

4.1 INTRODUCTION

A great deal of information has already been obtained from the Mariner, Mars, Viking and Phobos spacecraft. But it is necessary to extend those findings to answer new questions in planetary science, comparative planetology and cosmology, and to allow the formulation of a detailed scientific basis for future human flights.

Robotic missions are also called upon to help solve basic problems of Earth's environment by providing ecological understanding to guide the protection of our home planet from polluting processes and thus prevent unfavorable paths in its evolution. Mars and Venus are both models of evolution of Earth-like planets that are presently unfavorable for life. All three planets are important sources of information to understand how and why they evolved differently, what constraints are crucial for the processes involved, and what the limits are for the feedback control mechanisms which preserve their individual environments.

Robotic missions should continue to improve our scientific understanding of Mars and to demonstrate new robotic technology. Scientific robotic missions should be continued even after human landing on Mars. However, robotics can also be used for testing and verification of the human spacecraft systems and other relevant hardware, for development of the strategy and scenario of the initial human mission phase, and for preliminary logistics of cargo delivery. From this point of view, they can be considered as precursors for future human flights to Mars. The robotic precursor missions will perform scientific data collection, identify potential landing sites, emplace communications and other support systems, provide a means for technology demonstration and logistics deployment, and deliver necessary infrastructure. Because the domain of human mission architectures is currently characterized by choices among a wide variety of alternatives, precursors can also help to choose the scenario that is finally implemented. Precursor data will be used to optimize the mission in terms of human safety, most favorable science return, space technology development, and cost efficiency. This view is espoused by NASA Administrator Dan Goldin, "We should be pursuing two parallel paths right now. Robotic precursor missions, and human space flight." [34]

In order to satisfy these requirements, the automated missions should not only collect the basic information in the disciplines of Martian geology, geochemistry, atmospheric sciences, climatology, and exobiology, etc., but also collect data on the performance of the engineering subsystems. In particular, geologically interesting areas that will provide significant and valuable information on the history of Mars and its physical and chemical evolution should be identified to maximize the utility of, and facilitate the construction of, surface infrastructure such as Mars habitats. Detailed studies of atmospheric science and climatology should begin now for the development of techniques to forecast Mars weather and dust storms, to clarify the weather and climate mechanisms operating on the planet, and to evaluate the short and long-term effects of the Mars environment on human surface habitats. Biological studies should investigate provocative sites for extinct or extant life, but should also address the quarantine problems for crew health security and for minimizing the contamination of the Mars environment with terrestrially exported microorganisms [81,82].

The precursor missions can be the backbone of a Mars scientific program and, in their development of robotic technologies, can complement future human exploration. The automated missions should


be considered as an important part of an integrated science, technology, and human missions development program. Their dual role is not only desirable, but essential to ensure that the effort and expense of getting to Mars yields valuable scientific results and reduces the risk and cost of human exploration. Robotic precursor missions can also establish the degree to which human presence is a requirement for a more efficient and elaborate study of Mars, and what role automation might be called upon to play in assisting human exploration. Long-term colonization and settlement of Mars will benefit from initial automatic, including robotic, scientific exploration and assessment of the potential for local resource utilization by reducing uncertainties and development costs.

4.2 GENERAL STRATEGY

Exploration of all inner planets should be pursued, emphasizing Mars and Venus as two extreme models of thermal history and climatic evolution, to take advantage of science return for developing prognostic models of unfavorable changes in Earth's ecological environment. The precursor missions' strategies and technology developments may not only support human missions to Mars but also, secondarily, concurrent missions to the Moon, the near Earth asteroids, and comets to investigate the future utilization of their resources.

Through all phases of the overall Mars precursor strategy we should extend the current level of technology development to take advantage of progress in robotic techniques and artificial intelligence. The settlements could be started at the robotic phase by having robots prepare the base site, rather than doing this only as part of a human mission.

The precursor missions should bring back basic design data and deploy some facilities on the Mars surface, allowing future astronauts to encounter a less hostile environment as they emplace housing, energy supply, transportation, communications, etc. This includes data to optimize: 1) the human mission strategy and design; 2) the propulsion system to be used and testing the corresponding flight duration and orbit selection; 3) the proportion of food and water to be supplied by onboard storage versus that supplied by a closed ecological system; and 4) the level of redundancy and reliability required for mission success. The programmatic goal should be to reduce the cost of the whole Mars Exploration Program by conducting an efficient robotic phase.

4.3 NEAR-TERM ROBOTIC AND PRECURSOR ACTIVITIES

In the '60s and '70s, six U.S. successes and two partially successful Soviet robotic space vehicles were launched toward Mars. The most productive of these were the U.S. Viking missions (consisting of two orbiters and two landers), though all missions contributed to the advancement of technology in some form. The Viking landers functioned for several years subsequent to their 1976 landings and produced a wealth of information about the surface and atmosphere of Mars [69]. These data, however, have given birth to new questions. Since the Viking missions, new experimental capabilities and space technology have become available. There have been Russian and U.S. missions to Venus, various cometary missions, and the Voyager, Phobos, and Galileo missions. Though the Phobos mission objectives were not fully realized, the two months of spacecraft operations in Mars orbit have yielded important new information on the planet and its moons. Further scientific observations will be implemented in the Mars '96 mission.

A combined mission strategy embracing the objectives of the Mars robotic and precursor missions for the present and future would include the following:


¥ Perform global mapping of the surface of Mars for the study of geology and mineralogy, physical properties and chemical evolution;

¥ Map crustal thickness, cryolithozones, and establish the interior structure and activity;¥ Perform detailed studies to establish the chronology of surface evolution;¥ Perform in situ studies of Mars rocks and soil (including studies of carbonates, sedimentary

deposits, oxides, and soil organics);¥ Investigate the structure, composition, dynamics and the history of the atmosphere and

climate, measure the minor constituents of the Martian atmosphere, determine the vertical distribution of these constituents and their variations, and monitor the atmospheric and climatic processes;

¥ Investigate the intrinsic magnetic field (if any) and the plasma processes in the Martian environment generated by the interaction of the planet with the solar wind;

¥ Provide data for location of possible landing sites and support of subsequent missions.

The NASA Mars Observer (see Figure 4.1) resumed U.S. Mars exploration 17 years after the Viking launches. This mission planned a Mars satellite in a circular, near-polar orbit at 378 km altitude. The principal objectives of this mission were to focus on the global study of the surface and atmosphere of the planet using remote sensing techniques, including high resolution imaging at several selected sites. Unfortunately, Mars Observer was lost upon approach to Mars. Failure will be a part of any Mars Program. It is important that these failures be analyzed and the resulting knowledge be used to improve future missions. This is especially important when these missions contribute to the database to be used for human expeditions.

Figure 4.1: U.S. NASA Mars Observer [courtesy of Lockheed Martin Corporation]

The Russian Mars 96/98 program (formerly Mars 94/96) pursues a more complex mission strategy. In addition to an orbiter, Mars 96 will deliver two small stations and two penetrators to the Mars surface, and will include a new seismometer for passively measuring Marsquakes [83]. These will operate autonomously for approximately one year. The next mission will also be equipped with an orbiter and (possibly) penetrators, but will additionally deliver a descent module that will deploy a balloon in the Martian atmosphere [5] and a rover on the planetary surface. Both the Mars Observer replacement and the subsequent orbiters will serve as data relays for the vehicles on the Martian surface, thus increasing the total quantity of Mars data able to be transmitted (see Figure 4.2).

Figure 4.2: Mars Satellite Network [84]

The Russian Mars 96/98 missions are considered international projects because 18 countries will contribute to their scientific payload and other hardware (see Figure 4.3). The French will contribute to the development and procurement of the balloon (the shell and inflation system), will participate in the guide rope development and testing (with the U.S.), and will help with the onboard stereo vision and navigation for the rover. In addition, the U.S. will contribute substantially to the rover testing. Russian design teams have also outlined a plan to utilize deactivated SS-18 intercontinental ballistic missiles to serve as the backbone of a cheaper, better, faster approach to Mars exploration. Use of the SS-18 is reported as consistent with the Strategic Arms Reduction


Treaty (START) signed by the United States and Russia in 1991 [85]. The Stanford University/Russian engineering study group has also urged the upgrading of the Russian Marokhod Rover with Clementine technology [86] to permit it to be launched by a Molniya booster by 1998 and to carry more scientific gear over a great range of Martian territory [87].

Figure 4.3: Russian Mars 98 Mission Balloon Station [5][courtesy of Space Research Institute and Vernadsky Inst. of Geochemistry and Analytical Chemistry, USSR Academy of Sciences; and Babakin Center, USSR GLAVKOSMOS]

The replacement Mars Observer, Mars 96, and the following missions should expand the scientific database needed to ensure the success of future, more sophisticated Mars exploration programs [5]. For example, the hundreds of high-resolution landscape images that will be returned from orbit by the balloon, by the rover, and by the ground stations will contribute to the knowledge of the Mars' surface environment and will clarify scientific and technical requirements for the subsequent robotic, precursor, and human missions. Other equally significant aspects of these missions may produce important unforeseen contributions to the understanding of Mars.

To fulfill planetary geoscience knowledge gaps, NASA has suggested that a Mars Environmental Survey project (MESUR) be developed, consisting of a number of small stations to be deployed between 1998 and 2003, to perform long-desired surface environmental measurements. This network would carry instruments generally resembling those installed on the Mars 96/98 small stations. In addition, it would provide nearly global coverage to monitor Martian interior dynamics, weather, surface conditions, variations and trends. Seismic measurements can give provisional information on the interior of Mars. The network is planned to have an operational lifetime of at least one Mars year. In addition, ESA has suggested that a MARSNET project, consisting of at least four stations distributed over the surface, be implemented in parallel with the MESUR program. As early as 1996, the MESUR mission could be sent to qualify technology for Martian entry, descent, and landing.

Until recently, the Russian blueprint for Mars exploration included a Mars Rover/Sample Return (MRSR) mission before the end of this century. This scenario included a large long-range rover that would operate for several years on the Martian surface and would collect soil samples which would then be delivered to a separately landed sample return rocket (used to transport the samples to Earth). Additionally, a mission to Phobos was planned that would take soil samples and then return them back to Earth. The simultaneous testing of common hardware for these two missions (interplanetary sample return, reentry, and deep-space network facilities) has been under consideration. Unfortunately, the current political and economic situation in Russia may cause delay or cancellation of these plans. If the situation becomes favorable again, these plans could be implemented after the year 2000.

A similar scenario for a MRSR mission has been extensively studied by NASA, but the program schedule has not yet been fully defined. The Long Term Space Plan Committee of the Canadian Space Agency [58] has made preliminary plans for a contribution to the robotic exploration of Mars. It is thought that Canada could make a contribution to a Mars rover, possibly by providing it with a robotic arm. Studies for the development of a planetary rover with Martian applications are underway in France and Italy. A Mars Orbiter (PLANET-B project) is planned to be launched by ISAS in Japan. A full program of robotic exploration of Mars and its Moons, starting with an


orbiter and followed by Phobos/Deimos sample return, Mars lander, and MRSR missions, is also being considered by Japan's NASDA.

In support of future human flights to Mars, near-term activity could contribute significantly to Mars surface mapping and to the selection of potential landing sites (accessibility, primary scientific interests, future habitability, etc.) to facilitate human exploration. The investigations of these missions and the subsequent in-depth study of the selected sites might be focused on:

A. Atmosphere -1. Atmospheric structure in the 0-100 km height range;2. Meteorology (temperature, pressure and humidity variations) [88];3. Local climate;4. Synopsis of sharp-edged variations in the strato-mesosphere;5. Atmosphere-surface interactions;6. Dust and wind hazards.

B. Surface -1. Local surface relief and land forms in the surrounding regions;2. Soil composition, chemistry and physical properties;3. Geologic patterns and history;

C. Local resources availability (including water);D. Engineering constraints (accessibility and feasibility in terms of future settlements).

The ground comparison of orbital remote sensing data with data from the first few robotic missions will serve to validate, calibrate, and allow extrapolation of results from satellite remote sensing data and will thus help mission planners identify a large number of potential 'primary' landing sites for future piloted missions.

4.4 FUTURE SCIENCE & HUMAN LANDING PRECURSORS

The currently accepted and/or planned Mars missions can be regarded as a second wave of robotic activities in a long-term program of Mars exploration and settlement, following the first wave of reconnaissance study in the 1960-1980s. The various concepts, with the possible further development of the robotic/precursor programs, have been studied by several space agencies and organizations. Some of the current mission ideas were summarized and critically evaluated in the design project International Mars Mission (IMM), the report of the 1991 International Space University (ISU) Summer Session in Toulouse, France [59]. The advancement of scientific knowledge is considered an important goal of the Mars Exploration Program. The automated probe and human exploration communities share areas of mutual interest, which include Solar System exploration emphasizing the comparative planetology approach, space physics, astronomy, geology, cosmochemistry and life sciences.

A third wave of the robotic missions would continue scientific exploration, but would also focus on preparation for the next step of activities - human flight to Mars. The operational surface network should be complemented by a new generation of robotic surface vehicles, balloons and orbiters. These should use innovative technology to increase their capabilities to carry out more complicated experiments and analyses as well as simulations of crew operations on Mars. The orbiters and balloons should serve to continue surface mapping, with progressive resolution upgrades to obtain more detail in specific areas of interest and being followed by a detailed study with mobile surface vehicles. Continuous coverage of the global processes of atmospheric dynamics and meteorology,


with an emphasis on the most insightful phenomena, should also be provided at this stage. Satellites could be placed in Mars polar, Sun-synchronous, and stationary orbits, respectively, with orbital repositioning capability in case alternate coverage is desired.

The data provided by remote sensing and collected by the surface network are to be used to select several (probably not less than three) potential landing sites. Once the sites are selected, robotic missions can be sent to evaluate these areas and to conduct the comparative analysis to finally select the best landing site for the human piloted mission.

When the decision on a human expedition to Mars is firm, a new wave of specifically targeted precursor missions might follow. Automated cargo landers will bring supplies for the upcoming crew mission. The cargo could include both exploration and construction rovers. The construction rover will work to prepare the landing site for arrival. The appropriate launch vehicles and net payload mass of these missions have to be chosen and specified in accordance with the final orbital and landing conditions and the schedule should be fitted to the whole program. For increased efficiency, the design of the Mars Cargo Lander might be similar to the design of the later Mars Crew plus Cargo Lander vehicle (Figure 4.4), with many subsystem elements being identical. Both of these designs should be based on advanced Lunar Landers if prior Lunar missions have been performed.

At the time of the cargo missions, efforts should also be undertaken to implement a permanent Earth-Mars radio link and navigation aids. This goal can be accomplished by placing special communication and navigation satellites in Mars orbit and by deploying a set of beacons on the Mars surface, being combined with the operational (both stationary and mobile) ground stations. For redundancy, communication satellites may be placed at two of the Earth-Sun Lagrange points, L4 and L5. These communication satellites can then serve as relay stations for Mars-Earth communications in case of a conjunction of Earth, Sun and Mars. Satellites can also incorporate a solar flare monitoring capability to be used for the human missions and for science purposes in general.

An important aspect of the Mars exploration program at the precursor phase is the problem of planetary protection from contamination. The contamination and quarantine protocols developed and adopted by COSPAR are to be redefined, tested, and reliably implemented during precursor missions [89], and further extended for application to cargo and habitat modules as well as to crew operations on the Mars surface. Of course, once humans land on the surface of Mars, it may be impossible to ensure the biological pristinity of Mars. (Perhaps certain areas should be preserved and be "off-limits" to exploration.) The findings from these missions will determine whether quarantine security is warranted when astronauts return to the Earth.

4.5 PRECURSOR SUPPORT OF A HUMAN MARS FLIGHT PROGRAM

The synergism between science and engineering is the key to successful long-term science return. Focus on robotic and human exploration partnerships is needed to result in the full exploitation of these capabilities. As part of the strategy of the Mars Exploration Program, it is reasonable to plan that a certain percentage of the mass/volume of planetary spacecraft be available to the engineering community for engineering experiments. Such a strategy will allow the collection of environmental data essential to the selection of Mars lander configurations (see Figure 4.4 for one proposed design), and data for the most efficient hardware design.


Figure 4.4: Mars Crew plus Cargo Lander Concept [90]

[courtesy of Boeing Defense and Space Group]

A spectrum of approaches can be taken in selecting the landing sites for human missions. Ideally, a methodical step-by-step evaluation of the many characteristics of candidate sites would be undertaken by multiple robotic missions. These missions would choose the sites most likely to be: a) scientifically rewarding; b) suitable for a future long-term base; c) rich in indigenous resources; d) possessed of a unique characteristic such as access to permafrost; e) safe for landing; or f) blessed with some combination of the above.

Sites of greatest interest can be targeted for high accuracy landings by larger landers with more sophisticated instruments and the ability to provide mobile explorations. Current programs for planetary rovers span a large variety of approaches: medium-sized wheeled vehicles with two or three-segment bodies; tracked vehicles for low bearing strength surfaces; simple and complex walkers; elastic loops doubling as footpads for mobilizing an entire lander; jeep-like vehicles with artificial intelligence for terrain image analysis and path planning; very small tethered rovers operated telerobotically for a limited distance from a lander; microrovers with autonomous behavior using onboard obstacle sensors; "insect" rovers which combine walking motions with automatic reflexes; etc. Which design features to select, such as rover range, instruments, payload mass, power, and type of data support system, will depend on the specific exploration objectives. In addition, factors such as cost, delivery method, reliability, and robustness to hazardous terrain will also be important attributes for the selection process. The Russian 98 Mars Rover design is shown in Figure 4.5, and the Mars Pathfinder microrover is shown in Figure 4.6.

Figure 4.5: Russian Mars 98 Mission Rover [5]

[courtesy of Space Research Institute and Vernadsky Inst. of Geochemistry and Analytical Chemistry, USSR Academy of Sciences; and Babakin Center, USSR GLAVKOSMOS]

Implementation of the various scenario concepts and space vehicle designs for future human flights to Mars should be complemented by incorporating relevant branches of space exploration tests into the precursor missions program. The progress in the fields of space technology and expertise specified below will have crucial impact on the selection of criteria and optimization of scenarios to facilitate the accessibility, feasibility, reliability, and cost efficiency of the human flight to Mars and the deployment of the future settlements. The principal concept is that the hardware for the future human Mars expedition should be developed in parallel with other space science/application projects. The following points are especially emphasized.

¥ The Mars human exploration issues concern the use of space stations and transportation nodes for Earth-Mars vehicle assembly and the testing of potential artificial gravity vehicles in low Earth orbit. A space station could assist as a supporting facility for on-orbit assembly by providing resources and a habitat for the assembly crew. After its mission of artificial gravity research is accomplished, an artificial gravity prototype vehicle could be used as an orbiting habitat for the assembly crew.

Figure 4.6: Mars Pathfinder (MESUR) Microrover


[courtesy of NASA National Space Science Data Center (NSSDC) and Jet Propulsion Laboratory (JPL)]

¥ The network for communication and navigation services required by Mars exploration missions should be developed incrementally. The telecommunication satellites should provide a permanent, continuously operated Mars network while radio beacons in the penetrators and the rovers can be used for autonomous navigation. A Deep Space Network dedicated primarily to human missions may be developed as well, to serve the specific requirements of these missions.

¥ Warning of solar particle hazards is also among the high priority items. Astronauts on interplanetary voyages can face serious harm and even death from the radiation of sporadic solar particle events. Shielding from these swarms of energetic protons is massive and must at least be available in the form of a small "storm shelter" aboard the spacecraft. At the present time the possibilities for predicting these events are rather limited and can provide no more than several hours warning if a flare is detected on the Sun - and even less for the most energetic particles. The communication times between the Earth and a spacecraft en route to Mars could make this warning time inadequate. In addition, the crew may be endangered by solar events not visible from the Earth. Therefore, a full range of solar and radiation monitoring equipment should be onboard the crew vehicle.

¥ The option of using a Lunar base in support of Mars missions should also be considered, and the potential advantages should be specifically identified for the mission to Mars. The Lunar base may well be a worthwhile and necessary component of an overall plan of gradually increasing human presence in space and the testing of human adaptability in an isolated environment. It may also be a useful infrastructure element in some Mars exploration scenarios.

¥ Precursor missions should also involve the testing of delivery systems for subsequent Mars missions with flight crews. This type of testing could involve the assessment of alternative propulsion schemes and the corresponding interplanetary mission opportunities such as cryogenic chemical propulsion, aerobraking technology, nuclear thermal rocket (NTR) propulsion, nuclear electric propulsion, nuclear pulse propulsion, solar thermal propulsion, solar electric propulsion, and solar sails. The appropriate interplanetary trajectories and launch opportunities are directly related to the specific propulsion alternatives that are chosen. (Note: Some experts ask whether we should postpone the human Mars mission until we develop better technology, or go now with what we have? History suggests that propulsion and other technology funds are mission driven and such systems will not be developed unless there is an approved mission requirement.) New systems must ultimately be tested in space.

¥ Several other Mars mission components and phases could also be tested with the use of precursor missions. These include: targeting for aerocapture at Mars; autonomous landing with help from Mars surface navigation systems; automatic rendezvous and docking in Mars orbit; and the test of fully configured propulsion, navigation and control systems. Thus, the precursor missions can be used to develop, validate, and demonstrate technologies required for subsequent safer cargo and human missions.

¥ Testing and implementation of Closed Ecological Life Support Systems (CELSS) will be required in the conditions of microgravity and low-gravity. These tests can be accomplished through automated missions in low-Earth orbit, on space stations, at Lunar outposts, and even


onboard precursor landers on the surface of Mars. Some CELSS concepts, such as system closure and equilibrium, will be tested here on Earth in remote environments simulating the isolation of space before committing to more expensive space tests. These Earth tests can be robotically controlled from distant locations, using satellite communications networks such as would be required at Mars. Associated quarantine methods can be tested in these same experiments to guard against foreign organisms and to prevent Earth organisms from contaminating the Martian environment.

¥ The testing of In Situ Resource Utilization (ISRU) methods during precursor missions on the surface of Mars will supply valuable proof-of-concept tests before a human crew depends on these methods. Simple experiments can be conducted, such as Sabatier and Bosch carbon dioxide reduction methods using the atmosphere of Mars. The extraction of CH4 from the Mars atmosphere as suggested by Zubrin and Baker [26] should also be tested. Other tests include the filtration of the dust from the usable atmosphere during extreme Martian dust storms, and the possible utilization of the Martian winds. While these experiments can be initially tested on Earth, remote demonstration of reliable operation in the Martian environment is desirable.

¥ Zubrin, Sridhar [26,75] and others have observed that making propellants using a Mars precursor can leverage the precursor missions themselves, allowing a large increase in sample size returned on, for example, an MRSR mission.

¥ To optimize the design of planetary EVA suits, mobility equipment, and environmental health and life support systems, it will be important to return samples of typical Martian soil for characterization in laboratories on Earth. A sample return mission could also be used for definitive verification of some of the data collected by rovers and penetrators, and to confirm the procedures and results used in the wide-ranging landing site surface tests. Otherwise, engineering systems may be designed for worst case extremes, which will exceed the actual condition requirements and could incur significant mass penalties. Because of atmospheric transport of dust and grains on Mars [91], returning samples of surface soil and suspended dust from a single landing location, not necessarily from multiple or the final landing site, may be sufficient for these purposes. However, such a mission should not be considered as the ultimate and final requirement in the list of robotic precursor missions for human flight, but rather as an important additional source of information for planetary science.

The opposite end of the spectrum of approaches to surface precursors might emphasize only the safety aspects of site certification, e.g., to avoid a field of large boulders. In this case, it is possible to envision only a simple lander with meteorological instruments and cameras for taking descent and post-landing images. In addition, the lander should have a sufficiently long lifetime so that it can serve as a landing navigation transponder for the follow-on human missions. Because a human mission is expected to include one or more human-driven rovers, it will be important for at least one precursor mission to explore the trafficability of typical Martian terrain. The lander precursor at the human site could also very beneficially be a rover so that it could reconnoiter the general area to find the safest possible touchdown site, free of large obstacles and having good load-bearing soil. The site certification rover could then station itself at a safe distance from the landing site and eventually provide imaging of the human landing. This minimal approach would be the necessary choice if the human landings were to be scheduled as early as possible.

4.6 INTERNATIONAL SPACE STATION PROGRAM


The International Space Station, a cooperative program between Canada, the European Space Agency, Japan, Russia, and the United States, will begin to be assembled in 1997, and will be completely assembled by 2002. In the 1995-1997 time frame, the Russian Mir Space Station and the United States Space Shuttle will be used by members of the International Space Station Partnership to work through technical and management problems that are important to the smooth functioning of the International Space Station.

The International Space Station will provide both baseline data and special research capabilities for the International Exploration of Mars mission, including crew habitation and health care for long duration space flights. Typical crew tours of duty will be three to six months; however, longer stays are possible. The Space Station will be used to improve medical and exercise countermeasures for long duration flights, and will be used to address issues pertaining to consumables, health maintenance, human isolation, and protocols with multicultural crews.

The International Space Station can also serve as a platform for the advanced development and test of systems required for Mars missions. The life support system, with the objective of improved closure for air and water loops, is an example. It is also planned to have a plant and animal centrifuge on the initial Station by 2001. If it were to be determined that artificial gravity was a necessity for the Earth-Mars transit and return, it is likely that the Space Station would be utilized as a test facility during the development of a human-rated artificial gravity system.

The International Space Station is the largest science/technology program ever undertaken by an international partnership, and many management and technical problems are now being faced and solved. Because many of the prospective major partners in the International Exploration of Mars are currently participating in the Space Station Program, the International Space Station should be a precursor by establishing a process and giving insight into the necessary international relationships that will be required for the international human exploration of Mars.

The possibility that the International Space Station would be utilized in an end-to-end simulation of the human exploration of Mars has been suggested. The Synthesis Group suggested a Space Station - Lunar Surface - Space Station scenario for simulating the Mars mission [24]. Such simulations may be feasible and useful; however, the question of the cost/benefits must be carefully considered in terms of the degree of fidelity of the simulation and the opportunities for collecting statistically valid data. It is possible that baseline Space Station data and ground testing on Earth or the Moon will together result in sufficient data to provide confidence in the human elements of the exploration of Mars.

4.7 MARS PRECURSOR AND ROBOTIC MISSIONS CONCLUSIONS

The Mariner, Viking, Phobos, and Mars spacecraft have provided valuable scientific data about Mars and initial baseline data to enable some realistic planning and designs for a Mars human exploration mission. Exciting near-term robotic/automated probes are planned by Russia, Japan, the United States, and Europe's ESA. These probes feature various types and degrees of international cooperation, and promise a rich harvest of additional basic scientific data, including the possibility of soil-sample return.

Many space exploration planners and space agency leaders feel that two parallel Mars exploration paths should be followed: continued automated probes and the use of some of the probes to serve as precursors for 21st century international Mars human exploration missions.


The new technologies developed for these missions can bring many benefits. Advances in Earth-based robotics, artificial intelligence, and multi-satellite systems integration are some of the most visible spin-offs.


Chapter 5OPTIONS FOR HUMAN EXPEDITIONS TO MARS

5.1 A TYPICAL MISSION SEQUENCE

Once a crew-carrying Mars ship is in Earth orbit and ready to be launched towards Mars, the sequence is straightforward: interplanetary transfer to Mars, capture in Mars orbit; direct descent to the surface using a lander; surface mission operations; ascent to Mars orbit; possible rendezvous with an orbiting ship; interplanetary transfer back to Earth; capture in Earth orbit; and finally, Earth landing. An automated mission, if it returns a sample to Earth, generally follows the same sequence. If an automated Mars surface mission does not return to Earth, the sequence ends with the Mars surface mission as it did for the Viking spacecraft.

Mars orbit operations may be eliminated by mission profiles such as is planned for Mars Pathfinder and for Mars-Direct (see Addendum II and [26]). In the case of direct profiles that include return to Earth, replenishing propellant from Mars' atmosphere is usually proposed.

While the basic mission sequence is simple enough, the complexity arises from the choice of mission profile and the choice of interplanetary propulsion system(s). There are two basic mission profiles, a slow, minimum energy transfer and a much more costly (in terms of propellant required) high energy "fast" transfer, each of which again has several variations. The selection of a mission profile hinges on the selection of a propulsion system or systems. There are currently three propulsion options potentially available to the designer: chemical rockets, nuclear thermal rockets, and electric engines using nuclear or solar power. Of these, only chemical rockets have been safely demonstrated for human missions. Aerobraking and aerocapture, after an interplanetary trip, can be used with any of these options, adding further choices.

5.2 MISSION DRIVERS

Selection of technical alternatives for missions to Mars must respond to a set of constraints and objectives collectively called "mission drivers". Deciding on the mission and system design is a compromise among conflicting requirements and desires. Engineers must make trade-offs between competing performance requirements. Failure to carefully define priorities between these requirements only leads to potentially harmful compromises and needlessly drives up costs.

Our discussion of mission drivers begins by looking at the flight mechanics or astrodynamic constraints for reaching Mars, which include interplanetary transfer as well as landing and ascending from the surface of Earth and Mars. Robotic missions, unless intended for return of Mars samples to Earth, are not constrained by the need to return.

Many factors in addition to astrodynamics influence mission architectures, as illustrated in Figure 5.1. Safety and rescue are important to the design of human missions. Risk to the crew from the natural space radiation environment may be mitigated by the combined effects of: 1) arrangement of vehicle designs to maximize benefits of inherent shielding; 2) addition of dedicated shielding; and 3) selection of low-radiation mission profiles.

Scientific objectives may dictate the Mars surface destination, affecting astrodynamics constraints, logistics requirements, and the amount and type of cargo delivery to the surface. Logistics deals with initial and subsequent cargo delivery for support of humans and mission objectives, and may


lead to requirements to deliver cargo by way of automated missions. Human factors constraints also impinge on mission duration, including design of the crew habitats, and number of people to go on the mission. Operational requirements may include prelaunch processing, launch from Earth, assembly, checkout and launch of vehicles in Earth orbit, mission control, communications architecture and processes, and abort and off-nominal operations.

Figure 5.1: Mars Mission Drivers

5.2.1 Astrodynamics Constraints

Motions of the PlanetsIt is possible to launch a spacecraft on an efficient trajectory from Earth's orbit to Mars' orbit around the Sun at any time. Astrodynamic constraints arise for a Mars visit because we wish Mars to be at that particular place in its orbit when the spacecraft arrives at the orbit.

Design of Earth-Mars trajectories is thus governed by the motions of at least two planets about the Sun. Earth, at a mean radius of 149.6 million km., completes one orbit around the Sun in one year (365+ days). Mars, at a mean radius of 240 million km., completes one orbit in 1.88 years (687 days). The more rapid motion of Earth is evident. Because of its greater speed, Earth passes Mars every 780 days (2.14 years) on average. This time interval is called a synodic period (for Earth and Mars). When Earth passes between Mars and the Sun, Mars is said to be in opposition because Mars' position in the sky as seen from Earth is opposite to that of the Sun. Earth and Mars are said to be in conjunction when Mars and Earth are aligned on different sides of the Sun. If the orbits of both the Earth and Mars were perfectly circular, this synodic period would always be the same. However, while Earth's orbit is very nearly circular, Mars' orbit is noticeably elliptical. Thus, the average period between oppositions, and the distance of closest approach at opposition, vary considerably from one opportunity to the next. These variations are reflected in mission designs.

The orbital periods of Earth and Mars have almost common factors: 15 Earth years = 7.975 Mars years (7.02 synodic periods) and 17 Earth years = 9.038 Mars years (7.96 synodic periods). Planetary alignments that present low-energy mission opportunities recur with the synodic period and thus these variations in mission profiles nearly repeat every 15 to 17 years. Close approach Mars oppositions are associated with trajectory designs of less energy, needing less time. Mission opportunities are described as "easy" or "difficult" depending on relative energy requirements.

The planet Venus is sometimes included in Mars mission designs for purposes of gravity assist, as described below. Venus, Earth and Mars have a less precise repeat pattern every six Earth years (3.19 Mars years, 9.74 Venus years, 2.8 Earth-Mars synodic periods). If a particular Venus gravity assist profile exists for a given Earth-Mars opportunity, a similar one is likely to occur six years later. Since 6 and 15 or 17 do not have common factors, Venus gravity assist profiles do not repeat from one 15-17 year cycle to the next. Generally, Venus swing-bys are not used for conjunction class missions.

General Nature of Trajectory DesignsEarth-Mars trajectory designs usually begin in a low, circular Earth orbit and terminate in an orbit at Mars, not necessarily low or circular. If return to Earth is required, a trajectory may return to low Earth orbit, or directly to the surface of the Earth (for Hohmann-like missions) by using the Earth's


atmosphere to slow down from an arrival velocity of about 12 km/sec to a safe landing. It is possible to design a trajectory to go directly from the surface of the Earth to the surface of Mars, but such trajectories pass through at least a transient orbital state. The orbital conditions are a convenient reference for describing and comparing trajectory designs whether or not the orbital state is used for mission operations.

Chemical or nuclear thermal rocket vehicles combine the velocity maneuver to escape from, or capture into, an orbit with the velocity maneuver to achieve the interplanetary velocity, because this is most efficient in terms of the amount of propellant required. Electric rockets do not have enough thrust to do this, i.e., their thrust is small compared to the gravitational acceleration of Earth or Mars. Low-thrust electric rockets must spiral slowly out of or into the planetary gravity fields and then gradually add the needed interplanetary velocity. Their thrusting time is measured in months rather than in minutes or hours.

Minimum Energy Trajectories The minimum-energy, high-thrust Earth-Mars mission profile has been known since the 1930s when it was discovered by Hohmann [7,8,92]. (It is called "conjunction" because Mars passes through astronomical conjunction soon after the mission arrives at Mars.) The trajectory from Earth to Mars is nearly tangential to the orbits of Earth and Mars; it would be exactly tangential if Earth and Mars orbits were circular and in the same plane. The return trajectory is likewise nearly tangential at both planets. This takes maximum advantage of the natural motions of the two planets, 30 km/sec average velocity for Earth and 25 km/sec for Mars. The interplanetary velocities added at Earth and Mars, respectively, are only about 1/10 of each planet's velocity. Adding velocity requirements to escape and capture into planetary orbits (500 km altitude circular at Earth and 24-hour elliptic at Mars), typical low-energy requirements are about 3700 m/sec to depart Earth and 900 m/sec to orbit Mars.

Minimum-energy transfers cannot be exactly Hohmann because Earth and Mars orbits are not coplanar. The transfer path's plane, which always contains both planets and the Sun, must nearly coincide with the plane of Earth's orbit (the ecliptic) to be low energy. This requires that actual transfer paths subtend somewhat less, or somewhat greater than a 180û arc. Those less than 180û are called Type I, those greater than 180û Type II.

Minimum-energy velocities are only slightly higher than needed to travel from Earth orbit to the Moon. From a mission velocity point of view, minimum energy Mars trips are only slightly more challenging than lunar ones. However, they take much longer (multiple of 100). The longer duration occurs because of the much greater distances being traversed, and, in the case of minimum-energy missions, the wait time at Mars for the planets to again align for a minimum-energy return trajectory.

A typical lunar trajectory covers the 380,000 km. to the Moon in three days. The distance from Earth to Mars varies from about 60 million km. to over 400 million km. The actual distance traveled by a minimum-energy trajectory from Earth to Mars is about 600 million km. The average speed is slightly less than Earth's 30 km/sec, so the time is 20 million seconds, about 230 days. (Actual Hohmann trajectory designs range from 200 to 350 days.) When the spaceship reaches Mars, the planets are not again aligned for low-energy return until 300 to 600 days later. The return trip is a mirror image of the outbound trip. Thus a minimum-energy round trip to Mars takes 900 to 1050 days in all, 2.5 to 2.9 years, about the same duration as Magellan's exploration voyage


circumnavigating the Earth. With small additions of ÆV, conjunction trips can be shortened to approximately 180 days each way, with Mars surface duration increased accordingly.

An important characteristic of minimum-energy conjunction trajectories is that times spent at Mars by successive trips do not overlap. A continuously occupied Mars base, an objective of some scenarios, is only possible with at least some crew members staying on Mars for one synodic period plus one low-energy stay time, all told about 3 years; a total time away from Earth of 4-1/2 to 5 years. Opposition trajectories (described below) lend themselves to a crew rotation operation.

"Fast" ProfilesObviously, minimum energy missions require a long time to travel round-trip to Mars. For physiological and other reasons, it may be preferred to reduce the travel duration. The shorter round-trip profile is called "opposition" because Mars passes through opposition while the mission is at Mars. However, transfer to Mars can be faster using conjunction trajectories rather than opposition. Hohmann's coplanar orbit approximation for conjunction profiles can be solved in a few minutes by slide rule, pocket calculator or abacus. A much better approximation (Keplerian paths between real Earth and Mars orbits) can be solved using the same tools in a few hours. Planetary positions for minimum energy trajectories are known from first principles; only a few trajectories need to be solved to devise a reasonable mission design.

While the method for Keplerian paths can be used for opposition profiles, as above, the best interplanetary trajectories are not known in advance and must be searched out. Solutions are only practical using digital computers to compute hundreds of trajectories. The best trajectories were not found until the 1960s. These profiles reduce trip time by using the early part of the Earth-Mars opportunity, arriving in time to catch the late part of the return opportunity. Trajectory energies are much higher than minimum. Stay time at Mars costs additional energy since it exacerbates the problem of arriving too late for the low energy part of the return window.

Figure 5.2: Opposition and Conjunction Profiles [93]

Figure 5.2 illustrates typical conjunction and opposition trajectories. Current mission designs place the shorter, more direct leg of the opposition mission before Mars' arrival so that crew time in the space environment prior to Mars surface operations is minimized. A typical opposition mission duration is 450 days. Practical stay times for this profile usually do not exceed 30 days. The mission velocity (ÆV) can be over 20 km/sec. and varies greatly between "easy" and "difficult" years. (For comparison, a ÆV of 9.5 km/sec is needed just to reach LEO.) For conjunction trajectories, transfer times can be extended in "difficult" years to keep propulsion requirements near minimum.

Deep Space Maneuvers and Venus Gravity Assists (Swing-bys)A principal reason for the high energy of a "fast" profile is the large change in the direction of the vehicle's velocity vector upon return to Earth. In some scenarios, this large velocity vector change may require as much as 3 km/sec. Realize that elliptical transfer orbits can only be tangent to Earth's near-circular orbit at either perihelion or aphelion (closest or farthest point from the Sun). For high energy missions, perihelion for the Earth return leg will be well inside Earth's orbit, assuming the return leg is the longer leg. By performing a "deep space maneuver" that slows the vehicle down near aphelion, the transfer orbit can be lowered placing aphelion closer to Earth's orbit


and thus decreasing the required ÆV near Earth. A typical deep-space maneuver requires about 2 km/sec ÆV.

A trajectory design incorporating a deep-space maneuver often places the maneuver near the orbit of Venus. If Venus happens to be nearby, the deep-space maneuver can be replaced by a Venus gravity assist (Venus swing-by), thus getting the needed ÆV for "free." The benefit of the gravity assist is so great that a Venus swing-by will almost always yield better performance, i.e., less total mission profile propellant mass, than a deep-space maneuver. However, since the location of Venus is usually less than ideal, Venus swing-by profiles usually take longer than the opposition/deep space maneuver, typically 550 days. Venus is suitably positioned for a swing-by only about half the time, that is on about half the opportunities on the outbound leg and about half the opportunities on the return leg. For a few opportunities, Venus swing-by is available on either. The Venus swing-by leg is the long one, taking up to one year, while the other leg is 150 to 200 days. If mission design practice requires the short leg to be outbound, Venus swing-by is not always available. Figure 5.3 illustrates a typical deep-space maneuver and Venus swing-by trajectories.

Figure 5.3: Venus Swing-by Profiles (adapted from [90,94])

Deep-space maneuvers do not improve mission velocity in the easiest years, but help significantly in difficult years. The maximum mission velocity is reduced to about 16 km/sec. Venus swing-bys help even more, yielding typical mission velocities in the range 11 to 14 km/sec. For Venus swing-bys, the variance in ÆV over the opportunities is mainly influenced by the position of Venus. The variance from easy to difficult years occurs mainly in trip time, from about 450 to about 600 days. Venus swing-by profiles also permit more stay time at Mars, from 60 to as much as 90 days, and are only needed on opposition trajectories. However, in all cases, the addition of a Venus swing-by to the mission profile may complicate other vehicle design issues, notably thermal control and shielding from solar flares. The savings in ÆV must be weighed against design compensations for these other issues.

Other Mission ProfilesBeginning with the opposition profile, one can trade more ÆV for less trip time down to a lower limit of about two days, where continuous acceleration of one Earth g is applied, and the round-trip mission velocity is about 3500 km/sec (500 times greater than the low-energy minimum). With foreseeable propulsion technologies, it is not practical to consider mission velocities greater than about 20 km/sec. Practical round trip times of less than a year are out of the question, and trip times less than about 16 months need special profiles. One approach has been the "split sprint". This profile pre-positions mission cargo and propellant for the return trip at Mars, on a low-energy trajectory. The crew mission "sprints" to and from Mars on an opposition trajectory, refueling in Mars orbit from the propellant depot placed there earlier.

"Cycler" and "Dash" profiles increase mission performance by using crew "taxi" and cargo "drop-off" modes that avoid ÆV for the main interplanetary vehicle for some or all encounters.

Hoffman, McAdams and Neihoff [95] described a potential cycler system known as the "escalator" or "split cycler." It uses two vehicles placed permanently on repeating Earth-Mars-Earth trajectories, as shown in Figure 5.4. One provides a short-duration Earth-Mars transfer and the


other a short-duration return. Each path has a period of about two years. Earth and Mars, as noted earlier, have successive oppositions on about 26-month centers. Since this is two months longer than two years, the cycler path line of apsides (long axis of the ellipse) must be rotated about 60 degrees every trip. This is done by gravity assist, mainly at Earth. On a few of the revolutions, gravity assist alone is not enough and some propulsion is needed.

Figure 5.4: Split Cycler System -Inbound Split Cycler Trajectory (adapted from [95])

On short-leg encounters with Earth and Mars, smaller "taxi" spacecraft deliver crew and cargo to or from a planetary orbit to the cycling spaceship. Encounter velocities at Mars are high for these trajectories [96], too high for aerobraking. The "taxi" arriving at Mars needs 2 to 5 km/sec in ÆV to slow down enough for safe aerobraking. Despite these disadvantages, the cycler concept is attractive for an evolved, routine Mars transportation system.

There are also semi-cycler trajectories. These are like a flyby, except that a taxi craft delivers crew and cargo to or from the semi-cycler spacecraft at the time of flyby. A later semi-cycler, or a semi-cycler originating at Mars, picks the crew up for return. Semi-cyclers, by stopping at Earth after a flyby at Mars (or at Mars after flyby of Earth), solve the apsidal rotation problem of the repeating cycler without high encounter velocities. Welch proposes a semi-cycler [97]. Aldrin proposes a pair of semi-cyclers, one Mars-based and one Earth-based [98]. Donahue devised a variation on the semi-cycler, called "flyby-dash", where the taxi dashes ahead of the interplanetary ship to arrive at Mars a few days earlier, enabling a short (typically 20 days) mission to be performed on a single semi-cycler trip [79]. Such hyperbolic rendezvous orbits put the crew at great risk due to the tight constraints imposed by the mission-critical rendezvous in interplanetary space. Also, it is questionable how much useful science can be performed with such sharply limited surface stays.

Low Thrust TrajectoriesSome propulsion system options, such as electric propulsion systems, deliver very low thrust, but at very high nozzle exhaust speed. Electric propulsion and solar sail systems spiral in and out of planetary gravity and don't escape from Earth until well beyond the orbit of the Moon. Once they've escaped from Earth's gravity well, low thrust systems follow an interplanetary path that, if graphed alongside the coasting path of a high-thrust vehicle with the same interplanetary trip time, looks nearly the same. The primary drawback of low thrust trajectories is the additional time needed for transfer from low Earth orbit to Mars. In many cases, the spiral-out time from Earth orbit takes as long as the transfer from the escape point to Mars. Because of Mars' lesser gravitational potential, the time it takes to spiral into low Mars orbit is about 1/3 or less than it is for Earth. It is possible to design a low-thrust Mars profile where a crew "taxi" makes a short stopover at Mars as in the cycler and dash profiles described above. Since a low-thrust system can continuously modify its path, Mars encounter and entry conditions for the taxi can be modified more easily than in the case of high-thrust propulsion.

A very important distinction between low and high thrust trajectories is that a high-thrust trajectory is always on a planetary encounter path (except prior to a deep-space maneuver) while the low-thrust trajectory is not. High-thrust trajectories, with a suitably designed trajectory, can use gravity assist at planetary encounter to effect an abort and return home. Low-thrust trajectories do not


require special trajectory design just to enable abort. Abort from a low-thrust trajectory requires propulsion power, usually about the same ÆV as for a nominal mission; gravity assist abort from a low-thrust trajectory is not available. The problem is that if you lose all propulsion, you are lost; you can usually lose about half power safely. The general problem of abort from various trajectories has not been adequately addressed in the literature.

Sponaugle, et al. [99], describe elimination of spiral time from low-thrust interplanetary trajectories by staging at an Earth-Moon libration point, typically L2. At Mars, a Mars-Sun libration point is used. Taxi vehicles using cryogenic propulsion and aerobraking can provide transportation between low Earth orbit and L2, and between Mars surface and the low-thrust vehicle staging point. Gravity-assisted arrivals at Mars, in which the surface mission is performed in the 30 to 60 days between an initial swing-by encounter and later capture in a high Mars orbit, have been investigated. These schemes make low-thrust systems competitive with high-thrust systems for crew transport trip time.

Mars Capture Orbits Most mission designs use some Mars capture orbit. The present discussion applies mainly to high-thrust interplanetary systems since a low-thrust system can easily modify its capture orbit, and a low-thrust interplanetary trajectory is insensitive to capture orbit selection. Capture orbit selection is driven by the need to provide minimum-energy conditions for transfer from interplanetary approach to the capture orbit and from the capture orbit to interplanetary departure. Mission designers must also consider access to surface sites of interest as well as suitable conditions for descent to the surface and ascent back to the capture orbit. (No landing at all if the weather is bad.)

A low altitude circular capture orbit is the most flexible and is the easiest to analyze. An "in-plane" orbit can always be found that includes the approach and departure velocity vectors so that plane change is not required either on arrival or departure (this minimizes ÆV). The Mars descent system can initiate descent from anywhere in the orbit. In-plane orbits usually have an inclination of 30 to 50 degrees, giving reasonable but not total Mars surface access. Orbit periods are short enough to make any longitude on Mars accessible within a day or two. Ascent to the orbit can be direct or nearly direct.

Highly elliptic orbits with a low-altitude periapsis, as was used on Mariner 9 and Viking, are more complex to analyze and use, especially for round trip missions. However, these orbits save as much as 2 km/sec in ÆV for the interplanetary vehicle; but landing from such orbits and reascent may be more difficult. This is another mission trade study area. ÆV is the coin of the realm for mission designers and this is a major savings in ÆV. In-plane orbits can always be found, but there is an added complexity, since to achieve the savings the orbit must be entered and left near its periapsis. If the mission stays at Mars about 100 days or more, orbit perturbations due to the oblateness of Mars (J2 = 0.00196) can be used to modify the orbit for departure by adjusting the orbit period to obtain the right combination of nodal regression and periapsis advance. The lander entry into the atmosphere must be near periapsis. A lander lift-to-drag ratio above 1.5, attainable with either a lifting body or biconic shape, enables landing anywhere on the planet using aerodynamic lift for maneuver. A phasing orbit is used for ascent. If landing near the poles is desired, the elliptic orbit is preferred because the plane change needed to correct inclination from near-polar to that of the capture orbit can be done at apoapsis, where the velocity is low.

One option sometimes proposed is using one of the Martian moons, Phobos, as a staging base for surface exploration. However, orbital mechanics dictates the ease at which a Phobos landing can be


obtained as compared to simple capture of the spacecraft into Martian orbit. With Phobos' inclination at ~1¡, large (propellant expensive) plane changes (ÆV) are needed to reach Phobos on many arrival dates. Furthermore, there is a large variability in arrival geometry, depending on launch date, further complicating the mission design for a Phobos mission. The small size and very low gravity of Phobos requires more of a docking rendezvous between it and the spacecraft than a landing. And, once at Phobos, surface missions are limited to Mars' equatorial region unless another plane change is performed [100].

5.2.2 Abort/Rescue Considerations.Any human activity has its dangers, but the risk of fatality while engaging in space flight has historically been about 3%. The U.S. Mercury, Gemini and Apollo flights had no in-flight fatalities; and the U.S. Space Shuttle has had one failure in more than 50 flights, less than a 2% fatality risk. The Soviets/Russians have done extremely well in successful human flights in recent years. In comparison, driving your car or flying somewhere by commercial air carries a risk closer to 0.0005%. A risk of 3% is sometimes mentioned as an upper acceptable value for space mission planning purposes. Any next-generation system for transporting people to Earth orbit will probably be designed to a risk requirement of less than 1%. The 3% value is a reasonable target for Mars missions. Achieving 3% requires that abort and rescue play a prominent role in mission and system design, but these are only part of a general risk reduction analysis. Some analysts believe that achieving 3% may not require backup and rescue modes, but provision should still be included.

Thorough investigations of Mars mission risks have not yet been performed. Preliminary analyses indicate that acceptable risks for Mars mission profiles can be achieved if abort options are designed into the mission for all phases except those for which it is essentially impossible to do so (e.g., ascent from the Martian surface back to the capture orbit). The abort option requirement eliminates some mission profiles from consideration, especially those involving very fast and therefore energetic trajectories. Maintaining an option for unpowered flyby abort return to Earth at Mars encounter, for example, places limits on Earth-Mars trajectories. Of course, Earth is not the only abort option. Many abort mission concepts exist where in-flight failures can be overcome by landing at Mars, in those cases where surface conditions allow a safe landing and if subsequent Earth-return infrastructure is in place. Highly energetic trajectories usually do not have unpowered abort options, and the launch window at Earth is generally shorter if confined to trajectories with unpowered aborts. If a hyperbolic rendezvous is not successfully completed, the crew and/or supplies will not be transferred and this may mean crew loss and/or mission failure.

As noted above, low-thrust trajectories do not, in general, have unpowered abort options. However, the low-thrust systems envisioned usually involve redundancy of the propulsion power supply and thrusters. Nuclear thermal rockets degrade gracefully and can be controlled, according to proponents. Thus an abort return on reduced thrust missions is generally possible with modest increases in total trip time. Table 5.1 presents a typical menu of abort options for a high-thrust Mars mission. With exceptions as noted, these abort options do not create high initial mass penalties. The exceptions are often not included in a mission design; quantitative analyses of risks are needed to determine whether abort options are really necessary.

Table 5.1: Typical High-Thrust Abort Options by Mission Phase

Multi-Burn Earth Departure Intermediate orbits are elliptic; return to Earth from apogee.Early Part of Coast to Mars Quick return to Earth usually possible for about the first 30


days.Later Part of Coast to Mars Mars swing-by (gravity assist) return to Earth via

opposition-like trajectory. *Mars Orbit Early: Return to Earth on opposition-like trajectory.

Later: Wait for normal Earth return opportunity. **Mars Descent Separate ascent stage and crew module; abort to Mars

orbit.Surface Operations Use Mars ascent stage; if it is inoperable there is no abort

unless another lander/ascent vehicle is available for rescue or unless the surface base can be inhabited until a rescue

arrives on the next Mars opportunity.Mars Ascent No practical abort scheme.

Trans-Earth Injection No practical abort if main propulsion fails.Coast to Earth Continue normal return to Earth.

* On some opportunities, propulsion is required at Mars to reach the Earth return trajectory; if a Venus swing-by is not available, a deep-space burn may be required.

** Providing the ÆV for return to Earth on an opposition-like trajectory causes a severe initial mass penalty for some Mars opportunities. As soon as a viable long-term surface base is established, abort to Mars surface is likely to be the preferable option.

5.2.3 Mission ObjectivesMission objectives affect mission design and system selection through requirements such as crew size, scientific and operations cargo characteristics, stay time at Mars, surface site access, and the potential desire for continuous presence at Mars (e.g., a permanent Mars base).

Analysis of skill mix needs indicates a minimum crew number of five to eight for a Mars mission. This analysis assumes that each crew member could be trained for two primary skills and one secondary, and that a scientific discipline would be a primary skill for no more than two or three of the crew. The NASA "90-Day Study" [22] assumed a crew of four, while later studies assumed five crew members. The U.S. Synthesis Group activity recommended six crew members [24], while the study by the International Space University proposed eight crew members [59]. Parametric studies funded by NASA have considered larger crews, up to 32, but such large numbers lead to overly ambitious interplanetary ships. (The original von Braun papers [6] proposed a crew of 70!)

Greater demands for primary science skills as well as needs for international representation could lead to a greater number of crew than the minimum four to eight. The size and cost of a mission are directly driven by this number. For numbers greater than eight to ten, a convoy of two or more ships could prove an attractive mission design option by providing a redundant habitat for safety and limiting the size of ships to a more manageable scale.

Cost considerations have tended to drive the number of crew in recent studies to the lower limits of what is believed by the study authors to be a safe and reasonable crew complement. There is much uncertainty as to what this minimum number really is. A high priority for human factors studies is to better establish minimum requirements for Mars mission crew size and the habitation amenities necessary for the long duration of these missions.

Operational cargo includes those mission elements necessary for crew sustenance and operations on Mars. Cargo requirements increase with crew size and stay time. For a 30 to 60-day stay on Mars


for a crew of six, operations and science cargo has been estimated at between 50 t and 100 t*; 150 t will enable stay time to increase to conjunction mission durations of 500 to 600 days. A value for permanent occupancy has not been published, but is estimated to be at least 200 t. The added mass beyond conjunction stay provides for a food growth system. Food growth rather than resupply from Earth is indicated as the minimum-cost solution for mission durations of more than about two years. Food growth would only be practical in a continuous occupancy scenario since otherwise the agricultural system would have to be shut down at the end of each crew visit and restarted at the next visit.

Using current estimates, several tonnes of science cargo would be needed in the base vicinity. Such cargo would include sample gathering and aeronomy equipment, rovers (at least one unpressurized and in most cases at least one pressurized), and other equipment in a small laboratory attached to the crew habitat. The capabilities of rovers are addressed in Chapter 4 of this report. The range of pressurized rovers could be up to hundreds of kilometers. Even this range is small compared to the extent of scientifically fruitful sites on Mars. Studies in the literature have not adequately addressed how the surface site access needed for true exploration of Mars can be achieved [101]. Consequently, mission scenarios and cargo manifests for the long-duration class Mars surface mission should be regarded as preliminary and subject to major changes.

The major influence of a requirement for continuous occupancy is that, as mentioned above, a series of conjunction-class, long-duration Mars missions cannot support continuous occupancy unless people commit to stay for about 1-1/2 synodic periods (over 3 years). Most of the opposition mission profiles, and some of the cyclers, can be operated in a crew rotation/resupply mode in which the 30 to 60 day stay at Mars is the overlap period for arriving and departing crews. Crew stay time on Mars is then one full synodic period (about 26 months).

5.2.4 Long-Duration Hazards"Long-duration hazards" include the space radiation environment, several effects of microgravity, and sociological/psychological risks of extended confinement and hazardous operations. All of these are discussed in Chapter 7, "Human Factors and Physiological Aspects". Their influence on mission and system design includes: 1) shielding, system design, and operations approaches to minimize radiation risk; 2) possible requirement for an artificial-g interplanetary ship (i.e., some rotating portion); 3) incorporation of human factors needs in habitat design (affects mass and cost); and 4) selection/tailoring of mission profiles to suit duration limits. Minimum in-space transit time, for example, is obtained by a "fast conjunction" profile for any given technology availability. This is obtained by accepting long stay times on Mars. Minimum total mission duration is obtained with opposition-class missions, but nearly all the mission duration time of 1 to 1-1/2 years occurs in space rather than on Mars. Significant exploration requires the longer stay times of the conjunction profile (or continuous presence) in any case. The debate mainly concerns whether the program plan should include enough precursor robotic placement of cargo on Mars to support a longer stay on the first mission, versus a first mission with a short stay on Mars followed by longer stays later.

5.2.5 Operational ConsiderationsMany of the important operational considerations are included under "safety and abort". The other significant operational considerations arise from the necessity for a high degree of autonomy on the mission. A Mars ship departing Earth will, in two or three days, reach a distance where the communications time delays become too great for ordinary conversation, and will spend most of the mission at distances causing 10 minutes to 40 minutes round trip communications time delays. The

* t = tonne = 103 kg


nature of communications will be similar to sending faxes back and forth. Accordingly, all short-term decisions must be taken by the crew because of communications delays. Longer term decisions will no doubt involve mission control, but it will be difficult for mission control and the mission crew to "talk things over" as they did in formulating the successful Intelsat rescue plan on a recent U.S. Space Shuttle mission, or even as was done during the heroic Apollo 13 rescue.

Autonomy is also necessary because it will not be possible to design Mars ships with enough redundancy to operate during 11/2 to 3-year missions without repairs. Some onboard repairs, such as replacement of control moment gyro sets, were carried out on the Skylab mission. The Russians conducted extensive in-flight repairs on Salyut 7 and on Mir. The Mars ship will be far more complex than any of these, and the communications delays will prevent the ground from talking the crew through repairs. Consequently, end-to-end maintenance capability must be provided onboard: 1) built-in test and diagnostics to detect and isolate failures down to the "black box"/valve/electronics card level; 2) automatic compensation for failures so that maintenance operations may be conveniently and efficiently scheduled; 3) automatic determination and presentation of the necessary maintenance procedures to the crew; and 4) assistance to the crew to verify successful repairs.

Only very preliminary failure rate, spares, and stockout analyses have been conducted. These indicate that a Mars ship design must: 1) rely on a high degree of commonality at the parts level to minimize spares type inventory; 2) carry cold spares; 3) provide for replacement at the "black box"/valve/electronics card level, as noted above; 4) enable repairs to be made using few person-hours; and 5) provide shop facilities and materials stock to permit improvising repairs as a backup to "remove and replace" procedures. In any case, these operational requirements for designed-in reliability and ease of in-flight maintenance are unprecedented using current aerospace technology. This in itself is an important area of technological development that dare not be overlooked but which offers awesome potential for spin-offs to other parts of the economy.

5.3 SYSTEM OPTIONS

A critical system decision for a human mission is whether artificial gravity should be employed. Artificial gravity may be achieved through: a) the spinning of two modules attached to each other by a long cable tether or by shorter rigid tethers; b) the spinning of an integrated structure [102]; or c) the use of an internal centrifuge. This alternative would complicate the operating sequence and spacecraft control when ÆV is to be applied, would require additional energy for spin-up and spin-down, and would restrict aerobraking configurations. Research continues on artificial gravity concepts. The physiological aspects of the human crew are covered in more detail in Chapter 7, "Human Factors and Physiological Aspects".

5.3.1 PayloadsThe system options for Mars missions have a common factor, the payload. This consists of an interplanetary crew habitat, one or more Mars lander/ascent vehicles, and usually an Earth return entry module for the crew. For a crew of six, typical masses are 60 t for the habitat, 80 t for each lander, and 8 t for the entry module. Thus, a minimum Mars mission delivers 148 t to Mars orbit and uses 68 t on the Earth return leg. A Mars lander this size, operating as a robotic cargo vehicle, has cargo delivery capability to Mars surface of 40 t to 50 t. Thus, surface cargo delivery for typical scenarios requires one to four landers besides the crew lander. In most mission scenarios, the cargo landers are sent ahead on a robotic mission rather than with the crew ship. The mass of the habitat depends on crew size and to a lesser degree on mission duration.


5.3.2 Propulsion Options and Typical System Concepts The different system options for Mars missions are best identified based on interplanetary propulsion options. As noted above, these are: 1) conventional rocket engines burning cryogenic propellants (liquid oxygen and liquid hydrogen); 2) nuclear thermal propulsion; 3) nuclear or solar electric propulsion; and 4) aerobraking used in conjunction with some of the rocket propulsion systems. The higher performance systems provide greater mission design flexibility, but will take longer and cost more to develop initially. Rocket engine efficiencies are generally compared using a metric called specific impulse (Isp). Isp is derived by dividing the engine exhaust velocity by the Earth standard acceleration of gravity (9.80665 m/sec2). 5.3.2.1 Cryogenic PropulsionCryogenic rocket engines produce an effective exhaust velocity of about 4.6 km/sec (vacuum Isp of about 440 to 470 seconds). Since the minimum ÆV for a Mars mission is about 6 km/sec, the rocket equation determines the expected initial mass for a cryogenically propelled Mars ship to be about 6 times the payload to be delivered. For minimum-energy missions with a single lander, cryogenic propulsion leads to initial masses in the range 600 t to 800 t. As mission profiles are pushed to higher ÆVs to achieve shorter trip times or other desirable characteristics, the initial mass of a cryogenic propulsion system increases rapidly to values far greater than higher-energy systems. Therefore, while a cryogenic system requires the least development, it ties the mission planner to minimum-energy profiles with little flexibility to modify the profiles. A cluster of propulsion modules performs the Earth departure maneuver. A single propulsion module performs Mars orbit insertion (Mars capture) and Mars departure for Earth. The system includes the interplanetary crew habitat and a Mars lander.

5.3.2.2 AerobrakingIn the case of either cryogenic or nuclear propulsion, propulsion is used at Mars to slow down. Atmospheric drag can be used for the same purpose, i.e., aerobraking. It is presently believed that aerobraking can be developed for arrival velocities at Mars up to about 7 km/sec, corresponding to an entry velocity of about 8.6 km/sec. The velocity depleted by aerobraking at the maximum entry velocity is about 4 km/sec. (The velocity depleted at Mars arrival for a minimum-energy mission is less than 1 km/sec.) Design studies of aerobrakes have indicated that a brake mass of 15% to 20% of the net payload is adequate to produce a 4 km/sec deceleration. Cryogenic propulsion would require a mass factor of almost 200%, and nuclear propulsion approaches 80% to accomplish the same maneuver. Propulsion is still needed for the acceleration maneuvers of the mission. Cryogenic propulsion is usually selected as there are problems in devising a safe configuration for a nuclear propulsion system integrated with an aerobrake. Aerobraking offers little advantage over cryogenic propulsion for minimum-energy missions, but can perform conjunction fast transfer and opposition/Venus swing-by mission profiles with an initial mass in the range 800 t to 1000 t.

A cryogenic propulsion and aerobraking vehicle combination was included in the NASA "90-Day Study" [22]. As above, the cluster of propulsion modules performs Earth departure. The Mars capture and departure propulsion stage is replaced by an aerobrake and a much smaller propulsion stage for Mars departure only. The aerobrakes for the interplanetary vehicle and the Mars lander are similar in size. The mission plan has the two vehicle elements separate before Mars arrival, each to separately undergo aerocapture. Following capture, the vehicles rendezvous and rejoin for crew transfer to the lander.

5.3.2.3 Mars Direct, with In Situ Resource Utilization


A variation on the conventional cryogenic/aerobraking mission to Mars is the "Mars Direct" approach advocated by Zubrin and Baker [26]. This mission scenario requires no Earth orbit assembly operations. An entire MAV/ERV (Mars Ascent Vehicle / Earth Return Vehicle) is launched from Earth without crew and landed on Mars. Later, a separate habitat spacecraft with crew is launched from Earth and landed on Mars. The crew will then use the previously landed MAV/ERV to return to Earth at the completion of their mission. Previous investigations identified severe mass penalties for launching the relatively massive interplanetary return habitat from Mars rather than from Mars orbit. Baker and Zubrin avoid most of this mass penalty by producing methane and oxygen propellant for the return launch from Mars' atmosphere, using liquid hydrogen brought from Earth (see Addendum II).

The Russians are working on a system to use spacecraft carbon dioxide and water to generate methane and oxygen. The return system is sent ahead, then fueled and checked out robotically, before the crew leaves from Earth. The crew arrives in the main surface mission habitat, landing in proximity to the return system. This concept is applicable to a mission approach where the first human mission uses a conjunction profile and stays on Mars for about 11/2 years. Mission analysts differ on the relative merits of this mission profile; it is sensitive to assumptions and to mass estimates for the return habitat system. With modifications, this concept is applicable to the "colony mission" described below.

Missions faster than the Venus swing-by, such as opposition missions without swing-by, generally lead to encounter velocities exceeding the capability of aerobraking. Propulsion must be used to slow down before aero-entry, hence initial mass increases rapidly. Aerobraking performance capability is generally regarded as inadequate for these missions.

Aerobraking was dismissed by the United States Synthesis Report [24] as a high-risk approach. Risks cited include uncertainties in Mars' atmosphere including vertical and horizontal density waves, the problem of designing a guidance system capable of navigating the uncertain atmosphere and precisely removing the right amount of velocity, and the probable need to assemble large Mars aerobrakes in Earth orbit. Studies and experiments completed since the Synthesis Report was released indicate these risks to be manageable. An open issue for aerobraking is the adequacy of subscale demonstration of aerobraking at Mars as demonstrated by a precursor mission prior to human use. Is a full demonstration needed, for example, on an initial cargo delivery mission? Aerobraking has now been demonstrated successfully in the atmosphere of Venus during the Magellan mission.

5.3.2.4 Nuclear Thermal PropulsionThe prototype nuclear thermal rocket engines developed during the U.S. Rover and NERVA programs delivered a specific impulse of slightly more than 800 seconds, i.e., nearly twice as efficient as cryogenic propulsion. Engine and liquid H2 tankage mass "eat up" a good part of the Isp gain, however. Improved fuel element technologies developed since these programs should enable attaining an Isp of about 925 seconds. Thus an Isp of 925 seconds is used for current mission planning. Seventeen nuclear thermal propulsion concepts were reviewed during a 1990 workshop for the United States Space Exploration Initiative (SEI) study [103].

Most nuclear propulsion vehicle concepts use propulsion for all maneuvers, but attempts at nuclear/aerobraking concepts have also appeared. One of the more practical of these employs nuclear propulsion only for Earth departure (the principal ÆV of the mission), aerocapture for Mars arrival, and cryogenic propulsion for Mars departure. This avoids aerocapture of a nuclear


propulsion system at Mars. Since an aerobrake is much more efficient than nuclear propulsion for Mars capture, this scheme usually shows less initial mass in Earth orbit than an all-nuclear propulsion vehicle, despite the relatively low Isp of the cryogenic system for Mars departure. This approach has, however, been criticized as combining the disadvantages of both aerobraking and nuclear propulsion.

5.3.2.5 Nuclear and Solar Electric PropulsionElectric propulsion systems are capable of any exhaust velocity up to the speed of light, giving them an Isp approaching 30,000,000 seconds. While it might seem that a higher Isp is always better, it is not. Electric propulsion systems are power-limited, which means that the mass of machinery needed to produce thrust is a primary limiting factor in the design. The thrust produced is proportional to Isp and mass flow rate via the "rocket equation". If the designer selects too low an Isp, the mass of propellant required for the mission becomes large. If too high an Isp is selected, insufficient thrust is available to perform the mission in the time assigned, at reasonable mass flow rates. Before that limit is reached, the mass of the power system becomes large and overshadows that of propellant and payload. The net result is that an electric propulsion system always has an optimum Isp. For Mars missions, the optimum value generally lies between 3,000 and 10,000 seconds, about an order of magnitude greater than the cryogenic and nuclear systems described above. The optimum Isp depends strongly on electric generation system specific mass, which should be less than 30 kg/kW or so for electric propulsion to be attractive.

The dominant feature of an electric propulsion system is its electric powerplant and thrust-producing systems. This is unlike cryogenic and nuclear thermal propulsion systems, which at the beginning of a mission consist mainly of propellant mass and the tankage to contain it. At the optimum Isp, in many cases, it occurs that the initial mass of an electric propulsion vehicle is roughly 1/3 payload, 1/3 powerplant and thrusters, and 1/3 propellant.

Electric power may be produced in space by either nuclear or solar generators; the latter are usually large photovoltaic arrays. Electric power can also be produced by chemical means, such as fuel cells, but since a conventional cryogenic rocket engine converts nearly all the available chemical energy into jet energy, it is clear that a chemically powered electric propulsion system is not attractive. Only with essentially unlimited energy from the source is electric propulsion useful, and then only because very high jet velocities are not attainable by direct thermal expansion of a hot gas. The temperatures needed far exceed today's containment technology. (Perhaps in the future when thermonuclear containment technologies are far enough advanced, a thermonuclear, i.e., fusion, reactor may be converted into a high-performance rocket engine.)

Nuclear generator concepts usually employ turbogenerators operating on a Rankine (liquid/vapor) cycle, a Brayton (gas) cycle, or occasionally a Stirling (gas) cycle. The working fluid is heated in the reactor, or in a heat exchanger heated by the reactor, then expands through the turbine, generating shaft power and driving the generator.

The configuration of a typical nuclear electric Mars vehicle is dominated by the large thermal radiators needed to reject waste heat from the power cycle. The interplanetary crew habitat and Mars lander are similar to the concepts described above and give an idea of relative scale. This vehicle has no expendable elements except the Mars lander. The entire vehicle returns to an Earth orbit and is recycled for another mission. Recent studies have indicated a preference for servicing


large electric propulsion vehicles in high Earth orbits or at a lunar libration point, rather than in low Earth orbit.

Turbogenerators are a common means of electric power generation on Earth, as for example steam and gas turbines. They are inexpensive, reliable and compact. Turbogenerators have never been used for space power generation. Solar arrays have always been simpler and less expensive to develop. However, for electric propulsion, high power-to-mass ratio is very important and nuclear-powered turbogenerators offer as much as twice the power-to-mass ratio of even very advanced solar arrays. To obtain high performance, it is necessary to reject heat at moderately high temperatures, e.g., 500¡ C. This dictates cycle maximum temperatures near materials limits, and in the case of Rankine cycles, a metal liquid/vapor working fluid (the Brayton cycle can use noble gases, e.g., helium). These factors lead to a projection of high power system development costs. Thorough estimates do not exist, but those that have been made place the development cost of high-performance, high-power nuclear electric space power systems suitable for electric propulsion considerably greater than the cost of developing nuclear thermal propulsion.

The Russians have developed a stationary nuclear electric power generation technology of in-core thermionics, as used in the Topaz reactor. Thermionic cells generate electric power by electron emission and transfer across a near-vacuum voltage gap when the electron emitter is raised to a high temperature and the collector is at lower temperature. Temperatures are considerably higher than turbogenerator systems, but low pressures and lack of rotating machinery mean that materials mechanical stresses are very low. The in-core system places the thermionic cells in the reactor core where the emitters are directly heated by fission plates and the rest of the system is near the lower collector temperature. The Topaz system is about 1,000 times too weak for the propulsion purposes discussed here.

Solar electric propulsion has been used on a small scale in space in that certain communications satellites use electric-heat augmentation of hydrazine thrusters for station-keeping. The Isp is improved by about 50 seconds. Arcjets are now in use on communications satellites, and ion jets are being developed. Solar electric propulsion for human Mars missions will require solar electric generation of several megawatts, about 100 times the solar electric generation capacity planned for the International Space Station. While the ultimate technical feasibility of such large solar generators (photocells or solar dynamics) is not in doubt, the cost of such a system using today's space solar array technology (or solar dynamic plant costs) would be prohibitive. Recent evaluations of the promise of solar electric propulsion for Mars missions indicate that array production costs need to be reduced by about a factor of ten, and that if this could be done, solar electric systems would be superior economically for this mission.

5.3.3 Mars Human Flyby and Mars Orbiter ExpeditionsOne conservative option is to complete the mission verification of a Heavy Lift Launch Vehicle, the Mars Interplanetary Spacecraft, and the life-support systems by performing a Mars Flyby with crew and/or performing a human Mars Orbiter expedition. Some observers believe the cost-benefit return would be too low for such missions, even with stopovers at Phobos or Deimos, and they prefer that a Mars landing be included in the first mission [104].

5.3.4 Assembly of Interplanetary Vehicles in Earth OrbitThe Mars vehicles described here are too large to be launched from Earth in a single launch. The question of how many launches and how much orbital assembly is required is of course related to the lift capability and payload accommodation volume (shroud size) of the launch vehicle as well as


overall program architecture. Assembly analyses for the vehicles described above have considered low Earth orbit payload capability from 100 t to 250 t [105] and shroud diameters of from 10 m to 14 m, with payload bay lengths of 30 m to 50 m.

In a recent study, the nuclear thermal propulsion vehicle packaged nicely into about 5 launches of 180 t each, and using a 12 m x 30 m shroud [105]. All-cryogenic systems tend to be dense but massive, and need at least a 150 t vehicle capability to LEO to keep to a reasonable number of launches. Early studies of aerobrakes indicated severe packaging problems, but these were later largely solved. Electric propulsion vehicles also appear to have packaging problems, but packaging has not been studied in depth. Reasonable solutions probably exist as they did for aerobrakes. Nuclear electric systems using thermodynamic, e.g., Brayton or Rankine cycles, are likely to require joining of fluid systems and charging them on orbit. Joining will require a well-developed space welding technology since liquid metal and helium systems are both notoriously difficult to seal against leaks.

Some early NASA concepts for orbital assembly invoked large, complex orbital structures (transportation nodes) that surrounded the vehicle to be assembled. These assembly facility concepts appeared to pose more of an assembly problem than the vehicles they were intended to assemble. Later studies, concentrating on nuclear thermal propulsion vehicles, have progressively simplified assembly concepts by emphasizing design of the vehicle for simple assembly. One current scheme has been reduced to a grappling and positioning device launched with the first segment of the nuclear propulsion vehicle itself. A similar approach could work for all-cryogenic and cryogenic/aerobraking vehicles. Electric systems appear to pose a more difficult problem but have received relatively little study. A nuclear electric vehicle concept devised by the NASA Lewis Research Center used modular reactor/ powerplant assemblies, each one of which could be launched intact. A cluster of these assemblies produced enough power for Mars transportation. It was argued that the joining of fluid systems on-orbit is not required.

Alternatively, Earth orbital assembly could be bypassed and one could plan the rendezvous of components in Mars orbit, or on the surface of Mars. A comparative study of such alternative assembly versus Earth orbit assembly should be made.

5.3.5 Colony MissionsIt has long been observed that the difficulty of a human Mars mission stems from the need for a round trip. It is proposed to send permanent habitation facilities to Mars in advance of the colonists. If no return is contemplated, the transfer habitat can also be landed to augment habitation facilities delivered in advance. A Mars colony of adequate size might eventually become self-sufficient and independent of Earth. Today, good estimates do not exist for the size of such a colony or the technology development time and investment needed to achieve self-sufficiency. While a colony mission could be several times as efficient as conventional missions in terms of human exploration time on Mars versus cost, it would require a firm commitment of continuing support from Earth for at least decades to avoid failure and loss of the colony and its people. However, if the international community adopts settlement of Mars as a prime objective of human trips to Mars, colony missions offer an efficient, direct approach to that objective.

5.4 CRITERIA AND MISSION ARCHITECTURE SELECTION

This section describes criteria and mission architecture selection considerations. Recommendations are made for investing in priority technology advancements.


5.4.1 International ConsiderationsFor an international project, it is essential that the contractual development, production, and operations of the Mars vehicles and the associated ground and support systems be internationally shared. A Mars mission lends itself well to this end, since there are many major components and a large number of minor ones. A work package map for a Mars nuclear thermal propulsion mission, for example, including Mars surface systems and Earth-based support and operations systems, would need to be developed. This map should maintain simple interfaces among the flight elements to simplify project management. However, since the public might not allow the flight of large nuclear reactors (thousands of MW of thermal power for NERVA-types) into space, mission planners will have to deal with this issue or use the slower chemical propulsion missions. It is apparent that there is a large degree of flexibility for distributing the work among international partners. This flexibility exists for cryogenic and aerobraking systems. Electric propulsion systems tend to have somewhat less flexibility in dividing the interplanetary propulsion system work.

5.4.2 MassInitial mass of the space vehicle in low Earth orbit (often abbreviated IMLEO) is frequently used as a primary system selection criterion in Mars mission system studies. If no other measure is available, mass can serve as a cost indicator. Actually, as the following examples show, mass per se is not sufficient to discriminate among alternatives. The initial mass is related to the number of Earth launches required to perform a mission, but this number may also be driven by packaging problems so that the least mass system may not always require the fewest launches. Mass of space vehicle hardware is also related to development and production cost, but for high-thrust systems most of the IMLEO is propellant mass. An electric propulsion system can have the least IMLEO and the highest hardware mass. For repeated missions we are more concerned with resupply mass (that required to perform repeat missions) than initial mass. For an expendable system those numbers are the same or nearly the same. Electric systems, however, are usually conceived as reusable. Since they need comparatively little propellant, they can be much more attractive in terms of resupply mass than initial mass. An electric system with initial mass of 600 t may have a resupply mass as low as 200 t while an expendable nuclear thermal propulsion system would require the entire 600 t for every mission. All this is true only if system lifetime permits reuse.

5.4.3 SafetyCrew safety is clearly very important, if perhaps difficult to quantify. A common practice is to design all options to the same safety standards and compare them on other criteria. However, even if all are designed to the same standard, there may be differences in how well the standards are met or in best estimates of actual safety probabilities. The split mission strategy may allow a reduction in risk to the crew due to an ability to emplace and checkout landed cargo systems before a crew is launched from Earth. Safety and acceptable standards for safe return were discussed above under "Abort Options" (Table 5.1).

Public safety of people on Earth is also of concern. This will probably place certain constraints on the use of nuclear propulsion and power. Design of missions and systems must ensure that the probability of inadvertent Earth landing or crash of a radioactive nuclear reactor is vanishingly small. Consequences of uncontrolled Earth landing or crash of large non-nuclear systems are also severe enough that such events must be engineered out of Mars mission systems.

5.4.4 Cost


Assuming mission requirements are met and risks are controlled, cost is the most important criterion. Specific mission programs are usually designed through compromises between mission goals (early and ambitious versus later and limited) and cost. Two cost measures are especially pertinent; unfortunately they conflict. The first is often expressed as non-recurring (mainly development) cost; the second is any one of several variations of life-cycle cost.

The best measure of "non-recurring" cost is the total cost to achieve a first human mission to Mars. This includes some production tooling and operations cost as well as research and development costs. Options and programs that achieve lower costs for the first mission will, unless continuing technical evolution is built in, exhibit high life cycle costs because these options tend to use all-expendable systems. A minimum-cost initial mission to Mars would use all-cryogenic interplanetary propulsion on a conjunction-profile (long stay) mission, and storable propulsion near Mars. Risk to the crew may be too high for such a trip because of the long exposure to galactic cosmic rays and microgravity. If this is the case, nuclear thermal propulsion on an opposition-swing-by or a conjunction fast transfer profile may likely provide least cost. If large nuclear systems prove politically infeasible, then solutions for the slower missions (such as Mars-Direct) will have to be developed.

Low life-cycle costs are important to a program with repeating missions to Mars or one that strives to provide for permanent habitation. Life-cycle costs are minimized by advanced technology and reusable systems, features which incur high non-recurring costs. The only way to reasonably satisfy both cost criteria is through an evolutionary program that includes advancements of technology to reduce recurring cost after early program objectives are met. An example of a low recurring cost system is a long-life reusable solar or nuclear electric vehicle refueled by reusable Earth launch and orbit-to-orbit transfer systems using cryogenic propulsion. Lifetime reliability issues exist for both solar and nuclear electric propulsion systems. But, if these issues can be solved, both propulsion systems offer promise of lower recurring cost operations.

5.4.5 Technical and Cost RisksTechnical risk has two aspects: (1) failure to develop technical capabilities or systems within the time and budget allotted; and (2) failure of a system or mission due to an unanticipated failure of newly developed hardware/software or personnel performance error due to unfamiliarity with the system. Such failures increase cost. But, cost may be increased by poorly structured program management or by inadequate funding, e.g., test budgets, to begin with.

Technical risks are inherent in an undertaking like Mars exploration. Risks can be reduced but not eliminated. There always remains the chance of an "unknown"; a risk or technical problem that goes unaddressed because we simply are ignorant of its existence.

Measures that reduce risk are often under scrutiny and pressure for elimination because they cost money. Testing is expensive, as are rigorous and thorough safety and quality reviews. Engineers frequently believe their designs will work properly without thorough testing, despite ample evidence to the contrary. The U.S. Space Shuttle program, for example, was significantly delayed because the thermal protection tiles were initially tested only for their thermal protection performance and not as an integral part of the total Orbiter airframe structural system. When the tiles blew off the Columbia as it was air transported from California to the launch site in Florida, it became apparent that the design was faulty. It took two years to re-engineer it, thus increasing costs.


This points out that risks incurred by adopting new technology for a program are exacerbated by a political/program management reluctance to adequately fund the testing and development necessary to mature the technology and minimize technical risks. System selection must therefore balance the risks and costs of new technology with the risks of not using new technology and the costs of the alternatives.

5.4.5.1 Technological AdvancesIn the case of long-duration, remote human missions, there are certain technological advancements essential to a safe and successful mission.

Onboard vehicle maintenance and repairThe Russian space station experience demonstrates that it is possible to put a complex system in space and have flight crews maintain it in operation over a period of years. The human mission to Mars challenge is more difficult in two ways. First, the vehicle will be considerably more complex than the Russian stations. Second, all spares, repair parts and tools must be pre-planned and placed onboard the vehicle before it leaves Earth since the flight mechanics of Mars mission profiles makes resupply impossible. Further, more reliance must be placed on the onboard crew and systems for diagnostics and maintenance in view of the communications time delays.

This is a difficult area for which to devise technology programs since one cannot prescribe a specific performance target for a particular device or system. A combination of hardware maturity, operational experience, and automated test and diagnostics procedures is needed. Experience with the Russian Mir space station, with Apollo 13, with Shuttle and planning the International Space Station stress in situ repairability. The state-of-the-art of automated diagnostics is more advanced in commercial and military aircraft systems than in space systems. Appropriate technology transfer needs to take place. Finally, much more research and development emphasis on automated test and diagnostics systems and protocols tailored to space flight systems needs to be given.

Life SupportSizable storage reservoirs of water are useful for shielding the crew from radiation and for emergency supplies; so full closure of water and oxygen loops (complete recycling), while attractive from some standpoints, may not be needed. Improvements in current waste recovery methods are needed, especially in water recovery from waste, in agricultural utilization of waste, in reducing consumable element usage such as filters, and in converting compacted waste reserves to fuels or atmosphere.

Bioregenerative systems are not needed for initial missions to Mars, but are very important for permanent bases or settlements. We are far from understanding how to implement and operate a truly closed bioregenerative life support system.

Mars Surface Space SuitsCurrent orbital EVA suits are designed for operation in zero g, and hence the mass of the suits has not been a primary design criterion. These suits are too heavy to use on Mars at 3/8 g, as is also true for the 1/6 g Apollo suits. Improved mobility is needed. Also, current suit technology will not support large numbers of EVAs. Space station activities and requirements are expected to increase the useful life of suits and to develop technology and experience for on-orbit suit servicing. To date, U.S. Space Shuttle requirements have seen no more than four uses of a suit before return to Earth. Suits go through extensive ground-based servicing after each Space Shuttle flight. The Russian suits may be somewhat more serviceable on-orbit, but the Russians initially performed relatively few


EVAs from Mir. Since the main reason for a Mars mission is to explore, we expect daily or at least weekly EVAs, with perhaps up to one hundred uses of each suit on a 1-1/2 year surface stay. Further lunar base experience will help.

5.4.5.2 Trade-Offs Between New and Existing TechnologiesOther technology candidates fall into the category of trade-offs among new and existing technologies and cost. Some of the more important trade-off candidates are:

Cryogenic Fluid ManagementWe can design a Mars mission to fly with some cryogenic fluids management investment including high-performance tank insulation and heat leak interception, which is already a proven technology for the IRAS satellite. A total combined system must be evaluated, including the greater operational flexibility and economy that can be derived from the ability to transfer fluids and measure quantities in orbit and on the mission. Without transfer, each cryotank must be launched loaded with enough propellant for the mission and for boil-off that will occur before the tank is used. With transfer, fluids may be partitioned for launch so that launch vehicle efficiency is maximized, and tanks may be subsequently topped off before use.

Nuclear Thermal PropulsionWithout nuclear propulsion, we are confined to using the conjunction profile, or the opposition/swing-by profile if high-energy aerobraking is developed. High-energy aerobraking, however, may involve more risk than nuclear propulsion. (Low-energy aerobraking is needed for Mars landing but does not involve the guidance and control and aero-heating challenges of aerocapture.) Nuclear propulsion opens the opportunity for fast conjunction profiles, reducing the risks associated with many months of microgravity crew operations before Mars landing, and for opposition profiles that reduce overall mission time by almost half compared to conjunction profiles. The essence of the trade is that nuclear propulsion offers faster trips, hence less crew exposure to galactic cosmic radiation and to zero g, reduced initial mass and hence reduced launch cost, but it will cost several billion dollars to bring nuclear propulsion technology to a state of flight readiness, assuming that the public would accept it at all. Using artificial gravity would also possibly reduce the effects of long-term space flight and enhance the shorter trip-time advantage of nuclear thermal propulsion.

Nuclear Electric PowerNuclear electric power at the multi-megawatt level would be needed to power nuclear electric propulsion systems for Mars interplanetary vehicles. Advances in electric propulsion are also needed but these are a minor challenge compared to multi-megawatt orbital generation systems. A broad effort, over many years, is needed to develop high-power reactors, fluid loop and heat transfer components, turbogenerators, thermal radiator systems, and space construction techniques to a readiness level for full-scale development. While nuclear electric propulsion is technological overkill for a small exploration program of a few missions to Mars, its transportation efficiency would be highly beneficial for an extended Mars exploration program or for a Mars settlement.

Solar PowerSolar power may be useful on Mars, but there is a major issue concerning global dust storms. Present estimates, rather uncertain, indicate that during a major global dust storm the output from a planar solar array on Mars would drop to 30% of its clear weather value, and the output of a concentrator array would drop to zero. Sunlight is significantly weaker on Mars than on Earth due to Mars' greater distance from the Sun. A 100-kilowatt power system, approximately needed for a


six to eight-person long-term base, would require a Sun-tracking array the size of a football field, or a non-tracking array about twice that size. Thus the real issue is the mass of the collectors required and the relative risks between solar and nuclear power systems. Mass delivery to Mars is very expensive.

Advanced Storable PropulsionAscent from Mars to an elliptic or high Mars orbit requires a ÆV greater than 5 km/sec. Since Mars has atmosphere, the multi-layer insulation systems that are so effective in space will not work on Mars unless vacuum-jacketed. Even with the mass of a vacuum jacket (which is little on Mars since atmospheric pressure is low) and with boil-off, a cryogenic propellant ascent system has much better performance than a conventional storable propellant system. Advanced storable propellants minimize the difference and alleviate concerns about the integrity of vacuum jackets. Technology improvements in high-pressure tanks using advanced composite materials, improved combustors, improved propellants (e.g., hydrazine instead of MMH), and metal additives with gelled fuels all offer beneficial performance and achievable improvements for Mars ascent vehicles using storable propellants. These systems still fall short of cryogenic system performance, however.

In Situ Resource UtilizationUse of in situ resources is imperative for settlement of Mars or even for large semi-permanent bases. Initial benefits can be realized as soon as in situ processing is put in place. Breathable atmosphere can be made from Mars' atmosphere. Oxygen can be separated from the CO2 in Mars' atmosphere; the atmosphere also contains some nitrogen. Mars appears to have abundant water, albeit frozen at the polar caps or as permafrost. Water can be electrolyzed to hydrogen and oxygen with electrical power. Common metals are plentiful in the soil. The atmosphere and water contain the ingredients of plastics and carbon fibers. Production of hydrogen or methane and oxygen on Mars would enable Mars lander/ascent vehicles to be reusable, based on Mars, and would provide propellant for Earth return. These propellants are also needed for Mars surface vehicles and point-to-point flyers. With in situ propellant production, a fully reusable, efficient Earth-Mars transportation system could be put in place. Metals, plastics, and composite materials would enable base facilities construction without massive cargo shipments from Earth.

5.4.6 System Evaluation ModelsFaced with a wide variety of mission architectures for a combined robotic and human Mars Exploration Program, it would be useful to have a Mars Mission Evaluation Model for optimization. While no such model can capture the true impact of the many variables (continuous and discrete, stochastic and deterministic, using linear and non-linear constraints) such a model could evaluate strategies, choices, and alternatives for the achievement of exploration goals. Several such models have been suggested and have been used to guide initial strategic architectural choices [104]. Also see Addendum III, which contains trade-off methodology.

5.5 REPRESENTATIVE MISSION ARCHITECTURES

Many mission architectures can be contrived for the exploration of Mars. Those described here represent three very different scenarios, selected to suggest the range of possibilities, including trip times. These descriptions are not meant to advocate these particular architectures over others.

5.5.1 Minimum New Technology Architecture


An architecture confined to the essential technologies described above must use all-cryogenic propulsion on conjunction profiles with long stays at Mars. To support the long stays, 200 t of cargo must be pre-positioned on Mars before the exploration crew arrives. This will be done using one or more prior Mars opportunities, as four 50 t cargoes: 1) the habitat module; 2) power and thermal utilities modules; 3) exploration equipment; and 4) backup Mars ascent vehicle. Each 50 t cargo is delivered to the surface by an 80 t gross mass Mars lander, which requires a 240 t total mass transportation vehicle in low Earth orbit to launch it on a low-energy trajectory to Mars using cryogenic propulsion. The cargo landers will arrive at Mars with direct entry velocity only moderately greater than for entry from Mars orbit (5.87 km/sec vs. 4.72 km/sec). They will enter Mars' atmosphere, will slow down, and will land. The landers will home-in on a beacon located on the first lander, close enough together to assemble the base.

The initial mass of the crew vehicle in Earth orbit is about 800 t. The crew vehicle performs a conjunction round trip profile, with about 6 months travel time to Mars, 1-1/2 years on Mars, and 6 months to return. Upon arrival at Mars, the vehicle establishes an elliptic orbit of 12 to 24 hours period and the crew descends to the surface. At the end of the surface mission, the crew returns to Mars orbit using one of the two ascent vehicles, rejoins the interplanetary ship, and departs for Earth. Upon Earth arrival, the crew enters and lands using the Apollo-like crew return vehicle. The rest of the vehicle is abandoned, passing Earth on a hyperbolic trajectory and returning to interplanetary space.

Assuming a launch vehicle of 80 t to 100 t capacity (such as the current Russian Energia), 12 launches are needed for cargo delivery and about 10 for assembly of the crew vehicle. Each cargo mission can be divided into three parts that dock together automatically. The crew vehicle may require some human-assisted assembly, but automated assembly is baselined. It is advantageous to minimize assembly time in low Earth orbit in view of cryogenic boil-off and orbital debris.

5.5.2 Early Human Reconnaissance Architecture: One Possible LayoutNuclear thermal propulsion (NTP) lends itself to early human reconnaissance via flying an opposition profile. A fully self-contained mission is visualized, with two small landers of about 50 t each configured to support half the crew of six for one to two weeks on the surface. The NTP vehicle consists of one large lander. This mission spends one to two months in Mars orbit. After selection of a landing site, the first lander descends and its crew performs the surface mission. The second lander is available as a backup to the first one or it can be used by the other half of the crew to explore a second site after the first lander has completed its surface mission. The vehicle spends about five months going to Mars and ten months returning, for a total mission duration of about 500 days. Initial mass in Earth orbit is about 800 t, as for the first architecture, but no prior cargo deliveries are performed.

As in the U.S. Synthesis Group architectures [24], subsequent missions can increase in capability by emplacement of cargo on Mars, thus supporting longer stays. Unlike the first architecture (5.5.1), nuclear propulsion enables repeating opposition mission profiles, operating in a crew rotation/resupply mode, and supporting continuous human presence on Mars.

5.5.3 Extended Exploration/Settlement Architecture: One Possible LayoutAn extended exploration program (see Chapter 6) is best served by a reusable architecture with low recurring cost. A representative architecture uses nuclear or solar electric propulsion for interplanetary transportation, based at a lunar libration point, e.g., L2. Mars cargo, crews, and transfer propellant are delivered to low Earth orbit by a reusable launch system. An electric-


propelled cislunar ferry operates between low Earth orbit and the L2 libration point, carrying cargo and propellant. This propulsion system may use solar, nuclear, or Earth-based laser energy. A reusable cryogenic (high-thrust) crew transport system also operates between low Earth orbit and L2, refueling at L2 from propellant delivered by electric ferry or from production on the Moon. The interplanetary electric propulsion vehicle flies opposition-like, low-thrust profiles providing crew rotation and resupply to a permanent base or settlement on Mars.

Transportation service between Mars surface and a high Mars orbit is provided by a reusable lander/ascent vehicle based on Mars. It is fueled for descent and landing with propellants delivered by the interplanetary ship and for ascent by propellants produced on Mars. The electric ferry and interplanetary vehicles could use lunar-produced propellant if a compatible propellant product and thruster technology were developed. (Current electric thrusters operate on argon or hydrogen, both scarce on the Moon.)

A system such as that described above, and there are many possible variants, will operate with Earth launch of Mars cargo and transportation system propellant in roughly equal proportions. With in situ production of food and exploration consumables on Mars, Earth launch requirements to support Mars exploration on a significant scale are on the order of 1 t. per year to 10 t. per year to low Earth orbit for each person on Mars. Direct operating tonnage for Earth launch operations to support 100 people on Mars would be 100 t. to 1000 t. to low Earth orbit per year. At an estimated $20 per gram (typical government launch cost) we need $2 to $20 billion yearly, just to support the launch requirements. Current commercial launch prices are about $10 per gram and are forecast to drop to $7 - $8 in five years. Placing a Mars launch requirement on the competitive commercial market could drive prices farther down, below $5 per gram. Thus, the cost for Earth launch support could be as low as $0.5 billion per year, to several times higher. Most of the cost of exploring Mars on this scale, with this class of architecture, is amortizing the initial investment in the architecture. This investment is expected to be reduced by purchasing Earth launch requirements from the commercial sector, when the commercial sector is able to serve the Mars-destination market.


Chapter 6MARS SURFACE SYSTEMS AND OPERATIONS

The role of the Mars Surface System is ultimately to provide (with a modest start) a complete spectrum of capability for realization of the international exploration community's goals for robotic and human exploration and possible future settlement of Mars. This capability may include pre-programmed and autonomous robotic systems, teleoperated rovers, stationary geophysical stations, initial Mars human expeditionary outposts, self-supporting human bases, and Mars-based space transportation systems. The Mars Surface System will be derived from the basic exploration goals as established by the international community. For this study, it is assumed that these goals and objectives are as specified in Chapter 2, "Why Mars?". That Chapter has defined two major categories of goals: 1) to acquire new scientific data, with several subdivisions by discipline; and 2) to understand and determine the practicality of Mars as a future abode for humans (precursor role). To plan the Mars Surface System, it is necessary to examine these fundamental top level goals, to derive the next level of requirements, and then to conceptualize a set of temporal relationships, interactions, and phase transitions that best describe a strategic approach that ensures accomplishment of those goals.

This Chapter is divided into four major sections. The first section gives an overview of the derived strategic approach. The second section is a discussion of the derived requirements as determined by the Mars Surface System international study team. And the last two sections discuss the operations and the implementation concepts. It is implicitly assumed in this Chapter that the International Mars Exploration organization has successfully brought together an international team to implement surface operations. There are no provisions for separate national sites or agendas. This is consistent with Chapter 3, "Why International?", and with the thesis of this report that international exploration of Mars will bring greater benefits to the world than purely nationalistic exploration. While specific national projects may occur simultaneously, the IAA Subcommittee on the International Exploration of Mars believes it is preferable that these be part of an international plan.

6.1 STRATEGIC APPROACH

Goals of Mars exploration require the Mars Surface System to support the collecting of scientific data that increases our understanding of Mars on a global scale and supports the development and verification of Mars as a future abode for humans [74]. Upon examining those two primary goals, the Surface System team collected subsidiary goals under two categories: "Exploration", and "Human Expansion". These categories require different implementation schemes. Exploration generally emphasizes "global" Mars coverage with temporary human presence at any single site, and Human Expansion emphasizes growth and evolution outward from a single site with permanent human presence. The current Administrator of NASA, Dan Goldin, has espoused this view: "Our goal should be a sustained presence on Mars, not a one-shot, spectacular mission. Emigration, not invasion" [34]. These different schemes are shown in Figure 6.1. Possible implementation options are shown in Figure 6.2.

A characteristic of the planetary Exploration goal is that it is ultimately desirable to visit a multiplicity of sites. This implies either the capability to travel great distances across the surface of Mars using a mobile "base" concept, or that many sites can be visited from an orbital base, or that there are several separate Mars landing expeditions. Therefore, large, evolutionary settlements that grow outward from a single site are not envisioned as a practical implementation approach for the Exploration goal. Elements that provide temporary support associated with limited means and


short durations are most appropriate. Indeed, the area likely to be explored around a Mars site of interest is foreseen to be compatible with short duration stays, on the order of months.

Figure 6.1: Conceptual Illustration of the Strategic Approach (also see [106])The goals of the International Exploration of Mars require balancing desired "global" coverage

of Mars with expansion of a permanent "Abode of Human Habitation" from a central point.

Figure 6.2: Possible Basing OptionsThere exist many possible basing options for the International Exploration of Mars. The final

selection of the best option must be made within the very specific parochial interests of the international partners involved at the time the decisions to begin execution are made.


On the other hand, the Human Expansion goal requires a different approach in that a human settlement begins with a unique landing site from which a surface base infrastructure may grow outward. This may be only the first step, in that a global multi-settlement collection of autonomous colonies might be the ultimate result. Within the framework of the Human Expansion goal, it is expected that increasing capability may be provided by utilization of local resources that will enable much longer surface stays, support other goals, and open the way to long-range surface exploration capabilities.

The implementation and operations concepts must not preclude either approach, but rather must provide for the simultaneous implementation of both through the utilization and exploitation of common assets. Indeed, the Human Expansion implementation must evolve through a growth approach that utilizes the Exploration assets. From the other viewpoint, the Exploration assets must not preclude, and wherever possible, must facilitate future growth. In summary, the challenge of the international Mars Surface Systems implementation team was to discover how to merge these two objectives into a single coherent approach. The two categories were further subdivided into phases as follows:

6.1.1 Mars Exploration PhaseThe Mars Exploration phase is the totality of Robotic and human Expedition missions to the surface of Mars for the purpose of acquiring science data for the global understanding of the planet and its evolutionary history in the Solar System.

Mars Robotic Survey Sub-Phase Robotic surveys are those exploration activities that are required of robotic or telerobotic equipment to support the science objectives as well as to support the acquisition of engineering data needed for the development of the surface systems. The Robotic phase begins before the initiation of the human expeditions, but does not end there. It continues and supports not only the Exploration/ Expedition phase, but the Human Expansion phase as well. Details are discussed in Chapter 4, "Mars Automated Missions and Precursors".

Mars Human Expedition Sub-Phase Mars expeditions are the first human visits to any particular site on the surface of Mars for the purpose of initial surveys, testing engineering systems, and acquisition of science data. Mars expedition sites will "seed" subsequent Human Expansion sites as resources and planning allow. This is accomplished through designing surface assets that remain behind and are reconfigurable and/or restartable.

Initial human exploration stay times on Mars will be approximately either 30 days, or 600 days. The decision between the two options is based upon a number of conditions. An abort option to Mars, as opposed to a return to Earth, implies an initial stay time of 600 days, whereas the prudent testing of systems prior to commitment for extended stay would imply a 30 day stay (e.g., as with Apollo 8) for the first visit. Another consideration is based upon a concept of permanent habitation as opposed to an exploration only philosophy. The initial establishment of a permanent base allows for eventual exploration, whereas the exploration only philosophy would lead to an Apollo-type activity without the need to establish permanent presence. Positioning infrastructure on the surface of Mars from the start will ensure evolution of substantive science with each human visit, but possibly at higher initial costs.

6.1.2 Mars Human Expansion Phase


The Human Expansion phase is defined as that set of activities and concepts that provide the capability to use in situ resources to lessen the reliance on periodic cargo resupply of key resources from Earth. Human Expansion is dependent on and interactive with the Exploration phases. It consists of two sub-phases. The first sub-phase, Outpost, originates at a selected prior expedition site and utilizes the elements left behind by the previous expedition. From that point, it evolves to the second sub-phase, Base, which is developed to be significantly less dependent on Earth resupply through the deliberate use of local resources.

Outpost Sub-Phase This sub-phase tests and develops the systems and technologies that promote self-sufficiency, such as extraction of O2 from the atmosphere and water from the subsurface.

Base Sub-Phase This sub-phase begins with the delivery of the required operational equipment that allows substantial long-term habitation with significant Earth independence through the use of local resources for life support and space vehicle propulsion.

6.2 REQUIREMENTS

An analysis of the mission-level requirements in Chapter 2, "Why Mars?", has yielded the following basic requirements for the Mars Surface System:

Mars Scientific Goals¥ Understand the composition and internal structure of the planet Mars;¥ Determine the geological evolution and ages of Martian surface features;¥ Determine the composition and dynamics of the Martian atmosphere;¥ Determine the origin and history of water on the surface of Mars;¥ Determine the existence and evolution of life on Mars, extinct and extant.

Mars Habitation Goals¥ Determine the practicality of permanent human settlements on Mars;¥ Determine and evaluate methods to make the human settlements self-sufficient and less

dependent on Earth resupply.

The next step in the requirements analysis process is to assign the above mission level goals to potential functional hardware categories so that the surface system assets can be further defined in subsequent studies. This was done through an iterative process and those goals were allocated to major Mars Surface System functional categories that may contain a number of hardware assets. A summary description of the functional categories follows in Table 6.1.

Table 6.1: Allocation of Goals to Functional Implementation Categories(This is the first step in converting the goals into hardware requirements.)

FUNCTIONAL IMPLEMENTATION CATEGORIES

PRINCIPLE GOALS

HUMANSUPPORT

ENGINEERINGSUPPORT

SURFACE ACCESS

SPACETRANSPORT

ACCESSMARS SCIENCE X X


MARS AS A HABITAT¥ HEALTHY AND PRODUCTIVE HUMANS

X X

¥ SELF-SUFFICIENCY X X X

6.2.1 Functional Categories

6.2.1.1 Human SupportDevelop the capability to keep Mars astronauts healthy and productive.One of the key functions of the Mars Surface System will be the support of humans. During the precursor robotic missions, one of the main issues will be to identify and provide solutions for Mars expedition health and safety hazards.

In the expeditionary phase, when humans reach the surface for the first time, life support functions will be primarily provided by supplies and equipment transported from Earth. However, even during this phase, some limited use of Martian resources may be practiced. In particular, O2 production from atmospheric CO2 is desirable because it is one of the most simple and direct methods of in situ resource utilization (ISRU) on Mars, and could be used to augment supplies from Earth to allow for extended Extra-Habitat Activities (EHA) and exploration [76]. Demonstration of EHA and assessment of human performance on Mars could be key steps in this phase. Experiments in ISRU and food production systems would begin in the Human Expansion phase.

Finally, as humans achieve mature levels in the Base sub-phase, food production would be introduced to include growing conventional crops and developing animal husbandry inside Martian "greenhouses". We would expect that most, if not all, life support functions would be developed in situ in the Base sub-phase, such as water, breathable air, food, and the maintenance of a healthy, productive and safe environment. The ISRU equipment would continue to operate after departure of the initial crew and the supplies would be stored for future mission use.

6.2.1.2 EngineeringDevelop the knowledge and data required for the advancement of Mars Surface System operations and Surface System performance capabilities.The objective of this category of implementation assets is to provide those systems and elements that ultimately lead to a self-sufficient base. In early phases, it will include testing and analysis of pilot plant processes for in situ resource extraction. It is anticipated that the first developments will be for the purposes of testing and verifying the production of life support consumables. These tests would probably be accomplished on the robotic missions and the first human expeditions.

As the Mars Exploration subphase evolves to the Outpost subphase, the experiments, tests and developments will include the advanced life support systems, including food growth and production of propellants for surface transportation systems as well as for space transportation systems. In the final phases, as the Outpost is incremented to the Base capability, the engineering tests and developments will now examine the actual operations of the surface and space transportation assets utilizing in situ resources.

6.2.1.3 Surface Access and Support Space Transportation VehiclesDevelop the capability to support the space transportation vehicles when on the surface and to ultimately expand that capability to be totally surface supported.


The initial robotic landers are required to provide navigation capability for later Mars orbit-to-surface vehicles. There are no other Mars Surface Support System requirements on the robotic phase except for engineering demonstrations of the utilization of local resources for propellant production.

For the Exploration/Expedition phase of missions it is expected that lander vehicles will not be resident on the surface long enough to require any surface system support. However, for this phase, it is required that the Mars Surface System initiate the further development of the systems required for the sustenance of a lander vehicle while it is on the surface of Mars, as well as initiating the development of the in situ resource propellant extraction.

In the Expansion phase the capability will be provided for the support and maintenance of the space transfer vehicles while they are resident on the surface. The actual requirements need to be specified by the vehicle design, but should be limited to simple servicing items such as thermal protection, "keep-alive" power, data acquisition for equipment "health" assessments, and some limited propellant maintenance. Also, it is required that some propellants be produced by the Mars Surface System and transferred to the vehicle as a test and validation of the propellant production and servicing systems. As the Mars Surface System evolves to full self-sufficiency, the space transfer vehicle should become fully surface-based, utilizing Mars propellants. Its operational regime should be servicing vehicles that go from Mars surface to Mars orbit for rendezvous with the interplanetary space transfer vehicles, then return to the Mars surface.

6.2.2 Derived RequirementsThe Mars International Surface Systems and Operations Panel used the data in section 6.2.1 to derive a set of requirements for the functional categories identified above. Those requirements are listed in Figure 6.3.

6.3 MARS BASE OPERATIONS CONCEPTS

The basic strategic approach is to design each phase and sub-phase to be interdependent and supportive of each subsequent phase and sub-phase. This approach results in no "dead-ended" hardware, and, in the long run, should reduce costs in that fewer original development programs will be needed. For example, the rover designed for the robotic phase might be the same rover design used to support the human phases. In some cases the actual rover used in the telerobotic sub-phase will be the exact same rover used in the subsequent expedition sub-phase by having it rendezvous with the incoming lander and then temporarily assigning it to the inventory of the lander crew. Also, the "abandoned" hardware from an expedition will be used as supporting assets for the evolution stage. Although each sub-phase depends on the others, the decision to implement any phase is an independent activity. The sub-phase to sub-phase dependency is implemented through the design process by ensuring the availability of the additional performance capability required to support the subsequent phases when, or if, the decision to advance is made based on international resource availability and priorities. Figure 6.4 illustrates the operational approach described in detail in the following subsections.

6.3.1 Exploration ProgramInitiate the Robotic sub-phase of the program


The Mars Robotic sub-phase of the Exploration program will be operated and controlled by Earth-based stations during this initial period. This will require the need for partial automation of Mars assets before crew arrival. The robotic systems should be designed such that they can shift their operational control to the Mars crew when the crew arrives later at the Mars surface. These robotic assets will be much more efficient when operated by the local surface crew because of the greatly reduced communication delay time. However, the operational concept continues to allow Earth-control when it is in the best interests of mission success.

Initiate the Expedition sub-phase of the program The Mars Expedition program will utilize previously deployed robotic surface and orbital assets for navigation. The crew will land at the selected site and will begin autonomous operations, planning their daily routines, assigning their own resources for task execution, and completing the tasks without assistance from Earth. Earth support operations will be limited to top-level, goal oriented planning that will be accomplished on an infrequent basis. The surface crew will hold regular science conferences (or "fax" exchanges because of the time delay) with the Earth-based science team. Using available robotic rover assets as needed, the crew will explore the local area around the landing site (with surface pressure suits and Mars surface personnel rovers). The Expedition program will continue with flights to subsequent sites as desired and/or will begin the Human Expansion Program. It is possible in some scenarios to bypass the Expedition sub-phase and move directly to the Outpost phase. This can be achieved only if it is possible to deploy and validate all human support equipment by automated methods.

Figure 6.3: Derived Requirements for the Mars Surface Systems

The goals and objectives have been converted into the first-level of system functional requirements. Future studies will further analyze these requirements and derive more

specific and detailed element performance parameters.


Figure 6.4: Implementation of Operational Concept (also see [106])All phases and subphases are designed to cooperate and interact with each other to reduce costs through the utilization of common assets. The operational concept for implementation begins with the robotic phase and evolves to more complex bases

through a carefully planned strategic approach.


6.3.2 Human Expansion ProgramInitiate the Outpost sub-phase From a selected expeditionary site, the evolutionary growth will begin by transporting the Outpost sub-phase systems to the site. Alternatively, the Outpost phase can be entered by pre-deploying systems through automated methods. The surface crew will test and certify the resource utilization technologies, test and certify the performance and operations of the other surface systems, and determine the total feasibility for the use of Mars as an abode for human habitation. Then, as the International Exploration Council dictates and resource availability allows, continue to use the Outpost in a steady state, initiate a new Outpost at another expeditionary site, and/or initiate the Base phase of the selected site. The science objectives may be pursued in greater detail from the permanent bases by using personnel transport systems that can give the surface crew a much larger range over the surface of Mars. Also, exploration will continue by Mars-surface control of the robotic rover assets.

Initiate the self-sufficient Base sub-phase The Outpost will be then developed to full operational capability. The utilization of the local resource production plants will begin, in particular, those that support the Mars-based space transportation system. Further experiments will be initiated to utilize alternative local resources, focusing on food production and habitation structure construction. The continuation of the exploration objectives and/or the initiation of another Outpost or Base evolving from a separate site can be supported at this time.

6.4 IMPLEMENTATION CONCEPTS

The potential implementation concepts can vary widely depending on the detailed analyses of the requirements and the special interests of the international partners involved. For example, the "International Mars Exploration Council" (or whatever management concept is employed) will only require the power provider to deliver "X" kilowatts. Different nations who may opt to provide this power may select different generation concepts depending on their parochial interests, skills, and/or Earth-based technology development desires, though the concept selected must be compatible with the rest of the mission architecture. The implementation concepts shown here are only to demonstrate that there exists at least one solution to the problem. The primary need to get to this level of detail at this time is twofold: 1) to give some physical representation of the requirements; and 2) to produce a surface mass delivery estimate for the optimization analysis of the transportation system. The following describes but one potential implementation of the Outpost and the early stages of the Base (see [107] for similar approaches). The Expedition assets are shown on the drawings for reference.

6.4.1 OutpostFigure 6.5 shows a conceptual layout of the Outpost. The mass of the Outpost is approximately 120 t. A portion of this mass is shown in the drawing to have been landed on three carriers of about 35 t each. The additional mass is comprised of mass that arrives with the crew on the piloted flight, and the useful equipment available from the earlier Expedition lander (indicated on the drawing). The cargo is landed during mission opportunities preceding the piloted landings and is partially assembled by remote control from Earth-controlled stations. The crew will complete the setup and initiate operations.


6.4.2 BaseFigure 6.6 shows the additional equipment required for the establishment of the first stage of the self-sufficient Base. The additional mass delivered to the Outpost site is approximately the same as the Outpost itself, 120 t, to yield a very capable Base of substantial independent capability.


Figure 6.5: A Possible Implementation of the Outpost SubphaseThe Outpost habitat is deployed at one of the Expedition sites and is integrated with the

assets left behind by that previous Expedition. The total mass for the landed Outpost assets is 120 metric tonnes for this assumed implementation.


Figure 6.6: A Possible Implementation of the Base SubphaseThe Base habitat is landed next to one of the Outpost sites and is integrated with the

existing assets. The additional mass required to bring the Mars Surface System capability to one of significant Earth independence is on the order of another 120 metric

tonnes, roughly doubling the surface system mass over the Outpost capability.


Figure 6.7A & 6.7B: Placement of Footpads 3 and 2 of Viking Lander [4]Footpad 3 in 6.7A (lower right in top picture) is resting on blocky material.

Footpad 2 in 6.7B (lower left in bottom picture) is buried 0.165 meters below the surface in drift material.[courtesy of U.S. Geological Survey]


6.4.3 Mars Surface Outpost Construction OperationsIn this section the construction tasks that must be performed to achieve a functional First Mars Outpost (FMO) are outlined. These tasks are driven by a surface operations itinerary, which is a detailed construction schedule for the Outpost. It is important to note that this construction scenario was developed only as a tool to identify areas for further surface construction research. Thus, the FMO construction plan presented here is not meant to represent the optimal or best plan, but is instead an example of a construction scenario to be used for envisioning planetary surface construction problems [105].

6.4.3.1 Soil Strength/Site SelectionIn general, we can expect to find all types of soil on Mars, including the three types found at the Viking sites: aeolian drifty material (angles of internal friction between 14 and 21 degrees and cohesion between 0.7 and 3.0 kPa); blocky material (angles of internal friction between 27 and 32 degrees and cohesion between 1.5 to 16 kPa); and crusty-to-cloddy material (angles of internal friction between 32 and 39 degrees and cohesion between .5 and 5.2 kPa). Permafrost conditions may increase cohesion of underground soils.

The engineering properties of Mars soils or regolith are very similar to those encountered on Earth. We can calculate bearing capacities for these soil types, but the data obtained should be viewed with some skepticism because the effect of any subsurface soils (possibly permafrost) is not included in this analysis. Nevertheless, a bearing capacity for an individual 17.5 t type habitation module (Boeing/NASA JSC concept [108]) follows, based on the assumptions that the soil mass is homogeneous and continuous, that the mass of the habitation module is evenly distributed, and that there are four footpads, each with a diameter of 0.5 m. The formula for this bearing capacity is given in the United States Navy's Foundation and Earth Structures Design manual [109] using the formula for a circular footing. Physical properties of the soil types are taken from USGS studies of the Viking Lander missions [4].

The bearing capacity of "drift material" is ~61 kPa, of "blocky material" is 446 kPa, and of "crusty-to-cloddy material" is 303 kPa. With the estimated bearing force applied by each leg of the habitat module at 86 kPa, only the blocky and crusty-to-cloddy soils will yield a stable base for the surface habitat. Figures 6.7A and 6.7B show the placement and penetration of Viking I footpads into the Martian drift-type soil, emphasizing the importance of soil type for site selection. The drift material was the one soil found at both Viking sites, and is believed to be quite common on the Martian surface. It should be avoided as a foundation-bearing soil for all but the lightest of structures, and should probably be avoided by any vehicles used in transporting the heavier structures or cargoes on the Martian surface.

6.4.3.2 Lander Off-LoadingMost of the essential hardware for surface construction on Mars will need to be off-loaded from the landers. Some of the smaller equipment, such as the unpressurized rover, will be easy to off-load. However, off-loading the key components of surface construction, such as a nuclear power supply and the habitation modules, will be more difficult (Figure 6.8).

Two primary problems are present in off-loading. First, if a component is delicate, special care must be taken not to damage the object. Second, if a component is massive and bulky, special care must be taken to control the object safely while moving it. All the primary surface construction components fit into one of these two categories.


Delicate ComponentsThe most delicate components to be off-loaded are the photo-voltaic arrays (PVAs) and nuclear reactor power modules (Figure 6.9). The PVAs are deployed first to power the initial habitat until a nuclear power module can be brought on-line. The PVAs will serve as a back-up power source once the nuclear power module system is connected. The array will be set on the ground, unlike the initial PVA system for lunar bases, to minimize the effects of high winds. Special care must be taken during off-loading and deployment to avoid damaging the delicate photo-voltaic cells on the PVA. The PVA system will need to be both unloaded and deployed, which may require a crane-type device and a deployment system.

Figure 6.8: Surface Payload Unloading and Deployment [110]

Figure 6.9: Power Module Nuclear Reactor (undeployed and deployed configurations) [105]

In its operational configuration, the power module reactor cores are deployed down from the main skirt into a pit in the ground for extra shielding. An object of this size would normally be easy to off-load; however, damage to any nuclear power module may delay or cancel the entire mission. The United States SP100 nuclear reactor power module concept employed high-temperature, liquid metal coolant loops; puncture of one loop could significantly degrade the output power of the module. For this reason, whatever equipment is used to off-load a power module should also move it and place it into the prepared pit. This equipment needs to be able to perform all of these tasks delicately. If the site has permafrost near the surface, consideration must be given to insulation to control melting and settling from the heat generated by the nuclear power module. Permafrost conditions may also impede digging the pit. For the SP100 power plant and for the PVA, the power cables will require trenching and cabling operations to reduce exposure to the Martian environment and to surface vehicles.

Bulky ComponentsThe bulky cargo components are the habitation and logistics modules, two of which also contain airlocks. These modules are similar to International Space Station (ISS) habitation modules, ~8 meters in length and 4.5 meters in diameter, weighing 17 t each. They make up the main living and working area of the First Mars Outpost.

6.4.3.3 Site PreparationThe Mars environment contains several challenges and obstacles for FMO construction. Effective site selection can reduce some of these obstacles and thus the complexity of the construction tasks. Soil characterization and preparation tasks will be necessary before and during the FMO construction.

Site and Soil CharacterizationThree types of operations will be performed to characterize the site and soil: surface study, sub-surface study and chemical analyses. To perform these tasks, specialized equipment will be required. To characterize the types of soils, their locations and depths, a rover-mounted or a robotic soil survey drill and sub-surface sounding system might be used. A decision must be made during the system development phase to allow input into the design process. Fulfillment of these requirements is best allocated to the precursor robotic missions.


The soil-survey core drill will provide the crew with soil samples. These samples can be classified in the same manner as the soil samples of the Viking landers (i.e., drifty, blocky, and crusty-to-cloddy materials). The location of various soil types relative to the base site can be identified. This soil-survey core drill could be mounted on a robotic module or it could be mounted on a human driven rover. One advantage to the robotic module is that it could be sent to the Martian surface and could perform its tasks before the crewed lander arrives. Using a rover to conduct these tasks would absorb the time of at least one crew member and the rover. This would slow down the rest of the construction operations during the crucial initial stages.

The sub-surface sounding system will be used to identify the depths of the different soil types. This system may be set up by the crew or it could be self-deploying. The information reviewed by this system will be very important; it will indirectly determine the amount of soil that must be excavated to support the base subsystems.

Regolith ShieldingAn integrated analysis of the total radiation dose for the Earth-Mars transit phases as well as the surface stay must be performed. The Mars atmosphere greatly reduces the radiation dose to the surface crews. However, the overall dosage limit may require that protection be provided while performing tasks on the surface. Regolith shielding is one relatively economical approach.

To minimize exposure to Galactic Cosmic Radiation (GCR), the sleeping habitat could be shielded. This will give ~8 hours per day of relief from GCR. Two types of shielding structures were considered. Figure 6.10 illustrates two examples of shielding structures. The first is the Canopy Structure. This structure uses a truss support to minimize mass and a graphite fiber mesh to support the regolith. An additional graphite fiber mesh cover will be required to eliminate the adverse effects of the Martian winds (i.e., erosion and blowing of drift material). The second choice is the use of regolith-filled bags. These bags would be draped over the habitat module. Although the structural mass is reduced by this approach, the EVA construction time and amount of equipment needed may be increased. (We note that if permafrost or subterranean water is found, later missions might develop indigenous mortar or cement for this purpose.)

Figure 6.10: Buried Structure and Shielding with Regolith Bags [105]

BermsAlong with regolith shielding, berms must be constructed. These berms will be used to protect the crew from nuclear power module radiation emission, to protect PVA from Martian winds, and will serve as regolith blast barriers for lander and ascent vehicles. The construction operations for creating the berms are very similar to habitat burying operations. Soil must be moved from its current position, and placed in another location. To protect the berms from erosion and blowing of the drift material, the berms can be covered with a graphite fiber mesh that is anchored to the surface.

6.4.3.4 Delivery/Emplacement of Habitation Modules and Power Sources Habitation module and nuclear reactor power module delivery and setup are critical to establishing a viable environment for the second FMO crew. For this reason the transportation equipment


choices, e.g., Martian crane and/or construction rovers, are assumed to be crew-supervised either directly or by teleoperation. The final choice of transportation and emplacement options will be made after early robotic site reconnaissance and will be highly dependent on the soil and terrain characteristics of the initial cargo lander site. The flexibility and redundancy provided the FMO crew by multiple solutions will act to increase safety margins and to maximize the probability of achieving a sustainable FMO.

6.4.3.5 Subsystem Operational TestingMost modules operating in the FMO architecture should contain self-diagnostic capability to insure proper function. However, it may be desirable for redundancy to be able to outfit micro-rovers to act as diagnostic test-sets in the event of unexplained system failure. Crew transport vehicles should also be equipped with diagnostic equipment in the event that remotely placed modules fail. A supply of spares must be included with the FMO cargo landers.

Periodic diagnostic testing is necessary for maintaining optimal base operation and safety. All construction systems should be either equipped with or reconfigurable for use as diagnostic test and repair platforms. This requirement will drive the research in the area of fault-tolerant systems, expert systems, and neural networks. The energy required to perform this testing must be constrained while at the same time maximizing the probability of detecting a degradation in a system before catastrophic failure.

6.4.3.6 Conclusions Regarding FMO Construction ChallengesLogistics Constraintsa. Launch WindowsThe logistics problem for the FMO is immense and dominates the construction activity. It will be necessary to carefully plan the HLLV launches and the orbital assembly of the Mars spacecraft, and to include various contingency capabilities, so that the assembly can be accomplished with high probability within one of the 26 month Earth-Mars launch windows.

b. Abort/Contingency Scenarios Failures in both crew and cargo systems over the course of multiple missions must be anticipated and must be mitigated with contingency plans to avoid the loss of life or mission. This will involve the evolution of mission rules that span the entire construction and delivery sequence, similar to those used today in human space flight.

c. Interruptability Models have been developed for accommodating interruptions such as meteoroid/ debris damage, astronaut illness, launch failure, etc., in the assembly of the Space Station Freedom design [111]. The methodology developed could be adapted to assessing the interruptability of Mars base construction or assembly of the interplanetary Earth-Mars spacecraft in Earth orbit. Because of the 26 month "windows," scenarios must be developed which will make the mission plan robust with respect to the various types of possible interruptions.

Base Construction Considerations: a. Construction and Activity Windows / Base Pre-Deployment AlternativesOnce the first crew of astronauts has landed, they will have a limited time in which to complete their construction activities. During the first few days of this period, certain mission-critical tasks must be accomplished, such as the setup and activation of the photovoltaic power supply and the activation of the habitation module. If these tasks are not accomplished within the prescribed period of time,


the life support limitation of the ascent lander will be reached and the astronauts will be forced to ascend to the orbiting Mars Transfer Vehicle to survive. These constraints require that the times and reliabilities of construction activities be well understood so that the practical feasibility of any construction plan may be evaluated. Because of such critical timing it may be required that the Base and the critical life support functions be robotically emplaced and verified prior to crew departure from Earth.

b. Martian Wind Storms Mars Base construction and design must take into account the excessive wind storms that have been observed on the Martian surface. Wind storms have been observed at up to 130 km/hr. While the forces produced by such a wind equate to those felt at ~10 km/hr at sea-level on Earth, due to atmospheric pressure differences, these winds could be hazardous to both the PVA arrays and to the thermal radiators attached to the nuclear power modules. There is also the potential for erosion damage due to wind-borne dust particles. Contingency plans for these storms must be considered in construction planning. Appropriate design of equipment exposed to these dust storms will lessen the damage.

c. Multi-Use Planetary Surface Construction EquipmentA multi-purpose vehicle will be required to prepare a roadway between the area for Mars descent vehicle landing and the construction site of the habitat. This vehicle might also be used as a bulldozer and as a tug, pulling the habitat module into place. Additional requirements have been identified for the emplacement of the power modules. The nuclear power modules require site preparation, digging and the building of berms around the reactor. All of these requirements point to the development of a multi-purpose vehicle or rover. Thus, a construction vehicle should be designed that can be used as a rover, tug, trencher, back-hoe, and crane (the "Swiss army knife" of Mars construction equipment).

d. Early FMO ConstructionThe construction tasks for the First Mars Outpost mission include various site preparation tasks such as site preparation for reactor PVA array deployment and habitat placement. It is possible that some of these tasks could be completed autonomously by robots before crew arrival.

e. Reusability/Recycle EngineeringAs the FMO cargo and crew delivery sequence progresses, a growing stockpile of used cargo landers and crew descent stages will develop. The philosophy of "reusability engineering" should be used in the design of FMO equipment, so that all material delivered to the surface is used to the maximum extent. An example of this is the possibility of designing the lander legs so that they are easily detachable and pre-designed to be used as roof trusses to support Mars regolith, radiation, and meteoroid shielding loads over the habitat modules.

f. Astronaut Dexterity and StrengthAfter a long trip to Mars (150+ days) in a micro-gravity environment, astronauts may not be physically capable of performing the various construction tasks on the surface of Mars. Moreover, the astronaut life support suit may further reduce dexterity and stamina. It may be necessary to provide either an acclimatization period or end-effectors and telerobots that can work with the humans to perform the construction tasks. If artificial gravity is utilized on the journey to Mars, the degradation in the physical capability of the crew may be minimized, but the effect of long-term cabin rotation on the body's vestibular system is not known [112,113]. This problem is being studied by NASA at several of its NASA Specialized Centers of Research and Training (NSCORTs).


Additional design work on robots and end effectors could be performed and tested at the First Lunar Outpost.

g. Repair and Maintenance-Provisioning of SparesJust as contingency situations must be planned for in the logistics phases of the missions, so must they be provided for in terms of equipment spares. Backup spares and maintenance training will be necessary to accommodate safe and efficient repairs. Designing for in situ repair is a relatively new philosophy in space exploration that must become the rule, and not the exception.

h. Precursor KnowledgeA great deal of additional knowledge of the Martian environment is necessary to produce a real plan for FMO construction. Information on the geographic location of permafrost and water on Mars, the engineering characteristics of the soil, the atmospheric wind patterns, etc., must be obtained. This information should be obtained from robotic precursor missions that include orbiters, landers, and soil penetrators.


Chapter 7HUMAN FACTORS AND PHYSIOLOGICAL ASPECTS

7.1 INTRODUCTION

Traveling in interplanetary space or inhabiting a foreign planet for long durations can subject the crew to debilitating, injurious and possibly fatal stresses. Some of these stresses are radiation, hypogravity, isolation/confinement, toxicity, and mission specific environmental conditions. To be sure that the mission has a high probability of succeeding, it will be necessary to expand human knowledge of these stresses, their human effects over time, and remediation measures before undertaking such a flight. At the present time, upon return to Earth after long duration flights, Soviet cosmonauts have been unable to stand or walk and are routinely carried away on stretchers. Better physical condition will be required of astronauts upon landing on Mars.

The planning for the mission should also include consideration of crew selection and performance, habitability of the environments, sociological issues, life support, environmental health, and management of crises and illnesses. The accepted level of risk needs to be decided. We must realize that, inherently, risk cannot be totally eliminated and should not be denied; missions should be designed with prudent levels of risk (possibly 3% risk of catastrophe). The best way to manage the levels of risk for a mission is to understand the environment and the conditions of that mission, how a human will be affected by and will perform in that environment, and the mitigating benefits of possible control measures.

7.2 ISSUES AND APPROACHES

7.2.1 RadiationEn route to Mars, the flight crew will be subjected to Galactic Cosmic Radiation (GCR) and to solar radiation, including high intensity radiation associated with solar flares and other solar phenomena. It is not known precisely what the radiation fluxes from the GCR will be or what the interaction with spacecraft shielding will be, and it is especially difficult to say what the biological effects on the crew will be. Sub-lethal doses might have unknown physiological and behavioral effects on the crew. It is known that GCR is enormously energetic and very difficult to shield against. One percent of GCR is heavy charged particles, atomic nuclei (mostly carbon, oxygen, and iron nuclei) which are likely to produce vastly more than one percent of the biological damage.

The heavy charged particles are known as High Z and Energy (HZE) particles. Of these, iron is considered to be the most important biologically because of its relatively high abundance and the characteristics of the particle track, especially the large quantities of energy deposited per unit path length in tissue, the so-called linear energy transfer (LET). The risk of cancer, genetic effects and damage to tissues is greater with high-LET radiations than with low-LET radiations, such as gamma rays. In other words, high-LET radiations have a high radiobiological effectiveness (RBE). The RBE of the various components of the galactic cosmic rays in humans is not known. Single HZE particles can traverse a number of contiguous cells, unlike low-LET radiations, and the loss of contiguous cells might have effects different from the loss of the same number of cells separately located. It is not known whether the characteristics of the deposition of energy by HZE particles could result in late developing damage to tissues to a more marked degree, particularly in the brain, than would be predicted from the knowledge about the effects of low-LET radiation.


It has been suggested that crews en route to Mars would receive radiation to the blood-forming organs at the rate of 20 rem per year during solar maximum and at 49 rem per year during solar minimum, in a spacecraft with minimal shielding (~2 gram per square cm. aluminum equivalent). Tissue response to radiation is measured in rem; 1 rem = dose equivalent of effects of 200 KeV X-ray. The 20 rem and 49 rem values are rough estimates and need to be confirmed by future spacecraft flux measurements and by studies of radiation interactions with shielding. Extensive animal experimentation may be required to determine whether the exposure to the heavy atomic nuclei will produce unacceptable (and mission defeating) effects on the brain or nervous system, and not just longer-term genetic or cancer inducing effects, as now implicitly assumed.

Future robotic precursor missions should include instruments to provide additional interplanetary GCR data. German space flight research has indicated possible adverse synergy between radiation and microgravity in certain stages of development in a lower organism. Present research also includes examination of chromosomal level events. International radiation standards are evolving (NCRP - National Council on Radiation Protection and Measurement; BEIR - NSF Committee on Biological Effects of Ionizing Radiation), but are not yet in place. NASA radiation standards for interplanetary flights have not yet been determined.

It is known that GCR in the Solar System is less during a solar maximum (the active phase of the Sun's eleven-year cycle) than during a solar minimum (the quiescent phase). It has been suggested that crews en route to Mars would receive GCR at an unacceptably high rate if the flight took place during solar minimum, and that beneficial shielding would have to be enormously massive because of the high energy of the GCR. On the other hand, missions during solar maximum would be subject to solar storm generated Solar Particle Events (SPEs), associated with solar flares, necessitating the provision of an onboard storm shelter with considerable shielding.

Fortunately, the energy of SPE particles is much less than that of GCR particles, so that shielding is feasible. Shielding must be emplaced for all directions, not just for the direction of the Sun, and it would presumably consist partly of onboard water, food, waste, and equipment. Estimates for the amount of shielding required for anomalously large SPE, range from 10 to 70 gr. per sq. cm. aluminum equivalent. The correct thickness required needs to be determined. The possible use of active electromagnetic fields should also be investigated. Protection against SPE would be necessary also on the surface of Mars, but the requirement there would be much less because of the very effective shielding (16 gr. per sq. cm. aluminum equivalent) of the Martian atmosphere and the planetary mass underfoot.

The problem of providing adequate shielding is illustrated by the fact that while the equivalent dose for iron ions decreases with increasing thickness of shielding, the equivalent dose from protons increases. This is because of the secondary protons and the more biologically effective neutrons that are produced. It will also be necessary to establish with certainty that the solar maximum effect does in fact produce an acceptable level of GCR, as expected. It is worrisome that the higher energy cosmic rays are the ones least affected by the solar modulation.

To assess the magnitude of the biological effects resulting from exposure to different types of radiation, such as risk of cancer and damage to tissues, it is necessary to know not only the absorbed dose (energy deposited in tissue by radiation is expressed in Grays, Gy; 1 Gy = 100 rad = 1 Joule/kilogram), but also by what quality factor to weight the dose, based on the biological effectiveness of the specific radiation. Such a weighted-absorbed dose has been known as the "dose equivalent" but in the future will be called the equivalent dose (expressed in Sieverts, Sv; 1 Sv =


100 rem). The equivalent dose measurement yields a better correlation to effects such as cancer (typically, 1 rem Å 1.3 rad). The galactic cosmic-ray dose rate in deep space on a mission to Mars is about 0.14 Gy per year, but the equivalent dose rate is higher. For example, with 5-10 gr. per sq. cm. of Al shielding, the equivalent dose to the bone marrow could be greater than 0.3 Sv per year at solar minimum.

Radiation in sub-lethal doses causes lens opacities (cataracts), cancers, life shortening, and effects on offspring of people exposed to the radiation (genetic effects). It has been suggested that because of the genetic effects it is advantageous to select crew members, especially the female members of the crew, who are older than the usual reproductive age range.

Interestingly, older crew members will have shorter life expectancies, leaving less time for radiation exposure effects to manifest themselves, and hence may be less likely to develop cancer from radiation. This is part of the basis of NASA's much greater allowable radiation exposure limits for older people. Older crew members will also have a reduced likelihood of reproduction after exposure. Therefore, the amount of radiation shielding required on the spacecraft can be reduced (reducing the mass of the vehicle). But these advantages of an older crew composition need to be balanced with the issues of susceptibility to health problems, recovery ability, adaptability, life expectancy, task requirements, and skill availability over an isolated multi-year mission. Also to be considered is the desirability of people of child-bearing age for an eventual Mars settlement. There is the possibility that crew members exposed to radiation will have accelerated responses due to decreased immunological functioning in reduced gravity environments, and therefore, a decreased cancer defense system. Individuals with a high family incidence of cancer might be at increased risk. A significant amount of work is being performed and more will be needed to investigate these issues.

7.2.2 Space Habitat Environmental HealthContaminant and hazardous substance concentrations are potentially toxic threats in the recycling of breathable habitat atmospheres, water recycling systems, and solid waste handling and recycling systems in spacecraft and Mars bases. For example, thermodegradation of teflon wire insulation in spacecraft can release toxic gasses and ultrafine particles that are irritating and possibly life-threatening to habitat crews [114]. Water recycling systems that use iodine as the disinfectant may give rise to iodinated byproducts (IDPs) which have potentially debilitating and long-term health effects [115]. Prolonged, low-level exposure to toxicants has a potential to induce behavioral changes. Risk and mission success modeling, assessment of deterioration of astronaut productivity, and threat to life or long-term health are being investigated to help in the selection of control and mitigation measures and risk-acceptable decision modes [112,116]. Later, at Mars, the intrusion of Mars surface and atmospheric materials into the habitats represents an unknown risk at this time.

7.2.3 Hypogravity Versus Artificial GravityThe hypogravity (reduced gravity) reactions that are of concern for a Mars mission of duration 1 to 3 years are: (a) cardiovascular deconditioning; (b) musculoskeletal changes; (c) neurological/vestibular system changes [113]; (d) blood/immune system changes [117]; and (e) fluid/hormonal changes. The reactions (a) to (e) are listed in order of decreasing (apparent) importance. For some of the reactions, known countermeasures are helpful, but (a) and (b) today remain as impediments for the Mars mission, unless artificial gravity may safely be used. More knowledge of these areas is needed before a weightless flight to Mars should be undertaken.


The effects of short-term weightless exposure are generally known and characterized. Specific long-duration effects are difficult to characterize at this time due to limited occurrence of such flights, but some insight has been gained. Table 7.1 summarizes the general findings. In the United States, NASA has funded NASA Specialized Centers of Research and Training (NSCORTs) at Universities (see Figure 7.1) which will help to establish bases of understanding of these problems and will train new researchers.

Solutions to the noted problems that would allow a safe weightless flight to Mars might require considerable research in spaceflight as part of Mir and International Space Station activities. The United States and Russia have used and will augment the facilities onboard Mir for advanced research into the effects of hypogravity on the human body. However, it is possible that the problems caused by hypogravity (except the vestibular problems) could be remedied by rotating the spacecraft to produce artificial gravity for the astronauts. Table 7.2 summarizes the magnitude and quantity of physiological/psychological problems encountered during weightless versus artificial-g missions.

The major physiological problems of concern would essentially disappear with artificial gravity (preferably 1-g at no more than 1 rpm). With the use of artificial gravity, the astronauts could be expected to walk off the spacecraft onto Mars' surface with confidence, and be able to walk immediately upon return to Earth's surface, as compared to being unable to walk at all immediately after a long-term hypogravity flight. Table 7.2 raises one more concern about the physical capability of crew to accept the Mars entry deceleration. Inability to handle high reentry stresses might lead to lander redesign and to much less cargo/payload efficient lander vehicles.

Figure 7.1: Centers Initiated by NASA to Investigate Life Science Space Flight Issues

The real issue is whether humans can adapt to Mars' 0.38 g after long-term micro-gravity exposure on the interplanetary space voyage, and can then readapt to micro-gravity on the journey back to Earth after an extended period on Mars. The human body may not fully recover all functionality in the Mars reduced gravity environment, and so the effect of additional micro-gravity exposure might be cumulative.

Preliminary studies have suggested that the rotation of the crew compartment on a long tether could produce 1-g at 1 rpm or less for an incremental cost of approximately 10% over the cost of launching a zero-g system. The length of the tether could be slowly varied during the flights to and from Mars, thus adapting the crew to the reduced Mars gravity before landing on Mars, and then readapting the crew to a 1-g environment while returning to Earth. This 1-g system would probably be cost-effective as well as safer for long duration flights. A 1-g system would also permit better growth of food plants en route. Rotation rates of 0.01 rpm or less are attainable for some spacecraft designs; it is questionable whether any vestibular or other effects on the crew would be detectable with such low rotation rates. However, for flights of short duration, the weightless environment is known to be acceptable. For flights of intermediate duration, it might be found that lesser magnitudes of "gravity," shorter rotation arms, and higher rotation rates (at lower cost) are acceptable. Also for flights of intermediate duration, it might be found that working or sleeping for a few hours per day in an onboard centrifuge within a non-rotating spacecraft could be used to


provide sufficient gravity exposure en route (the duration and magnitudes of gravity could be determined in pre-Mars spaceflight experiments).


Table 7.1: Potential Medical Consequences From Long-Duration Exposure To Space Flight Factors (adapted from [118])


INFLIGHT PROBLEMS POSTFLIGHT PROBLEMSMainly Zero-g EffectsMuscle Atrophy

CardiovascularDeconditioning

Bone Loss,Hypercalciuria

Fluid Shifts, Decreased Fluid Electrolyte Level

Decreased RedBlood Cell Mass(Decreased Blood/ Fluid Volume)

Neurological Effects

Combined Zero-G, Confinement Effects?Immune Changes

Isolation, Confinement, Remoteness EffectsPsychological/ Sociological

Space EnvironmentRadiation Exposure

Fatigue during EVA

Abnormal heart rhythms, loss of blood pressure

Increased potential for kidney stones

Facial fullness, feeling of head/sinus congestion

Possibility of more acute response to trauma, blood loss during injury, or hemorrhage

Space Motion Sickness(initially hours-days)

Clinical significance unknown but changes may represent a potential for increased susceptibility to infections, potential for contracting viruses, etc., from visiting crew members

Potential for decreased motivation and productivity, compromised crew / interpersonal relations and coordination, compromised crew/ground relations

Possible combined effects with 0-g on physiological systems, light flashes in eye observed, possible tissue damage depending on dose and type of radiation encountered

Fatigue, weakness, loss of strength, muscle/ligament pain, postural instability, loss of Òmuscle pumpÓ, orthostatic intolerance

Decreased exercise capacity, orthostatic intolerance

Increased potential for fractures, lengthy recovery of bone mass, possible irreversible bone loss

Orthostatic intolerance from decreased blood/fluid volume

ÒSpace anemiaÓ (restoration requires 4-6 weeks)

Postural instability/ disequilibrium Observations suggest severity proportional to mission length and countermeasure use

Clinical significance unknown but changes may represent a potential for increased susceptibility to infections, possibly a decreased ability to respond to immunological challenges inherent on Earth

?

Increased potential for cancer induction, cataract formation later in life


Table 7.2: Three Scenarios For A One-Way Trip To Mars: Severity Of Possible Biomedical Changes [118]

Bone mineral loss

Muscle atrophy

Decreased strength

Decreased body fluid and electrolyte levels

Decreased Red Blood Cell mass

Cardiovascular changes

Decreased postflight exercise capacity

Space motion sickness

Immunological changes

Postflight postural instability

New inflight motor learning required

Radiation Exposure*

Psychological/ sociological stress and challenge

ZERO GRAVITY

1-yr. weightless flight w/exercise

XX

XX?

X

X

X

XX?

XX?

X

XX?

XX?

X

XX

XX?

ADVANCED PROPULSION

weightless flight3-6 mo.

w/exercise

X

X

X

X

X

X

X

X

X

X

X

X

X

ARTIFICIAL GRAVITY

1-yr. artificial gravity with some level of exercise

X

?

(non-rotating vs.rotating s/c)

X

XX

XX?

Legend: X = changes will occur; XX = changes more pronounced;? = unknown changes; * = with solar flare shelter utilized

7.2.4 Isolation/ConfinementRussian scientists have reported that after thirty days of a spaceflight scheduled to last several months, a "thirty-day phenomenon" has been observed to occur. Although the information is anecdotal and should be interpreted with caution, the apparent phenomenon seems to manifest itself


as hostility between crew members and between the crew and the ground support team. The crew members also start to dislike being imprisoned in a small space and they start to react to the prolonged absence from home and loved ones. For example, on one Skylab mission, following some animosity between crew and ground, the crew requested and were granted a 24-hour period of unbroken radio silence, a period of no communication between ground crew and flight crew.

Ivanov [119] has reported the results of Russian psychophysiological testing of ten volunteers (31 - 37 yrs. old) in an antiorthostatic situation in a 370 day ground experiment. The psychological condition of the volunteers stabilized by 40 - 50 days; but by 100 - 150 days, the volunteers developed anxiety (hypochondria, vulnerability, propensity for reflection, interpersonality conflicts). After 180 days, the volunteers displayed secretiveness, increased tiredness, and unwillingness to subject self to any dangers or risk. Excitability was observed in the volunteers during 180 - 330 days of the experiment.

After approximately four to six months in space at hypogravity, crews also become "fatigued" and their productivity and work effectiveness decrease. Nechaev, et al. [120] reports that, "In flights with duration 4 and more months (unstable compensatory period) the tendency to development of phenomena of cumulative fatigue and asthenization of cosmonauts (weariness, emotional liability, sleep changes, etc.) was noticed." This fatigue and the "thirty-day phenomenon," presumably the results of the long duration isolation and confinement, are judged to be the most serious potential impediments to a successful Mars mission, according to some Russian authorities. Obviously a certain minimum level of psychological fitness in the crew is necessary for mission success. Before launching the Mars mission it will be necessary to be confident that the selected (and trained) crew, who will be isolated and confined together in a small "can" for one to three years, will maintain at least that minimum fitness and stability.

To maintain morale and productivity on long spaceflights, Russian psychologists have provided well-planned work/rest cycles and emotional "unwinding" periods. Especially effective are two-way television conversations between cosmonauts and their families, scientists, entertainers, and ground controllers. But exchanges of this kind will be much degraded during the Mars mission because of the time delays in transmission over great distances, delays of up to 40 minutes. Many of the measures taken to maintain psychological fitness during the long duration Russian flights in Earth orbit will be unavailable on the Mars mission. Therefore, other morale and psychological support measures need to be devised, some electronically based and some originating autonomously. Because of the many kinds of support that married couples give to each other, it is reasonable to expect that such couples (couples without dependent children) may make up the crew of the Mars mission, with the expectation that the psychological and sociological problems will be much reduced.

7.2.5 Crew PerformanceHypogravity and isolation/confinement with their sequelae over time, could significantly impact crew performance during the Mars mission, as they have during orbital missions. Previous long-term Earth orbital missions have not required significant crew performance after landing, whereas Mars mission crew performance will be critical after the prolonged period of flight and just after the landing. It is after the landing that the major goals of the mission, exploration of Mars and construction of a Mars base, must be achieved by the crew. The crew must also manage the landing and the subsequent launch, on unprepared terrain, without the help of ground crews. The specific worries concerning the crew on arrival on the surface of Mars are that they might be unable to maintain blood pressure upon standing up (and therefore faint), and that they might initially be


unable to walk without falling over because of vestibular changes. For reasons of safety, a period of Mars adjustment time might be needed before the crew undertakes significant surface activity such as driving a Mars rover vehicle or the operating of cranes and other massive or dangerous equipment.

The steps taken to deal with hypogravity and isolation/confinement will, hopefully, prevent these phenomena from exerting any disastrous influence on crew performance. Other issues that will influence crew performance are habitability of the landed module and environment, life support systems, management of crises and illnesses, crew selection, and sociological issues.

7.2.6 Life Support Systems and Medical/Dental Care in Space HabitatsManaging life support systems, medical, dental and health issues is a necessary precondition for achieving high levels of space crew productivity. Air, water and food life support systems are still under development for the longer duration space missions. Some systems will have to function in micro-gravity, some on Mars (0.38 g), and possibly some on the Moon (0.17g) in certain mission architectures. Standards must be established for designing, building, testing, operating, and maintaining such advanced systems.

Issues requiring further study also include medical/surgical/dental procedures in hypogravity, reduced gravity countermeasure procedures, variable cabin pressure adaptation, hyperbaric treatment impact on system and structure design, impact of pre- and post-EVA procedures, design of proposed medical facilities, and adaptation to changing human physiological responses in space. The tightly sealed environments of space habitats pose special air and water quality challenges which will require special monitoring and control systems, special material selection criteria, and unique operational procedures. A particular example is the development of control and mitigation techniques for Mars surface dust, which is expected to affect crew health (silicosis) and comfort, as well as hardware, particularly seals and mechanisms. Maintaining crew health will require trained personnel on site, access to the appropriate diagnostic equipment, medical refresher training materials, and systems that are capable of responding to emergency conditions such as fire, loss of pressure, injured or ill crew, and contamination events.

U.S. and Russian space mission medical experience and epidemiological studies of populations in analogous situations (Antarctica, undersea habitats, submarines, oil rigs, etc.) imply a high probability of medical problems occurring during long-term missions. The major issues for a Mars mission involve the incapacitation of a crew member that can result from radiation exposure, life support malfunction, illness, injury, kidney-stone events, or incidents of decompression sickness (bends). Medical and dental support systems must be able to provide preventive, diagnostic and therapeutic care for crew members during a Mars mission.

Appropriate medical/dental equipment for emergency situations and health maintenance, and a level of medical self-sufficiency must be provided. An autonomous level of medical self-sufficiency for Mars missions is essential because rapid rescue and return of an ill or injured crew member to Earth will not be possible. Given the communication time-lag associated with a Mars mission, the outcome of a medical emergency might depend upon the on-site capabilities, including the medical support equipment and skill of the crew. Access to a medical advisory structure on Earth might not be sufficiently timely. The use of an "expert system" with stored diagnostic knowledge and medical procedures seems likely, as well as the use of virtual reality training techniques.


The absorption and efficacy of certain drugs in fractional gravity must be known and incorporated into therapeutic procedures. Drug absorption is altered in zero-g and the possibility exists that it might also be altered in reduced gravity. Data on fractional-g drug absorption and appropriate drug dosages must be acquired, possibly from lunar base experiments, and that data must be used to plan the treatment of illness and trauma. Treatment will vary according to the body's adaptation level.

During extraterrestrial surface habitation, injuries, dental problems and trauma might require surgery. Therefore, surgical procedures in reduced gravity must be established. Ideally, the procedures could be perfected in the gravity field of the Moon and applied to the Mars scenario. If zero-g transit is chosen for a Mars mission, zero-g surgical techniques would be established from Mir and International Space Station studies.

7.2.7 Human-Machine InterfaceThe division of tasks between humans and robots needs to be understood and resolved to ensure mission success and to reduce operating burdens. Experience in the area of human-machine interfaces, simulation, system design and operations, human-in-the-loop simulation, and training systems will be essential to the optimization of workstation design. Effective utilization of innovative time saving and accurate training technologies such as AI-based astronaut support systems, telepresence, and virtual reality systems must also be employed.

Human factors engineering is essential to successful human space flight and exploration. Major challenges in this area related to a piloted mission to Mars include: 1) quantifying the capabilities and limitations of the human operator in progressively complex technological systems (such as a Mars transit vehicle, a Mars habitat, a controlled ecological life support system, and in situ resource utilization); 2) understanding the symbiotic human-machine relationships; and 3) developing predictive models for designing safe and productive human space flight systems/operations applicable to the Mars scenario.

Anthropometrics and biomechanics are crucial focal points that will need to be addressed to quantify human capabilities and physical limitations of the spacecraft configuration. For example, major changes to human anthropometry and biomechanics under zero-g space flight conditions have been documented. These include adoption of a somewhat "fetal" resting posture as the limbs settle toward equilibrium in the weightless condition. This postural change can adversely affect the ability to reach controls and to position the arm and hand accurately. Anthropometric/biomechanical changes for a Mars fractional gravity environment must also be assessed. Employment of computer modeling techniques, human lunar experimental and exploration data, etc., will be important contributors to these efforts.

During the pre-Mars design/development phase research must be performed on human strength and motion assessment related to tasks, crew procedures, vehicle subsystems, and crew equipment so that these aspects can be better paired with human performance capabilities. Measures of human strength and motion in the full spectrum of anticipated environments (1-g, fractional-g and zero-g) constitute an important area of research.

7.2.8 HabitabilityHabitability is a generic term which connotes the level of perceived environmental acceptability. Conditions considered to be "habitable" change enormously with circumstances and with duration of exposure to a given environment. The term also encompasses the quality standards to support the crew's health and well-being during duty and off-duty periods. The basic level of habitability deals


with the direct environment (atmosphere, temperature, noise, light, food, etc.) which influence primarily the human physical condition. During human Mars missions of extremely long duration, an extended level of habitability has to be taken into consideration (both for inflight and surface conditions) to maintain the individual's physical and mental/psychological health. Experience has shown that with the passage of time deleterious effects of isolation and confinement gain prominence.

It is assumed that when dealing with the constraints of the Mars missions, the individual human will have to adapt to a large extent to the environment. It is therefore necessary to anticipate the proper selection of interior space, decor, lighting, odor, noise, etc. Those aspects dealing with or related to life support functions (temperature, food, hygiene), are not considered here.

The interior space issue is directly linked to the level of gravity that is chosen for the spacecraft. In microgravity conditions, all sides and corners of a given volume are usable. With artificial gravity, attention must be given to the floor/ceiling relationship and to the fact that activities must be performed "as on Earth," which requires larger volumes (80 to 100 cubic meters of interior volume per crew member).

Decor and lighting have received little attention in spacecraft design in the past, but for extended spaceflights and for extended surface stays it is reasonable to think that the importance of these aspects will increase [121]. Measures will be taken to reduce sameness, such as movable partitions and removable wall covers, and astronauts will be involved at an early stage in the planning. Attention will also be given to the use of lighting to entrain circadian rhythms.

The problem of odors in spacecraft has been largely ignored, and in microgravity particulate matter does not settle out or clear away easily. Until now, space qualified materials have been tested for flammability and toxicity. Odors and particulate generation have not been given serious attention. Concerning the surface habitation on Mars, it was reported by Apollo lunar astronauts that the smell of soil brought inside can become annoying over time. The soil may even contain nanometer size particles which can become a respiratory irritant with possible lethal implications [122,123,124]. In situ resource utilization and the materials used for surface infrastructure may further complicate the picture. As in earlier spaceflight missions, careful toxicological studies of possible habitat contaminants will be required.

The annoying effects of noise on perception and performance, adaptation effects, and fatigue, as well as individual sensitivity to noise, make this parameter a prominent one. The objective will not be simply to eliminate all sound, but rather to control unwanted noise.

Another habitability concern is the need for privacy. There should be a balance between forces to affiliate and forces to withdraw, but of course it is impossible to completely withdraw from the mission and crew, once committed. For the sociological and psychological benefits, it may be that married couples will make up the crew of a lengthy Mars mission, and sufficient privacy for sexual functions will in that case be a requirement. In addressing privacy issues it is important to appreciate the entire situation in which the crew members will have to function. Privacy needs can be partly met through such things as personal possessions, private space, individualistic clothing, architectural arrangements, or increased levels of personal communication. Two additional promising ways to address the privacy issue in spaceflight (i.e., to reduce the environmental stress of space) are to match the individual with the environment (the person-environment fit), and to train the individual to deal with the particular stressors of the anticipated environment.


7.2.9 Selection of Compatible Flight and Ground CrewsThe psychological functioning and well being of each individual crew member, as well as her/his performance and the overall morale of the crew as a whole, depend in part on the individuals' relationships with one another. Clearly, interpersonal and group variables are critical parameters in the successful completion of the human mission to Mars. Such a mission will require increasing levels of cooperation among crew members for longer times, and crew selection will have to emphasize not only effective individuals but also effectively cooperative individuals, individuals who can form effective groups. The selection problem will be not be so much to find people with the appropriate behaviors as to find people whose behaviors interact in a productive way.

The Soviet experience with long duration spaceflight is instructive, as is experience in analogous exploration situations. In polar research stations there have been many instances of conflicts, including physical aggression. In strategic nuclear submarines there are higher than average instances of hostility, depression, and anxiety, as manifested in cliques, physical conflict, and the development of pecking orders. Social compatibility seems to be the pivotal determinant of morale and performance. Parameters that influence social compatibility are: gender, age, international and cultural differences, group size, personal attractiveness, competence, cooperativeness, social versatility, similarities and complementarities in skills and characters, and ability to achieve group homeostasis (synchronization of activities to achieve group results). Communication delays because of the long distances will have an important effect on the relations between the flight crew and the ground crew on Earth. Stored entertainment and periodic "news broadcasts" will be important.

7.2.10 Crew SizePicking the optimum crew size for a given Mars exploration scenario involves a trade-off between increasing the number of crew members at the cost of a heavier, more expensive transportation system versus the benefits of accomplishing more work in the same time and having a more robust system. Because it will be expensive to transport additional personnel to Mars, it is clear that each crew member should be capable of supporting several critical mission needs. A partial list of mission jobs might include: pilot, navigator, physician/dentist, electronic maintenance, mechanical maintenance, computer software maintenance, and life support systems maintenance. Other important specialist skills include mission commander, exobiologist, planetologist, and resource scientist. In addition, all crew members can be expected to participate in EVAs, drive the rovers, operate cameras and other instruments, drill core samples, set up science experiments, perform logistics functions, cook, clean, and communicate with ground control personnel.

Assuming that each crewman is trained in three specialist skill areas, and that a mission requires at least two crew trained in all critical skills and one crew member trained in each of the other important specialist skills, the mission requirements imply a minimum crew size of six. However, crew sizing and selection will also depend on group dynamics and cultural factors for the particular mission, vehicle, and habitat design concept selected, and various habitability factors, mission duration, workload, and perceived isolation. Extensive skill-training and cross-training are benefits of older flight crew members, who have had the opportunity to be trained in several areas in their lifetime. "Expert systems" and virtual reality training may be used to supplement deficiencies in training for required skill areas.

7.2.11 Management of CrisesA crisis can be defined as any situation that arises over a relatively short time and which could result in severe or even life-threatening consequences. Two kinds of crises can be described: crises from


physical events external to the crew (for example a radiation storm, a meteoroid impact, or equipment malfunction); and crises from internal psychosocial causes (severe psychological disturbance onboard) or from "medical" problems.

7.2.11.1 External crisesDanger is inherent to space travel. Space remains an extremely hostile and unforgiving environment. Associated with danger is the natural feeling of fear, a complex phenomenon that is part of the human response to certain situations. Optimal performance is achieved not by totally eliminating fear (an impossibility anyway) but by controlling the time and intensity of the fear experience. The obvious means to prepare for danger is training, either for specific or general situations. What is true for the individual is true for the group; that is, a crisis is accompanied by problems of crew coordination within a general state of group instability that is not unlike fear within an individual. The quality of leadership displayed during a crisis is therefore critical. Surprisingly, it appears that in most crises altruistic behavior becomes the norm. After a crisis is past, recovery of group homeostasis is important. Blaming someone for a group problem is a common human reaction, and such a reaction within the confines of a space vehicle could place an intolerable burden on an individual. If this individual is in a position of leadership, blaming could result in further group instability. Crew members must be trained to control fear and to deal with crises without resorting to mechanisms that themselves would threaten the community over the long term.

7.2.11.2 Internal crisesInternal crises might not seem critical compared to an external "physical" event, but they can be equally devastating to the whole mission and crew. Psychological disturbance can affect one or more of the following: thinking (schizophrenia), perception (paranoia), mood (mania or depression), and impulse (violent, or frozen/passive). The most common disturbance observed in situations similar to spaceflight is depression in which the affected individual suffers a diminution in relations with other people and with the outside world. The stress literature does not provide an immediate solution, but attention is given to the significance of events to the individual, the possible multiplier effect of the individual's personality, the effectiveness of the individual's coping patterns, and the support system available.

Prevention of psychological disturbance during a human Mars mission is primarily a matter of crew selection and training. It seems best to select mature, emotionally stable people who are able to perform the required tasks, to meet the stresses of life without personality disintegration, to interact without making others annoyed, and to adapt their perceptions to reality. Open, extroverted people would probably be especially helpful to the mission. However, selection will not necessarily eliminate all psychological illnesses during the mission. Onboard psychotherapy and psychotropic drugs might be required to overcome internal crises despite careful crew selection. The crew medical officer should be skilled in this area.

During the first Mars mission, people (crew) will for the first time in history "cut the umbilical cord" with Earth. The Earth will not be visible for most of the mission. The effect of this on the crew is unknown. Among jet pilots flying at night at high altitudes (without lights on the ground below), there sometimes occurs a phenomenon called "breakoff" which can give feelings of exalted powers, exhilaration, or in some cases fear. Awareness of being personally dissociated from Earth (and not subject to its laws) is another prominent part of the experience. This phenomenon has been compared to the nitrogen narcosis of the deep sea diver, and to the "call of the water" in which young sailors, apparently healthy, quietly slip into the sea. A similar feeling is reported by sky


divers. All of these phenomena have in common a resemblance to general sensory isolation effects that occur in stressful, confined, isolated environments. It is not known whether the prolonged and complete inability to see the Earth will cause the "breakoff" effect to occur.

Other areas of concern are the death, severe trauma, dismemberment or hyperbaric paralysis of a crew member. These would be extremely traumatic events for the surviving crew members, and their reactions would be complicated by the fact that an immediate return to Earth would not be possible because of gravitational, operational, and fuel constraints. Should the remains of a dead crew member be brought back home, left in space, or buried on the surface of Mars?

Whether related to the space environment or not, physical illnesses will no doubt occur during a two or three year mission with a possible crew of six people. Studies will have to be performed to provide adequate preparation for the most likely illnesses, preventing disease transmission and for mission alteration in case of incapacitation of a crew member. The most common debilitating health problem in some selected populations is toothache, and provision (training) for dental surgery should be provided to the flight surgeon. In fact, one crew member in addition to the flight surgeon should be trained to treat the most likely illnesses.

7.2.12 Extra-Vehicular Activity (EVA) and Extra-Habitat Activity (EHA)Uncontrolled exposure to large pressure differentials (between habitat, space suit, and the space environment), glare, temperature extremes, and dust conditions experienced by crew members during EVA and EHA affect crew performance and constitute serious health risks. Selection of habitat module and suit pressure differentials also determine prebreathe and postbreathe time requirements, which can have a significant impact on activity timelines. For example, the United States Skylab cabin pressure was kept at 345 hPa (5 psi) with a 70% O2 cabin atmosphere. This enabled EVAs to be made in a low-pressure suit (240 hPa / 3.5 psi) with no pre- and post-breathe requirements.

Other critical concerns include suit flexibility (especially the gloves), Extravehicular Maneuvering Unit (EMU) weight, and maintenance requirements. Mars missions which are expected to put an emphasis on exploration will require frequent EHAs. Consequently, EVA and EHA preparation, execution, and support tasks need to be fast, simple and reliable. Support systems must include adequate tools to support productive work in a difficult environment, and must include appropriate decontamination systems capable of quick and effective removal of Martian dust from the EMU. Figure 7.2 addresses some of these issues.

7.2.13 Planetary ProtectionMissions carrying humans to Mars will contaminate the planet. It is therefore critical that every effort be made to obtain evidence of past and/or present life on Mars before these missions occur. The degree of contamination will thus be minimized. The issues of forward and back contamination have legal, societal, and international implications that are serious and deserve attention and discussion [81,89]. International law requires that activities in space be conducted in such a way as to avoid harmful contamination of celestial bodies. Most spacefaring nations are signatories of the Treaty on Principles Governing the Activities of States in the Exploration and use of Outer Space, including the Moon and Other Celestial Bodies (U.N. Doc. A/RES/2222/(XXI), 1967), monitored by COSPAR, which sets planetary protection requirements.


Helmet

¥ Dust abrasion & accumulation limit visibility;¥ Restricted field of view limits safety & efficiency of EVA operations;¥ Internal displays & communication limits affect crew performance;¥ Glare and UV coatings important for performance and health/safety.

Portable Life Support System

¥ Major portion of allowable suit mass;¥ Pack size partly drives airlock dimensions;¥ Extensive consumables required for non-regenerative technologies;¥ Capacity limits EVA duration; possible umbilical interfaces to habitats & rovers.

Gloves

¥ Design affects fine motor tasks;¥ Pressure stiffening causes "grip" fatigue;¥ Prime candidate for prosthetic aids;¥ Most likely site for pressure breach.

Boots

¥ Flexibility affects mobility and balance;¥ Requires traction in terrain & regolith without excess particulate entrapment;¥ Stable materials for thermal range.

Suit

¥ Operating pressure affects risk, habitat pressure, pre- & post-EVA operations;¥ Joint flexibility & pressure mobility affect range and ease of motion, suit mass,

airlock design (ingress/egress ease) and EVA tasks;¥ Don/doff ease drives preparation & emergency timing;¥ Daily use requires resources (H2O, dry air, O2 purge, wipes, spare joints &

fittings) and regular, simple servicing;¥ Integrated dust control strategy: tools, suit, airlock, servicing facility.

Figure 7.2: EVA and EHA Spacesuit Issues


7.3 CONCLUSIONS

Human factors and physiological problems will probably not delay the human exploration of Mars, provided the quest for problem solutions begins now. The selection of the crew will be based on physiological, psychological, sociological, and task considerations, and cross training for stable relationships. A significant amount of preliminary work still needs to be performed in the areas of radiation, hypogravity, and isolation/confinement to understand the effects of these stresses.

¥ For long duration missions, a 1-g environment for the astronauts (preferably using a long tether and low rate of rotation) would eliminate the potentially mission-defeating effects of hypogravity. The incremental cost increase of providing such rotation has been estimated to be 5% to 15 %, variable according to the type of vehicle and whether aerobraking is used.

¥ Sufficient knowledge of the effects of prolonged Mars-level gravity should be acquired if a tethered 1-g or variable-g spacecraft system is used, and to deal with the reduced gravity on the surface of Mars. Some knowledge of zero-g effects is required for the contingency plan in case of failure of the tethered system.

¥ Sufficient knowledge of the effects of prolonged zero-g should be acquired if no artificial gravity system is used for the spacecraft.

¥ The biological effects of the radiation anticipated en route, on the surface of Mars, and in case of an abort flight, should be precisely determined. The timing, shielding, and countermeasures should be such that the hazard is acceptable and the effects should be mitigated as much as reasonably possible.

¥ The psychological effects of isolation and confinement should be reduced by the careful selection and training of crew members. The environments provided should be carefully designed for habitability, and crew activities should be carefully planned and provisioned.


Chapter 8MARS PROGRAM ORGANIZATION AND LEGAL ASPECTS

The International Exploration of Mars Program should reflect the premise that the Project will be an adventure benefiting all of humanity, and that it will welcome the participation of all nations and cultures. Strategies for designing the organization and its leadership body, task forces, committees, staff selection, funding, headquarters location, operations, standards, language protocol, and venues should reflect this premise.

However, it should be recognized that, while the International Exploration of Mars Program is an inspirational and a logical objective for many space professionals, it may not have high priority for other global citizens. In these times of deep economic, environmental and social concerns, some may consider it an unwise use of technical talent and money. Therefore, a primary task, especially during the organizational phase, should be the education of the public through the world media (print, radio, television, film, Internet) and through lectures to schools, civic groups, professional organizations, etc., on the economic, environmental, motivational, scientific, political and technological justification for exploring Mars.

8.1 EVOLUTIONARY APPROACH

The size, scope and duration of the missions required for the international exploration of Mars will require an evolution of organizations over a period of time. Several such organizations are discussed sequentially in this Chapter (i.e., IMEF, ICEM, and ISEI). This approach promotes harmony and cooperation by addressing the appropriate needs and requirements of all participants in each phase, from initial discussions to governmental agreements and then to program implementation. Although this process will take time and may introduce some additional complexity in order to gain the desired broad level of involvement, it should be recognized that several nations already have Mars exploration programs and plans underway which can be coordinated and perhaps combined. Ultimately, the goal is to converge on a program and implementing organization that best meets the overall objectives of the international participants, and gains the benefits identified in Chapter 3, "Why International?". In concurrence with the IAA International Exploration of Mars Subcommittee, other authors also recognize that, "any form of international cooperation would work best in a modular format, possibly with various nations sponsoring the development of the feeder technologies" [125].

8.2 INTERNATIONAL MARS EXPLORATION FORUM (IMEF)

The literature contains various suggestions for international agencies to implement Solar System Exploration [79]. It is suggested that initially a mixed public/private International Mars Exploration Forum (IMEF) be established to provide the focus for the organizational phase. There are recent successful, low cost, low overhead, examples of such international efforts. One is the Inter Agency Consultative Group (IACG) which was convened in the early 1980's by the science directors of ESA, IKI (Russia), ISAS (Japan) and NASA (United States) to coordinate their respective missions to study Halley's Comet in 1986. Coordinated scientific and operations planning enabled the participants to optimize the scientific return from each spacecraft and to share in the resulting measurements from all spacecraft.

As an open forum, the IMEF by itself would probably not be effective in coordinating or melding national plans or developing regulatory, technology-transfer, or trade policies. General space


policies could be negotiated in the United Nations Committee on the Peaceful Uses of Outer Space, while those specific to the Mars activities should be negotiated between the countries involved.

The IMEF's purposes would be to:¥ promote the concept of internationally cooperative space exploration;¥ motivate governments to participate in international Mars missions;¥ identify humanitarian, economic and technical benefits of Mars exploration which will

motivate governments to participate in international Mars missions;¥ educate professional groups, the public and the media on space exploration benefits;¥ identify opportunities to coordinate and, where feasible, to combine existing national Mars

exploration plans;¥ gather technical and scientific data relevant to international Mars missions;¥ make recommendations for further investigations;¥ propose technical plans that will provide a foundation for international Mars missions.

The IMEF would provide:¥ a clearinghouse of historically relevant information, data and reports on Mars exploration;¥ access to a Mars database and reports on the results of the investigations and

recommendations;¥ a report recommending the structure of a more permanent IMEF administrative

organization and the regulations and policies governing the venture;¥ a report recommending a program designed to stimulate international public support.

A similar low-cost organizational approach was taken by the world space agencies in 1988 to coordinate the 1992 International Space Year (ISY) activities. After adopting Mission to Planet Earth as a major theme for ISY, the agencies agreed to meet annually as a Space Agency Forum for ISY (SAFISY) to exchange information and to provide opportunities to expand the scope of research, educational progress and public outreach activities initially planned on a national basis, but with no explicit exploration focus. When SAFISY representatives met after the International Space Year (1992) was over, they removed ISY from the title of the organization, with the organization now called the Space Agency Forum (SAF). The Strategic Planning Committee met in Rome, with Italy as the host, April 22-23, 1993, with 30 agencies invited. They met again in Montreal, with Canada as host, on Nov. 8-9, 1993. Full members are space agencies or government agencies responsible for space-based assets and funding of space research and development. New affiliate members can be from nations with plans for future space activities. Other groups, professional international organizations, may be invited but will not have membership status. As of 1993, SAF included 33 agencies, representing 30 countries, ESA, and Eumetsat [126].

On May 10, 1993, representatives of many space agencies met in Wiesbaden, Germany to express unanimous support for the Russian Mars 96 mission, for extending exploration beyond 1996 for the U.S. Mars Observer Mission, and for making a new start for the Mars Environmental Survey Pathfinder mission in 1994. This group called itself the International Mars Exploration Working Group (IMEWG) and they agreed on a charter with 3 points:

1. Produce an international strategy for the exploration of Mars beyond the current approved missions;

2. Provide a forum for the coordination of future Mars exploration missions;3. Examine the possibilities of an international Mars Network Mission as the next step

beyond the 1996 opportunity.


Each space agency designated 3 members by June 30, 1993. IMEWG rotates the chairmanship every 2 years. The next meeting was at the IAF 44th World Space Congress in Graz, Austria, in 1993, and the first recommendation was presented to COSPAR in 1994. The resolution was signed by representatives of ESA, Russian Space Research Institute, Centre National d'Etudes Spatiales, the Italian Space Agency, the German Space Agency, and NASA.

These examples show that less formal cooperation, minimizing bureaucratic, legal, political, and diplomatic complexities can work efficiently. It is suggested that the administrative structure of the IMEF be minimal. Public and private entities in all nations having contributory space capabilities should be invited to participate. Although the above discussion emphasizes the exploration of Mars, the IMEF concept could readily encompass all international space exploration beyond low Earth orbit.

It is recommended that the initial leadership of the IMEF be chosen from among the members of the IAA. The IAA itself, as well as the member societies of the IAA's parent organization, the International Astronautical Federation, might be considered a resource base for selection of expert participants in the work of the IMEF's task forces, once it is established. The IAA should initiate the IMEF in collaboration with the world's space agencies, universities, industry associations and professional societies. The support of relevant political authorities and the participation of international organizations relevant to Mars exploration (such as COSPAR and the UN Committee on the Peaceful Uses of Outer Space) should be sought at the appropriate time.

It is expressly hoped that the IMEF will be effective in promoting the coordination, and where feasible, the melding of national Mars exploration plans. The Forum (IMEF) will work with governments to develop regulatory, technology transfer, and trade policies that will facilitate the achievement of the goal of international exploration of Mars.

Funds for administrative costs should be solicited from governments, foundations, firms, individuals, professional societies, space agencies, and other sources, from around the world.

The IMEF structure should be flexible enough to accommodate the objectives, concerns and/or the ambitions of the spacefaring nations, space users, industrial firms, universities, research organizations, and individual space scientists and engineers, while implementing its agenda.

Spacefaring nationsThis type of participant has sufficient financial resources such that its industry, training and educational system and social organization may allow a significant investment in space. Literature of the ANSER Center for International Space Cooperation (CIAC) refers to 47 space capable nations [53].

Space user participantsThis type of participant includes the governments of nations which may not have space agencies or the financial resources sufficient to organize industry at a level that allows the development of indigenous space technology.

Individual scientists and engineersThe inclusion of this type of participant is of fundamental importance because it demonstrates that the doors of the Forum are open to everyone.


One of the major tasks of the Forum will be to develop a modus operandi for cost-sharing and management responsibility in proportion to each Forum member's contribution of finances, hardware and/or human resources. While participating governments will likely provide the major funding for Mars exploration, formulas should be conceived which provide incentives for the private sector to make investments. A modest initial step that could later evolve into an IMEF was taken in May 1993 when space agency scientific planners joined together in the International Mars Exploration Working Group (IMEWG), the objectives of which were listed earlier.

8.3 EVOLUTION TO AN INTERNATIONAL COMMISSION FOR THEEXPLORATION OF MARS (ICEM)

After a period of time when a sufficient consensus has been developed to proceed with the human international Mars mission (or with more encompassing, complex robotic/precursor Mars missions), it will be necessary to evolve to a more formal organization. This organization might be called the International Commission for the Exploration of Mars (ICEM). This Commission would consist of representatives of each country that is interested in participating in the human Mars trip through substantive contribution of funds, hardware and/or personnel.

In this phase of the evolution of the Mars project, the key requirement is to establish the intergovernmental agreements and the operating organizational plans by which the project will proceed. The tasks in this phase include:

¥ laying the groundwork for intergovernmental agreements;¥ creation of a specific charter and organizational structure;¥ establishment of funding plans and protocols;¥ establishment of the official project language, technical standards, and legal standards;¥ negotiation of the choice of technologies; and¥ establishment of a technology transfer and spin-off policy.

As exemplified below, there are a number of examples of international organizations of significant size and experience that can serve as models for the organization of ICEM. The new organization may require features and characteristics of several of these, as well as the evolution and development of new organizational features. The most suitable organization can only be defined when much more is known about the specific program plans and participants. Following are several current organizational approaches and some of their key features, with considerations of the important criteria for an enduring implementation strategy.

The United Nations ModelThis model accommodates a very large number of member nations, utilizing a Security Council type of management and control with the senior and more powerful members having the veto power. This approach is likely to be too bureaucratic and the organization would have difficulty maintaining focus and control over a long term project that would frequently require quick operational decisions. Also, there is a danger that political confrontations and "statements" might interfere with program implementation. There may also be shortcomings in ensuring the financial guarantees of the participants to support the organization and the Mars initiative.

NATO Model


This probably provides good ideas and examples for participation by a limited number of members and a good structure for implementation of program command and direction. It needs strengthening, however, to embody timely, equitable procedures for the acquisition of equipment.

Antarctic Exploration ModelIn this case there are good examples for the international sharing of national plans and data, however, each party operates quite autonomously in terms of its own government funding and project objectives. There are also good examples of agreement on exploration and exploitation of territory and on environmental protection. The autonomy makes this organization work, but might prevent the ability to "run" procurement and operation of a complex Mars Program.

International Space Station (ISS) ModelAlthough this model is not without its critics, it does in fact represent the most ambitious international space project ever undertaken. It is governed by parallel intergovernmental and agency level agreements which address development, construction, assembly, operation and utilization phases of ISS. Technical consensus among partners is the governing principle, but the U.S., as lead partner with a 70% investment share, is able to make binding decisions in case of a deadlock. The original Space Station Freedom (SSF) model transitioned to the ISS model in 1993.

Intelsat and Inmarsat ModelsIntelsat and Inmarsat were set up as entirely new international organizations, with international governing bodies to develop and manage fully integrated worldwide communications systems. Substantial implementation authority was granted to these organizations by the member nations. Funds for program implementation are turned over to the management organizations by the participating national bodies.

ESA ModelThe European nations have developed the European Space Agency (ESA) for operating their multi-program space activities. The organization has stood the test of time, offering a satisfactory distribution of benefits and costs. Features include:

¥ rotating leadership among major contributor countries;¥ centralized program and technical management with participation from contributor nations;¥ multi-year funding commitments at the member nation delegate level;¥ competitive bidding to select contractors from participating nations;¥ assurance that each member nation's industries receive contracts approximately proportional to

the national contribution.

Citing slightly different opinions, it should be noted that other authors feel that, "The eventual coordination of the mission could be performed by an established international body such as the United Nations." [125]. Several organizational models were also recently analyzed at the International Space University during the summer of 1995. The design project Vision 2020 [127] took a proactive look at space activities for the next twenty-five years. Alternative models such as the British-French Chunnel development and the International Olympic Committee organizational models were reviewed. The emphasis in the project (a complete section is developed on global cooperation) was on commercialized cooperation. The idea of a dedicated World Space Agency was rejected by the Vision 2020 members as too bureaucratic and inefficient. The Vision 2020


team foresees the next twenty-five years as encompassing the space activities presented in Figure 8.1.

Figure 8.1: Space Activities Over The Next 25 Years [127][courtesy of International Space University]

Key considerations that rank high in defining the program implementing organization for the Mars Exploration Program will be the ability to deal with: a large worldwide membership and activities; a broad range of technical capabilities and work scope of the participating members; fully integrated and shared projects as well as separate but coordinated projects; and appropriate levels for decisions and direction of political, financial, legal/contractual, technical, programmatic/scheduling, external relations and human resources.

8.4 THE INTERNATIONAL SPACE EXPLORATION INSTITUTE (ISEI) [A POTENTIAL "THINK TANK" SUPPORT FOR THE ICEM]

The IAA is currently considering the establishment of a not-for-profit International Space Exploration Institute (ISEI), which, according to its advocates, would be an advisory agency, and a study institute to advance the exploration of the Solar System (see description in Appendix D). It would be able to perform contract work to ensure the international planning of international space missions. Perhaps such an IAA established Institute can be of direct assistance and can perform objective technical contract work for the ICEM or related organizations established for managing the International Exploration of Mars project.

8.5 LEGAL CONSIDERATIONS

There are no legal or treaty barriers to international Mars exploration. Multidisciplinary problems that can be expected to develop when exploring Mars will be subject to legal provisions of treaties formulated by nations since l967 to ensure that outer space and celestial bodies are used for peaceful purposes for the benefit of all humanity. International cooperation and national responsibility are expected to maintain conditions essential for preventing harmful influences, and for the conduct of safe, orderly operations (including the prevention of planetary contamination).

The sources of space law that are relevant to Mars exploration are:¥ international law in general, including international customary law;¥ treaties, conventions and agreements formulated within and outside the UN;¥ statutes of international space organizations outside the UN, e.g., Intelsat, Inmarsat, ESA, etc.;¥ space-related regulations of the UN specialized agencies, e.g., the International

Telecommunication Union, the World Meteorological Organization, etc.;¥ interpretations of UN resolutions, negotiating histories, expert analyses and the Vienna

Convention on the Law of Treaties; and¥ national space laws and their implementing regulations.

This last category involves the coordination and harmonization of national and international space laws.


Mars exploration will involve a variety of problems for mission preparation on Earth and for operations in outer space, and each undertaking could have a different set of legal aspects. All space activities, however, must comply with a set of basic policies adopted by many nations. Fundamental concepts ratified by 93 nations are in the l967 Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies. Explorations and usage are to be performed for the benefit of all countries without discrimination; states are required to encourage and facilitate international cooperation.

To avoid potential causes of war and conflict, there is a prohibition against "national appropriation by claim of sovereignty, by means of use or occupation or by any other means." Weapons of mass destruction are prohibited and "The Moon and other celestial bodies are to be used exclusively for peaceful purposes." Although military bases and maneuvers are forbidden on the Moon and Mars, military personnel may be used for scientific research and other peaceful purposes. Whenever advances in space science and technology create new situations, provisions of the l967 Outer Space Treaty have been expanded into new treaties providing for assistance and return of astronauts and space objects, liability for damage, and registration of objects launched into outer space.

As of Oct. 20, 1995, the so-called Moon Treaty, The Agreement Governing the Activities of States on the Moon and Other Celestial Bodies, offered by the United Nations to States for consideration in l979, has been ratified by only nine nations (Australia, Austria, Chile, Mexico, Morocco, Netherlands, Pakistan, Philippines, and Uruguay). France, Guatemala, India, Peru, and Romania have signed the Agreement, but have not ratified it as of that time. Of possible future relevance to Mars are the two controversial provisions in the Moon Treaty which prevented its broad acceptance: l) declaring the Moon and its natural resources to be "the common heritage of mankind"; and 2) proposing an international regime to phase-in benefits derived from those resources.

The Moon Agreement entered into force on July 11, 1984. Article 18 of the Moon Agreement states that 10 years after the entry into force of the Agreement, the question of its review should be included in the provisional agenda of the U.N. General Assembly so that the Assembly might consider, in light of past application of the Agreement, whether it required revision. Accordingly, the matter was raised at the thirty-seventh session of the Committee on the Peaceful Uses of Outer Space (COPUOS), held June 6 -16, 1994. Members felt that since the Agreement had been ratified by only nine States and signed by five others, any possible revision of the provisions of the Agreement should be conducted with prudence and only on the basis of consultations with all Member States. The Committee recommended that the General Assembly, at its forty-ninth session in 1994, in considering whether to revise the Agreement, should take no further action at that time. As a result, no action was taken to revise the Agreement. [128]

8.6 CONCLUSIONS

Plans for the exploration of Mars should be based on the assumption that space activities involve risks and that measures required for the protection of lives and property will necessarily require regulation. Implementation of general guiding principles should be based realistically on scientific and technical facts and attention should be given to developing national space laws to ensure that they are internally consistent within individual countries and are in harmony with international space laws.

Some attention should be given to treaty provisions governing the relation between the Moon and Mars because legal provisions for the Moon have been drawn in such a manner that they also apply


to Mars. In addition, a study should be initiated as to whether international agreements need to be made specifically for Mars because it differs so much from the Moon.


Chapter 9ECONOMIC AND RESOURCE CONSIDERATIONS

This report is not directed mainly at the aerospace engineer or the space scientist who may already be committed to space exploration. Rather it is intended for the informed citizen and the members of governing bodies of societal institutions who collectively decide on the expenditure and application of global resources. While perhaps intrigued and favorably disposed towards the advancement of knowledge about our Solar System and our galactic home, these readers will ask to know the costs and the benefits of Mars exploration. They must compare and justify the applications of resources to space exploration versus applying those same resources to the many problems of the planet - hunger, education, disease, pollution, etc. In the end, it is an informed and objective cost/benefit study that they desire.

9.1 COSTS

Foremost, it must be recognized that all space funds are spent on Earth; spent on the development and application of advanced technology. Much progress has been made in estimating the true cost of products in modern engineering and manufacturing companies in order to be competitive in their respective market niches. Many complex products in our societal infrastructure, including the building of skyscrapers, jumbo jet aircraft, and awe-inspiring bridges are bid "fixed price" against cost and schedule. With the increased ability to build cost element databases and the use of sophisticated cost methodology [129] major contracts are awarded based upon cost-benefit analyses. There are even formal techniques of "design to cost".

The major problem in applying these techniques to the estimating of Mars exploration costs is that a large part of the project remains in the R&D and "unknown" input realm. It is precisely in this area that Cost Estimating Relationships (CER's) are least reliable. In addition, Carl Sagan has observed,

I would like to stress that it is impossible to estimate costs before you have a mission design. And the mission design depends on such matters as the size of the crew; the extent to which you take mitigating steps against possible solar and cosmic radiation hazards, or zero gravity; and what risks you consider acceptable with the lives on board. Other relevant uncertainties are the amount of redundancy in equipment; the extent to which you want to use closed ecological systems or just depend on the food, water, and waste disposal facilities you've brought with you; the design of the roving vehicles for the Martian landscape; and what technology you carry to test the ability to live off the land for later voyages. Clearly, these issues powerfully affect cost, and until they are decided it is absurd to accept any figure for the cost of the program. On the other hand, it is equally clear that the program will be extremely expensive. [130]

One of the main cost uncertainties has been the availability of low-cost launch vehicles to deliver the Mars vehicle (possibly in segments) to Earth orbit and to provide Mars mission logistic support. The Augustine Committee [23] and the Space Synthesis Group under General Tom Stafford [24] both recognized the need for a large, low-cost launch vehicle to LEO, the latter recommending a 150 t to 240 t LEO delivery capability. The desired delivery cost is on the order of hundreds of U.S. dollars per lb. to orbit [131]. Table 9.1 shows that this cost level is not yet reachable by existing launch vehicles. According to a Stanford University space systems design study of an International Mars Mission, a fully reusable, "aircraft-like" launch vehicle (SIRIUS) can be developed for an estimated $4 billion and would achieve $1650/kg ($750/lb) to LEO, but its payload size would be


limited to 20,000 lbs [132]. The low payload size would constrain the size of Mars spacecraft segments deliverable to orbit. Such a vehicle has not yet been developed.

Various human Mars mission designs have been postulated and rough, order-of-magnitude costs have been estimated. An "off-the-shelf" technology plan for landing a crew on Mars has been developed by Prof. H.O. Ruppe [133]. The plan lands a crew on Mars 19 years after the initial start and includes a backup second mission landing, for a 30 year program. The cost in 1992 U.S. dollars was estimated at $170 billion, with an average annual cost burden of $6 billion and annual costs that vary between a minimum of $1 billion to a maximum of $13 billion. (In discussions with Prof. Ruppe, this was thought to be above the Japanese and European space budget levels, but that it might be accomplished by the United States alone.)

Table 9.1: Cost and Payload Size for Some Large Launch Systems

LaunchSystem

LaunchCost (1995 $)

Payload to LEO Cost per kg

ChineseLong March-2E $40 - 50 M 8,800 kg ~$5.1K / kgLong March-3B $60 - 70 M ~13,600 kg ~$4.8K / kg

EuropeanAriane 42L $75 - 85 M 7,400 kg ~$10.8K / kgAriane 44L $90 - 110 M 9,600 kg ~$10.4K / kg

Ariane 5 $120 M ~18,000 kg ~$6.7K / kgIndianGSLV ? ~5,000 kg ?

JapaneseH-2 $150 - 190 M 10,500 kg ~$16.2K / kg

Russian (CIS)Ikar-1 $6 - 10 M ~4,200 kg ~$1.9K / kgSoyuz $12 - 25 M 7,000 kg ~$2.6K / kgZenit $35 - 45 M 13,740 kg ~$2.9K / kg

Proton $50 - 70 M 20,900 kg ~$2.9K / kgEnergia ? ~88,000 kg ?

AmericanDelta II $45 - 50 M 5,089 kg ~$9.3K / kg

Atlas IIAS $95 - 105 M 8,640 kg ~$11.6K / kgTitan III $130 - 150 M 14,515 kg ~$9.6K / kgTitan IV ~$180 M* 17,700 kg ~$10.2K / kg*

Space Shuttle ~$270 M* 24,400 kg ~$11K / kg*[entries are obtained from [134], except * is approximated]

The 1991 Stanford/Soviet Mars expedition concept [135], on the low end of system costs, suggested a cost in the $70 - $80 billion dollar range. H.C. Mandell initially estimated the cost of a human Mars landing mission as 1/3 to 2/3 of the cost of the lunar landing; about $200 per capita (U.S.) versus the lunar landing cost of $325 per capita (U.S.) in 1981 dollars [136]. More recent analysis by H.C. Mandell indicates that a Mars Exploration Program consisting of three missions has a 90% probability of costing less than $110 billion, assuming no commonality with lunar missions and using new ways of doing business (cost does not include certain operations costs, facility costs,


science, or EVA costs) [137]. On the other hand, M. Collins has referred to costs ranging from $200 billion to $500 billion for the SEI program, though his Mars Exploration Program includes much more than a single human expedition to Mars [138].

9.2 AFFORDABILITY

In any case, these costs will be spread over many decades and, if the urging of this report is accepted, will be spread internationally. In this way the cost will be affordable to all participants. Figure 9.1 indicates the world funding levels deemed available for Mars Exploration, obtained from the International Space University Report written during the ISU Summer Session in 1991 [59].

Figure 9.1: World Funding Availability for the International Mars Mission [59][courtesy of International Space University]

In 1992, former NASA Administrator Thomas O. Paine concluded that, "the substantial economic, human, and technical resources required for the settlement of Mars in the 21st Century will be broadly available on an increasingly affluent Earth" [71]. The data he examined leading to this conclusion utilized a historical chart of the United States Real Economic Growth and similar historical data on real GNP growth per person in the technologically leading nations:

Comparing different eras and economies involves complex problems of concept and methodology, so results can be ambiguous. With this limitation in mind, [Table 9.2], from Pioneering the Space Frontier [National Commission on Space, 1986 [17]], summarizes two-centuries of U.S. population increase, industrialization and real per capita economic growth.

Table 9.2: U.S. Real Economic Growth 1800 to 1985 [Table I from Ref. [71]]

Mid-Year Population(1000's)

Total GDP(1985 $millions)

GDP per Person(1985 $)

1800 5297 4900 9231855 27386 48300 17621885 56658 156400 27611900 76094 277700 36501933 125579 517300 41201950 152271 1245700 81811965 194303 2157600 111041985 238631 3769400 15796

In the past 185 years, America's population has multiplied about 45 times, Gross Domestic Product about 770 times, and per capita Gross Domestic Product about 17 times. This experience is paralleled throughout the industrialized world.

In 1800 planet Earth's estimated total population was about 900 million people, 10 percent urbanized, producing a Gross World Product of about $350 billion, or $390 per capita (all monetary units are in 1985 U.S. dollars). Today's world population is estimated to be 5320 million people, about 40 percent urbanized, producing a GWP of about $20000


billion, or $3760 per capita (about the U.S. per capita output of 1900). In other words, the first 200 years of the Industrial Revolution saw the population of the world multiply about 6 times, Gross World Product about 57 times, and GWP per capita about 10 times.

This momentum appears likely to continue through the next 100 years, but with uneven progress in differently managed economies. In the 21st Century an increasing percentage of humanity will possess advanced technologies, growing capital resources, trained scientists and engineers, and future-oriented leaders. This combination will encourage many nations to participate in pioneering the space frontier.

Figure 9.2 provides a sense of historical perspective by depicting estimates of comparative real economic growth, in 1985 dollars and exchange rates, for 12 nations across the development spectrum in terms of Gross Domestic Product per capita. As the Figure shows, some countries, such as Germany, Japan, and Singapore, are achieving relatively rapid rates of economic growth, surpassing the per capita incomes of other countries with long histories of higher ranking positions. Virtually no one looks on such statistics as ends in themselves, but they do correlate with other social measures to indicate nations whose citizens enjoy greater opportunities and higher standards of living.

Figure 9.2: Real GNP Growth per Person (Figure I from Ref. [71])

Adjusting to technological change will bring many social problems as the broadening industrial revolution continues to transform our planet. Strengthened international trade and environmental institutions will be required to guide wise economic growth, but five fundamental factors suggest favorable prospects for international cooperation in the 21st Century:

¥ 45 years of Cold War ending without a nuclear Armageddon;¥ The prospect of declining military expenditures freeing capital to update the world's

industrial, agricultural, communication, and transportation infrastructure (without economic distortions due to superpower competition);

¥ Accelerating technical progress across a broad spectrum that will improve public health, education and spur further widespread productivity gains;

¥ Demonstrated rapid growth of national economies in well-managed, global-market-oriented nations; and

¥ Increasing capabilities of effective international organizations like Intelsat to bring nations together in challenging high-tech enterprises. [71]

9.3 COST IMPACT OF PROGRAM ORGANIZATION AND CONTRACT TYPE

Dr. Dietrich Koelle has furnished the following information from his TRANSCOST-Model [139] concerning the possible increase in costs when multiple nations or players are involved in a major program:

The organization principle for the development of a complex technical project is well known; it requires a clear-cut prime contractor/subcontractor relationship with well defined responsibilities. As simple as this well-proven rule is, so more surprising is the fact that often this rule is ignored in favor of several "parallel" contractors without a strong prime contractor, mainly for political or "prestige" reasons.


It can easily be proven how any other organization principle with several parallel contractors (or "co-contractor" principle) with coordination by the customer or an additional organization leads to a higher project cost. A more recent example for this type of project organization was the first phase of the US Space Station Program for many years, until it became evident that an industrial prime contractor is unavoidable. Sometimes the argument is raised that the subcontract overhead cost charged by the prime contractor could be saved by this type of organization, but this is self-deception since the additional cost will then show up on the customer side sometimes hidden in the general budget, but certainly not disappearing.

[Figure 9.3] shows the empirical model and the reference points for the project cost increase with the number of parallel organizations has been analyzed using empirical data. The resulting cost growth factor was determined to be,

f7 = n0.2 ,

with n = number of participating parallel organizations.

It is in fact not that bad as the sometimes mentioned Ãn - relation, and it does NOT refer to the number of companies or countries working jointly on a project. If they are organized strictly according to the prime/subcontractor principle, then no essential cost growth should occur.

Numerical examples for the derivation of the empirical factor f7 are, by example, the development of the ELDO (European Launcher Development Organization) launch vehicle program "Europa I/II" by 9 national organizations in parallel, and specifically the development of the third stage (ASTRIS) by an "Arbeitsgemeinschaft" (Working Group) of two companies. The TRANSCOST-Model would give cost of some 408 Mio.DM while the effective total cost were 484 Mio.DM. The cost growth factor was f7 = 1.19, including some other secondary effects. The author's [D. Koelle] participation in this project allowed the insight which is rarely available in other cases. The ELDO Program is also an example that the lack of a strong industrial prime contractor does not only increase cost but also ends as a failure.

Figure 9.3: Cost Growth Factor for Parallel Contractor Organizations(Figure 2-43 from Ref. [139])

Another numerical example for our empirical cost growth factor from the spacecraft area is the German AZUR Satellite Project with 6 companies working under parallel contracts from the customer organization. The "normal" cost comparable to other satellite projects at that time should have been some 41 Mio.DM while the effective cost was 60 Mio.DM or a cost growth factor of 1.46. [139]

9.4 BENEFITS


Fred Singer has made the case for attempting to formally identify the benefits of specific mission alternatives. One can rely in this case on "relative or incremental benefits".

Five levels of increasing complication (and therefore cost and time scale) can be identified for manned missions to the planet Mars: 1. Flyby; 2. Orbiting; 3. Equatorial orbit, with landing on Phobos and/or Deimos; 4. Landings on the planet surface; 5. Habitation. While this appears to be a logical sequence, it may be cost effective to skip one or more of the steps. In order to judge this, one needs an incremental cost-benefit analysis. The results depend very much on judgmental factors; yet the exercise may prove to be instructive for planning purposes and for identifying crucial technologies. [104]

Concerning the various lists of absolute reasons or benefits for sending humans to Mars, Carl Sagan agrees with the individual benefit items on the list in many (or even most) cases, but goes on to say:

When I run through such a list and try to add up the pros and cons, bearing in mind the other urgent demands on the federal budget, to me it all comes down to this question: Can the sum of a large number of individually inadequate justifications and some powerful but intangible justifications add up to an adequate justification?

I don't think any of the items on my list of purported justifications is demonstrably worth $500 billion, certainly not in the short term. On the other hand, every one of them is worth something and if I have 10 items or so and each one of them is worth $50 billion, maybe it adds up to $500 billion. If we can be clever about reducing costs and making true international partnership work, the justifications become more compelling. I don't know how to do this calculus, but it seems to me that this is the kind of issue we ought to be addressing. [130]

9.5 WHAT SHOULD WE DO? WHAT IS THE VERDICT?

In the face of inability to accurately and absolutely assess either costs or benefits, the decision for the future shifts more to the realm of an affordable "hedged bet" in the sense of Sagan's and Paine's views. Dan Goldin, the present Administrator of NASA, shares the view that we can reduce costs and spread the costs internationally. In his July 15, 1995 speech he said:

The bad news is our budget was cut. The good news is it's forcing us to do things differently. We're going to use new-think on our next piloted planetary mission. We'll be more efficient. We'll work with international partners, industry, government and academia. [34]

Hence, if we can reduce costs to an affordable level by being clever and using global resources via planning international Mars exploration, and we also enhance benefits [as identified in Chapter 3, "Why International?"), then the decision is clear - Mars is a Mission whose time has come.

As H.C. Mandell also points out concerning the U.S. GNP,

As a percentage of the gross national product of the United States, the total Apollo program represented 2.8% of a single year's GNP. Total Space Shuttle development represented only 1/2 of 1% of the annual GNP of the year 1977; a manned planetary landing in total would represent only approximately 1% of the GNP of the year 1990, as a maximum.


On a per capita basis, a manned planetary landing would cost from $87 to $149 (1981 dollars); the Apollo program, on the other hand, cost $325 for every person in the United States. The manned planetary landing should therefore represent less than 1/2 of the individual investment for each American than did the lunar landing (see Figure 6A [not included]).

Because of the significance of annual costs, the peak year funding of planetary landing was compared with those of the Apollo and the Space Shuttle [Figure 9.4]. It is seen that at its peak the program would require only 1/2 of 1% to about 1% of the national

budget, or less than 1/2 of the annual commitment of the Apollo lunar landing. [136]

Other authors such as H. Ruppe evaluate the cost of a Mars exploration mission at $600/capita or about twice the cost of an Apollo mission, thereby requiring a larger portion of the annual GNP of the United States. It is fair to estimate a total mission cost as being $200/capita-$600/capita if such a mission was performed by the United States alone. This cost underlines the desirability of International joint venturing. Application of the principle set forth in the Augustine Report, i.e., to 'Go as you pay', rather than to 'Pay as you go', can assure that these expenditure levels are not exceeded [23].

Figure 9.4: Program Costs (Figure 6B from Ref. [136])

At the University of Colorado's 1981 Case for Mars Conference, Dr. "Buzz" Aldrin's remarks are also appropriate to the case at hand:

Dr. Aldrin reminded the conference participants of the great value of the exploration ethic and the role that human activity in exploration has. He noted that the main driving force behind a continued and vigorous manned exploratory program is the identification of the public with adventurers who undertake great deeds under the banner of America. If we wish to see not only a resurgence of public interest and support for space in general, then a renewal of extraplanetary human space exploration is essential. [140]

9.6 CONCLUSIONS

Humans will continue to go into orbit and the costs per unit mass delivered to orbit (in real terms) will decrease as technology increases. Ultimately, the Moon will be revisited and Mars will be explored by humans. We can enjoy the benefits of these great journeys of humanity in our time by following the above concepts and recommendations to decrease and control per capita space investment costs (making the journeys affordable), and by increasing the benefits (by going international) even if we do not know the absolute costs and the absolute benefits at this time. Such is always the case for great ventures of humanity.


Chapter 10CONCLUSIONS AND RECOMMENDATIONS

The world has changed dramatically since 1957 when the launch of Sputnik I inaugurated the Space Age. For those engaged in the exploration of space, the most fundamental difference is not technological, but rather political and economic. Historic (and expensive) achievements of space science and exploration have been supported over the past 35 years by the world political systems, often as part of the competition between the United States and the Soviet Union. Space programs of today are orphans of that defunct Space Race. Advocates of substantial support for national and international space programs must prepare new rationales. In the process, they must give careful thought to the role of space exploration in the emerging World Order.

Space programs can certainly be advertised as adding to scientific understanding, advancing the national technology base, and encouraging students to pursue science or engineering degrees. While these claims are valid, they are not unique to space exploration. Similar claims can be made by other competing Big Science projects such as the United States Superconducting Super Collider (now canceled), the European CERN supercollider, mapping the human genome, or measuring global climate change. Some argue that the "spinoffs" from the big science projects can be accomplished more efficiently and economically by direct investment in the desired social goals (although, in fact, such direct investments are seldom made).

After considering these questions, the IAA Mars Exploration Subcommittee concluded that international space exploration uniquely offers humanity access to an exciting frontier of new knowledge. Instead of a race between two space powers, it can now be a cooperative global race for global benefits. Discoveries on new worlds in new environments by robotic explorers add to our knowledge of the Solar System, but they also explore the possibilities for extension of human life beyond our fragile Earth. Subsequent visits by astronauts to these other worlds will provide real data on the feasibility of such dreams. We believe that demonstration of the reality or, conversely, of the impossibility of human habitation of other planets will have a profound influence on the ability to establish international controls for safeguarding our own planet in the 21st Century.

The planet Mars is the most natural objective for this grand exploration. Its geologic evolution has been similar to that of Earth in many ways. In its atmosphere and on its surface, we find water, carbon, and nitrogen - all required for the existence of life. Martian landforms include volcanoes and extensive channels, apparently formed by large amounts of flowing water. The ancient river beds imply that the Martian atmosphere once had temperatures and pressures not unlike Earth. Today, the atmospheric pressure on Mars is only one percent that of Earth, and temperatures are seldom higher than zero degrees Celsius. It is important to discover what events led to these bleak conditions, because the answer may have implications for changes on our own planet.

Travel to Mars is technically challenging, and operations on its surface are difficult. Therefore, a comprehensive program of Martian exploration should include both robotic and human missions. Robotic precursor missions and on-going robotic exploration will collect data both for basic science and for establishing human presence. A principal issue of programmatic strategy is the proper balance between automated and crewed missions. The IAA International Mars Exploration Subcommittee recommends a focused robotic precursor effort with an on-going effort of robotic missions to assist the emplacement of the human Mars outposts and to continue human scientific exploration.


In this report we presented a variety of alternative approaches to mission architectures but do not recommend any particular choice. Another good source of approaches to Mars Exploration has been published by the AIAA, "Mars: Past, Present and Future" [141,142] In general, human Mars mission profiles have long mission durations (~1000 days) with long stays at Mars (300 - 500 days), or shorter mission durations (~500 days) with much shorter staytimes (~30 days). Technical choices among these parameters will depend on available propulsion technology, on our understanding of human performance in space, and on our confidence in the maintainability and long-term reliability of space systems. The performance of the crew in a long duration mission profile is the major uncertainty and requires focused research on human physiology and behavior in the space environment. In some mission scenarios, propellant for the return voyage is produced on Mars. Obviously, reliability and maintainability are paramount here. No technical "show-stopper" seems to make a human expedition to Mars impossible in the initial decades of the 21st Century if the pertinent research is begun now. The human Mars mission will require either a heavy lift launch vehicle (HLLV, ~240 t to LEO), or a low cost payload delivery launch system used in conjunction with safe, efficient orbital assembly technology. Some authorities believe that, with some modifications, present launch systems might be adequate for enabling a Mars mission (see Addendum II). The adaptation or growth of present launch systems, the development of new heavy lift launch vehicles or smaller and more efficient launch vehicles, and the development of space construction techniques are technologies which, if used, may "pace" the progress of a Mars expedition, at least from a hardware standpoint.

The form of the Mars exploration program will be influenced by the nature of the organization created to implement it. In this work, we have argued strongly for an international effort. Although some current programs of Mars exploration are already international in character, we foresee a need to increase the level of cooperation and coordination for future human missions. From a practical point of view, solution of the many complex problems would be enhanced by the application of expertise from all the space agencies of the world. On the philosophical side, an endeavor designed to benefit all people might be less attractive if some parts of humanity were explicitly excluded from participation. A world which is being drawn together ever more closely by advances in communication and transportation needs consensus on the vision of a future accessible to all.

We are not the only organization which foresees the advancement of space exploration as being facilitated by international cooperation. The International Mars Exploration Working Group (IMEWG) is actively pursuing this goal, as mentioned previously. The Center for International Cooperation in Space at Stanford University is also investigating plans to use deactivated ICBM's and surplus rockets for inexpensive Mars exploration. The University of Colorado continues to sponsor the Case for Mars Conference series (the latest in the series was the Case for Mars VI Conference, July, 1996). Also, the AIAA International Activities Committee recently held Workshops in 1994 and 1995 on international space cooperation. At the Dec. 1994 Workshop, they came up with five recommendations:

First, the heads of state and the space agencies of spacefaring nations should continue to recognize that through the effective use of international cooperation, with collective use of technology and resources plus elimination of duplication, we will be able to implement and conduct more far-ranging space exploration initiatives than would be possible as individual nations.

Second, national governments and international public service organizations should take advantage of the emerging capabilities of global space systems services. International


regulatory organizations should enhance the public service utility of these services through increased and more efficient allocation of frequency spectra and orbital slot positions. Licensing for these limited assets should be tied to concessions that support world-wide public service efforts. Uniform technical standards must be developed to enhance the interoperability of these systems.

Third, the principal providers of military and civil space capabilities, should establish an international forum to investigate the feasibility of improved use of current and future space systems for peacekeeping operations. The United States and Russia, as primary providers, should take the initiative in this effort. Discussions should focus on requirements, how existing national and international space systems can be applied to satisfy these requirements, and mechanisms for near- and far-term cooperation.

Fourth, heads of space agencies should collectively review their respective space exploration agendas with a view toward identifying potential opportunities for coordination. Once identified, options should be studied for their implementation, taking into account the experience gained through existing international cooperative mechanisms.

Fifth, definitive steps should to be taken to establish a mechanism by which the international community can foster and promote beneficial projects of international cooperation in space. [143]

This report examined the many factors that affect the implementation of an International Mars Exploration Program, including human exploration. An International rather than a National Mars Exploration Program introduces complexities, but also provides resources. The International Mars Subcommittee believes that the benefits outweigh the additional costs and difficulties.

We have reviewed several models for conducting international space programs. All have advantages as well as shortcomings. We favor an approach that begins with informal, non-official consultations and conferences under the auspices of an International Mars Exploration Forum (IMEF) to establish the technical and political issues for an international cooperative exploration program. As consensus is achieved, at first informally, the Forum evolves in stages to a formal activity, the International Commission for the Exploration of Mars (ICEM), for achieving human presence on Mars. These recommendations are based on the successful experience with the Space Agency Forum (SAF) and are discussed in more detail in the report.

Financially, the sharing of costs among the nations of the world in a truly global effort will make the percentage of GNP required from each country affordable. This will be particularly relevant if the "go as you pay" philosophy of the Augustine Committee [23] rather than the traditional "pay as you go" philosophy is practiced. In this way the benefits available to all will not cost too much for any.

This document:¥ Reviews the rationale and technical basis for an International Mars Exploration Program

now;¥ Identifies the opportunities for a robotic precursor program to help implement a safe

human Mars mission;¥ Identifies human adaptation as the most uncertain issue remaining;¥ Recommends that the IAA should promote the International Mars Exploration Forum

(IMEF) now or that its equivalent be created now;


¥ Establishes a timetable for education, formal development of IMEF, and development of the Mars Program;

Experience gained in crewed stations in low Earth orbit or at bases on the lunar surface can be applied to Martian exploration. While there is some commonality of equipment for lunar exploration and that for Mars, many analysts feel that humanity cannot afford the cost of the Lunar Base Program simultaneously with a Mars Base Program. Both should be studied singlely and together, to identify possible synergistic effects. We recommend that formal consideration, perhaps in a later Moon/Mars joint Cosmic Study, be given by the IAA to the appropriate relationship among all such human initiatives on the space frontier. In the meanwhile, the best way to resolve all issues is to move ahead with the organization, planning and research for the cosmic adventure whose time has come: the human voyage to Mars.


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Addendum IUPDATE OF MARS EXPLORATION PROGRAMS - c1995

(Addendum to Chapter 4 - MARS AUTOMATED MISSIONS AND PRECURSORS)

Contributors: B. Clark (Ed.), R. Bourke, M. Marov, I. Nakatani, J. Runavot, D. Shirley

Table of ContentsI.1 STATUS OF MARS PRECURSOR MISSIONSI.2 NEW PROGRAM PLANS

I.2.1 The International Mars Exploration Working Group (IMEWG)I.3 SPECIFIC PROGRAMS

I.3.1 European Program I.3.2 Japanese Program I.3.3 Russian ProgramI.3.4 U.S. Program

REFERENCES

I.1 STATUS OF MARS PRECURSOR MISSIONS

Since the original 1993 Mars Cosmic Study Report Acta Astronautica [i], there have been two major setbacks in space programs for the robotic exploration of Mars. First, there was the failure of NASA's Mars Observer (M.O.) spacecraft at the time of its execution of the Mars Orbital Insertion event. Second, there was the delay of Russia's Mars 94 mission. In spite of these reversals, most, if not all, of the planning agencies have expressed the sentiment that Mars is and should remain the highest priority target for planetary exploration. Moreover, there has been a restatement of commitment to Mars by the U.S., with establishment of a long-term plan for exploration [ii]. The Mars Surveyor Program (MSP) is the next robotic step in that direction [iii].

The loss of the M.O. spacecraft was investigated by at least three different groups, and the findings published. Although the cause could not be determined with certainty, the highest probability of failure involves the propulsion system. Leakage through valves may have allowed the accumulation of sufficient propellant that when the main valves were opened, a small explosion could have resulted, causing the spacecraft to become disoriented and lose the ability to re-establish the communications link. Even without the cause being determined unambiguously, there emerged from the investigation a series of "lessons learned". These lessons are currently being applied to the design of the propulsion system of all future planetary missions (including the Cassini and future Mars spacecraft propulsion systems). As the leading element in the MSP program, the U.S. has now implemented a project to recoup the science objectives of the M.O. mission. The Mars Global Surveyor (MGS) mission is discussed below under section I.3.4, the "U.S. Program".

The delay of the Russian Space Agency's Mars 94 has caused additional problems because of its impacts to the follow-on project, originally called Mars 96. The status and plans for these projects are discussed in the section I.3.3, the "Russian Program".

From these setbacks has arisen a series of extremely wide-ranging studies of modalities of Mars exploration, unprecedented in the history of the space program. Not only have the science objectives flourished because of what has been learned and what remains undone, but the methods of how they


could be accomplished now encompass a larger range of permutations. Opportunities abound because the several national space agencies each seek a role in Mars missions. This, combined with the advent of new and better approaches, particularly in computer and other electronics technologies, opens up many possibilities that previously could not have been seriously considered. For these reasons, there is no reliable methodology for predicting the course of future Mars exploration. This challenge has been taken up, however, in efforts by both international and national space agencies to plan efficient, long-range, and systematic programs to study and understand the red planet.

I.2 NEW PROGRAM PLANS

The original Russian Mars 94 mission, now Mars 96, and the U.S. Pathfinder mission will be launched in 1996, along with the Mars Global Surveyor. The Japanese Planet-B mission will be launched in 1998.

In mid-1995, NASA adopted a strategy for the exploration of Mars for the next ten years, encompassing Mars Pathfinder, MGS, and MSP. The intent is to launch two spacecraft at each launch opportunity from 1996 through 2005.

Concerning the Mars 98 mission, after the Russian decision to move from a Proton to a Molniya launcher, a study on "Mars-Together" was performed by NPO Lavochkin, IKI, NASA, and CNES. It consisted of a Molniya launch in 1998 of a Russian descent module carrying the French balloon and a planned U.S. Mars Surveyor Program orbiter. As of May 1995, movement toward a flight project has been postponed. Mars-Together is currently undergoing further study, but no firm plans for its implementation are approved. CNES has suspended activities on the balloon development for the time being. All efforts for Mars exploration are currently being coordinated with a new international organization, the IMEWG, set up to specifically address this goal.

I.2.1 The International Mars Exploration Working Group (IMEWG)The conceptual international strategy for robotic and human exploration of Mars is being developed by a new organization, the IMEWG, which now has representatives from eleven space agencies:

Table I.1: Members of IMEWG

Agenzia Spaziale Italiana (ASI)Austrian Space Agency (ASA)British National Space Centre (BNSC)Canadian Space Agency (CSA)Centre National d'Etudes Spatiales (CNES)Deutsche Agentur fŸr Raumfahrtangelegenheiten (DARA)European Space Agency (ESA)Finnish Meteorology InstituteInstitute for Space and Astronautical Sciences (ISAS)National Aeronautical and Space Administration (NASA)Russian Space Agency (RSA)

The charter of the IMEWG is as follows: ¥ Produce an international strategy for the exploration of Mars beyond the currently

approved missions;


¥ Provide a forum for the coordination of future Mars exploration missions; ¥ Examine the possibilities for an international Mars Network Mission.

The results of a study by IMEWG have recently been published [iv]. A specific plan for exploring Mars during the next decade is outlined. Unforeseen events are likely to affect the strategy and plan, so it is expected to evolve as funding and implementation practicalities are confronted.

The rationale for Mars exploration is not exclusively scientific because of the constraints of funding profiles, political issues, infrastructure discontinuities, and technology readiness. Nonetheless, the strategy for future exploration should have a sound scientific basis. The IMEWG scientific strategy is formulated within the context of what could be achieved during the next decade. Thus, although long-range, highly capable rovers and sample return missions have a high science priority, the science discussion focuses mainly on measurements that can be done with orbiters, balloons, small landers, and modest rovers, because only these types of missions appear practical and affordable during the next several years.

The mission scenario envisioned by the IMEWG is to launch probes to Mars at every launch opportunity from 1996 to 2003. The plan assumes multiple launches at each opportunity so that failure or delay of one element will not result in a total failure for the opportunity. The plan assumes that missions currently in their implementation phase will be launched as planned. The early missions are predominantly U.S. and Russian, so the scenario is strongly dependent on sustained funding for Mars exploration in both the U.S. and Russia.

I.3 SPECIFIC SPACE AGENCY MARS EXPLORATION PROGRAMS

Discussed below, in alphabetical order, is the current status of specific Mars missions planned by those space agencies currently pursuing Mars programs. I.3.1 European Programs

I.3.1.1 ESA Mars Program - INTERMARSNETThe INTERMARSNET mission was submitted to ESA in response to a call for new mission proposals for the next medium-size project (M3) issued in November 1992. It was submitted by the Director of Scientific Programmes in the framework of the new selection cycle of the Horizon 2000 long term plan. It is based on the previous MARSNET Phase-A Study submitted for the M2 selection in April 1993. INTERMARSNET is part of the IMEWG scenario. It is the only network mission to Mars currently being planned.

The INTERMARSNET mission consists of four small landers to be placed on the surface of Mars and a carrier spacecraft/data-relay orbiter. The small landers will define a regional/global network of stations to perform simultaneous geophysical and meteorological measurements and to investigate the local geology and geochemistry of the landing sites during the operational lifetime of the stations on Mars, i.e., one Martian year (687 days).

The current INTERMARSNET mission scenario includes a dedicated Ariane-5 launch in June 2003 into a direct interplanetary hyperbolic trajectory with a cruising time to Mars of about seven months. The landers will then descend to the Martian surface, three of them in the Tharsis region. The altitude of the data-relay orbiter in circular Martian orbit is planned for 4600 km and the orbital period will be about 5 hours. The INTERMARSNET mission is a joint ESA/NASA contribution to


the international exploration of Mars. In the current mission baseline, ESA would provide a carrier spacecraft/data-relay orbiter and an Ariane-5 dedicated launcher, while NASA would provide four probe/landers, with the potential participation of various European national space agencies. ESA and NASA are currently performing a joint INTERMARSNET Phase-A study together with Industry.

I.3.1.2 Other European National ProgramsAlthough no country-specific Mars missions are being planned, individual science investigators, funded by their national space agencies, have been selected for the Russian and U.S. Mars missions. These include, for example, French (Mars 96, MGS) and German investigations (Mars 96, Pathfinder). Other participation may occur on the Russian follow-on missions and the U.S. MSP missions.

I.3.2 Japanese ProgramThe ISAS (Institute of Space and Astronautical Science, Japan) is now in the process of developing the PLANET-B spacecraft that will orbit Mars. The launch is scheduled for 1998 using the M-V launch vehicle, which is also being developed by ISAS. It is believed that Mars has no magnetic field intense enough to deflect the solar wind before it interacts with the Martian upper atmosphere. PLANET-B will have an orbit with a periapsis of 150 km or lower where the magnetic field / solar wind interactions are most effectively studied. The atmosphere of Mars is characterized by the presence of dust. The onboard camera will provide information on the global atmospheric conditions near the surface.

One of the engineering challenges is that the dry weight of the spacecraft (without propellant) must be less than 258 kg, yet significant science objectives are intended. Hence, extremely lightweight components, both for bus and science instruments, are being developed. The spacecraft will stay in Mars orbit for at least one Martian year. Beginning in October 1999, it will gather data on the magnetic field, the vertical structure of the ionosphere, the energetic particles produced by the interaction with the solar wind, and it will collect images of the surface and dust storms. For this purpose 15 science observations will be onboard PLANET-B, as shown in Table I.2.

Table I.2: Scientific Observations to be Made by PLANET-B

Observation DescriptionMagnetic Field (MGF) 3-axes, 0.1 nT accuracyEnergetic Electrons (LSA) 5 eV - 22 keVEnergetic Ions (ISA) 10 eV - 20 keV/qEnergetic Ion Mass (IMI) 0.5 eV - 40 keV/qHigh Energy Particles (EIS) 40 - 500 keV (e, p, He, O)Thermal Ion Drift (TPA) 0.1 - 100 keV, drift velocityElectron Temperature (PET) Electron Temperature probeUV Spectra (UVS) H, O, CO, CO2 imagingSounder and HF Waves (PWS) Electron density profile, HF wavesPlasma Waves (LFA) VLF/ELF wavesVisible Camera (MIC) Visible imagingDust Counter (MDC) Particle counterEUV Spectrometer (XUV) He+ scannerNeutral Gas Mass Spectrometer (NMS) Neutral gas composition


Radio Science Radio occultation measurements

I.3.3 Russian ProgramSoon after the Space Exploration Initiative (SEI) was initiated in the U.S., at the time of writing the former IAA Report, the Russian programs that became the Mars 94 and Mars 96 missions were in planning [i]. They were referred to as an important milestone in the overall program of Mars unmanned precursors and robotic explorers of the planet.

In conjunction, several follow-on missions were studied and compared in terms of scientific advantages. These included: deployment of a network of small stations-penetrators on the Martian surface; sample return from Phobos to the Earth; and Mars rover operations on the Martian surface, with sample collection and sample return back to the Earth. These potential missions had at that time been proposed by the scientific community and were under consideration by the Russian Space Agency, although the missions had not received final approval.

The world political changes culminating in the economic upheaval in the countries of the former Soviet Union had a major impact on scientific institutions and industrial facilities, including those dealing with space. Tight budgets forced cutbacks in the space program. This strongly affected the original program of robotic missions to Mars. As a result, the Mars 94 mission was postponed to 1996. As far as the earlier planned Mars 96 mission (with balloon and rover) is concerned, it has been provisionally reconsidered for 1998, although there is no confidence at the moment that this early date of launch will be possible to implement. The work on the French balloon has been halted as of this writing.

The present Mars 96 project remains the first priority of the Russian Space Agency. Despite the funding difficulties, best efforts are being made to meet the 1996 launch window. The main difficulties are the availability of the three-axis pointing platform, Argus, carrying the German cameras and the French Omega Infrared spectro-imager and the ground tests for the small stations. Concerning the orbiter flight unit, the electrical integration of the flight instruments started in September 1995. The delivery to the Baikonour launch-pad was to take place in June 1996.

There are excellent technologies, launch and test facilities that remain operational, and intellectual resources in Russia to stimulate positive processes and to continue a basic government-funded space program, though with a strong commercial component. A good opportunity to promote cooperative updated space programs between Russia, USA, European countries, Canada, and Japan started recently with the agreement on the joint development and building of the International Space Station, (ISS), which has a potential to expand joint efforts for solar system exploration, with primary emphasis on the Moon and Mars.

Efforts are also underway to find lower-cost approaches to Mars exploration that would involve Russian and international joint efforts. An example of a low-cost mission of the future is the project of Meteorological Mars Observations with Microstations Network (Project MEMO MICRON) proposed jointly by the Mars Mission Research Center of North Carolina State University (USA) and the Keldysh Institute of Moscow (Russia). Its principal objectives are focused on the meteorology and dynamics of the Martian atmosphere. The basic idea is to deploy a network of 18 microstations on the Martian surface. The proposed mission would provide long-term monitoring and a reliable data base on the meteorology of Mars and could serve as a key element in the planning for future manned missions. The proposal for such a project has been submitted to NASA and to the TsNIIMASH and Babakin Center of Moscow. In particular, a plan to utilize deactivated


SS-18 intercontinental ballistic missiles to serve as the backbone of a faster, cheaper, and better approach to Mars exploration has been considered.

I.3.4 U.S. Program Pathfinder is the name given to the first new U.S. lander for Mars since the Viking missions. Although intended foremost as an engineering demonstration of new entry and landing technologies, this mission will also accomplish important new exploration. It includes a stereo camera with image resolution close to that of the Viking cameras, but with the capability to image up to 24 different bands, optimized not only for mineralogical features but also for the "sounding" of atmospheric dust and water vapor content. An exciting adjunct of this mission is the provision of a roving vehicle for a Mars mission, an 11 kg, six-wheeled microrover. The microrover, "Sojourner", carries a payload of dual cameras and an element analyzer (APX) which can be placed against rocks as well as soil samples. The microrover is capable of operating for some tens of meters from the spacecraft, relaying its data through a radio frequency link to the lander. Pathfinder will also conduct entry science to measure atmospheric properties at high altitude, and meteorological monitors for the landed mission. The landing site for Pathfinder is an outwash area in Chryse basin, not far from the Viking-1 landing site, which may provide a variety of rock types for investigation. The Pathfinder is designed for launch by a Delta rocket in 1996.

The MGS orbiter is currently under development and is also scheduled for launch by a Delta rocket in 1996. The primary purpose of MGS is to fly all but two of the original experiments flown on the M.O. spacecraft. Included are the Mars Observer Camera (MOC), the Mars Orbital Laser Altimeter (MOLA), the Thermal Emission Spectrometer (TES), a magnetometer and an electron reflectometer (MAG/ER), and the Mars Relay (MR). Outstanding new experiment capabilities should lead to many new discoveries about Mars, as well as documenting its surface features. The MOC will obtain very high resolution images at 1.4 meters per pixel. From the MOLA, with its altitude resolution of 1.5 meters, the current large kilometer-scale uncertainties in terrain elevations as well as larger errors in geodetic locations will be greatly reduced. These data will facilitate the selection of landing sites for future landing systems. Slope data can be correlated with the stratigraphic units that are identified from imagery to help determine their nature and the processes that have occurred since formation. The TES will map the Martian surface at 3 km resolution and should detect various mineral occurrences as well as obtain data related to the presence of dust, duricrusts, and rocks on a regional basis. The MAG/ER experiment will determine if Mars has an intrinsic magnetic field and may also detect the remnant magnetization of major crustal units. The MR, provided by the French CNES, is a UHF communications link which can receive up to 37 Megabits of data per typical pass (minimum of twice per sol) over landers, rovers, and balloons on the Martian surface. In the near future, the possibility of using the relay before or during the MGS aerobraking phase will be seriously studied for the collection of the descent data from the Russian Mars 96 small stations immediately after landing. The atmospheric data may be useful for adjustment of the aerobraking maneuvers.

The MGS instrument suite will allow major advances in defining Mars and could lead to one or more discoveries that further intensify the imperative to explore this sister planet.

I.3.4.1 U.S. Long-Range ProgramIn May 1995, NASA announced its strategy for the exploration of Mars for the next 10 years. The strategy is to study Mars in three areas: 1) Evidence of past or present life; 2) Climate (weather, processes and history); and 3) Resources (environment and utilization). Each of these areas is connected with the search for water on Mars. When and where was water present in the past, and


what is its current form and amount? We know from previous missions that the Martian polar caps include water ice as well as frozen carbon dioxide. The Viking and Mariner 9 orbiter images show evidence of past great floods (the Pathfinder is planning to land in such an area), and of dry rivers and lake beds. Where did all the water go?

If life ever did exist on Mars it would almost surely have been connected with water. Understanding the processes that led (or didn't lead!) to life on Mars will help us understand the potential for life elsewhere in the Universe. Water is a key to climate, both on Earth and Mars, and understanding the history of the Martian climate will help us better understand the Earth's climatic change processes. Water will be a major resource for future human exploration of Mars. If we understand how the solid Mars evolved (including what happened to produce water and then to make it disappear), we may be able to predict or find reservoirs of water available for human use on Mars.

Small orbiter missions would search for accessible water. We know that ice is accessible at the poles, but are there reserves underground or in the soil? The orbiters will search for ancient sediments and hydrothermal deposits (dry lake beds and geysers). They will provide data to understand the present Mars climate and study how water escapes from the atmosphere into space. The orbiters will also study the surface of Mars and identify important landing sites for the landers. They will also provide a radio link for relay of high volumes of data between the landers and the Earth.

Small lander missions would search for carbonates and evaporites, minerals that could only have formed in the presence of water. Landers can investigate water reserves in detail. For example, they can measure the amount of water that has been bonded to or incorporated into the soil. Or, they can drill into the polar ice caps to study the layers of snow and dust deposits that have been built up. Investigation of surface chemistry and how the rocks and soil have "weathered" due to water will tell us about the past climate. The landers may also be able to find organic compounds or even evidence that life may have been present at one time in Mars' past.

"Networks" of more than a dozen very small landers scattered over the planet could be used as weather stations to see how the Martian weather changes over the whole planet and the whole Martian year. If the networked landers have seismometers on board, and if they detect "Marsquakes", that information will tell us about what Mars is like deep inside, and how it might have evolved.

Next, sample return missions can bring back rocks and soil for analysis, using very sensitive Earth-based instruments too large to take to Mars. These analyses can tell us about the climatic history, the ages of different rocks, and may even allow us to detect compounds that could have led to life, or which are evidence of past life. (The odds of being able to select a rock with a fossil, however, are very low, even if fossils exist on Mars.)

I.3.4.2 U.S. "Strawman" Mission SetAll of these missions must be done within the very tight cost constraints (about $100M per year) of a new U.S. Mars exploration initiative called Mars Surveyor Program (MSP). NASA's Mars Science Working Group has laid out a "strawman" strategy for fitting the science goals into a set of MSP missions that can gradually build up our knowledge of Mars over the next 10 years, following the announced three themes of life, climate, and resources.


Following the Mars Global Surveyor (MGS) orbiter and the Pathfinder lander missions to be launched in 1996, an MSP orbiter and MSP lander (each half the size and cost of MGS and Pathfinder) will be launched in 1998. The orbiter will carry an atmospheric instrument, the Pressure Modulated Infrared Radiometer (PMIRR) from the M.O. mission, plus a small camera and a radio relay for the '98 lander. The lander will carry the first of a series of lander payloads specifically designed to carry out the "water strategy." The payloads may search for certain minerals that yield information on the history and existence of water, they may analyze rocks to tell the history of the climate, they may (if the lander is targeted to one of the poles) drill into polar ice. In years 2001 and 2003, there will be opportunities to send additional landers and orbiters that can continue to carry out the "water strategy" investigations.

Some of these landers could be targeted to ancient lake beds to search for evidence of past warm climates and possible signatures of extinct life. They could be sent to river valleys to investigate how water once flowed on Mars. The landers could include rovers and/or sampling arms to put instruments on the surface or to retrieve samples for analysis.

In 2003, the baseline NASA plan is to collaborate with ESA on INTERMARSNET, described above in the European program. And finally, the Mars Science Working Group recommends that the Mars Exploration Program attempt a Sample Return Mission in 2005.

I.3.4.3 An Augmented Mission SetExpanded opportunities for the "water strategy" could occur if teams are successfully formed among international partners. NASA and RSA are still exploring the possibilities of "Mars Together". In 2003 the European Space Agency (ESA) is proposing to send a joint ESA/U.S. mission to orbit Mars and land three or four of the standard U.S. landers, supported with a radio link on a European orbiter (see discussion of INTERMARSNET above).

More instruments, hence more and better science, can be provided if new technology improvements can be introduced into U.S. spacecraft to make them smaller, lighter, and cheaper. A program called "New Millennium" is currently being implemented to develop and demonstrate a new generation of space technologies to do this for both planetary and Earth missions. The Mars Exploration Program will be a "customer" for this new technology, and some of the New Millennium demonstrations may "piggyback" on Mars missions.

Technologies are also under development which will facilitate Mars sample return (MSR) missions. A number of scenarios are currently under consideration for reducing the costs of MSR.

In one, propellant for the return flight to Earth would actually be manufactured from resources available on the surface of Mars. This could reduce cost by reducing the size of the Mars-bound payload and its launch vehicle. Development and demonstration of chemical synthesis systems appropriate for this task are already underway and are giving promising results.

In another scenario, a low-cost, short-term lander would rendezvous with a previous lander or a rover to pick up a cache of selected, high priority samples. By only remaining a short time on the Martian surface (a few hours or days), the vehicle would not need the longer-lifetime engineering subsystems normally needed for a landed mission. This effectively splits the cost between previous exploration missions and one dedicated to sample return, but requires the development of a highly accurate landing subsystem.


Another approach to reduce costs to any one space agency would be to fully internationalize MSR so that two, three, or four major partners would provide specific portions of the infrastructure: launch vehicles, Mars-bound vehicles, lander, Mars Ascent Vehicle (MAV), Earth Return Vehicle (ERV), and the sample reentry capsule. This approach is particularly suited to the "classical" Mars Orbital Rendezvous (MOR) hand-off of a sample brought into Mars orbit by one or more MAV to a waiting ERV. The MOR method follows the Apollo staging strategy to save overall mass, but requires more hardware elements than direct return to Earth via a launch from the Martian surface.

The pursuit of Mars sample return missions is motivated by two factors. First and foremost, by the high scientific rewards of obtaining carefully documented selected samples for analyses in advanced, sophisticated laboratories around the world. Secondly, an MSR mission will demonstrate the technological feasibility and reliability of the round-trip aspects of Mars exploration, and will be a compelling precursor demonstration leading to human exploration missions to Mars.

REFERENCES

[i] IAA Subcommittee on the International Exploration of Mars, "International Exploration of Mars: A Mission Whose Time Has Come", Acta Astronautica , Vol. 31, Pergamon Press, Oct. 1993.

[ii] NASA, NASA Strategic Plan, NASA Aeronautics and Space Exploration Programs, Washington D.C., 1994.

[iii] A. Chicarro and S. Squyres, Together to Mars: An Initiative of the International Mars Exploration Working Group, ESA BR-105, B. Battrick (ed.), ESA Publications Division, The Netherlands, July, 1994.

[iv] IMEWG, Planetary and Space Sciences, 43(5):581-95, 1995.


Addendum IIMARS DIRECT: A PRACTICAL LOW-COST APPROACH

TO NEAR-TERM PILOTED MARS MISSIONS

(Addendum to Chapter 5 - ALTERNATIVES FOR HUMAN MARS EXPEDITIONS)

Robert M. Zubrin*

Table of ContentsII.1 ABSTRACTII.2 GETTING TO MARS WITH A LUNAR TRANSPORTATION SYSTEMII.3 MARS DIRECTII.4 MARS SEMI-DIRECTII.5 CHOICE OF TRAJECTORIESII.6 REQUIRED HLLV AND PROPULSION TECHNOLOGYII.7 A BASELINE DESIGN FOR MARS SEMI-DIRECTII.8 HABITATS AND CONSUMABLESII.9 SURFACE SYSTEMS ARCHITECTUREII.10 CONCLUSIONSREFERENCES

II.1 ABSTRACT

This paper investigates means for achieving human expeditions to Mars utilizing existing or near-term technology. Both mission plans described here, Mars Direct and Mars Semi-Direct, are accomplished with tandem direct launches of payloads to Mars using the upper stages of the Heavy Lift Launch Vehicle (HLLV) used to lift the payloads to orbit. No on-orbit assembly of large interplanetary spacecraft is required. In situ propellant production of CH4/O2 and H2O on the Martian surface is used to reduce return propellant and surface consumable requirements, and thus reduce total mission mass and cost. Chemical combustion powered ground vehicles are employed to afford the surface mission with the high degree of mobility required for an effective exploration program. Data are presented showing why medium-energy conjunction class trajectories are optimal for piloted missions, and mission analysis is given showing what technologies are optimal for each of the mission's primary maneuvers. The proposed surface systems payload manifest is presented, and mission back-up plans are described. An end-to-end design for the Semi-Direct mission using either the Russian Energia B or an augmented U.S. Saturn V launch vehicle is presented and options for further evolution of the point design are discussed. It is concluded that both the Mars Direct and the Mars Semi-Direct plans offer viable options for robust piloted Mars missions employing near-term technology.

II.2 GETTING TO MARS WITH A LUNAR TRANSPORTATION SYSTEM

Conventional plans for manned Mars missions involve multiple launches of HLLVs to support the assembly on-orbit of spacecraft with dimensions greater than the space station, and masses on the order of 700 tonnes. The majority of such craft will be composed of cryogenic propellants, which will continually boil off over the course of the year or so required for vehicle assembly. The

* Lockheed Martin, Denver, Colorado, USA.


technology challenges and huge costs associated with the launch, assembly, fueling, on-orbit operations and quality control of such missions have caused many to relegate the first manned Mars mission to some future generation that, perhaps, may live in a universe where such things are possible. The conclusion resulting from this paradigm has been fatal to the Space Exploration Initiative (SEI), as it has resulted in SEI being viewed as either a long-term unlimited expense Moon-Mars extravaganza, or alternatively, as an uninteresting Moon-only Apollo replay embodying no real intent of carrying human explorers to the Red Planet.

On the other hand, if a means could be found by which the same class of transportation system needed for lunar missions could be used to enable manned missions to Mars, the entire SEI would become practical, not only from a technological standpoint, but perhaps also from political and economic standpoints. Viewed another way, if a lunar program is underway, the question of whether or not a Mars mission is possible will be posed in the form; "Can we do it with what we have now?" If this question can be answered in the affirmative, then humans may yet walk on Mars during the working lifetime of the present generation of engineers.

The real challenge facing Mars mission designers, then, is to solve this problem: reduce the mass of the manned Mars mission to the point where an Apollo class transportation system can handle it. This can also be accomplished by a mission plan known as "Mars Direct" [i,ii,iii]. Mars Direct was devised to apply the leverage offered by the use of propellants manufactured on the Martian surface, and follows a split mission architecture to bring the Mars exploration program into Apollo's scale. Subsequently, a collaborative discussion with the NASA JSC Exploration Programs Office produced an alternative "Semi-Direct" architecture that also meets this objective, while eliminating some of the weaknesses and constraints present in the original Mars Direct plan. A version of this Semi-Direct option has since become the basis for a Design Reference Mission Study conducted in collaboration with personnel from NASA's Johnson Space Center, Marshall Space Flight Center, Ames Research Center, and Lewis Research Center [iv].

II.3 MARS DIRECT

The Mars Direct plan works as follows. At an early mission opportunity, for example in the year 2001, a single heavy lift launch vehicle (Saturn V class or better) with a substantial upper stage lifts off from the Cape and hurls an unmanned payload onto direct Trans-Mars Injection (TMI). This payload consists of an unfueled methane/oxygen driven two-stage Mars Ascent Vehicle (MAV) /Earth Return Vehicle (ERV), several tonnes of liquid hydrogen cargo, a 50 kWe nuclear reactor mounted in the back of a methane/oxygen driven light truck, a small set of compressors and an automated chemical processing unit, and a few small scientific rovers. This payload aerobrakes into orbit around Mars and then lands with the help of a parachute. As soon as it is landed, the truck is telerobotically driven a few hundred meters away from the lander, and the reactor is deployed to provide power to the compressors and to the chemical processing unit. The hydrogen brought from Earth is quickly catalytically reacted with Martian CO2 to produce methane and water, eliminating the need for long term storage of cryogenic hydrogen on the Martian surface. The methane is liquefied and stored, and the water electrolyzed to produce oxygen, which is stored, and hydrogen, which is recycled through the methanator. Ultimately these two reactions (methanation and water electrolysis) combined with an auxiliary CO2 reduction unit produce an amount of methane/oxygen bipropellant equal to 18 times the mass of the hydrogen imported from Earth. More than 90% of the bipropellant will be used to fuel the ERV, but 12 tonnes extra is produced to support the use of high powered, chemically fueled, long range ground vehicles.


The propellant production having been successfully completed, two more HLLVs lift off from the Cape in 2003 and throw their payloads onto TMI. One of the payloads is an unmanned fuel-factory/ERV just like the one launched in 2001. The other is a habitation module containing a crew of 4, provisions for 3 years, a pressurized methane/oxygen driven ground rover, and an aerobrake/landing engine assembly. Artificial gravity can be provided to the crew on the way out to Mars by tethering off the burnt out HLLV upper stage and spinning up at 1 rpm. The manned craft lands at the fully characterized and beaconed landing site from the previous 2001 mission, where a fully fueled ERV awaits it. Assuming the surface rendezvous is accomplished as planned and the ERV checks out, the second ERV can be landed either at the same site or several hundred miles away to start making propellant for the 2005 mission. Thus, every other year two HLLVs are launched, for an average launch rate of one HLLV per year, to pursue a continuing program of Mars exploration. A description of the original baseline Mars Direct vehicle elements is given in Baker and Zubrin [i].

The crew stays on the surface for 1.5 years, taking advantage of the mobility afforded by the high powered, chemically driven, ground vehicles to accomplish a great deal of surface exploration. With 12 tonnes of methane/oxygen bipropellant allocated for surface operations, about 24,000 ground kilometers can be traversed, ranging up to 500 km out from the base. Thus, each mission can explore an area of approximately 800,000 square kilometers, which is roughly the size of the State of Texas. At the conclusion of their stay, the crew returns to Earth in a direct flight from the Martian surface in an ERV. All personnel sent to Mars thus spend all of the stay time at Mars on the surface where they can be shielded from cosmic radiation and have natural gravity. No one is ever left in orbit. Each habitation module flown out to Mars adds incrementally to the surface infrastructure. As the series of missions progresses, either a single major base or a string of small bases is built up on the Martian surface.

II.4 MARS SEMI-DIRECT

The Semi-Direct plan differs from the Direct plan described above in that the first launch, instead of delivering an unfueled ERV to the Martian surface, delivers an unfueled Mars Ascent Vehicle (MAV) and some cargo to the surface along with a fueled Earth Return Vehicle that is placed in a highly elliptical Mars orbit. The MAV then makes its own 24 tonnes of methane/oxygen propellant along with another 12 tonnes for surface vehicle use in the same manner proposed for Mars Direct. As in the Direct plan, the second launch then delivers the crew in their outbound habitat to rendezvous with the MAV on the Martian surface. There they conduct 1.5 years of surface exploration and then ascend in the MAV to rendezvous in Mars orbit with the ERV. The ERV propulsion stage then performs Trans-Earth Injection (TEI), and the MAV capsule is used as an Apollo-type Earth Crew Capture Vehicle (ECCV). An iconographic depiction of the Semi-Direct mission sequence is given in Figure II.1.

Compared to the Direct plan, the Semi-Direct plan has the disadvantage that the ERV habitation module is not available to the crew during the 1.5-year surface stay, and that a mission critical Mars Orbit Rendezvous is required on the return leg of the mission. On the other hand, the Semi-Direct plan only requires about 1/3 the propellant manufacturing needed by Mars Direct, thus reducing surface power requirements for propellant production to the 15 kWe level, which is about what is needed for base life support in any case. Furthermore, the ERV habitation module can be made much larger in the Semi-Direct plan than in the Direct, either affording the crew better accommodations on the return leg or allowing a larger crew. If TMI throw capability is limited, the Semi-Direct plan lends itself naturally to a 3-launch scenario, in which the MAV, ERV, and surface


habitation module are each flown out on their own launch. Finally, while in neither the Mars Direct nor Semi-Direct plan is the crew endangered if in situ production of the return propellant (ISPP) fails, in the Direct plan continued ISPP failure can only be resolved by redesigning the mission. But in the Semi-Direct option, the program could be retrieved by resorting to delivering a wet MAV to the Martian surface on a dedicated cargo flight.

II.5 CHOICE OF TRAJECTORIES

Much has been written in the past about the necessity of achieving "quick trips" to Mars to reduce crew exposure to zero gravity and cosmic radiation. Two such options have been proposed for achieving quick trips: opposition class missions and accelerated fast transfer conjunction missions.

In the opposition missions, large amounts of propellant are expended to achieve high energy trajectories that allow the crew to perform round trip missions to Mars in about 1.5 years. However, the trajectories employed are such that over 90% of the mission time is spent in interplanetary space and only 30 days or so are spent in the vicinity of Mars. The net result is a very high cost mission (because of large propellant mass and resulting on-orbit assembly requirements) with very low payoff (because the time available for exploration on Mars is minimized). In fact, if the weather on Mars is unfavorable at the time of arrival, it is quite possible that an opposition class mission would be forced to leave Mars without achieving a landing. Furthermore, it has been shown [iii,v] that, despite their comparatively short total duration, opposition missions actually subject the crew to greater cosmic ray doses and zero gravity exposure than minimum energy conjunction missions. This is a result of the fact that virtually all of the opposition mission time is spent in interplanetary space; whereas at least half of a conjunction mission's time is spent on the surface, where natural gravity and substantial radiation protection are available. Radiation doses received on the Martian surface, even without taking advantage of the use of Martian regolith as shielding, are about a quarter of those received in interplanetary space. Thus, the opposition mission has been found to offer maximum cost, maximum risk, and low return, and has been dropped from further consideration by most of the Mars mission planning community.

Figure II.1: An Iconographic Depiction of the Mars Semi-Direct Mission Sequence [vi] Every two years two HLLVs are launched, one to deliver a crew in the Transfer And Surface Habitat (TASH), the other to deliver an unmanned payload consisting of a self-fueling MAV and an ERV. Each mission adds another habitat to the Martian surface, leading incrementally to a large Base or a network of Outposts. The year 1 TASH is flown to Mars without crew. This creates a reserve habitat for the first piloted flight, which arrives at Mars in the year 3 TASH.

The other type of fast transfer, the accelerated conjunction, has a more substantial basis in reason. An absolute minimum energy conjunction mission would consist of a Hohmann transfer taking 0.7 years each way to Mars and back, with a 1.2-year surface stay. With very little extra propulsive ÆV, this flight plan can be altered to consist of two 0.5-year transfers plus a 1.5-year surface stay. This would be beneficial, as the surface stay fraction of the mission is increased from 46% to 60%, with the total round trip time reduced slightly. If more propulsive ÆV is added, this process can be taken even further, but at a significant cost to the mission in terms of reduced delivered payload.


Such payload reductions do not merely reduce mission capability, they are a source of risk to the crew, as they imply the thinning out of redundancy of backups to various mission-critical propulsion, control, and life-support systems. The failure of any one of these systems would represent a much more deadly threat to the crew than the roughly one percent statistical incidence of cancer caused by a year of exposure to interplanetary levels of cosmic radiation. Thus, if crew safety is an objective, attempts to accelerate conjunction trajectories beyond certain limits will fail.

In Figure II.2, the average transit times to Mars for opportunities between the years 2003 and 2011 are shown as a function of the C3 leaving Earth and the hyperbolic approach velocity of arrival at Mars (C3 is the square of the velocity of departure from a planet). A minimum C3 of 15 km2/s2 is required simply to assure the capability of performing a transit to Mars during any opportunity. It can be seen that by increasing the C3 to 25 km2/s2, a substantial reduction (about 70 days) in transit time is achieved. This requires a ÆV leaving LEO only 0.42 km/s greater than that needed for a C3=15 transfer. However, if we push harder to a C3 of 40 (which requires 1.04 km/s greater ÆV than a C3=15 transfer), the further reductions achieved (about 10 days) are marginal. In other words, a C3 of 25 achieves most of the transit time reduction that is realistically possible. Beyond this, we rapidly reach the point of diminishing returns, where large amounts of ÆV are required to produce very limited results. Furthermore, trajectories with energies about C3=25 have the interesting property that they can be made to return to the point of departure exactly two years after leaving, thus giving a piloted spacecraft the option of a "free return" to Earth if a decision is made to abort the mission (the current JSC approach emphasizes "abort" to Mars surface as a less risky approach for some system failures). For these reasons we have baselined an outbound C3 of 25 km2/s2 as optimal for piloted missions. For unmanned cargo vehicles a C3 of 15 km2/s2 is used, as transit time is not an issue. If hyperbolic velocities of arrival at Mars are limited to 5 km/s to keep aerocapture technology requirements modest, then the average transit time outbound will be about 160 days. (Vhyp=5 km/s at Mars produces atmospheric entry velocities of 7 km/s, less than the 8 km/s faced routinely by the Space Shuttle and much less than the 11 km/s encountered by the Apollo capsules.) From an engineering point of view, it is necessary to design propulsion stages and payloads for a fixed C3, and take whatever transit time the celestial mechanics of a given year allows. Therefore, the actual outbound transits will vary from a minimum of 113 days for the 2003 opportunity to 190 days for the 2011 opportunity.

The Mars-to-Earth transit times for all return launch windows between 2007 and 2013 are shown in Figure II.3. Once again, it can be seen that a sharp reduction in transit time can be achieved by slightly increasing the departure C3 (to C3=16 km2/s2) above its minimum value of C3=12 km2/s2, but that subsequent gains are marginal. For these reasons we have baselined a Mars departure C3 of 16 km2/s2. Earth arrival hyperbolic velocities are kept below 6 km/s (atmospheric entry velocities of 12.44 km/s) to keep aerocapture entry requirements within reach of Apollo capsule technology.

If these trajectories are used, then the ÆVs required (including five percent gravity losses leaving Low Earth Orbit (LEO), two percent leaving Mars, and 0.1 km/s mid-course corrections each way) are 4.15 km/s for cargo leaving LEO, 4.6 km/s for piloted vehicles leaving LEO, and 1.73 km/s departing a 250 km by 33,000 km elliptical parking orbit (1 sol orbital period) at Mars.

Figure II.2: Average Trip Time Outbound to Figure II.3: Transit Times from Mars to


Mars for the Years 2003-2011 Most of transit shortening is achieved with C3=25 km2/s2. [vi]

Earth for the Years 2007-2013 Most of transit shortening is achieved with a TEI C3 of 16 km2/s2. [vi]

II.6 REQUIRED HLLV AND PROPULSION TECHNOLOGY

In Table II.1 we show the amount of payload that can be delivered to the Martian surface from a single launch of an HLLV that can lift 200 tonnes to a 300 km circular LEO orbit. This is the amount that could be lifted by either a Russian Energia B or by a U.S. Saturn V derived booster scaled up to incorporate seven F-1 engines in the first stage instead of the original vehicle's five F-1 engines (a Saturn VII). We show variants for both the cargo and piloted outbound trajectory and for the assumption that the third stage of this vehicle is either a cryogenic H2/O2 chemical stage with an Isp of 460 s or a near-term nuclear thermal rocket (NTR) with an Isp of 870 s. Such NTR performance represents 1960's NERVA technology. Current Russian NTR fuel elements could give an Isp of 960 s, or more, allowing an 8 t increase in TMI capability over the estimates given here.

In Table II.1 aerobrakes are assumed to have a mass equal to 15% of the object they are decelerating, NTR stages are assumed to consist of a 25 klb thrust engine (sufficient to throw a 200 t in LEO payload onto TMI with minimal gravity losses if three perigee burns are used), a 1.5 t shield, and a tank with a mass of 20 percent of the hydrogen it contains. Cryo stage dry mass fractions are taken at 15 percent, that of methane/oxygen (CH4/O2) and monomethylhydrazine /nitrogen tetroxide (MMH/N2O4) are taken at 8 percent. The ÆV for post aerocapture periapsis raise was taken as 0.1 km/s. Specific impulse for CH4/O2 is taken as 375 s, MMH/NTO as 320 s. Aerobraked options employed trajectories with hyperbolic approach velocities of 5 km/s, while those options employing propulsive capture used somewhat slower transfer orbits with hyperbolic approach velocities of 4 km/s to minimize the capture ÆV (to 1.6 km/s). The landing ÆV is taken as 500 m/s, accomplished by CH4/O2, with a lander drymass equal to 10 percent of the payload it is delivering. The payload delivered to Mars orbit (excluding aeroshell) in all cases is 1.28 times the payload delivered to the surface.

It can be seen that the use of NTR for TMI is highly advantageous, increasing the delivered payload by 77 percent for cargo and 100 percent for piloted flights. However, it can also be seen that NTR offers no significant advantage over chemical propulsion for Mars orbital capture. This is because the large dry mass of the NTR stage, combined with the large amounts of hydrogen propellant boil-off during trans-Mars cruise (even an H2/O2 chemical stage is only 14 percent H2, NTR propellant is 100 percent H2), destroys any performance advantage resulting from the high specific impulse of NTR when applied to a modest ÆV. This logic holds even more forcefully for the Trans-Earth Injection burn, which occurs two years into the mission and is much more conveniently accomplished by a space storable CH4/O2 stage.

Table II.1: Payload Delivery to Martian Surface via 200-tonne-to-LEO HLLV [vi]

Mission TMI Stage

TMI Throw(tonnes)

Payload Delivered to Surface (tonnes)Mars Orbit Capture System

Aero NTR H2/O2 CH4/O2 MMH/N2O4Cargo H2/O2 * 57.5 35.9 29.2 28.5 27.3 25.9


Piloted H2/O2 * 46.7 28.9 21.0 20.5 19.2 17.2

Cargo NTR ** 101.7 63.1 53.1 50.4 48.4 45.8Piloted NTR ** 94.2 58.4 43.2 41.4 38.6 34.8

* chemical cryogenic ** nuclear thermal rocket

Staging of the NTR stage immediately after TMI also reduces the total burn-time required of the NTR engines. This allows the NTR to either be run hotter than would otherwise be possible and therefore produce a higher Isp, or to reduce the specifications and thus the development cost of the NTR program. For these reasons we recommend staging of the NTR immediately after TMI. If desired, the exhausted NTR stage can be strung several hundred meters out on a tether during trans-Mars cruise to be used as a counterweight to provide artificial gravity for the crew, and can then be discarded shortly before Mars arrival.

It is clear from Table II.1, that aerocapture is the optimal mode of Mars orbital capture (MOC) for use in these missions because all (for the Mars Direct plan) or nearly all (for the Semi-Direct plan) of the TMI payload is destined for the Martian surface, and so all or nearly all of it must carry an aeroshield in any case. MOC via aerocapture in these plans thus eliminates a significant propulsive ÆV essentially "for free." Aerocapture in the plans we propose also faces smaller technological hurdles than in many other applications, since the conjunction class trajectory employed produces moderate entry velocities, and thus modest mechanical and thermal loads. The aerobrakes we require are also much smaller than those required for the far more massive traditional style missions, and if either flexible fabric low L/D or rigid bullet-shaped high L/D configurations are employed, can easily be launched "all-up" without any need for on-orbit assembly. In addition, the guidance, navigation, and control requirements on Mars Direct and Semi Direct aerocapture are less than in those plans where a subsequent Mars orbit rendezvous is anticipated. This is because it does not really matter exactly what orbit the vehicle enters since the orbit will be "erased" after the vehicle lands. Even the ERV, which is left in orbit in the Semi-Direct mission, only has to be accessed from the surface. This is true so long as its inclination and argument of periapsis are within the broad tolerances that will allow access to the designated landing site. It may also be remarked that direct entry landings on Mars, which would also work well for Mars Direct and Semi-Direct, will be demonstrated by the Mars Pathfinder mission currently scheduled for 1996.

II.7 A BASELINE DESIGN FOR MARS SEMI-DIRECT

A baseline system design for the Semi-Direct Mars mission could be conducted employing two launches of a 120 tonne to LEO HLLV during each launch window to Mars, i.e., every other year. Such a launch vehicle can be readily assembled using Space Shuttle components consisting of an ET core, four SSME's, two solid strap-ons, and an H2/O2 second stage [ii]. A third stage with two 15 klb thrust NTR engines (NTRs of this size would be comparatively easy to develop and would have wide application for unmanned planetary and GEO missions) performs two perigee burns to throw the payloads onto trans-Mars injection. Use of a single NTR engine with three perigee burns would also be acceptable. After trans-Mars cruise, aerocapture is used to insert the payloads into an elliptical Mars parking orbit. If a 200 t to LEO launch vehicle such as Energia B is available, the same payloads can be delivered with an H2/O2 third stage. Using such systems, the payloads shown in Table II.2 can be sent to Mars.

During the first launch opportunity, say 2001, both the Cargo "A" launch and the usually piloted "B" launch are flown to Mars unmanned and their surface payloads landed at a common site. The MAV payload thus delivered would then proceed to convert its 4 tonne supply of hydrogen


feedstock into 36 tonnes of CH4/O2 (the MAV only needs 24 tonnes for ascent, so 12 tonnes extras are available for use by surface vehicles) and 18 tonnes of water. Then at the next opportunity, 2003 (and all subsequent), the Cargo "A" launch would be flown out unmanned, but the piloted "B" launch would deliver a crew of 4 to the Martian surface where they would rendezvous with the previously delivered payloads. The crew of the first mission thus will have access to 60 tonnes of habitation, and if we discount the mass of the MAV ascent stages and their propellant, a total of 149 tonnes of useful mass will be available to the crew of the first mission while they are on the Martian surface. This is 5 times the useful surface payload carried by the baseline mission in NASA's 90 Day report (which had twice our baseline Semi-Direct mission's initial mass in LEO).

Table II.2: Cargo and Piloted Payloads for the Mars Semi-Direct Mission [vi]

Launch A; Cargo Total MOC Payload - 58 t Launch B; Piloted Total MOC Payload - 53.8 tEarth Return Hab 15 t (to Mars parking orbit) Aeroshell 7.6 t (Common with Cargo)

CH4/O2 TEI Stage 15 t (to Mars parking orbit) Lander (wet) 9.7 t (3.6 t dry + 6.1 t prop)

Aeroshell 7.6 t (Expended during landing) Surface Hab Module 30.0 tLander (wet) 6.5 t (off-loaded piloted lander) Field Science Equip. 2.0 t

MAV Capsule 4.0 t (2) 6 kWe DIPS* 1.5 tDry Ascent Stage 2.0 t (Common with TEIS) Pressurized Rover 2.0 t

LH2 4.0 t (36 t CH4/O2 + 18 t H2O) (2) Open Rovers 1.0 t

(2) 6 kWe DIPS* 1.5 t

Chemical plant 0.5 t

Cargo 1.9 t

*Dynamic Isotope Power Source

Each subsequent mission will deliver an additional habitation module, more rovers and science gear, another chemical plant and 24 kWe of power, and will add 12 t of CH4/O2 and 18 t of water to the surface stockpiles. Thus with only two launches of a 120 t to LEO HLLV per opportunity, an extremely muscular surface exploration capability is put in place starting on the very first mission. This capability will grow rapidly as the mission sequence proceeds. Furthermore, so long as the landing sites are chosen to be within one-way driving range by a CH4/O2 pressurized rover (up to 1000 km if the terrain is favorable), each crew will always have available to them two completely redundant MAVs, two redundant ERVs in Mars orbit, and at least two complete surface habitation modules either of which can house the entire crew for the duration. This plan can thus be considered very robust.

II.8 HABITATS AND CONSUMABLES

Table II.3 shows the consumables required for each member of the crew per day and the totals required to support a crew of four in each of the two habitation systems (Mars Transfer and Surface Habitation Modules (TASH) and the Earth Return Vehicle (ERV) habitation module) for each leg of the mission. The numbers given under the Need/man-day column are NASA standards [vii], except that we have replaced 0.13 kg/day of dehydrated food with 1.0 kg/day of whole (wet) food. Such a mixed diet is much better for crew morale on a long mission than dehydrated rations only, and costs the mission very little in the way of added mass since the water content of the whole food makes up for the losses in the potable water recycling system.

The large benefits accruing to a strategy of using in situ resources can be seen from Table II.3. Without the water and oxygen manufactured on the Martian surface by the MAV chemical plant, an


additional 13 tonnes of consumables would have to be shipped out with the crew on the Mars Transfer and Surface Habitation Modules. This would increase the required consumables from nine tonnes to 22 tonnes, which, since we only have the capability of delivering a 36 tonne habitation module, would be very difficult to accommodate. As noted above, each MAV produces 18 tonnes of water in advance on the surface. This will provide an excess in water availability over NASA nominal requirements, which should be a real plus for the morale of a hardworking crew on a desert planet. For these reasons, in Table II.3, there is no requirement to transport oxygen or water to support the TASH surface stay. It can also be seen that each habitat flies out to Mars with enough food for an 800 day mission, which also allows it to suffice for a two year free-return abort. In the latter case, the crew in the habitation module will have to exploit the six tonnes of CH4/O2

propellant in the lander stage (unneeded as propellant in the event of a free return, which is concluded by aerocapture into Earth orbit), and will have to reduce their use of wash water to 40 percent of the NASA nominal levels. This will be uncomfortable and bad for morale, but it could be endured and survived, which is the only issue in the event of such an abort. Also, in Table II.3, there is no waste of potable water shown because potable water lost due to inefficiency of recycle is made up by water added to the system due to use of whole food.

Table II.3: Consumable Requirements for Mars Semi-Direct Mission with Crew of 4 [vi]

Item Need/man-day

FractionRecycled

Wasted/man-day

ERV Requirement

TASH Requirement Totals

200 day Return 200 day Out 600 day SurfOxygen 1.0 kg 0.8 0.2 kg 160 kg 160 kg 0 160 kgDry Food 0.5 kg 0.0 0.5 kg 400 400 1200 1600Whole Food 1.0 kg 0.0 1.0 kg 800 800 2400 3200Potable Water

4.0 kg 0.8 0.0* 0 0 0 0

Wash Water 26.0 kg 0.8 5.2 kg 4160 4160 0 4160Totals 32.5 0.79 6.9 5520 5520 3600 9120*No wastage because water added via whole food.

The subsystem mass allocations in Table II.4 represent good targets that should be achievable using near-term technology and a disciplined engineering design. However, should the required subsystem masses exceed these allocations, very large margins can be provided by shifting the mission to a three launch scenario, in which the TASH, the ERV, and the MAV are each sent out to Mars by a separate HLLV launch. In that case, the ERV mass could be increased by 67%, to 25 tonnes instead of the current 15 tonnes. The MAV surface payload could be increased even more, by 188%, allowing 39 tonnes to be landed instead of the current 13.5.

Table II.4: Mass Allocations for Two-Launch Mars Semi-Direct Mission Plan [vi]

Earth Return Vehicle Habitation module Transfer and Surface Habitation moduleERV Habitat Structure 4.0 tonnes TASH Structure 7.0 tonnesLife Support System 2.5 Furniture and Interior 2.0Consumables 5.5 Life Support System 4.0Electrical Power 1.5 Consumables 9.2Reaction Control System 0.5 (2) 6 kWe DIPS 1.5Com. & Info. Management 0.1 Reaction Control System 0.5Spares and Margin 0.9 Com. & Info. Management 0.2


ERV Habitat total 15.0 tonnes Crew 0.4EVA Suits 0.4

MAV Capsule 4.0 Lab Equipment 2.5Crew 0.4 Field Science Equipment 2.0EVA Suits 0.4 Pressurized Rover 2.0Samples 0.2 (2) Open Rovers 1.0MAV Total 5.0 tonnes Spares and Margin 3.8Total ERV Habitat/MAV 20.0 tonnes TASH Total 36.5 tonnes

Given these consumable requirements, the mass allocations for the ERV habitat and the Transfer and Surface Habitation Modules can be assigned. These are presented in Table II.4. Since the ERV travels back to Earth attached to the MAV capsule (which is used for Earth entry), we list them together.

II.9 SURFACE SYSTEMS ARCHITECTURE

The surface systems architecture suggested is modular, flexible, robust, and takes maximum advantage of the use of local resources to leverage all aspects of the mission. On the very first mission, two transfer and surface habitation modules are available, either of which alone is fully capable of supporting the crew for the entire surface stay. Two complete Mars Ascent and Earth Return Vehicles are also available. A total surplus of water equal to 3 times the minimum requirement is available (produced by the two MAVs), as is a food cache sufficient to support the crew for four years (triple the planned surface stay time). The crew has two pressurized rovers and four open rovers available for use, all of which run on CH4/O2 propellant. A total of 24 tonnes of this propellant is available on the surface to support these vehicles, sufficient to allow up to 48,000 km worth of travel by the pressurized rovers or triple that if the open rovers are employed instead. Along with the rovers, nine tonnes of scientific equipment are also available. The MAVs and pressurized rovers can be used as short duration safe-havens for the crew. Counting these plus the two large Transfer and Surface Habitation Modules, a total of six habitable volumes are available to the crew at the base. Since each MAV and TASH deliver a set of four spacesuits to Mars, four sets of spacesuits are available for the use of the crew.

Each MAV and TASH lander is equipped with its own set of two 6 kWe Dynamic Isotope Power Systems (DIPS), either of which can produce the bare minimum power required for life support or in situ propellant production. Each spacecraft is thus redundant in its power production. However, after the landing is accomplished, the four pairs of DIPS present on the surface can be linked in a grid. Once this has been done, each DIPS will have not one, but seven other units as backups. Total installed power at the base is 48 kWe, about eight times the minimum required for survival. Much more power can be generated for limited periods of time (either at the base or at remote sites) by using the CH4/O2 engine on any one of the six rover vehicles to turn an electric power generator.

Using the same ISRU units responsible for propellant manufacture, virtually unlimited quantities of oxygen can be readily produced on the Martian surface from the atmospheric CO2 (CO2 comprises 95 percent of the Martian atmosphere). However, nitrogen and argon combined only comprise about 4.3 percent of the Martian atmosphere, and thus buffer gas will be much harder to come by. It is thus imperative that the habitats and pressurized vehicles operate at the lowest buffer gas partial pressures possible. The five psi (3.5 lbs O2, 1.5 lbs N2) atmosphere used in Skylab is therefore recommended.


Apollo crews operated on two-week missions in an atmosphere consisting of five psi oxygen and no buffer gas. Since the maximum rover excursion will be of this order, this is what we recommend for the pressurized rovers. Such a low-pressure rover would require no airlock. Instead, the astronauts inside would simply don their spacesuits, valve off the pure oxygen atmosphere inside to Mars, and then open the hatch and walk outside. Assuming a rover interior volume of 10 cubic meters, 3.3 kg of oxygen would be lost each time the rover was depressurized in this way. If part of the rover's interior atmosphere were pumped into a compressed oxygen cylinder before valving, oxygen losses would be reduced further. In any case, the losses could easily be made up by in situ production of oxygen at the base. The low-pressure rover would allow the use of a low pressure (3.8 psi oxygen, no buffer gas, as in Apollo) spacesuit for EVAs, with no pre-breathing required. Such a suit would be the lightest and most flexible possible, and would thus enhance the quality of surface science performed. Since the oxygen is replaceable, a simple once-through system in which an exhaled lung-full of air is vented directly to the environment (in the manner of SCUBA gear) would be feasible, allowing a great simplification in space suit design. Such a simplification would not only further the goal of reduced spacesuit mass, but would dramatically enhance spacesuit serviceability, reusability, and reliability, and thus making possible a Mars surface mission incorporating not tens, but thousands of EVAs.

Assuming a breathing rate of five gallons a minute, each astronaut using such a low-pressure oxygen "scubasuit" would expend 1.3 kg of oxygen during a four hour EVA. Thus if two astronauts were to perform two EVAs each per rover excursion day, venting the rover twice in the process, 12 kg of oxygen would be used up. If the rover were to be operated in this manner every day of the 500 day surface stay, a total of six tonnes of oxygen would be used. Wasting this much oxygen would be a burden if it had to be transported from Earth, but, if produced on Mars, would only require 200 days of operation of an ISRU plant driven by a single 6 kWe DIPS.

II.10 CONCLUSIONS

In conclusion, the use of direct-throw mission strategies combined with utilization of in situ propellants allows for simple, robust, cost-effective, and coherent plans for Mars Exploration. By eliminating the need for construction of futuristic mega-spaceships on-orbit, such a strategy drastically reduces up-front development costs and technology challenges of the required flight systems, thus enabling an early commencement of human Mars exploration. Furthermore, in contrast to accelerated approaches that employ brute-force means, the use of in situ resources right from the start of the program allows missions to be conducted in such a way as to minimize cost and increase exploratory return for each recurring mission.

The 50 kWe power requirements for the manned Mars Direct propellant production can be met by near term surface nuclear electric systems. In the case of the Semi-Direct mission, this can be met by currently existing 10 kWe Topaz or near-term DIPS units. Near-term physical chemical life support system processes nearly identical to the in situ propellant production processes are found to be optimal from the point of view of mass and power. Combined with stockpiles of consumables that can be produced in situ on the Martian surface, these processes provide a robust life support architecture adequate to meeting the challenge of a 2.5-year round-trip Mars mission. The use of the transportation system/surface architecture described also allows for rapid evolution to either a permanently staffed large central base or a string of widely dispersed, but surface-to-surface transportation linked, exploratory outposts spread over the Martian surface.


A space transportation architecture similar to that described can provide an attractive baseline for human Mars exploration planning, and hence appropriate resources should be allocated for the rapid development of in situ propellant production and the other key technologies required.

REFERENCES

[i] D. Baker and R. Zubrin, "Mars Direct: Combining Near-Term Technologies to Achieve a Two-Launch Manned Mars Mission," Journal of the British Interplanetary Society 43(11):519-525, Nov., 1990.

[ii] R. Zubrin and D. Baker, "Humans to Mars in 1999," Aerospace America 28(8):30-33, August, 1990.

[iii] R. Zubrin, D. Baker, and O. Gwynne, "Mars Direct: A Simple, Robust, and Cost-Effective Architecture for the Space Exploration Initiative," AIAA 91-0326, 29th Aerospace Science Conf., Reno, Nevada, Jan., 1991.

[iv] D. Weaver, "Mars Study Team Reference Mission Overview," presented at Mars Working Group Conf., NASA Ames Research Center, May, 1993.

[v] K. Joosten, Bret Drake, D. Weaver, and John Soldner, "Mission Design Strategies for the Human Exploration of Mars," IAF-91-336, 42nd Congress of the IAF, Montreal, Canada, Oct., 1991.

[vi] R. Zubrin and D. Baker, "Practical Methods for Near-Term Piloted Mars Missions", AIAA 93-2089, presented at 29th Joint Propulsion Conference and Exhibit, Monterey, Calif., June 28-30, 1993.

[vii] A. Gonzales, L. Harper, E. Dunsky, and B. Roberts, "Mars Surface Mission Life Support Summary," presented to the Mars Exploration Workshop II, NASA Ames Research Center, May 24, 1993.


Addendum IIIMISSION PLANNING AND MARS ARCHITECTURE TRADE-OFFS

(Addendum to Chapters 5, 6 and 9)

Gordon R. Woodcock

Table of ContentsIII.1 EVOLUTION SINCE THE INITIAL MARS REPORT

III.1.1 Architectures ReviewIII.1.2 HLLV Future in DoubtIII.1.3 Demise of Space Nuclear ProgramsIII.1.4 Growth in Space CooperationIII.1.5 Mars Resources: Demonstration of Propellant Production

III.2 CLASSES OF ARCHITECTURESIII.2.1 To Mars and BackIII.2.2 In-Depth Science and Movement Towards SettlementIII.2.3 Permanent Transport InfrastructureIII.2.4 Exotics

III.3 EVALUATION OF ARCHITECTURESIII.4 NEXT STEPSREFERENCES

This review addresses the evaluation of Mars exploration architectures and discusses appropriate steps for IAA to develop a "preferred" international Mars program.

III.1 EVOLUTION SINCE THE INITIAL MARS REPORT

The Mars Subcommittee report [i] was initially prepared when the U. S. space industry was conducting a NASA study to define a program of lunar and Mars exploration which might be implemented by the U. S. with international partners. The projected cost of the proposed program, particularly the version described in the "90-Day Study" report, substantially exceeded U. S. political funding priorities for aggressive human space exploration, and by implication, those of the rest of the world as well. Meanwhile, a modest-scale robotic Mars exploration program continues, with increasing levels of international cooperation.

Viewpoints, status of technical elements of a human Mars exploration program, understanding of Mars architectures, and economic/financial considerations have all changed and become better delineated, in the past three to four years. Accordingly, a review and update of Mars architectures and their implications for the potential future of human Mars exploration is appropriate.

III.1.1 Architectures ReviewAlthough the level of research activity into Mars mission analysis and architecture synthesis has slowed considerably, a few new architectures have emerged, some offering implementations at far lower cost than the original "90-Day Study" approach. Some are also well suited for international programs. Finally, a new evaluation approach is suggested. Part of this approach is to recognize

Boeing, Huntsville, Alabama, USA.


that firm selection of an architecture is not possible now since the various architectures score differently depending on goals, objectives, rationales, and long-range exploration outlook. These latter factors have yet to be defined and agreed upon by the participants in an international program.

It is useful to consider in a broad overview the evolution of thinking about Mars missions and architectures over the past generation and a half. The first serious engineering proposal for a Mars mission was that of Wernher von Braun circa 1953 [ii]. An ambitious expedition was proposed involving 70 explorers and a fleet of ships, on a conjunction-class profile using chemical propulsion.

Not much more happened until the early 1960s when NASA began a series of studies that focused on the then emerging technology of nuclear thermal propulsion. These studies were also influenced by the Apollo goal, "to land ... and return safely", without much attention to what might be done while "there". These studies continued until about 1972, by which time the U.S. national mood had switched from enthusiasm about space exploration to concern about its costs and benefits. NASA focused on the Space Shuttle program and on activities with near-term economic payoff.

Thinking about exploration missions was rekindled by the U.S. President's Commission on Space report of 1986 [iii]. The Commission report led, somewhat circuitously, to the declaration in 1989 by President Bush for a Space Exploration Initiative (SEI; not called that in the beginning) to "return to the Moon" and begin the human exploration of Mars. The NASA study in response to the Bush initiative (the so-called "90-Day Study" [iv]) began by focusing on an architecture that used cryogenic chemical propulsion and aerobraking. Later, greater emphasis was given to nuclear thermal propulsion, and all then known feasible architectures were examined at some level of detail.

The NASA studies for the Bush initiative were widely criticized as far too expensive. Some of this was justified inasmuch as the cryogenic/ aerobraking architecture is not the most economic, but most of the high costs forecast by these studies resulted from the way the studies were done and presented. Whereas most previous studies presented the cost for one mission, either to the Moon or Mars, the NASA "90-day Study" documentation presented the total estimated life cycle cost for 30 years of exploration activities, including a long-term lunar base and a series of several Mars missions. The studies were quite comprehensive, for example, including the cost of lunar science observatories. While considerable progress has been made in reducing the projected cost of exploring Mars since the "90-Day Study", much of the reduction has been obtained by a scale-back of mission assumptions. Some cost reduction has also come from more efficient architectures.

III.1.2 HLLV Future in DoubtWhen the SEI studies were under way, it was a nearly universal assumption that a new generation of heavy lift launch vehicles (HLLVs) would be built as the next major step in publicly funded space transportation development. In only a few years, thinking has changed drastically. Low-cost launch is now given top priority and, with NASA getting out of the space transportation business entirely, commercialization/privatization is the normative future. If a Mars mission requires a heavy lift vehicle, it now appears that the entire HLLV R&D cost would be ascribed to the Mars program. This is a rather substantial burden for a program to bear. Mars architectures that could be implemented with frequent launches of a low-cost, smaller system might have a significant advantage.

During the SEI studies, the launch cost per pound of payload for an HLLV was quoted as about $2500. This probably understates the cost of operating a system that is launched infrequently and has only one purpose. A launch cost on the order of $4000/lb is probably nearer the truth. Payload


costs for low-cost fully reusable launch systems have been quoted below $500/lb with a norm about $1500/lb. At the launch rates to support a Mars program, a typical single-stage-to-orbit (SSTO) vehicle with 15 t payload would operate near or below the low cost limit of $500/lb. If one calculates the launch cost for a Mars mission based on mass in low Earth orbit, using a representative mass of 600 metric tons, one arrives at the values in Table III.1.

Clearly, assembling a Mars mission from 15 t payloads involves significant Earth orbit operations. However, the International Space Station (ISS) will be over 400 t when fully assembled, so building a Mars vehicle in orbit is a small extrapolation from anticipated ISS experience.

Table III.1: Launch Costs

Launch system Payload $/lb Cost to launch 600 t.Heavy Lift 4000 $5.3 billionNext-gen. ELV 2000 $2.65 billion Norm SSTO 1500 $2.0 billionLow-Cost SSTO 400 $530 million

III.1.3 Demise of Space Nuclear ProgramsWhen the SEI studies were under way, it was a nearly universal assumption that space nuclear electric power technology would be developed by the time Mars missions were undertaken. Mars architectures routinely assumed nuclear power systems would be available for application to Mars surface infrastructure. It was also assumed that nuclear thermal propulsion and/or high power nuclear electric power systems could be routinely developed if the requisite R&D funding were provided.

Today, almost all vestiges of space nuclear power technology programs have vanished. Almost all the people with space nuclear propulsion experience have retired. The U. S. Department of Energy nuclear laboratories are striving to convert to post-Cold-War civilian research applications. While there is nothing, except perhaps political opposition, to prevent development of space nuclear technology for Mars architectures, the prospects for doing so can no longer be regarded as "routine".

III.1.4 Growth in Space CooperationApproximately simultaneous with the ending of the U.S. SEI studies, the Space Station program brought Russia in as a major partner. Canada, Europe, and Japan were already participating. While international space cooperation has existed since the beginnings of space exploration, it has evolved from data exchange, cooperative science, and joint development of small spacecraft to full partnerships in major enterprises.

International bodies such as COSPAR and COPUOS do not have program authority. Joint programs are entered into by bilateral or multilateral agreements between nations. For major programs, the norm has been for one nation to initiate a program and then invite others to participate.

The investment required for human Mars exploration makes it unlikely that any nation will initiate a program without partnering agreements. This means that the definition and planning of such a program must be undertaken by an international body. Such a body could be set up by multilateral agreement, created by the U. N., or initiated by the IAF/IAA based on sponsorship of a group of


nations. In any case, the planning body would develop one or more specific Mars exploration proposals based on guidelines agreed upon by the sponsoring states (see Chapter 8).

III.1.5 Mars Resources: Demonstration of Propellant ProductionThree concepts have been developed for production of propellant on Mars: (1) Electrolytic extraction of oxygen from the atmosphere by reduction of CO2 (a hot zirconia cell is used); (2) Production of methane and oxygen from CO2, using hydrogen brought from Earth; and (3) Electrolysis of water to produce hydrogen and oxygen. The first two of these use Mars' atmosphere while the third relies on finding and mining water, probably as permafrost. In case 1, hydrogen or other fuel is brought from Earth. The ratio of propellant load to propellant brought is 7, since the typical mixture ratio for hydrogen is 6. In case 2, the hydrogen is converted to CH4, which quadruples the fuel mass. Some oxygen is produced in the process of making methane. By recycling a small amount of "seed" hydrogen, as much oxygen as desired may be extracted from Mars' atmospheric CO2. If enough oxygen is produced to reach an optimal rocket mixture ratio with methane, the ratio of propellant load to propellant brought is 18 to 20. Whether case 1 or case 2 gives the best leverage is somewhat dependent on how sensitive the system is to specific impulse (H2/O2 about 475, methane/O2 about 375). The methane option usually wins. Methane/oxygen is also the least energy demanding of the three, as reported by Zubrin and Baker [v], and it doesn't require active refrigeration to liquid hydrogen temperatures as does option 3. Option 3 is also less attractive for current planning because we don't know where adequate supplies of water will be found, or how accessible the water will be.

Experimental demonstrations of CO2 electrolysis and methane/oxygen production have both been accomplished. Water electrolysis, as will be used in option 3 (and option 2), is a well-known technology. The propellant production equipment is small, simple, and lightweight compared to the quantity of propellant that can be produced. The principal concern is the electrical power supply needed for each of these options.

To produce liquid oxygen and hydrogen from water, including cryogenic refrigeration, requires 5 to 6 kWh/kg, or 5 to 6 MWh per metric ton. Useful production rates are 10 to 100 t per year, signifying a power requirement crudely 10 to 100 kWe. The power to operate a Mars base of a few people, not including propellant production, is expected to be on the order 25 to 50 kWe. Generating this amount of power on Mars from solar energy will be daunting, which is why architecture designers so eagerly assumed availability of nuclear sources. A modest Mars base using solar power will need to cover roughly a football field area with photovoltaics.

III.2 CLASSES OF ARCHITECTURES

Architectures can be grouped by the kinds of goals they satisfy rather than the way they work, the profiles they can fly, or the technologies they use. These latter three categorizations have been used for almost all prior studies and tend to lead to confusion in comparing and evaluating architectures. In particular, we need to quit focusing on opposition versus conjunction profiles and focus on the basic needs and objectives, either satisfied or not satisfied. Here I shall group architectures according to three general classes of goals.

III.2.1 To Mars and BackIn 1961, President Kennedy committed the U.S. to "land a man on the Moon and return him safely to Earth." Thus was born Project Apollo, which proceeded to fly nine manned missions to the


vicinity of the Moon, and to land two men on each of a total of six landings. All crews returned safely to Earth.

The first round of major NASA design studies of Mars missions was conducted during the Apollo development period. The idea of "sending a Man to Mars and returning him safely to Earth" was the most important underlying theme, usually unstated, in the conduct of these studies and the design of the architectures. This is true even though some of the studies went beyond simply reaching Mars to consider in-depth science missions and permanent bases. These studies originated and concentrated on the Apollo archetype for Mars, the opposition-class mission with nuclear thermal propulsion. These architectures are characterized by a minimum Mars surface architecture and minimum mission durations ("Let's don't do any more of that than we have to do.").

This theme was echoed in the NASA "90-Day Study" for which the baseline architecture simply replaced nuclear thermal propulsion with cryogenic propulsion and aerobraking. The "90-Day Study" went further to consider longer-duration stays on Mars later, by adapting the transportation architecture to delivering cargo and flying conjunction profiles. Other studies during the SEI period considered alternate architectures including some that would fit into other categories, but the studies focused more on how to get to Mars and back than on what to do while at Mars.

There were nuclear thermal architectures aimed at round trips less than one year as well as the more typical 16 months; there were low-thrust propulsion architectures for both opposition and conjunction profiles. Much attention was given to Venus swing-by profiles, a variation on the opposition profile that eases ÆV requirements. Conjunction profile architectures in this group maintain the crew in Mars orbit for most of the long stay time at Mars, with one or more surface sorties, and probably extensive teleoperations on the surface from Mars orbit, taking advantage of the elimination of long communications delays.

This group might be considered the short-term commitment group: To Mars and Back, with a couple of encores, and then we have "been there, done that".

The Synthesis Group [vi] began to edge towards architectures with more focus on the actual activities when on Mars. Each of their architectures was related to a combination of goals and objectives such as science or space industry, not just "to Mars and Back". Their initial human mission, while opposition-like, took advantage of an unusual Venus swing-by opportunity with launch year 2014, in which a 3-month stay on Mars is possible. The surface stay was long enough to require preplacement of surface elements on a prior year cargo mission. This feature broke the paradigm.

III.2.2 In-Depth Science and Movement Towards SettlementThese architectures feature extensive surface architecture elements, enabling real exploration, and generally use a conjunction profile with 500-day stay beginning on the first human visit. Attention is given to using Mars resources for life support, surface transportation, and return to Mars orbit or to Earth.

Mars Direct is the archetype for this group. It is described in Addendum II of this report. The core features of Mars Direct are commitment to building surface infrastructure, elimination of Mars orbit operations, use of Mars resources, and use of Mars-produced propellant for return to Earth directly from the surface of Mars. Mars Direct uses near-term chemical propulsion technology and aerobraking direct from the approach to landing on Mars. It could be implemented about as quickly


as any architecture in the report. In view of the chemical propulsion technology and the launch direct from Mars surface to trans-Earth injection, Mars Direct is tied to the long stay times of the conjunction profile. (However, in-space transit times may be shorter than for opposition profiles.) These long stays are, of course, consistent with the basic philosophy of the architecture.

Other features often described are direct launch to Mars by HLLV, and use of nuclear power on Mars for propellant production. These can be "engineered out" without losing the essential features of this architecture. For example, despite the reluctance of Mars architects to accept the idea, Earth orbit operations are quite routine and becoming more so. A Mars direct system could easily be assembled in Earth orbit from elements delivered by a future modest-capacity commercial launch service. Nuclear power is the "easy" answer to Mars surface power, but solar is possible. The cost delta over nuclear, for delivering a solar power system to Mars capable of supporting a Mars Direct mission, is on the order of a few hundred million dollars. A nuclear powerplant cannot be developed for that. Clearly, as more and more power is required, nuclear will become more economical in the long run. This is true unless a way to implement solar power from Mars resources can be found.

This group of architectures can be considered a mid-term commitment. If we are going to Mars at all, we must persevere long enough to reap the scientific benefits and explore the habitability of Mars for humans.

Any architecture that adopts long stay times on Mars from the beginning, gives adequate attention to buildup of surface infrastructure, and uses Mars resources in a reasonable way may be considered applicable to this group. Nuclear thermal and nuclear electric propulsion do not fit well here because the development costs and times are not needed in view of the conjunction profiles. Solar electric propulsion also may not fit well because of development and procurement cost (see discussion in the following paragraphs).

III.2.3 Permanent Transport InfrastructureThis group is somewhat less studied than the others. The archetype solar electric propulsion transfer from high Earth orbit (or from a lunar libration point) to Mars orbit and back, with a reusable Mars lander/ascent vehicle operating on methane/oxygen produced on Mars is taken as the baseline. (The relatively small amount of descent propellant might best be supplied from Earth by the arriving transfer vehicle.) Transportation from low Earth orbit to high orbit would employ a reusable lunar transportation system. Complement this with a reusable Earth-to-LEO transportation system for a completely reusable Mars transportation system.

At the present time, spacecraft last for up to 20 years or more with no maintenance. A permanent Mars transportation architecture could probably be designed for 30 to 50 year life, with maintenance.

The solar electric system probably needs to be on the order of 10 megawatts. It is reported that high-quality commercial space arrays (gallium arsenide) are being produced at about $1000/watt. A multi-megawatt purchase could probably reduce this to less than $500/watt, at which point the 10 megawatt array costs $5 billion. Launch cost to high orbit is on the order of $1 billion (future Earth-to-LEO costs) and these costs are only borne once. Large solar arrays are simple repetitive structures readily adaptable to robotic deployment and assembly from subassemblies readily delivered by commercial-size launchers.


Other architectures in this class include cycler systems and nuclear electric propulsion. It is not likely that nuclear electric systems can be designed to last as long as solar electric systems, and some of those conceptually designed during the SEI studies were specified to last only for one mission. A few studies also considered solar sails, which might fit into this category.

These architectures might be selected when a long-term commitment to Mars exploration and settlement is made. A solar-electric architecture may be relatively economic to implement, depending on the cost of a multi-megawatt purchase of photovoltaics for space use.

III.2.4 Exotics One should mention in passing those architectures based on exotic propulsion such as nuclear pulse, ultra-high-power nuclear electric, nuclear gas-core, and nuclear fusion. Most of these were structured to take advantage of the features of the exotic propulsion, usually fast trips. They have not been taken to the point of a complete architecture description. The performance capabilities of these technologies are, of course, not well defined.

If a propulsion system can deliver one milli-g or better acceleration at a specific impulse of 2500 seconds or better, it will be capable of nearly eliminating the launch window problem for Mars travel. With this propulsion system, travel times on the order of a few months would result from departures at inopportune times, while travel times of as little as a month would result from departures at opportune times (though one could depart and return at any time with a fairly acceptable trip duration).

III.3 EVALUATION OF ARCHITECTURES

Evaluation of architectures must wait until program goals, objectives, and constraints are established. As noted above, architectures may be grouped into classes associated with very general kinds of goals and objectives. As these goals become more specific, one may derive sufficiently detailed evaluation criteria and methods to select a specific architecture.

The method of evaluation itself can be a subject of evaluation and selection. There are two general techniques in widespread use. The first is a scoring and weighting method, many of which have been described in the literature. The approach is to establish a set of criteria, usually ten to twenty, each representing a desirable feature according to the goals and objectives. Crew safety, crew time at Mars per mission opportunity, and mass in low Earth orbit are examples of such criteria. After the criteria are established they may be weighted. For example, if crew safety was considered twice as important as mass in low Earth orbit, then crew safety might be weighted 10 points and mass only 5. Each candidate architecture is scored according to its satisfaction of each criterion. Scoring may be judgmental or may use some semi-quantitative method such as the analytical hierarchy process (AHP) or quality function deployment (QFD). Scores are multiplied by weights and added to obtain total scores. The architecture with highest total score is selected. (See [vii] by Olds for a classical aerospace conceptual design optimization model.)

The second method establishes a single figure of merit, often life cycle cost. Additional criteria such as safety and perhaps a schedule of mission accomplishment are assigned threshold acceptability (pass/fail) values. Architectures are adjusted to satisfy the threshold criteria or, if this is not possible, rejected. The architectures are then ranked or evaluated by the figure of merit. This method is more work than the first since substantial effort may be needed to adjust architectures to


satisfy pass/fail criteria. However, in the author's opinion, it is more satisfying to a selection authority and more reliable in choosing the best solution.

III.4 NEXT STEPS

There are presently no national programs to develop long-range plans for human exploration or settlement of Mars. To plan and accomplish such a program would incur high cost and take a long time. Thus, it could be a priority for a national program only if space preeminence itself is seen by some nation as a high priority. Today no nations with the resources to aspire to human Mars exploration hold space preeminence as high priority.

The time and cost for a human Mars exploration program are not necessarily prohibitive for a group of several or more spacefaring nations. The breadth and depth of Mars exploration is such that many opportunities also exist for participation of non-spacefaring nations.

Space cooperation is the norm today. However, the norm in developing cooperative programs is for one nation to initiate a program and invite interested partners. Hence, it is a "catch-22" situation. An international program is probably the only way to initiate human Mars exploration, but there is no established mechanism to initiate it as an international program.

The International Academy of Astronautics or the International Astronautical Federation should undertake to be that mechanism.

The first step is to ascertain international interest in human scientific exploration and possible settlement of Mars. The IAA/IAF should, through the UN or by discussion with a core group of potentially interested countries, seek a charter to develop a concrete proposal for a program. The charter would essentially state that if IAA/IAF undertakes a proposal, high-level ministers of the interested states would periodically meet to review the status of the proposal, provide oversight and guidance, and seek approval of the proposal once completed.

The next step is to appoint and convene a working group. Twenty to thirty personnel might be needed, with each having at least a half-time commitment to the task. The number can be adjusted as needed to achieve adequate representation of the interested states. After an initial kickoff meeting of one or two weeks, members should be able to work at their parent institutions using electronic communications. Quarterly meetings might be held at a rotating location. The IAA has proposed an International Space Studies Institute (see Appendix D).

The next step is to develop goals, objectives and rationale for the decision-making with rough-order-of-magnitude resource and schedule estimates. Enough is known about Mars architectures to permit this to be done without new in-depth studies. Approval of this step by the interested states should be sought before embarking on architecture design. It is vital to have a clear definition of what such a program shall accomplish, and in what order and roughly on what schedule, and at what cost, before proceeding. Previous attempts to develop programs for human Mars exploration have failed because they have not gotten this right, and have not done it first.

What follows is to develop agreements on participation by all interested states. The number of interested states could grow as the project matures. An important part of this step is dealing with issues of technology transfer, openness of scientific discovery, and intellectual property rights. Also included are agreements on development of any needed new technology.


These preparatory steps are not easy. They will occupy years, even with good will on the part of all parties. Once these difficulties are overcome, execution of the program can proceed.

REFERENCES

[i] G.W. Morgenthaler (ed.), "The International Exploration of Mars: A Mission Whose Time Has Come" Acta Astronautica 31:1-101, Oct., 1993.

[ii] W. von Braun, The Mars Project, University of Illinois Press, Urbana, 1991. [Translation of: Das Mars project. Reprint. Originally published: Urbana, University of Illinois Press, 1953.]

[iii] U.S. National Commission on Space, Pioneering the Space Frontier [The Paine Report], Bantam Books, New York, 1986.

[iv] NASA, Report of the 90-Day Study on Human Exploration of the Moon and Mars, Washington, D.C., 1989.

[v] R.M. Zubrin and D.A. Baker, "Mars Direct: Humans to the Red Planet by 1999", presented at 41st Congress of the International Astronautical Federation, Dresden, GDR, Oct. 6-12, 1990.

[vi] U.S. National Space Council, America at the Threshold: America's Space Exploration Initiative [The Stafford Report], Report of the Synthesis Group, U.S. Government Printing Office, Washington, D.C., 1991.

[vii] J.R. Olds, Multidisciplinary Design Techniques Applied to Conceptual Aerospace Vehicle Design, CR-194409, NASA, Washington D.C., 1993.


Appendix AA SHORT GUIDE TO MARS

by Christopher P. McKay

Mars, the Red Planet, is the fourth planet from the Sun. It is aptly described as a small, cold, dry planet with a thin atmosphere. Nonetheless, it has the most clement non-terrestrial environment in the Solar System. It is certainly the most likely candidate for long-term manned exploration, colonization, and planetary ecosynthesis. An extensive body of information exists on all aspects of the planet.

Observations of Mars from Earth provided the only information on the planet until the flyby mission of Mariner 4 in 1965. NASA special publication 179, "The Book of Mars" [i] and the references therein provide a useful guide to the scientific and historical significance of these early observations. Mariner 4, followed by Mariners 6 and 7 in 1969 were all flyby missions yielding only brief looks at the surface of the planet. Mariners 8 and 9 were designed to orbit Mars taking advantage of the favorable 1971 launch window. Mariner 8 did not launch successfully. Mariner 9 arrived at Mars in October 1971 to find the planet totally obscured by a dust storm. The storm subsided and by the end of the mission, 7329 pictures of Mars had been returned to Earth, providing the first good look at the Red Planet. "The Geology of Mars" [ii] contains an excellent review of these early missions to Mars, as well as the early Soviet missions.

The two Viking spacecraft reached Mars in 1976. Each spacecraft consisted of an orbiter and a lander. Three special issues of the Journal of Geophysical Research contain a detailed account of the Viking mission. The first was published in September 1977, entitled "The Scientific Results of the Viking Project" [iii]. The second consists of the proceedings of the Second International Mars Colloquium held in January 1979 [iv]. The third is the proceedings of the Third International Mars Colloquium held in September 1981 [v].

The following Tables are adapted from a review of Mars compiled by the author and were originally published in NASA Technical Memorandum 82479, "Space and Planetary Environment Criteria Guidelines for use in Space Vehicle Development", 1982 Revision [vi].

REFERENCES

[i] S. Glasstone, The Book of Mars, NASA Science and Technical Information Division, Washington, D.C., 1968.

[ii] T.A. Mutch, et al., The Geology of Mars, Princeton University Press, Princeton, N.J., 1976.[iii] AGU, The Scientific Results of the Viking Project, American Geophysical Union, Washington

D.C., 1977.[iv] AGU, Proceedings of the Second International Mars Colloquium, held in January, 1979,

American Geophysical Union, 1979.[v] AGU, Proceedings of the Third International Mars Colloquium, held in September 1981,

American Geophysical Union, 1982.[vi] NASA, Space and Planetary Environment Criteria Guidelines for use in Space Vehicle

Development, NASA Technical Memorandum 82479, 1982.


Table A.1: Dynamical Properties

Parameter Value Comments

Semi-major axis 22.794 × 107 km 1.523691 AU

Perihelion distance 20.665 × 107 km 1.381398 AU

Aphelion distance 24.918 × 107 km 1.666984 AUEccentricity 0.093387 Earth: 0.017Orbit Inclination 1¡ 50' 59.28"Mean Orbital Velocity 24.129 km sec-1

Sidereal year 686.97964 daysSidereal day 24h 37m 22.663±0.002s

Solar day (1 "sol") 24h 39m 35.238s noon to noon

Synodic period 779.94657 days time between Earth-Marsoppositions

Obliquity of rotation axis 25 deg Earth: 23.5 degLongitude of perihelionfrom vernal equinox 253 deg Epoch 1980Earth-Mars oppositiondistance: max 10.1 × 107 km

min 5.6 × 107 km

Table A.2: Physical Data

Parameter Value CommentsRadius Equatorial Polar

3397.2 km3375.5 km

Mass 6.418 × 1023 kg 0.1074 that of EarthMass Ratio: Sun/Mars 3098700.Mean Density 3.933 g cm-3 Earth: 5.41 g cm-3

Gravity at surface 372.52 cm sec-2 Earth: 980. cm sec-2

Escape velocity 5.024 km sec-1 Earth: 11.2 km sec-1

Flattening Dynamic Optical

0.005220.00612

Earth: 0.00335

GM 42828.32 km3 sec-2

J2 0.00196 Earth: 0.001083

Moment of inertia parameter

0.365 (I / MR2)

Magnetic dipole moment < 1022 G cm3

Direction of rotation axis RA 317.340±0.003 degDec 57.710±0.002 deg

(1976 epoch)

Normal albedo 0.1 to 0.4Surface temperature 130 to 300¡K


extremesSurface atmospheric pressure

5.9 to 15.0 mb varies seasonally


Table A.3: Mars Opposition Distances through 2050

Date Distance (106 km) Mars SeasonAerocentric

Solar LongitudeNorth

January 7, 1993 94 Summer 22February 12, 1995 101 Summer 58March 17, 1997 99 Spring 91April 24, 1999 87 Spring 128June 13, 2001 68 Spring 177August 29, 2003 56 Autumn 247November 7, 2005 70 Winter 317December 24, 2007 89 Summer 7January 30, 2010 99 Summer 45March 3, 2012 101 Summer 78April 8, 2014 93 Spring 113May 22, 2016 76 Spring 156July 26, 2018 58 Autumn 216October 13, 2020 63 Winter 291December 8, 2022 82 Winter 350January 15, 2025 96 Summer 30February 20, 2027 101 Summer 65March 24, 2029 97 Spring 98May 3, 2031 84 Spring 137June 28, 2033 64 Autumn 190September 16, 2035 57 Autumn 264November 19, 2037 75 Winter 329January 3, 2040 92 Summer 16February 6, 2042 100 Summer 52March 11, 2044 100 Summer 85April 17, 2046 90 Spring 121June 4, 2048 72 Spring 168August 14, 2050 56 Autumn 233

Table A.4: Characteristics of Phobos and Deimos

Phobos DeimosOrbital Elements Semi-major axis 9378 km (2.76 RMars) 23459 km (6.90 RMars)

Eccentricity 0.015 0.00052 Inclination (deg) 1.02 1.82 Sidereal period 7h 39m 13.85s 30h 17m 54.87s

Physical Parameters Longest axis 13.5 km 7.5 km Intermediate axis 10.7 km 6.0 km Shortest axis 9.6 km 5.5 km Rotation synchronous synchronous


Density 2.0 g cm-3 1.9 g cm-3

Mass 9.8 × 1018 g 2.0 × 1018 g Albedo 0.05 0.06 Surface Gravity 1 cm sec-2 0.5 cm sec-2


Table A.5: Elemental Composition of the Viking 1 Lander Site

Element Percent by MassMg 5.0 ± 2.5Al 3.0 ± 0.9Si 20.9 ± 2.5S 3.1 ± 0.5Cl 0.7 ± 0.3K <0.25Ca 4.0 ± 0.8Ti 0.51 ± 0.2Fe 12.7 ± 2.0L* 50.1 ± 4.3

X** 8.4 ± 7.8Rb <30 ppmSr 60 ± 30 ppmY 70 ± 30 ppmZr <30 ppm

* L is the sum of all elements not directly determined.** If the detected elements are all present as their common oxides

(Cl excepted) then X is the sum of components not directlydetected, including H2O, NaO, CO2, and NOx.

Table A.6: Chemistry of the Viking 1 Lander Site

Compound Percent MassSiO2 44.7

Al2O3 5.7

Fe2O3 18.2

MgO 8.3CaO 5.6K2O <0.3

TiO2 0.9

SO3 7.7

Cl 0.7sum 91.8


Table A.7: Properties of the Mars Top-Regolith*

Parameter Nominal ValueThermal Conductivity 2 to 20 × 10-5 cal sec-1 cm-1 K-1

Specific Heat 0.15 to 0.19 cal g-1 K-1

Emissivity 0.90 to 0.98

Thermal Inertia 100 to 600 cm2 sec1/2 K/cal: (k ρ c)-1/2

Albedo 0.2 to 0.4Bolometric Albedo 0.43 to 0.93*Dielectric Constant 2.3 to 3.5Bulk Density (porosity) 1 to 1.8 g cm-3

Penetration Resistance 0.3 N cm-2 cm-1

Cohesion 0.01 to 0.1 N cm-2

Adhesion 10-4 to 10-3 N cm-2

Coefficient of Sliding Friction 0.55 to 0.65Density 3.933 g cm-3

*Equatorial Regions

Table A.8: Comparison of Viking 1 Landing Site and Lunar Soil Properties

Mars (Viking 1) Lunar DepthProperty* Sandy Rocky Rocky Flats 0 to 0.01 m 0.1 to 3 m

Bulk density (porosity)(g cm-3) 1 to 1.6 1.8 1.0 to 1.3 1.5 to 2.1

Particle size(surface and near surface)

10 to 100 µm (%)100 to 2000 µm (%)

6010

3030

30 to 6030 to 35

Angle of internal friction (deg) 20 to 40 40 to 45 35 to 50Penetration resistance

(dyne/cm2/cm)3 × 104 6 × 105 3 x 105

Cohesion (dyne/cm2) 103 to 104 104

Adhesion (dyne/cm2) 101 to 102 102 to 103

Coefficient of sliding friction 0.55 to 0.65 0.5 to 1* Soil properties deduced from Viking 1 data. Lunar soil is included for comparison and because the nominal engineering design soil model was based on the lunar soil.

Table A.9: Composition of the Martian Lower Atmosphere

Gas Percent VolumeCarbon Dioxide (CO2) 95.32 %

Nitrogen (N2) 2.7 %

Argon (Ar) 1.6 %Oxygen (O2) 0.13 %


Carbon Monoxide (CO) 0.07 %Water Vapor (H2O) 0.03 % (variable)

Neon (Ne) 2.5 ppmKrypton (Kr) 0.3 ppmXenon (Xe) 0.08 ppm


Table A.10: Summer, Mid-Latitude, Daily-Mean Atmosphere of Mars (Cool and Warm Models)

Cool, Low Pressure Model Warm, High Pressure Model

x, km T, ¡K p, mb ρ, kg/m2 p/p0 T, ¡K p, mb ρ, kg/m2 p/p0

0 204 5.9 1.51×10-2 1.000 224 7.8 1.82×10-2 1.000

4 204 4.03 1.03 0.683 224 5.51 1.29 0.706

8 199 2.74 7.20×10-3 0.464 219 4.09 9.77×10-3 0.524

12 191 1.84 5.04 0.312 211 2.85 7.07 0.366

16 185 1.22 3.45 0.207 205 1.97 5.01 0.252

20 178 7.96×10-1 2.34 0.135 198 1.34 3.54 0.172

24 173 5.13 1.55 8.70×10-2 193 9.03×10-1 2.45 0.116

28 168 3.27 1.02 5.54 188 6.03 1.68 7.73×10-2

32 163 2.06 6.60×10-4 3.49 183 3.99 1.14 5.11

36 158 1.28 4.23 2.17 178 2.61 7.67×10-4 3.35

40 152 7.81×10-2 2.69 1.32 172 1.69 5.13 2.16

44 148 4.70 1.66 7.96×10-3 168 1.08 3.36 1.38

48 144 2.79 1.01 4.73 164 6.83×10-2 2.18 8.75×10-3

52 140 1.64 6.12×10-5 2.78 160 4.28 1.40 5.48

56 137 9.49×10-3 3.62 1.61 157 2.65 8.84×10-5 3.40

60 134 5.44 2.12 9.22×10-4 154 1.63 5.55 2.09

64 132 3.09 1.22 5.23 152 9.99×10-3 3.44 1.28

68 130 1.74 7.01×10-6 2.95 150 6.08 2.12 7.79×10-4

72 129 9.76×10-4 3.96 1.65 149 3.68 1.29 4.72

76 129 5.47 2.22 9.27×10-5 149 2.23 7.83×10-6 2.86

80 129 3.07 1.24 5.20 149 1.35 4.75 1.73

84 129 1.72 6.99×10-7 2.92 149 8.21×10-4 2.88 1.05

88 129 9.70×10-5 3.93 1.64 149 4.99 1.75 6.39×10-5

92 129 5.46 2.22 9.26×10-6 149 3.03 1.07 3.69

96 129 3.08 1.25 5.22 149 1.85 6.49×10-7 2.37

100 129 1.74 7.00×10-8 2.95 149 1.13 3.96 1.44


Table A.11: Isotope Ratios in Atmospheric Gases

Ratio Mars Earth12C / 13C 90 89

16O / 18O 500 499

14N / 15N 165 277

40Ar / 36Ar 3000 292

129Xe / 132Xe 2.5 0.97

Table A.12: Meteorological Properties

Parameter Nominal Value Note or RangePressure 8 mb (at lowest point

on surface)7 to 9 mb

Temperature 215¡K 130 to 290¡KTemperature Lapse Rate 2¡K km-1

Adiabatic Lapse Rate 4.5¡K km-1

Scale Height 11 kmTropopause Height 40 kmTurbopause Height 120 kmWind Speed 0 to 50 m sec-1 above boundary layer

Solar Radiation mean 590.0 W m-2 based on the solar perihelion 718.0 W m-2 constant at 1 AU of apehelion 493.0 W m-2 1371 ± 5 W m-2

Albedo average 0.2 to 0.4 ice caps 0.7Solar UV Flux 104 erg cm-2 sec-1 200 to 300 nm, top of

atmosphere, subpolarpoint, perihelion.

Table A.13: Durations of Seasons on Mars

Season LengthNorthern

HemisphereSouthern

HemisphereDays Sols

spring autumn 199 194summer winter 183 178autumn spring 147 143winter summer 158 154

687 669


Appendix BINTERNATIONAL EXPLORATION OF MARS SURVEY - c1992

by Gerald J. Smith and Edward Barrett

A questionnaire was circulated to members of the IAA to research the membership's views on a proposed international mission for Mars exploration. A preliminary, expanded questionnaire was initially distributed to a few select individuals who were asked to answer the questions and give comments on the format of the survey. These individuals were not necessarily experts on Mars or space missions, so their comments on the questionnaire were distanced enough to provide an objective perspective. A total of 22 completed preliminary questionnaires were received. With this knowledge the present questionnaire, described herein, was developed as a survey of the IAA membership, and was hopefully simpler to understand than it might have been otherwise.

Over 119 completed questionnaires were received and tabulated. The initial tabulation separated the answers by occupational status and by overall answers. A total of 35 completed questionnaires were received from members in the United States, 11 from Germany, 10 from Russia, 9 from France, 8 from Japan, 6 from United Kingdom, 5 from Peoples Republic of China, 4 from Italy, 3 each from Bulgaria, Czechoslovakia and Yugoslavia, 2 each from Austria, Canada, Hungary, India, the Netherlands, Poland, Spain and Switzerland, and 1 each from Argentina, Australia, Belgium, Congo, Morocco and Pakistan. The possible answers to the questions were A, B, C, D, and E, with A denoting strong agreement with the statement or given answer choice, through to E denoting strong disagreement. A copy of the questionnaire follows.

Following the copy of the questionnaire is a summary of the tabulated answers. Also enclosed are Tables of the raw answers and tabulated statistics of the answers. Table B.1 shows the raw tabulation of the questionnaire answers separated by academic training. Table B.2 shows the number of replies for each answer, and the average score for each question (A=2, B=1, C=0, D=-1, and E=-2). The average score is not meaningful for some questions where the answer choices A thru E are not a smooth progression. Examining question 1A, which asks whether 'economic stimulation and benefits are an important objective or reason for Mars exploration at this time', the average answer score from all replies was 0.14, which places the average consensus at just slightly to the agreement side (B=1) of neutral (C=0). The average answer to question 1B is 0.9, which translates into an average consensus of near agreement (B=1). In addition, the absolute value of the weighted answer score was calculated (A=2, B=1, C=0, D=-1, and E=-2). When compared to the +/- weighted answer scores, this will yield an indication of the degree of common consensus among the responding members. If the 'absolute' score is within 0.5 points of the average score, then the answers are considered well correlated. Correlated answers are given a 1, poorly correlated answers are given a 0, and severely uncorrelated answers are given a -1. This is a preliminary method of analysis, but seems to work well on most of the answers. Some questions, though, must be analyzed individually. These include questions 10 and 11.

Looking first at answers with high consensus and strong agreement (score greater than 1), answers to questions 1c, 1e, 2a, 2b, 2d, 3b, 4b, 5a, 5b, 6c, 9d, 12a, 14a, 15d, and 15e fall into this category. Answer to question 4a shows a high consensus and a strong neutral position, but due to the way the question was presented can be considered as a strong agreement. Answers that show high consensus and strong disagreement (score less than -0.5) have been given for questions 6e, 8f, 9c, and 13b. Answers to questions 6a and 8e show the lowest degree of consensus (strong agreement and strong


disagreement). These answers and the answers to questions 10 and 11 are be addressed in the summary following the questionnaire.


Questionnaire of the IAA Mars Exploration Subcommittee

Name:_______________________________, Affiliation:______________________________IAA Section:_____, Country:____________________, Degree:___________________________Statesman/Lawyer, __Scientist, __Engineer, __Businessman, Other _______________

The Mars Exploration Subcommittee of the Committee on International Space Plans and Policies seeks input from IAA members as it develops a plan for the International Exploration of Mars. We solicit your knowledge, comments, and opinions on the subject of Mars exploration. Please respond to the questions (multiple choice and short answer), to provide IAA member guidance as to the important issues on which to focus in the Mars Exploration Report. The Subcommittee welcomes correspondence on any and all questions and references or reports on the subject.Send the completed Questionnaire and and any other correspondence to:

Prof. George W. Morgenthaler, Chairman - IAA Mars Exploration SubcommitteeUniversity of Colorado, Campus Box 429, Boulder, CO 80309-0429 USA

Phone: 303-492-3633 FAX: 303-492-5514 Please respond to the following questions by circling the appropriate letter, where

A = strongly agree, B = agree, C = neutral, D = disagree, E = strongly disagree.Write in additional comments on issues at the end of the questionnaire or in margins.

1) Which are the important objectives or reasons for Mars exploration at this time?a) Economic stimulation/benefits? A B C D Eb) Sociology, Human Adventure and societal development? A B C D Ec) Scientific? (rank the science areas below in order of priority) A B C D E

__Search for Life?, __Planetology?, __Atmospheric?, __Astrophysics?d) Contribute to world peace (by replacing the "Cold War", etc.)? A B C D Ee) Technological development? A B C D Ef) Ultimate colonization? A B C D E

2) Why International Mars Exploration?a) Combined international expertise to ensure mission success? A B C D Eb) Economic - cost spread among participants? A B C D Ec) Benefits from completed mission rapidly shared worldwide? A B C D Ed) Improve communication and understanding among nations? A B C D E

3) If we do not commit to Mars Exploration in our lifetime we shall seriously impede:a) Physical and planetary science? A B C D Eb) Space exploration momentum? A B C D Ec) Unified world project? A B C D Ed) Life science developments? A B C D Ee) Economic growth? A B C D E

4) The Exploration of Mars mission should be:a) A=crew only, C=crew + robotic, E=no crew (robotic only)? A B C D Eb) aimed at a series of scientific exploration visits? A B C D Ec) aimed at exploitation of resources? A B C D Ed) aimed at permanent-inhabitated Martian bases? A B C D E

5) Which main precursor missions should be stressed, assuming crew+robotic?a) Orbiter mapper? A B C D Eb) Planetary rover? A B C D Ec) Surface sample return? A B C D Ed) Lunar base? A B C D E


e) Mars moon (Phobos, Deimos) base? A B C D E6) How should the initial International Mars missions carrying a crew be focused?

a) "Fly-by" or orbital only, with later missions making landfall? A B C D Eb) Land on Martian moon (Phobos, Deimos)? A B C D Ec) Land on Martian surface? A B C D Ed) Establish scientific base? A B C D Ee) Establish colony? A B C D E


7) Acceptable risks for the human exploration of Mars are:a) use of nuclear propulsion to shorten trip. A B C D Eb) employing a single exploration/return vehicle. A B C D E c) reliance on a fully regenerative life support system. A B C D Ed) effects of long-term weightlessness (no artificial gravity). A B C D E

8) The first crewed Mars Exploration Mission should be undertaken:a) As soon as possible and prior to 2015? A B C D Eb) Not before 2030? A B C D Ec) Not before an Earth space station is established? A B C D Ed) Not before a lunar base is established? A B C D Ee) Whenever humanity feels ready; don't force the issue? A B C D Ef) Not in the lives of the present generations? A B C D E

9) What will be the result of the first successful human surface mission to Mars?a) Elation and determination to establish a permanent Mars base? A B C D Eb) Elation, but as the "Australian" saying ("Been there, done that")? A B C D Ec) A great let-down and confusion as to future exploration goals? A B C D Ed) Depends entirely on the results found? A B C D E

10) What is the best way to accomplish the International Mars Exploration?A= ESA Model - an international Mars Exploration Agency, funded

by all participating nations, with ability to sub-contract out.B= Private Company Model - an international private space exploration

foundation, which can sell shares in Mars enterprises.C= Space Station Freedom Model - a few space-faring nations band

together to provide major sub-systems on special projects.D= International Space Exploration Institute - "think tank" provides

scientific, technical, political, and economic expertise.E= Organized and sponsored by the United Nations? A B C D E

11) Rescue contingencies for Mars Exploration missions should be developed for:A= Interplanetary travel phase?B= In Mars orbit also?C= From Mars surface also?D= All of the aboveE= None of the above (explorers take risk)? A B C D E

12) What is the current state of technology for Mars Exploration?a) Ready for unmanned exploration only? A B C D Eb) Life Support / EVA systems not ready? A B C D Ec) Propulsion systems not ready? A B C D Ed) Power systems not ready? A B C D E

13) What % of Gross National Product should be expected for Aerospace and Space Exploration? Present % GNP's for USA, ESA member states, and Japan are <0.10%.a) A = <0.10%, B = 0.25%, C = 0.50%, D = 1%, E = >2% of GNP?A B C D Eb) 0% GNP, fund through private industry and contributions? A B C D E

14) What % of participant's Space budgets should be expected for Mars Exploration?a) A = < 10%, B = 25%, C = 50%, D = 75%, E = > 90%? A B C D E

15) Rules, Regulations and Legal Considerations (indicate agreement):a) Natural resources should be used on Mars only, for planetary

exploration, and not for profitable exportation? A B C D Eb) Mars orbit location should be considered a natural resource, analogous to the

international legal regime governing geostationary orbit use?A B C D E


c) Profitable exploitation (resource exportation to Earth) should be emphasized over research and an increase in knowledge of the Universe? A B C D E

d) National and international laws governing activities relating toMars shold be harmonized and coordinated? A B C D E

e) Rules concerning human settlements on Mars should be formulated before the trip to ensure maintenance of life and productivity. A B C D E

Other choices and comments?___________________________________________________


STATEMENTS WITH AGREEMENT OR STRONG AGREEMENT:(% agreement given)¥ An important objective or reason for Mars exploration at this time is scientific (92%) and

technological development (88%).

¥ The reasons for an international Mars exploration effort are: economic - cost spread among participants (85%), combined international expertise to ensure mission success (83%), and improve communication and understanding among nations (78%).

¥ If we do not commit to Mars exploration in our lifetime, we shall seriously impede space exploration momentum (82%).

¥ The exploration of Mars should be crew + robotic (80%).

¥ The exploration of Mars mission should be aimed at a series of scientific exploration visits (93%).

¥ Assuming crew + robotic missions are available, the main precursor missions which should be stressed are an orbiter mapper mission (86%) and a planetary rover mission (81%).

¥ The initial international Mars missions carrying crew should be focused on landing on the Martian surface (76%).

¥ The result of the first successful human surface mission to Mars will depend entirely on the results found (79%).

¥ The current state of technology for Mars exploration is ready for robotic exploration only (81%).

¥ The expected percentage of participants' space budgets for the exploration of Mars are less than 25 percent (82%).

¥ National and international laws governing activities relating to Mars should be harmonized and coordinated (95%).

¥ Rules concerning human settlements on Mars should be formulated before the trip to ensure maintenance of life and productivity (73%).


STATEMENTS WITH DISAGREEMENT OR STRONG DISAGREEMENT:(presented as statement disagreed with - the corresponding statement agreed with is in [ ])¥ The initial international Mars missions carrying crew should be focused on establishing a colony

(70%).[Respondents suggest that we do not attempt to colonize Mars on initial missions.]

¥ The first crewed Mars exploration mission should be undertaken not in the lives of the present generations (68%).[Respondents suggest that we prepare now to undertake a crewed Mars mission soon.]

¥ The result of the first successful human surface mission to Mars will be a great let-down and confusion as to future space exploration goals (60%).[Respondents suggest that a let-down and confusion from successful completion of a Mars mission are not widely expected.]

¥ 0% of the Gross National Product of participating countries should be expected for Aerospace and Space exploration (82%).[Respondents suggest that space exploration funding from governments is expected.]

STATEMENTS WITH LOW CONSENSUS - BI-MODAL RESPONSES:(agreement % / disagreement %)¥ The initial international Mars missions carrying crew should be focused on fly-by or orbital only,

with later missions making landfall (37% / 43%).

¥ The first crewed Mars exploration mission should be undertaken whenever humanity feels ready; don't force the issue (46% / 43%).

SPECIAL ANSWERS¥ The preferred organizational path to accomplish the international Mars exploration is with the

ESA model - an international Mars Exploration Agency, funded by all participating nations, with the ability to sub-contract projects out. (53% of respondents support this organizational path.)

¥ The second favored organizational system is the Space Station Freedom model - a few space-faring nations band together to provide major sub-systems on special projects. (24% of respondents support this organizational path.)

¥ A majority of responses prefer that no special and significant rescue contingency plans be developed for Mars exploration missions. (38% of respondents support this plan.)

¥ In close second, many responses prefer that rescue contingency plans be developed for all phases of Mars exploration missions. (35% of respondents support this plan.)


Table B.1: Tabulation of IAA International Mars Exploration Questionnaire(by academic training of respondent)

ENGINEERS SCIENTISTS LAWYERS OTHERS? A B C D E A B C D E A B C D E A B C D E1A 4 15 14 12 4 3 12 17 11 2 1 4 2 1 0 1 4 3 0 11B 13 21 13 3 1 18 20 9 2 1 1 3 0 3 1 5 3 2 0 01C 19 23 5 1 0 32 10 2 0 0 7 1 0 0 0 3 7 0 0 01D 10 11 15 7 3 10 14 13 6 1 3 4 1 0 0 5 1 2 1 21E 22 24 3 0 0 19 19 7 1 0 2 4 2 0 0 4 5 1 0 01F 4 10 15 6 12 3 12 17 7 6 2 2 1 1 2 2 4 1 1 22A 15 18 11 1 0 28 13 4 1 0 8 0 0 0 0 5 3 2 0 02B 22 18 8 2 1 26 14 5 1 0 7 1 0 0 0 5 5 0 0 02C 9 21 21 1 1 14 22 8 1 0 2 4 2 0 0 4 4 2 0 02D 15 19 11 3 0 26 13 5 0 0 4 3 1 0 0 5 1 4 0 03A 5 28 12 3 2 16 18 7 4 1 1 3 4 0 0 1 5 4 0 03B 14 25 6 2 2 13 23 8 1 1 4 4 0 0 0 4 6 0 1 03C 11 10 22 3 3 7 17 16 6 1 1 2 3 2 0 4 2 2 2 03D 4 14 14 9 5 5 13 18 9 2 1 3 3 1 0 2 3 4 1 03E 4 13 12 11 6 5 6 16 12 6 0 2 4 1 0 0 1 6 1 24A 3 1 37 0 4 5 1 34 2 3 0 2 5 0 1 0 0 10 0 04B 22 25 2 1 0 23 19 4 1 0 3 5 0 0 0 4 6 0 0 04C 4 15 13 9 5 2 13 15 13 2 2 3 1 2 0 0 3 5 1 04D 5 8 18 10 6 6 18 14 4 5 2 4 0 0 2 2 3 2 2 15A 24 17 8 0 0 27 13 3 2 0 4 3 1 0 0 6 2 2 0 05B 19 23 6 1 0 17 20 8 0 1 2 4 1 0 0 4 2 3 0 15C 16 17 12 3 2 21 14 6 3 2 2 5 1 0 0 2 2 3 1 25D 20 11 15 4 1 19 14 10 2 1 3 4 0 0 0 2 2 4 1 15E 4 10 20 10 6 5 11 17 10 2 2 3 2 0 0 2 3 2 1 26A 10 8 9 12 7 9 7 6 14 9 2 2 4 0 0 1 1 3 1 36B 5 9 21 4 6 2 12 14 12 3 0 6 1 0 0 2 0 4 2 16C 19 17 9 2 2 21 17 4 3 2 1 4 2 0 0 3 3 2 1 06D 4 20 12 8 3 4 19 12 8 3 2 3 2 1 0 2 1 2 2 26E 2 1 10 13 20 2 3 9 11 22 2 1 1 3 0 1 0 3 1 47A 20 14 6 4 5 19 13 4 5 4 3 5 0 0 0 6 3 0 0 17B 8 10 17 6 7 7 20 11 8 1 0 4 3 0 0 1 2 2 2 17C 6 22 16 3 4 10 22 10 4 0 1 4 2 0 0 1 4 1 2 27D 7 15 15 8 2 8 19 13 5 1 1 3 1 2 0 1 4 3 2 08A 19 9 8 13 1 15 8 13 8 4 4 1 2 1 0 4 2 2 0 28B 7 9 11 10 8 2 8 9 15 8 0 0 2 5 0 0 1 3 2 38C 18 12 8 7 4 12 12 14 4 3 0 4 0 1 2 3 3 2 1 18D 9 14 13 7 4 14 15 12 2 3 0 5 2 0 0 1 7 0 1 18E 12 7 7 14 5 12 12 4 9 5 0 1 0 4 1 1 2 1 3 38F 1 0 14 15 13 1 2 11 13 17 0 0 2 3 2 0 0 2 2 69A 7 14 11 8 5 9 14 11 7 1 1 5 0 1 0 2 0 5 0 19B 0 10 13 9 10 2 11 10 12 4 0 0 3 3 1 0 1 2 4 19C 1 1 14 15 10 1 2 9 14 10 0 0 3 1 3 0 1 2 4 29D 20 18 7 4 2 19 17 3 4 1 4 4 0 0 0 2 5 2 0 110A 21 0 13 8 5 32 1 9 3 6 5 0 1 1 1 4 0 5 1 0


Table B.1 (cont'd): Tabulation of IAA International Mars Exploration Questionnaire

ENGINEERS SCIENTISTS LAWYERS OTHERS? A B C D E A B C D E A B C D E A B C D E11A 5 2 4 16 23 9 5 2 13 15 1 0 0 7 0 1 0 0 3 412A 20 20 1 6 1 22 13 5 3 0 1 6 1 0 0 3 3 1 2 012B 11 14 8 12 2 11 16 8 4 0 0 4 3 0 0 2 4 1 2 012C 11 15 8 8 3 8 17 9 8 4 0 4 2 0 0 3 3 2 1 012D 8 16 9 13 3 5 12 13 10 2 2 1 4 0 0 2 4 1 2 013A 15 23 5 4 0 18 12 4 7 1 4 2 0 0 0 0 6 1 3 013B 1 3 3 13 13 2 3 2 8 18 0 0 0 3 3 0 0 0 2 514A 14 24 5 0 2 23 14 9 1 0 4 3 1 0 0 0 7 2 0 015A 11 14 9 11 3 20 6 6 8 3 2 2 0 1 2 0 1 4 3 115B 16 13 15 2 3 18 14 5 3 4 3 3 0 1 0 3 6 1 0 015C 5 9 7 17 12 3 4 7 12 15 0 0 2 3 2 0 0 3 4 315D 25 21 3 0 0 28 15 1 0 0 5 2 0 0 0 4 5 0 1 015E 19 16 9 3 2 19 18 4 5 0 2 1 3 1 0 4 3 2 1 0


Table B.2: Replies and Average Scores for Each Question(by academic training of respondent)

ANSWERS: AVERAGE (A=2,B=1,C=0,D=-1,E=-2)

ABSOLUTE (A=2,B=1,C=0,D=1,E=2) CORR

?/REPLIES ALL ENG SCI LAW OTH ALL ENG SCI LAW OTH1A 111 0.14 0.06 0.07 0.63 0.44 0.82 0.88 0.73 0.88 0.89 01B 119 0.90 0.82 1.04 0.00 1.30 1.13 1.02 1.20 1.25 1.30 11C 110 1.47 1.25 1.68 1.88 1.30 1.49 1.29 1.68 1.88 1.30 11D 109 0.55 0.39 0.59 1.25 0.55 1.03 0.96 0.95 1.25 1.45 11E 113 1.28 1.39 1.22 1.00 1.30 1.30 1.39 1.26 1.00 1.30 11F 110 -0.08 -0.26 -0.02 0.13 0.30 0.99 1.02 0.82 1.38 1.30 02A 109 1.32 1.04 1.48 2.00 1.30 1.36 1.09 1.52 2.00 1.30 12B 115 1.33 1.14 1.41 1.88 1.50 1.42 1.29 1.46 1.88 1.50 12C 116 0.91 0.68 1.09 1.00 1.20 0.97 0.79 1.13 1.00 1.20 12D 110 1.21 0.96 1.48 1.38 1.10 1.26 1.08 1.48 1.38 1.10 13A 114 0.76 0.62 0.96 0.63 0.70 0.99 0.90 1.22 0.63 0.70 13B 114 1.04 0.96 1.00 1.50 1.18 1.21 1.20 1.13 1.50 1.36 13C 114 0.49 0.47 0.49 0.25 0.80 0.86 0.84 0.83 0.75 1.20 13D 111 0.21 0.07 0.21 0.50 0.60 0.82 0.89 0.77 0.75 0.80 03E 108 -0.12 -0.04 -0.18 0.14 -0.40 0.86 0.96 0.89 0.43 0.60 04A 108 0.02 -0.02 0.07 0.00 0.00 0.35 0.33 0.42 0.50 0.00 14B 115 1.37 1.36 1.36 1.38 1.40 1.40 1.40 1.40 1.38 1.40 14C 108 0.10 0.09 0.00 0.63 0.22 0.82 0.91 0.76 1.13 0.44 04D 112 0.17 -0.09 0.34 0.50 0.30 0.96 0.85 0.94 1.50 1.10 05A 112 1.38 1.33 1.44 1.38 1.40 1.42 1.33 1.53 1.38 1.40 15B 112 1.14 1.22 1.13 1.14 0.80 1.23 1.27 1.22 1.14 1.20 15C 114 0.89 0.84 1.07 1.13 0.10 1.22 1.12 1.37 1.13 1.10 15D 114 0.93 0.88 1.04 1.43 0.30 1.16 1.12 1.22 1.43 0.90 15E 112 0.11 -0.08 0.16 1.00 0.20 0.84 0.80 0.78 1.00 1.20 06A 108 -0.03 0.04 -0.16 0.75 -0.44 1.18 1.17 1.27 0.75 1.11 -16B 104 0.07 0.07 -0.05 0.86 0.00 0.80 0.78 0.79 0.86 0.89 06C 112 1.03 1.00 1.11 0.86 0.89 1.28 1.24 1.40 0.86 1.11 16D 110 0.29 0.30 0.28 0.75 -0.11 0.93 0.89 0.89 1.00 1.22 06E 109 -0.93 -1.04 -1.02 0.29 -0.78 1.28 1.26 1.32 1.14 1.22 17A 112 0.91 0.82 0.84 1.38 1.30 1.43 1.39 1.42 1.38 1.70 07B 110 0.31 0.13 0.51 0.57 0.00 0.93 0.96 0.94 0.57 1.00 07C 114 0.59 0.45 0.83 0.86 0.00 0.96 0.88 1.00 0.86 1.20 17D 110 0.47 0.36 0.61 0.43 0.40 0.89 0.87 0.91 1.00 0.80 18A 116 0.59 0.64 0.46 1.00 0.60 1.21 1.24 1.13 1.25 1.40 08B 103 -0.33 -0.07 -0.45 -0.71 -0.78 1.03 1.09 1.02 0.71 1.00 08C 111 0.58 0.67 0.58 -0.14 0.60 1.17 1.29 1.02 1.29 1.20 08D 110 0.57 0.36 0.76 0.71 0.60 1.05 1.00 1.11 0.71 1.20 18E 103 0.14 0.16 0.40 -0.83 -0.50 1.26 1.22 1.31 1.17 1.30 -18F 104 -0.99 -0.91 -0.98 -1.00 -1.40 1.11 1.00 1.16 1.00 1.40 19A 102 0.40 0.22 0.55 0.86 0.25 0.99 1.02 0.98 1.14 0.75 09B 96 -0.35 -0.45 -0.13 -0.71 -0.63 0.90 0.93 0.90 0.71 0.88 09C 93 -0.82 -0.78 -0.83 -1.00 -0.78 0.99 0.93 1.06 1.00 1.00 19D 113 1.04 0.98 1.11 1.50 0.70 1.33 1.29 1.39 1.50 1.10 110A 116 0.76 0.51 0.98 0.88 0.70 1.40 1.28 1.57 1.63 0.90 0


Table B.2 (cont'd): Replies and Average Scores for Each Question

ANSWERS: AVERAGE (A=2,B=1,C=0,D=-1,E=-2)

ABSOLUTE (A=2,B=1,C=0,D=1,E=2)

CORR

?/REPLIES ALL ENG SCI LAW OTH ALL ENG SCI LAW OTH11A 110 -0.76 -1.00 -0.45 -0.63 -1.13 1.47 1.48 1.50 1.13 1.63 012A 108 1.12 1.08 1.26 1.00 0.78 1.36 1.42 1.40 1.00 1.22 112B 102 0.63 0.43 0.87 0.57 0.67 1.06 1.11 1.08 0.57 1.11 112C 106 0.49 0.51 0.37 0.67 0.89 1.08 1.13 1.07 0.67 1.11 012D 107 0.30 0.27 0.19 0.71 0.67 0.95 1.04 0.86 0.71 1.11 013A 105 0.96 1.04 0.93 1.67 0.30 1.27 1.21 1.36 1.67 0.90 113B 79 -1.16 -1.03 -1.12 -1.50 -1.71 1.47 1.33 1.55 1.50 1.71 114A 109 1.15 1.07 1.26 1.38 0.78 1.24 1.24 1.30 1.38 0.78 115A 107 0.45 0.40 0.74 0.14 -0.44 1.21 1.10 1.40 1.57 0.67 015B 110 0.87 0.76 0.89 1.14 1.20 1.24 1.08 1.39 1.43 1.20 115C 108 -0.66 -0.44 -0.78 -1.00 -1.00 1.19 1.20 1.27 1.00 1.00 015D 110 1.51 1.45 1.61 1.71 1.20 1.53 1.45 1.61 1.71 1.40 115E 112 1.00 0.96 1.11 0.57 1.00 1.25 1.24 1.33 0.86 1.20 1


Appendix CINTERNATIONAL SPACE EXPLORATION INSTITUTE

International Academy of AstronauticsSecretariat, 6 Rue GalilŽe, 75016 Paris, France


Appendix DADDITIONAL BIBLIOGRAPHY ON EXPLORATION OF MARS

The following bibliography has been provided by Marcia Smith (U.S. Library of Congress), Michael Duke (NASA Johnson Space Center), and other participants. It is intended as a helpful reference in addition to the references used in the Report, and is not intended to be a complete list of Mars references.

Edwin Aldrin, "The Mars Transit System", Air & Space, pp. 41-42, Oct./Nov., 1990.

Faren Akins, Mary Conners and Albert Harrison, Living Aloft: Human Requirements for Extended Spaceflight, NASA SP-483, NASA, Washington, 1985.

American Geophysical Union, Scientific Results of the Viking Project, American Geophysical Union, Washington, 1977.

American Institute of Aeronautics and Astronautics, Final Report to the office of Aeronautics, Exploration and Technology, National Aeronautics and Space Administration on Assessment of Technologies for the Space Exploration Initiative (SEI), AIAA, Washington, 1990.

S. Aroesty, R. Zimmerman and J. Logan, "Human Support Issues and Systems for the Space Exploration Initiative": Results From Project Outreach, Rand Report N-3287-AF/NASA, 1991.

Raymond E. Arvidson, et al., "The Surface of Mars", Scientific American, Vol. 238, pp. 76-77, 80-89, March, 1978. Isaac Asimov, "Is Mars Alive?", Saturday Review, Vol. 3, pp. 14-16, 18-19, May 1, 1976.

R.M. Batson and J.L. Inge (eds.), Atlas of Mars: the Viking Global Survey, National Aeronautics and Space Administration, Washington, 1992.

Gary L. Bennett, Richard J. Hemler, and Alfred Schock, "Status Report on the U.S. Space Nuclear Program", IAF-95-R.1.03, presented at 46th International Astronautical Congress, Oslo, Norway, Oct. 2-6, 1995.

Boeing Missiles & Space Advanced Civil Space Systems, Planetary Manned Exploration Performance Analysis Study, "Mars Basing" Vol. I - Technical, D615-18010, June, 1991.

S.K. Borowski and S.W. Alexander, "Fast Track NTR System Assessment for FLO", AIAA-92-3812, July, 1992.

Penelope Boston (ed.), The Case for Mars: Proceedings of a Conference Held April 29-May 2, 1981, Vol. 57, American Astronautical Society, Univelt, San Diego, c1984.

Ray Bradbury, et al., Mars and the Mind of Man, Harper & Row, New York, 1973.

R.D. Braun, R. Powell, and J.E. Lyne, "Earth Aerobraking Strategies for Manned Return from Mars", AIAA Paper 91-2873.


British Interplanetary Society, "Human Exploration of Mars", Journal of the British Interplanetary Society, Nov., 1990.

Michael H. Carr, "The Geology of Mars", American Scientist, Vol. 68, pp. 626-635, Nov.-Dec. 1980. Andrew Chaikan, "The Case for Life on Mars", Air & Space, Vol. 5, pp. 63-71, Feb.-Mar. 1991.

Carl Q. Christol, "The Moon and Mars Missions: Can International Law Meet the Challenge?", Journal of Space Law, v. 19, 1991: 123-135.

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