stepping stones: economic analysis of space transportation

72
Stepping Stones: Economic Analysis of Space Transportation Supplied From NEO Resources - Summary of Preliminary Results - PI: Joel C. Sercel, PhD TransAstra Corporation Winter 2016 Summary Presentation on Grant No NNX16AH11G Funded Under Economic Research for Space Development Technical Officer: Lynn D. Harper PhD

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!Stepping Stones: Economic Analysis of Space Transportation Supplied From NEO Resources!

- Summary of Preliminary Results -!!!!!!!

PI: Joel C. Sercel, PhD!TransAstra Corporation !

Winter 2016

Summary Presentation on Grant No NNX16AH11G Funded Under Economic Research for Space

Development!Technical Officer: Lynn D. Harper PhD

FISO Telecon Presentation8/16/17

A Framework for Considering Options!!

Not a Set of Answers!!

Today: Highlights of a Study of Broad Scope

- 3 -

Coauthors

•  Study Team –  James R. French: Mission scenarios –  Craig Peterson: Study systems engineering –  Anthony Longman: Vehicle configurations and graphics

•  Review Support –  Stanley Love (Astronaut), Mission operations and human

factors –  Lynn Harper and Dan Raskey of NASA Ames –  Dr. Robert Shishko of JPL

•  Collaboration on Fontus system concept –  Dr. Christopher Dreyer of Colorado School of Mines and

colleagues

- 4 -

Where We Are, Still Today

- 5 -

Study Purpose

•  The greatest impediment to NASA human exploration program is cost. –  Cost is dominated by transportation costs, which is

dominated by the cost of launching propellant. •  Goal is self-sustaining, reusable transportation

with Apis™ (Asteroid Provided In-Situ Supplies) (Sercel 2016) –  Apis™ architecture includes new approach to asteroid

ISRU called “Optical Mining™” (Sercel 2015).

Assess the Economic Viability of Asteroid ISRU to Support NASA Human Exploration

- 6 -

Why Now? •  The rise of the billionaire visionary !

(Musk and Bezos) •  Vindication of PPP through COTS etc.… •  Agile methods proven for aerospace (e.g. SpaceX) •  Understanding of the availability of space

resources –  Low ∆V water rich NEOs –  Lunar ice close to the peaks of perpetual light

The Rush To Cislunar Space Started With Blue Origin’s Proposal to NASA

- 7 -

Mission Architecture •  Remote prospecting based on compound digital synthetic

tracking •  Fully reusable launch vehicles •  Full reusable in-space vehicles •  No single-mission-type vehicles

–  e.g.: the same lander works on Mars and Moon –  The lander is also a reusable 2nd stage system

•  All in space propellant provided from above •  Propellant depot at the top of the Earth-Moon gravity well •  Launch nothing beyond LEO or LMO

–  Payload or Propellant Transfer In low orbit from aerobraking tankers

Sutter: Breakthrough Telescope Technology !and Mission To Trigger the Gold Rush To Space

1) Theia Mission Tech Demo of Digital Synthetic Tracking (DST)

2) Sutter Survey in Heliocentric Space Finds and Prospects 100s of of HEx and ISRU Targets With Compound

Synthetic Tacking (CST)

3) Sutter Extreme Finds and Prospects 1000s of Targets/Year

PI: Joel C. Sercel, PhD TransAstra Corporation

Co-I: Robert Jedicke, PhD

Hawaii Institute for Astronomy (IfA)

- 9 -

Thermal Spalling: Key to Optical Mining™ Optical Mining™ of Asteroids, Moons, and Planets for Human Exploration and IndustrySubmitter: TransAstra Corporation PI: Joel C. Sercel, PhD

Phase II work we will use all the major components of that light source for the rapid and cost effective maturation of Optical Mining™ technology in a system we refer to as the Optical Mining™ Test Bed (OMTB).

Demonstration of Optical Mining™: The goal of the experimental effort was to perform a large scale (≈10  kW  optical) demonstration of Optical Mining™ on a kilogram scale sample of a high fide l i ty astero id simulant to show that Optical Mining™ can be used to e x c a v a t e l a r g e rocks in vacuum without the use of physical digging equipment and to obtain pract ical i n s i g h t s i n t o Optical Mining™ paving the way for f u r t h e r t e c h n o l o g i c a l maturation. This d e m o n s t r a t i o n

TransAstra Corporation - ! -3 Proprietary Information

Fig. 3: Before and After A Single Simulant from Full Scale Optical Mining™

Fig. 2 - Understanding Optical Excavation Gained From Analytical Modeling and Experimentation

- 10 -

Optical Mining™

Low Pressure Partially-Sealed

Containment Bag

Growing Excavated

Cavity

Flexible Protective Boot Contains Debris and Reflected Radiation

Rigidized Torus Primary Reflective Surface Doubles as

Sun Shield

Inflatable, Passively-Cooled Cryopump and 2nd Surface

Ice Storage Bag

Transparent Front Surface of Lenticular

Structure

Stinger-Reflector Stowed Containment Housing, Optical Louver Light-Power Flux Regulator, and

Winston Cone Not Shown

Port with Sleeve Joint

Path of Sunlight

Telescoping Penetrator With Light Tube

Inflatable Sun Shield

Secondary Reflector

Solar Thermal Rocket (STR) Thruster

Thin Film Containment Bag at ≈10-4

Encapsulated Asteroid(Restraint Net Not Shown)

Fig. 1a: Optical Mining Starts With Asteroid Capture and Despin

Fig. 1b: Excavation by Spalling and Outgassing

Fig. 1c: Volatile Products Stored as Ice

- 11 -

Honey Bee Spacecraft Configuration Honey Bee With Inflatable Bag in Asteroid Capture

Configuration

15 m Diameter Inflatable Reflector

Design Adapted from Sercel Apis™ NIAC

Study

Honey Bee™ With Asteroid Captured in

Containment Bag

Mini Bee: Compatible With SmallSat Launchers

Mini Bee: 250 kg Technology Demonstration Vehicle

4,000 kg Class Vehicle Requires Full Falcon 9 FT

- 12 -

Honey Bee Robotic Asteroid Capture for ISRU Resource Return

But First

- 15 -

Mini Bee Tech Demo Mission: Launch On A SmallSat Launcher (eg Launcher One)

- 16 -

Mini Bee Separation

- 17 -

Synthetic Asteroid and Structures Deployment

- 18 -

Synthetic Asteroid Capture and Optical Mining Demonstraton

- 19 -

Demonstration of Solar Thermal Rocket Maneuvering With Mined Propellant

Before That

- 21 -

Optical Mining Experiment Module (OMEM)

- 22 -

OMEM Interior Cutaway

- 23 -

OMEM Inflatable Deployment

- 24 -

OMEM Optical Mining Demonstration

- 25 -

Inflatable Structure Separation and Deployment

- 26 -

First Space Asteroid Mining!

Module and Mined Water Return to Earth on Dragon

But First

- 28 -

The Next Step…!The Optical Mining™ Test Bed (OMTB)

Optical Mining™ of Asteroids, Moons, and Planets for Human Exploration and IndustrySubmitter: TransAstra Corporation PI: Joel C. Sercel, PhDestimate that this will require about two months of calendar time for Dr. Sercel working a day a week to complete.

Prior to initiating full scale long duration Optical Mining™ tests and demonstrations in our Phase II NIAC work we wil l need to construct the OMTB. We have completed a preliminary design of this system to the level of all major component selections and layouts based on past designs for solar simulators, IMAX projectors, and high intensity light sources. An artist concept of the layout we have chosen for this system is provided in Fig. 11 as it will be assembled and tested in the laboratory at the CSR at CSM. A detailed listing of the required components and their costs is provided in the cost section of this proposal.

The core of the illumination system will be the Superior Quartz SX32000D high pressure short arc xenon lamp. This device is the highest rated power level light bulb made in the world today. It can operate at up to 32 kW input DC power at a max current of 700 amps and 45 volts in normal conditions. A photograph and a drawing of the bulb is provided in Fig. 12. Another key feature of the OMTB is the OptiForm E1585 high temperature elliptical reflector. This nickel reflector is from a line of reflectors made by OptiForm and used

TransAstra Corporation - ! -9 Proprietary Information

Water Cooled Elliptical Reflector

Water CooledOptical Safety

Shroud

Manual Water Cooled Backup

Shutter

Sapphire Window

Quartz Shield View Ports

AsteroidSimulant Target

Motor Driven Turntable

Up To 10 kW Convergent Beam

Existing Vacuum Chamber

With Water Cooled Shroud

Cryotrap, Diagnostics, Pumping Equipment, and Digital Control Not Shown

32 kW Xenon Arc

Lamp

700 Amp PowerSupply

Rails for Optical Zoom Motion

Coolant Manifold

Cooling Fan

≈1m

Water Cooled Elliptical Reflector

Water CooledOptical Safety

Shroud

Manual Water Cooled Backup

Shutter

Sapphire Window

Quartz Shield View Ports

AsteroidSimulant Target

Motor Driven Turntable

Up To 10 kW Convergent Beam

Existing Vacuum Chamber

With Water Cooled Shroud

Cryotrap, Diagnostics, Pumping Equipment, and Digital Control Not Shown

32 kW Xenon Arc

Lamp

30 kWPowerSupply

Rails for Optical Zoom Motion

Coolant Manifold

Cooling Fan

≈1m

Builds on Complete Theory and Dozens of Demonstrations

- 29 -

High Performance Solar Thermal Propulsion

Thorium Oxide For Flight Systems

Ceramic Foam Solar Absorber

Sapphire Window

Incoming Solar Energy

Counterflow Propellant in Channels for RegenerativeHeat Capture

Photo of Zirconia Foam Showing Penetration of Sunlight

Tangential Flow Injection In Annular

Channels At Window and Throat

ICS Associates Proprietary Informtion

Cold Radial Propellant

Injection for Window Cooling

- 30 -

High Performance Solar Thermal Propulsion

NIAC Phase II Proposal Pending

Exterior Isometric View Isometric Cutaway

Long Chamber

Design Allows Tests with

Various Replaceable Foam Inserts

Same Architecture as250 kW Design But Smaller

With Long Chamber

Throat Area Cutaway

6.5 cm

Small Expansion Ratio For Low Cost Demonstration Exhausting to 1 atm

Step Ledge For Supporting Solar Absorber inserts

Sapphire Window

Primary Propellant

Inlet

CounterflowHeat Capture

PropellantInlet Near

Throat

Radial Propellant Injection Cools

Window175$

200$

225$

250$

275$

300$

325$

350$

375$

400$

425$

1,000$ 1,500$ 2,000$ 2,500$ 3,000$ 3,500$Specific'Im

pulse'(s)'

Chamber'Temp'(Kelvin)'

Ceramic ThO2 Working Limit

Flight System Projected Performance

Low Cost Lab Demonstration Performance

Zirconia Working

Limit

- 31 -

Mission Scenarios Studied •  Lunar Orbital Outpost

–  Established in Lunar Distant Retrograde Orbit (LDRO) and operated for life of scenario

•  Human Near Earth Object (NEO) Exploration –  Focused on crewed missions to a variety of small (10 m class) targets !

(five 14 month missions) •  Lunar Surface Operations (LSO)

–  Establishment and operate a lunar surface base (two crewed and two cargo lander per year)

•  Mars Exploration –  Four crewed exploration mission to Deimos crewed Mars landing –  Return missions could lead to establishment of Deimos or surface base,

but not covered in the version of this scenario presented

•  LEO to GEO commercial satellite transportation •  Cislunar Tourism

- 32 -

Combined Mission Schedule

  Start Year Mission/Event 1 3 5 7 9 11 13 15 17 19 21

Lunar Orbital Outpost                       Establishment                       Operations                      

NEO Exploration                       Mission 1 (14 mo. Duration)                       Mission 2                       Mission 3                       Mission 4                     Mission 5                      

Lunar Surface Operations                       Site Selection and Initial Base                       Base Expansion and Occupation                      

Mars Exploration                       Mission 1 (30 mo. Duration)                       Mission 2                       Mission 3                      

•   Mars and some NEO missions staged out of LEO in Non-ISRU case. •   All other missions staged out of LDRO from Honey Bee™ supplies. -  Reusable Spaceship (all LOX-LM) picks up payloads in LEO and

delivers them to LDRO Outpost in Apis™ cases

- 33 -

Propellant Depot and Outpost Configuration

Small enclosure used for temporary habitat during outpost buildup, later for

logistics storage

Two “Scooter” enhanced EVA support units

Emergency Airlock and Suitports

Habitat Module Workshop and

Laboratory Module

Inflatable Sun Shield

Liquid Water Storage

Fontus Fluids Processing System

Cryogenic Ice, Feedstocks, and Fluids

Storage Area Tensegrity Robotic

Arm

Radiator

- 34 -

Fontus Propellant Processing System Internal Material Flow

Fontus System extracts, separates, produces, and uses multiple materials prior to liquefaction and storage of the

finished products

ISRU Volatiles, Waste Material,

and Excess

Solid Output

Fontus System

ProductsTo Users

Solids Separator

Electrolyzer

SabatierReactor

Liquification & Storage System

Gas ProcessorSeparator

KeyHydrogenMethaneOxygen Mixture

CO2

H2O

- 35 -

Worker Bee™ Spacecraft Configuration Oblique View

15 m Diameter Inflatable Reflector

Top View

Sub-Reflector

Extendable Docking Adapter

Extendable Docking Adapter

Turning Mirror

Spacecraft Bus

Light Tube 15 m Diameter Inflatable Reflector

Design Adapted from Sercel Apis™ NIAC

Study

- 36 -

Deep Space Exploration System (DSES)

Worker Bee™ System Provides Propulsion Using Water STR for Human

Exploration of Asteroids

Moderate Sized Habitat Modules Provide ≈ 50 m3 per Crew Member for Crew of

Three on ≈ 6 month Voyage

System Provides Two Suit Ports, Emergency Air Lock, and Two Scooters for Asteroid Exploration

Used for Trans-Mars, Martian Moon, and Asteroid Exploration

- 37 -

Honey Bee Spacecraft Configuration Honey Bee With Inflatable Bag in Asteroid Capture

Configuration

15 m Diameter Inflatable Reflector

Design Adapted from Sercel Apis™ NIAC

Study

Honey Bee™ With Asteroid Captured in

Containment Bag

Mini Bee: Compatible With SmallSat Launchers

Mini Bee: 250 kg Technology Demonstration Vehicle

4,000 kg Class Vehicle Requires Full Falcon 9 FT

- 38 -

Honey Bee for Asteroid Ice Return

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

500 1,000 1,500 2,000 2,500 3,000 3,500

Ret

urne

d

Mas

s (k

g)

Delta-V (m/sec)

Honey Bee™ Water Return (kg) as a Function of ∆V (200,000 kg Initial Load)

Reusable Spaceship Upper Stage Lunar Landed Configuration Bottom View

Legs Stowed

Bottom View Legs Deployed

Launch Configuration

Payload Crane Cargo Bay Doors

Removable Habitat Module

Airlock

Crane Driven Elevator

Emergency Ingress Ladder

Landing Gear Heat Shield Door

Landing Gear Heat Shield

Doors

Descent Engines

Descent Engines

Aero Surfaces

Landing Gear Heat Shield

Doors

Cargo Bay Doors

Ascent Engines

Ascent Engines

- 40 -

Scooter Enhanced EVA Support System Pilot Astronaut Operates

Vehicle While EVA Specialist Performs Duties With Feet in

Foot Restraints

Astronauts in Transit to Target

- 41 -

Lunar Orbital Outpost Build Sequence (1)

- 42 -

Lunar Orbital Outpost Build Sequence (2)

- 43 -

Lunar Orbital Outpost Build Sequence (3)

- 44 -

Lunar Orbital Outpost Build Sequence (4)

- 45 -

Lunar Orbital Outpost Build Sequence (5)

- 46 -

Lunar Orbital Outpost Build Sequence (6)

Propellant Processing Begins When the Outpost

is Completed

- 47 -

Operational Lunar Orbital Outpost NEO or Mars

Exploration Vehicle Departing

Honey BeeTM Delivering Asteroid

ISRU Ices

Reusable Spaceship Arriving

From Earth

- 48 -

NEO DSES Human Exploration Vehicle Configuration With Worker Bee™

Used for Both Human NEO and Mars Orbital Exploration

(Forms the basis of an orbital outpost at Mars near

Deimos orbit).

Image shows configuration with

Worker Bee™. Reusable Spaceship OTV used in LOX-LM

option.

- 49 -

EVA At Small Asteroid With Scooter System

- 50 -

EVA Boulder Transport With Scooter System

- 51 -

Initial Lunar Surface Operations

- 52 -

Mars Exploration Systems at Deimos

- 53 -

Mars Exploration Systems at Deimos

- 54 -

Reusable Spaceship on Mars

- 55 -

What This Gives Us

- 56 -

Integrated Mission Schedule

  Start Year Mission/Event 1 3 5 7 9 11 13 15 17 19 21

Lunar Orbital Outpost                       Establishment                       Operations                      

NEO Exploration                       Mission 1 (14 mo. Duration)                       Mission 2                       Mission 3                       Mission 4                     Mission 5                      

Lunar Surface Operations                       Site Selection and Initial Base                       Base Expansion and Occupation                      

Mars Exploration                       Mission 1 (30 mo. Duration)                       Mission 2                      

Mission 3                      

•   Example of how missions might be scheduled over a 20+ year span.

•   Used to determine the number of active Honey Bees™ required over time and to provide for a summary across all NASA Human Exploration mission scenarios.

•   Did not explore SLS/Orion options as preliminary analysis showed only one mission type possible under any reasonable budget

- 57 -

Cost Modeling Assumptions •   NASA PPP Based on COTS and Related Programs

–  1/3 -2/3 cost share –  The 1/3 is financed

•   Robotic systems costed using NASA cost model •   Human space systems costed using Claybaugh approach

–  Accurately reflects SpaceX development price to NASA for commercial

–  Accurately reflects STS and ISS development costs for BAU •   DDT&E Through First Two Units As Per Models •   Subsequent units @ 90% learning curve

Four Approaches: -  PPP vs BAH -  ISRU vs Launch From Earth

- 58 -

Cost Model Results !20 Year Summary – NASA Business as Usual no ISRU

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Billion $

Year

Non-ISRU NASA BAU Costs by Category

Launch

Ops

Ops Dev

Add'l Units

DDT&E

Unaffordable: Requires Doubling the NASA Budget

- 59 -

Cost Model Results!20 Year Summary – Best Commercial Practices, no ISRU

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Billion $

Year

Non-ISRU Costs by Category

Launch

Ops

Ops Dev

Add'l Units

DDT&E

Unaffordable: Requires > 50% Increase in NASA Budget

- 60 -

Cost Model Results!20 Year Summary – NASA Business as Usual with ISRU

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Billion $

Year

NASA BAU LOX-LM Costs by Category

Launch

Ops

Ops Dev

Add'l Units

DDT&E

Marginal: Requires ≈ 30% Increase in NASA Budget

- 61 -

Cost Model Results !20 Year Summary – Best Commercial Practices

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Billion $

Year

Apis LOX-LM Costs by Category

Launch

Ops

Ops Dev

Add'l Units

DDT&E

Affordable Within Congressional Guidelines

- 62 -

Summary of Cost Analysis Results

Total Cost $B Savings $B Comments

NASA Business As Usual, Supply From Earth ~400 0 Unaffordable: requires doubling the

NASA Budget

Commercial Business Practices, Supply From Earth

~309 ~90

Unaffordable: requires > 50% increase in NASA Budget

NASA Business As Usual, Asteroid Resources ~150 ~250 Marginal, Requires ≈ 30% increase

in NASA budget

Commercial Business Practices, Asteroid Resources

~95 ~305 Affordable, Average NASA Human Exploration Budget ≈$6B Annually, Fits Within Congressional Guidelines for HEOMD.

Required: Major Shift to PPP for Deep Space Transportation Plus Massive ISRU

- 63 -

TransAstra Minimum Business Case: !Summary of Costs and Revenues

-$2,000

$0

$2,000

$4,000

$6,000

$8,000

$10,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Million $

Year

Annual Performance

Cost

Revenue

Profit/Loss (PreiTax)

Financing @10%

- 64 -

Business Case: !Transportation Service Price Analysis

•  Propellant cost based on: –  Honey Bee™ Unit Cost: 174 M$ (DDT&E TFU=$1.7B) –  Honey Bee™ lifetime: 10 years –  Honey Bee™ lifetime number of trips: 7 –  Replacement Asteroid Capture System (each): 20 M$

•  6 will be required over the lifetime. –  Replacement Inflatable Systems (each): 10 M$

•  2 will be required over the lifetime –  Initial Launch Cost: 63 M$ (Falcon 9) –  Mass returned per trip: 100,000 kg on average –  Average Propellant production from Mass returned: 60,000 kg –  Total Lifetime Propellant production: 420 MT –  Honey Bee™ lifetime costs: 174 + 120 +20 +63 = 377 M$ –  377/420 = 748 $/kg Propellant Cost –  Price is 748 $/kg + 20% or 897 $/kg

Cost to LEO would be $3,000/kg, Cost to LDRO would be $12,000/kg

- 65 -

TransAstra Projected Market Cap Based on Five Year Forward PE 10:1

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Million $

Year

Market Cap for P/E of 10

- 66 -

Space Tourism Market:Very High Net Worth People

- 67 -

Human Cislunar Transportation Fee Analysis

-  Price per trip determined to be 60 M$ for 20 passengers or $3M each, not including Launch costs

-  A 20 person passenger module is compatible with a reusable medium class 2nd stage!≈ Next Gen Falcon 9 or New Glenn

- 68 -

The Next Market: Cislunar Tourism

0

100

200

300

400

500

600

700

800

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

# of Persons

Year

Total Persons traveling to Cis-Lunar Space per year

Ramps to 40 Per Year Cislunar Excursions for 20 People

- 69 -

Tourism Market Projection

0

2,000

4,000

6,000

8,000

10,000

12,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Year

Cumulative Number of Persons to have visited lunar orbit

Post Apollo

- 70 -

Findings

•  NASA’s ambitions in the area of deep space human exploration are not affordable with a realistic budget close to $20B/yr (2017 dollars) without fundamental change.

•  Two fundamental changes can enable an exciting program of human exploration: –  Public Private Partnership (PPP) –  Asteroid ISRU.

[email protected]

- 71 -

Questions?

[email protected]

Joel C. Sercel, PhD

(818) 422-0514

- 72 -

Bibliography •  Brophy, John and Muirhead, Brian (2013) “Near-Earth Asteroid Retrieval Mission (ARM) Study”

Presented at the 33rd International Electric Propulsion Conference, Washington, DC, October 6 – 10, 2013, IEPC-2013-82.

•  Campbell, Nicholas S., Brian M. Argrow, and Jeremy C. Ralph, “Aerobraking in the Cis-Lunar Economy” AIAA Flight Mechanics Conference, 2017-0468

•  Palaszewski, Bryan, “Lunar Missions Using Chemical Propulsion: System Design Issues”, NASA Technical Paper 3065, January 1991

•  Pietrobon, Steven S., “Analysis of Propellant Tank Masses”, https://www.nasa.gov/pdf/382034main_018%20-%2020090706.05.Analysis_of_Propellant_Tank_Masses.pdf

•  Sercel, Joel C., Asteroid Provided In-situ Supplies (Apis™): A Breakthrough to Enable an Affordable NASA Program of Human Exploration and Commercial Space Industrialization, NIAC Phase I Final Report, 29 February 2016

•  Sercel, Joel C., “The N-Stage Reusable Space Vehicle (NSRV): Aviation Like Space Operations Initiating a Revolution in Military Affairs”, ICS Associates Inc., November 11, 2016

•  Sercel, Joel C., (1985) "Solar Thermal Propulsion for Planetary Spacecraft", presented at the JANNAF Propulsion Conference, San Diego, CA, April 9-12, 1985.

•  Sonter, Mark J., “The Technical and Economic Feasibility of Mining the Near-Earth Asteroids”, Master’s Thesis, 1997, Acta Astronautica, Vol. 41, pp 637-647

•  Wilcox, Brian, et al, Testbed for Studying the Capture of a Small, Free-flying Asteroid in Space”, AIAA 2015

•  “2015 Commercial Space Transportation Forecasts”, FAA Commercial Space Transportation (AST) and the Commercial Space Transportation Advisory Committee (COMSTAC), April 2015