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IS A LI QUID PROP ELLANT GUN A VIABLEOPTION FOR TH E FUTURE MAIN BATTLETANK IN THE UNITED STA TES ARMY?

A thesi s presented to the Faculty of the U.S. ArmyCommand and General Staff College in partialfulfillment of the requirements for thedegreeMASTER OF MILITARY ART AND SCIENCE

CURTIS L. MCCOY MAJ USAB.S. United States Military Academy 1978M.B.A. Flo rida Institute of Technology 1987

Fort Leavenworth Kansas1992

Approved for public rel ease; distribution is unlimited.


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MASTER OF MILITARY ART AND SCIENCETHESIS APPROVAL PAGE

Name of candidate: MAJ Curtis L. McCoyTitle of thesis: Is A Liquid Propellant Gun A Viable OptionFor The Future Main Battle Tank In The United States Army?

Thesis Committee Chairman

Member

Member, Consulting~ ~ u i l f r e d Dellv Faculty

Accepted this 5th day of June 1992 by:

Director, Graduate Degree~ h ) l i p 4 Brookes, Ph.D. Programs

The opinions and conclusions expressed herein are those ofthe student author and do not necessarily represent the viewsof the U.S. Army Command and General Staff College or anyother governmental agency. References to this study shouldinclude the foregoing statement.)


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ABSTRACT

S L QU D PROPELLANT GUN V ABLE OPT ON FOR THE FUTURE MA NBATTLE TANK IN THE UNITED STATES ARMY b y MAJ Curtis L. McCoyUSA 112 pages.This study is an examination of three areas: historical U.S.liquid propellant development liquid propellant logisticalconsiderations and the technical considerations in theapplication of a liquid propellant gun in a combat vehicle.The study examines the potential and demonstrated benefits ofliquid propellants for the military. The study uses the solidpropellant guns technology as the baseline t o conduct acomparison of liquid propellant guns i n the same operationalrequirements.The analysis b y the author on the logistical impacts focuseson the industrial base conversion production costs ofpropellants ammunition transportation requirements andliquid propellant demilitarization. The analysis continueswith a discussion on combat vehicle survivability firepowerand mobility.This study concludes that a liquid propellant gun is a viableoption for the Army to pursue. The primary logisticaladvantage with liquid propellant is volume efficiency whichimpacts storage transportation and ammunition processing.tank equipped with a liquid propellant gun has advantagesover a sol id propel ant gun in rates of fire basic ammunitionload capability survivability of the system and vehicleweight reductions.


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ACKNOWLEDGEMENTS

would like to recognize several people whose helpand support have made this study possible. First, I want tothank my wife, Eleane and my children, Sarah, Jason andAndrew. This thesis would not have been completed withouttheir total love, prayers, spiritual support, understandingand hours of long editing and typing support.Second, I would like to extend my appreciation to themembers of my research committee, Mr. James F Fox, Mr. DwainH. Skelton, and COL Wilfred Dellva. Their patience andobjective insights were instrumental in my completion of thisthesis. Third, I would like to thank the members of my A 2 2 1Research Methodology I I seminar group. The group, led by COLRobert A Gimbert, provided the logistical insights that werecritical to effective analytical review of the project. Thegroup provided the needed encouragement during the wintermonths of Term I I which assisted me in staying on course.Finally, would like to thank the staff in theCombined Arms Research Library. Especially Craig McLean andJohn Rogers for their insight on how to find researchmaterials, professional encouragement and assistance whichformed a foundation for the completion of my thesis.


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TABLE OF CONTENTS

THESIS APPROVAL PAGE........................................ABSTRACT...................................................TABLE OF CONTENTS............................................

............................................IST OF FIGURES v i iLIST OF TABLES............................................ i i iCHAPTER 1 DEFININQTHE PROBLEM.............................

I n t r o d u c t i o n.......................................Background.........................................Assunptions ........................................D e f i n i t i o n sL i m i t a t i o n s ......................................e l i m i t a t i o n s 6S ig n i f i cence o f S tudy ......................................................................ethodology 7S u m r y ........................................... 0............................HAPTER 2 . SURVEY OF LITERATURE 11I n t r o d u c t i o n...................................... 1P a r t H i s t o r i c a l ............................... 2P a r t I 1 Emerging Qun Propuls ionTechnologies............................ 7..............a r t l l L o g i s t i c a l C o n s id e r at io n s 28...........................................umnary 32

CHAPTER 3. HISTORY OF LIQUID PROPELLANT DEVELOPMENT........ 3l n t r o d u c t l o n ......................................3.......ar t Bu lk Loaded L i q u i d Pr op e l lan t Guns 36Pa r t Re g en e ra ti ve L i q u id P ro p e l l a n tQuns....................................2


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P a r t l l Review o f P ast L i q u i d P ro pe l l an tDevelopments................................ 8Swmary ...........................................CHAPTER 4 . CONVENTIONAL GUN PROPULSION REVIEW .............. 4

I n t r o d u c t i o n...................................... 4P a r t Conven t i ona l P ropu l s ion .................. 5P a r t II Advanced Convent iona l Propu ls ion........Sumnary ........................................... 65.......................HAPTER5. LOalSTlC LCONSIOER TIONS 66I n t r o d u c t i o n 6...............ar t In d u s t r i a l Base Convers ion 66Pa r t P ro pe l l an t P roduc t i on Cos t SavingsFactacs......................................P a r t l l Comnerc ia l P roduc t i on o f L i q u i d

P rope l l an ts .................................. 1...................a r t I V Transpor ta t i on Issues 72..................a r t V D e m i l i t a r i z a t i o n Issues 79...........................................umnrry 79CHAPTER6 . COMBAT VEHICLE ANALYSIS......................... 1

I n t r o d u c t i o n...................................... 1Part S u r v i v a b i l i t y.............................2P ar t 1 Fi repouer ............................... 87P a r t M o b i l i t y............................... 8Sumnary ........................................... 9.................HAPTER 7 CONCLUSIONS AND RECOMMENDATIONS 9I n t r o d u c t i o n......................................P a r t I Conclusions ..............................P ar t Recomnendat on s ......................... 3...........................................umnary 93

BIBLIOGRAPHY ................................................95INITIAL DISTRIBUTION LIST .................................. 4


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LIST OF FIGURES

Figure Page1 Schematic Diagram o n a MonopropellantBulk Loaded Prope lant Gun : 372 Schematic Diagram on a BiopropellantBulk Loaded Propel lant Gun 383 Interior Ballistic Cycle of aBulk Loaded Propellant Gun 404 Schematic Diagram on a MonopropellantRegenerative Injection Liquid Propellant Gun 35 Schematic Diagram on a BiopropellantRegenerative Injection Liquid Propellant Gun 46 Interior Ballistic Cycle of aRegenerative Liquid Propellant Gun 4 6

Logistical Advantages of Liquid Propellants 75


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LIST OF TABLES

Tab e PageAmnunition Data 9EstimatedCosts of Propellants 7Cubeverses Weight Comparisons 76ATPTrailerComparisons 76

5 Comparison of M I A Solid Propellant Verses LiquidPropel lant Vehicle Systems 8


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CHAPTERDEFINING THE PROBLEM

IntroductionThe primary purpose of this thesis is to examine

whether the Army should continue development and adopt theliquid propellant gun (LPG), or remain solely with the currentprojected improvements of the solid propellant gun (SPG) forthe future main battle tank. The focus of this discussionwill be on the several key elements of the life cycle processof both technologies with respect t o the future main battletank. A baseline combat vehicle, the MlAl Abrams Main BattleTank, will be used to compare SPG and LPG technologies.

Today's Army's arsenal of weapon systems reliesheavily on one type of propulsion delivery system. SolidPropel lants (SP) have been the principal means of del ivery forconventional munitions. SP charges have met the need for themilitary for decades. Even with the currently available andemerging technologies, the advances in SPs have beenrelatively minor. These small advances in SPs have beenachieved at great expense. Advances have been limited atbest


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BackgroundSlow technology advances in SPs, primarily related to

increased muzzle velocities in tank cannons, have forced aconstant review of the state-of-the-art propulsiontechnologies and possible future technologies. Slow progresstowards increased muzzle velocity coupled with the desire toreduce costs, and increase efficiency while meeting currentmission requirements have brought about a new school ofthought. In searching for new, more efficient systems in thefield of propulsion, the application of Liquid Propellants(LPs) to gun systems is one possible promising option. Thedesired characteristic of any future gun requirement is tohave lethality on the modern battlefield preferably atextended ranges greater than the effective range of t heenemy s armament. For the purposes of this paper, it will beconsidered that ranges from 0 2000 m will be defined as aclose range and 2000 3000 m will be the extended range. Toachieve that end, accuracy and mass firepower are consideredto be very important elements. LPs could possibly offer theseadvantages over SPs.

A S S U ~ D ~ ~ O ~ S1 ) regenerative LPG for the MlAl tank could be

demonstrated during FY94(2) Reliability and maintainability characteristics

are solvable on the LPG.


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(3) Two basic 120mm rounds M829A1, Armor PiercingFin Stabilized Discarding Sabot (APFSDS-T) and the M830, HighExplosive Anti-tank Multipurpose with Tracer (HEAT-MP-T) willbe used for all technologies.

4) A baseline vehicle, the MIA1 Abrams Main BattleTank, will be used to compare the different technologies.

5 Information about the Army s current gunpropulsion technologies is available for review.

(6) The LPG will have an autoloader system on theMlAl tank or a future main battle tank.

Definitions1 Solid Propellant Gun (SPG), conventional

propulsion technology on the current Army tank fleet, is thebasic chemical energy propulsion used to propel the family ofcannon fired projectiles down range. The current solidpropellant round consists of a projectile partially enclosedby a combustible case of granular type propellant.

(2) Liquid Propellant Gun (LPG) is a concept basedon mechanical control of the amount of propellant in thecombustion chamber. There are three general types of LPGs:

a. Bulk Loaded LPG: It is essentially a solidpropellant gun with the necessary changes to accommodate thenew propellant in the breech. The propellant initially fillsthe combustion chamber behind the projectile before ignition.All the propellant is ignited at one time


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b. Regenerative LPG: The gas pressure in thecombustion chamber pumps additional propellant into thecombustion chamber during the ballistic cycle.

c. Externally pumped LPG: An externallypowered pump forces the additional propellant into thecombustion chamber during the ballistic cycle.

3) Liquid Propellant Traveling Charge Gun LPTCG)is the concept of loading liquid propellant into a dispenserattached to the projectile. Initial acceleration is providedby burning a propellant charge in the chamber between thetraveling-charge dispenser and the barrel face. The drivingcharge may be a solid or liquid propellant.

4) Vulnerability The characteristics of a systemthat cause it to suffer a loss of combat utility or reductionof capabi 1 ity to perform the designated mission s) as a resultof having been subjected to a hostile environment on thebattlefield.

5) Lethality The ability of a system to cause theloss of, or a degradation in, the ability of a target systemto complete its designated mission s).

6) Survivability The capability of a systemresulting from the synergism between personnel, materiel

design, tactics, techniques, procedures and doctrine) toavoid, withstand or recover in hostile man-made and natural)environments without suffering an impairment of its ability toaccomplish its designated mission.


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(7) Armor Piercing Fin Stablized Discarding SabotThis a round which is a one piece depleted uranium kineticenergy (KE) penetrator with a combustible case. It is foundin the 120mm class of ammunition as a M829, a M829A1 and aM829E2 and in the lO5mm class of ammunition as a M774, a M833and a M900.

(8) High Explosive Anti-tank with Tracer This ashaped charged warhead round which has a combustible case witha multiaction fuse. It is found in th e 120mm class ofammunition as a M830 and in the 105mm class of ammunition asM456.

(9) SMART Ammunition These are high explosivetarget activated fire and forget cannon launched munitionssuch as the XM943 smart target activated, fire and forget(STAFF) 120mm tank round and the armor piercing enhancedkinetic energy weapon (X-rod) round coupled with a terminalguidance.

(10) Enhanced Kinetic Energy Weapon (X-rod) It isan advanced tank fired, guided kinetic energy projectilesystem capable of defeating targets at extended ranges.superior hit probability is expected y using competingconcepts, command guided or fire and forget' guidance.

LimitationsThis document will be written at the unclassified

level to enable the widest dissemination of the document tothe Department of Defense community. Most of the advanced

5


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MethodologyThe primary research methodologies used in this thesis

are a descriptive archival and a comparative analyticalevaluation. The descriptive archival methodology is designedto concentrate in liquid gun propulsion with subheaders incombat vehicle firepower combat vehicle survivability andcombat vehicle sustainment on the future battlefield.

Past studies are an excellent source to establish acommon foundation from which to start the thesis. During thereview of past technology developments in LP criteria can bedetermined to evaluate the potential for the system in thefuture. These sources are critical to providing an analyticalbase from which to project conclusions for the future of LPGsin tanks.

The review of past studies includes sources related tothe technical design character istics of LPG. There is a largebody of information in technical reports which describes theexperiments which range from bulk loading to a regenerativegun in actual hardware mounts. Due to the rapidly changingtechnology there appears to be questions whether a LPG is nowplausible on a combat vehicle on the battlefield.

To arrive at an end state in this thesis whichaddresses whether LPG is an option for the future main battletank critical performance elements have developed from the


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Chapter 6 Combat Vehicle Impact AnalysisChapter provides the reader an analysis of the LPG

from the three functional tank requirements: survivability,firepower and mobility. The author conducts a subjectiveevaluation of th e functional requirements in a directcomparison between the SPG and LPG.

Chapter 7 Conclusions and RecommendationsThe answer t o the thesis is determined based on th e

analysis conducted in Chapters 5 and 6. It draws a conclusionof the meaning of the study. It also relates the study toother works and make recommendations for future studies.

SummaryThe purpose of Chapter was to explain the importance

of the study and the three areas being investigated. Theintroduction and background outlined the need for a new gunpropulsion technology, identified a possible candidate forreview, drew the framework of the study, stated the describedresearch methodology to be used throughout the effort, and themechanical structure of the thesis y chapter. The need fora new gun propulsion system for the Army's main battle tankcould not be greater than at this time. The future does notpromise any near-term breakthroughs in the solid propellantarena. Concepts such as electrothermal technology are not anear-term optionsof today but liqu

in solvid prope

ing the gun propulsion requirementsllant could be


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CHAPTERSURVEY OF LITERATURE

IntroductionThis survey of literature performs atwo-fold mission.

It first demonstrates to the reader the technical sources andvariety of research materials used in this study. Secondly,the survey provides a basis from which further research can beconducted by any reader in the three principal study areas.The three study areas are: historical Army liquid propellantgun development, emerging gun propulsion technologies and thecriteria to evaluate both them and the logistical impact ofsustaining new weapon systems.

The primary source of research material was theCombined Arms Research Library CARL) at Fort Leavenworth,Kansas. Also, the study incorporated supplementalpublications and notes which were provided to or developed bythe writer during a previous assignment at the U S ArmyBallistic Research Laboratory. Additionally, the CombinedArms Command, Combat Developments activity providedinformation pertaining to current or ongoing development inthe liquid propellant gun program.


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majority of the research material used can bedivided into three categories; books government documents andperiodicals. Books provided an excellent review of trends andthe development of tank cannons in combat vehicles. They alsoassisted in establishing the criteria to evaluate a newemerging technology against the currently employed technology.U.S. Government documents were a primary source of collectingdata from actual test firing and modeling to evaluate theliquid propellant guns against conventional solid propellantguns. Periodicals also established additional criteria forevaluations and outside viewpoints on trends in armoredvehicle developments.

This chapter is divided into three parts: historicalemerging gun propulsion technology and logisticalconsiderations. Each section identifies the essential

research material used to explore that area of interest.Part

HistoricalThere is a significant amount of research material

available on the development of tanks from World War to thepresent. The materials provide a very good worldwide view ofcurrent technology development but lack greatly in discussingin any depth emerging advanced technologies. The only clearsource documents that discuss the historical development ofliquid propellant propulsion are in government documents. The


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following is a concise summary of those critical sourcedocuments which trace the origin of the liquid propellantprogram in the United States with a desired cannon applicationin a weapon system.

BooksIn Antitank, Richard E Simpkin provides a very wide

look at what kind of doctrine, major equipment and forcestructure the mechanized battle as a whole, on the ground andin the air space just above it, may call for in the closingdecade of this century of technological revolutions. 8Simpkin attempts to lead with technical arguments and thestate of the art, and to look at the principles and trends ofweapon systems rather than their historical origins. ' Heconcludes with the impact of new weapon systems factors ontraining, logistics and manning.

In Technolow in War: Impact of Science and WeaponDevelopment on the Modern Battlefield, Kenneth Mackseyexplores the impact of technology on current and emergingweapon systems. He spans his discussion from 1915-2000. Heis able to identify specific key developments on main battletanks and trace their projected technological advancements tothe year 2000.

'~ichard . Simpkin, Antitank: An Air mechanized ResDonseto Armored Threats in the 90s (Elmsford, NY: Pergamon Press,Inc., 1982), 8.'lbid.


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R.P. Hunnicutt has written a series of books whichprovide a summarized, in depth review of the U.S. Army tankprogram from 1914 to the present. Fi re ~o we r: A Historv ofthe American Heavy Tank, Sherman: A History of the AmericanMedium Tank, Patton: A History of the American Main BattleLank and Abrams: A History of the American Main Battle Tankprovide a well versed look at trends in the evolution of thearmored tank force especially in types of fire controlsystems, gun mounting, tank guns, and automatic loadingequipment.

U S Government DocumentsLiquid Propellant Guns, by Walter F. Morrison, John

D. Knapton, and Melvin J. Bulman provides an excellent reviewwhich summarizes liquid propellant gun research in the UnitedStates. Liquid propellants have been the focus of periodicresearch efforts from just after the Second World War to thepresent.jdevelopmentregenerativetechnologica

i s paper discusses, in depth, the historicalof bulk loaded liquid propellant guns andliquid propellant guns. The bulk of thesummary data generated in the report is focused

on the historical progression of the interior ballistics ofbulk loaded liquid propellant guns and regenerative liquidpropellant guns.

3 ~ a l t e r Morrison, John D. Knapton and Melvin J.Bulman, Liquid Propellant Guns, ADA188575 (Aberdeen ProvingGround, MD: U.S. Army Ballistic Research Laboratory, October1987). 1


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Liquid Propellants for Gun Applications, by WalterF Morrison, John D. Knapton, and Guenter Klingenberg is asurvey of some of the recent and ongoing iquid propellantresearch in both the United States and Germany. It providesa brief summary of past investigations and the limitingtechnology factors to liquid propellant development. Thesurvey includes Germany's progress and major obstacles toovercome in successfully demonstrating a liquid propellant ina 105mm or greater test fixture. It concludes that liquidpropellant propulsion has evolved over the past forty yearsinto a goal to develop improved liquid propellant regenerativedesigns and component mechanisms and to further improveexisting propellant candidates.

The Interior Ballistics of Regenerative LiquidPropellant Guns, by Walter F Morrison, Paul G. Baer, MelvinJ. Bulman, and John Mandzy is a paper which summarizes thecurrent development of large caliber regenerative liquidmonopropellant guns. Also it reviews the experimental testfiring results of regenerative liquid propellant guns rangingfrom 0.35 inch to 105mm. The paper traces liquid propellantdeveloped from the 1940s to the present, to include the majorengineering test failures during the 1970s. It concludes that

%alter F Morrison, John D. Knapton and GuenterKlingenberg, Liquid Propellants for Gun Applications,ADB090195 (Aberdeen Proving Ground, MD: U.S. Army BallisticResearch Laboratory, January 1985), 36.


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the focus of the U.S. Army liquid propellant efforts is thedevelopment and testing of a 155mn, technology demonstrationfixture.

. Tri-Service Plan for Liquid Propellant Technology forGun Applications, by Richard H. Comer and Walter F Morrisonis a plan prepared by the Task Force Group for LiquidPropellant Guns and approved by the Joint Directors ofLaboratories. It was not implemented. An updated version ofthis program was presented to the Director of Defense Researchand Engineering for discussion with the House Armed ServicesCommittee staff in August 1979, but no program was initiated.

1979lantthe

A synopsis of events since thenversion of the Tri-Service P

leading to the Augustlan for Liquid Prope

Technology for Gun Appl-ications is contained withindocumentation.

Liquid Propellant Technology Program, by Walter FMorrison was prepared at the request of Lieutenant General D.Keith, Deputy Chief of Staff, Research, Development andAcquisition, in 1981 to develop a program which would provideth e liquid propellant technology base required to decide theadvisability of developing liquid propellant guns for the

%alter F Morrison, Paul G. Baer, Melvin J. Bulrnan andJohn Mandzy, The Interior Ballistics of Regenerative LiquidPropellant Guns, ADA190020 (Aberdeen Proving Ground, MD:October 1987). 32.


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1990s. 6 This document tied the Department of Defenseservices together into a Tri-Service program focused on liquidpropellants.

PartEmerging Gun P ro ~u ls io n echnologies

Books do not address in any specific detail thesubject of advanced gun propulsion programs which currentlyrevolutionize the armored combat vehicle. Most documents ofthat nature are classified and wi not be part of this study.The largest source of unclassified materials which discussesliquid propellant guns is government technical reports.Periodicals assist in the evaluation of new technologies byidentifying additional areas of consideration. Periodicalscontain additional thoughts on the subject which are worthreview.

BooksHuman Factors in Mechanized Warfare, by Richard E.

Simpkin attempts to explore in depth the basic facts of atanker's life and their influences on how he is trained andled and how his machine is designed. I The book focuses on

6 ~ a l t e r F Morrison, Liquid Propellant TechnologyProgram, AD6056054 (Aberdeen Proving Ground, MD: U.S. ArmyBallistic Research Laboratory, January 1981), 1'~ichard Simpkin, Human Factors in Mechanized Warfare,(Elmsford, New York: Pergamon Press Inc., 1983): 4.


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the key elements the analysts and subsystem designers mustaddress in developing a modern combat vehicle. Simpkin isable to further address key differences between East and Westin design technology philosophies.

The Dangers of New Weapon Systems, edited by WilliamGutleridge and Trevor Taylor is a series of inter-relatedpapers, methods and criteriato assess current and new weaponstechnologies. The subjects range from criteria for evaluatingthe dangers and characteristics of new weapon systems, to theprocess of weapons development and mechanism to manage andcontrol it.

Tank Warfare, by Richard E. Simpkin begins with abroad look at the development of tank warfare and attempts toidentify trends to the present. Simpkin takes an in-depthlook at the tank design factors of firepower, mobility,survivability, fightability, and design constraints. The bookincludes lessons learned by NATO and the Soviet Union in tankdesign

U.S. Government DocumentsLiquid Propellant Traveling Charge Gun Concept , by

Eugene Ashley is a report which explores the feasibility ofa liquid propellant traveling charge gun concept, which hasbeen proposed as a means for improving the performance of high


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velocity guns. ' The growth potential for a 1 iquid propellantgun system with a traveling charge is discussed in depth withmuzzle velocity measurements taken from actual firings.

A Propulsion System Comparison Study For the 1 2 0 mAnti-Armor Cannon, b y Paul G. Baer, Catherine F. Banz, lngoW. May, and Walter F. Morrison is a study which explores thedifferent types of near term advanced technologies impact onthe performance of a 120mm high performance cannon. Theinvestigation includes an examination of the limits toperformance potential of conventional gun propulsion andcompares them to the potential performance of a regenerativeliquid propellant gun. The study was focused on key interiorballistic parameters which were used throughout the parametricstudy. The clear determining factor was the potential forincreased muzzle velocity which could result in significantimprovements in overall gun system effectiveness. The studyused a criteria of five to ten percent increases in strikingvelocity as important enough to justify substantialdevelopmental effort on such technology.

'~ ug ene Ashley, Liquid Propel lant Travel ing Charge GunConcept, ADA033971 (Burlington, VT: General Electric Company,November 1976), 1'paul Q Baer, Catherine F. Banz, lngo W. May and WalterF. Morrison, A Propulsion System Comparison Study for the1 2 0 m Anti-Armor Cannon, ADA187175 (Aberdeen Proving Ground,MD: U.S. Army Ballistic Research Laboratory, August 1987), 1


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development even prior to any system testing. The studyaddresses four types of advanced gun propulsion: advancedsolids propellant (-1, liquid propellant (LP),electromagnetic (EM), and electrothermal (ET) for threedifferent weapon system types: artillery, armor and airdefense. The study identifies the high risk subsystems on theabove listed advanced weapon systems technologies.

The Effect of Propellant Composition on SecondaryMuzzle Blast Overpressure, by George E Keller studies thesecondary muzzle flash from the reignition of a mixture offuel-rich exhaust gases and the entrained air in cannonsystems. The study examines three factors which affectsecondary muzzle flash: chemical factors, physical factors andmechanical factors.

Sensitivity Characterization of Low Vulnerability(LOVA) Propellants, by M.S. Kirshenbaum, L. Avrami and B.Strauss is a technical report that describes the results of aninvestigation that was conducted to determine the sensitivityproperties of a number of candidate LOVA propellants. Thereport includes thermochemical properties in the comparisonbetween the LOVA candidates and the current conventionalpropel lants.

M.S. Kirshenbaum, L. Avrami and 6 Strauss, SensitivityCharacterization of Low Vulnerability (LOVA) Propellants,ADA126130 (Dover, NJ: U.S. Army Armament Research andDevelopment Command, Large Caliber Weapon Systems Laboratory,March 1983), 1


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Low Temperature Properties of HAN-Based LiquidPropellants, by John 0 Knapton and Walter F. Morrison is astudy to examine the dynamic viscosity of potential liquidpropellants from room temperature to about -65 degreesCelsius.

Combustion Processes inconsolidated Propellants, bylngo W. May and Arpad A Juhasz is a memorandum report whichexams the research efforts for higher muzzle velocities in gunpropulsion through consolidated propellants as a means ofincreasing the charge-to projectile mass ratio for a givenchamber volume.

Liquid Propellants For Gun Applications. by WalterF. Morrison, John D Knapton, and Guenter Klingenberg is atechnical report of the state-of-the-art liquid propellanttechnology, its potential and limitations, as we11 as aprognosis for its development and application. The potentialbenefits of the liquid propellant portion of the surveyaddresses advantages in the areas of technical, systemperformance, operational potential, logistical, and financial.n particular the report addresses the operational potential

in design criteria, such as Nuclear Biological and Chemical

l1lngo . May and Arpad A. Juhasz, Combustion Processesin Consolidated Propellants, ADA101163 (Aberdeen ProvingGround, MD: U.S. Army Armament Research and DevelopmentCommand, Ballistic Research Laboratory, May 1981), 1


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protection, vulnerability reduction, mobility issues,transportability and resupply related t o a liquid propellantgun system. 2

Liquid Propellant Guns, by Walter F Morrison, JohnD. Knapton and Melvin J. Bulman is a study which includes acomparison of th e performance of monopropellants, bulk loadedpropellant guns, and conventional solid propellant guns.

The Accuracy of Tank Main Armament , by Joseph M.Olah and Fred L. Bunn is a report which discusses the accuracyof main armaments on armored systems; with a focus on tankcannons. It presents an indepth discussion into the classesand sources of gun error. Also, it describes required data tocalculate hit probabilities of tank fired munitions. Thepaper identifies possible criteria which should be addressedin any new weapon system.

Detailed Characterization of the Interior Ballisticsof Slotted Stick Propellant, by Frederick W. Robbins andAlbert W. Horat is a technical report which investigatesslotted stick propellant development. The study attempts toidentify thos e mechanisms which increase the thermodynamic

12~ot+ison, Liquid Propellants for Gun Applications, 3132.


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efficiency of stick propellants over granular propellants fora given charge weight. 3

Test Results From a Two-Stage Traveling Charge LiquidPropellant Gun, by lrvin C. Stobie, John D. Knapton, Bruce D.Bensinger, and Robert A. Pate is a test report for a 4 0 mfractional traveling charge (FTC) gun system. The testdemonstrated the abi ity to apply a iquid travel ing charge toa projectile with a conventional solid propellant charge.

High Performance Regenerative Liquid Propellant GunStudy, by J. Michael VanDerwerken is a study which examinesthe advantages of a high performance regenerative liquidpropellant gun in a future main battle tank. The key issuesevaluated were liquid propellant (LP) gun configurations, gunperformance characteristics, LP weapon system integrationfeasibility, vulnerability and logistics. 1 4

Ballistic Investigations of a High-Performance,Regenerative, Liquid Propellant Gun, by Cris Watson, John D.Knapton, Walter F. Morrison, and D. Maher is an investigationin the application of liquid propellants for gun propulsionsystems . This study demonstrates that a 30mm, liquid

13~rederick Robbins and Albert W. Horat, DetailedCharacterization of the Interior Ballistics of slotted StickPropellant, ADA147499 (Aberdeen Proving Ground, MD: U.S. ArmyBallistic Research Laboratory, September 1984 , 9.'l~ichael . VanDerwerken, High Performance RegenerativeLiquid Propellant Gun Study, AD8099639 (Pittsfield, MA:Qeneral Electric Company, Ordnance Systems, February 1986), 1


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propellant regenerative gun can operate in the high-performance, tank-cannon regime. .IS

PeriodicalsThe Two-Man Tank: An Idea Whose Time Has Come, by

Linwood E Blackburn compares the current main battle tankdesigns with future designs. It is a good discussion of theadvantages which technology has enabled the tank designers togo.from a four man crew to a two man crew. He summarizes theadvantages of tank design with crews that have less than fourpersonnel, in the areas of reduced vehicle size, reducedvulnerability. reduced procurement and operating costs, andimproved strategic transportability.

Human Factors Challenges in Armored Vehicle Design,by R Mark Brown discusses three human factors which he feltchal lenges the design evolution of armored vehicles. They areweight versus survivability, worldwide adaptability of combatvehicles, and crewmen information overload. He presents adiscussion on the size and weight trade off within any newweapon system that effects human factors.

The Heavily-Armored Gun-Armed Main Battle Tank is notOptimized for Mechanized Warfare, by Craig Koerner and

~ r i s atson, John D. Knapton, Walter F. Morrison and D.Maher, Ballistic Investigating of a High-PerformanceRegenerative Liquid Propellant Gun, ADA224593 (AberdeenProving Ground, MD: U.S. Army Ballistic Research Laboratory,February 1990), 1 .


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Michael O'Connor is an interesting article on designphilosophy driven by the modern tactical battlefieldrequirements. They developed a discussion on the impact ofincreased vehicle weight in relationship to vision,concealment, mobility, and dependence on a vulnerablelogistical tail which might raise some questions on the impactof liquid propellants.

Future Tank Guns, Part I : Solid and LiquidPropellant Guns, by R M Ogorkiewicz discusses the futureprospects and alternatives for increasing projectilepenetrating through an increased muzzle energy. The articleaddresses one method to improve the effectiveness of aprojectile is by increasing the energy per unit of cross-sectional area;'' To achieve that end state, the authordiscusses the options of increasing the calibre of the tankgun or increasing muzzle velocity of the projectile. Aparametric comparison between solid propellant and liquidpropellant is conducted in the 1 2 0 m calibre. The studyindicates an enhancement of vehicle survivability as a resultof reduced propellant vulnerability. The article concludesthat the growth potential of liquid propellant is in a twostage liquid propellant gun with a traveling charge.

1 6 ~ M Ogorkiewicz, Future Tank Guns, Part Sol id andLiquid Propellant Guns, International Defense Review. Vol.23, No. 12/1990: 1 3 7 7


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Liquid Propellant Artillery Proving Begins in theU.S., by Rupert Pengelley, discusses the liquid propellant(LP) research and development efforts being conducted byGeneral Electric in the 155mm howitzer class weapons system.The article compares test firing results in muzzle velocityand chamber pressure reproducibility on the test bed 155mmsystem. The article concludes with the potential positivebenefits of LP in reduced vulnerability to counter-batteryfire and the chances of detection by artillery locating radardiminished by resorting to multi-round TOT engagements at lowelevation angles.

Extended Range for ,155mm Artillery, by TerrenceRingwood takes a look at the major components that comprise anartillery system and their contributions to range performance.He explores the advantages and disadvantages in the currentdevelopmental efforts to improve range performance throughsolid and liquid propellants

The Return of the Gunned Tank Destroyer, by StevenR. Witkowski is an analysis of the Soviet Armored threat,current antitank technology, and doctrine. The articleaddresses the growth potential of technologies such aselectromagnetic rail guns, liquid propellant guns and hyper-velocity missi les which he be1 ieves are not mature enough for

~u pert engel ley, Liquid Propel lant Arti lery ProvingBegins in the U.S., International Defense Review, Vol. 23,No. 12/1990: 1379-1380.


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battlefield application. Conventional cannons are his onlysolution for meeting any problem in the future.

Liquid Propellant Charges for Gun and MortarAmmunition, by Wolfram Witt and Karlheinz Reinelt exploresthe potential advantages of liquid propellant charges for gunm u n i t i o n . The employment of liquid propellants in gunammunition could lead to benefits which reduce thevulnerability of propellant detonation when hit by enemy fire,employs combustible case ammunition which has a lower weightthan the current generation of solid propellant ammunition andsmaller dimensions, permit incremental charge loading for thegun system depending on firing range requirements, and whichcould create financial savings in the ammunition-manufacturingprocess. 8

Developing aaddresses some essent

Tank Autoloader, by John C. Woznickial criteria in the areas of vehicleintegration, lethality, survivabi

an autoloader is to be applied to

Part

ity, and sustainabia future combat veh

Lonistical Considerations

lity ificle.

The sustainment of the combat maneuver elements playsas major an impact on the battlefield as the combat weapon-

~olfram itt and Karlheinz Reinelt, Liquid PropellantCharges for Gun and Mortar Ammunition, International DefenseReview, Vol. 14, No. 1/1981, 64.


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systems. To develop a new weapon system is only one part ofthe equation. The sustainment aspects of the equipmentrequire major consideration prior to fielding. The primarysources of the logistical analysis of liquid propellant are ingovernment documents.

U.S. Government DocumentsClassification of Liquid Gun Propellants and Raw

Materials for Transportation and Storage , by William J.Cruice is the result of a study to evaluate the hazardousproperties of constituents and formulations of candidateliquid gun propellants for the purpose of classification intransportat ion. I9 The study has very interesting testresults with several of the possible liquid propellantcandidates having t o be classified as Military CLASS 2Explosives.

Liquid Propellants for Gun Applications, by WalterMorrison, John D. Knapton and Guenter Klingenberg is atechnical report which discusses the potential benefits ofliquid propellant guns. The report concludes that the primarysystem advantage is design flexibility which results fromreduced volume requirements for ammunition stowage,

I9wi iam J. Cruice, Classification of Liquid GunPropellants and Raw Materials for Transportation and Storage,ADA100729 (Rockaway, NY: Hazards Research Corporation, May1981), 1


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automation, and propellant stowage remote from the fightingcompartment. The design flexibility of liquid propellantsleads to logistical benefits in the storage, transport andammunition processing.

Logistics Analysis of the Impacts of LiquidPropellant on the Ammunition Resupply System, by Maureen MStark is a study of the co mp a~ at iv e cost and performanceanalysis of a liquid propellant gun system. The studyspecifically addresses the impact of liquid propellant on thesupply and transportation systems. The baseline vehiclestudied was a 55mrn self-propelled howitzer. A comparison wasmade not only with sol id propellant technology of today asexemplified by the bag charges used in modern artillery, butalso with possible emerging solid propellant technologiesprojected for use in the field by the year 2000 against theliquid propellant concept. Especially interesting was thediscussion on the significant savings in manpower andequipment usage when considering the effects of liquidpropellant on the m u n i t i o n resupply system. The studyconcludes that liquid propellants show a potential forreducing the requirement for personnel and equipment within

2oMorr son, 32.2'~bid.


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SumnaryThe primary research sources used in this study were

discussed and briefly related to the research topic. Thebibliography provides the complete listing of all sourcesconsulted. The parts addressed n this section of the thesisreflect the four areas of investigation: U.S. Army liquidpropellant gun development program history, the emerging gunpropulsion technologies and the criteria to evaluate them andthe logistical impact of sustaining a liquid propellantprogram in the field. Each part attempted to identify theauthor s key source material used to develop this thesis.

The most helpful sources for the author wereGovernment Technical Reports conducted at the BallisticResearch Laboratory (BRL). The BRL appears to be the leadDepartment of Defense Laboratory working the issues andattempting to develop a liquid propellant 120mn anti-armor-cannon for the main battle tank. This thesis attempts from auser point of view to support why that effort should becompleted.


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CHAPTERHISTORY OF LIQUID PROPELLANT DEVELOPMENT

IntroductionTo understand the current level of technology of a

liquid propellant gun LPG), a historical review of theDepartment of Defense DOD) LPG research and developmentefforts beginning in 1947 and continuing to the present willbe discussed. The types of LPG concepts and historicaldevelopment associated with each will be briefly explored.The goal of this portion of the study is to gain an elementaryunderstanding of the LPG and the different methods to achievegun propulsion.

Chapter 3 will not attempt to provide an in-depthanalysis of every liquid propellant LP) effort past andpresent in the DOD. Such an effort would be monumental andbeyond the limits of this thesis. The objective will be toprovide a trend of the major efforts directly after World War

and focus the reader on the current concepts which promiseapplication in the near future.

LP development in the DOD can be subdivided into fourdefined periods. The first, Post World War l l 1947-1950),explored the initial propulsion concepts in externally powered


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regenerative guns, direct injection regenerative guns and bulkloaded propel ant guns. The powered pump had to be external ymounted and was very large. The research quickly dropped theexternally powered regenerative gun for military applicationand continued on the other two.

The second period, (1950-1957), was focused on thebulk loaded propellant gun (BLPG) and the regenerative liquidpropellant gun (RLPQ). Problems related to stability duringthe interior ballistic phases and the shift from cannons torockets at the end of the Korean Conflict all but ended DODefforts in the LP program. The period from 1957-1968 saw verylittle if any research in LP.

The third period, (1968-1977), saw a relook into thepossible potential of LP in the mi itary. The major researchwas directed toward the bulk loading concept. The majorimpetus in reviving the LP program in this period was theArmy s involvement in the Vietnam War and the need to improvethe current gun propulsion technology. The Navy was the leadagency and believed LP would provide an answer to improvingthe current gun propulsion used on ship weapon systems.

The final period, 1977 to the present, began aninvestigation in LP which focused the research effortspredominantly on regenerative injection. Again the Navyinitially led the way until a Tri-Service Plan for Liquid


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Propellant Technology for Gun Application was revived in March1980' and turned into the DOD Liquid Propellant TechnologyProgram.

The Army has reached a point where the current gunpropulsion technology shows small growth potential in the nearfuture. The efforts to make combat vehicles more survivableby reducing propellant vulnerability and increasing thelethality of cannons is an on-going mission of the DODresearch and development comnunity. One current attempt tomeet this requirement is through advanced gun propulsionconcepts on the drawing board. To better understand theseconcepts, LP will be analyzed from its conception to thecurrent efforts through a historical discussion. In order, tounderstand the LP program, designers must first review the twocompeting concepts: bulk loaded liquid propellant guns(BLLPGs) and regenerative liquid propellant guns (RLPG).

'Richard H. Comer and Walter F Morrison, Tri-ServicePlan for Liquid Propellant Technology for Gun Applications,ADB055274L (Aberdeen Proving, MD: U.S. Army BallisticResearch Laboratory, September 1980), 9.alter F. Morrison, Liquid Propel lant TechnologyProgram, ADB056054L (Aberdeen Proving Ground. MD: U.S. ArmyBallistic Research Laboratory, January 1981), 5.


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PartBulk Loaded Pr o~ el la nt uns

The bulk-loaded liquid propellant gun (BLLPQ) ismechanically the simplest implementation of the liquidpropellant ~ oncept. ~ The BLLPG currently has two types ofloading methods: monopropellants, Figure 1 Schematic Diagramon a Monopropellant Bulk Loaded Propellant Gun, orbipropellants, Figure 2. Schematic Diagram of a BiopropellantBulk Loaded Propellant Gun. in both methods, the projectileis placed in the bore end of the chamber to form a seal. Thebreech is closed and the air is removed by either a venting orpreferably by vacuum line to prevent bubbles in the k u i dpropellant which can lead to a catastrophic effect during thesubsequent combustion process. The entire volume ofpropellant required to fire the projectile is pumped into thecombustion chamber at one time. in the monopropellant loadingmethod, the propellant is pumped directly from the storagetank to the chamber as shown in Figure 1 Schematic Diagram ofa Monpropellant Bulk Loaded Propellant Gun). In thebipropel ant loading method, a pump and valve system on each

halter F. Morrison, John D. Knapton and GuenterKlingenberg, Liquid Propellants for Gun Applications,ADB090195 (Aberdeen Proving Ground, MD: Ballistic ResearchLaboratory, January 1985), 9.'T.W Terry, S.R. Jackson, C.E.S. Ry ley, B.E. Jones andP.J.H. Wormell, Fighting Vehicles, (London, Great Britain:BPCC Wheatons Ltd., Exeter, 1991), 42


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FIGURE 2 SCHEM TIC Dl QR M OFBIOPROPELL NT BULK LO DED PROPELL NT QUN

38


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storage tank controls th e rate of fill into the chamber toensure both components are we1 mixed prior t o combustionS asshown in Figure 2. Schematic Diagram of a Monopropellant BulkLoaded Propellant Gun.

The next step is the combustion process as lustratedin Figure 3. Interior Ballistic Cycle of a Bulk LoadedPropellant Gun. The liquid can be ignited from one of threelocations: in the wall of the chamber, at the base of theprojectile, or in th e breech. The breech ignition can be avariety of methods ranging from electric spark to a hot wire.

Once th e combustion process is initiated,pressurization is achieved and the projectile is placed inmotion. As the projectile and liquid column are accelerateddown the tube, the gas cavity will penetrate the liquidcolumn, creating what is known as the Rayleigh-Taylorinstability. ' When this occurs, a ring of liquid remains onthe chamber walls. Hot gases flow at high velocity throughthis ring, which results in turbulent gas-liquid mixing at theinner surface of the ring which is called the Kelvin-Helmholtz

'~olfram Witt and Karlheinz Reinelt, Liquid PropellantCharges for Gun and Mortar Amnunition. International DefenseReview, Vol. 14 No. 1.1981: 65.'Morr son, 10.


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I NITIONPROJECTILE

T YLOR C VITYCH MBER

LIQUI CO TINGGUN B RREL

/

FIQURE 3 INTERIOR B LLISTIC CYCLE OFBULK LO DED PROPELL NT QU


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instability. I The Kelvin-Helmhol tz instabi ity can producethe large surface area needed for consumption of thepropellant in the gun and would also lead to very rapidcombustion after mixing in the area of t he burning surface. .aThis mechanism produces a rapid increase in the area of theburning surface.

The major difficulty with BLLPG has been variabilityin ballistics and occasional catastrophic failures of testhardware. $ Most BLLPG which have overpressured and led toa failure have been blamed on errors in ignition. Theirregular high pressures associated with bulk loading have notbeen fully controlled or understood as of yet. The criticalelement in a BLLPG appears to be the ignition system. Thecoupling in space and time of the igniter's energy to theliquid propellant (LP), controls the evolution of theballistic process. I0 As a result, the development work hasbeen done on a trial and error basis, which is not veryefficient. The studies and assessments thus far indicate

alter F Morrison, Liquid Propellants, Ball isticScience and Technoloav Tutorial Interior Ballistics, (AberdeenProving Ground, MD: U.S. Army Ballistic Research Laboratory,May 1991), 104.'Morrison, Liquid Propellants for Gun Applications, 1 1

10~orrison, all st ic Science and Technolonv Tutor a1lnterior Ballistics, 106.


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BLLPG would not be a good candidate for a possible LPG systemin a future combat vehicle.

PartRegenerative Liauid Pr o~ el la nt un

The regenerative liquid propellant gun (RLPG) ismechanically more complex than the BLLPG, but has beendemonstrated to be capable of more precise ballisticcontrol. I1 The RLPG currently has two loading methods:monopropel 1 ants, Figure 4 Schematic Diagram of aMonopropellant Regenerative Injection Liquid Propellant Gun

aInis

end bipropellants, Figure 5. Schematic Diagram ofBipropellant Regenerative Injection Liquid Propellant Gun.the RLPG, the propellant initially fills a reservoir whichseparated from the combustion chamber by a piston, and ispumped into the combustion chamber during the ballisticprocess through injectors in the piston as shown in Figure 4and Figure 5. The piston is the critical element whichdivides th e chamber into a combustion chamber and a propellantreservoir. The injector orifices in th e piston head are shownschematically in Figure 4 and Figure 5. An ignition train,

i orriso on Liquid Propellants for Gun Applications, 1 1 .4


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F I G U R E 4 S C H E H T l C D I M M M O NO PR O PE LL N TR EQ E NE R T IV E I N J E C T I O N L I Q U I D PR O PE LL N T GUN

43


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FIQURE 5 SCHEM TIC DI GR M OF BIPROPELL NTREQENER TIVE INJECTION LIQUID PROPELL NT GUN


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consisting of a primer, an ignition charge and in some casesa booster charge complete the system. I2

Two primary functions must be performed t o make theRLPG process successful. The first function is the controlledrate propellant is injected into the combustion chamber duringignition (Figure 6). As a result of this metered propellantflow, the combustion cycle is very stable and controlled sincethere is never more than a small quantity of unburnedpropel lant in the combustion chamber at any time. The abi i tyto meter the amount of propellant into the combustion chamberpermits tailoring the chamber pressure for a desiredeffect. I3 The metering pressure process is termed'regenerative' because the propellant pumping pressure isobtained by hydraulic multiplication of the combustionchamber. I4 The hydraulic action supplies the energyrequired to pump the liquid through the injectors.

I2Morrison, Ball istic Science and Technolonv TutorialInterior Ballistics, 108.

13Morrison, Liquid Propellants for Gun Applications, 1 1 .R.D.M. Furlona. Liouid Pro ~e ll an t for Future SPHowitzers? nternational defense deview Vo1 16 (December1983), 1765.


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PROPELL NT

IGNIT R

FIQURE 6 INTERIOR B LLISTIC CYCLE OFREQ ENE R TIV E I Q U I D ROPELL NT aun


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The second function is the requirement for thepropellant to be atomized as it enters the combustion chamberas shown in Figure 6. Interior Ballistic Cycle of aRegenerative Liquid Propellant Gun. This is accomplished byusing a set of injector orifices at the same location in thecombustion chamber. I5 Both functions are performed by thedifferential area piston, with propellant injection takingplace through orifices drilled through the face of the pistonas shown in Figure 5. The key is the amount of propellantavailable for combustion at any time is controlled by theinjection process. In general the process of a RLPG can bemodeled when the two functions are combined for the hydraulicresponse of the regenerative piston and the LP reservoir.This action is based on the smaller area on the unburnedpropellant side of the piston head than on the larger area onth e combustion side of the piston. This differential is thecorner stone to the injection and atomization of the LP in thecombustion process.

J . Mandzy, P.G. Cushman and T. Magoon, LiquidPropellant Technology Final Report, ADB097031 (Pittsfield,MA General Electric Ordnance Systems Division, October 1985),6.


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P a r tA Rev iew o f Pas t L iqu idP rooe l l an t Deve lo~men ts

L i q u i d p r o p e l l a n t r e s e ar c h i n t h e U n i t e d S t a te s begansh o r t l y a f t e r World War i l ended. Between 1946-1950, th r e ebas ic types o f LPG pro pu ls i on concepts were be in ginves t i ga ted : d i r e c t i n j e c t i o n , bo th ex te rn a l l y powered andregenera t ive , and bu lk loaded.'' The f i r s t was an ex te rn a l l ypowered in j e c t io n dev ice wh ich ach ieved v e lo c i t i e s up t o 7000f t / s . 7 M i l i t a r y app l i c a t i o n was cons ide red bu t wasdeterm ined no t t o be f eas ib l e due t o t he need f o r an ex te rna lpower sou rce . The second approach be in g researc he d wasexper imen ts i n bu 1k loaded LPG w i t h encapsu l 'ate d p ro pe l 1an ts .Ve lo c i t i es i n th e range o f 11,300 f t / s were repor ted .' ' Las t ,a r egene ra t i ve i n j e c t o r s t udy was comple ted and an e f f o r t t odevelop a 3 7 m RLPG was i n i t i a t e d

From 1950 t o 1957, work was conducted on bo th t h eBLLPG and RLPG co nc epts. Several 90mn tank guns wereeven tua l l y t es ted i n two sepa rate programs w i t h hyd raz idemono propellant^.^^ Problem s d eve lope d w i t h v a r i a b i l i t y i n t h e

16walter F. Mo rr iso n, Paul Q. Baer, Melv ln J Bulman andJohn Mandzy, The I n te r i o r B a l l i s t i c s o f Regene ra ti ve L i qu idP r o p e l l a n t Quns, ADA190020 (Aberdeen P ro v in g Ground, MD: U.S.Army B a l l i s t i c Research Labora tory, October 1987), 1.alter F. Morr ison, John D Knapton and Melvin J Bu lmanL iq u id P r o p e l l a n t Guns, ADA188575 (Aberdeen Pr ov in g Ground,MD: U.S. Army B a l l i s t i c Research La bo ra tor y, October 19871, 3.

I 8 l b i d .l b i d .


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bu lk l oaded f i r i n g s which exceeded t h a t o f con ven t iona l guns.F o l lo w i n g t h e end o f t h e K orean C o n f l i c t , i n t e r e s t i n LPG

research began t o d im in i sh , and by 1957, w i t h the i nc re as ingemphasis on rocke t s and m i ss i l e s , bo th ta c t i c a l and s t ra te g i c .ne ar ly a l l LPG researc h had s topped. s 20

The r i s i n g i n t e r e s t i n r o c ke t s i n t h e l a t e 1950s andth e gene ra l de c l i n e o f gun p ropu l s i on resea rch i n t he Armyne ar l y ended a1 1 suppor t o f t he LP program i n t o th e e ar l y1960s . ~ ' By t h e l a t e 1960s. t h e Vietnam War exper ien ce haddemonstra ted th e con t inue d need f o r gun systems i n a1 1a p p l i c a t io n s : a i r t o a i r , a i r defense, f i r e s up po rt , e t c . 2 2The Navy took th e l ead du r i n g t h i s p e r i o d and began th e f i r s tmajor rese arch and deve lopment e f f o r t s i n LP s in ce 1957. TheNaval Weapons Center , Ch ina Cake, began s t u d i e s on a LP cannonf o r a i r de fen se. A t t h e same tim e, t h e Naval OrdnanceS ta t i on , In di an Head, began development o f a new c la ss o fl i q u i d monopropel lan ts based on hydr oxy l amnonium n i t r a t e(HAN). These Navy programs were t h e f ou nd at io n which caused

l b i d .2 1 ~ o r r i s o n ,L i qu i d P rop e l l an ts f o r Gun A pp l i ca t i ons , 14.2 2 ~ o r r i s o n , L i q u i d P ro p el l a n t Guns, 42 3 i b i d .


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a renewed interest throughout the Department of Defenseresearch comnunity in the potential of LP.

LPG research and development in the 1970s can be brokendown into two categories: bulk loading and regenerativeinjection. Prior to 1976, bulk loading was the primary focusof the development effort, and from 1978 to the present, thefocus has shifted almost exclusively to regenerativeinjection. 24 Again the Navy lead the Department of Defenseresearch comnunity in LP development during the period. TheNavy's BLLPG program was focused toward a large calibershipboard gun and a small caliber air defense gun system. 5The Navy successfully demonstrated a small caliber 37mm airdefense gun but the ball istic control required for safety athigh rates of fire demonstrated ballistic variability whichwas still large compared to conventional guns of the samecaliber. 26 There were never any large caliber firingsconducted in con junction with this program, due to problems incontrolling high chamber variability in the 37mn testfixture. 21

141bid.2S~orrison,Liquid Propellants for Gun Applications, 142 s ~ o r rson, Liquid Prope ant Guns, 4lbid.

5


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The Defense Advanced Research Projects Agency DARPA )i n i t i a t e d c o n c u r ren t r e s e a rc h t o d ev elop a h i g h v e lo c i t y 75mmLPG cannon f o r a p p l i c a t i o n i n l i g h t armored v e h i c l e s . 8 2 8 i norder t o meet p rogram mi les tones , t e s t in g i n the p rogram wasa c c e le ra te d d e s p i t e ma rg in al s ma l l e r c a l i b e r p er fo rman ceeva lu a t ions . These deve lopment e f f o r t s concen t ra ted so le ly onth e bu lk loaded concep t due t o i t s mechan ical simp1 i c . i t y .

I n 1976, tw o s uc ce ss iv e f i r i n g s i n t h e DARPA 75mm programr e s u l t e d i n c a ta s t ro p hi c f a i l u r e . d As a r e s u l t o f t h e s emajor f a i l u r e s , a l l ma jor Department o f Defense LPG programsi n t h e U n i t e d S t a te s were t e r ~ n i n a t e d . ~ '

R esearch f o r c a nd id a te s i n l i q u i d p r o p e l l a n t s and a30mn cannon deve lopment e f f o r t s t i l l con t inued on a sma l le rsca le i n th e U.S. Army B a l l i s t i c Research Labora to ry andGeneral E l e c t r i c Company .3' I n 1978 a new fam i l y o f HAN-basedLPs was d evelo ped and a r a p i d f i r e 30mn RLPG cannon wasdemonstrated. 32 Th is caused renewed in t e r e s t i n LP by th eArmy i n th e ea r l y 1980s and a lO5mn reg ene ra t i ve t e s t f i x t u r e

1 b i d .

'Owalter F. Morr ison, Pau l O, Baer , Melv in J Bulman andJohn Mandzy, I n t e r i o r B a l l i s t i c s o f R eg en er at iv e L i q u i dP r o p e l l a n t Guns, ADA190020 (Aberdeen P ro v in g Ground, MD: U.S.Army B a l l i s t i c Research Labo ratory , October 1987), 1.3 'Morr ison, L iq u i d Pr op e l lan ts For Gun Ap p l ic a t io ns , 15.j21bid.


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was designed, fabricated and tested. The significantaccomplishments in these efforts have been the high degree ofballistic control and excellent reproducability in pressureand muzzle velocity. j3 This has resulted in the Armydeveloping and testing a 155mn RLPG system for a selfpropelled howitzer.

SumnarvThe objective of this section was to review the major

historical developments within the United States in the LPprogram from its beginning following World War to thepresent. This review identified four distinct periods inwhich LP was a possible concept as a gun propulsion system oncombat vehicles.

Initially there was a period of technologydevelopment, a feasibility demonstration conducted, andefforts toward the development of prototype hardware.Numerous gun fixtures were developed and fired but none werefielded.

The second period, 1950 to 1957, saw support for theprogram fade by the mid-1950s and all work had been abandonedby 1960. Three factors contributed to that: slow technicalprogress due to the complexities of the interior ball istics ofthe systems, reduced interest in new gun systems after theKorean conflict and the shift from guns to rockets.

SfMorrison, Liquid Propellant Guns, 5.5


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In the third period LP efforts were revived butfocused solely on the bulk loaded concept because of itsmechanical simplicity. Th e greatest test fixture failures inthe program occurred in 1976 which resulted in a shift toRLPQs

The fourth period has taken th e DOD from the late1970s to the present which has demonstrated several 1 0 5 m testfixtures wliich show great promise. Th e desire for growthpotential and increased lethality on the battlefield in a RLPQhas been shown in historical trends and is worthy of futureinvestigations in the Army.


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CHAPTERCONVENTIONAL GUN PROPULSION REVIEW

IntroductionTo establ ish a base1 ine for the major conventional gun

propulsion technologies, they be briefly analyzed for theiradvantages and disadvantages. The review includes current andadvanced technologies under development within the Departmentof Defense (DOD) research and development comnunity. The goalis to identify those concepts which show growth potential inthe near-term future as a possible improvement to the SolidPropellant Gun (SPQ). SPQs have successfully armed tanksmainly because progressive improvements made them capable ofdefeating the increasingly heavy armor of the opposing tanks,which represent their most demanding targets. ' One of themethods of increasing the penetration capability of any tankcannon without increasing the size of the gun or introducinga new technology is through increasing the energy output ofthe propellant. An objective of this improved propellant isan increased muzzle velocity which means increased weapon

R. M. Ogorkiewicz, Future Tank Guns, Part Sol id andLiquid Propellant Guns, International Defense Review. Vo1.24,No. 9/1991: 1377.5


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system lethality and increased crew survivability on themodern battlefield. The maximum velocity that can be achievedis determined by the type of propellant and the mass of theprojectile used in a gun system. Therefore, the limitingfactors become the amount of propellant that can be loaded inthe gun and the maximum pressure the gun can withstand. Theweight of propellant depends on the maximum loading density.The chapter addresses several propellant concepts whichattempt to increase the loading density. The chapter will bebroken down into conventional propulsion and advancedconventional propulsion.

PartConventional Pro~ulsion

I Conventional Propulsion chemical energy propulsiontechnology:

o Multiperforation Granular Propellantso Slotted Stick Propellantso Low Vulnerability Ammunition LOVA) Propellantso Deterred Propellantso Modular Chargeso Multiplex Charges

A Multiperforation Granular Propellants:Increasing the perforations from 1 or 7 to 9 or 37

perforation grains creates a relatively larger burning


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surface. Since the propellant gas generation rate isproportional to the burning area, it may be possible to gethigher relative pressures late in the interior ballisticcycle.

1 Advantage:Higher relative pressures may result

velocities. (It gets more usable propellant2. Disadvantages:

in higher muzzin the breech

a. Propellant grains are physically larger than thosein a standard charge, therefore, it may be difficult toachieve required loading density.

b There is a possible increase in muzzle blast whichis a survivability issue related t o the combat system.

c. The higher projectile velocities could result inincreased gun tube wear reducing the expected 1 ife of thecannon.

B Slotted Stick Propellants:The propel lant is in bundle packs which are more dense

than randomly loaded granular propellant, resulting in alarger mass being loaded into the chamber. The naturalchannels presented by bundled stick propellant allow the

'paul G Baer, Catherine F. Banz, lngo W. May and WalterF. Morrison, A Propulsion System Comparison Study For the120mn Anti-Armor Cannon, ADA187175 (Aberdeen Proving Qround,MD: U.S. Army Ball istic Research Laboratory, August l987), 13-14


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length of the chamber t o be almost immediately bathed inigniter and early combustion gases, promoting rapid flamespread because of the good pressure equilibration.

1 Advantages:a. The diminished resistance to gas flow reduces the

propensity for pressure waves and renders the potential forsimplified and less expensive charge designs.

b. The increased loading density permits the use ofthe larger charge weight needed with cooler, less energetic,propellants. These propellants result in decreased gun tubewear, muzzle flash and blast.

2. Disadvantage:Since the sticks tend to remain in the chamber during

the ballistic cycle, the propellant gases are forced to flowover the origin of rifling and erosion could possibly occur.

C LOVA Propellants:The general characteristics of LOVA propellants

consist of nitramine dispersed in an inert binder matrix.These low vulnerability properties are a result of a higherthreshold for thermal ignition, lower burning rate at lower

'~rederick W Robbins and Albert W. Horat, DetailedCharacterization of the Interior Ballistics of Slotted StickPropellant. ADA147499 (Aberdeen Proving Ground, MD: U.S.Army Ballistic Research Laboratory, September 1984), 9-11.


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pressures, and improved mechanical properties compared toconventional nitrocellulose based propellants.

1. Advantage:There is a reduction of vulnerabi 1 ity of a fire or

explosion with on-board propellant as a result of the higherflame temperature of ignition.

2. Disadvantage:There are flash and erosion problems with gun tubes

that use these propellants.

D. Deterred Propellants:Standard propellants are treated to infuse a slow

burn rate. This results in a slower burn rate in the earlyportion of the interior ball istic cycle until the deterredlayer is depleted. Then there is a more rapid burn in thelater portion of the cycle to approach a more constantpressure operation.

1 Advantage:With a constant pressure operation during the interior

ballistics cycle, higher muzzle velocities may be achievable.The loading density is not impacted though a larger charge

.s. Kirshenbaum, L. Avrami and 8 Strauss, SensitivityCharacterization of Low Vulnerability (LOVA) Propellants,ADA126130 (Dover, NJ: U.S. Army Armament Research andDevelopment Comnand, Large Caliber Weapons Systems Laboratory,March 1983), 1


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weight which is required due to the lower energy of thedeterred layer.

2. Disadvantage:The production process has not demonstrated the

capability of uniform consistent coating of a multi-perforatedpropellant grain with a deterrent.

E Multiple Charges:This concept is applicable to those situations that

require a variety of velocities from the same cannon andprojectile combination.

1 Advantage:Only the required amount of propellant is used.

2. Disadvantage:There is a potential for case residue when firing at

low pressures and cold temperatures. Also there is a possiblenon-uniform flame spread and pressure waves associated withmultiple charges.

F Multiplex Charges:The aim is to obtain a super progressivity.

Progressivity is a change in a grain's mass burning rate

L. E Harris, A Grabowsky, J. Shib-Thornton, P. Hui andA J. Beardell, Unicharge for Extended Range Ordnance, 25thJANNAF Combustion Meeting, CPlA PUB 498, Vol. IV, AD8133554(Huntsville, AL: NASA-Marshall Space Flight Center. October1988), 455-456.


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brought about by the change in the grain s surface as burningproceeds. Progressivity is desired to obtain the maximumchamber pressure very quickly and maintain it until propellantburnout.

1 Advantage:It offers the highest performance atta

conventional propulsion methods.2. Disadvantage:

i nab le with

The concept depends on th e development of graingeometries (such as rosette) that have not been manufactured.

PartAdvanced Conventional Pro~ulsion

I I Advanced Conventio.na1 Propulsion developmental enhancedchemical energy propulsion technology:

o Consolidated chargeo Enhanced Local Combustion Conceptso Programmed Fracture Propellant Graino Soft-Launch Conceptso Solid Propellant Traveling Charge

A. Consolidated Charge:consolidated charge is a charge fabricated

essentially from standard gun propellant in a way to producea monolithic structure which retains many of thecharacteristics of the initial propellant. To accomplish this


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p ro ce ss , t h e p r op e l l a n t i s f i r s t s o ft en e d w i t h a s o lv e n t, t h enp re ss ed i n t o t h e d e s i r e d b u l k d e n s i t i e s . The re i s aninc rease i n den s i t y mass by g r a i n co a t ing and b ind in g . Theconcept pe rmi ts compacted p ro pe l l an t t o be p lace i n t o the gunchamber wh ich inc reases th e ch ar ge - to -p r o je c t i l e mass r a t i of o r a g iv en chamber volume. t a t te m p ts t o m a i n t a i n h i g h e rr e a c t i v e p ressu res l a t e i n b a l l i s t i c c y cle .

1. Advantage:La rge r cha rge we igh ts can be packed i n t o a f i x e d

chamber volume, thus h i gh er muzzle v e l o c i t i e s may be ach ieved.2. Disadvantage:

The p rodu c t io n and manu fac tu r ing techno logy i sc u r r e n t l y a problem. Conso l ida ted charges may be inh er en t l ymore s u b j e c t t o r ou nd -t o- ro un d i r r e p r o d u c i b i l i t y t h a n a r e t h eloose granu r charges.

B . Enhanced Local Combustion Concepts:The ac c umu la ti on o f gases w i t h i n t h e p e r f o ra t i o n l ea ds

t o l o c a l l y h i g h p re ss ur es and f a s t e r b u r ni n g r a t e s o n i n t e r n a lsur faces. I f unders tood and con t ro l l ed , i t can be exp lo i tedas a means t o a c h ie v e ma jo r i n cre a se s i n e f f e c t i v ep r o g r e s s i v i t y .

l ~ e o n R ~ c o t t , C o ns ol id at ed P r o p e l la n t ChargeInvest iga t ion , Vo lume I Prep ara t ion o f Conso l ida ted ChargeIncre me nts, AD80433967 (Magna, Uta h: Her cu le s In c. AerospaceD i v i s i o n , November 1979), 1.


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1. Advantages:a. Lar ger charge weig hts can be employed w i t ho ut

in cr ea si ng maximum chamber pressures a l l o w in g h ig he rperformance w i t h th e same pro pe l l an t compos i t ion .

b. Inc reases i n bas ic amnun i t i on s towed load oncombat ve h ic le may be po ss ib l e i c ou pl ed w i t h t h e h i g hl o ad i ng d e n s i ty o f s t i c k p r o p e l l a n t .

2 Disadvantage:The re a re p ro blems a s s o c ia te d w i t h i n d i v i d u a l

p r o p e l l a n t g r a i n s w i t h s t a n d i n g t h e h i g h e r i n t e r n a l p re ss ur es .The prob lem i s exacerbated by tempera ture ext remes. Highte mpe ratures - enhance t h e l o c a l b u rn i n g r a t e e f f e c t . A lowte mpe rature d e te r i o r a te s p ro p e l l a n t me ch an ic al a nd b u rn r a t ep r o p e r t i e s .

C. P r o g ra m e d F r a c t u r e P r o p e l l a n t G r ai n:T h i s i s a t ec h ni qu e t o i nc re a se p r o g r e s s i v i t y . A

g i v e n p ro p e l l a n t g eometry t h a t may a l r e a dy be p ro g re s s i v e i smanufac tured such tha t t b ur ns on t h e g r a i n e x t e r i o r ad i st a nc e a t w hic h t im e t h e g r a i n w l l f r a c tu r e y i e l d i n g aprogramned inc rease i n th e ava i l a b le su r f ace a rea. Th is leadsa g a in t o i n cre a se d p re s s ure s i n t h e l a t e r p o r t i o n o f t h e c y c le


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until a specified (programned) burn of th e interior ballcycle is completed.

1 Advantages:a. A larger charge weight can be employed wi,

istic

thoutincreasing the maximum chamber pressure, allowing greatervelocities of projectiles at the same pressure or the samevelocity at lower pressures.

b. Temperature dependence may be exploited, to reducesensitivity to conditioning temperatures.

2. Disadvantages:It requires an average reproducible fracture event

which is not possible if the elimination of lot-to-lotdifferences in propellant is not achieved.

D. Soft-Launch Concepts:This concept employs propelling charge materials and

configurations which either significantly reduce theundesirable nature of gas and solid phase inputs to the shellor substantially interferes with or mitigates them beforereaching any sensitive portion of the projectile. Thisconcept exploits recent advances in high-permeability chargeand tailored-ignition methods.

a. E. Kel ler and A. W. Horst, The Effects of PropellantGrain Fracture on the Interior Ballistics of Guns, 25thJANNAF Combustion Meeting, CPlA PUB 498, Vol. IV, AD0133554(Huntsville, AL: NASA-Marshall Space Flight Center, October1988), 479-480.


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1 Advantage:This type of charge is attempting to permit firing

which ensures reliable operations of sophisticated projectilesthrough controlled interior ballistics.

2. Disadvantage:A harsher launch environment resulting from the

interior ballistic cycle might result in a decreased'probability of hit of a munition against a specific target.

E. Solid Propellant Traveling Charge:It entails affixing part the charge to the projectile

itself. Qases are generated at the base of the projecti le andpressure losses from the gun breech to the end of the gun tubeare not as great.

1 Advantage:Higher muzzle velocities may be achieved with the

current generation of munitions which couple a travelingcharge with them.

2. Disadvantages:a. The mass of the traveling charge must be

accelerated along with the projectile down the gun tube.

'~aust Denicola, Walter Arnold, Qayle Beavers, Paul Criseand Jane Krolewski, Tech Base Propulsion Technologies Effectson Weapon Systems Reliability, AD6145132 (Aberdeen ProvingGround, MD: U.S. Army Materiel Systems Analysis Activity,February 1990), 3.


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b There are severe mechanical, as well as combustionrequirements which must be overcome to make a travel ing chargeconcept successful.

c. Traveling charges tend to amplify round to rounddispersion.

SumnaryThe primary conventional gun propulsion technologies

being investigated b y the Army were reviewed in relationshipto conventional propulsion and advanced conventionalpropulsion. It gave a brief overview of each concept and theadvantages and disadvantages as currently known by the author.Higher muzzle velocities might be achievable over time withcertain concepts. The time to develop these concepts tomaturity, coupled with the associated costs, causes theresearcher and developer to explore new technologies which dolook promising in the near future over solid propellant SP)concepts. Energetic materials, such as liquid propellants,which could possibly lead to better gun propellants forimproved performance, less erosion and enhanced survivabilitycharacteristics are critical to the growth of future tankcannons. The next chapter will begin a discuss on one suchtechnology, liquid propellants, which increase the energy ofpropellants. The chapter will focus its discussion on thelogistical impact of liquid propellants as a new propulsionfor tank cannons.


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CHAPTERLOGISTICAL CONSIDERATIONS

IntroductionThere are major issues in logistics which must be

discussed if a new technology possibly to be to be fielded.One method is to draw a comparison between the base-linevehicle, a MlAl Abrams tank with a Sol id Propellant Gun SPG),and a M l l Abrams tank with a Liquid Propellant Gun LPG)continues. The chapter drawing a direct comparison betweenthe tow technologies by analyzing the issues in industrialbase conversion, production cost savings factors between SPQand LPG, comnercial production of liquid propellants LP),transportation factors, manpower resupply requirements anddemilitarization and disposal of propellants,

PartIndustrial Base Conversion

One of the key issues of many logisttcians about theuse of LPG for selected weapons is the conversion of theindustrial base to produce two types of amnunition, one forthe LPG program and one for the SPG program. Therefore, theprimary goal is to use the existing family of projectiles in


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their current configurations for LPG by reducing the number ofdesign modifications. Minimizing the number of projectilemodifications for a new weapon system results in lower costsand reduced testing for type classification for use in thefield.

The LPG program already has two advantages in the typeof projectiles required for a LPG. First, a LPG uses caselessamnunition which only requires the projectile. Secondly, thecurrent LP designs wi permit the use of M830, High ExplosiveAnti-tank, Multipurpose with Tracer (HEAT-MP-T) and M829A1,Armor Piercing Fin Stabilized Discarding Sabot with Tracer(APFSDS-T) rounds used in SPGs with minimal modification tothe current generation of projectiles.

The M829A1, APFSDS-T kinetic energy (KE) m u n i t i o nuses a subcaliber long rod penetrator stabilized in flight yfins. The design objective of a KE penetrator consists ofapplying sufficient energy at the point of attack to overmatchthe capability and strength of the target material to resistpenetration. ' Today's generat ion of long rod penetratorsachieves that design objective by traveling at supersonicspeeds and massing high concentrations of kinetic energy in arelatively small surface target area. The desired end stateis a perforation resulting in the defeat of the target.

'T.w. Terry, S.R. Jackson, C.E.S. Ryley, B.E. Jones andP.J.H. Wormell, Fishtins Vehicles (London, Great Britain: BPCCWheatons Ltd., Exeter, 1991). 28.


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Another secondary method of achieving a perforation of thetarget is through the use of chemical energy m u n i t i o n .

The M830, HEAT-MP-T chemical energy ammunition employsa high-explosive (HE) warhead to produce lethal effects ontargets. When the HEAT-MP-T round impacts a target, the fuzedetonates the HE which, in turn, fragments the casing, as we1 1as producing a highly penetrating jet of metal in the forwarddirection from the conical, copper liner at the front end ofthe casing.2 Again the desired end state is the perforationof the target. It is the residual penetrator and the debrisfragments that are the major contributors to lethal effectsinside the target once it has been perforated. ' Thecharacteristics of each of the rounds listed above aresumnarized in Table 1 Amnunition Data.

'~ndrew M. Dietrich, Warhead Mechan5cs. Ball isticScience and Technolosv Tutorial Terminal Ballistics Division,(Aberdeen Proving Ground, MD: U.S. Army Ballistic ResearchLaboratory, April 1991), 30.

u. S Army. TM 9-2350-264-10-3, Ooerators Manual. Tank,Combat. Full-Tracked: 120-mn Qun. MlAl. (2350-01-087-1092),Qeneral Abrams (Washington D.C.: Department of the Army,1991), 5-7.


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TABLE 1 AMMUNITION DATACOMPLETE ROUNDWE GHTLENGTHPROPELLANT TYPE

Just a slight modification to the M830, HEAT-MP-T and

PROJECTILETYPELENGTHWE GHTRANGE

the M829A1 in the form of a handling plug to the rear of the

M829A1 APFSDS-T46.2 lb38.7 inJA-2

projectile would make the current generation of tank fired

M830 HEAT-MP-T53 4 lb38.6 inStick DIGL-RP

APFSDS-TClassifiedClassified3000 meters

munitions interchangeable with the LPG system. The industrial

Multiple Purpose33.1 in29.8 lb2500 meters

base could continue to provide M830 HEAT-T and M829A1 APFSDS-Tto both types of gun systems until the transition wascomplete. The manufacturer would only produce projectiles forthe LP systems and complete projectiles with case for thesolid propellant SP) systems. The normal expense associatedwith a major amnunition redesign effort would not beexperienced, resulting in a much lower industrial baseconversion cost. The other critical factor which must beaddressed is propellant production by both in the SPG and the


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PartPropellant ProductionCost Savings Factors

One of the advantages to the caseless rounds in theLPG system is that manufacturing only the projectile for aweapon system would greatly reduce cost. In comparison thecurrent process of producing a SP round is very expensive andhazardous. It requires detailed and precise coating andweight specifications for each grain of propellant. Thepropellant grains must be a certain size and mass in order tomeet firing and performance table standards which predict theflight of a projectile. This process of coating weighingpropellant charge packing and assembly of propellants is verytime-consuming. The process is also hazardous and thematerials are extremely flamnable requiring strict safetystandards. The end result is a sol id one piece SP round whichrequires precision assembly and high costs.

The opposite is required for the LPG system whichconsists of two major munition components. These twocomponents propellant and projectile are not merged witheach other until they are placed together in the breech forcombustion process. The LP process eliminates the requirementto assembly a projectile and propellant at the productionplant. The projectile is manufactured separate from thepropellant. Since there are no requirements for assembly ofpropellant and projectile prior to combat operations the


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production requirements are less for LP rounds as compared toSP rounds, thus cost is reduced.

PartCommercial Production ofLiauid Pro~ellants

The current LP chosen to be used is called hydroxylamnonium nitrate (HAN). The comnercial proprietary processfor the production of HAN involves the electrolysis of nitricacid. ' The avai labi ity of natural resources at a low costmade HAN LP even more promising. With the same relativelysmall existing comnercial product