Critical Technology Events in the

Development of the Abrams Tank

Project Hindsight Revisited

Richard Chait, John Lyons, and Duncan Long 

Center for Technology and National Security Policy 

National Defense University

December 2005 
The views expressed in this report are those of the authors and do not reflect the official 

policy or position of the National Defense University, the Department of Defense, or the U.S. 

Government. All information and sources for this paper were drawn from unclassified 

materials.

Richard Chait is a Distinguished Research Professor at the Center for Technology and 

National Security Policy (CTNSP), National Defense University. He was previously Chief 

Scientist, Army Material Command, and Director, Army Research and Laboratory

Management. Dr. Chait received his Ph.D in Solid State Science from Syracuse University 

and a B.S. degree from Rensselaer Polytechnic Institute. 

John W. Lyons is a Distinguished Research Professor at CTNSP. He was previously director 

of the Army Research Laboratory and director of the National Institute of Standards and 

Technology. Dr. Lyons received his Ph.D from Washington University. He holds a B.A. from

Harvard. 

Duncan Long is a Research Associate at CTNSP. He holds a Master of International Affairs 

degree from the School of International and Public Affairs, Columbia University, and a B.A. 

from Stanford University.

Acknowledgments. A project of this magnitude and scope could not have been conducted 

without the involvement of many people. Their cooperation and willingness to recount 

events that happened many years ago made this paper possible. The Army Science and 

Technology (S&T) Executive, Dr. Thomas Killion, who requested this study, had the 

foresight to apply a “Hindsight” approach to specific Army systems, which benefits not 

only the Army technical and acquisition community but DOD and the other Services, as 

well. On-site visits were the result of the coordinating efforts of Clay Miller; David 

Hackbarth and Pearl Gendason; James Ratches; and Michael Audino for visits made to 

Warren, MI; Aberdeen, MD; Fort Belvoir, VA; and Watervliet, NY (details of the visits 

are given on p.10 of the text). Each and every person mentioned in Appendix A played an 

important role by providing valuable technical information and commentary as well as 

directing us to other contacts. Some, denoted by an asterisk, also reviewed sections in 

their area of expertise for accuracy and completeness. Also contributing greatly were the 

full text reviews provided by Robert Baer and Peter McVey (both former Abrams

Program Managers), Jerry Chapin, and Wayne Wheelock. Al Sciarretta, working with us 

under a contractual arrangement, ably assisted us by providing in-depth document 

reviews and research assistance, as well as providing relevant information based on his 

field experience while on active duty. 

Defense & Technology Papers are published by the National Defense University Center for Technology and 

National Security Policy, Fort Lesley J. McNair, Washington, DC. CTNSP publications are available online 

at http://www.ndu.edu/ctnsp/publications.html.

 ii
Contents 

I. Introduction......................................................................................................1

II. Background.....................................................................................................3

Project Hindsight ............................................................................................................ 3 

U.S. Tank Chronology .................................................................................................... 5 

III. Study Methodology........................................................................................9

Scope............................................................................................................................... 9 

Approach......................................................................................................................... 9 

IV. Armament Related CTEs.............................................................................12

Main Gun ...................................................................................................................... 12 

Gun Accuracy ............................................................................................................... 14 

Penetrators..................................................................................................................... 15 

Sabots............................................................................................................................ 18 

Propellants..................................................................................................................... 21 

V. Armor and Other Survivability Related CTEs.............................................22

Armor............................................................................................................................ 22 

Crew Protection ............................................................................................................ 24 

System Testing, Modeling, and Analysis ..................................................................... 27 

VI. Engine and Drive System CTEs .................................................................29

Engine ........................................................................................................................... 29 

Transmission................................................................................................................. 32

Track and Suspension System ...................................................................................... 34 

VII. Vetronics, C4ISR, and Fire-Control CTEs.................................................36

Vetronics....................................................................................................................... 36 

C4ISR............................................................................................................................ 37 

Thermal Imagery........................................................................................................... 39 

Fire-Control System and Related Sensors.................................................................... 41 

VIII. Findings and Concluding Remarks .........................................................45

Findings......................................................................................................................... 45 

Concluding Remarks..................................................................................................... 47 

Appendix A........................................................................................................48

Appendix B........................................................................................................52

 iii
I. Introduction 

The urge to remain militarily strong has long been a driver of technological advancement. 

This interplay between strength and technology, so evident in America’s global military 

reach, has for decades prompted U.S. defense planners to engage in technology 

forecasting. Analysis of emerging technologies was, and is, vital to making wise defense 

investments. Among the preeminent examples of such analysis are the studies undertaken 

by Theodore von Karman just after the Second World War. The von Karman reports1

represent an exhaustive review of science and technology related to the military services. 

His analysis projected the importance of unmanned aircraft, advanced jet propulsion, allweather sensors, and target seeking missiles. A steady stream of other forecasts have 

followed, such as “Strategic Technologies for the Army of the 21st Century”2

 and “New 

World Vistas—Air and Space Power for the 21st Century.”3

 

While it is important to assess the needs and challenges of the future, understanding past 

military technological successes can be equally important to defense science and 

technology (S&T) investment and management. To complement the above efforts and the 

many other technology forecasts too numerous to mention, this study is the first in a 

series that will examine some of the key factors that have led to meaningful technology 

generation and ultimate incorporation into the U.S. weapons systems we see in the field 

today. Included here are such factors as where the technical work was performed, funding 

source(s) for the effort, collaboration between government and non-government 

laboratories, and management style. This series of studies will focus only on Army 

weapons systems, beginning with the mainstay of the Army’s armor force, the Abrams 

tank. Analysis of other Army systems, such as the Apache helicopter and the Javelin and 

Stinger missiles, will follow. The results of all studies will be compiled in a wrap-up 

report that will focus on the implications of the findings for today’s S&T environment. 

We begin the paper by briefly reviewing a project that served as a source of inspiration 

for this study: Project Hindsight, a 1969 Defense Department (DOD) report.4 Hindsight

was an in-depth study sponsored by the Director of Defense Research and Engineering 

(DDR&E) that provided some insights into the development of approximately 20 

weapons systems across the DOD spectrum. Following the review of Hindsight, we 

present a short history of U.S. battle tanks as well as a summary of events leading up to 

the Army decision to replace the M60 Patton tank with the Abrams tank. This is followed 

by a description of the methodology used to gather key data on the development of the 

 

1

 Theodore von Karman, Toward New Horizons (Washington, D.C.: United States Army Air Force, 1945). 2

 Board on Army Science and Technology, Commission on Engineering and Technical Systems, National 

Research Council. Strategic Technologies for the Army of the Twenty-First Century: Technology Forecast 

Assessments (Washington, D.C.: National Academy Press, 1993). 3

 United States Air Force Scientific Advisory Board, New World Vistas: Air and Space Power for the 21st

Century: Summary Volume (Washington, D.C.: Department of Defense, 1995). 4

 Office of the Director of Defense Research and Engineering, Project Hindsight: Final Report

(Washington, D.C.: Department of Defense, 1969). 
Abrams. The information is broken out by topic area (armament related subjects; armor 

and other survivability related subjects; engine and drive system; vetronics, C4ISR and 

fire control) and presented in terms of critical technology events (CTEs). CTEs are ideas, 

concepts, models, and analyses, including key technical and managerial decisions, that 

have had a major impact on the development of a specific weapons system. CTEs can 

occur at any point in the system’s life cycle, from basic research, to advanced 

development, to testing and evaluation, to product improvements. CTEs can even relate 

to concepts that were developed but ultimately not incorporated into the weapons system. 

Also, CTEs can originate anywhere, from in-house laboratories, to private industry, to 

academia. The final portion of the paper presents the concluding remarks and findings

based on the CTEs that characterize the Abrams tank’s development. 

The CTEs are noted in the left margin throughout the report. They are summarized in 

Appendix B. CTEs are numbered only for ease of reference; there is no hierarchical or 

chronological significance to their order. 

While the link between high-tech weapons systems and battlefield success is often readily 

apparent, the geneses of and processes associated with CTEs often are not. CTEs depend 

on several important factors, including effective management, adequate funding, 

establishment of clear priorities, fostering of proper technical competencies, and 

leveraging of the resources of the private sector and academia. It is our hope that this 

retrospective look at the Abrams tank can highlight the importance of these factors, and 

thus can be of value to current S&T leadership within the Army and DOD as they wrestle 

with tight budgets, a changing workforce, and new acquisition strategies. 

 2
II. Background 

In this chapter we highlight some of the objectives and findings of the first Hindsight

report of 1969. We also present a brief chronology of U.S. tank development. Included in 

the chronology is a look at the Abrams’ predecessor, the M60 Patton tank, and at the 

requirements that were set for the design and development of the Abrams. 

Project Hindsight 

The study undertaken here is modeled in part on a 1969 report, Project Hindsight.

5

 In 

1965, the DDR&E, Dr. Harold Brown, launched a project to take a retrospective look at 

DOD investment in research and development (R&D), evaluate the results, and take stock 

of lessons learned. Brown’s overarching objectives for the study were to identify 

management factors that were associated with the utilization of the results produced by 

the DOD S&T program and to devise a methodology to measure the return on 

investment.6

 He was motivated in part by the House Committee on Defense 

Appropriations, which had questioned the efficiency of management and the overall 

payoff for the part of the Research, Development, Testing and Evaluation (RDT&E) 

program that pertained to S&T.7

 

The study was conducted by ad hoc teams of military and civilian in-house personnel. 

Some 20 weapons systems were selected for review and a set of subcommittees was 

arranged, one for each system. The systems selected for review included air-to-surface, 

ballistic, and tactical missiles; a strategic transport aircraft; a howitzer; and an antitank

projectile. Data were gathered by questionnaire and evaluated according to the following 

four criteria:8

 

1. The extent of dependence on recent advances in science or technology. 

2. The proportion of any new technology that resulted from DOD financing of 

science or technology. 

3. The management or environmental factors that appear to correlate with high

utilization of S&T results. 

4. A quantitative measure of the return on investment. 

The project teams made the following findings with respect to these criteria: 9 

1. Markedly improved weapons systems result from skillfully combining a 

considerable number of scientific and technological advances (Criterion 1). 

 

5

 Ibid. 6

 Harold Brown, Letter to the Assistant Secretary of the Army (R&D), the Assistant Secretary of the Navy 

(R&D), and the Assistant Secretary of the Air Force (R&D), 6 July 1965 in Project Hindsight: Final

Report (Washington, D.C.: Department of Defense, 1969), 135. 7

 Ibid. 8

 Ibid., xiii. 9

 Ibid, xxi. 

 3
2. More than 85 percent of the new science or technology utilized was the result of 

DOD-financed programs (Criterion 2). 

3. The utilization factor appears insensitive to environmental or management 

differences between industry, in-house laboratories, and university-associated 

S&T centers (Criterion 3). 

4. Most utilized new technological information was generated in the process of 

solving problems identified in advanced or engineering development (Criterion 

3). 

5. Most utilized new fundamental scientific information came from organized 

research programs undertaken in response to recognized problems (Criterion 3). 

6. Technological inventiveness and the utilization rate are dependent on the 

recognition of a need, an educated talent pool, capital resources, and an adequate 

communication path to potential users (Criterion 3). 

7. Any crude approximation in measuring cost-performance will tend to be delusory 

(Criterion 4). 

With regard to finding number seven, the study failed to find a satisfactory method for 

assessing cost-benefit or cost-performance from S&T work. To illustrate the difficulty 

that the study encountered, the report cited the example of the silicon-based integrated 

circuit. The circuit, invented during the period under review, revolutionized electronics 

and information technology and became a crucial part of virtually every system in the 

arsenal; there was no effective way to subdivide the effects on individual S&T programs. 

This paper will not attempt to redress this or any other shortcoming of Project Hindsight; 

Dr. Brown’s goal of quantifying the payoff of DOD investment in research and 

technology is if anything a loftier target today than it was in 1965. The fundamental 

purpose of this report, however, closely mirrors that of its predecessor: by examining the 

development of select Army systems, and in particular those signal technology events 

that propelled these systems to success, we hope to shed light on the factors that lead 

defense S&T research to fruition. 

 

In addition to sharing a broad goal with the original Hindsight report, this paper also 

takes from it a similar unit of analysis, the CTE. Hindsight evaluations were based on a 

concept called a Research and Exploratory Development (RXD) Event. In the original 

report, a RXD event has the predominant meaning of an event that “defines a scientific or 

engineering activity during a relatively brief period of time that includes the conception 

of a new idea and the initial demonstration of its feasibility.”10 There may be one or two 

such events in the development of a component or system, or a whole string of such 

events. In the case of basic research RXD events, the report distinguishes between 

undirected (curiosity driven) and directed (problem driven) work. Lastly, the final 

fabrication of the system component or device “may or may not involve an Event 

depending on the state of the technological art at the time of fabrication.”11 Please note 

that in our paper we use a definition for our signal events, CTEs, that differs from

Hindsight’s RXD event. Most significantly, as noted previously, CTEs can occur at any 

 

10 Ibid., xiv. 11 Ibid. 

 4
point in the life cycle; we leave open the possibility that CTEs might result from efforts 

that have utilized funds other than R&D. 

U.S. Tank Chronology 

The British Army first introduced the tank in combat in World War I, at the Battle of the 

Somme in 1916. Tanks were used with varying degrees of success throughout the 

remainder of the conflict. The tank’s place as a major factor in warfare was cemented in 

World War II, when German panzer divisions swept across Europe in 1939–1940. 

Though the Allies never built a tank as effective as those found in the German ranks, they 

countered with numerical superiority. Early in the war the Army deployed the M5A1 

Stuart light tank, some 8,800 of which were built and used in Africa and the Pacific 

theater. The Sherman medium tank appeared in late 1942. Though it was significantly 

overmatched by German heavy tanks, the Sherman was fast and reliable. Over 49,000 of 

these tanks were built, and thousands were shipped to American allies. The Sherman was 

in service into the 1950s. 

As the Soviet Union emerged as the obvious adversary of the future, the Sherman was 

succeeded by the M46–M47–M48 Patton series of tanks.12 The M48 Patton was in 

service from 1952 to the 1970s. It was replaced as America’s primary tank by the M60 

Patton, which incorporated most of the basic design elements of the M48. The M60 

weighed 52 tons, could travel 30 miles per hour, and was equipped with a 105mm highvelocity rifled gun. The armor was cast steel. 

In the mid 1960s, the Army began to develop a main battle tank13 to replace the M60.14

This undertaking first took the shape of the MBT70 program, a joint venture with the 

Federal Republic of Germany begun in 1963. This partnership was eventually terminated, 

and the U.S. program was redesignated the XM803. The XM803 mounted a 152mm 

gun/launcher combination capable of firing both conventional tank munitions and 

missiles. The project was canceled by the Congress in December 1971 because of high 

cost, but served, along with the last of the Patton series, the M60A3, as a significant 

technical predecessor to the Abrams series. 

The termination of the XM803 program left the M60 as America’s chief tank for the 

foreseeable future. Yet, despite incremental improvements to the M60, the Army

remained convinced that it needed a new tank design. Their main motivation lay across 

 

12 It is important to note that heavy tanks like the Patton series were not the only technological contenders

to anchor the U.S. armor force. Lighter combat vehicles, like the M41 Walker Bulldog Light Tank and the 

M551 Armored Reconnaissance Airborne Assault Vehicle (ARAAV), also received programmatic support 

(John Wiss, email to authors, 13 June 2005. All individuals cited in the footnotes appear in Appendix A, 

which lists their Abrams-era organization and their current status.) 13 American tanks were not designated as “Main Battle Tank” until the advent of the MBT70. The M46,

M47, M48, and M60 tanks were designated as “Medium Tanks.” 14 An excellent source for historical information on the Abrams is R.A. Hunnicutt, Abrams: a History of the 

American Main Battle Tank Volume 2 (Novato, CA: Presidio Press, 1990). Another useful reference is Rolf

Hilmes, Main Battle Tanks (London: Brassey’s Defence Publishers, 1987). 

 5
the intra-German border.15 In 1967, the Soviets, already ahead in quantity, fielded the 

qualitatively superior T–64 tank. The T–64 had its faults, but it boasted a 115mm gun 

(later upgraded to a 125mm) whose munitions could punch through the M60’s thickest 

armor. 

With the Soviet threat in mind, Congress authorized a new effort to develop a main battle 

tank at the same time it canceled the XM803 program (see timeline of Abrams

development at the end of the chapter). The Army set up a task force at the Armor School 

at Fort Knox, KY. With help from the Advanced Concepts Branch at Tank-Automotive 

Command (TACOM), the task force identified 19 characteristics that a new tank should 

possess. It listed them in order of importance, the first five being:16

• crew survivability; 

• surveillance and target acquisition performance; 

• high probability of hit with first round 

• time to acquire and hit a target; 

• cross-country mobility. 

The task force also issued more specific criteria, such as a 25:1 horsepower (hp) to 

weight (ton) ratio and a 46–52 ton gross weight.17 Furthermore, after the complexity and 

cost concerns that had contributed to the termination of the MBT70 and XM803 

programs, Congress required that unit cost be tightly controlled.18 An initial unit cost

ceiling of $400,000 (in 1972 dollars) was set; this figure rose to $507,790 (also in 1972 

dollars) by the time requests for proposals were issued to industry.19 This figure was 

$70,000 more than the estimated unit cost for the last M60 series tank, the M60A3, and 

$100,000 less than the estimated cost of the cancelled XM803.20 

Eight initial design contracts were given, later down-selected to two: General Motors 

(GM) and Chrysler. The designs drew on advances made in the MBT70 and XM803 

programs (for which GM was the prime U.S. contractor), and in the M60A3 (which was 

built by Chrysler). Chrysler and GM also drew on in-house laboratory R&D on 

components and design techniques, work that was not tied to any specific vehicle 

program. The Chrysler design ultimately won the competition, and Chrysler21 was given 

the contract to enter full scale engineering development of what became known as the M1 

Abrams main battle tank.

22 Production began in 1979. The Abrams went from

 

15 Orr Kelly, King of the Killing Zone (New York: W.W. Norton & Company, 1989), 19–23. 16 Ibid., 108. 17 The weight limit was later pushed to 57.5 tons. 18 R.A. Hunnicutt, Abrams: a History of the American Main Battle Tank Volume 2 (Novato, CA: Presidio

Press, 1990), 172. 

19 Ibid. 20 Ibid. 21 The Chrysler tank division was purchased by General Dynamics in 1982. General Dynamics has 

produced all versions of the Abrams from the M1A1 forward. 22 A point must be made about nomenclature. The tank did not become known as the Abrams until 1981, 

when it was type-classified as the M1 Abrams (after General Creighton Abrams, who commanded a tank

battalion in World War Two and later became Army chief of staff). The tank’s first official designation was 

 6
Congressional mandate to the field in 8 years, a journey that often took 15 to 20 years for 

other systems. Over 8,800 Abrams main battle tanks have been produced, primarily for 

the Army but also for the Marine Corps and foreign nations.23 Abrams also have been 

modified to serve as breaching vehicles, bridging vehicles, and mine-clearers. The United 

States is buying no newly built Abrams, though portions of the existing fleet receive 

periodic upgrades. The Abrams’ production timeline is provided below. 

ABRAMS PRODUCTION TIMELINE 

1971 The XM803 program is canceled. 

1971 Congress authorizes a study at Fort Knox to develop a main battle tank. The 

program is eventually designated XM1. 

1972 The Fort Knox study team issues a report on proposed characteristics for the new 

tank. 

1973 Contracts are awarded to General Motors’ Detroit Diesel Allison Division and the 

Defense Division of Chrysler Corporation to develop prototypes of the XM1. 

1976 Chrysler’s design wins the competition and is selected to become the new main 

battle tank. 

1980 The first production of the M1 Abrams is completed. The M1 remains in 

production until 1985. 

1982 Chrysler sells its tank-building division to General Dynamics. All future Abrams

and Abrams upgrades are built by General Dynamics. 

1984 The second Abrams model, the Improved Performance M1 (IPM1), is produced. 

It remains in production until 1986. The IPM1 was produced to take advantage of 

various improvements from the M1A1 program (know as the M1E1 program) 

before the full M1A1 was ready for production. 

1985 The third Abrams model, the M1A1, is produced. It remains in production until 

1993. Among other upgrades, the M1 105mm gun is replaced with a 120mm gun. 

1992 The first M1A2 tanks are produced. Existing M1 and M1A1 tanks are also 

upgraded to the M1A2 configuration. The great majority of M1A2-configured 

Abrams are upgraded versions of M1 and M1A1 tanks, but some are newproduction tanks. The M1A2 includes an independent thermal viewer for the 

commander and an Intervehicular Information System (IVIS), among other 

upgrades. 

1999 The first M1A2 System Enhancement Package (SEP) tanks are delivered to the 

Army. The M1A2 SEP has an embedded version of the Force XXI Battle 

Command, Brigade and Below (FBCB2) command and control architecture, 

improving the appliquéd version found in earlier Abrams. 

 actually XM815, quickly changed to XM1. The tank was known as XM1 throughout its development, until 

it was type-classified. To improve readability, this report sometimes refers to the Abrams and the Abrams

program even in the context of pre–1981 events. 23 GlobalSecurity.org, “M1 Abrams Main Battle Tank.” Available online at: 

<http://www.globalsecurity.org/military/systems/ground/m1-intro.htm>, accessed 9 November 2005. 

 7
In summary, the first production M1 Abrams weighed 60 tons and produced 1500hp, 

giving it the 25:1 ratio that the Army required. It had a top speed of 45mph and a cruising 

range of 275 miles. Also, per Army requirements, its survivability was much improved 

over the M60. It had more effective armor and superior crew protection features. Like the 

M60, early versions of the Abrams were equipped with a rifled 105mm gun that could 

fire a variety of ammunition. It was soon replaced with a more effective 120mm

smoothbore gun. The Abrams has evolved through several successive upgrades, the latest 

being the M1A2 SEP. After detailing the study methodology in the next chapter, chapters 

IV–VII identify the CTEs that provided the capabilities that led to the Abrams’ battlefield 

successes. 

 8
III. Study Methodology 

Scope 

We have chosen to focus this report on those things we deemed to be major technical 

developments. The Abrams has hundreds of components that undoubtedly required some

innovation, and this study neither intends to cover every CTE in the course of developing 

the tank nor to provide exhaustive technical detail on those CTEs that it does address. 

The intent is to concentrate on major technical developments that relate to the Abrams’ 

core capabilities. 

We have divided this report into four major topic areas: armament related subjects; armor 

and survivability related subjects; engine and drive system; and vetronics, C4ISR, and 

fire control. This separation of topics comes at the acknowledged price of diminished 

discussion of integration; systems engineering achievements; and the teaming of in-house 

laboratories, contractors, and the program manager (PM). The important integration work 

performed by the contractor, working closely with the PM shop and in-house 

laboratories, was vital to the final product. This fact is highlighted again in chapter VIII 

and will be the subject of additional discussion in a summary paper when the other 

reports in this series have been completed. 

Approach 

This report is based primarily on interviews and correspondence with people who were 

directly involved in the development of the Abrams. Given the technical emphasis of the 

report, we interviewed and corresponded with many technical professionals. We also 

sought out personnel who had been at the PM office and with the contractors. The 

objective of these communications was to obtain a picture of how the critical technology 

events unfolded. 

The interviews covered a broad range of pertinent topics, including the historical 

background of the developments in question. The focus of discussion, though, was the 

CTEs. We asked interviewees to identify those technology events that they considered 

critical to the development of the Abrams; to detail the impact of the CTEs; to indicate 

where the work in question was done; who contributed to it; who funded it; the nature of 

the funding (e.g., 6.1, 6.2, or 6.3);24 the number of staff involved; and the management 

factors that contributed to success. 

 

24 DOD divides Research, Development, Test and Evaluation (RDT&E) spending into seven different

activity categories. Category 6.1 refers to the budget line item for Basic Research; 6.2 is for Applied

Research; 6.3 is for Advanced Technology Development. These three categories are referred to collectively 

as S&T. 

 9
Often, we first interviewed a source and then obtained further information through 

follow-on conversations and correspondence. Though we used a questionnaire to guide 

some early discussions, we found it more fruitful to let the interviewees approach the 

subject in their own way. Almost all of the discussions began with the interviewees 

providing highlights of relevant experiences, after which we asked focused questions on 

topics not initially covered. 

It must be noted that the interviewees and correspondents were asked to relate events that 

took place as many as 40 years ago. A few of these individuals are still in government 

service but most are retired or active in the private sector. Detailed information was 

sometimes unavailable. Precise data on funding levels, for instance, were obtainable only 

intermittently. Wherever possible, we consulted multiple individuals on the same subject 

and checked their accounts against written sources. When interviewees and 

correspondents differed on what constituted a critical technology or who had made 

essential contributions, we revisited the issue until we established the most accurate 

possible picture of events. As a result, we are confident that we have captured the most 

pertinent information related to the major technical events in the development of the 

Abrams. 

As noted, we made a concerted effort to contact individuals who had played key roles in 

the Abrams tank development. Interviews were conducted both in person and by phone. 

In total, approximately 60 individuals were contacted, of whom about 50 were able to 

provide information in varying degrees. Some of these individuals were also asked to 

review selected sections for accuracy and completeness. (Appendix A lists individuals 

interviewed and their affiliations at the time of the Abrams program.) The following 

discussions were held on-site: 

• Aberdeen Proving Ground, MD, 3 November 2004; 

• Detroit Arsenal, the Abrams PM office, and General Dynamics, Warren, MI, 22–

24 November 2004; 

• Fort Belvoir, VA, 6 and18 January 2005; 

• Watervliet Arsenal, Watervliet, NY, 26 July 2005. 

Most of the individuals interviewed were employed by one of the following companies, 

in-house laboratories, or program management offices involved in the Abrams program: 

• Ballistic Research Laboratory (BRL) at Aberdeen Proving Ground (now the 

Weapons and Materials Directorate of the Army Research Laboratory at 

Aberdeen Proving Ground) 

• Armaments Research, Development and Engineering Center at Picatinny Arsenal 

• Tank-Automotive Command Research Development and Engineering Center at 

Detroit Arsenal 

• Benet Laboratories at Watervliet Arsenal (now part of the Armaments Research, 

Development and Engineering Center) 

 10
• Night Vision Laboratory at Fort Belvoir (now part of the Communications and 

Electronic Research, Development Engineering Center and known as the Night 

Vision and Electronic Sensors Directorate) 

• Chrysler Defense in Warren Michigan (now General Dynamics Land Systems) 

• Ordnance Laboratory at Frankford Arsenal (now closed, with mission transferred 

to the Armaments Research Development and Engineering Center at Picatinny 

Arsenal) 

• Program Executive Office, Ground Combat Systems (PEO GCS), located at the 

Detroit Arsenal. 

 

 11
IV. Armament Related CTEs 

We start our discussion of critical technology events with armament, covering those 

CTEs associated with the main gun and its ammunition. 

Main Gun 

When the MBT70 was being designed in the early 1970s, the U.S. Army initially wanted 

to equip it with a high performance version of the light-weight M81 152mm rifled cannon 

then used for the M551 Sheridan Armored Reconnaissance Airborne Assault Vehicle 

(ARAAV). That gun could fire guided missiles as well as high explosive, antitank 

(HEAT) rounds. The proposed gun for the MBT70 was increased in length and was 

capable of high chamber pressures to enable fin-stabilized kinetic energy ammunition to 

complement the missile and the spin-stabilized HEAT round.25 For the Abrams, however, 

the notion of combining missiles and projectiles was dropped in favor of the 105mm M68 

cannon, a proven weapon then used on most of the M60 Patton series of tanks.26 The 

M68 was a 105mm rifled gun with a suite of ammunition that included kinetic energy

ammunition (discussed at length later); spin-stabilized live and training (inert) HEAT 

rounds; high explosive plastic rounds; white phosphorus rounds; and anti-personnel 

rounds. 

The days of the M68 as the main gun were numbered, though. Even at the time it was 

selected, the Army wanted a larger gun. Though the likely candidate, a 120mm

smoothbore gun under development in the United States and West Germany, was deemed 

not ready at the time, the M1 designers were directed to provide a gun mount and turret 

that could handle the larger and heavier weapon when it became available.27 This 

forethought paid off in 1981, when the Army elected to adopt the 120mm smooth bore 

cannon. The Army purchased the gun design and the know-how and equipment to 

manufacture it from West Germany. Watervliet Arsenal installed a rotary forge, worked 

out the remaining manufacturing difficulties, and started up production of the gun. 

Progress at Watervliet Arsenal was bolstered by long experience with the manufacture of 

large gun tubes. 

CTE 1 

By 1985, the new gun was installed on the M1A1 tank model. It is important to note that 

this was a relatively rapid advance. The Army went from purchasing the gun design to 

introducing it to the tank fleet in four years. This demonstrated the advantage of the 

ongoing partnership with Germany. It also shows the importance of having an 

 

25 Common projectiles are either spin- or fin-stabilized: spin-stabilized projectiles are gyroscopically stable, 

while finned projectiles require slow roll to achieve precision. Finned projectiles can be fired from rifled

guns through the use of a special obturator that functions as a slipping clutch, while spin-stabilized 

projectiles must be fired from a rifled gun. Fins are typically canted or otherwise trimmed to maintain or

provide roll when launched from a smooth-bore cannon. 26 The sole exception was the M60A2 vehicle, which featured the M81 152mm cannon used for the M551

Sheridan armored vehicle. 27 Hunnicutt, 190. 

 12
experienced technical staff at the Benet Weapons Laboratory and the Watervliet Arsenal, 

ready and able to transfer into the Army such a complex manufacturing process and make 

it work. 

Problems with premature gun tube failure in 175mm artillery guns in Vietnam had led to 

more stringent requirements for both the materials and the manufacturing processes.28

Work at the Benet Laboratory improved the resistance of large caliber guns like the 

120mm to unexpected fast fracture. Using linear elastic fracture mechanics to assess gun 

tube failure, researchers developed an understanding of the fatigue and fracture behavior 

of the tubes, especially in solving the issues associated with brittle fracture on the 175mm

cannon.29 This work developed a new fracture toughness test specimen from a thickwalled gun barrel and a new test procedure that made use of the specimen.

30 With these 

developments, both resistance to fast fracture and the fatigue crack growth rate could be 

measured using a cost-effective test methodology. 

CTE 2 

This design information was used in conjunction with a manufacturing process known as 

autofrettage to increase gun tube life. In autofrettage (an existing process applied to large 

gun tubes at Watervliet Arsenal), the tube is subjected to internal hydraulic pressure, 

which causes plastic deformation up to halfway through the gun tube wall.31 The result is 

a significant level of compressive residual stress that remains upon removal of the 

hydraulic pressure. The residual compressive stress acts to lower the applied cyclic 

tensile stress that occurs during service. Around 1970, Watervliet Arsenal developed 

swage autofrettage, in which pressure applied by a mandrel replaces the hydraulic 

pressure.32 This process, now used world-wide, was first used on the M68 105mm gun 

and subsequently on all 120mm guns. 

CTE 3 

Additional work at Watervliet Arsenal involved electroplating, a process that had long 

been used for decorative purposes and on smaller caliber weapons. Watervliet Arsenal 

engineered this technology for depositing increased thickness chrome plating in the bore 

of the 90mm gun of the M48 tank, which was fielded in 1953.33 This process, also 

utilized for the chrome plating of the Abrams’ 120mm gun, resulted in significantly 

increased service life due to decreased erosion caused by hot propellant gases.34 

 

28 John Underwood, telephone interview with authors, 12 October 2004. 29 Ibid. Underwood, emails to authors, 12 January and 20 January, 2005. 30 J.H. Underwood and D.P. Kendall, “Fracture Toughness Testing Using the C-Shaped Specimen,” ASTM

Special Technical Publication 623, 1977. 31 T.E. Davidson et al., “Failure of a 175mm Cannon Tube and the Resolution of the Problem Using an

Autofrettage Design,” Case Studies in Fracture Mechanics, Watervliet Arsenal Report AMMRC MS 77/5, 

June 1977. 32 Underwood, email 20 January 2005. 33 Michael Audino, interview with authors, Watervliet, NY, 26 July 2005, and Michael Audino, email to

authors, 30 August 2005. 34 Ibid. 

 13
Gun Accuracy 

Another major challenge was to improve gun accuracy. As the range of U.S. and Soviet 

tank guns improved, it became clear that the battles of the future would be conducted at 

much greater distances than the tank-on-tank combat of World War II. Errors in aiming 

that were tolerable for close-in combat were unacceptable for long-range firing. A very 

slight deviation in any of a great many variables would result in aiming error. Among the 

possible sources of aiming error were imperfect sabots; erratic burning of the propellant; 

flawed gun tubes, rangefinders, or gun sights; tube droop; wind or heat; and the cant of 

the tank. 

By the time of the M1 program, the Army had already made strides in confronting these 

complex problems. In the 1960s, researchers at Frankford Arsenal put together an error 

budget (an analysis of the sources and size of the errors) for tank guns.35 Their report was 

the basis for early fire-control systems fabricated at the Arsenal. Fire control (discussed at 

greater length in the “Fire Control and Related Sensors” section) was only part of the gun 

accuracy equation, however. With rounds ejected from the gun tube at speeds in excess of 

1.6 kilometers per second, small flaws in the tube or imperfections in the shell or the 

sabot could change the trajectory of the round in a way for which no computer could 

correct. 

CTE 4 

The first step in addressing these problems was to find a way to measure the effects. 

Researchers at BRL were able to develop experimental, computational, analytical, and 

statistical models that could determine the relative magnitude of each component of 

error.36 They were then able to focus their attention on the most important variables and 

apply vector analysis to factor together the errors from the several sources.

CTE 5 

Armed with a comprehensive suite of tools to assess the critical errors, engineers were

able to address each technical challenge. The critical factor was the recognition that this 

was a system with an interdependent collection of error sources. This resulted in the 

development of a multi-disciplinary approach that created integrated high-level physicsbased models of the system. Analysis showed that lack of straightness of the gun barrel 

was one of the key sources of error. Gravity and differential heating of the gun surface 

due to sun exposure caused warping of the barrel. To compensate for the effect of 

gravity, a constant factor was applied in the fire-control software. Drawing on a concept 

used on the M60’s 105mm gun, General Dynamics designed, fabricated, and supplied a 

thermal shroud for the 120mm gun to mitigate the bend in the tube caused by sun 

exposure.37 A muzzle reference system (discussed in the Fire Control and Related 

Sensors section) enabled the fire-control system to compensate for any remaining bend. 

CTE 6 Also, a special machine press was designed at Watervliet Arsenal to address tube 

 

35 Walter Hollis, interview with authors, Arlington, VA, 7 December 2004. 36 Peter Plostins, interview with authors, Aberdeen, MD, 3 November 2004. 37 Larry Rusch, email to authors, 1 June 2005. 

 14
straightness and profile after manufacture and to correct tubes brought in from the fleet 

for overhaul.38 

This important work on gun accuracy continued over two decades. It involved many of 

the best people at BRL, Picatinny Arsenal, and Watervliet Arsenal, who collaborated 

closely with the PM office. Mission funds were provided in the Army budget in the 

amount of $1 to 2 million per year and a matching amount of customer funds came from

the PM.39 Mission funding ended in the mid 1990s. Customer funding continues to this 

day. Interviewees who worked in these organizations cited strong and patient 

management support as critical to their ability to do the work. Laboratory management

also pressed for collaborations among all the parties. 

Armament Enhancement Initiative (AEI): In 1985, AEI was launched in 

hopes of gaining a “leap-ahead” advantage over America’s Soviet adversary 

and to offset the huge numerical superiority the Soviet Union enjoyed during 

the Cold War. The AEI technology program was led by the PM, Tank Main 

Armament Systems (PM-TMAS). It was well-resourced, with expenditures 

totaling at least $100 million per year. Successes include: a suite of advanced 

kinetic energy rounds featuring improved penetrators, advanced propellant 

charge technologies, and very lightweight sabots; and a multi-purpose subcaliber HEAT projectile with a discarding sabot and a proximity fuse to 

address both ground targets and helicopters.a

 Many of the advances in sabot 

technology, penetrator technology, and propulsion technology discussed in 

the sections that follow were funded through AEI. 

 

a. Al Horst, email to authors, 4 November 2004. 

Penetrators 

The Abrams can fire two primary types of munitions: chemical energy (HEAT) rounds 

and kinetic energy (KE) long-rod penetrators. The latter rounds, which vary from 10:1 to 

30:1 in length-to-diameter ratio,40 received perhaps the greatest attention from the 

Abrams program. 

In developing the 120mm gun, the Army made the key technical decision that it should 

be optimized for long-rod penetrators.41 The bore of the 120mm gun offered a bigger 

“engine” than the 105mm; rounds could utilize 50 percent more propellant to produce 

CTE 7 

 

38 Plostins. 

39 Ibid. 40 Al Horst, Bruce Burns, and Brett Sorenson, interview with authors, Aberdeen, MD, 3 November 2004. 41 As mentioned in the section of the report on sabots, a long-rod penetrator was also developed for the 

105mm gun. 

 15
higher operating pressure so that more energy could be put into the round.42 Long-rod 

penetrators were best suited to take advantage of this additional capacity, as their armorpiercing ability comes largely from their very high KE—there is no explosive. Flight 

stability for a long-rod penetrator comes primarily from the four to six fins at the rear of 

the rod and also from some spinning—approximately 20 revolutions per second.43 

 

Figure 1: A long-rod penetrator.44

The first long rods for the Abrams (also discussed in the Sabot section of this report) 

were designed for the rifled 105mm gun. The AEI funded a larger research effort to 

perfect a long-rod penetrator for the 120mm gun. This program, which involved years of 

research in KE penetration mechanics and thousands of sub-scale experiments,45 played 

CTE 8 

 

42 Bruce Burns and William Drysdale, email to authors, 19 May 2005. 43 GlobalSecurity.org, “Large Caliber Ammunition—Types of Projectiles.” Available online at: 

<http://www.globalsecurity.org/military/systems/munitions/bullets2-types.htm>, accessed 19 July 2005. 44 SPG Media PLC, “APFSDS Ammunition—Armoured [sic] Piercing Fin-Stabilised Discarding Sabot.”

Available online at: <http://www.army-technology.com/contractors/ammunition/apfsds.htm>, accessed 21 

July 2005. 45 Randy Coates, email to authors, 13 November 2004. 

 16
an important role in the development of one of the mainstays of the Abrams’ armament, 

the M829 series of 120mm armor piercing fin-stabilized discarding sabot (APFSDS) 

rounds. 

A great deal of modeling was done to design the M829 series. For instance, early 

modeling work was done at BRL on the structure of the penetrator.46 A central goal of 

research on the structure was to craft a long rod with the highest possible ratios of length 

to diameter and also with the highest possible density, two qualities that optimize armorpiercing capability. Since the late 1950s, penetrators had been made primarily of 

tungsten. Researchers did their best to respond to improving armor technology by 

reworking the composition of the tungsten alloy used in rounds. In 1970, researchers built 

a model using finite element analysis to determine the structural integrity of the bullet. 

Staff also did systems analysis of interior, exterior, and terminal ballistics for the rods. 

Based on this modeling, researchers determined the optimal materials for use in the 

round. 

CTE 9 

Tungsten was replaced by depleted uranium (DU) in the mid 1970s. Researchers had 

previously known of DU’s superior ballistic qualities, but it was not until improvements 

in adversaries’ armor outstripped their ability to adjust the tungsten alloy that they made 

the switch to DU. Whereas tungsten penetrators became blunt as they cleaved through 

armor, crushing the tip into a mushroom shape and impeding the rod’s progress, DU has 

a self-sharpening property.47 The tip of the DU penetrator shears such that it remains 

sharp as it passes through armor. This substantially increases the range of any tank firing 

DU rounds, as even with diminished velocity a DU round can defeat a target’s armor. In 

the mid–1980s, Battelle Northwest Laboratory suggested a new process to improve the 

compressive strength of the DU rod.48 The desired strength was obtained by a thermomechanical process known as high-rate forming, which enabled the use of longer rods or 

higher length-to-diameter ratios. The Oak Ridge Y12 plant helped out as well by 

supplying tungsten and depleted uranium for the program. 

CTE 10 

CTE 11 

The M829 series has been a valuable contributor to the Abrams’ success: it helped the 

Abrams to knock out Soviet-made tanks in Iraq during Operation Desert Storm, often 

with a single shot.49 Most of the R&D on the M829 series was done in-house, with some

modifications made by the sole manufacturer, Alliant. Collaboration among BRL, 

Picatinny Arsenal, the PM shop, and the contractors was “at an all-time high.”50 The total 

funding for the penetrator work from 1984–1988 was on the order of $30 million per 

year.51 This includes funding for the associated manufacturing technology program. 

 

46 Al Horst and Bruce Burns, email to authors, 8 November 2004. 47 William S. Andrews, “Depleted Uranium on the Battlefield,” Canadian Military Journal, Spring 2003, 

43. 48 Bret Sorenson, interview with authors, Aberdeen, MD, 3 November 2004. 49 Picatinny Arsenal, “Tank Munitions Development.” Available online at:

<http://www.pica.army.mil/PicatinnyPublic/products_services/products12.asp>, accessed 19 July 2005. 50 Bruce Burns, email to authors, 8 November 2004. 51 Al Horst, Bruce Burns, and Brett Sorenson, interview with authors, Aberdeen, MD, 3 November 2004. 

 17
The Abrams has continued to benefit from advanced research on its APFSDS 

ammunition. The M829 round has been through successive generations; the most 

advanced KE round fielded today is the M829A3. Unofficial estimates indicate that the 

M829A3 has a maximum effective range of over 3,000 meters and can penetrate over 

900mm of rolled homogeneous armor at 2,000 meters.52 The result of work on 

penetration mechanics, the M829A3 is designed to mitigate the effect of reactive armor.53 

Important Facilities: Research work on penetrators and sabots drew on 

unique and vital Army resources. Supercomputers and, later, the Major 

Shared Resource Facility (one of several high performance computing 

facilities throughout DOD) at ARL-Aberdeen Proving Ground, enabled 

ballisticians to run very complex models on penetrator-target interactions 

that otherwise would have been impossible. This program, which provided 

valuable insights on how to defeat various armors, is described by a 

participant as “the most complex and thorough terminal ballistic evaluation” 

ever performed at BRL/ARL.b

 Another facility, Experimental Facility 9 at

Aberdeen Proving Ground, was constructed to handle DU in bullets and 

armor. Without this enclosed facility, full-scale firings with DU would have 

been difficult if not impossible. It should also be noted that the BRL shops 

supplied precisely machined parts and developed new techniques for making 

sabots for experimentation. 

CTE 12 

 

b. Randy Coates, email to authors, 13 November 2004.

Sabots 

Sabots are equally important to the design of a round. To achieve and maintain high 

speeds for penetration, modern KE tank ammunition is normally composed of a narrow 

long-rod penetrator surrounded by a sabot, which expands the diameter of the round to 

the full barrel diameter of the gun. The sabot enables the pressure of the propellant gases 

to push on a larger base and produce rapid acceleration of the round (see figure 2 below). 

Once outside the barrel, the sabot, which is parasitic mass, falls off, leaving the highspeed penetrator with a smaller cross-sectional area that reduces aerodynamic drag during 

flight. 

 

52 The Armor Site, “M1A1/2 Abrams.” Available online at: 

<http://www.fprado.com/armorsite/abrams.htm>, accessed 21 July 2005. 53 Randy Coates, email to authors, 13 November 2004. 

 18
Figure 2: Pressure builds behind the sabot and propels the projectile down the 

gun tube.54 

Sabots are essential to the use of long-rod penetrators, but it was difficult to adjust sabot 

technology to pair an APFSDS round with the M1’s 105mm gun. The initial KE rounds 

for the rifled 105mm gun did not have fins—they received all the spin they needed from

the rifling of the gun tube. The sabot that encased these munitions, dubbed Armor 

Piercing Discarding Sabot (APDS) rounds, was designed with a copper ring that engaged 

the rifling grooves. This sabot design was not suitable for longer rod penetrators like the 

M829 round, which rely primarily on fins to create stabilizing spin, rather than the rifling 

of the gun tube. By fully engaging the rifling of the gun tube, the APDS-type sabot would 

impose too many revolutions per second on the APFSDS round and undermine the 

stabilizing effect of its fins. In-house technical work was able to resolve this problem by 

adapting an earlier design. A slipping rotating band, or “slipping obturator,” was used on 

the 105mm HEAT rounds to prevent unwanted spin.55 The slipping obturator makes it 

possible for the round to engage the rifling of the barrel while the round itself turns at 

fewer revolutions per second than does the obturator. This concept was applied to the 

APFSDS’s sabot.56 

CTE 13 

Another challenge for APFSDS rounds was to have the sabot separate from the round 

cleanly after firing (see figure 3 below). Any strikes on or damage to the penetrator or its 

fins due to an asymmetric lift off by the sabot could cause erratic flight and significantly 

affect the probability of a hit at extended ranges. Comprehensive experimental techniques 

developed at BRL to measure all launch accuracy errors were applied to the problem.

57 A 

tipping ring was designed for the rear of the sabot that pivoted the sabot segments so that 

they were in a position to fly cleanly away from the rod.58 R&D work at Picatinny 

CTE 14 

 

54 Federation of American Scientists, “M829 120mm APFSDS-T.” Available 

online at: <http://www.fas.org/man/dod-101/sys/land/m829a1.htm>, accessed 19 July 2005. 55 Renata Price, email to authors, 6 June 2005. 56 Ibid. 57 Bruce Burns, “An Executive Summary of the M829A2 Sabot Technology Program,” Army Research

Laboratory, ARL–TR–350, February 1994. 58 Bruce Burns and William Drysdale, email to authors, 19 May 2005. 

 19
Figure 3: A representation of the final stage of sabot separation from the penetrator.59

Arsenal and BRL also produced a series of designs for the sabot focusing on exact shape 

of the scoops or ramps. The final double ramp sabot shape used on the M829 was the 

result of computer modeling by BRL.60 

In addition to crafting the precise shape of sabots, Army researchers made advances on 

their composition. Sabots were first made of steel, then of aluminum and magnesium

alloys, and today are made of composite materials. Staff at BRL used finite element stress 

analysis to establish the proper geometric design of optimized, minimum-mass, 

aluminum sabots for both the 120mm M829 and M829A1.61 They were configured, 

developed, and produced under the AEI program. The technology for the new APFSDS 

rounds was successfully transferred to Picatinny Arsenal and to industry. Several 

interviewees commented on how effectively this was accomplished.62 A technical staff 

member at BRL involved with this work was transferred to the PM office at Picatinny 

Arsenal, carrying with him intimate knowledge of the BRL work on the program. He

worked at the PM office for about two years, and then moved to industry. Thus, the 

technology was transferred by the individual as well as by written reports and periodic 

visits by other staff members. The end result was an effective technology transfer and a 

strengthening of the collaboration between BRL, Picatinny Arsenal, and industry. This 

approach was devised by the BRL Director. 

CTE 15 

CTE 16 The next step was the incorporation of composite materials. Although the finite element 

methods of the time were incapable of capturing the highly anisotropic nature of the 

sabots, especially in predicting failure of these materials, careful experimentation defined 

the lay-up of the fibers in the composite. Investigators at BRL—teamed with composite 

material specialists at the Lawrence Livermore National Laboratory and with industry—

developed the means to design the architecture and processing for the first composite 

sabot used for the M829A2 round.63 The AEI provided for a companion program that 

 

59 GlobalSecurity.org, “120 mm Ammunition.” Available online at: 

<http://www.globalsecurity.org/military/systems/munitions/120.htm>, accessed 19 July 2005. 60 Bruce Burns, email to authors, 13 November 2004, and Renata Price, interview with authors, Arlington, 

VA, 8 December 2004. 61 Burns, ARL–TR–350. 62 Dick Vitali, phone interview with authors, 8 February 2005 and John Frasier and Renata Price, interview

with authors, Arlington, VA, 8 December 2004. 63 Burns, ARL–TR–350. 

 20
established production facilities for the new composite sabot. The next variant, the 

M829A3 round, was designed using a new thermoplastic matrix material in place of the 

thermoset plastic used in the first versions. The Army-funded Center for Composite 

Materials at the University of Delaware contributed a piece of processing equipment that 

is in use at the manufacturer’s plant. 

Propellants 

 

Another crucial element of a KE tank munition, along with the penetrator and sabot, is 

the propellant. Researchers strove to create higher density, more energy, and a proper 

burn rate and burn progression.64 

Among the most important aspects of developing better propellants was modeling. In the 

1970s, a model of propellants known as NOVA (for new computer code) was developed 

at the Naval Surface Weapons Center, Indian Head.65 One of the two key researchers on 

this project transferred to BRL in 1977 to continue this work on Army problems. 

Subsequent efforts at BRL resulted in an improved computer code called the XKTC (for 

the express, kinetics, traveling charge version of NOVA). XKTC has been widely 

distributed among America’s allies.66 Studies with a scanning electron microscope 

revealed the micro-mechanisms of the behavior of the propellant in the M829 and other 

120mm rounds. 

CTE 17 

These studies led BRL investigators to develop a new propellant design that could deliver 

both more total charge mass and more efficient transfer of energy to the projectile. 

Previously, gun propellant was typically manufactured in one of two ways. In the first 

method, short cylinders with perforations provide needed increases in burning surface, 

the length of the cylinders being short to allow venting of the perforations without 

internal overpressures. The alternative was slotted, single-perforated sticks. The stick 

configuration permits good flow of ignition gases in a tightly packed bundle of sticks and 

the slot provides a vent for the single perforation. The problem with both designs was that 

the burning surface did not increase with time, and pressure dropped off rapidly as the 

projectile traveled along the tube. The BRL design incorporated partial transverse cuts at 

regular longitudinal distances in the sticks instead of a lengthwise slot, thus allowing 

multiple perforations in long, large-diameter sticks that both packed well and provided 

highly progressive gas generation rates with time.

67 This combination of features 

provided the necessary increase in interior ballistic performance. 

CTE 18 

 

64 Al Horst and Bruce Burns, email to authors, 8 November 2004. 65 Ibid. 66 Ibid. 67 Al Horst, email to authors, 8 November 2004. 

 21
V. Armor and Other Survivability Related CTEs 

The Abrams’ survivability has been instrumental to its success. The importance of armor 

developments and other improvements cannot be understated because, since the first 

major use of tanks in World War II, the lethality of antitank munitions has increased 

steadily. Israel’s tank losses in the 1973 Yom Kippur war, in the early days of the 

Abrams program, underlined the importance of developing a well-protected tank.68 

Armor 

The M48 and earlier M60 tanks had a rounded shape and made use of large monolithic 

armor castings with relatively few welded joints. To incorporate complex, nonmonolithic armors and increase design and manufacturing options, much of the Abrams 

was fabricated with rolled homogeneous steel plates, known as rolled homogeneous 

armor (RHA). The shape of the Abrams stemmed from several important concept studies 

and analyses that TACOM, in conjunction with input from other in-house laboratories, 

had authored in 1972 and 1973.69 Through the use of modeling and simulation at the U.S. 

Army Tank-Automotive Research and Development Center (TARDEC), and other 

system engineering tools, the designs of the M1 series tanks optimized the vehicle 

silhouette, the location and type of armor, the location of the crew and vulnerable 

components, and many other survivability factors.70 For example, as shown in table 1, the 

front silhouette area of the M1A2 is 12.7 percent smaller than the M60A1. It is beneficial 

to survivability to reduce tank vehicle height and present a harder target to the enemy. 

CTE 19 

Width (in) Height (in) 

M60A1 145.00 129.17

M1A2 144.00 113.60

Table 1. Comparison of the dimensions of the M60 and the Abrams.

71

While the new hull configuration optimized survivability, it demanded innovations in the 

production process and made use of many more weldments than in the M60. Drawing on 

extensive welding experience gained during WWII fabrication efforts, in-house engineers 

from several laboratories and arsenals established joint design and welding techniques to 

be used in fabricating the hull.72 Advances in welding equipment were incorporated into 

the process to optimize quality control. R&D funding in the mid-to-late 1970s that 

CTE 20 

 

68 Hans Halberstadt and Erik Halberstadt, Abrams Company (Ramsbury, England: Crowood Press, 2000), 

16. 69 Hunnicutt, 168. 70 Al Sciarretta, interview with authors, Washington, D.C., 20 May 2005. 71 Federation of American Scientists, “M60 Series Tank (Patton Series).” Available online at: 

<http://www.fas.org/man/dod-101/sys/land/m60.htm>, accessed 19 July 2005 and Federation of American 

Scientists, “M1 Abrams Main Battle Tank.” Available online at: <http://www.fas.org/man/dod101/sys/land/m1.htm>, accessed 19 July 2005. 72 Terry Higgins, telephone interview with authors, 7 February 2005. 

 22
amounted to about $3–5 million supported this work.73 The results of these efforts were 

transitioned directly to the Abrams production facilities in Michigan and Ohio. Industry 

welding and quality control personnel benefited from the direct interface with Army

welding experts.74 

Improvements in hull design and manufacture were matched by improvements in armor. 

The response to more effective antitank munitions was, for many years, to add thicker 

and thicker steel plates. But in the case of the Abrams, the conventional way of 

improving armor was not feasible. The specified weight for the XM1 was 58 tons, and 

the mobility specifications set the requirements for the power of the engine and drive 

train based on this weight.75 For the protection levels desired, RHA alone was not a 

feasible solution at a reasonable combat weight; concept studies early in the M1 program

established that lighter complex armors also would be required.76 Thus, the M1 program

started with the intent to use what the Army called “Special Armor.” 

This special armor came out of technology developed through exchanges with the United 

Kingdom and through U.S. indigenous advances. In U.S.-UK technology exchanges from

1965 to 1969, the U.S. Army was made aware of the British concept known as Chobham

armor. This work complemented parallel work in U.S. Army laboratories.77 During a 

hiatus in the exchanges, the Army continued to develop these concepts and, after 

demonstration by BRL, the technology was selected for incorporation into the XM1. 

With the signing of a Memorandum of Agreement in late 1972, the United States and the 

U.K. again engaged in armor technology discussions. When the validation contracts for 

the XM1 were signed, a team of Army specialists and representatives of the two 

contractors, Chrysler and GM, visited the U.K. to view their armor implementations. 

Lessons learned during this visit were incorporated into the contractors’ vehicles.78 These 

armor designs and implementation were unique to the M1. Throughout the development 

phases, the contractors and BRL refined the armor configurations and implementations to 

enhance vehicle survivability. 

CTE 21 

Details of the Abrams’ armor design and composition are classified, but this much can be 

said: instead of using a single material—steel—the Chobham concept uses steel over one 

or more layers of different materials, each layer designed to perform a different function

against incoming munitions. The armor is therefore a layered composite. The result is 

that one can either have protection equivalent to using only steel at a much reduced 

weight, or one can have much more protection at the same weight as a steel-only 

configuration. A great deal of research was performed to perfect the design; later 

improvements went far beyond the initial ideas.79 Developers made heavy use of 

experiments and early computer models to develop ever more complex and effective 

composite armor. 

CTE 22 

 

73 Ibid. 74 Terry Higgins, telephone interview with authors, 10 February 2005. 75 The weight of the M1A2 is approximately 70 tons. 76 Kelly, 115. 

77 Tom Havel, email to authors, 19 May 2005. 78 Hunnicutt, 178. 79 Tom Havel, Walter Rowe, and John Runyan, interview with authors, Aberdeen, MD, 3 November 2004. 

 23
Since the decision to incorporate the composite armor concept into the M1, there have

been further important armor advances. To improve protection against ever-increasing 

threats, BRL researchers, with funding from the Abrams PM office, developed new 

armor concepts, the most notable being one that incorporated DU.80 A team effort

involving BRL, the PM office, the Department of Energy (DOE), and General Dynamics 

resulted in this new technology being incorporated into the Abrams’ turret armor. 

Selected for its high density and special performance in high-shear fracture, DU makes an 

ideal armor component. This upgrade was fielded on the M1A1 and M1A2 models. As 

with the basic composite principles, the details of the upgraded armor are classified. 

CTE 23 

 

More recent advances have further bolstered the Abrams’ protection. BRL, building on 

special armor technology, developed a new side armor concept that significantly 

increased protection with minimal weight impact.81 This was handed off to the 

manufacturer, General Dynamics, and is in the latest Abrams model, the M1A2SEP.

In the armor-antiarmor race, the Army laboratories have played and continue to play a 

dominant role. All the work in the United States in this area has been funded by DOD, 

and most of it has been done in-house. These new advances were developed primarily at 

BRL, in close collaboration with other Army laboratories, DOE, and General 

Dynamics.82 Funding was provided by the Army. BRL assigned roughly 12 technical 

staff and technicians plus range crews—about 30 people in total.83 Staff at BRL—

continually seeking the optimal balance of weight, protection, and cost—continue their 

work to this day. For instance, contingency armor kits have been developed and continue 

to be advanced to provide users with options to further tailor the protection of the vehicle. 

Crew Protection 

The initial XM1 study team at Fort Knox named crew survivability as the number one 

priority for the new main battle tank. A great many of the technological advances on the 

Abrams discussed elsewhere in this report contribute to crew protection—greater speed 

and agility for less exposure to enemy fire, a lower noise signature, and better armor, to 

name a few. But while the developers of the Abrams strove to prevent the tank from

being fired upon, to prevent it from being hit if fired upon, and to stop the incoming 

round if hit, they also took into account the possibility of penetration by an enemy round, 

the risk of self-started fires, and nuclear, biological, and chemical (NBC) threats. 

Improvements in crew compartment design made one of the biggest contributions to crew 

protection. Ammunition stowage was a particular concern. The goal was to ensure that, if 

armor was compromised, the stowage system was able to limit the damage to just a single 

warhead. Ammunition was stowed openly in the turret in the Abrams’ predecessors and 

the propellant in the ammunition was such that a hit on a round would produce 

 

80 Ibid. 81 Ibid. 82 GM and Chrysler also made contributions in early design competition. 83 Havel, Rowe, and Runyan interview. 

 24
deflagration within the turret. Propellant fires cannot be extinguished by current fire 

suppression systems;84 water deluge is the extinguishing technique of choice for a 

propellant fire, but systems have not been developed for vehicle use. The rounds for the 

Abrams’ 120mm gun use highly flammable nitrocellulose cases (unlike the steel cases 

used in the 105mm variant), putting a special premium on compartment design. A 

combination of providing a separate compartment for the on-board ammunition, 

controlling burning or explosion by propellant design and separation of the rounds, and 

safely venting reaction products to the exterior of the vehicle were found to be necessary 

for crew survivability. 

Staff at BRL designed a separate compartment to stow ammunition.85 The compartment 

makes use of automatic doors to isolate the ammunition from the crew while still 

allowing the loader to easily access the rounds for firing. There was considerable effort 

on perfecting the door seals using monitors and sensors to measure air quality in the crew 

compartment during ballistic tests.86 The approach taken was later used in developing the 

protocols for ballistic evaluation of full scale testing of vehicles and structures. The 

compartment design provided sufficient venting for any explosion by installing blow-out 

panels that would direct energy from the blast away from the crew. 

CTE 24 

Researchers at BRL also addressed ammunition sensitivity and warhead shielding. 

Controlling the interaction of stowed high explosive warheads was critically important to 

an ammunition compartment concept. To this end, BRL developed less shock and crush 

sensitive warheads and included plastic shields between stowed rounds.87 The shields 

served to reduce the velocity of the detonation wave to manageable proportions. 

Researchers also developed a new test rig in an effort to study the reaction of munitions 

to impact.88 The test fixture, a 3 ton pendulum referred to as the “BRL Ballistic 

Pendulum,” quantifies the response of ammunition components to impact, thereby 

providing guidance for compartment design. 

CTE 25 

CTE 26 

R&D on crew compartment and munitions design enjoyed stable funding. Increased 

money for restructuring the crew compartment was obtained from the PM through the 

AEI. It must be noted that without the preexisting 6.1 and 6.2 research that had created 

broad expertise in propellant technology at BRL, these developments would have come

much more slowly.89 Crew protection efforts benefited from sympathetic and patient 

management, a strong support staff, and close collaboration among many participants, 

including BRL, the Navy, Picatinny Arsenal (for the manufacturing technology), other 

parts of DOD, DOE laboratories, and contractors Aerojet, Honeywell, and AAI. 

 

84 The Halon extinguishment system cannot put out a propellant fire, since the agent relies on depriving the

fire of sufficient oxygen and the propellant carries its own oxidizer. Halon is effective against petroleumbased fires. 85 Jerry Watson, Gould Gibbons, and Pat Baker, interview with authors, Aberdeen, MD, 3 November 2004. 86 Terry Dean, fax to authors, 1 August 2005. 87 Watson, Gibbons, and Baker interview. 88 Ibid. 

89 Ibid. 

 25
Another contribution to crew protection was the development of combustible casings for 

the tank rounds. In earlier tanks, there was a risk of fires started by the inadvertent 

ejection of burning debris from the tank gun breach into the turret, which had additional 

combustible casing rounds and spilled hydraulic fluid on the floor. The Abrams program

sought to avoid any such issues. To minimize accumulation of empty casings on the floor 

of the tank compartment and to reduce fire hazards, the Army had developed casings that 

were supposed to be consumed after firing in the breech, leaving only the metal base 

plate to be ejected. When the 120mm gun technology was purchased from Germany, a 

design was included for such combustible sidewalls in the casings. However, Army tests 

revealed some deficiencies, such as incomplete combustion, low strength, and trouble 

with surface coatings.

90 A team from Picatinny Arsenal and two contractors—Honeywell 

and Armtec Defense Products (now Esterline Armtec)—resolved these difficulties.91

CTE 27 

The Abrams’ design also drew on infrared sensor technology to protect the crew. Sensors 

in the Abrams’ crew compartment can detect a fire in a few milliseconds and (if it is a 

petroleum fire) extinguish it within tenths of a second using Halon agent. A similar 

system is installed in the engine compartment with provision for a manual second shot of 

Halon if a flare-up occurs.92 This upgraded fire suppression capability grew out of an 

R&D effort that was underway at TACOM in the late 1960s as a result of experiences in 

Vietnam.

93 The TACOM program funded efforts in the private sector and academia that 

significantly advanced the state of the art in key areas such as sensor technology and flow 

of the suppression agent. Total cost for fire suppression R&D, including testing, was 

approximately $1 million per year over a 10-year period.94

CTE 28 

Based on analysis of the 1973 Arab-Israeli war, and conscious that the Soviet adversary 

was armed with weapons of mass destruction, the Army pursued another area of crew 

protection for the Abrams: defense against NBC attack.95 In 1977, Congress requested 

that the Army incorporate a system that would provide decontaminated air to the crew

compartments of armored vehicles.96 Existing tanks, like the M60, then relied on a 

ventilated facepiece system (VPS) that delivered filtered air to a protective mask. The 

Army’s Edgewood Chemical Biological Center (ECBC), which had developed the VPS 

technology, was tasked with analyzing the feasibility of a hybrid collective protection 

system that would make use of both individual gear and compartment-wide filtration and 

overpressure. ECBC research indicated substantial benefits to a hybrid system, and, 

among other NBC-related work, the lab determined the necessary airflow rate and 

overpressure level.97 In 1980, ECBC awarded a contract to develop Hybrid Collective 

Protection Equipment (HCPE). This HCPE effort included the development of the NBC 

filter currently being used on the Abrams. This system was not ready in time for the M1, CTE 29 

 

90 Renata Price, email to authors, 7 July 2005. 91 Ibid. 

92 Terry Dean, fax to authors, 1 August 2005. 93 Steve McCormack, phone interview with authors, 1 February 2005. 

94 Ibid. 95 James Baker, email to authors, 7 July 2005. 96 Ibid. 97 Ibid. 

 26
which relied instead on a VPS-only system, but it has been installed on subsequent 

versions of the Abrams. 

These technical developments provided the crew with much-improved protection. Should 

a round penetrate the turret’s ammunition compartment, it is likely that only one or two

rounds will be set off and the explosion will be vented harmlessly to the outside. 

Similarly, measures taken to lessen the risk of fires started by munition casings and 

diminish the threat of an NBC attack greatly enhanced crew safety. 

System Testing, Modeling, and Analysis 

As part of the development process, DOD required full scale testing under controlled 

conditions (developmental testing) and then testing under field conditions with soldiers 

using the equipment (operational testing). Tests of armaments include firing for accuracy, 

lethality, speed, and range. Testing of armor requires live-fire tests in which selected 

portions of the complete tank are exposed to the fire of specified munitions. 

Researchers did modeling and testing work on the Abrams in response to a full range of 

threats, including nuclear blast and hacking of the on-board computers by an adversary. 

The most prominent work, though, was done on the most prominent threat: impact from 

an antitank munition. 

BRL began developing models and computer codes to predict the vulnerability of combat 

vehicles (both aircraft and ground vehicles) shortly after WWII. Until 1984, these models 

were deterministic, meaning that they could not account for the stochastic nature of the 

interaction between an attacking munition and the target vehicle. Thus, for any specific 

engagement condition, only one prediction of the outcome of the ballistic interaction 

could be made. There was no way to estimate the effect of variability on a projectile’s 

ability to defeat armor, the yaw or pitch of an attacking munition at the moment it strikes 

the target vehicle, the size and nature of the damage inflicted on internal components, and 

myriad other phenomena. 

CTE 30 

Beginning in 1984, BRL developed computer models to predict the outcome of specific 

live-fire test shots.98 When adequate input data are available, these new models account 

for the highly stochastic nature of ballistic damage. Consequently, analysts can now 

model the variability of results observed in tests or even those experienced in combat by 

generating a statistical distribution of possible outcomes of a particular test event or 

combat engagement. When data to characterize the variability of the encounter conditions 

are not available, the new models are used to provide deterministic estimates of the 

system’s vulnerability.99 The models take into account the shot trajectory, location of the 

impact on the target (including angle of attack), the physics of the penetration of the 

armor, and characteristics of the behind-armor debris (pieces of armor and pieces of the 

CTE 31 

 

98 John Beilfuss, interview with authors, Aberdeen, MD, 3 November 2004. 99 John Beilfuss, email to authors, 28 June 2005. 

 27
penetrator after it has perforated the armor).100 The behind-armor debris are characterized 

by the spatial distribution, mass, and velocity of all fragments. The model predicts which 

components or crew members will be hit by the behind-armor fragments, resulting 

damage or injury, and consequences of that damage or injury in terms of the capability of 

the vehicle to perform its intended mission. The models produce maps of target 

vulnerability viewed from any direction around or above the vehicle. The models also can 

handle indirect fire from a munition that detonates outside the target, when fragments and 

blast constitute the threat. Algorithms in these models and input data needed to run them

are based on ballistic and controlled damage tests and experiments conducted at 

Aberdeen Proving Ground and elsewhere.101 

Over the years, these models have evolved. The predominant model now used at ARL is 

called MUVES–S2,102 which is actually a computing environment containing 

approximation methods designed for specific attacking munition/target vehicle 

combinations, including aircraft and antiair munitions. 

Computer modeling yields great cost savings for testing armor and armaments. If 

vulnerability studies had to be done solely by field experimentation, performance testing 

would involve many rounds, major repairs between shots, and the sacrifice of several 

targets, such as tanks, personnel carriers, and helicopters. The cost of each live-fire shot

is substantial: $50,000 to $100,000 is not uncommon.103 With modeling, the number of 

live shots is considerably reduced, because they are used only to investigate specific 

vulnerability or lethality issues and to validate the analysis model.104 Computer modeling 

permits hundreds, if not thousands, of simulations to be run quickly and enables the 

investigation of many more engagement conditions than could be considered in even the 

most extensive test program. 

The computer modeling work on the Abrams was done in-house by the people at ARL 

using 6.2 and 6.6 mission funds and customer funds from the Abrams PM.

105 The 

development of the models was done primarily in the ARL Survivability and Lethality 

Analysis Directorate, which receives 6.2 and 6.6 mission funding. At its highest level of 

effort, this modeling work on the Abrams, including model development, involved about 

10–15 people at ARL.106 The level of effort has dropped off and currently involves only 

one or two people at ARL. 

 

100 Behind-armor fragmentation can take place even if a round doesn’t penetrate the exterior armor: the 

force of impact on the hull causes the softer metal inside the tank to burst apart, with dire results for the 

crew and sensitive instruments and ammunition. Indeed, some antitank weapons are designed to have this 

effect. 

101 John Beilfuss, email to authors, 28 June 2005. 102 Ibid. 103 Ibid. 104 Nonetheless, the testing and validation of the Abrams required many live fire tests. One participant 

recalls that “over eighty ballistic tests have been conducted on full-up and fully operational vehicles. Large 

caliber tests on full scale structures and ammunition compartments are in excess of 800.” Terry Dean, fax

to authors, 1 August 2005. 105 This is the case where funds beyond the usual categories are treated as S&T for management purposes. 106 John Beilfuss, interview with authors, Aberdeen, MD, 3 November 2004. 

 28
VI. Engine and Drive System CTEs

We now turn from armament and armor to other equally important parts of the lethalitysurvivability equation. This chapter will discuss vehicle mobility-related CTEs. 

Significant increases in engine power, transmission capabilities, and the quality of the 

suspension system have given the Abrams greater dash capability than the M60, 

especially when maneuvering uphill or across soft soil. This maneuverability reduces

exposure to enemy fire and contributes to the Abrams’ superior survivability (see table 2 

for significant survivability-related mobility differences between the Abrams and M60 

tanks). 

Engine 

The Fort Knox study team required that, whatever the weight of the Abrams, the tank 

have a 25:1 hp-to-ton ratio.107 As the weight of the M1 grew along with its armor and 

armament capability, its designers found themselves increasingly in need of a more 

powerful engine. 

The fundamental choice was between a diesel engine and a gas turbine engine. There 

were pluses and minuses to abandoning the diesel engine that was then standard in 

ground vehicles. Mostly because of more efficient fuel consumption, a diesel engine was 

better suited for situations characterized by idle time and/or low, steady speeds—the kind 

of operation associated with a defensive posture or overwatch role. The turbine engine, 

which had a higher initial cost, was considered better for offensive and highly mobile 

defensive operations, where wide-open acceleration is needed. Also, the turbine engine

worked better in cold weather, weighed less, and took up less space than the diesel 

engine. It could run on multiple types of fuel, and though it had a significant heat 

signature, the turbine engine produced less smoke and noise than a diesel engine. 

By some measures, the most obvious choice for the Abrams was the AVCR–1360 diesel 

engine. GM, the prime contractor on the XM803 program, had used this engine in its 

design for that tank. GM was also the prime U.S. contractor on the joint U.S./FRG 

MBT70 program, and had incorporated a predecessor of the AVCR–1360, the AVCR 

1100, into that design. Built by Continental Motors, the AVCR–1360 (Air-cooled, 

Variable Compression Ratio, 1,360 cubic inches) was a highly capable engine. It was a 

120o Vee, 12–cylinder, with turbo charging, supercharging, and intercooling, using 

variable compression ratio pistons. The version prepared for the XM1 was rated at 1,500 

gross horse power (GHP). This leap forward in performance was well over double the 

horsepower of its closest predecessor but raised some doubts about its long-term

durability.108 It did, however, have a long track record: development of the AVCR–1100 

began back in 1957; by 1965 the engine had accumulated 1,356 hours of test operation, 

 

107 Kelly, 98. 108 John Wiss, email to authors, 13 June 2005. 

 29
including 4,425 miles of vehicle test rig testing.109 Further, through their inclusion in two 

major (though ultimately unsuccessful) tank programs, both GM and the Army had 

considerable developmental experience with the AVCR 1100 and 1360. 

Despite the attraction of the diesel, a gas turbine engine was chosen: the AGT1500 gas 

turbine engine was part of the Chrysler design that won the XM1 competition. The roots 

of the AGT1500 lie in a TACOM effort that predates the Abrams program. Gas turbines 

had been investigated as potential combat vehicle propulsion systems ever since their 

development and installation in aircraft during the latter portion of World War II. Aircraft 

experience had demonstrated improved maintainability compared to piston engines. 

About 1960, TACOM engineers initiated an R&D program in gas turbine engine 

technology for ground vehicle applications.110 The entire multi-year (mid–1960s to mid–

1980s) turbine engine developmental program was funded to a level of about $300 

million.111 This program first investigated the potential of turbine engines, funding the 

development of three prototype engines using three different technological approaches.112

After technical analysis, TACOM set forth demanding performance specifications for an 

advanced gas turbine engine.113 Initial performance requirements specified that the 

engine produce 1,500 GHP on a 125oF day and demonstrate a best brake specific fuel 

consumption of 0.38 (pounds per hp-hour) at 80 percent engine power at that elevated 

temperature. Cold-day performance at 2,000 hp was required to assure adequate power 

for subsequent upgrades. 

CTE 32 

CTE 33 

The AGT1500 and AVCR1350 programs ensured that GM and Chrysler could choose 

between a diesel and a turbine engine as they submitted advanced development and full 

scale engineering development proposals and prototypes for the XM1 competition. Based 

most likely on the availability of developmental data and analysis, as well as the inherent 

advantages noted above, the Chrysler team selected the gas turbine engine as the 

propulsion system for its submissions, even though some in the Army favored the diesel 

engine option.114 Ultimately, though, both contractors included turbines in their designs.

In July 1976, just before DOD was to award the M1 contract to GM or Chrysler, 

Pentagon leaders decided to extend the competition and compel both companies to 

submit designs that provided for the use of either a diesel or a turbine engine. There were 

several reasons for this delay, among the most important being the preference of some 

senior civilian leaders for the turbine.

115 DOD announced that Chrysler, which had used 

the time extension to significantly lower its design’s projected unit cost, would receive 

the M1 contract, and the gas turbine engine became the power plant for the Abrams. 

There were, however, several aspects of the turbine engine that still needed to be 

addressed. An important concern was air filtration. Designers had to find a way to 

provide sufficient air cleaner volume to allow the vehicle to operate for a reasonable 

 

109 Leroy Johnson, email to authors, 10 May 2005. 110 Charles Raffa, written communication to authors, 23 November 2004. 111 Ibid. 112 Wiss. 113 Johnson. 114 Jim Mesko, Abrams in Action (Carrollton, TX: Squadron/Signal Publications, 1989), 5. 115 Kelly, 143-158. 

 30
period without cleaning the air filters. The M1 was fielded with a two-stage filter.116 A 

pre-cleaner prevented large particles from entering the intake. The rest of the particles 

were trapped by a filter called a V-Pack. When the filter became clogged an indicator 

light in the tank would alert the crew, who would have to remove the filter and clean it 

manually. Improvements were continually sought, culminating in the upgraded M1A2

filtration system. This system, developed and supplied by Donaldson Company,117 uses a 

pulse jet air cleaner that removes the need for the crew to manually clean a filter.118

Between $10 and $20 million of government funds was spent in developing the pulse jet 

air cleaner.119 

CTE 34 

There was also a need to address fuel efficiency—an idling turbine engine could consume 

over 10 gallons of fuel an hour.120 Several engineering approaches came forward to deal 

with the issue. As part of the TACOM test program, the gas turbine engine had a 

recuperator, a well-established means of improving fuel consumption by using exhaust 

gases to preheat air entering the engine's combustor. Also, there were efforts to explore 

the use of an auxiliary power unit (APU) that would provide electrical power when the 

vehicle was stationary (e.g., in a defensive posture) for long periods of time, thus 

enabling the engine to be shut down to reduce wear and fuel consumption. APUs had 

been considered for previous U.S. tanks and had been used by some British tanks. 

Evaluations of candidate external diesel and gasoline APU units obtained from industrial 

suppliers were conducted.121 The final evaluation included one bustle-mounted diesel 

APU, one bustle-mounted gasoline APU, and a fender mounted diesel APU. Based on 

this evaluation, a bustle-mounted, diesel APU was selected for production in 1991 in 

support of Operation Desert Shield.

122 Today most active Army M1A1s have the bustle 

mounted APU.123 This APU was suited to peacetime operations, but it was not the 

optimal solution for combat because the crew had to get in and out of the tank to turn it 

on, shut it off, and fill it with fuel, and because it took up storage space in the bustle and 

used different fuel.124 The Army recognizes the problems posed by an external APU and 

while awaiting an under-armor APU has added batteries to the M1A2 SEP to run the 

vehicle’s electronics without turning on the engine.125 

 

116 Irv Smith, telephone conversation with authors, 29 September 2005. 117 Herbert Dobbs, interview with authors, Arlington, VA, 7 December 2004. 118 Smith. 

119 Ibid. 120 GlobalSecurity.org, “M1 Abrams Main Battle Tank.” Available online at: 

<http://www.globalsecurity.org/military/systems/ground/m1-specs.htm>, accessed 19 July 2005. 121 The evaluation was done by a combination of PM-Abrams (TACOM), Combat Systems Test Activity 

(CSTA) at Aberdeen Proving Ground, ARL’s Harry Diamond Lab (HDL) in Adelphi, MD, and the Army

Materiel Command’s Field Assistance in Science and Technology (FAST). Al Sciarretta, email to authors, 

14 July 2005. 122 James J. Chopack et al. Development and Testing of Auxiliary Power Units for the M1A1 Tank System

(Adelphi, MD: U.S. Army Laboratory Command, Harry Diamond Laboratories, 1991), 44. 123 Irv Smith, telephone conversation with authors, 30 November 2005. 124 James J. Chopack et al. Development and Testing of Auxiliary Power Units for the M1A1 Tank System

(Adelphi, MD: U.S. Army Laboratory Command, Harry Diamond Laboratories, 1991), 31–32. 125 Roxana Tiron, “Army Future Force: Abrams Tank Still Far From Retirement,” National Defense 

Magazine, October 2004. Available online at: 

<http://www.nationaldefensemagazine.org/issues/2004/oct/Abrams%20_Tank.htm>, accessed 30 

November 2005. 

 31
Transmission 

During the same period that the diesel and turbine engine candidates were maturing, 

TACOM issued a contract to Allison Transmission, a division of GM, to develop a 

hydromechanical transmission. Allison, which had long made transmissions for Army 

ground vehicles, was directed to design a transmission that could be used with either of 

the two engine candidates. Proceeding under TACOM technical guidance, it created a 

hybrid hydrostatic-mechanical transmission, designated the XHM1500 (Cross Drive 

HydroMechanical, 1,500 HP). While the final version of this transmission, the –2 series, 

functioned well, and the hydrostatics performed very well, the hydraulic control 

technology available at the time did not have the flexibility and capability to optimally 

control the transmission.126 Furthermore, improved fuel economy—one of the primary 

reasons for choosing a hydromechanical transmission—was not shown in development 

tests. Allison ultimately recommended that the hydromechanical technology not be 

pursued for the XM1 effort. 

CTE 35 

Based on the Allison recommendation not to pursue the hydromechanical technology 

approach, TACOM contracted Allison to re-optimize an existing Allison transmission, 

the X700 (Cross Drive, 700 HP), as the X1100 (Cross Drive, 1100 Net HP). These 

contracts, totaling about $10 million, covered the redesign, fabrication, and 

demonstration/validation of the X1100 transmission for the XM1.127 

TACOM laid out several challenging requirements for the X1100.128 First, in case the 

XM1 program did not succeed, it had to fit in the M60. Second, it had to be adaptable to 

three different engines: the M60’s AVDS1790 diesel engine (again, in case the XM1 

program failed), as well as the AGT1500 gas turbine engine, and the AVCR1360 diesel 

engine (because the Army did not yet know which engine the XM1 would use). To meet 

these multiple requirements, Allison developed a transmission based on the Allison onhighway commercial transmission design. The new transmission, the X1100 is a 35-

cubic-inch, radial displacement, hydrostatic steering mechanism that remains unique in 

the world today.129 

CTE 36 

The X1100 represented a major departure from the CD850 transmission utilized in the 

Patton series tanks.130 It featured an automatic-shifting, 4–speed forward/2–speed reverse 

propulsion scheme; the CD850 had a 2–speed forward/1–speed reverse powershift. The 

X1100 also incorporated power-assisted service brakes, which allowed maximum-effort

brake stops with minimal brake pedal force; the CD850 required considerable force to 

achieve maximum braking. The above features, combined with hydrostatic speedCTE 37 

 

126 Johnson. 127 Charles Raffa, email to authors, 31 January 2005. 128 Johnson. 

129 Ibid. 130 Ibid. 

 32
controlled power steering, gave the X1100 performance and drivability never before 

available in a U.S. tank.131 

Further development of the X1100 conducted as part of the M1 Reliability and 

Maintainability/Durability and M1A1 development programs resulted in additional 

technology events worthy of note. Initial production X1100 transmissions experienced 

limited brake life and occasionally required replacement of the transmission brake plates. 

Continued development of the X1100 multi-plate, wet disk brake system has resulted in 

an extremely durable, reliable, high-performance brake system. Subsequent studies have 

validated the X1100 approach as the safest, most cost-effective system for braking a 

track-laying combat vehicle.132 

It should be noted that prior to the start of the X1100 development effort, significant 

efforts had been expended to gather duty-cycle transmission performance data on a wide 

variety of actual test courses. The analog tapes of data from these courses were 

subsequently digitized and became the basis for laboratory durability development of the 

M60A1 M1A2

Weight, Combat 

Loaded 

52.5 tons 68.7 tons 

Engine 750 hp Continental 

AVDS–1790 V–12 

diesel 

Textron-Lycoming 

AGT–1500 multi-fuel 

gas turbine with 

recuperator 

GHP (max) 750 1,500 

HP per ton 13.1 21.8 

Maximum level road 

speed 

30 mph 42 mph (governed) 

Acceleration time 0 

to 20 mph 

15 sec 7.2 sec 

Cruising Range 300 miles 298 miles 

Fuel tank 375 gal 504 gal 

Transmission Detroit Diesel Allison 

CD850 series, 2 forward 

and 1 reverse gears 

Allison X–1100–3B 

Automatic hydro-kinetic, 

hydrostatic steering, 4 

forward and 2 reverse 

gears 

Drive Rear Rear

Table 2. The engine and power train of the M60 compared to the M1A2. 

 

131 Ibid. 132 Ibid. 

 33
X1100 and all subsequent Allison military transmission products. The test regimen 

proved to be an extremely valuable tool and time yielded significant schedule and cost 

savings during transmission development.133

Track and Suspension System 

While the gas turbine engine remains the propulsion system in all the Abrams tank 

variants, there were marked changes in some of the other drive system components. 

Engineers recognized that with the increased speed and weight of the Abrams, the 

suspension system needed attention, especially if the tank was to perform well on rough 

terrain. 

The original M1 tank suspension system was developed by Chrysler for a 58 ton 

vehicle.134 The production M1A1 tank resulted in a Gross Vehicle Weight (GVW) of 65 

tons, which increased even further with the introduction of the T–158 replaceable pad 

track system and additional survivability enhancements. With the introduction of the 

M1A2 upgrades, the GVW for the tank rose to about 70 tons. The suspension system had 

to be upgraded to accommodate the additional weight and maintain a high degree of tank 

performance in terms of ride, mobility, reliability, and durability. 

The suspension system proposed for the Abrams M1A2 is known as the "Improved 

Suspension System." This system consists of larger torsion bars, which increase the 

suspension spring rate by 25 percent, and larger shock absorbers, which double the 

damping capacity.135 Aluminum torsion bar housings were designed for the undamped 

suspension stations in an effort to minimize weight increases. The hull interfaces for the 

improved suspension system were not changed. The "Improved Suspension System" was 

implemented in production on the M1A2 tank and is scheduled for the M1A1 upgrade 

tanks. 

CTE 38 

Manufacturing processes, maintenance procedures, and changes in the design of the seal 

package were developed to improve vehicle suspension assembly and maintainability.136

In particular, to produce such a robust torsion bar it was necessary to use steel in heavy 

section processed to high strength levels. For this, it was possible to utilize advanced 

heat-treating methods available in the private sector. Modest R&D efforts, funded by 

TACOM, evaluated heat-treating methods such as induction hardening and other 

thermomechanical treatments used in the private sector.137 These processing methods 

were successful in achieving the required mechanical properties and resulted in the use of 

high-strength steel for the torsion bar.

138 

 

133 Ibid. 134 Michael Blaine, email to authors, 26 May 2005. 135 Ibid. 136 Ibid. 137 Ray Cellitti, telephone interview with authors, 31 January 2005, and John Wiss, email to authors, 13

June 2005. 138 Hunnicutt, 212. 

 34
Another area that needed attention was the track system. The T–156 track system initially 

installed on the M1 had integral rubber track pads that exhibited far less track life than

designers had hoped.139 Under normal operating conditions, the integral rubber pad 

required replacement after about 700–800 miles, far short of the 2,000-mile design 

goal.140 TACOM engineers knew from prior work on ground vehicles that, despite a 

weight penalty, a replaceable track pad would increase track life. In fact, the M60 had 

replaceable track pads. TACOM funded efforts in the private sector on track design and

improved rubber compounds that would return the Abrams to this earlier track concept.141

Modest funding was provided for efforts in academia on systems engineering and 

analysis. TACOM engineers integrated and managed these efforts, providing oversight of 

design reviews and proof-of-principle testing. The result of this re-engineering effort 

(approximately 20 man-years in the mid–1980s from concept to testing) was the T–

158 track system, which had replaceable pads that met the initial track-life goals.142 

CTE 39 

In the mid 1980s, this T–158 track system was optimized for weight reduction to produce 

the T–158LL track system, which was installed on the M1A2.143 The T–158LL has the 

same form, fit, and function as the T–158, yet is 1,008 pounds lighter in weight. The T–

158LL track system allows removal of the replaceable rubber road pads to expose the 

steel tracks; this, though usually prohibited in peacetime on public roads, can improve 

traction in most conditions. Steel "ice cleat" can be installed in place of the rubber road 

pads to enhance traction over snow and ice. 

Among the most recent track system efforts was research performed in academia to 

analyze a problem with the drive sprocket on the M1A2.144 The existing sprocket teeth on

the M1A2 Abrams were designed for an optimal fit with zero track tension. However, 

during normal operating conditions, the track tensioner loaded the track with as much as 

15,000 pounds of tension. This caused the overall length of the track to increase, 

adversely affecting the interaction between the sprocket and the end-connectors and 

causing a hang-up of the track during its exit from the drive sprocket. This produced 

accelerated wear of the components and noise. The result of this effort was a new 

sprocket better suited to the high tension, resulting in a 20-percent improvement in track 

end connector wear and a reduced acoustic signature.145 

CTE 40 

An additional, modest, in-house effort at TACOM tackled the unacceptable acoustic 

signature of the track.146 Using complex signal analysis, engineers determined that the 

source of the noise was the rubbing of the track center guide against the road wheel. They 

changed the shape of the center guide and significantly reduced the signature. 

 

139 Blaine. 140 Hunnicutt, 248. 141 Dennis Sweers, telephone interview with authors, 2 February 2005. 142 Ibid. 143 Blaine. 144 Ibid. 145 Ibid. 146 Grant Gerhart, interview with authors, Warren, MI, 24 November 2004. 

 35
VII. Vetronics, C4ISR, and Fire-Control CTEs 

As a result of the armaments, survivability, and mobility CTEs discussed in chapters IV, 

V, and VI, the Abrams was a substantial improvement on the M60 Patton. Equally 

important to the tank’s success are its digital electronics, the way it operates as part of an 

effective unit on the battlefield, and its ability to find and hit the enemy. This section will 

discuss the technology events that contributed to the Abrams’ abilities in the areas of 

vetronics; command, control, communication, and computers (C4); intelligence, 

surveillance and reconnaissance (ISR); and fire control. 

Vetronics 

As the M1A1 began to evolve into the M1A2, engineers at the TACOM in-house 

laboratory proposed a radical redesign of the internal electronics using digital 

architectures.

147 The laboratory had gained ground vehicle control architecture experience 

from a late-1970s/early-1980s program in electrical power management and control 

systems. Drawing on this experience, the new electronics approach for the Abrams

became the subject of an intense R&D program. 

TACOM envisioned a significant change to the electronic integration of the Abrams

using a digital architecture approach similar to that used in aircraft. Specifically, this 

“vetronics” approach would change the arrangement from a hard-wired point-to-point 

configuration to a software-controlled multiplexed data bus approach, thus eliminating a 

significant amount of wiring. During the mid–1980s, the TACOM laboratory funded 

efforts with the private sector to confirm and demonstrate that an avionics-type 

architecture was applicable to the Abrams, could manage the electrical power, and could 

be interfaced with digital radio communication.148 Also in this time period, GDLS, 

working under a DARPA/TACOM contract as part of an advanced ground vehicle 

technology program, generated important algorithms that were applied to vetronics.149

This GDLS work formed the basis of the M1A2’s digital intravehicle architecture.150 It 

also demonstrated the digital interfaces that later enabled the Abrams’ inter-vehicle data 

transmission through the Intervehicular Information System (IVIS, discussed below).151 

CTE 41 

The Abrams vetronics architecture links onboard electronic subsystems, such as sensors 

and computers, in real time on a 1-megabit-per-second MIL-STD–1553 data bus. An 

advantage of this architecture is seen in the Abrams fire-control system. On the M60A1, 

mechanical inputs to and outputs from the ballistic computer, such as selecting 

ammunition type, were made by turning a hand crank on the computer or through metal 

shafts connected to the commander’s coincidence rangefinder (computer input) and the 

 

147 Don Sarna, interview with authors, Warren, MI, 23 November 2004. 148 TACOM, “Vetronics Evolution” summary document and Don Sarna, interview with authors, Warren, 

MI, 23 November 2004. 

149 Jerry Lane, email to authors, 2 December 2005. 150 Ibid. 151 Ibid. 

 36
main gun elevation system (computer output). As compared to the Abrams, this 

mechanical input/output was slow and prone to error.152 Lethality and survivability were 

also degraded, as the gunner had to take his eyes away from his sight to look at the 

computer during ammunition selection.153 On the Abrams, the vetronics architecture 

supports almost instantaneous, push-button selection on the gunner’s controls, provides 

connections to significantly more inputs from a variety of sensors (range, cant, wind, 

etc.), and allows more rapid adjustment of the position of the main gun. Additionally, the 

digital vetronics enables the gunner and commander to share capabilities that previously 

had been available to only one, e.g., ranging the target, sighting, and firing the main gun. 

This same vetronics architecture also supports control of the power train, mobility, other 

internal vehicle control systems, and internal/external communications. Where the M1A1 

was 90 percent analog, the M1A2 is 90 percent digital.154 

C4ISR 

While the internal systems and components on the Abrams are integrated with the 

vetronics architecture, the linking to other vehicles, foot soldiers, and commanders is 

done only with secure data links and voice radios. The vetronics digital architecture 

approach meshed nicely with an early-1980s concept put forth by the Army Science 

Board that was aimed at tying together the various pieces of information generated during 

the course of ground vehicle operations to give tank crews the ability to know where they 

are, to see what other tanks see, and to exchange information between vehicles.155 Crews

on the M60 tank had to use hand-and-arm signals or RF voice radios to communicate, a 

system that limited command and control capabilities.156 Improved battlefield 

communications and battlefield management systems held the promise of multiplying the 

Abrams’ already-formidable capabilities, and the Army leadership strongly supported this 

concept. 

CTE 42 

The Army laboratories at TACOM, Picatinny Arsenal, and the U.S. Army

Communications-Electronics Command (CECOM) moved forward in several areas 

during the 1980s and early 1990s, funding internal and external efforts to make the vision 

of using digital capability to enhance battlefield communication a reality. The concept of 

an overarching Battlefield Management System was first manifest in the Intervehicular 

Information System (IVIS).157 Communications networking architecture and protocols 

were developed by CECOM for IVIS in the late 1980s and early 1990s to allow M1A2 

tanks to communicate situational awareness information to each other and to the 

Battalion Tactical Operation Center. The communications protocol provided an efficient 

way to transmit digital data from a single M1A2 tank over the bandwidth-limited Single 

CTE 43 

 

152 Al Sciarretta, email to authors, 16 June 2005. 153 Ibid. 154 Hans Halberstadt and Erik Halberstadt, Abrams Company (Ramsbury, England: Crowood Press, 2000), 

19. 155 TACOM, “Combat Vehicle Command and Control” summary document and Don Sarna, interview with

authors, Warren, MI, 23 November 2004. 156 Al Sciarretta, email to authors, 6 February 2005. 157 Sarna. 

 37
Channel Ground and Airborne Radio System (SINCGARS) reliably.158 This was the first 

time that digital data had been communicated between M1A2 tanks in the forward areas 

of a battalion and below. 

A key enabler of this battlefield communication concept is the M1A2’s 

Position/Navigation (PosNav) system. PosNav is a nuclear-hardened, autonomous 

navigation system with a global positioning system (GPS) component.159 It was designed 

specifically for the M1A2, though other military systems have adopted it. PosNav 

provides real-time position, heading, and attitude information to the tank crew.160 

CTE 44 

The Abrams cannot rely solely on a satellite-based GPS system, because terrain often 

blocks access of the GPS receivers to satellites.161 PosNav overcomes this problem by 

coupling GPS with an inertial navigation system. Based on an initial calculation of the 

vehicle's location, PosNav uses the rotation of the track to determine the location of the 

vehicle. To compensate for track slippage that could affect the accuracy of the inertial 

system, a tank commander can use GPS to update PosNav.162 When connected to IVIS 

using the protocols described above, the system enables the creation, sharing, and 

constant updating of the battlefield picture. 

With all of the Abrams tanks on the battlefield linked together with IVIS, commanders 

can keep track of the positions of other vehicles, transmit maps, and share information 

about the enemy. The ability of a group of tanks to synchronize their fires against a target 

or targets is especially important to unit fire control. In the M60A1 units, this was done 

through much talking on the radio and much training.163 The M60A1 unit commander 

had to estimate the location of each of his tanks, as well as their orientation and fields of 

fire, but he could never really “see” what each tank was seeing. The communications and 

information-sharing advances of the Abrams significantly improve the unit commander’s 

ability to coordinate fires against enemy targets. 

During the mid–1990s, C4 capability was further enhanced by providing communication 

and radio access for crew members on all models in the Abrams fleet via the Vehicle 

Intercommunication System. This system, available for the M1A2 line and retrofitted to 

other Abrams models, consisted of the necessary hookup items and headsets. The latter 

included the capability to reduce ambient vehicle noise significantly by using an 

electronic Active Noise Reduction unit.164 The unit permitted the crew to operate within 

the 85-decibel level established by the Surgeon General without ear plugs. As a result, 

CTE 45 

 

158 Gary Blohm, email to authors, 9 March 2005. 

159 GPS, an innovation that contributes to numerous weapons systems, was based on concepts that 

emanated from DOD laboratories. Tim Coffey, interview with authors, 1 November 2005. 160 SPG Media PLC, “Smiths—Heading/Pointing and Land Navigation Systems.” Available online at: 

<http://www.army-technology.com/contractors/satellite/smiths/>, accessed 7 July 2005. 161 Al Sciarretta, email to authors, 15 July 2005. 162 U.S. Army FM17–5. Available online at: 

<http://www.nuui.com/Sections/Military/Field_Manuals/FM17-15/chp2.htm>, accessed 12 July 2005. 163 Al Sciarretta, email to authors, 16 June 2005. 164 Blohm. 

 38
commands given over the intercom are clearly heard and understood the first time, thus 

reducing the potential for fratricide and other mishaps. 

The idea of extending C4 capabilities across all battlefield elements, including other 

ground vehicles, helicopters, and artillery, was expanded upon in Force XXI Battle 

Command, Brigade and Below (FBCB2) packages that were developed by CECOM in 

the late 1980s and early 1990s.165 These packages were appliquéd into the M1A1 and 

embedded into the M1A2SEP. It was advantageous to have FBCB2 fully embedded in 

M1A2SEP to fully leverage the tank’s sophisticated digital architecture.166 The software 

system design for the SEP upgrade removed IVIS from the baseline M1A2 system

software and provided a software interface to allow the embedding of FBCB2. The 

embedded FBCB2 software was used with the upgraded SEP processors and soldiermachine interfaces, such as displays and input devices. 

CTE 46 

FBCB2 significantly enhanced situational awareness as well as command and control to 

the lowest echelons. Specifically, it provided a seamless flow of battle command 

information across a Tactical Internet system by collecting, integrating, and displaying a 

common picture of the battlefield. The development of FBCB2 was greatly helped by the 

resources available at the Tactical Internet Laboratory, which was conceived and 

developed by CECOM to optimize performance through analyses and simulations.167 

Thermal Imagery 

The digital advances of vetronics, IVIS, and FBCB2 allowed Abrams’ commanders to 

operate their 70-ton vehicles with previously unachievable agility and coordination. 

Advances in thermal imaging meant that they could use this capability in battle on a 24-

hour basis, a critical component of American military superiority. The efforts of the 

Army’s Night Vision Laboratory (now known as the U.S. Army CommunicationsElectronics Command’s Night Vision and Electronic Sensors Directorate), in concert 

with private industry and in-house applications engineers, such as those at Frankford 

Arsenal, have been instrumental in thermal-imaging advances. As a result of their work, 

the first versions of thermal-imaging systems for tanks, such as the externally mounted 

Far Infrared Thermal Indicator and the first under-armor thermal viewer device (named 

the Far Infrared Periscope), were developed in the 1960s. These early thermal devices 

were created by a strong combination of in-house research, design, and prototyping with 

industry-produced, non-standardized components. 

Non-standardized components, however, meant that the Army bore the cost of outfitting 

and maintaining a variety of thermal-imaging systems for individual weapons platforms. 

A common sensor module approach, pioneered by the Night Vision Laboratory (NVL) in 

the early 1970s, reduced the skyrocketing cost of custom imaging systems. This approach CTE 47 

 

165 Ibid. 166 Clay Miller, email to authors, 27 January 2005. 167 Blohm. 

 39
had its beginnings in an in-house study at NVL on the feasibility of such a concept.168

The report studied the community of Army thermal-imaging systems and concluded that 

it was possible to introduce a greater degree of compatibility. 

As the next step, in 1973 researchers at NVL patented a device called a Universal Viewer 

for Far Infrared. The patent described the configuration of all of the major components, 

including the detectors, imager optics, electronics, display of light emitting diodes, and 

scanning device that became the Army Common Modules.169 Subsequently, NVL funded 

primary and secondary sources for each of the modules to enhance competition and 

further reduce acquisition cost. These Common Modules were the basis for a whole 

generation of thermal imagers that the Army used not only in the Abrams, but also in 

missile systems and helicopters.170 As a result of these efforts, the Army and the other 

Services were able to achieve parts standardization and significantly reduce costs. The 

success of the approach was shown by the fact that it became accepted production 

practice by industry and has led to affordable first and second generation Forward 

Looking Infrared (FLIR) thermal imaging systems on the Abrams.

171 Savings of many 

millions of dollars have been documented in the implementation of this sensor 

modularization.172 

The Abrams benefited from significant advances in performance optimization of thermal 

sensors. Researchers at NVL very early on proposed that the ability of an observer to find 

military targets in scenes viewed through an electro-optical device was dependant on how 

well an observer can resolve bar patterns at varying spatial frequencies.173 This model 

became universally known as the Johnson model, after its inventor, who was a scientist at 

NVL. A paper published in 1970 in the classified literature, co-authored by an NVL 

researcher and an industry researcher, further quantified recognition performance in 

terms of performance related to a minimum resolvable temperature difference (MRT).174

A four-bar pattern is imaged by the system, and a human subject attempts to recognize 

the four bars on display at different spatial frequencies. A higher spatial frequency and 

lower MRT is indicative of a better system/human performance. This measurement 

technique was subsequently standardized at NVL and has became an industry standard 

for performance evaluation of infrared systems. This approach to system performance 

modeling and specification quantification was codified and documented in an Army

CTE 48

 

168 James Ratches, email to authors, 27 April 2005. The study itself is Patrick J. Daly Report of the 1971 Ad

Hoc Study Group on Commonality of Thermal-Imaging Systems (Unclassified Version), (Fort Belvoir, VA:

U.S. Army Night Vision Laboratory, 1977). 169 Daly, 77. 170 Ibid., i. 171 An excellent summary of the common module success story is found in a report written by Walter 

Morrow, Jr., while he was a scientist at NVL. Walter B. Morrow Jr. Common Modules: A Success Story

(Fort Belvoir, VA: Center for Night Vision and Electro-Optics, 1988). 172 Ratches. 173 John Johnson, “Analysis of Image Forming Systems,” Proceedings of the Image Intensifier Symposium, 

1959, n.p., 249–273. 174 J.M. Lloyd and R.L. Sendall, “Improved Specifications for Infrared Imaging Systems” Proceedings of

IRIS, 1970, 109–129. 

 40
report175 and was adopted by all three services, DOD, NATO, and the entire electrooptics community. A close working relationship between the in-house researchers at 

NVL and private industry has been key to the performance optimization of the thermalimaging systems noted above.176

The M1A2 added a commander’s independent thermal imaging system, which also was 

fabricated using the common modules approach. This system gave the tank commander a 

sighting system completely independent of the gunner, thus allowing the commander and 

the gunner to identify and track separate targets simultaneously. This development has 

significantly increased the Abrams’ lethality.177

CTE 49

Fire-Control System and Related Sensors 

Advances in thermal imaging technology gave the Abrams crew the ability to find targets 

in all conditions, be it at night or through smoke and haze. Seeing the enemy is vital, but 

it is only the first step: the Abrams must also be able to destroy the target. 

Some aspects of hitting a target have been addressed in the Gun Accuracy section. 

Another crucial contributor to meeting this challenge is the gun stabilization system. To 

improve accuracy of firing while the tank is moving, the Abrams, like most versions of 

the M60 Patton tank, is equipped with a gun turret drive stabilization system that isolates 

the gun platform from the effects of vehicle pitch, roll, and yaw. The system makes 

automatic adjustments to keep the gun trained on the target. This equipment is essential 

to the tank’s ability to fire accurately on the move. The M60A1 had such a system, which 

was designed and built by Cadillac Gage.178 Subsequent redesign by Chrysler for the 

Abrams corrected for deficiencies in the M60A1 system.

179 Over rough terrain the 

M6OA1 had a stabilized hit probability of approximately 75 percent at 1,500 meters, at 

15mph. Under the same conditions, the M1A1 has a hit probability of 95 percent at 2,200 

meters at 25mph.180 

What really sets the Abrams’ lethality apart from the M60 is the digital fire-control 

system. The advances discussed above—improved munitions, higher muzzle velocities, 

gun stabilization—combine with the fire-control system to make the Abrams a singularly 

formidable threat. 

CTE 50

The Abrams’ digital fire-control system can be thought of as combining two primary 

elements: the sensors that collect any information that might affect the flight of the round 

and the digital ballistic computer that integrates the information and generates an accurate 

 

175 James Ratches, et. al., NVL Static Performance Model for Thermal Viewing Systems U.S. Army

Electronics Command Report 7043, AD–A011212, (Fort Monmouth, N.J.: U.S. Army Electronics 

Command, 1973). 176 James Ratches and Paul Travesky, interview with authors, Fort Belvoir, VA, 18 January 2005. 177 Clay Miller, email to authors, 9 June 2005. 178 M60A1 tanks with a stabilization system were called M60A1(OAS) for Add-On Stabilization. 179 Kelly, 195. 180 Dennis W. Beal, Major, USMC, “The M1A1 Tank: Its Role in the Marine Corps.” Available online at: 

<http://www.globalsecurity.org/military/library/report/1991/BDW.htm>, accessed 7 July 2005. 

 41
firing solution. The sensors include the laser rangefinder, cant sensor, muzzle reference 

system, wind sensor, and atmospheric temperature and pressure sensors. Of these, the 

laser rangefinder and muzzle reference system in particular deserve further discussion. 

The laser rangefinder replaced the dual mirror-based coincidence rangefinder found on 

the M60A1.181 The M60’s rangefinder needed constant adjustment and was susceptible to 

temperature and moisture. It took a well-trained crew 7–10 seconds to put a round on 

target. The Abrams’ rangefinder, on the other hand, reduces the round-on-target time to 

2–3 seconds from target acquisition and has a range three times greater than that of the 

M60A1.182 

The ruby laser, the first successful optical laser, was the basis for the first type-classified, 

man-portable rangefinder in the mid-1960s. In the 1970s, Army researchers first 

developed laser rangefinders based on Neodymium: Yttrium Aluminum Garnet (Nd: 

YAG) lasers. These laser rangefinder units achieved two pulses per second, and with 

continued research efforts the output was increased to 10 pulses per second.183 The 

advantage of the Nd: YAG system over the ruby laser system was that they could be run 

at higher repetition rates and higher output energies and could operate more covertly, 

primarily because of thermal stability.

184 

CTE 51

With all the advantages of the Nd: YAG laser, there was one disadvantage that required 

attention: Nd: YAG lasers were not eyesafe because of their operational wave length 

(1.06 microns). Over the years, many investigators have worked on eyesafe replacements 

to the Nd: YAG laser. Several approaches were considered. One was to pass the original 

laser beam through a methanol cell, which caused the wave length to shift.185 Others 

included using an optical parametric oscillator, a special crystal, to convert the frequency 

of the laser output to the eyesafe region (such as 1.5 microns) and developing new 

materials that emit at eye-safe wavelengths.186 These efforts yielded an industrydeveloped eyesafe Erbium laser rangefinder, which replaced the Nd: YAG laser on the 

Abrams.

187

CTE 52

Another important development in the Abrams’ fire-control sensor suite was the addition 

of a muzzle reference system (MRS). The concept of an MRS stemmed from the early 

1970s, when field inspections indicated that a substantial portion of the U.S. tank fleet 

had improperly adjusted guns. In August 1972, a team of fire-control designers from

Frankford Arsenal filed a patent for an MRS that used a flat mirror fixed to the muzzle of 

the gun.188 In this design, a beam of light emanates from the gunner’s periscope and 

CTE 53 

 

181 Ibid. 182 Ibid. 183 Joseph Lehman, email to authors, 17 March 2005. 184 It should be noted that once the Nd: YAG laser was perfected and was being utilized in weapons 

systems, it opened the door for commercial applications in areas such as medicine and metals joining. 185 Maurice Yeager, telephone interview with authors, 16 March 2005. 186 Ratches, email. 187 Eugene Del Coco, email to authors, 29 August 2005 and DefenceJournal.com, “Abrams M1A1/2.” 

Available online at <http://www.defencejournal.com/jul99/abrams.htm>, accessed 30 November 2005. 188 Joseph Lehman, email to authors, 1 June 2005. 

 42
reflects to the muzzle mirror. This provides compensatory azimuth and elevational error 

signals which are algebraically added to azimuth and elevational range signals produced 

by a ballistic computer in response to a rangefinder sighted on a target. The MRS 

positions a movable reticle correctly in the periscope to enable the gunner to aim the gun 

accurately, thereby increasing first-round-hit probability. Later, more advanced MRSs 

utilized an automated sensor mounted on the turret wand that measured the deviation of 

the muzzle with respect to that fixed point on the turret. 

To field a rugged system, Benet Laboratories at Watervliet Arsenal did extensive analysis 

associated with the mechanical attachment of the Abrams’ muzzle sensor unit to the gun 

tube.189 During the early years of fielding, there were many instances of breakage of 

internal optical components, loosening of the muzzle sensor on the tube, and loss of 

calibration (alignment of tube and optics). At that time (late 1980s–early 1990s), Benet 

technologists discovered a previously unknown dynamic strain wave that travels axially 

through the gun tube walls along with high-speed, KE projectiles.190 It was found that 

when the projectile approaches the so-called “critical velocity” of the dynamic strain 

wave, severe resonances occur that greatly amplify local strains and accelerations in the 

tube—enough to cause the MRS damage being observed. General Dynamics used this 

information to modify muzzle sensor design to maintain functionality.191 Since that time, 

Benet has developed gun tube design techniques that can mitigate these dynamic strain 

waves and prevent MRS damage. 

CTE 54 

Information from the laser rangefinder, the muzzle reference system, and other sensors 

are collected and provided to the other primary component of the fire-control system, the 

Abrams’ digital ballistic computer. The digital computer aboard the Abrams, which 

benefited from the well-documented development of the U.S. computer and electronics 

industry, represents a major leap forward from the analog system used by the M60A1. 

CTE 55 

The work that led to the M60’s automated fire-control systems was done at BRL and 

Frankford Arsenal in the 1960s using first mechanical computation methods and then an 

analog computational approach.192 One such analog computer, the M16, went into the 

M60 tank. It was initially patented in the 1970s by engineers from Frankford Arsenal,193

and later versions were jointly patented by the original inventors and an engineer from 

Hughes Aircraft. This fire-control system used a periscope sight with a ballistic reticle, a 

coincidence rangefinder, and an analog ballistic computer that required the gunner to 

manually select the type of ammunition. The ballistic reticle assisted the gunner in 

adjusting fire and leading moving targets. The rangefinder and ammunition selection 

compensated for only two of the essential variables involved in putting a round on target. 

 

189 Ibid. 

190 Rick Hasenbein, email to authors, 23 May 2005. 191 Lehman, 1 June 2005. 192 Lehman, 17 March 2005. 193 Ira Goldberg et al., U.S. Patent No. 3686478 (Washington, DC: U.S. Patent Trademark Office, 1972);

Paul Marasco, U.S. Patent No. 3733465 (Washington, DC: U.S. Patent Trademark Office, 1973); Paul 

Marasco et al., U.S. Patent No. 3743818 (Washington, DC: U.S. Patent Trademark Office, 1973). 

 43
In the 1970s, engineers at Frankford Arsenal were able to develop a digitized fire 

computer with greatly improved speed and accuracy.194 The Abrams’ gunner manually 

inputs ammunition type, temperature, and barometric pressure. The computer integrates 

the data, takes into account such things as how much the target should be led, based on 

the range and speed of the target and the speed of the Abrams, and generates a firing

solution. The software in the computer draws on instrumented experiments, computer 

modeling of the system errors, and confirming field firings (as discussed in the System

Testing, Modeling, and Analysis section) to account for the possible errors in the firing

sequence, including range, cant, wind, speed, and gun firing jump. With digital 

processing capability to integrate the data, the Abrams is able to swiftly acquire a target

and bring accurate fire to bear. 

 

194 Lehman, 17 March 2005.

 44
VIII. Findings and Concluding Remarks 

Findings 

1. We have identified the following distribution of 55 critical technology events in the 

development of the Abrams tank. 

• Armaments and Armor CTEs

o Main Gun: 3 

o Gun Accuracy: 3 

o Penetrators: 5 

o [Sidebar on Important Facilities: 1] 

o Sabots: 4 

o Propellants: 2 

o Armor: 5 

o Crew Protection: 6 

o System Testing, Modeling, and Analysis: 2 

• Engine and Drive System CTEs 

o Engine: 3 

o Transmission: 3 

o Track and Suspension System: 3 

• Vetronics, C4ISR, and Fire-Control CTEs 

o Vetronics: 1 

o C4ISR: 5 

o Thermal Imaging: 3 

o Fire-Control System and Related Sensors: 6 

2. The funding for the development of these CTEs came almost entirely from DOD. There 

are many aspects of the Abrams that utilize Army-unique technologies, such as armor and 

armaments, crew protection, and fire control and its components. These were all funded 

by DOD, either in-house or on contracts. Other critical technologies have broader 

applicability and have received additional support from industry. Examples are found in 

the power train and suspension system, computers, and communications. Some of the 

technologies began as strictly military items but later found their way into civilian 

systems, like GPS. 

3. The Army did not develop the Abrams all on its own: while some CTEs emanated from 

the in-house laboratories, others came from industry, academia, and abroad. Here it is 

worthwhile to restate what was said in the Introduction: the goal of this paper is to 

identify CTEs related to the development of the Abrams tank. The focus on technical 

events should in no way diminish the importance of the close team environment that 

existed between in-house laboratories, the PM office, and industry to the success of the 

Abrams program. The result of this close working relationship was the effective 

transitioning of CTEs noted in this paper. 

 45
4. Systems integration was key to the transitioning process. This function was overseen 

by the Abrams PM office and implemented by Chrysler/General Dynamics. Good 

teamwork was evident in the system integration process. Though (as was noted in the 

Study Methodology chapter) this paper did not detail the integrative role played by these 

parties, their work in this regard was vital and it required an intimate knowledge of the 

systems and components and their intended use. As was noted in the Sabot section in 

chapter IV, the transfer of in-house personnel to team with the PM office was an effective 

way of integrating advanced concepts. Throughout its lifecycle, the Abrams development 

program reaped the rewards of close collaboration and teamwork among all of the 

Abrams program members. 

5. We have five findings regarding the in-house laboratories: 

a. A staff of highly skilled/experienced engineers and scientists and the right 

equipment and facilities to do the work were critically important. These 

capabilities enabled the Army laboratories to recognize valuable new ideas, 

concepts, and promising technologies and to apply them to the Abrams tank 

development. The Abrams’ developers drew heavily on their prior experience. 

In many cases, this experience was gained only through long service in militaryspecific S&T areas. To cite only one example, the technologists who improved 

the resistance of the 120mm gun to brittle fracture were informed by their past 

work on other weapons, most notably the 175mm artillery piece. 

b. The Army also benefited from prior investments in unique research 

equipment and facilities. At Aberdeen Proving Ground, for example, there was 

research instrumentation for measuring the behavior of propellants, penetrators, 

sabots, and gun tubes under the extraordinary conditions of launch. Similarly, 

the Night Vision and Electronic Sensors Laboratory at Fort Belvoir developed 

instruments and techniques that were essential to the work of contractors. This 

equipment enabled the laboratories to push the state of the art in night vision. 

c. Even where the in-house laboratories were not directly responsible for a 

CTE, they often played a crucial role. The in-house laboratories often passed 

the findings of their R&D to industry for use in technology developments. 

When the technology came from other sources, the in-house laboratories 

performed an important role in taking new ideas and adapting and perfecting 

them to fit into the overall design. Both these functions drew on the in-house 

laboratories’ existing body of professional expertise, tools, and facilities. Either 

by laying the groundwork for other advances or making existing innovations 

useful to Abrams, the in-house laboratories made essential contributions without 

which the new ideas would have been dropped. 

d. The in-house laboratories were most deeply involved in those CTEs that 

pertained to requirements unique to ground combat vehicles. CTEs in these 

 46
areas—composite armor, the 120mm gun, improved crew protection, the more 

powerful gas turbine engine, the digital command and control applications, and 

so on—were at the core of what made the Abrams so much better than its 

predecessors. 

e. The in-house laboratory management created a supportive and patient 

environment for the technical staff. The management was responsive to the 

needs of the users. Many of the interviewees noted the role of management in 

allowing and encouraging the staff to explore new ideas. In most cases—not 

all—whatever funding was needed was supplied. In virtually all cases relations 

among the different in-house laboratories, the PM shop, and the contractors 

were described as close and productive. This was sometimes accomplished by 

moving staff to meet project needs, even if it meant locating them at industry 

facilities. Also, the user played an important part in identifying the threats and 

stating the needs. The role of Fort Knox exemplifies this. 

Concluding Remarks 

These findings and conclusions apply to the Abrams tank and may not apply to other 

Army weapons systems. While the results of this report have suggested to us some

general recommendations that likely would apply to other Army weapons systems, we

will reserve judgment until we have completed subsequent papers on additional 

platforms. Also left until we complete the papers on additional systems will be any 

comments related to current matters of interest, such as acquisition strategies and the 

technical personnel skill mix. 

We would like to emphasize again that this study has not set out to capture every 

technical innovation in the development of the Abrams. Nor have we striven to present 

the CTEs in exhaustive technical detail. We are confident, however, that we have 

captured most of the major technical events pertaining to the tank, and that these events 

support the above conclusions. 

 47
Appendix A 

Individuals Contacted for the Abrams Project 

Key 

Civil Service 

Employee 

 CSE Academia ACD Active 

Military 

 AM

Government

Retired 

 GR Military Retired MR Private Sector 

Retired 

PSR

Consultant CST Private Sector Employee PSE Contractor CTR

* denotes that the individual reviewed some or all of the draft document for completeness and 

accuracy. 

Last Name First 

Name 

Abrams-era Organization Current Status 

Audino Michael Watervliet Arsenal (CSE) CSE

*Baer Robert Abrams PM Office (AM) MR 

Baker James Edgewood Arsenal (CSE) CSE 

Baker Patrick Ballistic Research Laboratory 

(CSE) 

CSE 

Bartle David Abrams PM Office (CSE) PSE 

*Beilfuss John Harry Diamond Laboratory 

(CSE) 

CSE 

*Blaine Michael Tank-Automotive Command

(CSE) 

CSE 

*Blohm Gary Communications-Electronics

Command (CSE) 

CSE 

Bolon Michael Chrysler/General Dynamics

(PSE) 

PSE

*Burns Bruce Ballistic Research Laboratory 

(CSE) 

CSE

Buser Rudy Night Vision Laboratory 

(CSE) 

GR, CST 

Cardine Chris Abrams PM Office (AM) MR, PSE 

Cellitti Ray International Harvester (PSE) PSR, CST 

Cerrato Louis Frankford Arsenal/Armament

Research, Development and 

Engineering Center (CSE) 

CSE

Coates Randy Ballistic Research Laboratory 

(CSE) 

CSE

*Chapin Jerry Abrams PM Office (CSE) GR, PSE 

*Dean Terry Abrams PM Office (CSE) CSE 

DeBusscher David Chrysler/General Dynamics

(PSE) 

PSE

 48
Del Coco Eugene Frankford Arsenal/Armament 

Research, Development and 

Engineering Center (CSE) 

GR, CST 

Dobbs Herbert Tank Automotive Research, 

Development and Engineering 

Center (AM/CSE) 

GR, CST 

*Drysdale William Ballistic Research Laboratory 

(CSE) 

CSE

Foos Michael Tank-Automotive Command

(CSE) 

CSE

Frasier John Ballistic Research Laboratory 

(CSE) 

GR, CST 

*Furmanski Donald Frankford Arsenal/Armament

Research, Development and 

Engineering Center (CSE) 

GR, CST 

Gerhart Grant Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

*Gibbons Gould Ballistic Research Laboratory 

(CSE) 

CSE

Giordano Robert Communication and

Electronics Research, 

Development and Engineering 

Center (CSE) 

GR, CST 

Goodman Samuel Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

Gow Edward Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

GR

Harju William Abrams PM Office (CSE) GR, CST 

Hasenbein Richard Frankford Arsenal/Armament

Research, Development and 

Engineering Center (CSE) 

CSE

*Havel Thomas Ballistic Research Laboratory 

(CSE) 

CSE

Havrilla Alan Abrams PM Office (CSE) CSE 

*Higgins Terry Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

Hollis Walter Frankford Arsenal (CSE) CSE

Hoogterp Frank Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

GR

*Horst Albert Ballistic Research Laboratory 

(CSE) 

GR, CST 

 49
Johnson Larry Ballistic Research Laboratory 

(CSE) 

GR, CST 

*Johnson Leroy General Motors (PSE) PSE 

Kuss Paul Ballistic Research Laboratory 

(CSE) 

CSE

Lane Jerry Tank-Automotive Command

(CSE) 

CSE

*Lehman Joseph Frankford Arsenal/Armament

Research, Development and 

Engineering Center (CSE) 

GR, CST 

Lett Phil Chrysler/General Dynamics

(PSE) 

PSR, CST 

May Ingo Ballistic Research Laboratory 

(CSE) 

GR, PSE 

McClellan Richard Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

McCormack Steve Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

*McVey Peter Abrams PM Office (AM) MR, PSE 

*Miller Clay Abrams PM Office (AM) MR, CTR 

Motzenbecker Peter Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

Nietubiez Charles Ballistic Research Laboratory 

(CSE) 

CSE

*Plostins Peter Ballistic Research Laboratory 

(CSE) 

CSE

Price Renata Armament Research,

Development and Engineering 

Center (CSE) 

GR, PSE 

*Raffa Charles Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

*Ratches James Night Vision Laboratory 

(CSE) 

CSE

*Rowe John Abrams PM Office (CSE) CSE 

Rowe Walter Ballistic Research Laboratory 

(CSE) 

CSE

Runyan John Ballistic Research Laboratory 

(CSE) 

CSE

Rusch Laurence Watervliet Arsenal (CSE) CSE

*Sarna Donald Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

GR, CST 

 50
Sciarretta Albert Armor Unit, U.S. Army (AM) MR, CST 

*Smith Irving Abrams PM Office (CSE) CSE 

Sorenson Brett Ballistic Research Laboratory 

(CSE) 

CSE

Stevens Randy Abrams PM Office (CSE) GR, CTR 

*Sweers Dennis Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

CSE

Travetsky Paul Night Vision Laboratory 

(CSE) 

GR, CST 

Underwood John Benet Laboratories (CSE) GR, CTR 

Vigilante Greg Watervliet Arsenal (CSE) CSE

Vitali Richard Ballistic Research Laboratory 

(CSE) 

GR, CST 

Watson Jerry Ballistic Research Laboratory 

(CSE) 

CSE

*Wheelock Wayne Tank Automotive Research, 

Development and Engineering 

Center (CSE) 

GR

*Wiss John Tank Automotive Research, 

Development and Engineering 

Center (AM) 

MR, ACD 

Wynbelt Walter Abrams PM Office (CSE) GR, CST 

Yeager Maurice Martin Marietta (PSE) CST

 51
Appendix B 

Critical Technology Event List 

Number CTE Report Section

1 120mm gun decision Main Gun 

2 Fracture mechanics application Main Gun 

3 Swage autofrettage process Main Gun 

4 Error budget Gun Accuracy 

5 Statistical models Gun Accuracy 

6 Gun tube straightening process Gun Accuracy 

7 Long-rod penetrators/120mm gun decision Penetrators 

8 Long-rod penetrator development Penetrators 

9 Long-rod penetrator modeling Penetrators 

10 Depleted uranium LRP decision Penetrators 

11 High rate forming DU process Penetrators 

12 Penetrator/target interaction analysis [Sidebar on Facilities]

13 Slipping rotating band Sabot 

14 Sabot tipping ring and scoop design Sabot 

15 Aluminum sabot technology Sabot 

16 Composite sabot technology Sabot 

17 Propellant modeling and analysis Propellants 

18 Propellant design and development Propellants 

19 Hull design and analysis Armor 

20 Hull joining technology Armor 

21 U.S/U.K armor technology exchanges Armor 

22 Special armor design Armor 

23 DU armor application Armor 

24 Ammunition compartment design Crew protection 

25 Less sensitive munitions Crew protection 

26 Ammunition sensitivity test rig Crew protection 

27 Combustible casings Crew protection 

28 Fire protection system Crew protection 

29 Nuclear, Biological and Chemical protection system Crew protection 

30 Predictive computer models for live-fire tests System Testing, Modeling 

and Analysis 

31 Robust model for live-fire tests System Testing, Modeling 

and Analysis 

32 Gas turbine engine decision Engine 

 52
33 Gas turbine engine development Engine 

34 Air filtration system Engine 

35 Hydromechanical transmission Transmission 

36 X1100 transmission requirements and decision Transmission 

37 X1100 transmission gears and brakes Transmission 

38 Improved suspension system Track and Suspension 

System 

39 Replaceable track pad Track and Suspension 

System 

40 Drive sprocket fix Track and Suspension 

System 

41 Vetronics digital architecture Vetronics 

42 Army Science Board concept C4ISR 

43 The Intervehicular Information System (IVIS) C4ISR 

44 Position/Navigation system C4ISR 

45 Intercom system C4ISR 

46 Force XXI Battle Command, Brigade and Below C4ISR 

47 Common module approach Thermal Imaging 

48 Models to predict Minimum Resolvable Temperature Thermal Imaging 

49 Commander's Independent Thermal Imaging System Thermal Imaging 

50 Digital fire-control system Fire-Control System and 

Related Sensors 

51 Laser rangefinder Fire-Control System and 

Related Sensors 

52 Eyesafe laser rangefinder Fire-Control System and 

Related Sensors 

53 Muzzle reference system Fire-Control System and 

Related Sensors 

54 Muzzle reference system fix Fire-Control System and 

Related Sensors 

55 Digital ballistic computer Fire-Control System and 

Related Sensors 

 53