GAO

United States General Accounting Office

Report to Congressional Requesters

March 1999 DEFENSE 

ACQUISITIONS

DOD Efforts to 

Develop Laser 

Weapons for Theater 

Defense

GAO/NSIAD-99-50

GAO United States

General Accounting Office

Washington, D.C. 20548 Letr

National Security and 

International Affairs Division Letr

B-279125 Letter

March 31, 1999

The Honorable Owen B. Pickett 

Ranking Minority Member

Subcommittee on Military Research and Development

Committee on Armed Services

House of Representatives

The Honorable John M. Spratt, Jr.

Ranking Minority Member

Committee on the Budget

House of Representatives

This report responds to your request that we conduct a review of Department of Defense 

(DOD) programs to develop laser weapons for missile defense. Specifically, you asked us to 

(1) identify what laser weapons are being considered for missile defense and the coordination 

among the program offices developing the systems, (2) determine the current status and cost 

of each system, and (3) identify the technical challenges each system faces as determined by 

DOD program managers and analysts and other laser system experts. The report recommends 

that the Secretary of Defense direct the Secretary of the Air Force to reconsider plans to 

exercise the option for the second ABL aircraft for the engineering and manufacturing 

development phase of the Airborne Laser program before flight testing of the Airborne Laser 

system developed during the program definition and risk reduction phase has demonstrated 

that the Airborne Laser concept is an achievable, effective combat system.

We are sending copies of this report to Senator Pete V. Domenici, Senator Daniel K. Inouye, 

Senator Carl Levin, ’’Senator Frank R. Lautenberg, Senator Joseph I. Lieberman, Senator Rick 

Santorum, Senator Ted Stevens, Senator John W. Warner, Representative Duncan L. Hunter, 

Representative John R. Kasich, Representative Jerry Lewis, Representative John P. Murtha, 

Representative David R. Obey, Representative Norman Sisisky, Representative Ike Skelton, 

Representative Floyd D. Spence, Representative Curt Weldon, and Representative C.W. Bill 

Young in their capacities as Chair or Ranking Minority Member of Senate and House 

Committees and Subcommittees. We are also sending copies of this report to the Honorable 

William Cohen, Secretary of Defense; the Honorable F. Whitten Peters, Acting Secretary of the 

Air Force; the Honorable Louis Caldera, Secretary of the Army; the Honorable Jacob Lew, 

Director, Office of Management and Budget; and Lieutenant General Lester L. Lyles, Director, 

Ballistic Missile Defense Organization. Copies will also be made available to others on request.
B-279125

Page 2 GAO/NSIAD-99-50 Defense Acquisitions

Please contact me at (202) 512-4841 if you or your staff have any questions 

concerning this report. Major contributors to this report are listed in 

appendix II.

Louis J. Rodrigues

Director, Defense Acquisitions Issues 
Page 3 GAO/NSIAD-99-50 Defense Acquisitions

Executive Summary

Purpose The Ranking Minority Member, House Committee on the Budget, and the 

Ranking Minority Member, Subcommittee on Military Research and 

Development, House Committee on Armed Services, asked GAO to review 

the Department of Defense’s (DOD) programs to develop laser weapons for 

missile defense to (1) identify the laser weapons being considered for 

missile defense and the coordination among the program offices 

developing the systems, (2) determine the current status and cost of each 

system, and (3) identify the technical challenges each system faces as 

determined by DOD program managers and analysts and other laser system 

experts.

Background DOD is developing a variety of weapon systems as part of its Theater 

Missile Defense program. The first generation of these weapons uses 

interceptor missiles to intercept and destroy enemy missiles in the latter 

stages of their flight. Included among these systems are the Patriot 

Advanced Capability-3, an improved version of the Patriot system that was 

used during the Gulf War; Navy Area Defense; Medium Extended Air 

Defense System; Theater High Altitude Air Defense; and Navy Theater Wide 

system.

In addition, DOD is developing ballistic missile defense systems that will 

use laser beams to destroy enemy missiles. These systems, as well as a 

system that is to be used to destroy short-range artillery rockets, are the 

focus of this report.

Results in Brief DOD is developing two laser weapons--the Airborne Laser (ABL) and the 

Space-Based Laser (SBL)--which U.S. forces intend to use to destroy enemy 

ballistic missiles. Additionally, in a joint effort with Israel, DOD is 

developing a ground-based laser weapon, the Tactical High Energy Laser 

(THEL), which Israel will use to defend its northern cities against 

short-range rockets. ABL is funded and managed by the Air Force, SBL is 

jointly funded by the Ballistic Missile Defense Organization and the Air 

Force and managed by the Air Force, and THEL is funded jointly with Israel 

and managed by the Army. The respective program offices are 

coordinating the development of these programs through various means of 

information sharing.

ABL, SBL, and THEL are in varying stages of development ranging from 

conceptual design studies to integration and testing of system components.
Executive Summary

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• The ABL program is in the program definition and risk reduction 

(PDRR) acquisition phase1

 and is scheduled for full operational 

capability in 2009, with a total of seven ABLs. This schedule reflects a

1-year delay from the original schedule. The Air Force attributes this 

slippage to a congressional funding cut and to an expanded test 

program. The Air Force estimates the life-cycle cost of the ABL to be 

about $11 billion.

• The SBL program is about a year into a $30-million study phase to define 

concepts for the design, development, and deployment of a proof of 

concept demonstrator. DOD estimates that it will cost about $3 billion 

to develop and deploy the demonstrator. The future of the SBL program 

is unknown at this time, pending the outcome of a DOD assessment of 

the program.

• The $131.5-million THEL Advanced Concept Technology Demonstration 

program is about 34 months into a 38-month program. System 

components have been built, but system testing has been delayed from 

December 1998 to July 1999 due to administrative and technical 

problems. The United States is contributing $106.8 million toward the 

program cost and Israel is contributing $24.7 million.

Laser experts agree that the ABL, SBL, and THEL face significant technical 

challenges. The ABL program has made progress in addressing some 

technical challenges, such as completing the collection of non-optical 

atmospheric turbulence data from the Korean and Middle East theaters. 

However, in commenting on a draft of this report, DOD officials stated that 

while the Air Force’s analyses of these data argue that the design 

specification established for atmospheric turbulence is generally accurate, 

DOD has yet to reach a final position on this issue. The technical 

complexity of the ABL program has caused some laser experts to conclude 

that the ABL planned flight test schedule is compressed and too dependent 

on the assumption that tests will be successful and therefore does not 

allow enough time and resources to deal with potential test failures and to 

prove the ABL concept. GAO believes that the Air Force should reconsider 

its plan to order a second ABL aircraft before flight tests demonstrate that 

the ABL system can shoot down enemy ballistic missiles.

1

This phase consists of steps necessary to verify preliminary design and engineering, build prototypes, 

accomplish necessary planning, and fully analyze trade-off proposals. The objective is to validate the 

choice of alternatives and to provide the basis for determining whether to proceed into the next phase 

(engineering and manufacturing development) of the acquisition process.
Executive Summary

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SBL program management has characterized the SBL demonstrator as the 

most complex spacecraft the United States has ever attempted to build. If 

DOD ultimately decides to continue the program, the size and weight 

limitations dictated by current and future launch capabilities will force the 

program to push the state of the art in areas such as laser efficiency, laser 

power, and deployable optics.

THEL's components have been produced. However, initial testing of the 

laser has identified problems with the operation of the chemical flow 

control valves and with the low-power laser that is to be used in tracking 

short-range rockets the system is being designed to defeat.

Principal Findings

DOD Developing Three

Defensive Laser Weapons

The ABL is expected to be DOD's first system to intercept and destroy 

enemy missiles in their boost phase several hundred kilometers away. The 

program involves placing multimegawatt lasers, beam control systems, and 

related equipment, in a fleet of seven Boeing 747-400 freighter aircraft.

The SBL is to be DOD's first space-based laser weapon and is designed to 

provide a continuous global boost phase intercept capability for both 

theater and national missile defense. Proposed concepts call for placing 

multimegawatt chemical lasers, beam control systems, and related 

components on a constellation of 20 to 35 satellites. Each SBL is to be 

capable of destroying about 100 missiles and is to have a range of about 

4,300 kilometers.

The THEL is a ground-based weapon that is being designed to destroy 

Katyusha2 and other short-range rockets. It is to detect an incoming rocket, 

track the rocket's path, and hold a concentrated laser beam on the rocket's 

warhead until the beam's heat causes the warhead to detonate, destroying 

the rocket. THEL is not designed to be powerful and mobile enough to 

meet U.S. needs.

2

According to THEL program officials, the Katyusha rocket has a range of 8 to 24 kilometers, with a 

flight time of 20 to 80 seconds. Its boost phase is about 1.5 seconds.
Executive Summary

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Coordination Among the 

Programs

The directors for the three laser development programs are coordinating 

their efforts by meeting periodically to share information on technology 

and development issues. In addition, some of the same contractors and 

contractor personnel are involved in all three programs, thereby increasing 

program coordination. Further, all three programs have benefited from 

work performed by the Air Force Research Laboratory.

Status and Cost of the

Laser Weapon Programs

The ABL program is currently in the PDRR acquisition phase. In November 

1996, the Air Force awarded the PDRR contract to the team of Boeing, 

TRW, and Lockheed Martin. Under this contract, Boeing is to produce and 

modify a 747-400 freighter aircraft and integrate the laser and beam control 

system with the aircraft; TRW is to develop the chemical oxygen iodine 

laser and ground support systems; and Lockheed Martin is to develop the 

beam control system. One prototype ABL is to be produced and used in 

2003 in attempts to shoot down missiles in their boost phase. This 

schedule reflects a 1-year slip in the original PDRR schedule. According to 

the program office, this slip is due to a $25-million reduction made by 

Congress in the fiscal year 1999 appropriation for the ABL and to an 

expanded test program. If the 2003 demonstration is successful, the 

program is to move into the engineering and manufacturing development 

phase. The Air Force estimates the life-cycle cost of the ABL to be about 

$11 billion, including $1.6 billion for the PDRR phase, $1.1 billion for the 

engineering and manufacturing development (EMD) phase, $3.6 billion for 

the production phase, and $4.6 billion for 20 years of operations and 

support.

The SBL program office awarded two 6-month, $10 million contracts in 

February 1998 to Lockheed Martin and TRW to obtain information needed 

to develop an acquisition plan. It planned to award another contract in 

August 1998 for the design, development, and deployment of the 

demonstrator. However, that contract was not awarded because, in August 

1998, the Under Secretary of Defense for Acquisition and Technology 

directed the Air Force to restructure the SBL strategy, including 

considering other alternatives to the SBL. The Air Force's restructured 

strategy shows that a demonstrator would not be launched until the 2010 to 

2012 time frame, due to the immaturity of the required technology and the 

projected program funding. The restructured strategy has not received 

final approval and is not consistent with Congress' desire to launch the SBL 

readiness demonstrator in the 2006 to 2008 time frame. At the time of 

GAO's review, Ballistic Missile Defense Organization (BMDO) officials did 

not know when or if the proposed restructured acquisition strategy will be 
Executive Summary

Page 7 GAO/NSIAD-99-50 Defense Acquisitions

approved and ultimately submitted to Congress. If the SBL is ultimately 

selected to proceed, DOD estimates that a fully operational system would 

not be deployed until after 2020.

The $131.5 million THEL system, which is being developed by TRW and 

Israel, is scheduled to be the first of the three systems fielded, albeit not for 

U.S. use. The program is about 34 months into a 38-month program. The 

United States and Israel are contributing $106.8 million and $24.7 million 

toward the program cost, respectively. All system components have been 

built and are in varying stages of testing and integration. Testing at White 

Sands Missile Range against Katyusha rockets, originally scheduled for 

December 1998, is now scheduled for July 1999, due to administrative 

issues and technical problems with the laser and tracking system.

Technical Challenges Face 

Each System

While individual components of the proposed systems have been tested 

under laboratory conditions and the program offices have conducted 

modeling and computer simulations, none of the systems has been fully 

integrated and tested as a complete weapon system. Until this is 

accomplished, it is not possible to predict with any degree of certainty the 

probability that these laser programs will evolve into viable defense 

systems.

The ABL program has made progress in addressing some technical 

challenges. However, other challenges remain as do concerns about some 

Air Force statements of program successes. Specifically, Air Force 

statements that the flight-weighted laser module3 exceeded power output 

requirements are questionable because a major component of the module 

did not meet ABL design specifications. Further, the Air Force states that it 

met the beam quality requirement for the laser module; however, it has not 

yet measured the quality of an actual laser beam generated by the module. 

Instead, during the initial tests, beam quality was estimated using computer 

models and measurements of the chemical flows within the laser. The 

complexity of the ABL system indicates that initiating the hot fire flight 

testing only 4 months prior to the 2003 theater ballistic missile shoot down 

tests is not adequate. In that regard, the Air Force Scientific Advisory 

Board stated that, "past experience with high power laser systems and 

large beam directors suggests that new and difficult problems will surface 

in that [flight test] phase, and many flights and targets will be needed to 

3

A laser module that is of the size and weight that can be carried by the ABL aircraft.
Executive Summary

Page 8 GAO/NSIAD-99-50 Defense Acquisitions

sort them out." Given these complexities, the Air Force's plan to order a 

second ABL aircraft, about 1 year before the weapon system developed 

during the PDRR phase, attempts to demonstrate that the proposed ABL 

system can shoot down an enemy theater ballistic missile, should be 

reconsidered.

The high level of technical challenges facing the SBL program is 

exemplified by a statement a senior SBL program official made to GAO that 

there was a 50-percent chance of being able to build and deploy the SBL 

concept demonstrator by 2008 (one of the then-current deployment goals). 

According to this official, the SBL demonstrator would be the most 

complex spacecraft the United States has ever built. The major reasons for 

this technical complexity are the weight and size constraints dictated by 

the limited payload capabilities of current and future launch vehicles. 

These constraints will force the program to push the state of the art in 

areas such as laser efficiency, laser power, and deployable optics.

A 7-month schedule delay in the THEL program illustrates the technical 

challenges the program must overcome. Testing against Katyusha rockets 

at White Sands Missile Range, New Mexico, was to occur in December 

1998, but has now slipped until July 1999 due to administrative issues 

associated with contract initiation and technical problems with the laser 

and tracking system. The initial tests of the laser revealed leaks in the 

specialized valves that control the flow of chemicals through the laser. 

These leaks must be corrected because they would detract from the 

performance of the laser. In addition, testing of the pointer tracker system 

disclosed a problem with the low-power laser that is to be used in tracking 

incoming short-range rockets.

Recommendation Regarding the ABL program, GAO recommends that the Secretary of 

Defense direct the Secretary of the Air Force to reconsider exercising the 

option for the second ABL aircraft for the EMD phase of the program until 

flight testing of the ABL system developed during the PDRR phase has 

demonstrated that the ABL concept is an achievable, effective combat 

system.

Agency Comments and 

GAO’s Evaluation

In a draft of this report, GAO recommended that the Secretary of Defense 

direct the Secretary of the Air Force to provide DOD an assessment of the 

need to expand the ABL flight test program. In commenting on that draft 
Executive Summary

Page 9 GAO/NSIAD-99-50 Defense Acquisitions

report, DOD partially concurred with GAO’s recommendation and stated 

that its ongoing assessment of the ABL program by an Independent 

Assessment Team (IAT) would constitute an appropriate assessment of the 

flight test program.4

 

Subsequent to DOD’s comments on GAO’s draft report, DOD completed its 

assessment of the ABL program and reported the results to Congress in 

March 1999. In its report, DOD noted the IAT’s agreement with Air Force 

plans to restructure the ABL program to expand testing and risk reduction 

activities before starting modifications to the PDRR aircraft (the first 

aircraft). DOD concurred with the IAT’s recommendation for more testing 

of the PDRR aircraft before Milestone II, which governs entry into 

engineering and manufacturing development. DOD stated that it will 

review the Air Force’s proposed restructured program and set a new 

Acquisition Program Baseline in the spring of 1999. During the 

restructuring and rebaselining effort, DOD stated that, among other things, 

it will revise the exit criteria for Milestone II to require more testing against 

threat-representative targets. 

DOD stated that it expects that adding flight tests to the program before the 

start of EMD will increase near-term costs and might delay ABL’s 

achievement of an initial operational capability. However, according to 

DOD, the added tests will ensure that the expenditures required for ABL’s 

EMD phase are justified.

GAO agrees with DOD’s assessment and future plans for the ABL program. 

Therefore, GAO deleted from its final report the recommendation for an 

assessment of the ABL flight test program.

Based on DOD’s comments on GAO’s draft report that DOD would not 

necessarily incur unnecessary costs by proceeding with the purchase of a 

second ABL aircraft, GAO revised its recommendation to reflect the need 

for DOD to reconsider its planned purchase in light of the IAT’s findings 

and GAO’s report.

GAO recognizes that delaying the procurement of the aircraft for the EMD 

portion of the program until after the ABL demonstrates it can shoot down 

target missiles might require a change in the scheduled initial operational 

4

This assessment was required by the Strom Thurmond National Defense Authorization Act for Fiscal 

Year 1999.
Executive Summary

Page 10 GAO/NSIAD-99-50 Defense Acquisitions

capability. However, such a slip would ensure that the procurement of the 

EMD aircraft would then be based on the additional knowledge gained in 

the shoot down demonstrations that the ABL design is feasible. GAO’s 

approach is consistent with DOD’s March 1999 report to Congress on the 

ABL program wherein it accepted a potential delay in the ABL’s initial 

operational capability in favor of obtaining additional data through 

increased flight tests. GAO’s approach is also appropriate in view of the 

discussion in DOD’s March 1999 report on the impact of turbulence on the 

ABL design specification. DOD stated that optical turbulence in excess of 

the design specification along the slant path between the ABL and its target 

can reduce ABL’s maximum lethal range and increase required dwell times, 

even at lesser ranges. It said that some analyses of atmospheric turbulence 

data collected in theaters of interest to date suggest that turbulence levels 

well above assumed ABL design levels might occur more often than 

expected at the time the design levels were set. According to DOD, there 

are currently no clear methods for predicting the actual turbulence level 

along a slant path to a particular threat location at a given point in time. 

Thus, according to DOD, beyond trial and error, it is not clear how a correct 

decision can be made on whether a particular target can be successfully 

engaged when launched near ABL’s maximum lethal range. The Air Force 

is analyzing turbulence data and investigating tactical decision aids for the 

system to address this issue.

DOD’s comments are reprinted in appendix I. DOD also provided separate 

technical comments that we have incorporated in this report where 

appropriate.
Executive Summary

Page 11 GAO/NSIAD-99-50 Defense Acquisitions
Page 12 GAO/NSIAD-99-50 Defense Acquisitions

Contents

Executive Summary 3

Chapter 1

Introduction

14

Objectives, Scope, and Methodology 16

Chapter 2

DOD Developing Three 

Laser Weapons and 

Coordinating Its 

Development Efforts in 

Various Ways

17

Developing Three Defensive Laser Weapons 17

Coordination and Technology Sharing 21

Chapter 3

Airborne Laser: Status, 

Cost, and Technical 

Challenges

23

Status and Cost of the ABL Program 23

ABL Program Progress 24

Technical Challenges Remain 25

Planned Ordering of the EMD Aircraft

May Be Premature 29

Conclusions 29

Recommendation 30

Agency Comments and Our Evaluation 30

Chapter 4

Space-Based Laser: 

Status, Cost, and 

Technical Challenges

32

Status, Cost, and Technical Challenges 32

Conclusions 34

Chapter 5

Tactical High Energy 

Laser: Status, Cost, and 

Technical Challenges

35

Status and Cost of the THEL Program 35

Conclusions 37
Contents

Page 13 GAO/NSIAD-99-50 Defense Acquisitions

Appendixes Appendix I: Comments From the Department of Defense 40

Appendix II: Major Contributors to This Report 44

Tables Table 1.1: Examples of DOD Laser Development Efforts 14

Figures Figure 2.1: ABL Missile Engagement 18

Figure 2.2: Notional SBL Missile Engagement 19

Figure 2.3: THEL Rocket Engagement 21

Abbreviations

ABL Airborne Laser

AFRL Air Force Research Laboratory

ATP Authority to Proceed

BMDO Ballistic Missile Defense Organization

DOD Department of Defense

EMD engineering and manufacturing development

HELSTF High-Energy Laser Systems Test Facility

PDRR program definition and risk reduction

SBL Space-Based Laser

SBLRD Space-Based Laser Readiness Demonstrator

SMDC Space and Missile Defense Command

THEL Tactical High-Energy Laser
Page 14 GAO/NSIAD-99-50 Defense Acquisitions

Chapter 1

Introduction Chapte1r

The Department of Defense (DOD) and Congress have become increasingly 

concerned that U.S. and allied troops abroad may be attacked by chemical, 

biological, or nuclear weapons delivered by ballistic missiles. Operation 

Desert Storm demonstrated that the U.S. military and other allied forces 

have limited capability against theater ballistic missiles. In fact, U.S. 

defensive capability is limited to weapons that defend against missiles 

nearing the end of their flight, such as the Patriot.1

 Consequently, 

developing weapon systems to defeat these threats is DOD’s top priority in 

its overall ballistic missile defense program.

DOD has been working with laser technology for a long time. The 

following table shows some of the laser development efforts that DOD has 

undertaken. To date, none of these efforts has resulted in an operational 

laser weapon system.

Table 1.1: Examples of DOD Laser Development Efforts

1

The Patriot system was initially deployed in 1985 as an anti-aircraft weapon and modified in the late 

1980s to defend against ballistic missiles as well. It has a range of about 40 miles.

Development effort Purpose Inception date

Tri-Service Laser Program Develop carbon dioxide gas 

dynamic laser 1968

Navy-Advanced Research 

Projects Agency Chemical 

Laser Program

Develop high-energy 

chemical laser

1971

Airborne Laser Laboratory Demonstrate the feasibility 

of using a high-energy laser 

in an airborne environment 1972

Mid-Infrared Advanced 

Chemical Laser

Develop and integrate a 

ground-based high-energy 

chemical laser with a beam 

control system 1977

Space-Based Laser 

Program

Develop space-based highenergy chemical laser 

weapon system 1977

Ground-Based Laser (free 

electron) 

Develop high-energy free 

electron laser weapon 

system 1979

Ground-Based Laser 

(Excimer)

Develop high-energy 

excimer laser weapon 

system 1979
Chapter 1

Introduction

Page 15 GAO/NSIAD-99-50 Defense Acquisitions

Currently, DOD is developing a variety of weapon systems as part of its 

Theater Missile Defense program to counter the potential threats posed by 

ballistic missiles. The first generation of these weapon systems uses 

interceptor missiles to intercept and destroy enemy missiles in the latter 

stages of the missiles' flight. Included among these systems are the Patriot 

Advanced Capability-3, an improved version of the Patriot system that was 

used during the Gulf War; Navy Area Defense; Medium Extended Air 

Defense System; Theater High Altitude Air Defense; and Navy Theater 

Wide.

In addition, DOD is developing ballistic missile defense systems that will 

use laser beams to destroy enemy missiles. DOD plans to spend billions of 

dollars to develop these laser weapons and place them in the air (Airborne 

Laser)2 and in space (Space-Based Laser). In addition, DOD is developing a 

ground-based laser (Tactical High-Energy Laser) that is to be used to 

destroy short-range artillery rockets.

Congress has generally endorsed DOD’s efforts to develop and produce 

these laser weapon systems. Its desire to have these systems developed, 

produced, and deployed as soon as possible was heightened by a July 1998 

report by the Commission to Assess the Ballistic Missile Threat to the 

United States.3

 The Commission concluded, among other things, that 

concerted efforts by a number of overtly or potentially hostile nations to 

acquire ballistic missiles with biological or nuclear warheads pose a 

growing threat to the United States, its deployed forces, and its friends and 

allies.

While endorsing, and in some instances suggesting that DOD’s efforts to 

develop laser weapon systems to defeat ballistic missiles be accelerated, 

Congress has also expressed concern over the cost and risk associated 

with developing and demonstrating the maturity of the technologies 

required to develop such missile defense capabilities.

2See Theater Missile Defense: Significant Technical Challenges Face the Airborne Laser Program

(GAO/NSIAD-98-37, Oct. 23, 1997) for a discussion of this program.

3

The Commission was established pursuant to P.L. 104-201, the National Defense Authorization Act for 

Fiscal Year 1997.
Chapter 1

Introduction

Page 16 GAO/NSIAD-99-50 Defense Acquisitions

Objectives, Scope, and 

Methodology

The Ranking Minority Member, Committee on the Budget, and the Ranking 

Minority Member, Subcommittee on Military Research and Development, 

Committee on Armed Services, House of Representatives, asked us to 

review DOD's programs to develop laser weapons for missile defense to

• identify what laser weapons are being considered for missile defense 

and the coordination among the program offices developing the 

systems,

• determine the current status and cost of each system, and

• identify the technical challenges each system faces as determined by 

DOD program managers and analysts and other laser system experts.

To identify the laser weapons being considered for missile defense and 

what coordination exists among the programs developing the systems, we 

reviewed DOD budget and Airborne Laser (ABL), Space-Based Laser (SBL), 

and Tactical High-Energy Laser (THEL) program office documents. We 

also met with officials of the Office of the Secretary of Defense; the 

Ballistic Missile Defense Organization, the ABL program office; the Air 

Force Space and Missile Systems Center; and the Army Space and Missile 

Defense Command.

To determine the current status and cost of each system, we reviewed and 

analyzed DOD; Air Force; Army; ABL, SBL, and THEL program offices; and 

contractor documents regarding the status and cost of the DOD laser 

weapon programs. We discussed the laser programs with officials of the 

Ballistic Missile Defense Organization; the ABL program office; the Air 

Force Space and Missile Systems Center; the Army Space and Missile 

Defense Command; TRW, Inc.; and Lockheed Martin Corporation.

To determine the technical challenges each system faces, we reviewed and 

analyzed documents and studies from DOD; Air Force; Army; ABL, SBL, 

and THEL program offices; and contractors. We discussed the technical 

aspects of the laser programs with officials of the Office of the Secretary of 

Defense (Operational Test and Evaluation); the Ballistic Missile Defense 

Organization; the Air Force Air Combat Command; the Air Force 

Operational Test and Evaluation Center; the ABL program office; the Air 

Force Scientific Advisory Board; the Air Force Space and Missile Systems 

Center; the Army Space and Missile Defense Command; TRW, Inc.; 

Lockheed Martin Corporation; and Lawrence Livermore National 

Laboratory.
Chapter 1

Introduction

Page 17 GAO/NSIAD-99-50 Defense Acquisitions

We conducted our review from November 1997 to December 1998 in 

accordance with generally accepted government auditing standards.
Page 17 GAO/NSIAD-99-50 Defense Acquistions

Chapter 2

DOD Developing Three Laser Weapons and 

Coordinating Its Development Efforts in 

Various Ways Chapte2r

DOD is developing two laser weapons, ABL and SBL, that are to be used by 

U.S. forces to destroy enemy ballistic missiles. Additionally, in a joint effort 

with Israel, DOD is developing the THEL, which is to be used by Israel to 

defend against short-range rockets.

All three programs have benefited from work performed by the Air Force 

Research Laboratory on lasers and associated systems. In addition, the 

program directors for these three programs are coordinating their efforts 

by meeting periodically to discuss and share information on technology 

and program development issues. Moreover, some of the same contractors 

and contractor personnel are involved in all three programs, thereby 

increasing program coordination.

Developing Three

Defensive Laser 

Weapons

The ABL is to be carried by a 747 aircraft, and the SBL by a constellation of 

satellites. Both of these weapons are to be used by U.S. forces to destroy 

ballistic missiles while the missiles are still in the early stage of their flight 

(boost phase). The THEL is a ground-based laser weapon Israel is to use to 

defend its northern border cities against Russian-made Katyusha rocket1

attacks in the final stages of the rockets' flight.

ABL Program The ABL, funded and managed by the Air Force, is planned to be the first 

system with the ability to detect and destroy enemy missiles in their boost 

phase several hundred kilometers away. It is a complex laser weapon 

system that is being designed to detect an enemy missile shortly after its 

launch, track the missile’s path, and hold a concentrated laser beam on the 

missile until the beam’s heat causes the pressurized missile casing to crack, 

in turn causing the missile to explode and the warhead to fall to earth well 

short of its intended target. The program involves placing a multimegawatt 

laser, beam control system, and related equipment in a Boeing 747-400 

freighter aircraft. One prototype ABL is to be produced and tested in 2003 

in attempts to shoot down missiles in their boost phase. If this 

demonstration is successful, the program is scheduled to move into the 

engineering and manufacturing development phase in 2004. Figure 2.1 

shows the ABL concept.

1

According to THEL program officials, the Katyusha rocket has a range of 8 to 24 kilometers, with a 

flight time of 20 to 80 seconds. Its boost phase is about 1.5 seconds.
Chapter 2

DOD Developing Three Laser Weapons and 

Coordinating Its Development Efforts in 

Various Ways

Page 18 GAO/NSIAD-99-50 Defense Acquistions

Figure 2.1: ABL Missile Engagement

The ABL is expected to operate from a central base in the United States and 

be available to be deployed worldwide. Ultimately, with a seven-aircraft 

fleet, five aircraft are expected to be available for operational duty at any 

given time. The other two aircraft are expected to be undergoing 

modifications or undergoing maintenance or repair. When the ABLs are 

deployed, two aircraft are to fly in figure-eight patterns above the clouds at 

about 40,000 feet. Through in-flight refueling and rotation of aircraft, two 

ABLs will always be on patrol, thus ensuring 24-hour coverage of potential 

100,000

80,000

60,000

40,000

20,000

0

Cloud Tops

Altitude (feet)

Missile 

destroyed

Laser Dwell

Destruction

Tracking

Detection

Booster burnout

747
Chapter 2

DOD Developing Three Laser Weapons and 

Coordinating Its Development Efforts in 

Various Ways

Page 19 GAO/NSIAD-99-50 Defense Acquistions

missile launch sites within the theater of operations. Each ABL is to be 

capable of destroying about 20 missiles before chemicals needed to 

generate the laser beam need to be replenished. At that point, the aircraft 

will have to land to refuel the laser.

SBL Program The SBL, jointly funded by the Ballistic Missile Defense Organization 

(BMDO) and the Air Force and managed by the Air Force, is to be capable 

of detecting a missile in its boost phase, tracking the missile’s path, and 

holding a concentrated laser beam on the missile until the beam’s heat 

causes the missile to be destroyed. The SBL program involves integrating a 

multimegawatt laser, beam control system, and related equipment on a 

space platform and launching it into low earth orbit. Air Force estimates 

show that a full SBL system would not be deployed until after 2020. 

Figure 2.2 shows a notional SBL engagement.

Figure 2.2: Notional SBL Missile Engagement

DOD is developing the SBL to provide a continuous global boost phase 

intercept capability for both theater and national missile defense. The 

Booster Destruct

Laser Energy On Booster

Identify and Track Target

Detect Target

Target
Chapter 2

DOD Developing Three Laser Weapons and 

Coordinating Its Development Efforts in 

Various Ways

Page 20 GAO/NSIAD-99-50 Defense Acquistions

notional concept involves having a constellation of 20 to 35 SBLs. Each 

SBL is to be capable of destroying about 100 missiles and is to have a range 

of about 4,300 kilometers.

THEL Program The THEL, funded jointly with Israel and managed by the U.S. Army, is a 

ground-based laser weapon that is to be used to destroy short-range 

rockets toward the end of their flights. THEL is to accomplish this by 

detecting an incoming rocket shortly after it has been launched, tracking 

the rocket's path, and holding a concentrated laser beam on the rocket's 

warhead until the beam's heat causes the warhead to detonate, destroying 

the rocket. The THEL program involves designing and building a 

multi-hundred kilowatt chemical laser, a beam control system, a fuel supply 

system, a laser exhaust system, and other equipment to fit into separate, 

transportable containers, sized so that each container can be transported 

by a large truck. The transportable containers are to be placed on concrete 

pads at deployment sites. Once deployed, the THEL components in each 

separate container are to be integrated. All THEL components have been 

produced and are scheduled to be integrated and tested at White Sands 

Missile Range, New Mexico, in July 1999. Figure 2.3 shows the THEL 

concept.
Chapter 2

DOD Developing Three Laser Weapons and 

Coordinating Its Development Efforts in 

Various Ways

Page 21 GAO/NSIAD-99-50 Defense Acquistions

Figure 2.3: THEL Rocket Engagement

DOD is developing the THEL, in a joint effort with Israel, to be used by 

Israel to defend against Russian-made Katyusha rockets and other shortrange rockets that have been used by terrorists to attack cities in northern 

Israel. The number of rockets THEL is capable of destroying is limited only 

by the amount of laser fuel stored at the deployment site.

Although THEL is a transportable system that can be moved by large 

trucks, it is not a mobile system, in the sense that the integrated system 

cannot move under its own power. Because of this limitation, the United 

States has no use for THEL as it is currently designed. See chapter 5 for 

additional discussion of the U.S. need for a mobile THEL-type system.

Coordination and 

Technology Sharing 

The three laser weapon development programs have coordinated their 

efforts by holding periodic program director conferences to share 

information. In addition, some of the same contractors and contractor 

personnel are involved in all three programs and all three programs have 

Detect

Target

Track

Target Beam on Target

THEL Fire Unit

Target Kill

Defended Zone

THEL Radar Unit
Chapter 2

DOD Developing Three Laser Weapons and 

Coordinating Its Development Efforts in 

Various Ways

Page 22 GAO/NSIAD-99-50 Defense Acquistions

benefited from work performed by the Air Force Research Laboratory on 

lasers and associated systems.

According to the program directors of the ABL, SBL, and THEL, they have 

conducted periodic conferences and frequent phone conversations to 

discuss and share information on technology and program development 

issues. They told us that technology developed under one program is 

shared where appropriate by all programs, thereby reducing duplication. 

For example, weight reduction techniques developed under the SBL 

program are to be used on the ABL and THEL programs.

TRW is a subcontractor for the ABL and SBL programs and the prime 

contractor for the THEL program and is developing the lasers for all three 

programs. ABL program officials told us that some of the same TRW 

personnel work on all three programs, thus transferring and sharing their 

laser technology knowledge between the programs. In another case, the 

same contractor is to produce the deformable mirrors2 used in the ABL and 

SBL programs.

All three programs have benefited from the research carried out by the Air 

Force Research Laboratory (AFRL). For example, all programs plan to use 

AFRL-developed optical coatings for beam control and laser optical 

systems. With these specialized coatings, optics absorb little energy from a 

high energy laser beam, and heavy, vibration-inducing cooling systems are 

not needed. AFRL officials have also participated in the three programs in 

various ways, which enhances information sharing. For example, an AFRL 

official participating in the ABL program is also acting as a THEL principal 

on-site government representative.

2

A deformable mirror is a flexible reflective surface mounted to an array of actuators, or pistons, that 

can rapidly (up to 1,000 times per second) alter the shape of the mirror. In effect, the mirror's shape is 

altered to predistort an outgoing laser beam, which is then refocused by the turbulence through which 

the beam travels on its way to the target.
Page 23 GAO/NSIAD-99-50 Defense Acquisitions

Chapter 3

Airborne Laser: Status, Cost, and Technical 

Challenges Chapte3r

The ABL program is currently in the program definition and risk reduction 

(PDRR) acquisition phase.1

 Initial operational capability of three ABLs is 

scheduled for 2007 and full operational capability of seven ABLs is 

scheduled for 2009. This schedule reflects a program slip of about 1 year. 

The Air Force estimates the life-cycle cost of the ABL at about $11 billion.

The ABL program has made progress in addressing some technical 

challenges, such as atmospheric turbulence that we and others have 

reported on in the past. However, challenges remain because the 

components of the system are in various stages of development and have 

yet to be produced in their final configurations, tested, and integrated into 

an operational weapon system. Because of the complexity of this 

integration, some laser experts both inside and outside of DOD have noted 

that the planned flight testing schedule for the program should be 

expanded. We believe that the technical complexity of the ABL and related 

integration issues also raises questions about whether the Air Force's 

planned ordering of a second aircraft, for modification during the 

engineering and manufacturing development (EMD) phase of the program, 

is premature.

Status and Cost of the 

ABL Program

In November 1996, the Air Force awarded a 77-month PDRR contract to the 

contractor team of Boeing, TRW, and Lockheed Martin. Under the 

contract, Boeing is to produce and modify a 747-400 freighter aircraft and 

integrate the laser and beam control system with the aircraft; TRW is to 

develop the laser and ground support systems; and Lockheed Martin is to 

develop the beam control system. The PDRR phase includes two interim 

milestones--Authority to Proceed 1 (ATP-1), originally scheduled for June 

1998, and ATP-2, scheduled for August 2002. The ABL passed ATP-1 in 

September 1998, 3 months late because the flight-weighted laser module 

had problems producing the required power level.

The PDRR phase is scheduled to culminate with attempts, in 2003, by the 

PDRR ABL aircraft to destroy a boosting theater ballistic missile. If these 

demonstrations are successful, the program is scheduled to move into the 

engineering and manufacturing development phase in 2004. Initial 

1

This phase consists of steps necessary to verify preliminary design and engineering, build prototypes, 

accomplish necessary planning, and fully analyze trade-off proposals. The objective is to validate the 

choice of alternatives and to provide the basis for determining whether to proceed into the next phase 

(engineering and manufacturing development) of the acquisition process.
Chapter 3

Airborne Laser: Status, Cost, and Technical 

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Page 24 GAO/NSIAD-99-50 Defense Acquisitions

operational capability of three ABLs is scheduled for 2007; full operational 

capability of seven ABLs is scheduled for 2009. This schedule reflects a 

1-year slip in the original PDRR schedule. According to the program office, 

the revision to the schedule is due to a $25-million reduction Congress 

made in the fiscal year 1999 appropriation for the ABL and to an expanded 

test program. The Air Force estimates the life-cycle cost of the ABL to be 

about $11 billion, including $1.6 billion for the PDRR phase, $1.1 billion for 

the EMD phase, $3.6 billion for the production phase, and $4.6 billion for 

20 years of operations and support.

ABL Program Progress We reported on the ABL program in October 1997. At that time, the 

immediate area of concern that we and others reported was whether the 

program had adequately assessed the adverse effects of atmospheric 

turbulence on the ABL's operational effectiveness.2

 We reported that the 

Air Force did not have all of the data needed to fully understand the effect 

that atmospheric turbulence would have on the operation of the ABL and 

that the Air Force had not determined whether non-optical turbulence 

measurements could be correlated to optical turbulence measurements.3

 

We reported that the Air Force had not shown that it could accurately 

predict the levels of turbulence the ABL will actually encounter; neither 

had it shown that the ABL's technical requirement regarding turbulence 

was appropriate. Consequently, we concluded that it was not yet known 

whether the ABL would be able to operate effectively in its operational 

environment. In addition, we reported that the Air Force planned to only 

take additional non-optical turbulence measurements to predict the 

severity of the optical turbulence the ABL would encounter without first 

determining whether the two measurement types could be correlated.

The Air Force has now completed collecting non-optical atmospheric 

turbulence data from the Korean and Middle East theaters. In commenting 

on a draft of this report, DOD stated that, while the Air Force's analyses of 

2The type of turbulence that the ABL will encounter is referred to as optical turbulence. It is caused by 

temperature variations in the atmosphere. These variations distort and reduce the intensity of the laser 

beam. Unless these turbulence effects are compensated for, they decrease the laser beam's effective 

range.

3

Optical turbulence measurements are taken by instruments that directly measure distortions in light 

that has traveled from a point source through the atmosphere to the measuring instrument. This can be 

accomplished by transmitting laser beams from one aircraft to instruments on-board another aircraft at 

various altitudes and distances, or by focusing on a point source of light, such as a star. Non-optical 

turbulence measurements are taken by radar or by temperature probes mounted on balloons or on an 

aircraft's exterior.
Chapter 3

Airborne Laser: Status, Cost, and Technical 

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Page 25 GAO/NSIAD-99-50 Defense Acquisitions

these data argue that the design specification established for atmospheric 

turbulence is generally accurate, the DOD has yet to reach a final position 

on this issue. DOD stated further that it is still examining the design 

specification for atmospheric turbulence. According to DOD, the Air Force 

plans to collect and characterize additional data to further validate its 

design assumptions. DOD also stated that uncertainties remain concerning 

the ability to use non-optical turbulence measurements under all 

conditions to predict operational performance for the ABL. It said that it 

was considering what additional measurements and analysis are needed to 

resolve these uncertainties.

The Air Force has also been able to establish that the correlation between 

non-optical and optical data is adequate for the purposes of estimating ABL 

performance using non-optical data at this stage of the program. However, 

according to DOD officials, there are instances where optical and nonoptical data disagree and the causes of these differences are not 

understood. Consequently, the Air Force is continuing to collect and 

analyze data to further validate its turbulence design assumptions.

Technical Challenges 

Remain

While the ABL program has made progress in addressing technical 

challenges relating to atmospheric turbulence, other challenges remain. 

Developing a laser module that is of the size and weight that can be carried 

by the ABL aircraft (referred to as a flight-weighted laser module), and 

integrating the laser, beam control system, and related equipment into an 

aircraft, are two examples of these challenges.

Flight-Weighted Laser

Module Challenges

The technical challenge inherent in the ABL program is exemplified by 

problems experienced in developing the high-energy laser. The Air Force 

must build the laser to be able to contend with size and weight restrictions, 

motion and vibrations, and other factors unique to an aircraft environment, 

yet be powerful enough to sustain a killing force over a range of hundreds 

of kilometers. It is also to be constructed in a configuration that links 

modules together to produce a single high-energy beam. The laser being 

developed for the PDRR phase will have six modules. The laser for the 

EMD phase will have 14 modules. When we issued our report on the ABL 

in 1997, the program had constructed and tested a developmental laser 

module. Although that developmental module exceeded its energy output 

requirements, it was too heavy and large to meet integration requirements. 

It would have to be reduced in width by about one-third and reduced in 

weight by over one-half. To accomplish this, many components of the 
Chapter 3

Airborne Laser: Status, Cost, and Technical 

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Page 26 GAO/NSIAD-99-50 Defense Acquisitions

module would have to be reconfigured and built of advanced materials, 

such as composites.

As previously discussed, the PDRR phase of the ABL program includes two 

milestone decision points--referred to as ATP-1 and ATP-2. To pass ATP-1, 

the Air Force had to "demonstrate a single laser module at full power with 

all critical components flight-weighted and show performance (power, 

beam quality, chemical efficiency, thermal management) is scaleable/

traceable to the EMD design through analysis." During testing of the

flight-weighted laser module in connection with the scheduled June 1998 

ATP-1 decision point, the module failed to meet its power output 

requirement. Because of this failure, the program provisionally passed 

ATP-1. 

The program fully passed ATP-1 when, 3 months later, the laser module 

exceeded its power output requirement by 10 percent. However, the power 

output was achieved using a flight-weighted laser module that was not 

representative of the laser modules that will be used in an operational ABL 

weapon system. Specifically, the flight-weighted laser module used for 

testing in connection with ATP-1 used a stable resonator. ABL design 

specifications require that an unstable resonator be used.4

 According to 

program officials, an unstable resonator is needed because it would 

produce a laser beam that would allow the ABL's beam control system to 

focus more of the beam's power on the target than would be possible with a 

beam produced by a stable resonator. In commenting on a draft of this 

report, DOD stated that a stable, versus unstable, resonator was used for 

the initial flight-weighted laser module tests because the test facility had a 

stable resonator in place, and to replace the stable resonator with an 

unstable resonator would have been too costly and would have adversely 

affected the program schedule.

In addition to demonstrating the laser module at full power, ATP-1 also 

required the program to demonstrate that the beam quality of the laser 

4

A resonator consists of two mirrors placed at opposite ends of a laser cavity. As the reaction of 

chemicals within the laser cavity produces photons of light, the photons are reflected back and forth 

between the two mirrors, which causes additional photons to be generated, resulting in a state of high 

energy within the cavity. In a stable resonator, one mirror is fully reflective while the other is only 

partially reflective, allowing part of the energy to escape from the laser cavity in the form of a 

high-energy laser beam. In an unstable resonator, both mirrors are fully reflective but one is much 

smaller in diameter. As the photons are reflected from the larger mirror in the direction of the smaller 

mirror, energy escapes from the laser cavity by passing around the edges of the smaller mirror in the 

form of a high-energy laser beam.
Chapter 3

Airborne Laser: Status, Cost, and Technical 

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Page 27 GAO/NSIAD-99-50 Defense Acquisitions

beam generated by the module would meet ABL design requirements. In 

meeting this requirement, the Air Force did not measure the quality of an 

actual laser beam generated by the module. Instead, it estimated the beam 

quality using computer models and measurements of the chemical flows 

within the laser. In future tests of the laser module, the Air Force plans to 

measure the beam quality of an actual beam generated by the laser module.

In attempting to demonstrate the laser module at full power, the Air Force 

identified several design problems. For example, the catch tank and catch 

tank outlet, which collect and recirculate a chemical used by the laser, 

were too small. This limited the flow rate of the chemical, reducing the 

laser's power. Another problem identified was that too much water vapor 

entered the laser cavity, which reduced the amount of power generated. In 

addition, gas pressure within the laser cavity was too high, thus slowing the 

velocity of gases through the cavity, which also reduced the amount of 

power generated.

Some modifications were made to achieve higher power levels during 

testing. These and other modifications are currently being finalized and 

incorporated into the flight-weighted laser module.

System Integration Challenges The ABL program manager stated that integrating a weapon-level laser, 

beam control system, and the other related components into an aircraft is 

the largest challenge facing the program. Some individual components of 

the ABL have been tested under laboratory conditions and the program 

office has conducted modeling and computer simulations. However, the 

individual components have not been integrated and tested as a complete 

weapon system. As we stated in our October 1997 report, until this system 

integration and testing is accomplished, it is not possible to predict with 

any degree of certainty the probability that the ABL program will evolve 

into a viable missile defense system.

A major aspect of this system integration testing will be the hot fire flight 

tests when the laser is turned on and the beam is controlled by the beam 

control system. According to planning documents, hot fire flight testing 

begins only 4 months prior to the 2003 theater ballistic missile shoot-down 

tests. Because of the complexity of the system integration task, some 

experts both inside and outside of DOD have noted that the planned flight 

testing schedule for the program is too dependent on successful tests and 

does not allow enough time and resources to deal with potential test 

failures and to prove the ABL concept.
Chapter 3

Airborne Laser: Status, Cost, and Technical 

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Page 28 GAO/NSIAD-99-50 Defense Acquisitions

In a May 1998 Early Operational Assessment, the Air Force Operational 

Test and Evaluation Center characterized the flight test schedule as 

"compressed and success-oriented." In addition, the Air Force Scientific 

Advisory Board, in its February 1998 report, "Airborne Laser Scenarios and 

Concept of Operations," stated that while the ABL program evolution as 

currently planned is rational in its sequencing of tests, the schedule 

appears to have an unrealistically brief flight testing phase. The Board 

characterized the flight test program as "immature" and said that it needs to 

be structured to build high confidence in the operability of the laser 

system. It further stated that past experience with high-power laser 

systems and large beam directors suggests that new and difficult problems 

will surface in that phase, and that many flights and targets will be needed 

to sort them out. The Board suggested that the laser should be fired a 

reasonably large number of times (in the hundreds) with the ABL in flight 

before committing to a lethality demonstration and that this would serve to 

gain experience; establish that it is safe, reliable, and routine; and measure 

the critical parameters that will give a commander the confidence to use 

the system without hesitation. Consequently, the Board advised the Air 

Force to develop contingency plans to prepare for the possibility that the 

current success-oriented schedule is not achieved, to include ordering 

additional long lead targets if required, the identification of potential 

avenues of failure during the flight tests, and preparation of work-arounds 

or corrective steps prepared in advance.

Congress has also raised concerns related to this issue. The conference 

report on the Strom Thurmond National Defense Authorization Act for 

Fiscal Year 1999 noted that the conferees are concerned that the Air Force 

plans to enter EMD without adequate time to operate, test, and evaluate the 

PDRR configuration. As a result, the conferees directed the Secretary of 

Defense to establish an independent review team to assist with the 

Secretary’s evaluation of the technical risk in the ABL program and his 

determination of whether (1) additional testing and risk reduction is 

necessary prior to integration of the ABL subsystems into a commercial 

747-400F aircraft and (2) the fully integrated PDRR aircraft should be 

operated for a period of time and thoroughly tested prior to finalizing an 

objective design. The act directed the Secretary of Defense to report the 

findings of his assessment of the ABL program by March 15, 1999.
Chapter 3

Airborne Laser: Status, Cost, and Technical 

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Page 29 GAO/NSIAD-99-50 Defense Acquisitions

Planned Ordering of 

the EMD Aircraft

May Be Premature

The technical complexity of the ABL and related integration issues raise 

questions about when a second aircraft, for modification during the EMD 

phase, should be ordered. Current program plans call for an aircraft to be 

ordered about 1 year before the planned attempts to shoot down a theater 

missile with the PDRR aircraft. 

The Air Force has a contract with Boeing for the aircraft that will be used 

during the PDRR phase. According to ABL acquisition plans, a second

747-400 freighter will be ordered in September 2002 for the EMD phase.5

 

The ordering of the aircraft is to immediately follow the August 2002 ATP-2 

meeting. However, this acquisition strategy will result in the second 

aircraft being ordered about 1 year prior to the scheduled demonstration of 

the ABL's ability to shoot down a theater ballistic missile.

Conclusions The ABL program has made progress in addressing some technical 

challenges, such as atmospheric turbulence, that we and others have 

reported on in the past. However, challenges will continue through the 

development program and we have concerns about some Air Force 

statements of program successes--specifically, statements related to the 

power output and beam quality of the flight-weighted laser module. Once 

these and other problems are resolved, the major program challenge will be 

to integrate the individual system components into a complete weapon 

system for testing. A major test for the program will be the flight tests 

during which the laser is turned on and its beam is controlled by the beam 

control system. Independent reviews of the ABL program by laser experts 

indicate that the ABL flight test plan may be too limited and too dependent 

on successful tests, and not allow enough time and resources to deal with 

potential test failures and to prove the ABL concept.

The technical complexity of the ABL and related integration issues also 

raise questions about when a second aircraft, for modification during the 

EMD phase of the program, should be ordered. Current plans call for the 

EMD aircraft to be ordered about 1 year before the PDRR aircraft attempts 

to shoot down theater ballistic missiles. If the PDRR aircraft fails to prove 

the ABL concept, the funds expended for the EMD aircraft may be wasted.

5

ABL acquisition plans call for a total of seven aircraft. One ABL is to be produced during the PDRR 

phase, a second during the EMD phase, and five more are to be developed during the production phase. 

Also, during the production phase, the aircraft from the PDRR and EMD phases are to be refurbished to 

production standards.
Chapter 3

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Page 30 GAO/NSIAD-99-50 Defense Acquisitions

Recommendation Regarding the ABL program, we recommend that the Secretary of Defense 

direct the Secretary of the Air Force to reconsider plans to exercise the 

option for the second ABL aircraft for the EMD phase of the program 

before flight testing of the ABL system developed during the PDRR phase 

has demonstrated that the ABL concept is an achievable, effective combat 

system.

Agency Comments and 

Our Evaluation

In a draft of this report, we recommended that the Secretary of Defense 

direct the Secretary of the Air Force to provide DOD an assessment of the 

need to expand the ABL flight test program. In commenting on that draft 

report, DOD partially concurred with our recommendation and stated that 

its ongoing assessment of the ABL program by an Independent Assessment 

Team (IAT) would constitute an appropriate assessment of the flight test 

program.6

 

Subsequent to DOD’s comments on our draft report, DOD completed its 

assessment of the ABL program and reported the results to Congress in 

March 1999. In its report, DOD noted the IAT’s agreement with Air Force 

plans to restructure the ABL program to expand testing and risk reduction 

activities before starting modifications to the PDRR aircraft (the first 

aircraft). DOD concurred with the IAT’s recommendation for more testing 

of the PDRR aircraft before Milestone II, which governs entry into 

engineering and manufacturing development. DOD stated that it will 

review the Air Force’s proposed restructured program and set a new 

Acquisition Program Baseline in the spring of 1999. During the 

restructuring and rebaselining effort, DOD stated that, among other things, 

it will revise the exit criteria for Milestone II to require more testing against 

threat-representative targets. 

DOD stated that it expects that adding flight tests to the program before the 

start of EMD will increase near-term costs and might delay ABL’s 

achievement of an initial operational capability. However, according to 

DOD, the added tests will ensure that the expenditures required for ABL’s 

EMD phase are justified.

6

 This assessment was required by the Strom Thurmond National Defense Authorization Act for Fiscal 

Year 1999.
Chapter 3

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Page 31 GAO/NSIAD-99-50 Defense Acquisitions

We agree with DOD’s assessment and future plans for the ABL program. 

Therefore, we deleted from our final report the recommendation for an 

assessment of the ABL flight test program.

Based on DOD’s comments on our draft report that DOD would not 

necessarily incur unnecessary costs by proceeding with the purchase of a 

second ABL aircraft, we revised our recommendation to reflect the need 

for DOD to reconsider its planned purchase in light of the IAT’s findings 

and our report.

We recognize that delaying the procurement of the aircraft for the EMD 

portion of the program until after the ABL demonstrates it can shoot down 

target missiles might require a change in the scheduled initial operational 

capability. However, such a slip would ensure that the procurement of the 

EMD aircraft would then be based on the additional knowledge gained in 

the shoot down demonstrations that the ABL design is feasible. Our 

recommended approach is consistent with DOD’s March 1999 report to 

Congress on the ABL program wherein it accepted a potential delay in the 

ABL’s initial operational capability in favor of obtaining additional data 

through increased flight tests. Our approach is also appropriate in view of 

the discussion in DOD’s March 1999 report on the impact of turbulence on 

the ABL design specification. DOD stated that optical turbulence in excess 

of the design specification along the slant path between the ABL and its 

target can reduce ABL’s maximum lethal range and increase required dwell 

times, even at lesser ranges. It said that some analyses of atmospheric 

turbulence data collected in theaters of interest to date suggest that 

turbulence levels well above assumed ABL design levels might occur more 

often than expected at the time the design levels were set. According to 

DOD, there are currently no clear methods for predicting the actual 

turbulence level along a slant path to a particular threat location at a given 

point in time. Thus, according to DOD, beyond trial and error, it is not clear 

how a correct decision can be made on whether a particular target can be 

successfully engaged when launched near ABL’s maximum lethal range. 

The Air Force is analyzing turbulence data and investigating tactical 

decision aids for the system to address this issue.
Page 32 GAO/NSIAD-99-50 Defense Acquisitions

Chapter 4

Space-Based Laser: Status, Cost, and 

Technical Challenges Chapte4r

The SBL program is about a year into a $30-million study phase to define 

concepts for the design, development, and deployment of an SBL proof of 

concept demonstrator. According to the program office, the SBL 

demonstrator would be the most technically complex spacecraft the United 

States has ever built. DOD is currently considering an acquisition strategy 

under which the demonstrator spacecraft would be launched in the 2010 to 

2012 time frame. Congress, however, has directed that the demonstrator be 

launched in the 2006 to 2008 time frame.

Status, Cost, and 

Technical Challenges

According to a senior SBL program official, the SBL readiness 

demonstrator will be the most complex spacecraft the United States has 

ever built. He also said that there is only a 50-percent chance that it will be 

built and deployed by 2008. According to SBL program officials, the weight 

and size constraints dictated by the size and weight limitations of existing 

and planned launch vehicles force the program to push the state of the art 

in areas such as laser efficiency, laser brightness, and deployable optics. 

DOD's programmed funding for SBL from fiscal year 1998 to 2005 totals 

$1.1 billion. DOD officials told us that the design, development, and 

deployment of an SBL readiness demonstrator would cost about $3 billion.

The conference report for the fiscal year 1998 National Defense 

Authorization Act states that the Secretary of Defense, in an August 1997 

letter to the Senate Majority Leader, confirmed that SBL technology had 

reached a level of maturity that could lead to a future space demonstration 

of a sub-scale vehicle. Consequently, the conferees directed the Air Force 

to promptly establish a baseline for a Space-Based Laser Readiness 

Demonstrator (SBLRD) to include a set of technical objectives and 

requirements, a contracting strategy, a system design, a program schedule, 

and a funding profile that would support a launch in fiscal year 2005. 

Further, to ensure the focus of the program remains on a fiscal year 2005 

(this deployment date was later changed to the 2006-2008 time frame) 

launch, the conferees directed that they be consulted prior to planned 

variances from this launch date. In addition, the conferees directed the 

Secretary of Defense to report on the status of the SBL readiness 

demonstrator baseline and related issues to the congressional defense 

committees by March 1, 1998. To date, DOD has not submitted its SBL 

baseline report to Congress.

In February 1998, the Air Force awarded two 6-month concept definition 

study contracts, valued at $10 million each, to Lockheed Martin and TRW 
Chapter 4

Space-Based Laser: Status, Cost, and 

Technical Challenges

Page 33 GAO/NSIAD-99-50 Defense Acquisitions

as an initial step to develop SBLRD. The contractors were tasked to 

evaluate three strategies: 

• a 2005/2006 launch of the SBLRD with existing technology,

• a 2008 launch with existing technology, and

• a 2008 launch infusing advanced technology.

In early 1998, the Air Force's acquisition strategy was to use evaluation 

data from these two efforts, along with other appropriate data, to award a 

contract in August 1998 to develop the SBLRD. The objectives of the 

demonstration would be to validate the SBL as a viable option for missile 

defense by demonstrating SBL technology readiness and to obtain 

performance and operations data regarding high-power space lasers, 

long-range precision pointing, adjunct missions feasibility, and to explore 

battle management issues.

When the initial acquisition strategy was provided to the Under Secretary 

of Defense for Acquisition and Technology in August 1998, the Under 

Secretary was concerned that the strategy focused only on the 

demonstrator and wanted to know whether the long-term program to 

develop and deploy the SBL would be affordable. Consequently, he 

directed the BMDO and the Air Force to restructure and expand the scope 

of the readiness demonstrator acquisition strategy to include the complete 

development and deployment of an SBL system. The restructuring was 

also to include review and assessment of other missile defense concepts 

such as ground-based lasers and space-based relay mirrors. In addition, the 

Under Secretary directed them to look for opportunities to develop 

technologies that would increase the affordability of the SBL by 

collaborating with other agencies such as the National Aeronautics and 

Space Administration, which is currently developing deployable optics for 

its next generation space telescope. In implementing this direction, BMDO 

and the Air Force restructured the acquisition strategy and extended the 

concept definition study contracts at a cost of $5 million each. In February 

1999, BMDO and the Air Force announced the award of a contract for a 

joint venture among Boeing, Lockheed Martin, and TRW for $125 million 

for initiating the Space-Based Laser Integrated Flight Experiment effort 

that is to result in deploying the readiness demonstrator in the 2010 to 2012 

time frame. According to BMDO officials, a full SBL system would not be 

deployed until after 2020.

The restructured strategy has not received final approval by DOD and is not 

consistent with Congress' direction to launch the SBL readiness 
Chapter 4

Space-Based Laser: Status, Cost, and 

Technical Challenges

Page 34 GAO/NSIAD-99-50 Defense Acquisitions

demonstrator in the 2006 to 2008 time frame. In the conference report for 

the fiscal year 1999 DOD Authorization Act, the conferees expressed 

concern over the lack of progress in awarding a contract for the readiness 

demonstrator and directed the Secretary of Defense to promptly release 

the request for proposals for the SBL readiness demonstrator. At the time 

of our review, BMDO officials did not know when or if the proposed 

restructured acquisition strategy will be approved and ultimately submitted 

to Congress

Conclusions The future of the SBL program is unknown at this time. DOD is currently 

doing a comprehensive assessment of the program. That assessment will 

include alternative ballistic missile defense concepts, such as ground-based 

lasers and space-based relay mirrors. If, based on this assessment, the SBL 

is ultimately selected, DOD estimates that a fully operational system would 

not be deployed until after 2020. Accelerating the deployment date would 

require the maturation of some complex technologies such as deployable 

optics and would require a large, but yet unknown, infusion of funds into 

the program.
Page 35 GAO/NSIAD-99-50 Defense Acquisitions

Chapter 5

Tactical High Energy Laser: Status, Cost, and 

Technical Challenges Chapte5r

The THEL is about 34 months into its $131.5 million 38-month development 

program. All of its components--such as the laser, the pointer tracker, and 

the pressure recovery system--have been built and are currently being 

tested. The system was scheduled to be integrated, tested, and ready to 

begin shoot-down tests against short-range rockets at White Sands Missile 

Range by December 1998. However, the shoot-down testing has been 

delayed 7 months due to administrative issues and technical problems with 

the laser and the pointer tracker. 

Although THEL's components have been produced, the technical 

challenges relating to testing and integration remain to be overcome. 

Initial testing of the laser has identified a problem with the chemical flow 

control valves. In addition, tests of the pointer tracker have identified 

problems with the low-power laser that is to track short-range rockets. 

Furthermore, integration and related testing have yet to begin.

Status and Cost of the 

THEL Program

In May 1995, a predecessor program to THEL, Nautilus, was started. 

Nautilus was a joint U.S.-Israel program to evaluate the effectiveness of 

lasers for potential use as a tactical air defense system against short-range 

rockets in a variety of missions, including peace-keeping operations. The 

U.S. Army Space and Missile Defense Command (SMDC), then called the 

Space and Strategic Defense Command, provided primary management 

functions for the program. The Israel Ministry of Defense provided support 

to SMDC. In February 1996, the Nautilus program culminated in a 

successful test at the Army's High Energy Laser Systems Test Facility 

(HELSTF) at White Sands Missile Range, New Mexico, using the MidInfrared Advanced Chemical Laser and Sea Lite Beam Director to engage 

and destroy a short-range Katyusha rocket.

In April 1996, President Clinton met with Israel's then Prime Minister 

Shimon Peres. At the meeting, the United States made a commitment to 

assist Israel to develop a Tactical High Energy Laser Advanced Concept 

Technology Demonstrator. This commitment, based on the success of the 

Nautilus program, was designed to help Israel defend its northern cities 

from the threat posed by Katyusha and other short-range rockets.

In May 1996, TRW was awarded a contract for $89 million to design, 

fabricate, and test a tactical-sized deuterium fluoride chemical laser 

capable of defeating short-range artillery rockets. The original contract 

called for about a 22-month effort to design and build the system by March 

1998. Israel contributed $24.7 million toward the contract cost and 
Chapter 5

Tactical High Energy Laser: Status, Cost, and 

Technical Challenges

Page 36 GAO/NSIAD-99-50 Defense Acquisitions

developed components such as the fire control radar system, laser fluid 

supply system, and pressure recovery system (laser exhaust system). In 

January 1998, the contract was modified to increase its value by

$42.5 million to $131.5 million (increasing the U. S. contribution to 

$106.8 million) and to extend the completion date by 11 months to 

February 1999 for integration and rocket shoot-down testing at HELSTF. 

This testing was scheduled to begin in December 1998. However, testing of 

the laser and the pointer tracker has revealed problems that have, along 

with administrative issues associated with contract initiation, caused the 

schedule to be delayed by 7 months, to July 1999.

Technical Challenges Facing

the THEL Program

THEL's components have been produced. However, initial testing of the 

laser has identified problems with the operation of chemical flow control 

valves and with the low-power laser that is to be used in tracking the 

short-range rockets.

The initial tests of the laser revealed leaks in the specialized valves that 

control the flow of chemicals through the laser. These leaks must be 

corrected because they would detract from the performance of the laser. 

In addition, testing of the pointer tracker system disclosed a problem with 

the low-power laser that is to be used in tracking incoming short-range 

rockets. This laser is a commercial off-the-shelf item that is generally used 

in laboratory settings. It has been modified for use on the THEL; however, 

it is still undergoing tests to ensure it meets performance requirements.

The valve leaks and the problems with the low-power laser in the pointer 

tracker system have caused a delay in the THEL test schedule. Originally, 

the THEL system was scheduled to be a fully integrated system that would 

attempt to shoot-down a Katyusha rocket at HELSTF in December 1998. 

Because of these unanticipated problems and administrative issues, the 

schedule has slipped by 7 months, to July 1999.
Chapter 5

Tactical High Energy Laser: Status, Cost, and 

Technical Challenges

Page 37 GAO/NSIAD-99-50 Defense Acquisitions

A U.S. Requirement for 

THEL-Type System

Would Present Additional 

Technical Challenges

Currently, U.S. forces do not have a validated mission requirement for the 

THEL as it is being designed for Israel.1 However, the Army has prepared a 

draft mission needs statement for a reconfigured mobile laser weapon that 

could be used by U.S. forces to shoot down a variety of targets in theater 

environments. A THEL official told us that the draft Army mission needs 

statement is being incorporated into Atlantic Command's Joint Theater and 

Missile Defense mission needs statement, which includes the need for a 

mobile high-energy laser weapon.

The THEL would have to be radically modified for it to be more powerful 

and mobile and thus meet emerging U.S. theater defense requirements for a 

ground-based laser. While the THEL system being developed for Israel is 

designed to be transportable, it will not be mobile; THEL components must 

be transported by large trucks and placed on prepared concrete sites. 

According to laser experts at Lawrence Livermore National Laboratory, a 

mobile, ground-based high-energy laser weapon for U.S. use would 

probably necessitate using a relatively small solid-state laser (versus the 

much larger and heavier chemical laser being developed for the THEL), the 

technology for which is relatively immature. The experts said that a 

generation of solid-state laser research and development would be needed 

to develop technology to the level necessary for use in a mobile THEL-type 

system. A program official said that such a system would probably not be 

fielded until at least 2025. In commenting on a draft of this report, DOD 

stated that the Army is investigating four solid-state laser concepts and the 

availability dates and concepts may be different than the assessment 

provided by Lawrence Livermore National Laboratory officials.

Conclusions Of the three laser weapon systems that DOD is developing for use against 

theater ballistic missiles or short-range artillery rockets, the THEL is 

closest to becoming a fielded system. It is being developed in a relatively 

short time frame at a relatively low cost. Because THEL is a follow-on to 

an earlier laser weapon program, its successful development and fielding 

have been considered relatively low risk. However, technical problems and 

their associated program delays demonstrate the complex nature of 

developing laser weapons of this type. Lessons learned from the THEL 

1

The Navy has expressed interest in a THEL-type system for shipboard defenses, but does not have any 

major efforts planned in this area yet. In addition, the Commander in Chief, Korea, is looking at a 

THEL-type system for a counter-artillery role. Specifically, he is interested in using a laser weapon to 

help protect major assets in or near Seoul from enemy rocket attacks.
Chapter 5

Tactical High Energy Laser: Status, Cost, and 

Technical Challenges

Page 38 GAO/NSIAD-99-50 Defense Acquisitions

program will be beneficial if the United States decides to develop a THELtype system for its military forces. However, given the more demanding 

requirements that the U.S. will likely have, eventual success of the THEL 

program will not easily translate into a low-risk, problem-free U.S. 

program.
Chapter 5

Tactical High Energy Laser: Status, Cost, and 

Technical Challenges

Page 39 GAO/NSIAD-99-50 Defense Acquisitions
Page 40 GAO/NSIAD-99-50 Defense Acquisitions

Appendix I

Comments From the Department of Defense ApIexndi

See comment 1.

See comment 2.

See comment 3.

See comment 4.

See cimment 5.
Appendix I

Comments From the Department of Defense

Page 41 GAO/NSIAD-99-50 Defense Acquisitions

See comment 1.

See comment 1.

Now on

 pp. 8 and 30.

See comment 6.
Appendix I

Comments From the Department of Defense

Page 42 GAO/NSIAD-99-50 Defense Acquisitions

The following are GAO’s comments on the Department of Defense’s (DOD) 

letter dated February 19, 1999.

GAO Comments 1. The Secretary of Defense submitted his report on the Airborne Laser 

(ABL) program to Congress in March 1999, subsequent to DOD providing 

comments on a draft of this report. The Secretary reported that the ABL 

flight-test program will be expanded. Since this action is consistent with 

the recommendation in our draft report, we have deleted the 

recommendation from the final report.

2. We agree that operational testing for the ABL program will not begin 

until the engineering and manufacturing development (EMD) phase and 

have modified the text by deleting the word operational. However, we 

retained the term combat system because it refers to the ABL concept and 

not to the program definition and risk reduction (PDRR) aircraft.

3. We have modified the report to clarify that the Space-Based Laser (SBL) 

is a demonstration program. 

4. We have modified the report title and text to clarify that the Tactical 

High-Energy Laser (THEL) is not a theater ballistic missile defense system.

5. We have modified the text of the report to reflect that DOD has not yet 

reached a final position on the issue of atmospheric turbulence.

6. We did not assess the marketability of the 747 freighter aircraft by the 

Air Force if it decides to terminate or delay the ABL program. However, if 

after ordering the aircraft DOD decides to terminate the program, it would 

be liable for up to $50 million unless it can successfully sell its place in the 

production queue or sell the aircraft. DOD did not include in its comments 

an estimate to store the aircraft if the ABL program is delayed.
Appendix I

Comments From the Department of Defense

Page 43 GAO/NSIAD-99-50 Defense Acquisitions
Page 44 GAO/NSIAD-99-50 Defense Acquisitions

Appendix II

Major Contributors to This Report ApIexndi

National Security and

International Affairs

Division, Washington,

D.C.

Steven F. Kuhta

Boston Field Office Subrata Ghoshroy

Denver Field Office Ted B. Baird

Rich Horiuchi

(707317)
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