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. 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. 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) 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. 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. 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. We conducted our review from November 1997 to December 1998 in accordance with generally accepted government auditing standards. 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. 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 rocket attacks in the final stages of the rockets' flight. 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. 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 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. 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. DOD is developing the SBL to provide a continuous global boost phase intercept capability for both theater and national missile defense. The 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. 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.