Theater Missile Defense

The Air Force has yet to demonstrate it can accurately predict levels of turbulence that will confront the airborne laser, which is being designed as the primary weapon for intercepting theater ballistic missiles shortly after launch. For example, Air Force data suggest that the levels of turbulence that the airborne laser may encounter could be four times greater than levels in which the system is being designed to operate. Predicting turbulence is one of many technical problems that must be solved before the airborne laser can become a viable missile defense system. Integrating the laser beam with military aircraft will be a major challenge. The Air Force must build a new laser that is able to contend with size and weight restrictions, motion and vibrations, and other challenges and yet be powerful enough to sustain a killing force over a range of at least 500 kilometers. In addition, the laser beam control system, which consists of complex software, moving telescopes, and sophisticated mirrors, will have to compensate for turbulence and control the direction and size of the laser beam. So far, the Air Force has not shown how well a beam control system of such complexity can operate on an aircraft.

GAO noted that: (1) the ABL program is the Department of Defense's (DOD) first attempt to design, develop, and install a multimegawatt laser on an aircraft and is expected to be DOD's first system to intercept missiles during the boost phase; (2) a key factor in determining whether the ABL will be able to successfully destroy a missile in its boost phase is the Air Force's ability to predict the levels of turbulence that the ABL is expected to encounter; (3) the Air Force has not shown that it can accurately predict the levels of turbulence the ABL is expected to encounter or that its technical requirements regarding turbulence are appropriate; (4) because ABL is an optical weapons system, only optical measurements can measure the turbulence that will actually be encountered by the ABL laser beam; (5) the Air Force has no plans to take additional optical measurements and instead plans to take additional non-optical measurements to predict the severity of optical turbulence the ABL will encounter; (6) to ensure that the non-optical measurements can be validly applied to the ABL program, the Air Force must determine whether the non-optical measurements can be correlated to optical measurements; (7) until the Air Force can verify that its predicted levels of optical turbulence are valid, it will not be able to validate the ABL's design specifications for overcoming turbulence; (8) the Air Force has established a design specification for the ABL that is based on modelling techniques; (9) data collected by the program office indicate that the levels of turbulence that ABL may encounter could be four times greater than the levels in which the system is being designed to operate; (10) DOD officials indicated that a more realistic design may not be achievable using a current state-of-the-art technology; (11) in addition to the challenges posed by turbulence, developing and integrating a laser weapon system into an aircraft pose many technical challenges for the Air Force; (12) the Air Force must build a new laser that is able to contend with size and weight restriction, motion and vibrations, and other factors unique to an aircraft environment and yet be powerful enough to sustain a killing force over a range of at least 500 kilometers; (13) the Air Force must create a beam control system that must compensate for the optical turbulence in which the system is operating and control the direction and size of the laser beam; and (14) because these challenges will not be resolved for several years, it is too early to accurately predict whether the ABL program will evolve into a viable missile defense system.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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