Strategic Defense Initiative

President Bush directed in January 1991 that the Strategic Defense Initiative (SDI) program be refocused to protect against limited ballistic missile strikes. Consequently, a proposed space-based interceptor system known as Brilliant Pebbles is now being assessed. During this early stage of Brilliant Pebbles' development, the Strategic Defense Initiative Organization (SDIO) has extensively used simulations to answer the question: If a system can be designed, manufactured, and deployed so that it functions as planned, will it provide the desired protection? SDIO believes that the answer is yes and is using the simulation results to improve the design. Congress should be aware, however, that the simulations are still immature and use many unproven assumptions. They do not prove that Brilliant Pebbles can be built and will work. Only later in the development cycle, after Brilliant Pebbles has been fabricated and tested, can assumptions be replaced with hard data. An extensive test program is planned over five years to gather information. As testing results replace assumptions, more confidence can be placed in the simulations' projections of the effectiveness of Brilliant Pebbles.

GAO found that: (1) as of December 1991, SDIO had not evaluated through computer simulations Brilliant Pebbles' performance against a variety of interceptors deployed against certain hypothetical ballistic missile attacks; (2) to assess effectiveness, SDIO has identified over 40 hypothetical attack scenarios or threats against the United States and its allies, which include short, intermediate, and long-range ballistic missile attacks originating from all over the world and submarine-launched attacks against the United States; (3) Brilliant Pebbles could not intercept missiles with ranges of less than 400 to 600 kilometers or those with altitudes less than 80 to 100 kilometers which means that Brilliant Pebbles could not attack some missiles currently owned by third world countries; (4) the number of weapons deployed and the angle at which the rings of weapons cross the equator have a direct effect on the performance of the Brilliant Pebbles constellation against a given threat; (5) SDIO has performed simulations in which the number of weapons in orbit varies from a few hundred to over a thousand, which indicates that the effectiveness of a hypothetical Brilliant Pebbles constellation improves as the number of weapons in orbit increases; (6) the simulations SDIO uses to estimate the effectiveness of Brilliant Pebbles are relatively immature and use too many unproven assumptions about the performance and operation of the constellation; and (7) as Brilliant Pebbles development progresses, SDIO plans to replace early assumptions about Brilliant Pebbles' performance with data obtained through testing and continued simulation.