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The author traces the history of U.S. research into the development of a system of space-based missile interceptors known as Brilliant Pebbles (BP). Equipped with sensors, these kinetic-kill vehicles were designed to locate and collide with incoming ballistic missiles (BMs), thereby destroying them before they could reach their targets. Although the program was cancelled due to opposition in Congress, and lack of interest during the Clinton Administration, the aerospace technology developed utilized a combination of essentially off-the-shelf commercial and military technology that is still available to U.S. aerospace development. Key Words: Brilliant Pebbles (BP); Inter-Continental Missiles (ICBMs); Strategic Defense Initiative (SDI); Anti-Satellite Systems (ASAT); DOD Advanced Research Agency; Clementine Space Mission; General George L. Monahan; Ambassador Henry Cooper; Defense Secretary Richard Cheney; Senator Sam Nunn; Lawrence Livermore Laboratory. Introduction In simple terms, missile defense systems consist of three basic components: sensors that detect and track missiles and missile warheads, weapons that intercept and destroy missiles and warheads, and battle management systems that integrate sensors and weapons into a coherent system. Regarding interceptors, there are two basic types: those that destroy their targets by means of an explosive warhead and those that physically collide with their targets. Interceptors of the latter type are know as hit-to-kill (HTK) interceptors or kinetic kill vehicles (KKV). The principles behind kinetic kill vehicles were articulated as early as 1960 in Project Defender, an inventory of missile defense technologies completed by the Department of Defense's Advanced Research Projects Agency. Given the state of technology when Defender started, the accepted wisdom was that destroying an ICBM warhead required the use of a nuclear-tipped interceptor. However, as Defender proceeded, faith in the accepted wisdom eroded. A July 1960 Defender paper put the matter as follows: Intuitively, one feels, that in trying to intercept anything traveling at ICBM velocities, the resultant miss distance would be large. Until recently, systems considerations have been based on the premise that miss distances would be of the order of one or two hundred feet. This dictated the use of nuclear warhead with its attendant high cost and weight, and other disadvantages. During our space based interceptor studies, consideration of light weight, 300 Ib., interceptor using an IR seeker led to the conclusion that miss distances of 10 to 30 feet could be achieved. At these distances, fragment type warheads exploiting hypervelocity impact for kill appeared reasonable against tankage, motors, and other parts of the ICBM in boost. Further study indicated that a cheap effective warhead could be built weighing as little as 2 lbs.2 Not only did it begin to appear that lightweight interceptors armed with conventional explosives were feasible, but even hit-to-kill interceptors. In the words of the Defender paper: Computer simulation runs on several types of interceptors weighing about 50 lbs., and using IR homing have resulted in miss distances of one or two feet. This certainly indicates hypervelocity impact kill could be employed. Incidentally, a nose cone traveling at ICBM velocities in collision with one pound of material releases the energy equivalent of 6 pounds of TNT. In a word, the kinetic energy at that velocity exceeds the chemical energy available at that mass.3 Another point to emerge from Project Defender was the advantages that accrue to the defense from using space-based interceptors to attack and destroy ICBMs while they are still in their boost phase. As the 1960 Defender paper put the matter: A ballistic missile is more vulnerable in its propulsion or boost phase then in any subsequent part of its trajectory. At the same time, its identity is most difficult to conceal. … |
