The term “boost-phase intercept” (BPI) refers to programs, strategies, and systems designed to intercept ballistic missiles during the course of their initial phase of flight, beginning with ignition and lasting through that period of time during which the missile’s stages are firing and providing thrust. The boost phase can last anywhere from 20 to 240 seconds, depending on the type and range of the missile. From the point of view of developing an effective missile defense system, there are distinct advantages to attempting to intercept a missile during this phase, but there also are daunting technical challenges involved. The advantages include the fact that a ballistic missile is traveling at its slowest speed while accelerating, the missile’s exhaust plume is bright and hot against the atmosphere and the surface of the Earth and thus more easily detected and tracked, and any countermeasures the missile might be carrying will not yet have been deployed. In many respects, a ballistic missile is at its most vulnerable during its boost phase. Having the capability to intercept missiles during this phase can contribute to a layered defense; if a missile fails to be intercepted during this phase, there remain the midcourse and terminal phases during which additional attempts can be made to intercept it.
Achieving an intercept during the boost phase is technologically very challenging. Since this phase of the missile’s flight is so short, there is very little time available for the process, which includes detecting its launch, tracking its flight, determining whether it is hostile, deciding whether to launch an interceptor missile or initiate some other interception method (such as using an airborne laser), and actually reaching the ascending and accelerating missile with another missile or kill mechanism. This approach thus places maximum stress on command and control systems and on the acceleration capacities of interceptor missiles, since their acceleration often must be many times that of the missiles they are intended to intercept. To be effective, a BPI system probably needs to be located very close to the bases from which the targeted missiles are launched.
Sea-based BPI systems have the advantage of mobility; they can be deployed off the shores of a hostile nation and relocated as circumstances require. They can also be deployed closer to the launch point, making early interception during the boost phase more likely. The United States is currently developing a very fast acceleration missile for deployment on navy ships intended as a boostphase interceptor. Sea-based systems, however, would be ineffective against missiles launched from deep within a hostile nation’s territory.
Space-based BPI systems, if developed, could orbit over any part of the Earth’s surface, providing global reach. The United States is pursuing long-range research and development into both a kinetic kill space-based intercept capability (designed to physically ram hostile missiles) and a directed energy space-based system (which would employ laser beams or focused X-rays to destroy a missile). But the first tests of prototypes for such systems are ten to twelve years off, and their effectiveness has yet to be validated.
Garwin, Richard L., “Boost-Phase Intercept: A Better Alternative,” Arms Control Today, September 2000, available at http://www.armscontrol.org/act/ 2000_09/bpisept00.asp.
Lamb, Frederick K., and Daniel Kleppner et al., “Boost- Phase Intercept Systems for National Missile Defense,”American Physical Society Report, July 2003, available at http://www.aps.org/public_affairs/ popa/reports/nmdexec.pdf.
“Missile Defense Systems and Boost-Phase Intercept,” Raytheon Corporation, available at http://raytheonmissiledefense.com/boost/.