Space-Based Missile Defense

Published Apr 1, 2011 Updated Jun 1, 2017


A space-based boost-phase missile defense system is intended to target ballistic missiles in the first few minutes of flight, while the missile’s engines are burning and providing a bright target. Proponents argue that by engaging a missile during boost phase, space-based interceptors (SBIs) could avoid the crippling problems that plague interceptors designed to engage warheads during midcourse phase, when the warhead is above the atmosphere. A boosting missile is a more attractive target than a warhead because it is large, easy to detect (given its large plume), and vulnerable to attack (as it is not hardened).

However, such a system would require many hundreds of orbiting interceptors to defend against one or two missiles, and it would have serious inherent vulnerabilities that would render it ineffective.

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