Space-Based Missile Defense with Early Interceptor Launch Strategies

There is renewed interest in space-based boost-phase intercept (SBPI) for missile defense against ICBMs of near-peer adversaries. We discuss SBPI in the context of other missile defense approaches, and address one of its challenges, which is the expense of fielding a large enough constellation of interceptors in space to counter even a small number of ICBMs. We develop an early-launch approach that could substantively reduce the required density of interceptors. Because every second matters in boost-phase defense, early launch of interceptors can significantly increase the reach of each interceptor. Early launch would require interceptors that have highly throttleable motors. Our simulations show that interceptors can be launched productively as soon as the threat is identified and before the precise trajectory is known, updating the intercept location continually with real time ICBM trajectory updates. Robust early detection of a launch, while critical to this approach, presents a significant technical challenge that we defer addressing in this initial study.