Interceptor Line-of-Sight Rate Steering: Necessary Conditions for a Direct Hit

The zero-effort miss of an interceptor is a vectorthat measures the closest pass to the target that will occur on its current trajectory if no corrective control is applied. The position divert is the change in the zero-effort miss that occursas a resultof applying control. A necessary condition fora zero miss is that the magnitudeofthe interceptor zero-effortmissbesmallerthan thatofthemaximum positiondivertatallvaluesofinterceptor ‐targetrange. Using this condition, a criterion for a hit is established: The set of probable zero-effort misses must always be a subset of the set of position diverts. Because it is impossible to meet this condition for arbitrarily small interceptor ‐target range, there must be some critical range at which the guidance fails. The work is limited to predictive homing guidance using reaction control and shows how the guidance failure mechanism ine uences the interceptor miss. A simple approximate expression for miss distance is obtained, in terms of homing seeker noise, maximum divert acceleration, and uncertainty about target acceleration.