Reduced-order pulse-motor ignition control logic

Abstract

The higher total impulse and energy management potential available in a pulse motor can be exploited with optimal guidance and propulsion control methods to improve missile performance. Under the assumptions of same propellant formulation and similar grain configuration of the pulses, a pulse motor can generally deliver higher specific impulse than its boost-sustain counterpart, leading to higher total impulse with the same launch weight despite a weight penalty on the pulse motor due to barrier insulation and an additional igniter; moreover, the pulse motor also allows arbitrary pulse delays between pulses. To fully exploit such energy management capabilities requires a real-time on-board pulse ignition controller. This paper studies the pulse ignition problem for a generic medium-range air-to-air missile from an optimal control viewpoint, using a minimum flight-time performance index. To make real-time mechanization feasible with state-of-the-art microprocessors, the optimal control solution is reduced to an implementable algorithm using singular-perturbation arguments and engineering approximations for the midcourse guidance problem. The resulting ignition control used in conjunction with the midcourse guidance law is then shown to command pulse ignition within the desirable period, leading to significant performance improvement over the boostsustain motor.