Tactical Missile Guidance with Passive Seekers Under High Off-Boresight Launch Conditions

For future short-range air-to-air missile concepts, it has been recently demonstrated that throttleable hybrid rocket motors, coupled with linear optimal guidance laws, provide significant performance improvements over traditional solid rocket motors utilizing similar guidance laws in high off-boresight launch conditions. A problem associated with these optimal guidance laws is that they require missile-to-target position, velocity, and acceleration. For practical missile applications, only the initial values of relative position and velocity and an initial guess of the target's acceleration would be available from the launching aircraft. To further complicate the situation, most short-range missiles use a passive seeker, providing angle-only measurements, and accelerometers to measure the missile's accelerations. An extended Kalman filter (EKF) is developed to estimate the required guidance information using passive seeker measurements. The performance of a missile with a passive seeker in high off-boresight launch conditions is evaluated using the combination of an EKF and the guidance law. In particular, a comparison is made between three guidance schemes using estimated states from an EKF. The three guidance schemes are 1) an optimal guidance law coupled with a solid rocket motor, 2) an optimal guidance law coupled with a hybrid rocket motor, and 3) proportional navigation coupled with a solid rocket motor. The results show that the optimal guidance law coupled with a hybrid rocket motor provides a significant improvement in high off-boresight, air-to-air engagements over proportional navigation and the optimal guidance law coupled with a solid rocket motor. (Author)