Analytical entry guidance scheme for multiple complex-shape no-fly zones avoidance

An analytical entry guidance scheme is proposed to address a challenging problem where a Hypersonic Glide Vehicle (HGV) needs to avoid multiple complex-shape No-Fly Zones (NFZ), which are circular, elliptical, and polygonal in shape. First, a tangent-arc method is designed to search multiple candidate waypoint sequences, where the waypoints are the tangency points of the NFZs over the spherical Earth, and the vehicle will be guided to target by following one of the sequences. However, as the HGV is unpowered, NFZ-avoidance maneuvers will speed up the deceleration of the velocity, and so not all the sequences are feasible. Hence, analytical trajectory solutions are used to judge the feasibility of each sequence by planning a reference trajectory which passes through all the waypoints of the sequence, does not intersect with any NFZ, and makes the vehicle reach the target with the desired speed. Finally, a guidance algorithm is designed to track the reference trajectory. For energy management, the guidance steers the vehicle to the next waypoint by performing careful S-turn maneuvers in order to consider the constraints on speed and heading angle at the waypoint. Monte-Carlo simulations validate that the proposed scheme is capable to handle complex flight missions.