Waypoint constrained guidance for entry vehicles

A guidance algorithm for the waypoint constrained atmospheric entry is presented. To guarantee that the vehicle is able to reach all the waypoints and the final target accurately, the flyby direction constraint for each waypoint is investigated. The controllable and reachable sets for the vehicle's velocity heading angle are defined and calculated. The expected heading angle is obtained from these sets and used as a direction constraint for the corresponding waypoint. Under the location and direction constraints, a bank reversal strategy based on the trajectory prediction is developed. With this strategy, a lateral trajectory that satisfies the waypoint constraint is generated online. Tracking laws for the longitudinal and lateral trajectories are designed. Finally, the guidance algorithm is tested on the Common Aero Vehicle model in highly constrained flights. Results show that the conventional path constraint, the terminal constraint and the additional waypoint constraint are all well satisfied, which indicates the effectiveness of the proposed guidance algorithm.