Reentry trajectory optimization for hypersonic vehicle satisfying complex constraints

The reentry trajectory optimization for hypersonic vehicle (HV) is a current problem of great interest. Some complex constraints, such as waypoints for reconnaissance and no-fly zones for threat avoidance, are inevitably involved in a global strike mission. Of the many direct methods, Gauss pseudospectral method (GPM) has been demonstrated as an effective tool to solve the trajectory optimization problem with typical constraints. However, a series of difficulties arises for complex constraints, such as the uncertainty of passage time for waypoints and the inaccuracy of approximate trajectory near no-fly zones. The research herein proposes a multi-phase technique based on the GPM to generate an optimal reentry trajectory for HV satisfying waypoint and no-fly zone constraints. Three kinds of specific breaks are introduced to divide the full trajectory into multiple phases. The continuity conditions are presented to ensure a smooth connection between each pair of phases. Numerical examples for reentry trajectory optimization in free-space flight and with complex constraints are used to demonstrate the proposed technique. Simulation results show the feasible application of multi-phase technique in reentry trajectory optimization with waypoint and no-fly zone constraints.