Evolutionary Trajectory Optimization for Suborbital Spaceplane by Combining Direct and Inverse Trajectory Design Approach

This paper proposes evolutionary trajectory optimization methodology for suborbital spaceplanes that combines direct and inverse trajectory design approach. Guidance of suborbital spaceplane has attracted attention as a method to generate and update new trajectories in flight, and trajectory optimization by evolutionary computation enables global search. The trajectory of a spaceplane is subject to several strict constraints including flight path, aerodynamic loads, and longitudinal trim, making it difficult to find feasible solutions. The proposed methodology focuses on the dynamics of the trajectory, and flight constraints are handled efficiently. In the region where the angle of attack constraint changes drastically from transonic to hypersonic due to longitudinal trim constraints, the time history control input is directly designed to obtain the trajectory. In the end of the flight after deceleration to subsonic speed, the inverse design method is applied to satisfy the path constraints. The proposed method was validated by simulation, and it was confirmed that a diversity of solutions that fully satisfy the constraints can be obtained with a relatively small number of generations and individuals.