Steady Glide Reentry Trajectory Optimization with Waypoint and No-fly Zone Constraints

This paper studies the hypersonic reentry trajectory optimization problem considering waypoints and no-fly zones constraints. This problem is difficult to solve because of (1) the poor damping phugoid oscillations, (2) the constraints on waypoints and no-fly zones, and (3) the rapid changes in part of the trajectory. To suppress the oscillations, we establish a novel reentry dynamic model by embedding the trajectory damping control technique (TDCT) in it, and thus successfully enhance the damping of the trajectory. To improve the accuracy of the model, we establish an exact mathematical model for the no-fly zone constraint over the spherical Earth. Considering the rapid changes in part of the trajectory and some strict constraints, we divide the whole trajectory into phases and adopt the multi-phase Radau pseudospectral method (MRPM) to solve the optimal control problem. Moreover, an adaptive mesh refinement strategy is applied to guarantee the solution precision by infilling grid or adjusting the interpolation polynomial order. The proposed method requires a light computational load to obtain the optimal trajectory satisfying the waypoints, no-fly zones and other constraints. Compared with the Gauss pseudospectral method (GPM), the trajectory planned by the proposed method is accurate, smooth, and easy to track.