ROBUST TRAJECTORY OPTIMIZATION FOR MARS ATMOSPHERIC ENTRY BASED ON UNCERTAINTY PROPAGATION

A robust optimization procedure of Mars atmospheric entry trajectory under uncertainty is newly developed in this paper. Uncertainty propagation due to both initial state and dynamical parameters are taken into account. In the proposed robust design framework, the original robust trajectory optimization problem is transformed into an equivalent deterministic one in the expanded higher dimensional state space by polynomial chaos expansion at first. Quantification of the stochastic cost, and boundary and path constraints in terms of polynomial chaos expansion is formulated. Then, hp-adaptive pseudospectral method is adopted to solve the equivalent optimal control problem numerically. Finally, the effectiveness of the proposed procedure is verified through final altitude maximization problem. And the obtained optimal trajectory is evidently more robust to uncertainties compared to traditional deterministic optimization and reliability-based optimization.