Trajectory optimization for lunar soft landing with complex constraints

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Trajectory optimization for lunar soft landing with complex constraints

Chu, Huiping / Ma, Lin / Wang, Kexin / Shao, Zhijiang / Song, Zhengyu

Highlights•A unified trajectory optimization framework is proposed for lunar soft landing.•Advanced initialization strategies improve the performance of optimization.•Use R functions to describe discontinuous thrust constraints in the same problem.•Results demonstrate the adaptability of the framework for various landing missions.

AbstractA unified trajectory optimization framework with initialization strategies is proposed in this paper for lunar soft landing for various missions with specific requirements. Two main missions of interest are Apollo-like Landing from low lunar orbit and Vertical Takeoff Vertical Landing (a promising mobility method) on the lunar surface. The trajectory optimization is characterized by difficulties arising from discontinuous thrust, multi-phase connections, jump of attitude angle, and obstacles avoidance. Here R-function is applied to deal with the discontinuities of thrust, checkpoint constraints are introduced to connect multiple landing phases, attitude angular rate is designed to get rid of radical changes, and safeguards are imposed to avoid collision with obstacles. The resulting dynamic problems are generally with complex constraints. The unified framework based on Gauss Pseudospectral Method (GPM) and Nonlinear Programming (NLP) solver are designed to solve the problems efficiently. Advanced initialization strategies are developed to enhance both the convergence and computation efficiency. Numerical results demonstrate the adaptability of the framework for various landing missions, and the performance of successful solution of difficult dynamic problems.