Fast guidance method of lunar landing based on dynamic programming

In this paper, a novel multi-stage trajectory transfer and fixed-point landing time optimal guidance method for the lunar surface emergency rescue mission is proposed. Firstly, the whole process motion and dynamics model for the lunar surface emergency rescue with four stages are established. Then, in the initial orbit transfer phase, the Lambert algorithm based on "prediction + correction" is designed for the non spherical gravitational perturbation of the moon. In the powered descent phase, the Hamiltonian function is used to design a time suboptimal explicit guidance law that can be applied in orbit in real time. Finally, aiming at the multi-stage global time optimal guidance, the whole time process guidance law is obtained by establishing the allowable control set for each stage in the whole process. The simulation results show that compared with the piecewise optimal control method, the present method has better optimization effect and shorter whole process time. It is of great significance to the possible emergency rescue mission of manned lunar exploration in the future.