Elliptical Orbit Guidance Scheme Research for Far-Range Rendezvous in Lunar Mission

The application of nearly-circular deviation equations in far-range rendezvous between spaceship and lunar module in elliptical orbit guidance scheme for manned lunar missions is researched. A four-pulse far-range rendezvous guidance scheme is designed, in which the out-of-plane parameters of orbit are corrected by a vertical pulse and the far-range rendezvous is realized by three in-plane phasing pulses. First, the positions of the first two phasing pulses are fixed. Then, in order to obtain the optimal solution of the total velocity increment, the position of the third in-plane pulse and three velocity increments of in-plane pulses are solved by the sequential quadratic programming algorithm with the total velocity increment transformed into the objective function. The correctness of the scheme is verified by scenario simulation, and the effective solution interval of the scheme with different initial positions and orbital eccentricity of the lunar module is analyzed. The simulation shows that different initial positions and orbital eccentricity of the lunar module have significant effects on effective phase angles between spaceship and lunar module which are able to be solved successfully by nearly-circular deviation equations.