Optimal earth-moon transfers using lunar gravity assist in the restricted four-body problem

In this paper, optimal two-impulse Earth-Moon transfers using the lunar gravity assist (LGA) are designed and investigated in the restricted four-body problem (RFBP) with the Sun, the Earth, and the Moon as primaries. Using the double LGA orbit as the initial guess, we propose an optimization method of the Earth-Moon transfer using the LGA in the RFBP. In our design process, the optimization problem in the RFBP is decomposed into several easier optimization subproblems in the easier models to reduce the difficulty of the optimization problem. Then, the optimal LGA transfers are displayed and analyzed. The results indicate that the LGA is an important technique in the Earth-Moon transfer design, which can efficiently save the fuel cost, but the LGA transfer duration must be larger than a period of the Earth-Moon system.