Three-Impulse Return Orbit Design and Characteristic Analysis for Manned Lunar Missions

Return orbit design and characteristic analysis are very important issues in manned lunar missions. In this paper, a three-impulse return orbit scheme is studied. First, a convenient method based on the conical surface of the hyperbolic excess velocity is proposed, which can effectively perform an approximate analysis of the velocity increment characteristic. Second, a serial orbit design strategy is presented to determine the entire return orbit from the lunar parking orbit to the intended landing site. In the initial design, a three-segment orbit patched method based on the pseudo-perilune parameters is applied. Backward and forward calculations are conducted in the hybrid orbit model and the patched-conic model respectively, with the perilune of the lunar escape orbit as the dividing point. In the accurate design, a two-segment orbit patched method is employed in the high-fidelity model. Finally, numerical simulations are used to verify the effectiveness and feasibility of the orbit design strategy. According to many simulation results achieved by this strategy, the characteristics of fixed-point return window and velocity increment are further analyzed.