Lunar orbit insertion targeting from the two-segment lunar free-return trajectories

This paper presents a method for designing a lunar orbit insertion (LOI) targeting sequence from a two-segment lunar free-return trajectory. To reduce the fuel consumption for lunar orbit targeting, the algorithm modifies the LOI sequence and simultaneously optimizes the midcourse lunar-targeting maneuver (LTM) time. The circular restricted three-body is used to construct the two-segment lunar free-return trajectories and to observe the trajectory characteristics during the midcourse transfer and lunar encounter. A high-fidelity lunar gravitational model is adopted to modify the initial estimates of the LTM time and LOI sequence. Numerical examples are presented to illustrate the fuel consumption for accomplishing the lunar global targeting from a specified two-segment lunar free-return trajectory. The result indicates the lunar global targeting can be achieved within a LOI budget of 2.6 km/s and LTM budget of 0.4 km/s. The use of the proposed method provides an accurate initial solution that can be further optimized rapidly on higher-fidelity models. The procedure is well suited for onboard, real-time control of lunar global access missions.