Generation of Multisegment Lunar Free-Return Trajectories

Abstract

To support the mission and trajectory design problems associated with the Earth-to-moon trajectories for a crewed vehicle, a multisegment lunar free-return trajectory is proposed. The multisegment free return differs from hybrid profiles in that it consists of free-return sections only; however, it maintains the advantages of hybrid returns. The analysis presented here is limited to a two-segment class of trajectories. In this profile, the translunar injection puts the spacecraft onto a free-return trajectory with a high perilune altitude; then, the spacecraft performs a transfer maneuver onto a new translunar coast trajectory that has an approximate perilune altitude of 100 km. This new translunar coast trajectory is also designed as a free-return trajectory that can perform a safe return. With a finite sphere of influence model, an analytical model of the multisegment free-return trajectories is developed by the matched-conic technique. Characteristics of the injection velocity, flight time, and lunar approach inclinations of the multisegment lunar free returns have been extensively investigated. The results indicate that multisegment free returns allow a wider range of lunar approach inclinations and freer launch window than free-return profiles.