Launch window for manned Moon-to-Earth trajectories

Purpose - The purpose of this paper is to establish an orbital launch window for manned Moon-to-Earth trajectories to support China's manned lunar landing mission requirements of high-latitude landing and anytime return, i.e. the capability of safely returning the crew exploration vehicle at any time from any lunar parking orbit. The launch window is a certain time interval during which the transearth injection may occur and result in a safe lunar return to the specified landing site on the surface of the Earth. Design/methodology/ approach - Using the patched conic technique, an analytical design method for determining the transearth trajectories is developed with a finite sphere of influence model. An orbital launch window has been established to study the mission sensitivities to transearth trip time and energy requirements. The results presented here are limited to a single impulsive maneuver. Findings - The difference between the results of the analytical model and high-fidelity model is compared. This difference is relatively small and can be easily eliminated by a simple differential correction procedure. The launch window duration varies with launch date, from less than one hour to greater than 20 h, and the launch window occurs every day in the sidereal month. Research limitations/implications - The solution can be used to serve as an initial estimate for future optimization procedures. Practical implications - The orbital launch window can be used to provide the basis for the preparation of an orbital launch timetable compatible with lunar missions and re-entry conditions requirements. Originality/value - Previous studies were mainly concentrated on the launch windows for the departure from the Earth. This paper investigates and establishes the orbital launch window for Moon-to-Earth trajectories.