High-latitude-landing circumlunar free return trajectory design

Abstract

Purpose -The purpose of this paper is to design free return trajectories launching at lower-latitude launch site Wenchang and landing at relatively high-latitude landing site Siziwang Banner tailored to human lunar missions for China, and in general demonstrate the feasibility of high-latitude landings with acceptable entry range. Design/methodology/approach -Free return trajectories satisfying all basic constraints were generated directly by a high-fidelity model with multiple differential corrections. Suitable initial assumptions, control parameters, constraints and stopping conditions were set. Method was developed to automatically converge unlimited trajectories accurately to the same constraints, and their characteristics affected by the ephemeris were analyzed. Findings -Launching into lower Earth inclination plus high-latitude landing with acceptable entry range requires asymmetric trajectories with high inclination Earth entry only from the south. Periodic trends of parameters at launch, injection and entry were found and analyzed. Nominal trajectory covering phases from launch to landing for China human moon flight with minimum entry range were designed. Practical implications -Such trajectories can be used by China's future manned lunar missions. Spacecraft capability and ground station distribution shall adjust accordingly. Originality/value -Previous studies mainly concentrated on symmetric free returns using low-fidelity models first. This paper investigates asymmetric free returns skipping simplified gravity model approximation to simultaneously achieve high-latitude landing and acceptable entry range, and accurate automated generation of feasible trajectories daily across 19-year lunar nodal cycle within every monthly launch window without trial and error to reflect the actual effect by the ephemeris only. Others include landing accurately by controlling entry direction and range (and altitude), minimizing entry range and designing an effective scheme of differential correction for full convergence.

Generation of launch windows for high-accuracy lunar trajectories

“…The analytical first guesses of ground launch windows are verified to fall only within minutes of accurate solutions, which results in fast and reliable convergence. On the other hand, the first guesses include both TLI types, which allows the automated generation of complete sets of accurate lunar trajectories and launch windows as seen in the 19-year simulation by Yim and Baoyin (2015). The simulation in the work can be faster and include both TLI types using the method presented in this paper.…”

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

“…Due to the special environment of the lunar polar region and the discovery of water ice [9]- [10], the lunar polar region has irreplaceable value for scientific exploration and application development. Therefore, humans are paying increasing attention to the lunar high-latitude region and taking it as a hot spot [11]- [12], even considering the establishment of a lunar base in the lunar polar region in the future. Manned lunar missions are large systematic projects, of which the orbit scheme is an important component.…”