关键词: 地月转移, 弱稳定边界转移, 调相轨道, 应急轨道重构, 应急窗口

Abstract: To address the contingency scenario in which the second-stage engine shuts down prematurely at the end of the ascent phase in Earth–Moon direct transfer missions, thereby injecting the spacecraft into a large elliptical orbit, the conventional contingency trajectory reconstruction strategy of “phasing orbit + direct transfer” exhibits significant limitations, including a large total impulse and emergency windows constrained by the sidereal month. To address these issues, a contingency trajectory reconstruction strategy of “phasing orbit + Weak Stability Boundary (WSB)” is proposed. First, candidate transfer windows are identified based on orbital elements of the large elliptical orbit, and the Sun–Earth–Moon phase configuration is adjusted via multi-revolution phasing orbits. Second, a forward multi-step shooting method is employed to raise the apogee altitude, enabling the spacecraft to enter the WSB region. Combined with deep-space maneuvers at the apogee and solar gravitational perturbation, the spacecraft arrives in the vicinity of the Moon upon returning from apogee. Finally, differential correction is applied to iteratively correct the transfer trajectory, precisely satisfying the lunar low orbit (LLO) insertion constraints. Numerical simulations are conducted for the contingency trajectory reconstruction of the Chang’e-5 mission. The results show that, under different injection semi-major axis deviations, the “phasing orbit + WSB” strategy provides a continuous emergency transfer window of approximately 20 days within one month. Further integration of the Lunar Gravity Assist (LGA) scheme reduces the total impulse by up to 186.67 m/s, though the available window is restricted to once per month. The proposed strategy offers an effective technical reference for emergency trajectory design in future lunar exploration missions.

Key words: Earth–Moon transfer, Weak Stability Boundary transfer, Phasing orbit, Contingency trajectory, Contingency window