Based on the need for switching the landing site in an emergency during the return flight of a crewed lunar exploration mission, an emergency transfer trajectory is designed and analysed. First, the problem of generating a single transfer trajectory for switching the landing site in an emergency is equivalently converted to solving a Lambert problem. Second, a calculation method based on homotopic continuation is proposed to obtain the high-fidelity solution of the Lambert problem in the complex gravitational field of the Earth-Moon system. Based on this calculation method, the design algorithm of an emergency transfer trajectory is put forward, and an improved differential evolution algorithm is used for optimization. The results of simulation examples indicate that the calculation method of the Lambert problem based on homotopic continuation has good convergence, and also verify the effectiveness and feasibility of the trajectory design algorithm proposed in this paper. Finally, extensive simulation calculations are carried out by adopting this method, and the impulsive manoeuvre characteristic of the emergency transfer trajectory is discussed. The research conclusions can provide a reference for the design of an emergency rescue scheme during the return flight of a crewed lunar exploration mission in the future.

基于载人探月任务返航过程中紧急切换着陆点的需要，设计并分析了一条应急转移轨迹。首先，在紧急情况下为切换着陆点生成单一转移轨迹的问题等价地转换为解决朗伯问题。其次，提出了一种基于同伦延拓的计算方法，以获得地月系统复杂引力场中Lambert问题的高保真解。基于该计算方法，提出了应急转移轨迹的设计算法，并采用改进的差分进化算法进行优化。仿真算例结果表明，基于同伦延拓的Lambert问题计算方法具有较好的收敛性，也验证了本文提出的轨迹设计算法的有效性和可行性。最后，采用该方法进行了大量的仿真计算，讨论了应急转移轨迹的脉冲机动特性。研究结论可为未来载人探月任务返航过程中应急救援方案的设计提供参考。讨论了紧急转移轨迹的脉冲机动特性。研究结论可为未来载人探月任务返航过程中应急救援方案的设计提供参考。讨论了紧急转移轨迹的脉冲机动特性。研究结论可为未来载人探月任务返航过程中应急救援方案的设计提供参考。