Abstract: Idealized double twobody model is the universal hypothesis in the preliminary trajectory design of deep space. Based on this hypothesis, a return trajectory model with six independent parameters of lunar spacecraft from parking moon orbit including direct return trajectory and indirect return trajectory is designed. Through analysis of the six independent parameters and the time of outlet point, general relationships between constraint and free parameters are given to easily search certain trajectories. Finally, effectiveness of the proposed approach is validated by examples including two types of return trajectory.

Key words: return trajectory, preliminary design, general characteristic analysis, six independent parameters