Accurate and fast design algorithm for free-return lunar flyby trajectories

• A linear approximation based fast prediction algorithm is proposed.
• A fast free-return lunar flyby trajectory design method is developed.
• The design method is suitable for large-scale computational mission analysis.

A linear approximation based fast prediction algorithm for the Earth–Moon transfer trajectory is proposed. Compared with the multi-conic technique, the algorithm dramatically improves the accuracy of the trajectory prediction results. Based on this prediction algorithm and the pseudostate theory, a preliminary design algorithm of the free-return lunar flyby trajectories between the Earth and the Moon is developed. Without numerical differential correction, an accurate solution can be obtained within a little computational time. A large number of numerical examples are carried out to examine the reliability and efficiency of this design algorithm. The results indicate that this design algorithm has a good balance between the accuracy and efficiency. It is valuable for the large-scale computational applications, such as the lunar exploration mission analysis.