Contingency trajectory design for the launch-phase failure of cislunar missions

In the past few years, international interest has been gradually revived in human explorations of the cislunar space. While multiple transfers from the Earth to the cislunar space have been investigated, critical operational challenges remain unsolved. Specifically, the premature shutdown or precision limitations of the rocket may result in insufficient orbital insertion energy or direction deviations and increase mission failure risks. This paper designs a contingency strategy to address failures during the launch phase. By selecting a lunar gravity assist (LGA) transfer orbit from the low Earth orbit (LEO) to the distant retrograde orbit (DRO) as the nominal orbit, the impact of the energy and direction deviations on the orbital evolution is analyzed in the bicircular restricted four-body problem (BR4BP). Four recovery options are then proposed, including patching the nominal orbit, reconstructing the LGA transfer, and converting to the weak stability boundary (WSB) transfer from the perilune or perigee. Results indicate that the optimal contingency cost is approximately 200-400 m/s, within the range acceptable for practical missions.