Low-thrust transfer to the Earth-Moon triangular libration point via horseshoe orbit

This paper proposes a novel method for the low-thrust transfer to the triangular libration points in the Earth-Moon system. Horseshoe orbit is explored as the coasting arc in this transfer scenario. By tangential thrust control strategy, the low-thrust transfer from the Earth to the short-period orbit around L-4 point is realized. The pseudospectral method is used to obtain another Earth-L-4 transfer trajectory by solving an energy-optimal low-thrust trajectory optimization problem. Interestingly, these two kinds of Earth-L-4 low-thrust transfer trajectories both share similar geometric configuration and velocity trend with a natural Horseshoe orbit, which evokes the main contributions of this paper that leveraging Horseshoe orbit as the coasting arc. The complete transfer trajectory is divided into three phases: Earth spiral phase, Horseshoe coasting phase and L-4 point insertion phase, where the first and the third are powered phases. The tangential thrust control strategy is used in the first phase to generate the transfer from the Earth to the Horseshoe orbit, and the pseudospectral method is utilized in the third phase to enable the transfer from the Horseshoe coasting arc to the L(4 )point by solving a time-optimal transfer problem. Then, by patching these two powered segments with the unpowered Horseshoe coasting arc, the Earth-L-4 low-thrust transfer is constructed.