Solar sailing trajectory optimization with planetary gravity assist

Significant propellant mass saving can be obtained with the use of complex multiple intermediate flyby maneuvers for conventional propulsion systems, and trip time also decreases for a portion of the proper solar sail missions. This paper discusses the performance of gravity assist （GA） in the time-optimal control problem of solar sailing with respect to sail lightness number and the energy difference between the initial and final orbit in the rendezvous problem in a two-body model, in which the GA is modeled as a substantial change in the velocity of the sailcraft at the GA time. In addition, this paper presents a method to solve the time-optimal problem of solar sailing with GA in a full ephemeris model, which introduces the third body＇s gravity in a dynamic equation. This study builds a set of inner constraints that can describe the GA process accurately. Finally, this study presents an example for evaluating the accuracy and rationality of the two-body model＇s simplification of GA by comparison with the full ephemeris model.