Optimization of Interplanetary Trajectories With Unpowered Planetary Swingbys

Many of the trajectories currently being examined for future planetary missions involve repeated planetary flybys with a high probability that some of these flybys are unpowered. Indeed the current baseline trajectory for Galileo involves an unpowered swingby of Venus followed by two unpowered swingbys of the Earth. This paper presents a method of both calculating and optimizing unpowered planetary swingby trajectories using a patched conic trajectory generator. Several examples of unpowered swingby trajectories are included to demonstrate the capability of solving this type of planetary mission using the formulation to be presented in this paper.