Shape-based analytic representations of low-thrust trajectories for gravity-assist applications

A new kind of space trajectory will soon be added to the mission designer's arsenal: The low-thrust, gravity-assist trajectory. The technology of low-thrust, recently demonstrated by Deep Space 1, can significantly enhance the effectiveness of the tried and true pure gravity-assist technique, This paper addresses the problem of identifying the conditions under which such trajectories exist, Rather than directly addressing the optimization problem, we develop a shape-based analytic technique for identifying candidate low-thrust, gravity-assist trajectories. Application of this technique provides similar results to optimal trajectories reported in the literature, Such easily computed trajectories serve as initial guesses in optimization and for quick overviews of a broad launch-date space.