Research on hybrid design method of gravity-assist trajectories for interplanetary missions

Taking the exploring Mars via Venus gravity-assist as the background, a hybrid design method of gravity-assist trajectories for interplanetary missions is proposed to the problems of conventional design method of gravity-assist trajectory. First, based on analysis of characteristics of gravity-assist celestial bodies, we provide the possible parameter matching regions for gravity-assist trajectory by using the contour map of hyperbolic excess velocity. Then, while patching the segments of gravity-assist trajectories, we present the "Soft matching" strategy instead of the classical matching strategy. Finally, the hybrid optimal algorithm is used to optimize the design parameters of gravity-assist trajectories. This method could resolve effectively the problem that conventional method omits gravity-assist opportunities satisfied with constraints. Taking the exploring Mars via Venus gravity-assist in 2017-2018 years as an example, we not only provide the design results that agree with that of Okutsu, but also find a new trajectory profile in the same parameter region. In addition, we also analyze the transfer opportunities for exploring Mars with Venus gravity-assist in the period of 2010-2018, and provide the better design parameter regions. These researches will present the significant reference for the future Mars mission.