Resonant gravity-assist trajectory design for Sun’s middle latitude exploration

Sun's middle latitude exploration targets on the observation of the solar middle-latitude region from inclined orbits. In order to achieve this, resonant gravity-assists trajectory(RGA) was investigated considering the constraints of nearest distance to the Sun. After the deduction of analytical expression of out-going excess velocity, dimensional normalization was performed in order that the results can be applied to any gravity-assist planet with proper scaling. Then a novelty graphical method for gravity-assist analysis was proposed as RRpInc graph, which visualized the relations in resonance ratio, normalized perihelion and inclination. From RRpInc graph, the magnitude of excess velocity was concluded to be the key parameter for final inclination. Thus several other gravity-assists should be carried out before RGA and optimized by multi-objective genetic algorithm for both minimum escape energy and maximum excess velocity at the beginning of resonant gravity-assist planet. Then RRpInc graph was used to get the proper resonant ratio. Two trajectory options are listed up as promising choices. The first option takes a flyby sequence of venus-earth-earth(VEE) before Venus resonant gravity-assists to the final inclination of 30 . The second option uses Jupiter flyby to speed up, which is followed by Earth resonant gravity-assists to reach an solar ecliptic inclination of 35 .