Optimal interplanetary trajectories using constant radial thrust and gravitational assists

The missions to planets outside the orbit of Mars using radial thrust propulsion and gravity assist trajectories were investigated. It was found that 5-deg thrust angle reduced the required impulsive velocity change to circularize the final orbit. The change was effected without a significant increase in burn time or total flight time. A solar-powered propulsion system was preferred during flyby transfer of the space flight from one planet to another through a middle planet as a smaller cutoff radius was produced during this transfer.