Interplanetary Trajectory Design via Short-Term Stays in Sun–Planet Systems

Giant planets are essential for investigating the origin of the solar system. Trajectories to these planets are typically designed using the multiple gravity-assist (MGA) technique, where the phases between gravity-assist targets are critical for determining feasible transfer opportunities. Due to the differing orbital periods of the planets, these opportunities are limited to specific years. To address this challenge, this paper presents a novel method for designing interplanetary trajectories. The method exploits the unique short-term stay (STS) motion in the three-body system to adjust the transfer phases between gravity-assist planets, thereby expanding the available transfer opportunities. First, the feasible set for STS is constructed using the periapsis Poincaré map, and the correlation between stay duration and the initial periapsis state of STS is analyzed. Second, a method is proposed to determine the optimal STS trajectory, which is subsequently linked to optimal interplanetary trajectories via periapsis maneuvers, allowing for flexible transfer phase adjustment. Finally, this method is applied to design the Uranus exploration trajectory. Compared to the classical MGA trajectory, it significantly increases transfer opportunities by incorporating the STS segment within the Jupiter system. Moreover, the transfer phase improvement achieved through STS results in a reduction in maneuver costs by approximately 26%.