Optimization of variable-specific-impulse gravity-assist trajectories

This paper presents a series of optimization methods for finding fuel-optimal gravity-assist trajectories that utilize the practical solar electric propulsion with variable specific impulse. An optimization method combining the particle swarm optimization and the indirect method is proposed to optimize the variable-specific-impulse gravity-assist low-thrust trajectories. Additionally, the modified logarithmic homotopy function is applied to serve as a gateway in variable-specific-impulse case. The algorithm for optimization multiple-gravity-assist trajectories is also presented in this paper. Moreover, the experimental data of NASA’s Evolutionary Xenon Thruster (NEXT) is employed in numerical simulations. Main-belt asteroids missions are given to substantiate the feasibility of the proposed methods.