Minimum fuel trajectories for low-thrust spacecraft with radiation exposure constraints

This study investigated the multiobjective optimization of low-thrust spacecraft. An empirical optimization was performed to characterize the tradeoffs of fuel consumption, manoeuvre time and radiation exposure. A calculus of variations approach was also taken to perform a more mathematically rigorous optimization under the guise of optimal control theory. The empirical study demonstrated that larger burn lengths, while decreasing manoeuvre time and radiation exposure, also resulted in a dramatic increase in fuel requirements. The modern control theory optimization was less successful as converged solutions were obtained for simple multirevolution orbit raisings when considering only minimum fuel constraints. The addition of radiation considerations in the minimization resulted in some trajectory adjustments that reduced radiation exposure but in general only increased the instability of the system. The method was found to be too sensitive to the system dynamics and poor initial guesses to make the algorithm feasible in solving practical problems.