Optimal-fuel, low-thrust Earth-Ivar transfer trajectories with Venus gravity assist

In this paper, fuel-optimal low-thrust trajectory with Venus gravity-assist is presented for exploring Ivar asteroid. The problem formulation treats the spacecraft mass as a state variable, thus coupling the spacecraft design to the trajectory optimization. To avoid numerical sensitivity, the equinoctial elements are utilized to describe spacecraft motion, and the optimization problem is divided into three subproblems, the solution of the last subproblem is taken as the primary guess for the next one. A hybrid optimization method is utilized to solve them, which method utilizes the costate time histories to parameterize the thrust steering angles time histories. Numerical results are presented for the optimal three-dimensional Earth-Ivar with Venus gravity-assist trajectory.