Direct Approach for Computing Near-Optimal Low-Thrust Earth-Orbit Transfers

摘要

A new method for computing near-optimal, minimum-time Earth-orbit transfers for solar electric propulsion spacecraft has been developed. A direct optimization approach is utilized to solve the optimal control problem. The optimal thrust direction time history is computed by obtaining the optimal blend of three extremal feedback control laws. This approach is applied to long-duration orbit transfers, and the effects of Earth shadowing, oblateness, and solar cell degradation are included in the simulation. The optimal trajectories computed using the direct approach exhibit a very close match (within 1%) with the corresponding optimal trajectories obtained with a calculus of variations approach. The direct method also exhibits robust convergence properties and is insensitive to the initial guess of the optimization variables.