Technique for escape from geosynchronous transfer orbit using a solar sail

A technique for escaping the Earth using a solar sail is developed and numerically simulated. The spacecraft is initially in a geosynchronous transfer orbit (GTO). A sail force control algorithm is derived that continuously orients the sail in three dimensions to maximize the component of sail force along the velocity vector. This approach maximizes the instantaneous rate of increase of the total orbital energy. Trajectories using this strategy are not necessarily minimum-time solutions, but independent analysis has shown that for the realistic order of magnitude of sail acceleration considered here, the solutions obtained are near-minimum-time trajectories. The equations of motion for the trajectory are expressed in modified equinoctial orbital elements, which are well behaved as the trajectory goes from elliptic to hyperbolic during escape. In this preliminary study a spherical gravity model for the Earth is assumed. The gravitational perturbation of the sun is included but atmospheric drag and shadowing effects of the Earth are neglected. No sail angle, sail angle rate, or minimum perigee radius constraints are included. Numerical results confirm that escape does occur, with the escape time highly dependent on the sail acceleration magnitude but relatively independent of the time of year of the deployment.