Optimal solar sail orbit transfers to synchronous orbits

The recent development of a strong, lightweight, thin-member substrate may provide the technological breakthrough that will enable heliocentric solar sailing missions. The missions considered in this paper used solar sails to transfer to a heliocentric circular orbit and then to apply a constant outward radial thrust acceleration. This radial acceleration allows the spacecraft to have a larger period than the Keplerian period at that radius. Heliocentric circular orbits are designed to match the orbital period of Earth or Mars and these designed orbits are termed synchronous orbits. Optimal control theory is applied to determine minimum-time solar sail orbit transfers for a range of Earth and Mars synchronous orbits and several numerical results are presented.