Time-optimal three-dimensional trajectories for solar photon thruster spacecraft

The minimum-time trajectories of flat and solar photon thruster (SPT) solar sails for interplanetary mission were investigated using an indirect approach. The optimal control law for a SPT sail is very simple and extends the results found under the assumptions of coplanar, circular orbits to a three-dimensionali problem. SPT is more efficient and is likely to be heavier and more complex than flat sail. The results obtained for both sail models for Earth to Mars minimum-time transfer were compared and it shows that SPT offers performance improvements over conventional flat sails.