Controlled Solar Sail Transfers to Near-Sun Orbits with Restrictions on Sail Temperature

We present results of numerical simulations of local-optimal trajectories of a space probe with a flat solar sail which moves from a circular Earth orbit to near-Sun regions. We examine the planar (ecliptic) and three-dimensional transfer cases. We consider the upper limit of the sail temperature as the basic restriction. The local-optimal control law of the sail orientation angle was chosen in such a way that the rate of decrease of the orbital focal parameter reaches its maximal value. In the three-dimensional case, the requirement of the maximization of the orbital plane rotation rate was added. We also investigated complex control modes of the sail orientation for near-Sun orbits and of some “falling onto the Sun” trajectories. These computer simulations allow us to examine the durations of some sail missions and to investigate the evolution of osculating elliptical orbits.