Optimisation of solar sail interplanetary heteroclinic connections

This paper investigates time-optimal solar sail trajectories between displaced Libration Point Orbits (LPOs) of different circular restricted three-body systems. Key in the investigations is the search for transfers that require little steering ef-fort to enable the transfers with low control authority solar sail-like devices such as SpaceChips. Two transfers are considered: 1) from an Earth-L2 Halo orbit to a Mars-L1 Halo orbit and 2) from an Earth-L1 Halo orbit to a Mercury-L2 Halo or-bit. For both transfers the optimal control problem is derived and solved with a direct pseudospectral method. For a sail performance comparable to that of NASA’s Sunjammer sail, the results show transfers that require very little steer-ing effort: the sail acceleration vector can be bounded to a cone with a half angle of 5 deg (Earth-Mars) or even 2.5 deg (Earth-Mercury). These transfers can serve a range of novel solar sail applications covering the entire spectrum of sail length-scales: micro-sized SpaceChips could establish a continuous Earth-Mars communication link, a traditional-sized sail provides opportunities for in-situ observations of Mercury and a future kilometer-sized sail could create an Earth-Mars cargo transport gateway for human exploration of Mars.