Preliminary design of earth-mars cyclers using solar sails

Abstract

Motivated by the concept of using cycler trajectories for Mars return missions, an optimal Earth–Mars cycler is designed for spacecraft that use solar sails. The design is preliminary in the sense that the trajectories are assumed to be coplanar and the orbits of Earth and Mars are assumed to be circular. The optimality criterion is the vehicle’s hyperbolic excess speed V∞ with respect to Mars. This trajectory optimization problem is formulated using the framework of optimal periodic control with interior point constraints that include jump discontinuities that arise as a result of gravity assists. The problem is numerically solved using the concept of pseudospectral knots (PSK) by way of a general-purpose dynamic optimization software. Feasibility of the PSK-derived trajectories is demonstrated using numerical propagation. Results show that solar sails can be used to reduce significantly V∞ at Mars. For example, it is shown that a sail with a lightness number of 0.17 can achieve a V∞ with respect to Mars of 2.5 km/s at every synodic encounter.