Near Minimum-Time Trajectories for Solar Sails

Abstract

SOLAR sailing has long been considered for a diverse range of future mission applications. As with other forms of low-thrust propulsion, trajectory optimization has been a focus of development activities. In particular, minimum-time solar-sail trajectories have been obtained by several authors for a range of mission applications. Almost all of these studies have used the Pontryagin principle of the calculus of variations to obtain minimum-time trajectories by the classical, indirect method (see, for example, Ref. 2). The indirect approach provides a continuous time history for the required solar sail steering angles. Only a few studies have used the competing direct approach, which recasts the task as a parameter optimization problem by discretizing the control variables. These studies have used many discrete segments for the sail steering angles to ensure a close approximation to the continuous steering angles provided by the indirect approach and hence a close approximation to the true minimum-time trajectory