Thrust Vector Control of Solar Sail Spacecraft

Abstract

This paper presents a comprehensive mathematical formulation of the thrust vector control (TVC) design problem of solar sail spacecraft. A TVC system is part of an attitude and orbit control system (AOCS) of a sailcraft, and it maintains the proper orientation of its solar sail to provide the desired thrust vector pointing. The solar pressure thrust vector direction of a sailcraft is often described by its cone and clock angles with respect to a particular orbital reference frame. This paper describes various forms of orbital trajectory equations, which employ two different sets of the cone and clock angles, for the design and simulation of solar sail TVC system. In particular, a quaternion-based TVC/AOCS architecture is proposed for solar sailing missions because of its simple interface with the TVC steering commands of the desired cone and clock angles. In practice, any sailcraft TVC system will require frequent updates of both orbital parameters and TVC steering commands for frequent trajectory corrections because of the inherent difficulty to precisely model the solar radiation pressure and to accurately point the true thrust vector direction. The frequency of orbit determination update and TVC command update is mission-dependent; it is determined by many factors such as the trajectory dispersions, the target-body ephemeris uncertainty, and the operational constraints.