Time-optimal Control of Axi-symmetric Rigid Spacecraft

In this paper, we consider the minimum-time reorientation problem of an axi-symmetric rigid spacecraft with two independent control torques mounted perpendicular to the spacecraft symmetry axis. The spacecraft is allowed to spin about its symmetry axis. All possible control structures, including both singular and nonsingular arcs, are studied completely by deriving the corresponding formulae, and the necessary optimality conditions. An efficient method for solving the optimal control problem numerically, based on a cascaded computational scheme, is also presented. Numerical examples demonstrate optimal reorientation maneuvers with both nonsingular and singular subarcs.