Reaction Sphere Actuator*

The reaction sphere actuator (RSA) described in the paper is a novel device for satellite attitude control. It consists of a sphere, an actuation system, made out of holonomic wheels, and an outer encapsulating shell. Reaction torques are obtained by adequate rotation of the sphere. The mechanical rolling contact between the actuation system and the sphere also ensures the sphere static equilibrium and the transfer of the reaction torque to the encapsulating shell. RSA reaction torques can be generated along any rotational axis. This paper starts by discussing the controllability of the system, which amounts to a feasibility of the concept, goes over the actuation system, basic control strategy and simulation results. Finally a performance analysis comparison between a RSA and an equivalent reaction wheel arrangement is presented.