Three DOF Optimal Thrusters Selection and Modulation for Space Vehicles

In reaction control thrusters (RCT) propulsed space vehicles the force and/or torque derived from the control law must be translated into thrusters selection and thrusters firing durations. This has often to be done in an optimal way with respect to propellant consumption. Classical catalogue approaches to perform that rely on RCT architectural geometry symmetry properties. When such symmetries are not present at all, use of algorithms such as the linear programming “simplex” one has been advocated. But it presents some risks because the computation duration is not deterministic and no converged solution is granted in a predetermined duration. In-house studies performed at EADS Space Transportation found an optimal catalogue solution for the six DOF (degrees of freedom) problem. This algorithm has been developed for the ATV (Automated Transfer Vehicle) spacecraft. It is based on a precomputed optimal catalogue that is used onboard. However this catalogue depends on the centre of mass and this feature prevents its direct use in the pure attitude control problem. Here it is proposed an adaptation of the 6 DOF optimal catalogue to cope with 3 DOF problems and present some results