Methods and apparatus are provided for reaction wheel (RW) assemblies for spacecraft. The apparatus comprises a M/G coupled to an inertia wheel and a controller coupled to the M/G that, in response to commands it receives, couples power to or from an M/G of another RW assembly over a shared transfer connection (V.sub.XFR), so that one M/G acts as a generator powering another M/G acting as a motor. The controller compares generator voltage V.sub.GEN to the BEMF of the motor on V.sub.XFR and reconfigures a multi-winding M/G or steps-up the generated voltage to maintain V.sub.GEN>V.sub.XFR to maximize direct energy transfer from one RW to the other as long as possible. When V.sub.GEN declines sufficiently, the controller can couple the motor to the spacecraft power bus and/or the generator to a power dump so as to continue to provide the commanded torque if needed. Operation is automatic.