Abstract: Selective reconfiguration of existing spacecraft on-board control and propulsion equipment is provided. The modification combines add-on switch means such as solid state multiplexers or relay banks and rate sensing gyros with existing accelerometers, propulsion control electronics and thrusters. The switch means reconfigure the input circuits and the output circuits of the propulsion control electronics. The switch means select the rate sensing gyro and the liquid apogee motors for control of spacecraft spin axis coning during perigee solid rocket motor firing, and reselects the accelerometer and reaction control thrusters for on-orbit nutation control.