A flight auxiliary propulsion system for velocity trim, station keeping, momentum adjustment for a spacecraft comprising rocket or reaction motors, also designated thrusters, utilizing thermally decomposable monopropellants such as hydrazine and other derivatives, thereof hydrogen peroxide, and isopropyl nitrate. The thrusters are arranged in a distribution or manifold system so that one set of thrusters provides for relatively large thrusts of force in the order of 1 to 5 pounds and another set of thrusters develop low thrusts in the millipound range. The large thrusts are developed by the catalytic decomposition of the monopropellant into a thrust chamber and through a throat and expansion nozzle to the ambient externally of the spacecraft. The low level thrusts are developed by heating catalytically or thermally decomposed monopropellant by electrical heating elements more commonly known as resisto-jet elements. Dual thrust levels may also be achieved by a common motor with a controllable resisto-jet and variable throat-area control.