DESIGN AND PERFORMANCE OF A 110 N ATTITUDE CONTROL THRUSTER FOR LUNAR MISSIONS

The design and development of an attitude control thruster, designated A110, developed for broad attitude control applications, including lunar landers, is described. The A110 thruster produces 110 N (25 lbf) of nominal thrust and in-excess of 305.5 s of specific impulse (I_sp) while operating on a fuel blend of 20% monomethylhydrazine-80% hydrazine (M20) with mixed oxides of nitrogen containing 3% nitric oxide (MON3) as the oxidizer. The injector and combustion chamber are additively manufactured with cobalt-chrome and niobium C103, respectively, to enable the rapid development required of the industry. The thruster is capable of response times of under 10 ms and currently produces a minimum impulse bit (MIB) of 0.436 N.s and has demonstrated operation in pulse-mode with a variety of duty cycles during development testing. These capabilities allow for the generation of precise pulses for accurate control of a lander. The testing of this thruster is used to evaluate steady-state and pulse-mode specific impulse, impulse repeatability, and combustion stability. The measured performance (i.e., specific impulse and characteristic velocity (C*), are compared with theoretical values. The capabilities demonstrated by the A110 thruster are applicable to a wide range of lunar lander missions and can be qualified for minor changes in thruster requirements for additional missions without the need for major design changes. This article is published with the permission of the authors granted to 3AF – Association Aéronautique et Astronautique de France (www.3AF.fr) organizer of the Space Propulsion International Conference.