Design, Fabrication, and Test of a Microelectromechanical-System-Based Millinewton-Level Hydrazine Thruster

T HE miniaturization of space systems, such as microsatellites, has become an important development trend. Using a cluster of microspacecraft with a constellational architecture to replace a traditional spacecraft can greatly reduce the costs of production and launch, increase flexibility, and disperse the risks of a mission. Miniaturized spacecraft are classified based on mass, power, and dimensions. Spacecraft with amass of less than 20 kg are classified as class I microspacecraft [1] and require millinewton-level thrusts for spacecraft control. For microspacecraft, the onboard thrusters must be extremely small and lightweight; microelectromechanical systems (MEMS) are thus employed in microthruster design and fabrication [2]. A number ofmicropropulsion systems have been proposed.Micro cold-gas systems have been constructed and used in practice [3,4]; however, a rather low specific impulse (60–80 s) limits their usage. Micro electric-type thrusters provide a high specific impulse [5], but the requirement of high power for operation limits them to larger spacecraft. Miniaturized solid-propellant thrusters have a simple structure and a high specific impulse [6], but their relatively high thrust level (10–10 mN) and single use restrict their application. Monopropellant thrusters are appropriate for miniaturization due to their simplicity and acceptable working temperatures [7]. The catalytic reaction of monopropellant systems mitigates the constraints of radical quenching and mixing prohibition found in the microcombustion of bipropellant systems. Although hydrogen peroxide/silver systems have been tested and effectively reacted in microreactors, hydrazine is considered a better monopropellant for actual microthruster design and operation [7]. A millinewton hydrazine (N2H4) monopropellant thruster is presented in this work. MEMS technologies are employed in the design. The design considerations and component fabrication are discussed. The vacuum thrust of the designed thruster was measured and its propulsive performance was analyzed.