Precision Microvalve for Green Propellants

ABSTRACT: Busek proposes to develop a flight-prototype piezo microvalve useful for micro chemical thrusters that require precisely metered flow rates. Deriving from a flight-qualified Busek microvalve and a successful proof-of-concept Phase I laboratory prototype, this proposed valve will be small, lightweight, and ready for flight qualification. It can linearly actuate thrust up to the 100 mN design point while consuming power as low as one milli-Watt. In parallel to the valve development, efficient power converter electronics will be developed to provide the voltage necessary to operate the piezo actuator. Though designed for highly viscous green monopropellants, the valve will be equally adequate for regulating most liquid and gaseous propellants. One unique feature includes an all-welded design that will accept inlet pressures over 500 psi. When coupled with a closed-loop control system, the valve can regulate flow with extreme precision while exhibiting no hysteresis. Upon completion of the successful Phase II development, Busek will deliver a flight-like microvalve and electronics that are fully characterized and tested for operation in a simulated space environment. Additional qualifications will include open/close cycling, vibration, and abbreviated life testing. BENEFIT: Many in the space industry desire to start phasing out hydrazine from monopropellant space propulsion systems due to its toxicity. Hydrazine is also a primary choice for micro chemical propulsions like ACS. Advanced green monopropellants, such as AF-315 and ADN, offer increased performance at much reduced toxicity. For green monopropellants to evolve into a major role in the space industry, they must be appropriate for ACS applications, and thus, a suitable feed system is essential. The proposed microvalve will attract attention from the U.S. Air Force and NASA who have shown great interest in adapting green monopropellants for future satellite main propulsion and ACS thrusters.