Precision Microvalve for Green Propellants

Busek Co. Inc. proposes to develop a piezo-actuated, precision microvalve for metering extremely low flow rates typical of chemical micropropulsion.  Existing microvalves offer no flow regulation and consume several watts due to their electromagnetic coil actuation while the piezo actuator consumes few mW.  For micro and nano spacecraft which have of the order of 10W on-board, power consumption is crucial and low power valves are enabling.  The proposed microvalve will maintain a set-point flow with 100:1 resolution.  An active feedback system using a calibrated orifice will be incorporated thus eliminating actuator hysteresis and thermal drifts.  Derived from highly successful and flight-qualified Busek product, the proposed microvalve will be small, light weight, and specifically designed to accommodate highly viscous green monopropellants.  Other propellants can be accommodated because the valve body is universal requiring only an orifice change to operate with other fluids or broader range.  The entire flow passage is welded offering high pressure rating making it also suitable for on/off service at the exit port of a propellant tank.  In Phase 1 an advanced prototype of the microvalve will be constructed and tested.  An EM model suitable for flight qualification will be developed in Phase 2 and delivered to AFRL. BENEFITS: The proposed microvalve will enable new micro propulsion systems for micro and nanosats that can not be realized at present because of the absence of suitable low power valves.  Hydrazine has been phasing out from monopropellant space propulsion systems due to its toxicity. However, it is still a primary choice for micro chemical propulsions like ACS.  For green monopropellants such as AF-315 and ADN to evolve into a major role in ACS applications, a suitable feed system is essential.  The proposed microvalve will attract attentions from NASA and U.S. Air Force who have shown great interest in adapting green monopropellants for future ACS thrusters and satellite propulsion.