Film-Evaporation MEMS Tunable Array: Theory of Operation and Proof of Concept

Chemical micropropulsion options for small satellite systems (i.e. cube-sats, nano-sats, pico-sats) are currently limited by feed system complexity and viscous effects which dominate low Reynolds number flows, inhibiting efficient operation at low thrust levels. Electric propulsion offers high Isp but with high power/thrust demands and require power supplies which are bulky, complex, and expensive. The proposed Film-Evaporation MEMS Tunable Array (FEMTA), exploits the small scale surface tension effect in conjunction with temperature dependent vapor pressure to realize a thermal valving system for effective propulsion in the sub-milliNewton range with a thermal management option. The local vapor pressure is increased by resistive film heating until it exceeds meniscus surface tension strength in the nozzle inducing vacuum boiling which provides a stagnation pressure equal to vapor pressure at that point which is used for propulsion. The heat of vaporization is drawn from the bulk fluid and is replaced by either an integrated heater or waste heat from the vehicle providing a thermal control capability.