MDL News & Trends
Microfluidic Electrospray Propulsion May Allow Microspacecraft to Fly to Mars or the Asteroid Belt
Small spacecraft currently under development in the 3- to 50-kilogram mass range have very limited delta-V capability. Microfluidic electrospray propulsion (MEP) technology, currently under development at JPL, may one day enable delta-Vs of thousands of meters/second and the precision pointing of small spacecraft for planetary missions and missions to explore asteroids. The scalable, highly integrated MEP assembly has a dry mass less than 10 grams and is under development for 20–100 micronewtons of thrust. Its technology comprises an electrospray thruster with microfabricated components that include a silicon chip etched with micron-scale electrospray needles, heater chip, extraction electrode chip, and propellant reservoir. The propellant, indium metal, is stored as a solid and then heated to melt, flow, and spray. The feed system has no pressurized reservoir or valves. Instead, the propellant is capillary force driven from the reservoir, through the emitter array chip and to the tip of the emitters. High-electric fields applied between the emitters and the extractor electrode accelerate the indium charged particles to create thrust.
In 2013, MDL continued to refine fabrication techniques for the components of the MEP thruster. The process under development for creating the emitter array chips includes a grayscale lithography for 3D-micro rapid prototyping of complex silicon needle configurations with micron-scale precision. MDL also fabricated MEP thruster pyrex heater chips and silicon extraction grid chips. They were tested with the emitter array chips in the MEP thruster prototype assembly in the Microthrust Propulsion Laboratory (MPL) with over 10 hours of continuous operation. Technology development now continues to improving emitter needle array fabrication uniformity, and integration of axial grooves to support the capillary force driven flow of indium from a propellant reservoir through the emitter chip and to the tips of the emitter needles.