Progress Towards a Miniaturized Electrospray Thruster for Propulsion of Small Spacecraft

Miniaturized electrical thrusters based on electrospray (or colloid) emitters could rev- olutionize the spacecraft industry by providing efficient propulsion capabilities to micro and nano satellites (1-100 kg). We report on our recent advances in the development of this technology within the MicroThrust ( European consortium. We present the design and operation of the currently fabricated and next generation emitter arrays, describing their microfabrication process and measured performance. The emitters are out-of-plane internally fed capillaries micromachined in monolithic silicon. They are 100 µm tall and have an inner diameter of 5-10 µm. We operate the devices in both unipolar and bi-polar modes and find that the latest devices operate in a mixed regime, with the emitted spray a composition of ions and droplets. Their specific impulse is consequently in the few hundred seconds, highlighting the need for higher impedance, smaller emitters. Onset voltages are of than 800-850V for 200 µm inner diameter extractors, current levels for 19 emitter arrays of 2-3 µA. Preliminary analysis hints to plume half-angles of 35-40◦, although these values depend on the operation mode and beam composition.

Presented at:
48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Atlanta, Georgia, USA, July 30 - August 1, 2012

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