Ion electrospray for efficient propulsion of microspacecraft

Electrosprays make use of strong electric fields to extract streams of charged particles from conductive liquids most of the time held at the tip of a sharp emitter electrode over which a Taylor cone forms. The technique has been widely used in analytical chemistry as a means of obtaining intact macromolecules. Ionic liquid ion sources (ILIS) are a subclass of electrosprays capable of emitting ion beams directly from a non-volatile room-temperature molten salt (also known as an ionic liquid) with no intervening droplets. By leveraging these results with MEMS manufacturing of ILIS emitter arrays, it should be possible to obtain large current densities suitable for high-throughput applications, such as etching of wafers at increased rates and for efficient propulsion of small spacecraft.

Researchers in the Space Propulsion Laboratory (SPL) at the Massachusetts Institute of Technology (MIT) have been focused in recent years on the practical implementation of ILIS for propulsion. Small satellites currently do not have access to efficient, miniature propulsion that is free of pressurized tanks and/or volatile propellants, as is often required by launch providers, even though they are becoming increasingly capable in nearly every other regard. These smaller platforms hold much promise, especially in applications such as disaster monitoring and response.

The current status and technological challenges of the reduction to practice of ILIS for small satellite propulsion are presented, accompanied by a brief survey of specific applications/maneuvers enabled by such a technology. A critical challenge—electrical discharges between the high-voltage electrodes—is discussed, and potential mitigation techniques are introduced. Lastly, the status of commercialization of the technology is presented.