A simple electric thruster based on ion charge exchange

Abstract

An electric thruster is presented that makes use of the properties of an asymmetric hollow cathode glow discharge that ejects a collimated plume of high velocity neutral atoms. Ions are accelerated electrostatically outwards from within the asymmetric hollow cathode and undergo charge exchange with the background gas resulting in energetic neutrals being ejected, thus producing thrust. This thruster is entirely self-contained allowing thrust generation and beam neutralization within the discharge. Doppler spectroscopy was used to determine the speed of atomic hydrogen in the plume and was found to produce a specific impulse greater than 3 × 104 s for applied voltages and powers of the order of 5 kV and 100 W, respectively. An estimate of the thrust of 1 mN for a power input in the order of 1 kW was obtained from previously measured ion densities in similar discharges. This work builds on recent work associated with the ejection of high velocity neutrals from hollow cathode discharges. The simple but effective design of the thruster has the potential for large thrust densities as well as successful long term operation.