The pocket rocket electro-thermal plasma thruster for 'CubeSat' nano-satellites

Abstract

In the miniaturised Pocket Rocket thruster, a radiofrequency plasma is employed to heat the gas via charge exchange collisions and ambipolar flow to create a form of electrothermal thruster which has its heating mechanism in the centre of the flowing propellant rather than on the thermally lossy walls. The radiofrequency generates a highdensity plasma at about 1 Torr having a volume less than 1 millilitre and its characteristics operate in a linear power regime where measured thrust (~1 mN) and specific impulse (~100 s) performances can now be successfully simulated using computer fluid dynamics codes. Miniaturised power and propellant sub-systems totaling a few hundred grams in weight for a few Watts have been developed for Pocket Rocket for integration within a 1/2 U (1 U = 10 cm x 10 cm x 10 cm) CubeSat. This proof of concept aims at getting flight heritage and is a stepping stone towards the development of higher power systems since the radio-frequency power sub-system can be scaled up to a few kWatts and drive the electrode-less neutraliser-free Helicon plasma thruster.