Discharge characteristics of two-stage micro-cathode arc MPD thrusters with a permanent magnet and a pulsed magnetic field

Abstract

Small, lightweight low-power micro-cathode arc thrusters (µCATs) with micronewton thrust are well suited to the altitude control of small satellites like CubeSats. For some applications (orbit raising, maneuvering) their thrust level needs to be improved. A possible approach for this could be the two-staged thruster—a micro-cathode thruster with a magnetoplasmadynamic (MPD) stage and an external magnetic field. In this article, we discuss some discharge features that such a two-stage µCAT-MPD experiences in each configuration of the magnetic field—formed with either a permanent magnet, or a pulsed magnetic coil. We found that in both configurations of the magnetic field, the thrust can be enhanced significantly (up to factor of 10) after some threshold voltage is applied to the second stage. The pulsed magnetic coil ensures better controllability of the magnetic field; however, it causes an undesirable time delay between the plasma generation moments in both stages, which consequently results in a moderate thrust increase. The permanent magnet provides a stable thrust increase; however, it cannot be switched off, which seems to be impractical for its use in micro-satellites. In both magnetic field configurations, the emissive electromagnetic noise level was found to be low-frequency (within tens of kHz) and quite moderate in amplitude, and mechanical noise was found to be two orders of magnitude lower than the thrust generated in the normal working regime.