Inter-electrode discharge of an ablative pulsed plasma thruster with asymmetric electrodes

Abstract

Ablative pulsed plasma thrusters (APPTs) are a form of propulsion that have been widely used in space tasks. In a recent study, an asymmetric segmented anode schematic was shown to be able to enhance the thrust performance of APPTs. To further understand the physical processes behind a segmented anode APPT, various research campaigns were carried out in this work: the discharge characteristics were studied, measurements were made of the total discharge resistance and inductance, and mapping was performed for the current density (along the side-view plane). From the discharge parameters and fitted total resistance and inductance profiles, we found a 10% lower discharge resistance for the segmented anode APPT compared with a normal anode APPT, which indicates a more optimized discharge process in the segmented anode APPT. The time-resolved current density maps offer two clear indications that verify the better performance of a segmented anode APPT. The first indication is the stronger current density on the surface of PTFE of the segmented anode during the main discharge, which shows that the segmented anode increases the discharge arc current density, which can then improve the ablation and ionization processes. The other indication is the more intense current density distribution between the electrodes during the follow-up discharge period (re-strikes) on the segmented anode APPT. This phenomenon implies that the segmented anode APPT may be able to better utilize the restrike energy in the propellant ionization process.