Characterization of a liquid-propellant pulsed plasma thruster using various nozzle configurations

Abstract

Liquid-propellant pulsed plasma thrusters (LP-PPTs) perform better than conventional solid-propellant (typically PTFE) PPTs because the use of an LP can eliminate the problems of late-time ablation and particulate emission associated with solid propellants. In the present study, the performance and characteristics of a prototype LP-PPT are investigated using a range of nozzle and electrode configurations. Two types of conical nozzles were tested: a ceramic nozzle with an annular anode placed at the nozzle tip and a monolithic-anode nozzle made of stainless steel. The area ratio ¾, divergent angle ª, and cavity length L of the ceramic nozzle were varied from 10 to 30, 10° to 40°, and 5 to 20 mm, respectively. Ethanol was used as the propellant. The thrust measurements showed that the LP-PPT prototype demonstrated superior performance when it was fitted with the embedded annular anode ceramic nozzle than when it was fitted with the monolithic-anode nozzle. Among all of the tested nozzle configurations, the highest performance was observed for a ceramic nozzle with ¾ = 30, ª = 20°, and L = 10 mm, which yielded an impulse bit of 167 µNs, a specific impulse of 1,150 s, a thrust efficiency of 5.9%, and a thrust–power ratio of 11 µNs/J at a capacitor-stored energy of 14 J and a propellant mass shot of 14.8 µg.