Experimental Evaluation of a Micro Liquid Pulsed Plasma Thruster Concept

Abstract

Researchers at The Johns Hopkins University Applied Physics Laboratory (APL) have developed a novel miniaturized pulsed plasma thruster (PPT) concept that utilizes a liquid propellant. Such devices could theoretically provide ultra-low dry mass, high specific impulse (Isp), flexible propellant options, and long-term reliability in a single package. Experimental devices have been designed and fabricated to help evaluate the concept. Typically, these devices have been powered by 0.5 1.0 μF capacitors at 200 700 V. Electrical discharge characteristics have been measured and peak currents have been estimated to be about 1.9 kA for a device powered by a 0.937 μF capacitor at 600 V. Impulse bit measurements have been facilitated by a custom-built thrust stand. The thrust stand was calibrated by dropping small nylon balls on the thruster and measuring the momentum transfer with a high speed camera. Impulse bits from a thruster powered by a 0.937 μF capacitor over a 200 700 V range were found to vary from 0.4 – 0.6 μN-s. Additional testing and analysis techniques are planned to quantify the propellant mass consumed per impulse bit. These and further experiments can be used to evaluate and improve microliquid PPT (MILIPULT) devices.