Capillary Discharge Based Pulsed Plasma Thrusters (Preprint)

Abstract

Abstract : Although pulsed plasma thrusters have significant experimental heritage over a range of power levels, more recently they are often described as attractive low-power thrusters due to their small dimensions, simplicity, and ability to provide high specific impulses at low power levels. This paper, however, discusses research into the potential application of an electrothermal capillary discharge as a pulsed plasma generator useful in high-power spacecraft propulsion. A 0D transient physical model of the capillary discharge was constructed and used to characterize the operational envelope of the capillary discharge. Fundamental experimental investigations were also conducted to demonstrate the performance of the polyethylene capillary discharge over a range of energy/shot levels (500-1500J), capillary lengths (4cm-10cm), and LRC circuit inductances. The experimentally measured parameters (voltage difference, current, ablated mass, plasma temperature, and electron number density) typically agreed with the model predicted values to within 20%. Thruster relevant performance calculations were made using the validated model and showed that even without nozzle expansion the capillary discharge can operate as an efficient (30-40%) source of high-pressure (>100 atm) plasma for use in spacecraft propulsion systems.