Operation of an auto‐initiated pulsed plasma thruster

Abstract

Purpose -The purpose of this paper is to develop and characterize a pulsed plasma thruster (PPT) that does not need a spark plug to initiate the plasma discharge. Design/methodology/approach -Two parallel rail thrusters were built and their performances were characterized inside a vacuum chamber to elucidate the effect of vacuum level and thruster geometry on the performance. The thruster electrical performance was quantified by measuring the voltage output from a Rogowski coil connected to the power supply. The thrust produced by the developed thruster was estimated by measuring the force exerted by the plume on a light weight pendulum, whose deflection was measured using a laser displacement sensor. Findings -The thruster can operate without a spark plug. In general, the performance parameters such as thrust, mass ablation, impulse bit, and specific impulse per discharge, would increase with increasing pressure levels up to an optimum level due to the increase in discharge energy as well as the decrease in the total impedance of the plasma discharge. The discharge frequency is function of the breakdown potential, the total resistance in the equivalent circuit, and the capacitance of the circuit. The total impedance of the circuit decreases with pressure level and hence the discharge energy increases. The thrust efficiency is found to be affected by the thruster geometry as well as the discharge energy.Research limitations/implications -The studies reported in this paper have been carried out at relatively higher pressure levels compared than prevail in space. However, it should be possible to extrapolate these results to the lower vacuum levels at which the performance is independent of the geometry. Practical implications -The results reported in this paper suggest a design guideline for auto-initiated PPT. Originality/value -If the spark plug is eliminated, the size of the thrusters can be reduced and arrays of such thrusters can be manufactured using micro electro mechanical systems techniques, which can provide tremendous control authority over the satellite positioning. Nomenclature¼ conversion factor for Isp between SI and imperial units (m/s 2 )¼ highest absolute Rogowski coil voltage peak (V) V2¼ second absolute Rogowski coil voltage peak (V) V, G(pd) ¼ discharge voltage, also the breakdown potential function (V) V o ¼ power supply output voltage (V) n ¼ velocity of pendulum during discharge (m/s) h ¼ thrust efficiency

Analysis of effective parameters on ablative PPT performance

“…However, there have been a few number of researches trying to experiment other methods of PPT discharge initiation. Kushari and Loh (2010) reported that they designed and developed an auto-initiating ablative PPT with PTFE as propellant that could operate without an igniter plug. Elimination of igniter plug can be of paramount importance in its miniaturization and the lifetime of the thruster.…”

Pulsed Plasma Thrusters

“…2 Japanese researchers have also engaged in such work obtaining fairly good current results at low electrode voltages. 15 • High Pressure: Kushari et al 26 suggested that high vacuum pressures catalize ignition through the air gap once a given voltage is reached. The breakdown clears the energy from the capactior until it recharges and self-ignites again allowing the pulsed behaviour desired.…”

“…Over the years propellant-feed mechanisms, chamber geometries, and energy levels have varied. Various attempts to improve performance have led teams to use gas, 7 liquid 23 propellants, laser 15 and/or high-pressure gas 26 ignition over the standard configurations. Unfortunately, thus far, a common classification scheme is non-existent.…”