Two-stream efficiency model of the pulsed plasma thruster

Summary form only given. The Teflon/sup TM/ pulsed plasma thruster (PPT) is particularly well suited for propulsion of microspacecraft because of its simple inert fuel feed system and low power requirement. This paper discusses the thruster efficiency of a pulsed plasma thruster in terms of pulsed energy transfer, wall heat loss, frozen flow loss, velocity distribution loss, and exhaust beam divergence. The efficiency is described with the aid of a two-stream exhaust flow model, which assumes separate fast and slow particle streams, and invokes the Alfven critical velocity to evaluate efficiency in terms of measured parameters. The model is used to predict the differing performance of rectangular and coaxial PPTs, and shows good agreement with measured values. The model also indicates how thruster efficiency can be radically improved to values approaching 40% for specific impulse greater than 2000 seconds in the high current mode of operation.