Advanced Diagnostics for Millimeter-Scale Micro Pulsed Plasma Thrusters

摘要

A class of Micro-Pulsed Plasma Thrusters (MicroPPTs) is being developed by the Air Force Research Laboratory (AFRL) to provide precise attitude control and stationkeeping ability to 25-kg class satellites. Operating by means of a surface discharge across a Teflon(TM) propellant fuel bar only a few millimeters in diameter, the MicroPPT delivers a thrust-to-power ratio of 5 - 10 microN-s/J. Due to the low pulse energy and size, the MicroPPT produces a spatially-confined and diffuse plasma plume that is difficult to analyze with material probes. Efforts to characterize MicroPPT plume are underway. To this end, a Herriott Cell interferometer is introduced to establish the plume electron and neutral densities. Comparison of the measured electron density with modeling predictions shows close agreement. Additionally, a Pockels cell has been developed to provide a zero-impedance MicroPPT breakdown voltage measurement. Current research focuses on an infrared-emission measurement capability to determine propellant surface temperature during thruster operation.