Analysis of Pulsed Plasma Thruster Plume Characteristics

Abstract

*† Pulsed Plasma Thrusters (PPTs) are ideal on-board propulsion systems for space missions that require very precise attitude control, such as station keeping and formation flying missions. However, there is still insufficient understanding about characteristics of the exhaust plume, and there is a concern that the exhaust plume could cloud solar panels and possibly harm other optical instruments. Successful modeling of the exhaust plume will help determine optimum locations of PPTs in a satellite, as well as help avoid clouding solar cells and harming optical instruments. In this work, the characteristics of the exhaust plume along the perpendicular plane to the electrodes are investigated. The Dawgstar mini-PPT that utilizes a solid Teflon (C 2F4) propellant is used. The PPT is rotated to different angles in order to measure different locations of the plume. Measurements are made at angles of 0 °, 10 °, 20 °, 30 °, -10 °, -20 °, and –30 ° ° ° °. An instrument that combines time of flight (TOF) and a gridded energy analyzer (GEA) is used. A 3.2 m drift tube, at the end of which is mounted the GEA, collimates traveling ion species from a thruster. A detector in the GEA provides velocity information, and electric potentials are applied on the grids of the GEA to discriminate selected ion species. The energy distribution of multi-component plume is incorporated with the velocity information and the mass to charge ratio of ion species to determine the plume characteristics. The result shows presence of C+, F+, F++, F2+ and CF+ in the plume. The centerline bulk velocity is found to be 23 km/s, and the ion temperature is 2.4eV. The plume characteristics at the other angles are presented on this paper. The comparison with previous experiments is discussed. Future work to determine characteristics of the plume along the horizontal plane to the electrodes is also discussed in this paper.