Facility Effects on Ion Flux Measurements of the Radiofrequency Ion Thruster 10 cm (RIT-10)

Abstract

Electric propulsion is an alternative means for spacecraft to execute orbital maneuvers and provide attitude control in space. Electric propulsion devices generate thrust by electrically converting a neutral gas into a plasma and accelerating the heavy ions through an electric field. The performance of these devices is characterized in vacuum test facilities that can appropriately simulate the space environment and accommodate the plasma plume generated by the thruster. Understanding the facility effects on ion flux pathways from the plasma to its surroundings is critical in characterizing potential thruster-spacecraft interactions. The ion charge density profile of the 1.35 kW radiofrequency ion thruster 10 cm, RIT-10, was captured at the Justus-Liebig University JUMBO test facility. The vacuum chamber maintained high-vacuum levels in the 1x10E-6 Torr range using three turbomolecular pumps and an array of 8 cryopumps. The RIT-10 operating condition was held constant at 2 sccm Xe, 80 mA beam current, 1000 V screen grid bias, and -150 V acceleration grid bias with respect to chamber ground. The vacuum pumping configuration was changed by maintaining all three turbomolecular pumps operational while toggling on different sets of cryopumps. At each pumping configuration, Faraday probe scans across the RIT-10 exhaust plume collected ion flux measurements at 74 cm downstream from the thruster exit plane. The ion charge density profiles captured during the various pumping configurations are compared with the baseline scan. The results and their implications in characterizing facility effects on ion charge density and beam divergence angle of the RIT-10 are discussed on this poster.