96 kN-sec endurance test of the R-200 low power hall thruster

Abstract

The R-200 low power Hall thruster unit completed a 96 kNs endurance test, during which the anode mass flow rate was adjusted to maintain a constant power of 250 W throughout the campaign. The test was performed at Rafael, while the initial performance validation was conducted at ESTEC. At the end of the endurance test the thruster exhibited nearly unchanged performance and did not reach its end-of-life. During the endurance test, the thruster performance was characterized 5 times in the 100–250 W discharge power range, the ceramic channel profile was measured 6 times to assess the erosion rate, thrust was continuously tracked multiple times a day, an ignition test was conducted after 60 kNs to assess continuous operation impact on ignition capability, and sensitivity to magnetic field changes was checked twice (at 12 kNs and 65 kNs). Two notable events occurred during the test – a cathode keeper breach and a ceramic channel breach. The keeper electrode was replaced, and cathode position adjusted. following the ceramic channel breach the thruster continued to operate regularly, and with no performance degradation, even after the inner pole was exposed to the plasma discharge. The thruster generated a constant thrust of 13 mN throughout the entire test while the Isp decreased from 1,250 s at the beginning of life to 1,160 s at the end of test. Performance degradation of less than 10% was measured at all operating points in the 100–250 W discharge power range at the end of the experiment. The ignition test validated 300 successful thruster ignition cycles. Using channel profile geometry data, a simple semi-empirical erosion model was calibrated to predict future breaching events and allow for an improved channel design. The information gathered during this endurance test campaign was used to redesign the cathode keeper and inner ceramic channel profile. A subsequent test of the improved thruster unit design showed an expected lifetime of over 200 kNs.