96 kN-sec Endurance Test of the R-200 Low Power Hall Thruster

The R-200 low power Hall thruster unit passed a 96 kNs endurance test in which it operated at one operating point of 250 W (275 V) while anode mass flow rate adjusted over time to maintain constant power. 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. Throughout the endurance test performance was characterized 5 times in the 100-250 W discharge power range, 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 (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 sec at the beginning of life to 1,160 sec at the end of test. Performance degradation of less than 10% was spotted at all operating points in the 100-250 W discharge power range throughout the experiment. The ignition test validated 300 successful thruster ignition cycles. Using channel profile geometry data a simple semi-empirical erosion model was constructed to predict possible breaching points and allow for an improved future 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.