Indium FEEP Endurance Test: Preliminary Results

Three endurance tests have been carried out in order to investigate the long-term behavior of Indium FEEP microthrusters. The thruster tested is based on the Indium Liquid Metal Ion Source (LMIS), space-proven in a number of scientific satellites up to a thrust of 5 µN, developed by the Austrian Research Centers (ARC). The first endurance test was performed at a thrust of about 17 µN consistent with requirements for missions such as SMART2, LISA, DARWIN and TPF. It lasted 820 hours at a mean mass efficiency of 45%, an extractor current of less than 1 µA and no spraks. Two more tests were run using profiles from 0-35 µN (plus calibration periods up to 60 µN) and 0-25 µN lasting for 460 and 470 hours respectively. In addition, a lifetime prediction model was developed and experimentally verified to estimate the behavior of microdroplet deposition on the extractor electrode.