Demonstration of 13,011-h of operation of a proto-flight compact heaterless lanthanum hexaboride hollow cathode

As part of the flight qualification of the Hall thruster component of the Ascendant Sub-kW Transcelestial Electric Propulsion System (ASTRAEUS), the thruster's proto-flight compact heaterless lanthanum hexaboride hollow cathode was subjected to a long-duration wear test. The cathode was mounted in an ASTRAEUS Hall thruster simulator for the test, which provided a flight-like mechanical, thermal, and magnetic environment for the cathode. The ASTRAEUS cathode was successfully operated for 13,011 h at a discharge current of 4 A using xenon propellant, with a total of 1653 ignitions performed throughout the test. The cathode's discharge voltage and keeper floating potential were 23.3 V ± 1 V and 3.9 V ± 1 V, respectively, during nominal operation of the device, indicating stable operation that did not change or degrade over the entire duration of the test. Cathode characterizations performed periodically throughout the test, where the cathode was operated at different conditions from the nominal 4 A discharge current, showed that the cathode performance was virtually invariant with operation time. The test was voluntarily terminated due to programmatic constraints. An intermittent keeper-to-cathode short was observed during the test, which was traced to an issue with the weld schedule of the cathode's internal heat shield that allowed slight contact to occasionally develop. The intermittent short was able to be cleared using the existing capabilities of the ASTRAEUS power processing unit, did not prevent ignition of the cathode, and showed no detrimental effects to cathode performance during steady state operation. This test marks the world's first 10,000+ h flight qualification test of a compact heaterless lanthanum hexaboride hollow cathode to be used with a low-power magnetically shielded Hall thruster.