Proof-of-Concept In-Situ Diagnostic for Magnetically Shielded Hall Thruster Erosion

Abstract

Validating flight-ready hardware for magnetically shielded Hall thrusters is criticallydependent on lifetime testing. Traditionally, measuring the erosion of the inner pole requires breaking vacuum, a process that can influence test results, and typically allow for erosion measurements only after extensive durations. A proof-of-concept in-situ erosion diagnostic is explored to assess its feasibility for more accelerated testing. The diagnostic operates by using a conductive material, specifically ITO-coated glass, and tracking the change in its electrical resistance over time. This change in resistance is directly correlated to the material’s erosion rate. Testing was conducted under three different operating conditions: 200V, 250V, and 300V in the plume of a magnetically shielded Hall thruster along it’s centerline. Theoretical results were also shown for the probe’s behavior at the inner pole. The results demonstrated that the resistance change exhibited an inverse trend, in line with theoretical expectations, and the probe was capable of detecting resistance changes as low as 0.05 Ω/s in the plume and theoretical resolution of 0.04 Ω/s at the inner pole. Looking ahead, future improvements will focus on mitigating thermal variations and employing more robust materials that erode more slowly, enhancing the diagnostic’s durability and accuracy at the inner pole. The successful implementation of this approach — placing a conductor in plasma and measuring its resistance as it erodes — paves the way for the development of in-situ erosion sensors for accelerated Hall thruster lifetime testing.