Exploration of an In-Situ Hall Thruster Erosion and Plasma Diagnostic Sensor

Hall-effect thrusters (HET) serve as primary propulsion for thousands of spacecraft, yet there is no architecture for directly assessing thruster health in orbit. The dominant mechanisms limiting thruster lifetime are discharge channel erosion in unshielded HETs and pole-cover erosion in magnetically shielded HETs. A fiber optic regression probe (FORP) embedded in either erosion region may be a promising diagnostic to provide in situ information on the state of health and remaining useful life of the thruster. However, the suitability of FORPs in HET applications has not been fully investigated. This work presents an exploratory benchtop investigation and calibration of a FORP operating in HET-relevant conditions, focusing on measuring sensing fiber attenuation across HET-relevant wavelengths (630–1083 nm). To emulate plasma-induced erosion, a FORP embedded into a boron nitride block was manually eroded with sandpaper. Over HET-relevant wavelengths (630–1083 nm), the average sensing attenuation was measured to be 4.4 ± 0.18 dB/cm and was insensitive to wavelength, distance, and incident optical power. Additionally, the FORP was found to resolve millimeter changes in material thickness. These preliminary results suggest that a FORP may provide a means to assess channel erosion and the remaining wear-lifetime of HETs in orbit