Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Carl Hartsfield, PhD.


Hall thrusters are a key technology for current and future unmanned satellites, striking a balance between thrust and fuel economy suitable for many mission profiles of interest. Despite their extensive flight heritage and a large body of research, many phenomena occurring in the plasma discharge of Hall thrusters are not well understood. A combination of intrusive and non-intrusive measurement techniques were used to investigate the properties of the exhaust plume of two Hall thrusters and correlate optical characteristics of oscillating modes with the plasma potential and azimuthal current distribution during those modes. A strong trend was found associating the optical emission of spokes with a local increase in plasma potential as measured by an emissive probe, indicating a spoke structure with visible and non-visible regions. Additionally, a consistent phase delay was observed between oscillations in discharge current and Hall current during the breathing mode. A similar delay was not observed between discharge current and optical emission or plasma potential oscillations during the breathing mode. These trends were used to infer a possible plasma structure during breathing and spoke modes.

AFIT Designator


DTIC Accession Number