Date of Award

6-2025

Degree Name

Master of Science in Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Kristina M. Lemmer Ph.D.

Second Advisor

Nicholas Taylor, Ph.D.

Third Advisor

Mike McDonald, Ph.D.

Keywords

Aerospace, electric propulsion, electrospray

Access Setting

Masters Thesis-Open Access

Abstract

In this thesis, a single-emitter porous electrospray thruster was tested at nine different extractor electrode positions. The nine positions were: center, four slightly offset in each cardinal direction, and four significantly offset in each cardinal direction. Slightly offset was defined as ~25% of the distance from the center to the edge of the extractor orifice (~125 ± 2 μm) and significantly offset was defined as ~60% of the distance from the center to the edge of the extractor orifice (~302 ± 2 μm). Three diagnostic measurements were recorded to determine the effect of the extractor electrode position on thruster operation: emitter current, extractor current, and Computed Tomography (CT) scans. The current-voltage (I-V) characteristics for the emitter and extractor current were measured from 0 V to at least 1900 V, with the centered extractor position reaching 2400 V. The ending voltage was decided based on the percentage of the emitter current intercepted by the extractor. The emitter I-V characteristics for the slightly offset positions showed no significant difference from that obtained when the extractor was in the center position while the significantly offset positions showed earlier onset voltages but no significant difference in slope of the I-V characteristic. The discontinuities in current observed on the emitter I-V characteristics can be directly correlated with the formation of emission sites as observed in the CT scans measured at those corresponding potentials. The extractor I-V characteristic for the slightly offset positions were similar to the center position characteristic, with the percent of intercepted current having a steeper slope vs. voltage for some positions. The extractor I-V characteristics for the significantly offset positions all saw current to the extractor at earlier potentials, had significantly steeper slopes than the center position, and saw large increases in intercepted current percentage vs. voltage.

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