Student Name: William Brabston
Advisor: Dr. Mitchell Walker
Milestone: PhD Thesis Final Examination (Defense)
Degree Program: Aerospace Engineering
Title: Analysis of the Ionization Mechanisms of an N2/O2 Air Mixture in a Hall Effect Thruster
Abstract: There is a growing interest for satellites to access very low Earth orbit (VLEO); however, VLEO is currently prohibitive due to its high atmospheric density imposing a strong drag force on satellites. This drag force is life-limiting to the satellites as it rapidly depletes on-board propellant, typically xenon or krypton, used in a Hall effect thruster (HET) to counter the drag and maintain the VLEO orbit. Air-breathing electric propulsion (ABEP), consisting of the collection and subsequent ionization and acceleration of atmospheric air in a HET, offers a potential solution to enable long-term access to VLEO by providing an indefinite propellant supply. The electron-impact ionization of air in a HET is governed by distinct molecular-specific reaction mechanisms that vary from traditional atomic xenon and krypton mechanisms. This thesis seeks to better understand this unique ionization process and how it translates to currently decreased exhibited HET performance through four novel contributions. (1) Development of an energy flow model to visualize and understand the unique molecular energy sinks and power conversion pathways in the ionization and acceleration of air in a HET. (2) Construction of a kinetic model of electron-impact air kinetic reactions to understand mechanisms that drive air ionization and their effect on plasma parameters in a HET. (3) Derivation of an analytical efficiency model to quantify molecular propellant-specific efficiency sinks that occur during the ionization and acceleration process. (4) Analysis of experimental data from HET operation on an air propellant to determine how the composition in an air mixture influences the species production, power conversion pathways, and overall performance and efficiency.
Date and time: 2025-10-09, 2:00 P.M.
Location: MK 317
Committee:
Dr. Mitchell Walker (advisor), School of Aerospace Engineering
Dr. Wenting Sun, School of Aerospace Engineering
Dr. Sedina Tsikata, School of Aerospace Engineering
Dr. Lukas Graber, School of Electrical and Computer Engineering
Dr. Umair Siddiqui, Phase Four