{"685550":{"#nid":"685550","#data":{"type":"event","title":"PhD Defense by William Brabston","body":[{"value":"\u003Cp\u003EStudent Name: William Brabston\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EAdvisor: Dr. Mitchell Walker\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EMilestone: PhD Thesis Final Examination (Defense)\u003Cbr\u003E\u003Cbr\u003EDegree Program: Aerospace Engineering\u003Cbr\u003E\u003Cbr\u003ETitle: Analysis of the Ionization Mechanisms of an N2\/O2 Air Mixture in a Hall Effect Thruster\u003Cbr\u003E\u003Cbr\u003EAbstract: 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.\u003Cbr\u003E\u003Cbr\u003EDate and time: 2025-10-09, 2:00 P.M.\u003Cbr\u003E\u003Cbr\u003ELocation: MK 317\u003Cbr\u003E\u003Cbr\u003ECommittee:\u003Cbr\u003EDr. Mitchell Walker (advisor), School of Aerospace Engineering\u003Cbr\u003EDr. Wenting Sun, School of Aerospace Engineering\u003Cbr\u003EDr. Sedina Tsikata, School of Aerospace Engineering\u003Cbr\u003EDr. Lukas Graber, School of Electrical and Computer Engineering\u003Cbr\u003EDr. Umair Siddiqui, Phase Four\u003Cbr\u003E\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EAnalysis of the Ionization Mechanisms of an N2\/O2 Air Mixture in a Hall Effect Thruster\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Analysis of the Ionization Mechanisms of an N2\/O2 Air Mixture in a Hall Effect Thruster"}],"uid":"27707","created_gmt":"2025-10-06 13:56:10","changed_gmt":"2025-10-06 13:56:46","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2025-10-09T14:00:00-04:00","event_time_end":"2025-10-09T16:00:00-04:00","event_time_end_last":"2025-10-09T16:00:00-04:00","gmt_time_start":"2025-10-09 18:00:00","gmt_time_end":"2025-10-09 20:00:00","gmt_time_end_last":"2025-10-09 20:00:00","rrule":null,"timezone":"America\/New_York"},"location":"MK 317","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}