Date of Award
2025
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Materials Science and Engineering (MS)
Administrative Home Department
Department of Materials Science and Engineering
Advisor 1
Paul G. Sanders
Committee Member 1
Tim J. Langan
Committee Member 2
Sriram Vijayan
Abstract
Currently, no viable emitter materials exist for Hall-effect thrusters used in air-breathing electric propulsion systems (ABEP) operating in very low earth orbit (VLEO). The atmosphere at VLEO is primarily composed of atomic oxygen and nitrogen, with the oxygen having a catastrophic effect on emitter stability, leading to rapid failure. LaB6 is a rare-earth hexaboride emitter used in Hall-effect thrusters propelled by xenon or krypton and has better oxygen resistance than other common emitter materials. Modeling by others has suggested that optimizing mixed rare-earth hexaboride emitters may have potential for VLEO thrusters. Binary and mixed rare-earth hexaborides were synthesized based on their ability to form oxide films that will fail in tension as predicted by models utilizing the Pilling-Bedworth ratio and Ellingham diagrams. Testing conducted by the sponsor, Aerojet Rocketdyne, produced emitters with an order of magnitude higher operating lifetimes, but with accelerated material consumption. Even with improved lifetimes, further work is needed to design a propulsion system to meet the design requirements.
Recommended Citation
Eacker, Seth A., "MATERIAL OPTIMIZATION OF THERMIONIC EMITTERS FOR OPERATION IN OXYGEN-CONTAINING ATMOSPHERES", Open Access Master's Thesis, Michigan Technological University, 2025.