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David Zidar
Department of Mechanical and Aerospace Engineering
Missouri University of Science and Technology
Adviser: Dr. Joshua L. Rovey
Abstract
Surface properties of Hall-effect thruster channel walls play an important role in the performance and lifetime of the device. Physical models of near-wall effects are beginning to be incorporated into thruster simulations, and these models must account for evolution of channel surface properties due to thruster operation. Results from this study show differences in boron nitride channel surface properties from beginning-of-life and after 100's of hours of operation. A worn Grade M26 boron nitride thruster channel is compared with its corresponding pristine and shadow-shielded samples. Pristine M26 grade boron nitride surface roughness is 18400±1400 Å, while the worn sample is 52300±4200 Å at the exit plane. Comparison of pristine and worn channel surfaces also show surface properties are dependent on axial position within the channel. For example, surface roughness increases by as much as 73% and surface atom fraction of carbon and metallic atoms decreases by a factor of 2.9 from anode to exit plane. Macroscopic striations at the exit plane are found to be related to the electron gyroradius and give rise to anisotropic surface roughness. Smoothing of ceramic grains at the microscopic level is also found.
David Zidar is originally from Hartford, Ohio. In 2009 he received his BS in aerospace engineering from Saint Louis University. He is currently pursuing an MS in aerospace engineering while working as a graduate research assistant in the Aerospace Plasma Laboratory at Missouri University of Science and Technology. |
