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Dr. Walker’s primary research interests lie in electric propulsion, plasma physics, and hypersonic aerodynamics/plasma interaction. He has extensive design and testing experience with Hall thrusters and ion engines. Dr. Walker performed seminal work in Hall thruster clustering and vacuum chamber facility effects. His current research activities involve both theoretical and experimental work in advanced spacecraft propulsion systems, diagnostics, plasma physics, helicon plasma sources, magnetoplasmadynamic thrusters, and pulsed inductive thrusters.

Current Domestic Projects

High-Fidelity Coupling of Predictive Plasma-Wall Models

Very-short Antennas via Ionized Plasmas for Efficient Radiation (VAIPER)

Magnetohydrodynamic Power Generation for Upper-Stage Rockets

Proprietary

Hi-speed Plasma Science (HiPS) to Enable Advanced Radiation Devices

Solar Array Exposure to an Arcjet Plume

Magnetohydrodynamic Energy Generation and Flow Control for Planetary Entry Systems

Supported by NASA

GT HPEPL is working to investigate magnetohydrodynamic energy generation during planetary entry.  Atmospheric reentry plasmas are simulated using an artificially radio-frequency ionized supersonic plasma wind tunnel developed in collaboration with NASA JPL. Results include electrical energy harvested from the plasma wind tunnel using a prototype magnetohydrodynamic energy generator design appropriate to planetary entry systems.

Past Research Projects

Comprehensive Study of Plasma-Wall Interaction
Supported by AFOSR – Visit Website
In collaboration with researchers from Georgia Tech, Georgia Tech Research Institute, University of Alabama, and George Washington University, GT HPEPL investigated the interactions between a confined plasma and adjacent wall from both plasma physics and materials science perspectives.

Helicon Plasma Source
Supported by MOOG and AFOSR
This research focused on the physics and behavior of RF plasma sources in the HF range. The work also examined the potential of helicon devices as electrode-less thrusters that use plasma double layers to accelerate ions. Thrust measurements and plume evaluation were executed in this work.

Molecular Dynamics of Boron Nitride – Xenon Plasma Interface
Supported by AFOSR – Visit Website
In collaboration with Dr. Julian Rimoli, the focus of this effort was to understand the physics behind Hall Thruster discharge channel wall erosion, including microstructural effects that may seed large-scale variations in erosion.

Development of Negative Ion Thruster
Supported by NASA MSFC
GT HPEPL worked on developing an ion thruster that uses electronegative gas as a propellant. Unlike most ion thrusters, electronegative thrusters produce both positive and negative ions and accelerate both species to generate thrust. This also enables the plasma to remain quasineutral, eliminating the need for neutralizing devices like cathodes at the thruster exit. This work was supported with a grant from NASA Marshall Space Flight Center. It is called the MINT for Marshall’s Ion-ioN Thruster.

Laboratory Affiliations

Electric Rocket Propulsion Society

Air Force Research Laboratory

Georgia Tech Center for Space Systems