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Mitchell Louis Ronald Walker II (born July 18, 1977) is an American aerospace engineer, researcher, and educator. As of January 1, 2024, he is the chair of the Daniel Guggenheim School of Aerospace Engineering (AE) in the College of Engineering at the Georgia Institute of Technology. [1] Prior to serving as the chair, he was the associate dean for academic affairs at the Georgia Tech College of Engineering. [2] He is the founder and director of the High-Power Electric Propulsion Laboratory (HPEPL) at Georgia Tech, founded in 2005. [3] The lab aims to advance the understanding of plasma physics and expand the technology of electric propulsion devices for future space use.
As a leader in the field of electric propulsion, he has served on the National Research Council Reusable Booster System Committee, [4] the NASA Advisory Council Technology, Innovation, and Engineering Committee, [5] the U.S. Department of Energy, Office of Science Fusion Energy Sciences Advisory Committee (FESAC) [6] and the National Academies of Sciences Engineering Medicine, Committee to Review the Air Force Reusable Booster System Study. [7]
Walker has authored over 100 scientific journal articles and conference papers in electric propulsion and plasma physics. [8] In addition, he serves as an associate editor of the American Institute of Aeronautics and Astronautics (AIAA) Journal of Spacecraft and Rockets. [9] Walker is also on the editorial board of the Journal of Electric Propulsion [10] and Frontiers in Physics and Astronomy and Space Sciences-Plasma Physics. [11]
Walker was born in Alma, Michigan, but grew up in Cassopolis, Michigan, a lakeside community on the southwest side of the state.[ citation needed ]
He earned his B.S.E. in aerospace engineering in 1999, M.S. in aerospace engineering in 2000, and Ph.D. in aerospace engineering in 2005 from the University of Michigan. [12]
Walker joined the faculty at Georgia Tech in AE as an assistant professor in 2005. He became an associate professor in 2011 and a full professor in 2017. In two years, he became the associate chair for graduate programs, where he served for four years. Walker is the principal investigator and director of the Joint Advanced Propulsion Institute (JANUS), [13] NASA's Space Technology Research Institute, which develops strategies and methodologies to overcome limitations in ground testing of high-power electric propulsion systems. The $15 million project includes 11 partner universities and 17 researchers. In 2022, he served as the associate dean for academic affairs for the Georgia Tech College of Engineering. [14] In January 2024, he became the chair of the highly ranked [15] [16] AE School.
Walker's primary research interests focus on electric propulsion, plasma physics, and hypersonic aerodynamics/plasma interaction. He has worked in the development of Hall thrusters and ion engines. Walker has done relevant research in the areas of Hall thruster clustering, vacuum chamber facility effects, particle-material interactions, and electronic emission from carbon nanotubes. His research involves theoretical and experimental work in advanced spacecraft propulsion systems, diagnostics (including THz time-domain spectroscopy and Thomson scattering), plasma physics, helicon plasma sources, magnetoplasmadynamic thrusters, and pulsed inductive thrusters. [17] [18]
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric entry.
In spacecraft propulsion, a Hall-effect thruster (HET) is a type of ion thruster in which the propellant is accelerated by an electric field. Hall-effect thrusters are sometimes referred to as Hall thrusters or Hall-current thrusters. Hall-effect thrusters use a magnetic field to limit the electrons' axial motion and then use them to ionize propellant, efficiently accelerate the ions to produce thrust, and neutralize the ions in the plume. The Hall-effect thruster is classed as a moderate specific impulse space propulsion technology and has benefited from considerable theoretical and experimental research since the 1960s.
An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. An ion thruster creates a cloud of positive ions from a neutral gas by ionizing it to extract some electrons from its atoms. The ions are then accelerated using electricity to create thrust. Ion thrusters are categorized as either electrostatic or electromagnetic.
A magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electrically powered spacecraft propulsion which uses the Lorentz force to generate thrust. It is sometimes referred to as Lorentz Force Accelerator (LFA) or MPD arcjet.
A pulsed plasma thruster (PPT), also known as a Pulsed Plasma Rocket (PPR), or as a plasma jet engine (PJE), is a form of electric spacecraft propulsion. PPTs are generally considered the simplest form of electric spacecraft propulsion and were the first form of electric propulsion to be flown in space, having flown on two Soviet probes starting in 1964. PPTs are generally flown on spacecraft with a surplus of electricity from abundantly available solar energy.
A nuclear electric rocket is a type of spacecraft propulsion system where thermal energy from a nuclear reactor is converted to electrical energy, which is used to drive an ion thruster or other electrical spacecraft propulsion technology. The nuclear electric rocket terminology is slightly inconsistent, as technically the "rocket" part of the propulsion system is non-nuclear and could also be driven by solar panels. This is in contrast with a nuclear thermal rocket, which directly uses reactor heat to add energy to a working fluid, which is then expelled out of a rocket nozzle.
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is an electrothermal thruster under development for possible use in spacecraft propulsion. It uses radio waves to ionize and heat an inert propellant, forming a plasma, then a magnetic field to confine and accelerate the expanding plasma, generating thrust. It is a plasma propulsion engine, one of several types of spacecraft electric propulsion systems.
Nuclear pulse propulsion or external pulsed plasma propulsion is a hypothetical method of spacecraft propulsion that uses nuclear explosions for thrust. It originated as Project Orion with support from DARPA, after a suggestion by Stanislaw Ulam in 1947. Newer designs using inertial confinement fusion have been the baseline for most later designs, including Project Daedalus and Project Longshot.
A field-reversed configuration (FRC) is a type of plasma device studied as a means of producing nuclear fusion. It confines a plasma on closed magnetic field lines without a central penetration. In an FRC, the plasma has the form of a self-stable torus, similar to a smoke ring.
ATS-6 was a NASA experimental satellite, built by Fairchild Space and Electronics Division It has been called the world's first educational satellite as well as world's first experimental Direct Broadcast Satellite as part of the Satellite Instructional Television Experiment between NASA and Indian Space Research Organisation (ISRO). It was launched May 30, 1974, and decommissioned July 1979. At the time of launch, it was the most powerful telecommunication satellite in orbit. ATS-6 carried no fewer than 23 different experiments, and introduced several breakthroughs. It was the first 3-axis stabilized spacecraft in geostationary orbit. It was also the first to use experimentally with some success electric propulsion in geostationary orbit. It also carried several particle physics experiments, including the first heavy ion detector in geostationary orbit.
High Power Electric Propulsion (HiPEP) is a variation of ion thruster for use in nuclear electric propulsion applications. It was ground-tested in 2003 by NASA and was intended for use on the Jupiter Icy Moons Orbiter, which was canceled in 2005.
A plasma propulsion engine is a type of electric propulsion that generates thrust from a quasi-neutral plasma. This is in contrast with ion thruster engines, which generate thrust through extracting an ion current from the plasma source, which is then accelerated to high velocities using grids/anodes. These exist in many forms. However, in the scientific literature, the term "plasma thruster" sometimes encompasses thrusters usually designated as "ion engines".
Spacecraft electric propulsion is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generating thrust to modify the velocity of a spacecraft in orbit. The propulsion system is controlled by power electronics.
Robert David Braun is an American aerospace engineer and academic. He has served as the dean of the College of Engineering and Applied Science at the University of Colorado Boulder, the David and Andrew Lewis Professor of Space Technology at the Georgia Institute of Technology, and the NASA Chief Technologist. Currently, Dr. Braun is the Space Sector Head at the Johns Hopkins University Applied Physics Laboratory (APL).
Busek Company Incorporated is an American spacecraft propulsion company that builds thrusters, electronics, and various systems for spacecraft.
Atmosphere-breathing electric propulsion, or air-breathing electric propulsion, shortly ABEP, is a propulsion technology for spacecraft, which could allow thrust generation in low orbits without the need of on-board propellant, by using residual gases in the atmosphere as propellant. Atmosphere-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible.
Direct Fusion Drive (DFD) is a conceptual, low radioactivity, nuclear-fusion rocket engine, designed to produce both thrust and electric power, suitable for interplanetary spacecraft. The concept is based on the Princeton field-reversed configuration reactor, invented in 2002 by Samuel A. Cohen. It is being modeled and experimentally tested at Princeton Plasma Physics Laboratory, a U.S. Department of Energy facility, as well as modeled and evaluated by Princeton Satellite Systems (PSS). As of 2018, a direct fusion drive project driven by NASA is said to have entered its simulation phase, presented as the second phase of the concept's evolution.
ASTER is a planned space mission under development by the Brazilian Space Agency that will launch a spacecraft to orbit a near-Earth object known as (153591) 2001 SN263, a triple asteroid system. The launch is scheduled for 2025, with a rendezvous in 2024/2027.
David Y. Oh is an American spacecraft systems engineer and expert in electric propulsion. Dr. Oh currently works at the Jet Propulsion Laboratory (JPL) as the NASA Psyche mission chief engineer. Prior to this role he served as the Project Systems Engineering Manager for Psyche. He was also the cross-cutting phase lead and lead flight director for the NASA Mars Science Laboratory mission and was recognized in popular media for living on Mars time with his family during the month following the landing of the Curiosity rover.
L. Brad King is an American engineer. He is the CEO and co-founder of Orbion Space Technologies, an aerospace company based in Houghton, MI, specializing in Hall-effect thrusters. He is also the CEO of Aerophysics Inc, a company based in Allouez, MI, providing "intelligence, surveillance, and reconnaissance" to the government. He is a Richard and Elizabeth Henes Endowed Professor for Space Systems in Mechanical Engineering-Engineering Mechanics at Michigan Technological University.