Congratulations to Aerospace Engineering Assistant Professor Benjamin Jorns, recipient of the Air Force Office of Scientific Research’s (AFOSR) Young Investigator Program (YIP) award. The award-winning proposal, “Predictive Modeling for Complex Plasma Systems with Poorly Understood Physics” describes the need for additional research on electric thruster technologies such as Hall thrusters and Field Reversed Configuration (FRC) thrusters. As a form of propulsion with moderate specific impulse, Hall thrusters have been historically used for in-orbit satellite orientation adjustment and for propulsion of robotic space vehicles. FRC thrusters are a much less developed technology but could have unprecedentedly high performance and power density compared to state-of-the-art electric thrusters.
The X3 Hall thruster operating at 30 kW in the PEPL Large Vacuum Test Facility. Schematic (left) of PEPL's Experimental Coaxial Field Reversed Configuration Thruster (XOCOT) system and photograph (right) of the XOCOT annular chamber, test setup, and current transmission cables. PEPL's Large Vacuum Test Facility (LVTF).
Professor Jorns explains that although Hall thrusters, which he studies as co-Director of the UM Plasmadynamics and Electric Propulsion Laboratory (PEPL), are “a mature technology with quite a bit of flight heritage, there are no predictive models for either of these [Hall or FRC] thrusters. You cannot program a new prototype geometry into CAD or a commercial code, run it, and be confident that it will predict performance. This is because there are aspects of the fundamental physical processes in these devices that we do not understand sufficiently to model.” Specifically, Hall thruster researchers do not have a strong understanding of how electrons move in the plasma. For FRC thrusters, a type of plasma “rail gun,” there are many open and fundamental questions about how the propellant can be efficiently accelerated.
As a YIP awardee, Professor Jorns will receive a $450,000 research grant to be used over a three-year period. With this funding, he and his team will be developing and modeling technologies for United States Air Force (USAF) applications. Professor Jorns’ goal for Hall thrusters is to “finish this work with algorithms that can be incorporated into existing Hall thruster codes and that actually demonstrate a predictive capability” for “mode transitions, performance, and dynamical response.” For FRC thrusters, on the other hand, there is much more room for development than the more mature Hall thruster technology. Facing the challenge of building and optimizing an operational FRC thruster, Professor Jorns explains, “I would be very happy if [at the end of the contract] we actually had a working thruster with 1) new insight into how they work and 2) a demonstration of optimized performance.”
As a widely-renowned laboratory for plasmadynamics research, PEPL is undertaking a series of research efforts for a variety of applications. The lab is home to an extensive family of five- to six-kilowatt Hall thrusters, a series of micropopulsion concepts, and a 100-kilowatt class, three-channel thruster design dubbed the X3.