June 12, 2024

A plasma propulsion device
A plasma propulsion device that is operating in conditions that simulate very low-Earth orbit. The device operates by adding electrical energy to ionize and accelerate molecules using electromagnetic forces. The goal of this experiment is to develop a propulsion system that can refuel as it orbits the Earth.

Sustained missions in low Earth orbit, protecting fast-moving spacecraft as they reenter the atmosphere, limiting emissions in semiconductor manufacturing and clean hydrogen production – these may seem like completely unrelated subjects, but they're all areas where aerospace engineering faculty member

Thomas Underwood is applying his unique research approach.Underwood has received grants to study these topics over the last several months, totaling nearly $3 million from the Department of Energy (DOE), Defense Advanced Research Project Agency (DARPA), Samsung, and the University Consortium for Applied Hypersonics (UCAH). There's a through line uniting them – the infusion of electrical energy into gases to create plasmas. These plasmas can be applied to various concepts, from propelling spacecraft to reducing emissions.

"The core idea is to use electrical energy to create a plasma discharge that can rethink how fuels are made, stored and used on-demand,” said Underwood, an assistant professor in the Department of Aerospace Engineering and Engineering Mechanics. “These plasmas feature energized electrons that can activate molecules, drive chemical reactions, synergize with catalytic materials, or accelerate molecules without needing bulk scale heating or pressurization.”

The projects: A recent $1 million grant from DARPA will support sustained travel in low Earth orbit through a big goal: the reimagination of propulsion systems. Instead of using atomic propellants based on xenon and other limited elements, the researchers will develop and test a prototype propulsion system that can harvest molecules and solar energy out of the atmosphere itself to compensate for drag on spacecraft.

In a $1.5 million grant from UCAH, Underwood and his colleagues are designing a multifunctional thermal protection system (TPS) to help spacecraft retain radio signals during hypersonic flight and upon re-entering the atmosphere. Loss of communication has consistently plagued space missions, and the plan is to embed layers of metamaterials into spacecraft TPSs directly to mitigate the attenuation of radiofrequency communication through plasmas. This highly collaborative project includes Underwood's aerospace colleague Noel Clemens and researchers from the Missouri S&T and Lockheed Martin.

A $450,000 grant from the Samsung Global Research Collaboration program focuses on the abatement of harmful emissions, including N2O and fluorocarbons, created during semiconductor manufacturing. In collaboration with chemical engineer C. Buddie Mullins and Graeme Henkelman from the College of Natural Sciences' Department of Chemistry, this project aims to capture and convert molecules emitted during these processes before they can escape plants and make it into the atmosphere. As semiconductor manufacturing increases, this is a critical need because molecules emitted during these processes produce long-lasting impacts with atmospheric lifetimes that can exceed 10,000 years.

"We need to find ways to destroy the molecules that come from semiconductor fabrication before they are emitted," Underwood said. "If we design plasma systems to synergize with catalytic materials, we can develop new and more efficient ways to abate harmful molecules before they can be emitted into the atmosphere.”

One final area of emphasis for Underwood's work in plasmas is the creation of sustainable hydrogen directly from distributed resources like methane. He and his collaborators have several research papers underway in this area that are supported by the DOE. And Underwood, along with Mullins and mechanical engineer Michael Webber, recently received funding from the UT Energy Institute's Strategic Seed Grant program to study "distributed and electrified green ammonia production using plasma-catalysis."

Tom Underwood and Ph.D. candidate Charan Nallapareddy

Why it matters: In many industries, innovation is limited by issues with power sources. For example, it's nearly impossible to sustain missions in low Earth orbit because of harsh conditions and limits on the amount of propellant a spacecraft can carry.

Several of these projects, like the self-fueling propellant technology, are not small improvements, but reimaginations of established systems.  

"These are grand challenges, holy grail problems," Underwood said. "How can we fly spacecraft without forcing them to carry propellant and protect them upon re-entry? How can we come up with new ways to store, convert, and utilize fuels? How can we minimize pollution from semiconductor manufacturers?"

How we got here: Raise your hand if you've heard something like, "In 20 years, nuclear fusion will take care of all energy problems." He read a few books about it as a high schooler and became intrigued.

Plasmas are a critical part of nuclear fusion, serving as the medium to drive fusion reactions. They are inherently chaotic, and discovering new ways to control them has long inspired Underwood.

"When you put energy in to create and sustain plasmas, they don’t want to stay in one place, the energy wants to go everywhere," Underwood said. "How do you force the energy you add to go where you want it, whether it be to excite a molecule or accelerate a flow? This fundamental question opens so many avenues of research. There are all kinds of knobs we can turn to try and control plasmas, and it's up to us to turn these knobs in the right way to generate processes that can solve the societal problems that we face today."