Caption: Nuclear Engineering Ph.D. student Jason Reynolds stands next to a Thermogravimetric Analysis/Differential Scanning Calorimetry, which provides simultaneous thermal analysis.
CEC researchers aim to develop nuclear processes for space travel
The U.S. Defense Advanced Research Projects Agency is aiming to successfully demonstrate an in-space flight using nuclear thermal propulsion (NTP) in 2026. NTP is considered more efficient by using systems that are faster and smaller than electric or chemical processes. Mechanical Engineering Chair and Professor Travis Knight and his research team, including Mechanical Engineering Professor and SmartState Chair Ted Besmann, and professors Frank Chen and Xinyu Huang, are currently developing mixed carbide fuels for NTP that will increase efficiency, decrease costs and help maintain the United States’ edge in space exploration.
The NASA Marshall Space Flight Center is funding Knight’s research. During his doctoral studies, Knight researched space nuclear power, specifically mixed carbide fuels for nuclear thermal propulsion. A mixed carbide fuel example could include a mix of uranium, zirconium and niobium carbide. “I didn’t continue as strongly in this line of research but still pursued advanced fuels, including carbide fuels for terrestrial applications. This present research is exciting because it's enabling human space exploration,” Knight says.
NTP research dates back to the 1960s. It is considered a better alternative method of space travel for manned missions by offering high thrust and higher specific impulse, which reduces costs and provides power for long periods of travel with less hydrogen propellant. Nuclear fuels must withstand the harsh environments of high temperature, radiation damage and possible reactions with the hydrogen propellent. Knight plans to show how advanced fuels offer excellent performance for propulsion, especially when used in the mixed carbide formulation.
“Mixed carbide fuels offer high melting points, allowing for very high operating temperatures for even more efficient use of propellent,” Knight says.
For NTP, the fission process creates heat that causes the hydrogen propellant to reach a very high temperature before it is fired out of a nozzle to create thrust. The higher temperature and lower atomic mass of the propellant enable a high specific impulse, which is a measure of the efficiency of creating the required thrust.
“The high thrust and high specific impulse mean that you can get to a destination such as Mars in a shorter time, reducing the exposure of astronauts to cosmic radiation. It's ironic that you need nuclear power to reduce radiation exposure,” Knight says.
Los Alamos National Laboratory will make powders of the mixed carbides and send them to the Marshall Space Flight Center, which will produce samples for testing. Knight’s research team will then characterize the samples to assist in developing models of fuel performance.
“We've fabricated and tested similar materials at UofSC using a different production or fabrication route. This earlier research on carbide fuels was aimed at producing a fuel for a Generation IV reactor design, the Very High Temperature Reactor, which would be used for both electricity generation and process heat for production of hydrogen or synthetic fuels for use in transportation,” Knight says.
Besmann and his post-doctoral student have also started modeling work, which will be important in predicting interactions with the hot hydrogen propellent. Knight’s Ph.D. student Jason Reynolds previously worked at the Marshall Space Flight Center as a research assistant. He primarily worked with radiation testing and researching solid rocket motor materials, but in his last six months, he worked with the nuclear group that was responsible for ceramic metallic nuclear fuels another alternative fuel for NTP.
“One of the important things we’ll do is scanning electron microscopy to understand the microstructure of the samples evaluating different sample compositions and methods of fabrication. NASA will use the results we generate to refine the fabrication process and improve fuel performance for NTP,” Reynolds says.
According to Knight, power and propulsion are the two applications that can result from the research into mixed carbide fuels. “Nuclear power would maintain the operations of the spacecraft and operate like a conventional nuclear reactor by generating heat from the fission process that’s turned into electricity.” Knight says.
Knight is also confident that NTP can help the U.S. maintain an edge in space exploration.
“Putting someone on Mars would certainly be an achievement, but NTP could also be used to travel and carry cargo to the moon or be utilized as a space tug, which could move assets in space,” Knight says. “You're enabling new technologies and approaches in space exploration and uses of space-based technology.”
But the technology would have applications beyond rockets and space travel. This includes a greater understanding of the science of carbide fuels that would have applications for terrestrial power generation.
“If you think about most things that are studied for space, they eventually find an application here on Earth,” Knight says. “How many advanced materials that have been developed for space applications have found their way into everyday life? Hopefully our work will provide a better understanding of advanced nuclear fuels and a range of compositions that could power terrestrial reactors.”