Researchers have announced progress in the development of a Centrifugal Nuclear Thermal Rocket (CNTR), a next-generation propulsion system powered by liquid uranium fuel. This advanced concept is being developed by teams at the University of Alabama in Huntsville and The Ohio State University.

The CNTR is a nuclear thermal propulsion (NTP) system that heats hydrogen propellant directly using the reactor’s liquid uranium fuel. By spinning the molten uranium in a centrifuge, hydrogen gas is passed through the superheated liquid and expelled through a nozzle to generate thrust. This method is designed to achieve a specific impulse of approximately 1,500 seconds—nearly double that of current solid-core NTP designs, such as NASA’s DRACO Program, which aims for around 900 seconds.

Unlike traditional solid fuel elements, the CNTR uses rotating cylinders to contain the liquid uranium, held in place by centrifugal force. This innovative design could significantly enhance a spacecraft’s delta-v, or change in velocity, without sacrificing thrust.

However, the CNTR concept faces several engineering challenges. A recent paper in Acta Astronautica outlines ten major technical hurdles, with current research focusing on four key areas. One area is improving the stability of nuclear reactions. Researchers are experimenting with the addition of Erbium-167 to manage internal temperatures, while also addressing the impact of fission byproducts such as xenon and samarium, which can disrupt the reaction if not properly removed.

Another focus is understanding how hydrogen bubbles behave within the liquid fuel. Using experimental setups named Ant Farm and BLENDER II, scientists are studying bubble dynamics through X-ray imaging in uranium-surrogate materials. Despite these efforts, mathematically modeling the bubble behavior remains a complex task.

To improve engine performance, the research team has employed a genetic algorithm to refine integration modeling. Under ideal conditions, this approach predicts a specific impulse of 1,512 seconds. Achieving this would require more centrifuges and faster rotation rates than initially proposed.

A critical issue still under investigation is preventing uranium from escaping through the nozzle along with the hydrogen propellant. This loss could dramatically reduce engine efficiency. To counter this, researchers are exploring the use of dielectrophoresis (DEP) to recover vaporized uranium, aiming for a recovery rate of 99%.

While the CNTR is not yet ready for full-scale prototyping, ongoing work will focus on minimizing uranium loss and testing the DEP recovery system. The research team emphasizes that the CNTR has the potential to revolutionize in-space propulsion, offering up to twice the performance of current solid fuel NTP technologies like those being developed for NASA’s DRACO mission.

By Impact Lab