How Liquid Uranium Could Get Us to Mars in Half the Time

Space travel has always been a long haul since chemical rockets, the space age’s workhorses, guzzle fuel and plod through the universe, making a trip to Mars a year long slog. But a team at Ohio State University is breaking the rules with a new concept: a nuclear powered rocket that could cut the travel time in half. Their Centrifugal Nuclear Thermal Rocket, or CNTR, replaces solid fuel rods with liquid uranium, and that’s a big increase in efficiency that makes Mars feel like a weekend getaway.

Nuclear propulsion is not new; in the 1960s NASA’s Rover/NERVA program experimented with nuclear thermal propulsion, using reactors to heat hydrogen into a hot gas that was blown out of a nozzle for thrust. Those early designs increased the effectiveness of chemical rockets, achieving a specific impulse—a measure of how much thrust you get per unit of propellant—of around 900 seconds, compared to 450 seconds for standard engines. According to a paper in Acta Astronautica, CNTR wants to do even better, potentially reaching 1800 seconds.

Here’s how it works: CNTR spins liquid uranium inside rotating cylinders and uses centrifugal force to keep the molten metal in place. This liquid fuel immediately heats the propellant—most likely hydrogen, but ammonia, methane, or even propane could work—to produce a hot gas that rockets out the back. What’s the result? A more efficient and adaptable propulsion system that can use resources found on asteroids and in the Kuiper Belt. Spencer Christian, a PhD student at Ohio State who’s leading the prototype build, thinks this could mean a one way trip to Mars in six months, reducing the health risks from prolonged exposure to cosmic radiation and zero gravity.

Unlike chemical rockets stuck in rigid flight paths, CNTR opens up new trajectories, allowing spacecraft to take shortcuts through space. Dean Wang, an associate professor at Ohio State and member of the project, says this could make missions to far flung destinations like Saturn or Neptune more feasible. Robotic probes could zip to the outer planets in half the time it took New Horizons to reach Pluto—a nine year journey that could be cut down dramatically. Even better, the ability to use different propellants means future missions could refuel in space, tapping into the resources floating out there in the void.

It’s already being tested. Researchers from Ohio State and the University of Alabama in Huntsville, with support from NASA’s Space Technology Mission Directorate, are working on the CNTR design. A recent test at Ohio State’s research reactor, in partnership with the Department of Energy’s Oak Ridge National Laboratory, tested fuel coatings to withstand the extreme conditions inside a nuclear rocket. The coatings, made of zirconium carbide, protect the critical components from the heat, a key step towards making CNTR a reality.
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