If humanity wants to turn Mars into more than a daydream, we need a new kind of rocket. Not just a bigger booster or a fancier capsule, but something radically different. At Ohio State University and the University of Alabama in Huntsville, engineers are betting on a dangerous-sounding fuel that might slash the time it takes to reach the Red Planet — molten uranium.
Their prototype, called the centrifugal nuclear thermal rocket (CNTR), is pretty wild. Instead of relying on chemical combustion, or even the solid nuclear fuels tested in the 1960s, the CNTR spins cylinders of liquid uranium at thousands of revolutions per minute. That spinning keeps the uranium in place while hydrogen propellant bubbles through it, heating up until it blasts from the nozzle at blistering speeds.
Spencer Christian, a PhD student leading the prototype construction at Ohio State, put it bluntly: “You could have a safe one-way trip to Mars in six months, for example, as opposed to doing the same mission in a year.”
A Nuclear Detour from Chemical Rockets
Chemical rockets, the workhorses of space exploration, are nearly maxed out. At best, they can achieve about 450 seconds of specific impulse — a measure of thrust efficiency. That’s fine for hopping to the Moon or nudging satellites, but for Mars or Pluto it means long, grueling missions. New Horizons took nine painful years to reach Pluto.
Nuclear thermal propulsion, which uses reactors to heat propellant, has long promised double that efficiency. The CNTR pushes even further. According to the team’s paper in Acta Astronautica, a fully realized CNTR could hit 1,500–1,800 seconds of specific impulse. That could shrink a round trip to Mars from nearly two years to about 420 days.
Dean Wang, associate professor of mechanical and aerospace engineering at Ohio State, underscored the stakes: “The longer you are in space, the more susceptible you are to all types of health risks. So, if we can make that any shorter, it’d be very beneficial.”
The Hard Problems Hiding Inside
Of course, harnessing molten uranium inside a spinning rocket engine is not exactly a plug-and-play solution. The study lists ten daunting engineering challenges. Among them:
- Designing porous cylinder walls that let hydrogen in but keep uranium from leaking out.
- Preventing uranium vapor from saturating the exhaust, which could cripple efficiency.
- Controlling the whole thing during startup and shutdown, when instabilities are most likely.
One experiment, whimsically called BLENDER II, spins a simulant liquid metal at thousands of RPM to study how gas bubbles behave in such an extreme environment. Other researchers are exploring dielectrophoresis, using electric fields to pull stray uranium atoms out of the hydrogen stream before they rocket into space.
As the paper notes, “one or more fuel-loss mitigation techniques are required for a viable engine.” Right now, the best-case engine lifetime is about 10 hours of total burn time — a far cry from what’s required for interplanetary travel.
But the potential is there.
Why This Matters
NASA and DARPA are already investing in nuclear thermal propulsion through the DRACO program, scheduled to fly a test by 2027. That project builds on decades-old designs with solid fuel. The CNTR represents a wilder, riskier bet: molten cores, higher temperatures, but with potentially a leap in performance.
If it works, the payoff is enormous. Faster trips reduce astronaut exposure to radiation and microgravity. They also open up direct trajectories to the outer planets, bypassing the years-long detours of gravity-assist flybys. Imagine a spacecraft reaching Neptune not in fifteen years, but in seven.
But even its creators are cautious. “We have a very good understanding of the physics of our design, but there are still technical challenges that we need to overcome,” said Wang.
In other words, don’t expect molten-uranium spaceships to roll out of the hangar next year. However, each step inches us closer to rockets that make interplanetary travel feel less like an odyssey and more like a manageable long-distance commute.
The dream is bold, the challenges are brutal, but the physics is tantalizingly real. And in space exploration, that’s usually how revolutions begin.
