The Thermal Nuclear Engine That Could Get Us to Mars in Just 3 Months

It’s twice as efficient as a chemical rocket.

Ultra Safe Nuclear Corporation (USNC) has designed a new thermal nuclear engine it says could carry astronauts to Mars in just three months—and back to Earth in the same amount of time. By using ceramic microcapsules of high assay low enriched uranium (HALEU) fuel, USNC’s thermal nuclear engine could cut the trip in half even from optimistic estimates.

“The problem is to produce a nuclear reactor that is light enough and safe enough for use outside the Earth’s atmosphere—especially if the spacecraft is carrying a crew,” New Atlas explains.

Thermal nuclear for propulsion is an old idea. While weapons are thermal, other applications have lingered in the experimental stage and then been discarded, but they’ve still been studied off and on for decades. These designs use the astonishing heat generated by a nuclear reaction to push a rocket at speeds approaching the Star Trek realm compared to what we use today. And they contrast with traditional chemical rockets, where chemical propellants like liquid oxygen are used to make something more like a supersized fossil fuel combustion engine.

USNC’s technology hits just months after Elon Musk suggested that a nuclear engine could be key to getting astronauts to Mars. For Musk, the concern was for astronaut health and safety: the longer the trip to Mars, the longer astronauts are exposed to extraordinary cosmic radiation.

The Department of Energy has found that HALEU fuel is, relative to the higher risk of handling nuclear materials at all, less dangerous than it could be. Cosmic radiation is probably far worse, and negotiating around it has been a huge barrier to any hypothetical Mars travel.

The reactor in USNC’s nuclear thermal propulsion engine is very similar to the design that powers its upcoming microreactor energy facilities. That’s not a coincidence. Although USNC is starkly divided into USNC-Tech and USNC-Power, with different leadership and goals, the corporation’s “ultra safe” goals and designs are shared. Both use HALEU fuel whose ceramic casing is safe in very high temperatures.

“Key to USNC-Tech’s design is a conscious overlap between terrestrial and space reactor technologies,” USNC-Tech CEO Paolo Venneri said in a statement. “This allows us to leverage the advancements in nuclear technology and infrastructure from terrestrial systems and apply them to our space reactors.”

USNC-Tech says its engine delivers twice the thrust of a chemical engine, and because of the encapsulated, low enriched fuel, it’s more stable than previous nuclear thermal designs. This is key, because chemical rockets are simply maxing out.

We’ve plumbed non-nuclear thrust technology to the full depth of our possible understanding, and the next step up from this plateau will require something different. Today, it’s hard to imagine that being anything other than nuclear propulsion.