If the U.S. wants to send humans to Mars in the 2030s, it may have to rely on nuclear-fission-powered spacecraft to cut the travel time down to three to four months. (Image: © NASA)

Space is about to go nuclear — at least if private companies get their way.

At the 23rd annual Commercial Space Transportation Conference (CST) in Washington, D.C., in January, a panel of nuclear technology experts and leaders in the commercial space industry spoke about developments of the technology that could propel future spacecraft faster and more efficiently than current systems can.

Nuclear technology has powered spacecraft such as NASA's Mars rovers, the Cassini mission and the two Voyagers that are currently exploring the outer reaches of our solar system. But those fuel sources rely on the passive decay of radioactive plutonium, converting heat from that process into electricity to power the spacecraft.

Instead, the CST panelists discussed Nuclear Thermal Propulsion (NTP), a technology developed in the 1960s and '70s that relies on the splitting, or fission, of hydrogen atoms. Although fission is associated with more warlike images, the panel's experts emphasized the safety of nuclear thermal propulsion, which would use low-enriched uranium.

An NTP-powered spacecraft would pump hydrogen propellant through a miniature nuclear reactor core. Inside this reactor core, high energy neutrons would split uranium atoms in fission reactions; those freed neutrons would smack into other atoms and trigger more fission. The heat from these reactions would convert the hydrogen propellent into gas, which would produce thrust when forced through a nozzle.

This chain reaction is the key to NTP's power, panelist Venessa Clark, CEO of Atomos Space, a company that’s developing thermonuclear propulsion powered spacecraft to provide in-space transportation options to satellite operators, told Space.com. A soda-can-size fission reactor could propel humans to Mars in just three to four months, she said, about twice as fast as the currently estimated time it could take a chemically propelled ship to carry humans to the Red Planet.

"The reason we want to use a reactor is we have a lot of power from [it], which is really what enables us to be so agile and move such heavy payloads so quickly," Clark said. 

So where does the commercial sector fit in? According to Jeff Thornburg, CEO of Interstellar Technologies, an aerospace engineering company focused on propulsion, and another panelist, it's the speed that commercial ventures offer, which can get new technologies off the ground both literally and figuratively. 

"I know how fast we've changed the dynamic and how we develop technologies for the commercial space sector for launch now, which didn't exist 20 years ago," Thornburg told Space.com. He wants to apply that same methodology to developing fast and efficient nuclear propulsion.

"I don't think the government's going to be able to move quickly enough to stay competitive in this technology area," Thornburg said. He noted that NASA is currently focused on its Artemis lunar program and launching to the moon doesn't necessarily require nuclear technology. 

Sending astronauts to Mars and minimizing their time in a dangerous radiation environment however, may require a faster propulsion system, and that's what NTP technology might provide. 

But the government still has to play some role, both Clark and Thornburg said. Government agencies like NASA and the military branches may be the first clients for these commercial companies. Clark noted NASA's recent pushes to partner with the private sector, such as its commercial lunar payload services program and its commercial crew program. 

"Government players, NASA and also now the Air Force are looking at procuring services rather than funding the development of technology, which is really exciting for us," Clark said.

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