NASA is getting fired up about a nuclear reactor on the Moon

Nuclear reactors have been generating power on Earth for more than 70 years. How hard would it be to place one on the moon to provide copious, continuous energy through the cold, dark, 2-week-long lunar nights? And could that be accomplished in less than five years?

Transportation Secretary Sean Duffy, who is now also NASA's acting administrator, called for just that last week: a reactor producing 100 kilowatts of electricity -- enough to power about 80 households in the United States -- that would launch to the moon before 2030.

Why put a nuclear reactor in space?

Nuclear reactor technology would transform the ability of humanity to travel and live in the solar system. Many of NASA's robotic spacecraft today operate at power levels equivalent to what a few incandescent light bulbs consume. That limits what scientific instruments can be put on board.

The International Space Station gets its energy from swaths of solar panels, but that is not practical for human habitats on the moon, where the cold, dark night lasts two weeks, or on Mars, where the sun is farther away and dimmer.

Nuclear reactors would also enable faster and more efficient propulsion systems.

Putting radioactive energy sources in space is not unusual. The Voyager 1 and Voyager 2 space probes, which are still operating after launching in 1977, are powered by plutonium, with the heat of natural radioactive decay turned into electricity. The plutonium heat initially generated 470 watts. In the decades since, the power output has dwindled to about 225 watts.

But the plutonium power sources on the Voyagers are more like batteries than nuclear power plants on Earth. Fission -- the chain-reaction splitting of atoms like uranium -- releases much more energy than solar panels and the power sources on the Voyagers.

This is what Duffy's order aims to harness.

"The Secretary has made it very clear in his new role as acting administrator that we need to go bigger and bolder than what we did with Apollo," said a senior NASA official, who spoke on the condition of anonymity to discuss the background of Duffy's directive.

"Everything needs power," the official said.

A reactor and a kilogram of uranium would be able to produce "as much energy as a freight train full of coal," said Bhavya Lal, a former associate administrator for technology, policy, and strategy at NASA. Lal recently wrote a white paper that argued for a demonstration of a nuclear reactor in space by 2030 with Roger Myers, a former executive at Aerojet Rocketdyne. "That changes the paradigm."

How would a nuclear reactor on the moon work?

A reactor on the moon would not operate in quite the same way as one on Earth.

For one, it has to be small enough and light enough to fit inside a rocket. Safety precautions would include not turning the reactor on until it reached the moon

On the moon, there is also no water or air. The surface swings between 250 degrees Fahrenheit during the day and minus 400 degrees at night. Those make it more difficult to manage the reactor's temperature to keep it operating efficiently. Proposed designs of lunar reactors typically include large radiators to dissipate heat.

Kevin Au, the vice president of lunar exploration at Lockheed Martin, said the biggest challenge of a higher-power reactor would be developing materials that could survive hotter temperatures for use in the conversion of heat to electricity.

Still, experts say building such a power source falls within what is realistically possible.

"It's not science fiction," said Sebastian Corbisiero, a senior program manager at Idaho National Laboratory who leads the Energy Department's space reactor program. "This is very doable."

How feasible is the lunar reactor plan?

However, building a reactor and launching it by 2030 seems unrealistic to some outside experts. They also call it somewhat perplexing because NASA is not currently planning anything on the lunar surface that would require a reactor there that soon.

"It's just a very aggressive, frankly unrealistic timeline for something that is good and should happen," said Kathryn Huff, a former nuclear energy official at the Department of Energy who is now a professor of nuclear, plasma and radiological engineering at the University of Illinois at Urbana-Champaign. "My understanding is that its intent was to power an outpost. So it feels a little silly to do so without an outpost."

Beyond the necessary work to design and build a lunar reactor, navigating the regulatory approvals for launching one would take a couple of years, Huff said.

The NASA official said the 2030 date aims to provide focus and motivation.

"Urgency is the name of the game," the official said. "If we put it too far in the future, we're not going to achieve it, right?"

Duffy's directive also cites plans by China and Russia to build a nuclear reactor for a lunar base near the moon's south pole. The fear is that a keep-out zone around the reactor could limit what the United States could do on the moon.

The official declined to say how much money would be devoted to the program, but said it could be in the hundreds of millions of dollars, or more than $1 billion.

Who might build a nuclear reactor for NASA?

In 2022, NASA, along with the Idaho laboratory, awarded contracts for initial design studies for a lunar reactor that would produce 40 kilowatts. Those small-scale efforts were led by Lockheed Martin, which has built many of NASA's spacecraft; Westinghouse, a heavyweight in the nuclear power industry; and a collaboration between two startups, Intuitive Machines and X-energy.

All three studies failed to fit their reactor designs within the goal of weighing less than 6 metric tons.

"The technology does not exist to do that," said Vincent Bilardo, executive director of the nuclear space program at Intuitive Machines, which twice has landed small spacecraft on the moon. "It's more like a 9- to 10-metric-ton system at that 40-kilowatt power level."

A fission system producing 100 kilowatts would probably be more massive. For the reactor itself, "it's not that huge of a change," said John Kennedy, who leads the space nuclear program at X-energy.

But other pieces like the radiation shielding and the apparatus for converting heat to electricity would have to be larger, Kennedy said.

Duffy's directive, however, says the lander taking the reactor to the surface would have a payload capacity of 15 metric tons.

No such spacecraft currently exists, but cargo versions of the two landers that are being developed to take astronauts to the moon's surface -- SpaceX's Starship and Blue Origin's Blue Moon -- would meet that requirement.

Both Bilardo of Intuitive Machines and Au of Lockheed Martin said their companies would bid for the NASA contracts. Other companies could also submit proposals.

"We're glad to see this coming out," Au said. "This is right in line with our strategies."