Here is NASA's plan for nuking Gateway and sending it to Mars - Ars Technica

Overview

Here is NASA’s plan for nuking Gateway and sending it to Marsvar abtest_2146874 = new ABTest(2146874, 'click');

Only one US-built nuclear reactor has ever flown in space, and that was more than 60 years ago.

Details

NASA’s announcement Tuesday that it will “pause” work on a lunar space station and focus on building a surface base on the Moon was no big surprise to anyone paying attention to the Trump administration’s space policy.

But what should NASA do with hardware already built for the Gateway outpost? NASA spent close to $4.5 billion on developing a human-tended complex in orbit around the Moon since the Gateway program’s official start in 2019. There are pieces of the station undergoing construction and testing in factories scattered around the world.

The centerpiece of Gateway, called the Power and Propulsion Element, is closest to being ready for launch. NASA’s rejigged exploration roadmap, revealed Tuesday in an all-day event at NASA headquarters in Washington, calls for repurposing the core module for a nuclear-electric propulsion demonstration in deep space.

This is not the first time NASA has announced a nuclear propulsion demo. More than 20 years ago, NASA was working on a nuclear-electric propulsion initiative called Project Prometheus. It was canceled. In 2021, NASA and DARPA, the Pentagon’s research and development agency, started work on a nuclear rocket engine known as DRACO. NASA and the Pentagon canceled the DRACO program last year.

Like on Gateway, NASA and other agencies have spent billions of dollars on nuclear power and propulsion in space, with little to show for it. There are good reasons for using this technology. Nuclear power enables more ambitious robotic missions deeper into the Solar System, where the Sun’s energy is not sufficient to generate electricity. Closer to Earth, nuclear reactors on the Moon can be used to power habitats, robots, and lunar bases during the two-week-long lunar night.

Nuclear-powered rocket engines are more efficient than chemical rockets. They come in two forms: nuclear-thermal and nuclear-electric engines. Nuclear-thermal rockets produce higher thrust, using heat from a reactor to heat up a chemical rocket fuel. Nuclear-electric engines have lower thrust but greater efficiency. The now-canceled DRACO mission would have used the former approach. NASA’s new nuclear mission will use the latter.

“We will launch the first-of-its-kind interplanetary mission called SR-1 Freedom before the end of 2028, demonstrating fission power and the extraordinary capabilities to move mass efficiently in space,” said NASA Administrator Jared Isaacman.

NASA will cannibalize the core module of Gateway for the SR-1 mission. The Power and Propulsion Element, or PPE, is under construction at Lanteris Space Systems in Palo Alto, California. The module will have the most powerful electric propulsion system ever flown in space, with three 12-kilowatt engines and four 6-kilowatt thrusters. The PPE would have originally relied entirely on solar power. Under NASA’s new plan, it will have solar arrays and a uranium-fueled fission reactor.

The goal for SR-1 Freedom is to “prove the US can build, launch, and operate a nuclear propulsion system,” laying the “foundation” for more capable missions to follow, said Steve Sinacore, NASA’s program executive for space reactors. Launch is just 33 months away.

NASA officials present the SR-1 Freedom mission at NASA Headquarters in Washington on March 24, 2026.

There are reasons NASA has never launched a nuclear propulsion mission before. Past efforts aimed too high, with complicated designs and bonus science objectives that ballooned their costs and dragged out their schedules. Other projects, like DRACO, had convoluted management structures with multiple government agencies claiming ownership.

Only one US-built nuclear reactor has ever flown in space, and that was more than 60 years ago. “The lack of an operational space nuclear reactor is not a technology problem, it’s an execution problem,” Sinacore said.

SR-1, short for Space Reactor-1, will take a smaller bite at solving the nuclear power challenge in space. It will have a roughly 20-kilowatt fission reactor, a fraction of the power levels NASA aimed to achieve with the first mission for Project Prometheus before its cancellation. This is still 20 times more electricity than the nuclear power generators currently operating in deep space, such as on NASA’s Mars rovers and the Voyager probes leaving the Solar System.

NASA is already working with commercial nuclear reactor developers to provide power on the lunar surface. Lockheed Martin and BWX Technologies were developing the reactor to fly on the DRACO mission before its cancellation last year. One thorny problem that cursed the DRACO mission was the question of how to test a nuclear thermal rocket engine on Earth while adhering to nuclear safety protocols. This would require engine exhaust to be scrubbed of radiological material. Managers found there’s no easy, inexpensive way of doing that.

In addition to efficiency, a nuclear-electric propulsion system has the benefit of using conventional plasma thrusters. But instead of using solar power to energize the thrusters’ xenon fuel, SR-1 will use electricity generated from a nuclear reactor.

“Our nuclear program, SR-1, is not about going and lobbying for billions of dollars to undertake a brand-new mission,” Isaacman said. “Honestly, we haven’t won the right to be able to do that after $20 billion worth of failed programs over time. This is why we’re taking hardware that we already have, a reactor that’s mostly built, fuel that’s mostly paid for over time.”

Gateway’s Power and Propulsion Element, seen here under construction last year, will form the centerpiece of the SR-1 Freedom mission.

NASA officials did not disclose an estimated cost for the SR-1 mission.

After proving nuclear propulsion works, “then you can come back and maybe ask for more [funding] in the future when you show that it can be done,” Isaacman said.

“SR-1 Freedom primarily has that one new system, the reactor, on a spacecraft bus that already exists,” Sinacore said. “The timeline will match the need with the next Mars launch window in December 2028. Orbital mechanics does not negotiate, and the scope must bend around this deadline.”

There are still some hurdles that won’t be easy to jump. Readying any large space mission, especially one as novel as a nuclear propulsion demo, for launch in less than three years will require sharp focus, resistance to mission creep, and near-perfect execution. Sinacore laid out an ambitious timeline for SR-1, with mission design complete by June and large-scale assembly beginning at the start of 2028. If the mission misses a launch opportunity in late 2028, the next Earth-Mars alignment won’t happen until early 2031.

“We are not trying to do everything,” Sinacore said. “We are trying to do the hard thing, which is operate a coupled nuclear reactor, power conversion, and electric propulsion thruster system beyond Earth orbit for the first time ever.”

Although NASA will be the “prime integrator” for SR-1, actually launching radioactive fuel into space requires input from multiple federal agencies, including the Department of Energy. Any rocket selected to launch a nuclear-powered mission must undergo a special certification. Space X’s Falcon Heavy, which NASA originally booked to launch the Gateway core module, is undergoing a nuclear certification to launch NASA’s Dragonfly mission to Saturn’s moon Titan.

There is one additional payload that NASA says will ride to Mars with the SR-1 Freedom spacecraft. The mothership will release three flying drones, each based on NASA’s Ingenuity helicopter, to land on Mars and scout future landing sites for human explorers.

These copters, presumably built at NASA’s Jet Propulsion Laboratory, will carry cameras and ground-penetrating radars to scan the Martian terrain for subsurface water ice. They will land themselves on Mars after plunging through the Martian atmosphere.

NASA’s Ingenuity Mars helicopter is seen here in a closeup taken by Mastcam-Z, a pair of zoomable cameras aboard the Perseverance rover.

“After separating from SR-1 Freedom, the entry capsule enters the Martian atmosphere at hypersonic speeds greater than Mach 5, slowing to approximately Mach 2,” Sinacore said. “Next, a supersonic parachute deploys to slow the capsule further, and finally, the heat shield separates and the helicopters are released in a first-ever mid-air deployment.”

NASA isn’t sure what they will do with the SR-1 mothership after reaching Mars. They could try to maneuver it into orbit around the red planet, or slingshot the spacecraft past Mars to head to another planetary destination.

The inclusion of Mars helicopters on the SR-1 mission would bridge a gap in NASA’s Mars landing missions. The agency canceled a robotic Mars Sample Return mission last year due to rising costs, meaning China is likely to be the first country to bring Martian rocks back to Earth.

NASA is contributing to Europe’s Rosalind Franklin rover, also set for launch in late 2028. The US space agency also plans to partner with a commercial provider for a Mars communications relay orbiter that could launch as soon as 2028.

NASA’s Curiosity and Perseverance rovers continue operating on Mars, but there were no US-led Mars landing missions in the agency’s roadmap until this week’s announcement of Skyfall.

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Key Takeaways

• Here is NASA’s plan for nuking Gateway and sending it to Marsvar abtest_2146874 = new ABTest(2146874, 'click');

• Only one US-built nuclear reactor has ever flown in space, and that was more than 60 years ago

• NASA’s announcement Tuesday that it will “pause” work on a lunar space station and focus on building a surface base on the Moon was no big surprise to anyone paying attention to the Trump administration’s space policy

• But what should NASA do with hardware already built for the Gateway outpost

• The centerpiece of Gateway, called the Power and Propulsion Element, is closest to being ready for launch