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

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.

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. “T he 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.