Just before the Artemis II crew began its historic slingshot around the moon this past April, NASA announced plans to build Space Reactor-1 Freedom. SR-1, the first-ever nuclear-reactor-powered interplanetary spacecraft, is meant to fly an uncrewed mission to Mars by the end of 2028, arriving in 2029. A successful mission would herald a new era of more efficient, potentially faster spaceflight, saving astronauts time and cutting their exposure to harmful cosmic radiation. "You wake up to that announcement, and it puts a big smile on your face," says Simon Middleburgh, co-director of the Nuclear Futures Institute at Bangor University in Wales.
Running a nuclear reactor in space may sound like lunacy, but experts say there are no major technical obstacles. The Soviet Union sent dozens of reactors into orbit, often to power spy satellites. "I think it's a very doable technology," says Philip Metzger of the Florida Space Institute. Still, the US has started and terminated several such programs over the past 75 years, most recently DRACO, which ended in 2025 due to high costs, an inability to compete on price with conventional rockets, and difficulty performing ground tests safely.
Now, nuclear-powered interplanetary travel appears to be a $2 billion bet NASA is willing to make. The agency is pursuing nuclear electric propulsion, which uses heat from a uranium-splitting reaction to generate electricity. That electricity ionizes a gas, which is blasted out of the spacecraft with magnetic fields to generate thrust. The approach "is very low thrust, but very efficient," says Sebastian Corbisiero of the US Department of Energy. The craft's concept art resembles a colossal fletched arrow, with a reactor of at least 20 kilowatts in the tip and large fins that radiate heat into space.
The reactor will be switched on about two days after launch, once it is safely far from Earth. If SR-1 works as planned, its journey to Mars will take about a year. NASA says Idaho National Laboratory, which is building the reactor, is on target for a late-2028 launch. "Procurement of major components is underway," said program director Steve Sinacore.
Source: MIT Technology Review · Summarized by HeadlinesBriefing