{"id":21107,"date":"2026-04-14T12:05:50","date_gmt":"2026-04-14T12:05:50","guid":{"rendered":"https:\/\/ideainthebox.com\/index.php\/2026\/04\/14\/nasa-nuclear-powered-spacecraft\/"},"modified":"2026-04-14T12:05:50","modified_gmt":"2026-04-14T12:05:50","slug":"nasa-nuclear-powered-spacecraft","status":"publish","type":"post","link":"https:\/\/ideainthebox.com\/index.php\/2026\/04\/14\/nasa-nuclear-powered-spacecraft\/","title":{"rendered":"NASA is building the first nuclear reactor-powered interplanetary spacecraft. How will it work?"},"content":{"rendered":"
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MIT Technology Review Explains: Let our writers untangle the complex, messy world of technology to help you understand what\u2019s coming next.\u00a0<\/em>You can read more from the series here<\/em><\/a>.<\/em><\/p>\n

Just before Artemis II began its historic slingshot around the moon, Jared Isaacman, the recently confirmed NASA administrator, made a flurry of announcements<\/a> from the agency\u2019s headquarters in Washington, DC. He said the US would soon undertake far more regular moon missions and establish the foundations for a base at the lunar south pole before the end of the decade. He also affirmed the space agency\u2019s commitment to putting a nuclear reactor on the lunar surface.<\/p>\n

These goals were largely expected\u2014but there was still one surprise. Isaacman also said NASA would build the first-ever nuclear reactor-powered interplanetary spacecraft and fly it to Mars by the end of 2028. It\u2019s called the Space Reactor-1 Freedom, or SR-1 for short. \u201cAfter decades of study, and billions spent on concepts that have never left Earth, America will finally get underway on nuclear power in space,\u201d he said at the event. \u201cWe will launch the first-of-its-kind interplanetary mission.\u201d<\/p>\n

A successful mission would herald a new era in spaceflight, one in which traveling between Earth, the moon, and Mars would\u2014according to a range of experts\u2014be faster and easier than ever. And it might just give the US the edge in the race against China\u2014allowing the country to beat its greatest geopolitical rival<\/a> to landing astronauts on another planet.<\/p>\n

While experts agree the timeline is extremely tight, they\u2019re excited to see if America\u2019s space agency and its industry partners can deliver an engineering miracle. \u201cYou wake up to that announcement, and it puts a big smile on your face,\u201d says Simon Middleburgh<\/a>, co-director of the Nuclear Futures Institute at Bangor University in Wales.<\/p>\n

Little detail on SR-1 is publicly available, and NASA\u2019s own spaceflight researchers did not respond to requests for comment. But MIT Technology Review<\/em> spoke to several nuclear power and propulsion experts to find out how the new nuclear-powered spacecraft might work.<\/p>\n<\/p>\n

Nuclear propulsion 101<\/h3>\n

Traditionally, spaceflight has been powered by chemical propulsion. Liquefied hydrogen and liquefied oxygen are mixed, and then ignited, within a rocket; the searingly hot exhaust from this explosion is ejected through a nozzle, which propels the rocket forth.<\/p>\n

Chemical propulsion offers a significant amount of thrust and will, for the foreseeable future, still be used to launch spacecraft from Earth. But nuclear propulsion would enable spacecraft to fly through the solar system for far longer, and faster, than is currently possible.\u00a0<\/p>\n

\u201cYou get more bang per kilogram,\u201d says Middleburgh. A nuclear fuel source is far more energy-dense than its conventional cousin, which means it\u2019s orders of magnitude more efficient. \u201cIt\u2019s really, really, really high efficiency,\u201d says Lindsey Holmes<\/a>, an expert in space nuclear technology and the vice president of advanced projects at Analytical Mechanics Associates, an aerospace company in Virginia.\u00a0<\/p>\n

The approach also removes one other element of the traditional power equation: solar. Spacecraft, including the Artemis II mission\u2019s Orion<\/a> space capsule, often rely on the sun for power. But this can be a problem, since it doesn\u2019t always shine in space, particularly when a planet or moon gets in its way\u2014and as you head toward the outer solar system, beyond Mars, there\u2019s just less sunlight available.\u00a0<\/p>\n

To circumvent this issue, nuclear energy sources have been used in spacecraft plenty of times before\u2014including on both Voyager missions<\/a> and the Saturn-interrogating Cassini<\/a> probe. Known as radioisotope thermoelectric generators, or RTGs<\/a>, these use plutonium, which radioactively decays and generates heat in the process. That heat is then converted into electricity for the spacecraft to use. RTGs, however, aren\u2019t the same as nuclear reactors; they are more akin to radioactive batteries\u2014more rudimentary and considerably less powerful.<\/p>\n

So how will a nuclear-reactor-powered spacecraft work?\u00a0<\/p>\n

Despite operational differences, the fundamentals of running a nuclear reactor in space are much the same as they are on Earth. First, get some uranium fuel; then bombard it with neutrons. This ruptures the uranium\u2019s unstable atomic nuclei, which expel a torrent of extra neutrons\u2014and that rapidly escalates into a self-sustaining, roasting-hot nuclear fission reaction. Its prodigious heat output can then be used to produce electricity.<\/p>\n

Doing this in space may sound like an act of lunacy, but it\u2019s not: The idea, and even a lot of the basic technology, has been around for decades. The Soviet Union sent dozens of nuclear reactors into orbit (often to power spy satellites), while the US deployed just one, known as SNAP-10A<\/a>, back in 1965\u2014a technological demonstration to see if it would operate normally in space. The aim was for the reactor to generate electricity for at least a year, but it ran for just over a month before a high-voltage failure in the spacecraft caused it to malfunction and shut down.\u00a0<\/p>\n

Now, more than half a century later, the US wants its second-ever space-based nuclear reactor to do something totally different: power an interplanetary spacecraft.<\/p>\n

To be clear, the US has started, and terminated, myriad programs<\/a> looking into nuclear propulsion. The latest casualty was DRACO, a collaboration between NASA and the Department of Defense, which ended<\/a> in 2025. Like several previous efforts, DRACO was canceled<\/a> because of a mix of high experimentation costs, lower prices for conventional rocket propulsion, and the difficulty of ensuring that ground tests could be performed safely and effectively (they are creating an incredibly powerful nuclear reaction, after all).<\/p>\n

But now external considerations may be changing the calculus. The Artemis program has jump-started America\u2019s return to the moon, and the new space race has palpable momentum behind it. The first nation to deploy nuclear propulsion would have a serious advantage navigating through deep space.\u00a0<\/p>\n

\u201cI think it\u2019s a very doable technology,\u201d says Philip Metzger<\/a>, a spaceflight engineering researcher at the Florida Space Institute. <\/strong>\u201cI\u2019m happy to see them finally doing this.\u201d<\/p>\n

One version of this technology is known as nuclear thermal propulsion, or NTP. You start with a nuclear reactor, one that\u2019s cooking at around 5,000\u00b0F. Then \u201cyou\u2019ve got a cold gas, and you squirt cold gas over the hot reactor,\u201d says Middleburgh. \u201cThe gas expands, you shoot it out the back of a nozzle, and you have an impulse. And that impulse drives you forward.\u201d\u00a0<\/p>\n

Because the thrust depends on the speed of the gas being ejected, the propellant gas needs to be light, making hydrogen a popular choice. But hydrogen is a corrosive and explosive substance, so using it in NTP engines can make them precarious to operate. On top of this, NTP doesn\u2019t necessarily have a very long operating life.<\/p>\n

Alternatively, there\u2019s nuclear electric propulsion, or NEP, which \u201cis very low thrust, but very efficient, so you can use it for a long period of time,\u201d says Sebastian Corbisiero<\/a>, the US Department of Energy\u2019s national technical director of space reactor programs. This method uses heat from a fission reactor to generate power. That power is used to electrify a gas and then\u00a0 blast it out of the spacecraft, generating thrust.\u00a0\u00a0<\/p>\n

Both NTP and NEP have been investigated by US researchers, because both have the added benefit of making it easier and safer for human beings to explore the solar system. Astronauts in space are exposed to harmful cosmic radiation, but because nuclear propulsion makes spacecraft speedier and more agile, they\u2019d spend less time in it. \u201cIt solves the radiation problem,\u201d says Metzger. \u201cThat\u2019s one of the main motivations for inventing better propulsion to and from Mars.\u201d<\/p>\n<\/p>\n

How to build a nuclear-powered spaceship<\/h3>\n

For SR-1, NASA has opted for nuclear electric propulsion. NEP is \u201ca much simpler affair\u201d than its thermal counterpart, says Middleburgh. Essentially, you just need to plug a nuclear reactor into a power-and-propulsion system. Luckily for NASA, it\u2019s already got one.<\/p>\n

For many years, NASA\u2014along with its space agency partners in Canada, Europe, Japan, and the Middle East\u2014was preparing for Gateway<\/a>, meant to be humanity\u2019s first space station to orbit around the moon. Isaacman canceled the project in March, but that doesn\u2019t mean its technology will go to waste; the power-and-propulsion element of the nixed space station will be used in SR-1 instead. This contraption was going to be powered by solar energy. It\u2019ll now be attached to an in-development nuclear reactor custom built to survive in space.<\/p>\n

What might the SR-1 look like? MIT Technology Review<\/em> saw a presentation by Steve Sinacore<\/a>, program executive of NASA\u2019s Space Reactor Office, that offers some clues. So far, the concept art makes it look like a colossal fletched arrow. At the back will be the power-and-propulsion system, while its tip will hold a 20-kilowatt-or-greater uranium-filled nuclear reactor. (For context, a typical nuclear plant<\/a> on Earth is 50,000 times more powerful, producing a gigawatt of power.)\u00a0<\/p>\n

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Annotated diagram of the key systems of SR-1 Freedom. Indicated at the front is the power and propulsion element, up to 48kw Advanced electric propulsion system. Panels at the middle are high performance, light weight composite and titanium heat rejection system. At the tail there is indicated an advanced closed Brayton cycle power conversion system and a .20kWe Reactor with HALEU UO2 fuel, heat pipe thermal transfer and boron carbide radiation shield. A small attachment at midcraft is labelled. :High Rate Direct to Earth Communications.\"<\/p>\n
NASA<\/div>\n<\/figure>\n<\/div>\n

The \u201cfletches\u201d on SR-1 are large fins that allow the reactor to cool down. \u201cYou have to have really large radiators,\u201d says Holmes, since the nuclear fission process produces so much heat that much of it has to be vented into space\u2014otherwise, the reactor and spacecraft will melt.<\/p>\n

According to that presentation, the spacecraft\u2019s hardware development is due to start this June. By January 2028, SR-1\u2019s systems should be ready for assembly and testing. And by that October, the spacecraft will arrive at the launch site, ready for liftoff before the year\u2019s end. Will the nuclear reactor manage to hold itself together? \u201cGoing through the launch safely is going to be a challenge,\u201d says Middleburgh. \u201cYou are being shaken, rattled, and rolled.\u201d\u00a0<\/p>\n

Then, he says, \u201conce you\u2019re up in space, once you\u2019ve got through that few minutes of hell in getting there, it\u2019s zero-gravity considerations you have to worry about.\u201d The question then becomes: Will the mechanics of the reactor, built on terra firma, still work?\u00a0<\/p>\n

For safety reasons, the nuclear reactor will be switched on around two days post-launch, when it\u2019s comfortably in space. Uranium isn\u2019t tremendously dangerous by itself, but that can\u2019t be said of the nuclear waste products that emerge when the reactor is activated, so you don\u2019t want any of that to fall back to Earth.\u00a0<\/p>\n

If this schedule is adhered to, and SR-1 works as planned, it\u2019s expected to reach Mars about a year after launch. \u201cIt\u2019s an aggressive timeline,\u201d says Holmes, something she suspects is being driven partly by China\u2019s and Russia\u2019s own deep-space nuclear ambitions<\/a>. The two countries aim to place their own nuclear reactor on the moon\u2019s surface to power the planned International Lunar Research Station\u2014a jointly operated lunar base\u2014by 2035.\u00a0<\/p>\n

Whether it flies or fails in space, SR-1\u2019s operations should help NASA with putting a nuclear reactor on the moon soon after. \u201cAll of the things we\u2019d be learning about how that system operates in space [are] very helpful for a surface application, because basically it\u2019s the same,\u201d says Corbisiero. \u201cThere\u2019s still no air on the moon.\u201d<\/p>\n

And if SR-1 does triumph, it will be a game-changing victory for NASA. It will also be \u201ca massive win for the human race, frankly,\u201d says Middleburgh. \u201cIt will be a marvel of engineering, and it will move the dial in humans potentially taking a step on Mars.\u201d Like many of his colleagues, including Holmes, he remains thrilled by the prospect of the first-ever nuclear-powered interplanetary spacecraft\u2014even with the incredibly ambitious timeline.\u00a0<\/p>\n

\u201cThese are the things that get us up in the morning,\u201d he says. \u201cThese are the sorts of things we will remember when we\u2019re old.\u201d<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

MIT Technology Review Explains: Let our writers untangle the complex, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"content-type":"","footnotes":""},"categories":[226],"tags":[],"class_list":["post-21107","post","type-post","status-publish","format-standard","hentry","category-technology"],"acf":[],"_links":{"self":[{"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/posts\/21107","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/comments?post=21107"}],"version-history":[{"count":0,"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/posts\/21107\/revisions"}],"wp:attachment":[{"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/media?parent=21107"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/categories?post=21107"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ideainthebox.com\/index.php\/wp-json\/wp\/v2\/tags?post=21107"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}