Could a nuke be used in space? Last month, Russia seemingly took a step toward making the idea a reality. In defiance of a US and Japan-sponsored UN resolution, the country vetoed plans to prevent the development and deployment of off-world nuclear weapons.
Fortunately, the country didn’t actually threaten to launch such a device into space, an act that would violate the 1967 Outer Space Treaty. However, the UN representative for Russia did call the new resolution a “cynical ploy” and claimed “we are being tricked”.
But what would actually happen if Russia – or any other country – detonated a nuke above Earth? The worrying answer: such an explosion could be as devastating as one on ground level.
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What happens if you detonate a nuclear warhead in space?
There are some pretty stark differences between setting off a nuke at ground level and up in orbit.
“When nuclear weapons go off on the ground, a lot of energy is initially released as X-rays,” Dr Michael Mulvihill, vice chancellor research fellow at Teesside University, tells BBC Science Focus.
“Those X-rays superheat the atmosphere, causing it to explode into a fireball – that’s what produces the shockwave and characteristic mushroom cloud that sucks up dirt and produces fallout.”
But in space there is no atmosphere. So no mushroom clouds or shockwaves are formed when you set off a nuke in space. That doesn’t mean the effects are any less terrifying, however.
“In space, a nuclear explosion releases a huge amount of energy as X-rays, gamma rays, intense flows of neutrons and subatomic charged particles. It also produces what’s known as an electromagnetic pulse, or EMP,” Mulvihill says.
An EMP is effectively a burst of electromagnetic energy; when one interacts with the upper atmosphere, it strips electrons from it, blinding radar systems, knocking out communications and wiping out power systems.
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After the initial explosion, a belt of radiation wraps around the Earth that persists for months, possibly even years – no one knows for sure. The radiation can damage satellites and, as Mulvihill points out, would pose a serious risk to anyone in space at the time – such as astronauts on the ISS.
“The EMP would knock out power systems on the ISS, effectively destroying the life support systems and everything that circulates the atmosphere within the space station. And I imagine the astronauts would be exposed to high levels of radiation too,” Mulvihill explains.
“It would be highly hostile to life in orbit.”
Space is becoming more and more crowded with satellites – approximately 10,000 satellites are in low earth orbit right now, and tens of thousands more are planned for launch in the coming years. This significantly raises the stakes of unleashing nuclear energy in space, as we become more reliant on the systems we put into orbit.
From ground level, however, other than blowing power grids and disrupting communications, the effects could also be somewhat beautiful.
As charged particles from the explosion interact with the Earth's magnetic field and the atmosphere, they would cause brilliant auroras, stretching across huge distances that could last for days. So there’s that, at least.
Have nuclear explosions reached space before?
Unsurprisingly, during the Cold War, global superpowers (namely, the US and Russia) tested nukes in just about every scenario imaginable. On land, underwater, in a mountain – you name it, they tried blowing it up.
It comes as no surprise then, that detonating nuclear weapons in space has been done before. In total, the US conducted five space nuclear tests in space; the most famous of which, according to Mulvihill, occurred on 9 July 1962 near(ish) to the Pacific island paradise of Hawaii.
Starfish Prime was launched 400km (250 miles) above Johnston Island and had an explosive power of 1.4 megatons – about 100 times more powerful than the Hiroshima bomb.
The EMP was much larger than expected, compromising the classified nature of the test as streetlights and phone lines were knocked out in Hawaii 1,450 km (900 miles) away from the detonation point.
The ensuing red auroras stretched across the Pacific Ocean and lasted for hours.
“At the time there were around 22 satellites in space, of which around a third were knocked out,” Mulvihill says. The casualties included the world’s first TV communication satellite, Telstar 1, which had been a beacon of US technological development until Starfish Prime caused it to prematurely fail after just seven months in orbit.
In the following years, everyone came to their senses a bit and decided that testing nuclear warheads in space constituted a bad idea. Thus, the Outer Space Treaty (OST) was born.
Signed in 1967 by the US, UK and Soviet Union, the OST now has over 100 signatories and designates space as free for all to use for peaceful purposes only. The world breathed a sigh of relief and got on with using space for nice things like astronomy, space stations and WiFi for the next 60 years. So, what’s changed?
How worried should we be?
Rumours of a change in the orbital security situation began swirling when earlier this year the US House Intelligence Committee chairman Mike Turner issued a vague warning about a “serious national security threat” posed by Russia.
Following this, news outlets began reporting that the threat pertained to a possible “nuclear weapon in space”.
“It’s certainly concerning, but don’t lose sleep over it,” Mulvihill says. “Russia is still a signatory of the OST, so any sort of weapon in space would be absolutely illegal.”
He also points out that as Starfish Prime demonstrated, nuclear weapons in space are indiscriminate, meaning any detonation would do just as much damage to Russia and its allies as anyone else.
“It wouldn’t just knock out Starlink [the SpaceX system of satellites that provides internet to 75 countries]. It would knock out Chinese satellites and everyone else's too.”
Another possibility, Mulvihill thinks, is that countries could develop nuclear-powered 'jammers'. In other words, not a bomb (phew), but something that uses nuclear power to generate a signal that could disrupt, rather than destroy, other satellites.
Ultimately, though, this could all be little more than geopolitical posturing. “Deterrence is all about messaging and trying to persuade somebody that you would do it without ever actually getting there. I think that’s probably the psychology that’s going on with this,” Mulvihill concludes.
About our expert
Michael Mulvihill is a vice chancellor research fellow at Teesside University investigating embodied socio-technical and astro/geopolitical phenomena emerging from nuclear deterrent and space technologies. Additionally, he is an associate convenor of the Military War and Security Research Group and a member of the British International Studies Association Astropolitics Working Group.
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