Why a Russian nuclear weapon in space could be so devastating

In 1962, the US conducted the largest nuclear test in outer space. The effects were far more devastating than the Pentagon had imagined and brought about a treaty that banned the deployment of nuclear weapons in space.

In the test, known as Starfish Prime, a 1.4 megaton nuclear weapon was detonated 250 miles above the Earth’s surface in the Pacific.

In an instant, an electromagnetic pulse - a brief burst of energy - knocked out hundreds of streetlights in Hawaii, some 900 miles away.

But it was in space where the most powerful effects were felt. Within minutes, the blast had created a fireball and a glowing red aurora clearly visible to observers hundreds of miles below.

Unexpectedly, energetic electrons released during the high-altitude nuclear blast became trapped by the Earth’s magnetic field, forming radiation belts that lingered for several months after the detonation. As they travelled around the planet, these destroyed or damaged one third of all satellites in low orbit at the time, including some that were located at the other side of the earth. Among those damaged was the UK’s first orbital satellite, Ariel One.

It is partly this experience that has driven the alarm at reports that Russia is developing a new space-based anti-satellite (ASAT) weapon. While insiders familiar with the classified information state that the weapon system is still under development and has not been deployed in orbit, it is said to include a nuclear component.

The precise nature of this nuclear component remains uncertain. Two prevailing theories suggest that Russia is either developing a nuclear-armed or a nuclear-powered ASAT capability.

The prospect of a nuclear-armed anti-satellite weapon raises questions as to what it exactly it could be used for militarily. Russia has demonstrated in the past its capability to conduct conventional strikes against satellites. In November 2021, Moscow was widely condemned for carrying out a conventional ASAT test which produced so much space debris it posed a temporary threat to the International Space Station.

In theory, detonating a nuclear weapon in space could provide the advantage of swiftly disabling a large part of the adversary’s satellites in one decisive blow. This is because the electromagnetic pulse (EMP) that is produced as a side-effect of a nuclear detonation can permanently disable electrical and electronic equipment across a relatively vast area, especially if the nuclear device is detonated at high altitude.

Although it is possible to harden satellites to withstand bombardment of charged particles released during high-altitude nuclear detonations, only a relatively small portion of military-grade satellites currently in orbit have undergone such hardening measures. The vast majority of commercial satellites in low Earth orbit, critical to economic activities, incorporate standard electronics into their payloads that render them vulnerable to these kinds of attacks, rendering Western states vulnerable to these kinds of attacks.

The second option, the deployment of a nuclear-powered ASAT weapon that utilises lasers or particle beams to destroy its targets could, in theory, offer the same benefits, while avoiding some of the associated risks. This approach might enable Russia to threaten larger constellations of micro-satellites, such as those that make up Elon Musk’s Starlink internet system, without generating excessive space debris and radiation, and avoid the potentially self-harming effects of a nuclear detonation.

The Soviet Union and its successor state are known to have worked on nuclear-powered “space tugs” that could theoretically be equipped with electronic warfare capabilities, including electromagnetic energy weapons that might prove effective against satellites. However, it remains uncertain whether Russia has had the capacity to invest in such technology  after two years of high-intensity land-warfare in Ukraine and a strict sanction regime that continues to undermine its technological base.

This implies that while Russia may potentially have the capability to deploy a space-based nuclear warhead in the not-so-distant future, deploying a sophisticated nuclear-propelled electromagnetic weapon system in space will be much more difficult to achieve.

Regardless, if an active weapon system were to be deployed in space, it would represent a major escalation and a clear violation of the 1967 Outer Space Treaty, to which Russia is a signatory. 

The revelation also highlights Russia’s continued willingness to disrupt and destabilise the political environment in pursuit of perceived advantages. With a space-based and potentially nuclear ASAT weapon, Moscow would have the option to release a devastating attack on Nato at any moment - a significant piece of leverage that could prevent the bloc from reacting decisively against a land-attack on an alliance member.

 That, however realistic, might be the threat Vladimir Putin hopes to hang over the heads of the West.

Fabian Hoffman is a doctoral research fellow at the Oslo Nuclear Project.