I will expand on a story that has recently caught my eye in the media about the possible use of nuclear weapons in outer space. During the Cold War, both the Soviet Union and the United States developed nuclear weapons designed for use in space.

In 1967, the United Nations adopted the Outer Space Treaty, which stipulates that states are not allowed to place nuclear weapons in orbit, on celestial bodies, or station them in outer space in any other way. After that, more attention was paid to nuclear missiles launched from Earth that could be used, if necessary, to destroy space objects. Efforts were also made to develop ground-launched kinetic systems to attack enemy satellites in space.

In 1969, Moscow began developing missiles dubbed "satellite killers," and in the 1970s the program was declared operational. Afterward, research was conducted into using lasers against U.S. satellites, and in 1987 an attempt was made to send such a system into orbit, but it failed.

In 1977, the United States developed its own plans for anti-satellite weapons. It also explored electronic systems aimed at blinding Soviet satellites. With the end of the Cold War, anti-satellite programs were either terminated or at least suspended. Later, several countries were observed testing the destruction of satellites using ground-launched missiles. At present, Russia, the United States, China, and India have the capability to destroy satellites from Earth.

The nuclear issue resurfaced in April 2024, when Russia vetoed a UN Security Council resolution proposed by the United States and Japan that would have reaffirmed the provisions of the 1967 Outer Space Treaty and banned nuclear weapons in space.

Less than a month later, U.S. Assistant Secretary of Defense John Plumb reported to Congress that Russia was preparing to launch a satellite with a nuclear payload into orbit. Its alleged purpose would have been to render low Earth orbit unusable. This discussion was accompanied by calls from some Russian figures to use nuclear weapons in the war in Ukraine or against European countries. Among these statements were suggestions of carrying out a warning detonation in low Earth orbit to disable ground-based electrical and communication systems.

For clarity, there are three orbital zones around Earth in terms of satellites. Low Earth orbit extends from about 100 to 2,000 kilometers. Practically all commercial satellites are located there, and in general about 90 percent of all man-made objects in space.

Above that is medium Earth orbit, extending up to about 36,000 kilometers. This is where satellites that provide navigation systems such as GPS, Europe's Galileo, and Russia's GLONASS are located. The highest is geostationary orbit, above 36,000 kilometers, where weather and television satellites are found, as well as strategic military communication satellites. The most dangerous scenario would be a nuclear explosion in low Earth orbit, as it would disable the largest number of critical space assets.

The issue gained attention two years ago when, in 2022, Russia launched the satellite Kosmos-2553 into orbit. It was placed at an altitude of 2,000 kilometers, at the upper edge of low Earth orbit. This raised questions because, as a rule, satellites are not placed there due to high radiation levels. Earth is surrounded by two permanent radiation belts, known as the Van Allen belts, which trap high-energy particles and protect the planet from solar storms and solar wind.

Thus, the orbit where the Russian satellite was sent is generally used as a "graveyard" for defunct satellites. Although Russia claimed it was conducting scientific research, U.S. intelligence assessed that it was evidence of a Russian anti-satellite nuclear program. According to last year's space threat assessment by the U.S. think tank CSIS, the satellite began rotating irregularly and may no longer be functional. It may also be equipped only with a mock warhead.

Historically, nuclear charges have already been detonated in outer space. In 1962, the Soviet Union conducted a test in which a 300-kiloton warhead was detonated at an altitude of 290 kilometers over Kazakhstan. On the ground, the result was that in a telephone line 570 kilometers from the epicenter, between Zhezkazgan, Karaganda, and Akmola, the current surged to 2,500 amperes. All protective systems reacted, the Karaganda power plant burned out, a 1,000-kilometer underground cable between Akmola and Almaty short-circuited, and radio relay stations up to 1,000 kilometers away were damaged.

The United States detonated a 1.4-megaton device the same year at an altitude of 400 kilometers over the Pacific Ocean. In Hawaii, 1,445 kilometers away, streetlights burned out and inter-island radio communication was disrupted. The electromagnetic pulse destroyed eight of the 24 satellites then in orbit. The radiation levels in orbit, sharply increased by the explosion, remained elevated for several months.

Thus, if a nuclear charge were detonated in low Earth orbit today, one must consider that there are no longer 24 satellites but 16,910 (as of March), of which 14,200 are operational. There are now more than 10,000 Starlink satellites alone.

A nuclear detonation would generate a huge amount of space debris, destroying satellites within an 80-kilometer radius. As the debris spreads, it could strike other satellites and create additional debris, posing a major hazard in orbit. In addition, there is the issue of radiation. Even a relatively small 10–20 kiloton device would immediately affect 5–10 percent of satellites. A strong electromagnetic pulse would also damage onboard electronics. The impact on Earth would depend on the altitude of the explosion.

To circumvent the UN prohibition, Russia could also use satellites powered by nuclear energy sources, in which an "accident" might occur in space — essentially an explosion — after which Moscow could simply claim it was just an accident.

In any case, the threat is real, and in March the U.S. Space Command conducted a staff exercise to respond to the potential threat of a Russian anti-satellite nuclear program. Fortunately, Russia's current capabilities in space programs are fairly limited. But one never knows…

Recommended reading

• New details emerge of Russia's potential nuclear space weapon - Breaking Defense
• Ядерная угроза в космосе — Россия готовит удар с орбиты, под угрозой Starlink / NV
• A Russian nuclear weapon in space? Intel on Putin plan leaves unanswered questions
• Russian Nuclear Sabotage In Space Could Blast U.S., SpaceX Satellites
• A Russian space nuke was focus of US wargame, Space Command says - Defense One
• Russian Nuclear Weapons in Space? - Stiftung Wissenschaft und Politik
• Why Russia Might Put a Nuclear Weapon in Space | Foreign Affairs
• Russian nukes in space: Why a Cold War response will only make it worse - SpaceNews
• NATO Must Respond to the Russian Nuclear Threat in Space
• What Happens if a Nuclear Weapon Goes Off in Space? | Scientific American

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