One Nuclear Blast in Space Could Cripple Nearly Every Low-Orbit Satellite

A single nuclear explosion high above Earth could knock out almost every satellite in low-Earth orbit within a month, according to a new study reported by ScienceAlert. The work, by researchers at the University of Wisconsin–Madison and Princeton University, has not yet been peer-reviewed.

The simulation also points to a longer-term problem: crippled satellites would collide, and the debris could keep growing for decades.

What did the researchers simulate?

The team modeled a 1-megaton nuclear detonation 500 kilometers above the South Atlantic, near a region where Earth's magnetic field is unusually weak, known as the South Atlantic Anomaly. They used the 13,300 satellites that were active in low-Earth orbit as of January this year.

The paper is a preprint posted on arXiv, and its first author is Zach Petersen, a University of Wisconsin–Madison student.

How fast would satellites fail?

In the simulation, the damage builds quickly. About 25 percent of the fleet would be disabled after one day and 78 percent by the end of day three. The figure would reach 98 percent after a week and 99.4 percent by day 15.

Extra radiation shielding would not save the fleet. Even if spacecraft were given strengthened protection, 99.3 percent would be disabled within 30 days. A much weaker 100-kiloton warhead would take a year to neutralize 99 percent of satellites.

Why would a blast in space keep causing damage?

The explosion itself is only the start. The researchers explain that electrons from the radioactive decay of fission products become trapped in Earth's magnetic field and form an artificial radiation belt. Satellites are exposed again and again as they pass through it.

This has happened before. During the Cold War, the United States and the Soviet Union carried out 18 high-altitude nuclear explosions. The largest, Starfish Prime in 1962, detonated a 1.4-megaton warhead at an altitude of 400 kilometers over the Pacific Ocean. Its effects disabled several satellites. A year later, the two countries agreed to suspend above-ground nuclear testing under the Partial Nuclear Test Ban Treaty.

The authors note that a comparable event today would take place in a far more crowded orbital environment.

What would happen to the debris?

Once satellites lose the ability to maneuver, the risk of collisions rises. The researchers estimate about 20 collisions in the first two years. After 10 years, those crashes would leave roughly 3,900 new fragments of space junk circling Earth.

The team writes that continued collisions among long-lived objects are expected to keep producing debris beyond the simulated decade, with a possible slow buildup and eventual runaway growth over centuries.

Why does it matter for everyday life?

More than 13,000 satellites currently orbit in low-Earth orbit, according to ScienceAlert, and they support weather forecasts, telephone and data communications and satellite internet services. Losing nearly all of them would disrupt those services.

Recovery would not be simple either. The authors say restoring orbital services would require more than replacing the lost spacecraft, because new satellites would have to survive the remaining radiation and debris. They argue the prospect of fast infrastructure loss followed by years of disruption reinforces the need to prevent nuclear weapons from being deployed or used in space.

Nuclear policy researcher James McKeon summed up the findings online by calling the scenario very bad and saying everything possible should be done to keep it from happening.

Because the study is a preprint, its results have not yet been checked by independent reviewers, and they come from a simulation rather than an observed event.

Around Prague, based on reporting by ScienceAlert

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