Starlink vs. a nuclear blast in space: 98% of satellites lost in a week

They chose that spot on purpose. The South Atlantic Anomaly is a region with elevated radiation. Electrons released there would spread along compact magnetic shells that overlap with orbits satellites use heavily.

The blast itself is only part of the damage. Radiation, collisions between debris and atmospheric drag all add to it.

How fast would satellites fail?

According to the analysis, 25 percent of satellites would be out after 24 hours and half after 1.9 days. After 4.1 days, 90 percent would be gone, and after 15 days 99.4 percent. Dead satellites cannot dodge anything, so the team expects around 20 collisions within two years. Replacement satellites would face radiation and debris for years. The lowest-flying dead satellites would be dragged down by the atmosphere and fall.

The assumed yield is roughly two thirds of Starfish Prime, the US hydrogen bomb test of 1962. That 1.4 megaton blast, fired at 400 kilometres altitude, remains the strongest in the upper atmosphere or beyond. Seven satellites failed in the following months, and the radiation dose was a hundred times higher than expected. Far fewer satellites were up there back then.

Why this matters now

The 1967 Outer Space Treaty bans stationing nuclear weapons in orbit. Still, signs are piling up that states are working on it. In early 2024 the US government briefed Congress and European allies on Russian progress toward a space-based nuclear weapon. In September this year it emerged that the US has also placed weapons in space, though nuclear ones were not mentioned, and the treaty does not explicitly ban conventional arms.

Starlink has made the scenario more relevant. The satellite internet has proved a strategic advantage for Ukraine against Russia, and it is hard to attack because it has no single point of failure. A blast in orbit would not need one.