On July 9, 1962, the United States launched a Thor rocket armed with a W49 thermonuclear warhead up to an altitude of around two hundred and fifty miles over the Pacific and detonated it. It took thirteen minutes for the missile to reach its predesignated altitude before the 1.45 megaton explosion illuminated the night sky for hundreds of miles in every direction. The missile, designated Starfish Prime, remains the biggest bomb ever detonated in space to this day.
Scientists were poised to study the effects of radiation at high altitudes on Johnston Island below. Twenty-seven smaller rockets were launched alongside Starfish Prime to measure the effects of the detonation, but none of them, nor the scientists involved, were prepared for what would occur as a result of the explosion.
In the near vacuum of space, free electrons were hurled from the explosion in every direction and faced no atmospheric impedance. Instead, they formed a brief but powerful, electromagnetic pulse that caused power outages and other electrical issues on the Hawaiian Islands, nearly a thousand miles away. At least six satellites orbiting near the explosion were lost despite the distance seeming so insurmountable that the U.S. government hadn’t even considered the likelihood of such damage occurring. Scientists had discovered that high altitude detonations of nuclear weapons could disrupt the flow of electricity in devices thousands of miles away from the point of detonation. Starfish Prime was not just a nuclear weapon, it was a weaponized EMP (electromagnetic pulse).
In the scope of threats to our way of life, few things should be more concerning than the prospect of a foreign nation using this method to cripple the infrastructure of the United States. If a 1.45 megaton bomb could knock out electronics a thousand miles away, imagine what a warhead the size of the Soviet Tsar Bomba would do if detonated in low orbit above us. Its 50-megaton yield would render the entire U.S. power grid a thing of the past. Cars wouldn’t start. Phones wouldn’t work. The blackout would be all encompassing and permanent.