On July 9, 1962, the US launched a Thor missile from Johnston island, an atoll about 1500 kilometers (900 miles) southwest of Hawaii. The missile arced up to a height of over 1100 km (660 miles), then came back down. At the preprogrammed height of 400 km (240 miles), just seconds after 09:00 UTC, the 1.4 megaton nuclear warhead detonated.
And all hell broke loose.
It pretty much looks like what you would expect a nuclear explosion in low-earth orbit would look like. Nuclear explosions release huge amounts of radiation, obviously, plus electrons and heavy ions. The electrons basically crashed into the molecules of the atmosphere and created an aurora visible for thousands of miles. Then it got crazier:
But the effects were far more than a simple light show. When the bomb detonated, those electrons underwent incredible acceleration. When that happens they create a brief but extremely powerful magnetic field. This is called an electromagnetic pulse, or EMP. The strength of the pulse was so huge that it affected the flow of electricity on the Earth hundreds of kilometers away! In Hawaii it blew out hundreds of streetlights, and caused widespread telephone outages. Other effects included electrical surges on airplanes and radio blackouts.
The EMP had been predicted by scientists, but the Starfish Prime pulse was far larger than expected. And there was another effect that hadn’t been predicted accurately. Many of the electrons from the blast didn’t fall down into the Earth’s atmosphere, but instead lingered in space for months, trapped by Earth’s magnetic field, creating an artificial radiation belt high above our planet’s surface.
When a high-speed electron hits a satellite, it can generate a sort-of miniature EMP. The details are complex, but the net effect is that these electrons can zap satellites and damage their electronics. The pulse of electrons from the Starfish Prime detonation damaged at least six satellites (including one Soviet bird), all of which eventually failed due to the blast. Other satellite failures at the time may be linked to the explosion as well.
It was far from the biggest nuclear explosion in history. That honor goes to the Tsar Bomba, a Soviet nuclear test in 1961 that clocked in at fifty megatons (after they reduced it from the original one hundred megatons, because that would have been too much, amiright?) It had no realistic military application, since it weighed around twenty-seven tons, so the main goal seemed to be geopolitical big-dick swinging.
An art project by Isao Hashimoto shows every nuclear detonation on Earth from 1945 to 1998. Phil Plait blogged about it a couple years ago and asked the pertinent question: “What the hell were we thinking?”
Photo credit: ‘Starfish5’ by Photocopier at en.wikipedia [Public domain], from Wikimedia Commons.