Ah those wonderful 1960s, when Mad Men roamed the streets, everything was possible and the sky the limit. Looking back from an age when every children’s playground or bicycle path is subject to environmental impact assessment regulations, the Starfish Prime nuclear test seems almost like from a different planet.

The Starfish Prime test on 9 July 1962 was one of a series of five in the Operation Fishbowl series aimed at testing the effects of nuclear weapons in high altitudes and lower outer space. The warhead was launched with a missile to around 400 kilometres height, where it detonated with a yield of 1.45 megatons – approximately a hundred times that of the Hiroshima bomb.

One of the main aims of the test was to see how a nuclear explosion would affect the Van Allen Radiation Belt – bands of high-energy protons and electrons that follow the Earth’s natural magnetic field.

The belts had only recently been discovered before by a group of U.S. scientists under the direction of Dr. James Van Allen. Surprisingly, he agreed to cooperate with the U.S. military in setting up the test – on the very same day as he held a press conference to announce his discovery as his biographer, science historian James Fleming found out.

Fleming commented

“this is the first occasion I’ve ever discovered where someone discovered something and immediately decided to blow it up.”

The consequences for the magnetosphere were completely unpredictable at the time. Also its crucial role in shielding all life on Earth from solar winds was not understood until later. The Starfish Prime test resulted in a temporary alteration of the shape and intensity of the lower Van Allen belt, which created artificial aurora borealis that could be seen across the Pacific Ocean, from Hawaii to New Zealand.

Video footage from the test:

The test also revealed the destructive impact of the Electromagnetic Pulse produced by a nuclear explosion. Located at more than 1,300 kilometers from the test site, the Hawaiian Island of Oahu received a power surge that knocked out numerous electric devices. The radiation from this and other high-altitude nuclear tests also created an artificial radiation belt that, together with the EMPs, damaged or destroyed as many as one third of the satellites in lower earth orbit at the time.

The result is eloquently described by Robert Krulwich in his NPR piece A Very Scary Light Show: Exploding H-Bombs In Space.

The surprise at these unforeseen consequences and concerns for the safety of astronauts in the nascent space travel led to a reduction in the yield of further outer space tests, which were banned by the 1963 Partial Test Ban Treaty.

Read more on the Van Allen Radiation belts.