The first attempts of the Operation Fishbowl tests took place in June 1962, but didn’t succeed, due to radar-tracking issues and rocket-engine malfunction. But on July 9, 1962, the United States found success with its Starfish Prime test, illustrated in the first series of images in this photo essay. The 1.4 megaton bomb—which was sent skyward via a Thor missile, and detonated at an altitude of about 250 miles, at around 10 p.m. local time—yielded an electromagnetic pulse so large, it damaged streetlights, telephone lines and other electronic devices some 900 miles away in Hawaii. (And, reportedly, even further away—in New Zealand.) It also left a radiation belt in its wake that was so substantial, it crippled multiple American and British satellites and caught the attention of administrators at NASA, who became concerned about its potential effects on the space vehicles and astronauts then participating in programs such as Apollo.