July 9, 1962 – 250 miles above uninhabited Johnston Island – a Pacific atoll between Hawaii and the Marshall Islands – America detonated a nuclear warhead. As part of “Operation Fishbowl”, this wasn’t their first high altitude nuclear rodeo. High altitude nuclear testing began in 1958. six detonations that year raised more questions than answers. Hardly surprising poor instrumentation and inconclusive data, frustrated scientists on the forefront of nuclear exploration.
“Previous high-altitude nuclear tests: YUCCA, TEAK, and ORANGE, plus the three ARGUS shots were poorly instrumented and hastily executed. Despite thorough studies of the meager data, present models of these bursts are sketchy and tentative. These models are too uncertain to permit extrapolation to other altitudes and yields with any confidence. Thus there is a strong need, not only for better instrumentation, but for further tests covering a range of altitudes and yields.” – Defense Atomic Support Agency interim report on Starfish Prime, August 1962
Just after 11 PM Honolulu time July 9, 1962, Thor (the first USAF ballistic missile) unleashed Starfish Prime – Thor traveled almost 700 miles straight up before puttering out, as it fell towards Earth – at precisely 13 minutes 41 seconds after launch – a programmed detonation took place around the 250 mile mark.
The question of how Earth’s magnetosphere reacts to thermonuclear assault became clear. The EMP (electromagnetic pulse) sent instruments off the scale, 900 miles away in Hawaii streetlights blew, burglar alarms sounded and a damaged telephone microwave link knocked out phone service between Kauai and other Hawaiian Islands. Auroras illuminated thousands of miles over the Pacific – according to a U.S. Defense Report, the New Zealand Navy on anti-submarine maneuvers, took advantage of light from the blast. Starfish created a “radiation belt” – initially 3 “low earth orbiting” satellites went dark, ultimately a third of all “low earth” satellites clocked out. It would be 5 years before Starfish electrons completely left our atmosphere.
Starfish Prime was the last high altitude nuclear event – science wasn’t prepared for such a powerful EMP, further detonations would have been folly. A clever decision to place tracer isotopes in the package, allowed science to map polar and tropical air masses.