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Starfish Prime Interim Report By Commander JTF-8
1.4 Mt · Jul 9, 1962 · Johnston Island · 93 Hiroshimas
Part of Operation Dominic, Starfish Prime was a 1.4-megaton warhead detonated on 9 July 1962 at an altitude of 250 miles above Johnston Island — a deliberate high-altitude nuclear test. It lit an artificial aurora seen across the Pacific and produced an electromagnetic pulse that reached Hawaii.
The EMP knocked out streetlights, tripped burglar alarms and damaged telephone equipment 900 miles away in Honolulu. The blast pumped the Earth's magnetic field with charged particles, creating artificial radiation belts that crippled or destroyed at least six satellites over the following months — the first demonstration that a nuclear weapon in space could disable the technology below.