Johnston Atoll significant event Operation Fishbowl
National nuclear weapon test site 1958–1963
Successes
Between 1958 and 1975, Johnston Atoll was used as an American national nuclear test site for atmospheric and extremely high-altitude nuclear explosions in outer space. In 1958, Johnston Atoll was the location of the two "Hardtack I" nuclear tests firings. One conducted August 1, 1958, was codenamed "Hardtack Teak" and one conducted August 12, 1958, was codenamed "Orange." Both tests detonated 3.8-megaton hydrogen bombs launched to high altitudes by rockets from Johnston Atoll.
Johnston Island was also used as the launch site of 124 sounding rockets going up as high as 1,158 kilometers (720 miles). These carried scientific instruments and telemetry equipment, either in support of the nuclear bomb tests, or in experimental antisatellite technology.
Eight PGM-17 Thor missiles deployed by the U.S. Air Force (USAF) were launched from Johnston Island in 1962 as part of "Operation Fishbowl," a part of "Operation Dominic" nuclear weapons tests in the Pacific. The first launch in "Operation Fishbowl" was a successful research and development launch with no warhead. In the end, "Operation Fishbowl" produced four successful high-altitude detonations: "Starfish Prime," "Checkmate," "Bluegill Triple Prime," and "Kingfish." In addition, it produced one atmospheric nuclear explosion, "Tightrope."
On July 9, 1962, "Starfish Prime" had a 1.4-megaton explosion, using a W49 warhead at an altitude of about 400 kilometers (250 miles). It created a very brief fireball visible over a wide area, plus bright artificial auroras visible in Hawaii for several minutes. "Starfish Prime" also produced an electromagnetic pulse that disrupted some electric power and communication systems in Hawaii. It pumped enough radiation into the Van Allen belts to destroy or damage seven satellites in orbit.
The final Fishbowl launch that used a Thor missile carried the "Kingfish" 400-kiloton warhead up to its 98-kilometer (61 mi) detonation altitude. Although it was officially one of the Operation Fishbowl tests, it is sometimes not listed among high-altitude nuclear tests because of its lower detonation altitude. "Tightrope" was the final test of Operation Fishbowl and detonated on November 3, 1962. It launched on a nuclear-armed Nike-Hercules missile and was detonated at a lower altitude than the other tests:
"At Johnston Island, there was an intense white flash. Even with high-density goggles, the burst was too bright to view, even for a few seconds. A distinct thermal pulse was felt on bare skin. A yellow-orange disc was formed, and transformed itself into a purple doughnut. A glowing purple cloud was faintly visible for a few minutes." The nuclear yield was reported in most official documents as "less than 20 kilotons." One report by the U.S. government reported the yield of the "Tightrope" test as 10 kilotons. Seven sounding rockets were launched from Johnston Island in support of the Tightrope test, and this was the final American nuclear atmospheric test.