Underwater Atomic Test, Mark 90 Betty A-Bomb: "Operatiovn Wigwam" 1955 USAF Lookout Mountain Laboratory

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WIGWAM was the first atomic test in the deep ocean.

Originally a public domain film, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.

The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

https://en.wikipedia.org/wiki/Operation_Wigwam

Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

Operation Wigwam involved a single test of the Mark 90 Betty nuclear bomb. It was conducted between Operation Teapot and Project 56 on May 14, 1955, about 500 miles (800 km) southwest of San Diego, California. 6,800 personnel aboard 30 ships were involved in Wigwam. The purpose of Wigwam was to determine the vulnerability of submarines to deeply detonated nuclear weapons, and to evaluate the feasibility of using such weapons in a combat situation. The task force commander, Admiral John Sylvester, was embarked on the task force flagship USS Mount McKinley. WIGWAM was the first atomic test in the deep ocean, and it remains the only test that has been conducted in water deeper than 1000 ft...

The test device was suspended to a depth of 2,000 feet (610 m) by cable attached to a barge. A 6-mile (9.7 km) tow line connected the 205 ft. USS Tawasa (a Cherokee-class fleet tug) and the shot barge itself. Suspended from the tow lines of other tugs were three miniature unmanned submarines named "Squaws", each packed with cameras and telemetry instruments.

The time of detonation was 1300 hrs local Pacific Time (noon Pacific Standard Time). The test was carried out without incident, and government said radiation effects were negligible. The device yielded 30 kilotons. Three personnel received doses of over 0.5 rem (5 mSv). Other sailors on USS Cree (another Cherokee-class fleet tug) were tasked with measuring radiation and said that the ocean water boiled and churned, and radiation meters went off the charts when they held them over the side. The sailors wore minimal protection of their standard cotton clothes only. One sailor on the Cree had three cornea transplants without any official recognition by the U.S. government. The feeling on the feet of the sailors when it went off was like a sledge hammer hitting the deck of the ship.

The equipment intended for direct measurement of the explosion-generated underwater bubble was not operational at the time of the shot, but based on other measurements, the bubble's maximum radius was calculated as 376 feet (115 m), and its pulsation period approximately 2.83 seconds. (See Scientific Director's Report)

See also the United States' nuclear testing series table.

Underwater sound

The underwater sound from the Wigwam explosion was recorded on bottom‐mounted hydrophones at Point Sur and Point Arena off California, and at Kaneohe Bay off Oahu, Hawaii. The sound emanating from the explosive test began as an intense water shockwave. As the sound travelled away from the test point, it reflected from topographic features, such as islands and seamounts, located throughout both the North and South Pacific Basins. The reflected sound was then recorded as hours-long coda at Kaneohe and Point Sur. Some of the acoustic energy travelled round trip distances of over 20,000 km. The sound signals provided one of the early measurements of underwater sound attenuation at low frequencies.