Operation Sailor Hat

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Operation Sailor Hat
Sailor Hat Shot.jpg
500 tons of TNT (17 × 34 feet) awaiting detonation at Operation Sailor Hat. The USS Atlanta is visible in the background.
Country United StatesUnited States
Test site Kahoʻolawe, Hawaii
Date February 6-June 19, 1965
Number of tests 3
Test type Non-Nuclear
Device type TNT Charge Stack
Yield 0.5 kilotons of TNT (2.1 TJ)

Operation Sailor Hat was a series of explosives effects tests, conducted by the United States Navy Bureau of Ships under the sponsorship of the Defense Atomic Support Agency. The tests consisted of two underwater and three surface explosions at San Clemente Island, California in 1964 and three surface explosions at Kahoʻolawe, Hawaii in 1965[1]. They were non-nuclear tests employing large quantities of conventional explosives (i.e. TNT) to determine the effects of a nuclear weapon blast on naval vessels. Each "Sailor Hat" test at Kahoʻolawe consisted of a dome-stacked 500-ton charge of TNT high explosive detonated on the shore close to the ships under test. The first test, called Bravo, occurred on 6 February 1965, with the second test, called Charlie, on 16 April and the last, code-named Delta, on 19 June[2].

The main ship used for testing was the former Cleveland-class Light cruiser USS Atlanta. Decommissioned in 1949 and placed in the Pacific Reserve Fleet, it was subsequently earmarked for disposal in 1962. However, after undergoing extensive modifications at San Francisco Naval Shipyard she was converted to a target ship (reinstated as IX-304) to study the effects of high energy air explosions. The hull was cut down to the main deck level and various superstructures were installed to determine their blast resistance[3]. In addition to Atlanta, the guided-missile destroyer leaders USS England and USS Dale, the guided-missile destroyers USS Cochrane, USS Benjamin Stoddert, and USS Towers, and the Royal Canadian Navy's escort destroyer HMCS Fraser all participated in the trial. These were a mixture of the obsolete, Atlanta being built during WWII, and the recently constructed. While Atlanta was a close in target ship, the others were stationed more distantly so that they could be repaired more readily. All ships were manned during the tests. In addition, seismological data, underwater acoustics, radio communications, cratering, air blast effects, cloud growth, fireball generation, and electromagnetic data were gathered.


The test shots resembled a small nuclear explosion, creating a shock wave on the water and an expanding shock condensation cloud. On USS Atlanta, cameras recorded the blast effects inside the ship and have shown that the force of the blast was enough to buckle steel walls and tear off heavy radar equipment and send it flying.[4] Although severely damaged, the ship stayed afloat. In addition, two observation blimps were destroyed high above ground by the shock wave.

USS England, which was farthest from the blast center, experienced the least damage, the most serious of which was only a dent where a boulder had hit the ship. The shock wave caused the ship to move side to side by 4 feet[5].

USS Cochrane lost power for 5 minutes after being hit by the blast overpressure. She was able to restore power and return to Pearl Harbor Naval Shipyard for a hull and systems inspection and to asses the effects of the blast. The yard noted that the ship performed well in terms of resistance to the blast. After some minor repairs (Both the 3-Dimensional AN/SPS-39 & 2-Dimensional AN/SPS-40 Air Search Radar Antennas had to be replaced) and routine maintenance Cochrane was cleared for her first deployment[6].

The crater left by the blast is called the "Sailor's Hat" crater and holds an anchialine pool containing Halocaridina rubra shrimp, which have adapted to the conditions in the crater.[7]


  1. ^ "Protect Kaho'olawe 'Ohana". Retrieved 17 April 2017. 
  2. ^ "Naval Historical Center". Retrieved 17 April 2017. 
  3. ^ "Naval History and Heritage Command". Retrieved 17 April 2017. 
  4. ^ Operation Sailorhat 1965. Retrieved 2014-12-16. 
  5. ^ "USS England official website". Retrieved 17 April 2017. 
  6. ^ "USS Cochrane History". USS Cochrane. Retrieved 17 April 2017. 
  7. ^ Brock, R.; J. Bailey-Brock (1997). "An Unique Anchialine Pool in the Hawaiian Islands". International Review of Hydrobiology. 83 (1): 65–75. Retrieved 2010-04-01. 

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Coordinates: 20°30′15″N 156°40′44″W / 20.50417°N 156.67889°W / 20.50417; -156.67889