Between the years of 1946 and 1958, a nuclear testing program was put in place by the United States in Bikini Atoll (part of the Marshall Islands). They used seven test sites in this area; a mix of underwater, on the reef and aerial tests.
Operation Crossroads was the name given to the very first series of tests that were conducted, the second detonation of this set resulted in immediate, radioactive fallout. The second series was codenamed Operation Castle and started by testing a thermonuclear hydrogen bomb. The expected yield of this bomb was to be 4-8 megatons; however, it totaled 15 megatons – which is 1,000 times the yield of each of the atomic bombs used in Hiroshima and Nagasaki.
The U.S. Navy arranged for 95 ships to be used during this testing, they included cruisers, carriers, battleships, submarines, destroyers and many more. The reason for the variety and quantity of ships was to test how well each could withstand the damage of nuclear bombs. Military equipment was used in the testing also; tanks and armor were positioned on these ships to see how they withstood the affects of the bombs also.
Whilst testing occurred in the area, the local inhabitants were asked by the Navy to temporarily relocate, however, none returned as the Atoll could no longer support farming or fishing, due to contamination. The inhabitants were later compensated for this occurrence.
A total of 23 nuclear devices were detonated over this period of time, if you combine the fission fields of all of these they total 42.2 Mt.
Many of the ships used in this testing now lie on the ocean floor; this video shows them still lying there, a little piece of hidden history.
Preparation
Seabees with the 53rd NCB constructing a tower to hold automatic camera as part of Operation Crossroads. The towers were built on an island near Bikini Atoll to document the Atomic Bomb explosion. [Via]
U.S. Navy Grumman F6F-5K Hellcat drones during the “Operation Crossroads” atomic tests at the Bikini Atoll in July 1946. The Hellcats were flown through the cloud formation to test radioactivity. The different coloured tails indicated different radio guidance frequencies. [Via]
Battleship USS Nevada (BB-36) painted in orange as target ship for the Operation Crossroads Able Nuclear weapons test [Via]
Prospective Operation Crossroads target ships and support ships at Pearl Harbor on February 27, 1946. Ships from front to rear: USS Crittenden, Catron, Bracken, Burleson, Gilliam, Fallon, unknown ship, Fillmore, Kochab, Luna, and an unidentified tanker and liberty ship. On the right are LSM-203 and LSM-465. Farther in the background are a floating drydock and a merchant ship hulk. [Via]
Test animals were deliberately confined to the ships of Operation Crossroads. Goat #53, penned like this on the Nevada deck, died of radiation exposure two days after Able. [Via]
USS Appling (APA-58) lies outboard (top) of sister ships Barrow (APA-61), Brule (APA-66) and Gasconade (APA-85), at the Pearl Harbor Naval Shipyard, 27 February 1946, as they are readied for Operation Crossroads. [Via]
U.S. military observers watch the explosion during Operation Crossroads Baker, a nuclear test conducted on Bikini Atoll on July 25, 1946. This was the fifth nuclear explosion ever, after two other tests and the two bombs dropped on Hiroshima and Nagasaki. (U.S. Department of Defense) [Via]
Crossroads Able, a 23-kiloton air-deployed nuclear weapon detonated on July 1, 1946. This bomb used the infamous Demon core that took the lives of two scientists in two separate criticality accidents. [Via]
Aerial view of the Able mushroom cloud rising from the lagoon with the Bikini Island visible in the background. The cloud carried the radioactive contaminants into the stratosphere. [Via]
Crossroads Baker 4 milliseconds after the explosion, the shock wave reaching the surface throws up a “spray dome”, rising at an initial speed of 2500 ft/sec (mach 2.5), in advance of the rapidly expanding bubble of hot gases. This picture shows the spray dome development a few milliseconds later. The light from the sub-surface fireball is clearly visible. [Via]
In this frame of this sequence, the front of the faster moving the hydrostatic shock is visible as a fainter ring surrounding the white slick of the atmospheric shock. [Via]
Crossroads Baker, showing the white surface “crack” under the ships, and the top of the hollow spray column protruding through the hemispherical Wilson cloud. Bikini Island beach in the background. [Via]
At this point the mushroom cloud head is 6000 feet across (2000 meters). It rose to 10,000 feet (~3000 meters before dispersing). The base surge is prominent. Expanding outward initially at over 60 mph, it rapidly rose to a height of 900 feet (300 meters). The expanding surge formed a doughnut shaped ring 3.5 miles (5 km) across and 1800 feet high 4 minutes after the explosion. [Via]
The Wilson cloud lifts, revealing a vertical black object, larger than ships in the foreground, which most observers believed was the upended battleship Arkansas. [Via]
The Wilson cloud has evaporated revealing the cauliflower atop the spray column. Two million tons of water spray fall back into the lagoon. The radioactive base surge is moving toward the ships. [Via]
The Baker shot of Operation Crossroads, Bikini Atoll, July 25, 1946. As the spray column collapses a 900-foot-tall “base surge” of radioactive mist envelops the target ships. Ship in the foreground (left) is the Japanese battleship Nagato. [Via]
Aftermath
The U.S. light aircraft carrier USS Independence (CVL-22) afire aft, soon after the “Able Day” atomic bomb air burst test at Bikini on 1 July 1946 (Operation Crossroads). The bomb had exploded off the ship’s port quarter, causing massive blast damage in that area, and progressively less further forward. The carrier did not sink during the tests and was finally sunk as a target off San Francisco, California (USA), on 27 January 1951. [Via]
Second Atom Bomb sinks U.S. Aircraft Carrier USS Saratoga —Surrounded by the target ships in the lagoon of Bikini, the USS Saratoga slowly settles to a watery grave. The ‘Sara’ was too “hot” to be boarded by salvage man in order to prevent her from sinking. Joint Army Navy Task force One Photo Released August 1, 1946 [Via]
The Baker shot of Operation Crossroads, Bikini Atoll, July 25, 1946. A navy fireboat washes down the battleship New York with seawater, to reduce radioactive contamination after the base surge passed over it. They are using radioactive lagoon water to wash it down, making this is highly ineffective. [Via]
Sailors scrubbing down the German cruiser Prinz Eugen with brushes, water, soap, and lye. Five months later, the ship was still too radioactive to permit repairs to a leak, and she sank. [Via]
The aircraft carrier USS Saratoga sinks, due to damage sustained from “Test Baker” – a 21 kiloton atomic bomb blast, part of the Operation Crossroads atomic tests on naval ships. [Via]
