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    Operation Crossroads - 1946

    / Main Archive / USA /



    Page: 2/3

    Shot Able



    Able - 1st July 1946
    The first shot of Operation Crossroads, Able, was an air drop of a Mk-3 plutonium implosion bomb over the target array of ghost ships. This was the world's fourth nuclear explosion, second nuclear test, and first weapons effects test.

    By mid-June the Task Force was in place. The Durleson, with its cargo of experimental animals, was one of the last arrivals (14th June). Several small scale-rehearsals were done in preparation from Able Day.

    On Queen Day, the eighth day before the Able test, a complete dress rehearsal was staged. The bombing plane made its runs, dropping a flash-powder bomb which went off near the target ship Nevada at 0914. In the air, manned and unmanned planes followed the courses prescribed in the Air Plan prepared 3 months before. Vital to the success of Queen Day was the evacuation on the previous day of the 42,000 men of the Task Force from the target vessels, the Lagoon, and encircling islands. Every man had to be ccounted for, including the technicians who had made hurried, last minute adjustments on the scientific instruments on the target array and islands.

    Favorable weather conditions were necessary before shot day. On the day preceding Able Day, and on Able Day itself, three special weather reconnaissance missions were made. Daily weather conferences were held between forecasters at Kwajalein and Captain A.A. Cumberledge, USN, and Col. B. G. Holtzman at Bikini.

    At the morning weather conference on 30 June 1946, favorable weather was forecast for the following day, so Admiral Blandy set 0830, 1 July 1946 as shot time. At the evening weather conference, conditions still appeared favorable. However, fairly heavy cloud cover was reported early on the morning of 1 July, and shot time was changed to 0900.

    Evacuation of Task Force support ships began soon after CJTF 1 set the hour for Able. All destroyers except USS Moale got underway and were clear of the lagoon by early afternoon on 30 June. Most of the support ships of TG 1.2 were out of the lagoon shortly thereafter. Small craft had evacuated Task Force personnel from Enidrik and Eneman islands and transferred them to Fall River, which then left the lagoon along with the smaller ships of TG 1.2. Ten ships remained in the lagoon after 1800 hours.

    Preparations ashore had included removal the roofs of buildings to prevent blast damage and removal of the pontoon-supported docks and causeways that had been installed on the islands. Machinery such as refrigerators, generators, and water-distilling units had been covered by tarpaulins.

    F6F-5K drone aircraft
    USS Chilton evacuated 691 nonessential personnel and natives from Enewetak before the test. Provision had been made to evacuate essential U.S. personnel on Enewetak if necessary, and five C-54 air transports were at Enewetak for this purpose. The Marshallese on Rongerik to the east had been taken aboard USS LST-989 in case evacuation was necessary there.

    Two additional C-54s were sent from their Kwajalein base on 30 June, one to Enewetak and one to Roi Island. These were scheduled to receive the radioactive cloud samples to be collected by the B-17 drone samplers based at Enewetak and the F6F drone samplers returning it following the shot.

    Non-target small craft were moored (unmanned) in the lagoon off Eneu Island about 5 nmi south of the test area. Among these were several drone boats equipped to be remotely controlled. After each detonation the drones were guided by aircraft and USS Beqor to areas in the target array to collect water samples and take radiation readings. After the water samples were collected, the drones were guided back to Begor where they were hosed down to remove radioactive contamination and retrieve samples.

    After each test the drones were followed by six patrol motor gunboats (EMS) and twenty landing craft (LCPLs) with radiation monitors aboard. Radiation intensity measurements were sent by radio to the Radsafe Control Center. From this information and that gathered from aircraft equipped with radiation detectors, it was determined when a safe reentry to the lagoon by the main body of the fleet could be.

    - Video showing Gilda being loaded


    The first airborne aircraft were three B-29s that had made weather reconnaissance flights in the shot area and northeast and northwest of Bikini Atoll. At 0540 CJTF 1 ordered the drop aircraft to take off from Kwajalein, which had the bomb loaded about midnight. The four F6F drones and sixteen F6F controllers from USS Shangri-La were airborne shortly after 0700. In all, 79 aircraft were airborne on the morning of Able. By 0800 all aircraft and ships were on station. One F6F drone went out of control and crashed in the sea just as the B-29 began its live run at 0850. The bombing aircraft had made one practice run before the live run.

    The live bombing run was made at 28,000 feet. The bomb was released at 08:59 detonating with a yield of 21 kilotons at 09:00:34.



    "At 20 miles it gave us no sound or flash or shock wave... Then, suddenly, we saw it – a huge column of clouds, dense, white, boiling up through the strato-cumulus, looking much like any other thunderhead but climbing as no storm cloud ever cloud. The evil mushrooming head soon began to blossom out. It climbed rapidly to 30,000 to 40,000 feet, growing a tawny-pink from oxides of nitrogen, and seemed to be reaching out in an expanding umbrella overhead .... For minutes the cloud stood solid and impressive, like some gigantic monument over Bikini. Then finally the shearing of the winds at different altitudes began to tear it up into a weird zigzag pattern."

    - Oberver's account of the Able detonation from a Navy PBM 20 nmi away


    6,000 pairs of dark goggles were distributed to personnel who were directed to look into the blast. All other servicemen were required to turn their backs and shield their eyes against the brilliant flash of the nuclear explosion. Observers included Congressmen, the President's Evaluation Commission, the Joint Chiefs of Staff Evaluation Board, United Nations representatives, and media correspondents.

    The event was described by many of the personnel that observed it from ships 20 nautical miles away as being disappointing. Professor Simon Alexandrov, Russian delegate to the United Nations Atomic Energy Commission, reportedly pointed to the mushroom cloud and said "Not so much." One serviceman was quoted as saying "Well, it looks to me like the atom bomb is just about like the Army Air Force—highly overrated".

    The bomb missed its intended target by 650 meters, detonating west of the planned surface zero. This was probably due to a collapsed tail fin on the bomb. The Navy accused the Air Force of sabotaging the test and visa versa. A government investigation later agreed that a flaw in the bomb's tail stabilizer had caused the miss, and the flight crew was cleared of responsibility.

    - Details of the Able target array



    The five ships sunk by the Able explosion were Sakawa, USS Anderson (DD-411), USS Lamson (DD-367), USS Carlisle (APA-69), and USS Gilliam (APA-57).

    In addition to the five ships that sank, fourteen were judged to have serious damage or worse, most due to the bomb's air-pressure shock wave. All but three were located within 900 m of the detonation. Inside that radius, orientation to the bomb was a factor in shock wave impact. For example, the destroyer Lamson, which sank, was farther away than seven ships that stayed afloat. Lamson was broadside to the blast, taking the full impact on its port side, while the seven closer ships were anchored with their sterns toward the blast, somewhat protecting the most vulnerable part of the hull.

    - Video showing the Able aftermath



    USS Independance
    Serious damage to the aircraft carrier Saratoga, more than a 1.6 km from the blast, was due to fire. For test purposes, all the ships carried sample amounts of fuel, ordnance and airplanes. Most warships carried a seaplane on deck, which could be lowered into the water by crane, but the Saratoga carried several airplanes with highly volatile aviation fuel, both on deck and in the hangars below. The fire was extinguished and the Saratoga was kept afloat for use in the Baker shot.

    The only large ship inside the 900 m radius which sustained moderate, rather than serious damage was the Japanese battleship Nagato, whose stern-on orientation to the bomb gave it some protection. As the ship from which the Pearl Harbor attack had been commanded, Nagato was positioned near the aim point to guarantee its being sunk. Since the Able bomb missed its target, that symbolic sinking would come three weeks later, in the Baker shot.

    Ships beyond 600 m that had sustained sufficently low levels of damage and contamination, were re-boarded on July 1 and used for crew quarters. By 5 July all target vessels (except those sunk) had been rehabilitated to the extent necessary for the upcoming Baker event.

    Fifty-seven guinea pigs, 109 mice, 146 pigs, 176 goats, and 3,030 white rats had been placed on 22 target ships in stations normally occupied by people. 10% of the animals were killed by the air blast, 15% were killed by fireball radiation, and 10% were killed during later study. Altogether, 35% of the animals died as a direct result of blast or radiation exposure.

    Although the target ship the Nevada was not sunk or heavily contaminated (due to the poor targetting), had it been fully manned direct radiation from the fireball would probably have exterminated most the crew rendering her a ghostship.


    Able damage results:
    • 5 ships sunk
    • 6 ships seriously damaged
    • 8 ships seriously impaired efficiency
    • 9 ships moderately damaged
    • 43 ships negligible damage
    • 22 landing craft beached at Bikini Isl.
    • 14 aircraft destroyed
    • 30 aircraft seriously damaged
    • 10 aircraft lightly damaged
    • 19 aircraft no damage


    - Click on a thumbnail for a larger version





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