page_title: Fat Man
section_title: Bomb assembly
hierarchical_section_title: Fat Man / Bombing of Nagasaki / Bomb assembly
caption_attribution_description: العربية: صورة لسحابة عيش الغراب الناتجة عن الأنفجار النووي عند إلقاء قنبلة "الرجل البدين" على مدينة ناگازاكي اليابانية سنة 1945 اثناء الحرب العالمية الثانية. Български: Гъбата от атомният взрив над Нагасаки на 9 август 1945 Deutsch: Atombombenabwurf mit einer Boeing B-29 Superfortress auf Nagasaki am 9. August 1945. Der Atompilz stieg 18&#160;km hoch. English: Mushroom cloud above Nagasaki after atomic bombing on August 9, 1945. Taken from the north west. Русский: Атомная бомбардировка города Нагасаки 9 августа 1945 года. Español: Nube de hongo sobre Nagasaki producida por la bomba atómica. Tomada desde un B-29 a una altura de 18 km Français&#160;: Le champignon atomique sur Nagasaki est monté jusqu'à une altitude de 18 km. Nederlands: Paddestoelwolk boven Nagasaki na de aanval op 9 augustus 1945. Genomen vanuit het noordwesten. Română: Ciuperca atomică de la Nagasaki, Japonia, 9 august 1945. Svenska: Atombomben över Nagasaki resulterar i ett svampformat moln som sträcker sig över 18 km upp i luften. Scope and content: Original caption: A dense column of smoke rises more than 60,000 feet into the air over the Japanese port of Nagasaki, the result of an atomic bomb, the second ever used in warfare, dropped on the industrial center August 8, 1945, from a U.S. B-29 Superfortress. General notes: Atomic Cloud Rises Over Nagasaki (Q55437339)
context_page_description: "Fat Man" was the codename for the nuclear bomb that was detonated over the Japanese city of Nagasaki by the United States on 9 August 1945. It was the second of the only two nuclear weapons ever used in warfare, the first being Little Boy, and its detonation marked the third nuclear explosion in history. It was built by scientists and engineers at Los Alamos Laboratory using plutonium from the Hanford Site, and it was dropped from the Boeing B-29 Superfortress Bockscar piloted by Major Charles Sweeney.
  The name Fat Man refers to the early design of the bomb because it had a wide, round shape; it was also known as the Mark III. Fat Man was an implosion-type nuclear weapon with a solid plutonium core. The first of that type to be detonated was the Gadget in the Trinity nuclear test less than a month earlier on 16 July at the Alamogordo Bombing and Gunnery Range in New Mexico. Two more were detonated during the Operation Crossroads nuclear tests at Bikini Atoll in 1946, and some 120 were produced between 1947 and 1949, when it was superseded by the Mark 4 nuclear bomb. The Fat Man was retired in 1950.
context_section_description: The first plutonium core was transported with its polonium-beryllium modulated neutron initiator in the custody of Project Alberta courier Raemer Schreiber in a magnesium field carrying case designed for the purpose by Philip Morrison. Magnesium was chosen because it does not act as a tamper. It left Kirtland Army Air Field on a C-54 transport aircraft of the 509th Composite Group's 320th Troop Carrier Squadron on 26 July and arrived at North Field on Tinian on 28 July. Three Fat Man high-explosive pre-assemblies (designated F31, F32, and F33) were picked up at Kirtland on 28 July by three B-29s: Luke the Spook and Laggin' Dragon from the 509th Composite Group's 393d Bombardment Squadron, and another from the 216th Army Air Forces Base Unit. The cores were transported to North Field, arriving on 2 August, when F31 was partly disassembled in order to check all its components. F33 was expended near Tinian during a final rehearsal on 8 August. F32 presumably would have been used for a third attack or its rehearsal.
  On 7 August, the day after the bombing of Hiroshima, Rear Admiral William R. Purnell, Commodore William S. Parsons, Tibbets, General Carl Spaatz and Major General Curtis LeMay met on Guam  to discuss what should be done next. Since there was no indication of Japan surrendering, they decided to proceed with their orders and drop another bomb. Parsons said that Project Alberta would have it ready by 11 August, but Tibbets pointed to weather reports indicating poor flying conditions on that day due to a storm and asked if the bomb could be made ready by 9 August. Parsons agreed to try to do so.
  Fat Man F31 was assembled on Tinian by Project Alberta personnel, and the physics package was fully assembled and wired. It was placed inside its ellipsoidal aerodynamic bombshell and wheeled out, where it was signed by nearly 60 people, including Purnell, Brigadier General Thomas F. Farrell, and Parsons. It was then wheeled to the bomb bay of the B-29 Superfortress named Bockscar after the plane's command pilot Captain Frederick C. Bock, who flew The Great Artiste with his crew on the mission. Bockscar was flown by Major Charles W. Sweeney and his crew, with Commander Frederick L. Ashworth from Project Alberta as the weaponeer in charge of the bomb.
caption: Mushroom cloud after Fat Man exploded over Nagasaki on 9 August 1945
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