Lowering "Fat Man" bomb into a bomb pit at the airfield. 5th August 1945. This plutonium爄mplosion-type燽omb that was detonated over the Japanese city of Nagasaki by the United States on August 9; 1945. It was dropped from the Boeing B-29 Superfortress Bockscar; named after its pilot; Captain Frederick C. Bock.燭he 10;000-pound weapon was detonated at an altitude of approximately 1;800 feet over the city. The bomb had an explosive force (yield) of about 20;000 tons of TNT; about the same as the bomb dropped on Hiroshima.燭inian; Mariana Islands in the western燦orth Pacific Ocean.