The World War II Gallery in the National Museum of the United States Air Force in Dayton, Ohio includes a display Bockscar: The Aircraft that Ended WWII.
According to the Museum
By August 1945, U.S. Navy submarines and aerial mining by the Army Air Forces severely restricted Japanese shipping. The AAF controlled the skies over Japan and the AAF's B-29 bombing attacks crippled its war industry. A plan for the invasion of Japan had been drawn up; Operation Olympic was scheduled for November 1945. Estimates of Allied casualties ranged from 250,000 to a million with much greater losses to the Japanese. To repel invaders, Japan had a veteran army of some two million ready, an army that had already shown its ferocity and fanaticism in combat. Some 8,000 military aircraft were available that could be used for devastating Kamikaze (suicide) attacks on U.S. ships. The draft had been extended to include men from age 15 to 60 and women from 17 to 45, adding millions of civilians ready to defend their homeland to the death, with sharpened sticks if necessary.
Experience throughout the Pacific war had shown that Japanese combat casualties had run from five to 20 times those suffered by the Allies, particularly in the battles of the Philippines and Okinawa. Whatever the predicted Allied losses, the potential Japanese military and civilian casualties would have been staggering. Whether Japan would have surrendered prior to invasion without the use of the atomic bombs is a question that can never be answered. Using the history and projections available to him, President Harry Truman made the grave decision to use the atomic bomb in an effort to end the war quickly, thus avoiding a costly invasion.
About the B-29 Superfortress:
The B-29 on display, Bockscar, dropped the Fat Man atomic bomb on Nagasaki on Aug. 9, 1945, three days after the atomic attack against Hiroshima. Bockscar was one of 15 specially modified "Silverplate" B-29s assigned to the 509th Composite Group. Most B-29s carried eight .50-cal. machine guns in remote controlled turrets, two .50-cal. machine guns and one 20mm cannon in a tail turret, and up to 20,000 pounds of bombs. Silverplate B-29s, however, retained only the tail turret and had their armor removed to save weight so that the heavy atomic bombs of the time could be carried over a longer distance.
Designed in 1940 as an eventual replacement for the B-17 and B-24, the first B-29 made its maiden flight on Sept. 21, 1942. In December 1943 U.S. Army Air Forces leadership committed the Superfortress to Asia, where its great range made it particularly suited for the long over-water flights against the Japanese homeland from bases in China. During the last two months of 1944, B-29s began operating against Japan from the islands of Saipan, Guam and Tinian. With the advent of the conflict in Korea in June 1950, the B-29 returned to combat. Although vulnerable to MiG-15 jet fighter attacks, the Superfortress remained effective against several types of targets throughout the Korean War.
This aircraft has a top speed of 357 mph, a cruising speed of 220 mph, a range of 3,700 miles, and a ceiling of 33,600 feet.
Fat Man
According to the Museum:
A "Fat Man" bomb was dropped over Nagasaki, Japan, on Aug. 9, 1945, near the end of World War II. Released by the B-29 Bockscar, the 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. Because of Nagasaki's hilly terrain, however, the damage was somewhat less extensive than of the relatively flat Hiroshima.
"Fat Man" was an implosion-type weapon using plutonium. A subcritical sphere of plutonium was placed in the center of a hollow sphere of high explosive (HE). Numerous detonators located on the surface of the HE were fired simultaneously to produce a powerful inward pressure on the capsule, squeezing it and increasing its density. This resulted in a supercritical condition and a nuclear explosion.
Little Boy
According to the Museum:
The Mk I bomb, nicknamed "Little Boy," was the first nuclear weapon used in warfare. It was delivered by the B-29 Enola Gay (on display at the Smithsonian National Air & Space Museum), it detonated at an altitude of 1,800 feet over Hiroshima, Japan, on Aug. 6, 1945. The result of the Manhattan Project, begun in June 1942, "Little Boy" was a gun-type weapon, which detonated by firing one mass of uranium down a cylinder into another mass to create a self-sustaining nuclear reaction. Weighing about 9,000 pounds, it produced an explosive force equal to 20,000 tons of TNT.
When constructed in 1945, the "Little Boy" on display was an operational weapon, but it has been completely demilitarized for display purposes. In 2004 the Department of Energy repaired and repainted the artifact at its Sandia National Laboratories in Albuquerque, N.M.
More World War II Museum Exhibits
Air Force Museum: The Memphis Belle (photo diary)
Air Force Museum: World War II Japanese planes (photo diary)
Air Force Museum: World War II German Planes (photo diary)
Museum of Flight: World War II American fighters (photo diary)
Historic Flight: Grumpy (photo diary)
Historic Flight: Grasshopper, Texan, Spitfire (photo diary)
Planes of Fame: P-38 Lightning (Photo Diary)
Yanks Air Museum: World War II Bombers (Photo Diary)