Keep in mind that an explosive nuclear chain reaction occurs when a sufficient quantity of nuclear fuel, such as uranium or plutonium, is brought together to form a critical mass.  This is the minimum amount of fissionable material needed to start a chain reaction.  The chain reaction starts when neutrons strike the heavy uranium or plutonium nucleus which splits releasing a tremendous amount of energy along with two or more neutrons which, in turn split more nuclei, and so on.  In the implosion-type device, a core of sub-critical plutonium is surrounded by several thousand pounds of high-explosive designed in such a way that the explosive force of the HE is directed inwards thereby crushing the plutonium core into a super-critical state.

Dropped on the Japanese city of Nagasaki on August 9, 1945, it was the second nuclear weapon used in a war.  Following are some approximate statistics for Fat Man.  If you require more extensive information on this weapon, please contact us via feedback:

• Weight: 10,800 lbs
• Length: 10 ft 8 in.; Diameter: 60 in.
• Fuel:  Highly enriched plutonium 239
• Plutonium Fuel: approx. 13.6 lbs; approx. size of a softball
• Plutonium core surrounded by 5,300 lbs of high explosives; plutonium core reduced to size of tennis ball
• Bomb Initiator:  Beryllium - Polonium
• All components of Fat Man ferried to Tinian Island aboard B-29's of the 509th CG
• Efficiency of weapon: 10 times that of Little Boy
• Approx 1.176 Kilograms of plutonium converted to energy
• Explosive force: 21,000 tons of TNT equivalent
• Use:  Dropped on Japanese city of Nagasaki; August 9, 1945
• Nuclear Weaponeer: Cdr. Frederick Ashworth
• Delivery:  B-29 Bockscar piloted by Maj. Charles Sweeney

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