nuclear weapon used in warfare was dropped on
Nagasaki, Japan, on August 9, 1945 (the first,
had been dropped on Hiroshima just three days
"Fat Boy" was dropped
from a B-29 piloted by Major Charles W. Sweeney.
When the bomb reached 1,850 feet, control plugs
and a radar antenna detonated an explosive charge
that crushed a hollow sphere of plutonium into a
beryllium-polonium core, creating an explosive
force equal to 20 kilotons of TNT. At least
40,000 people were killed in the blast.
How It Worked
"Fat Man" was 7 feet
8 inches long, 5 feet in diameter, and weighed
10,200 pounds. It was an implosion-type weapon
with a plutonium core. A subcritical sphere of
plutonium was placed in the center of a hollow
sphere of high explosive. Numerous detonators
located on the surface of the high explosive were
fired simultaneously to produce a powerful inward
pressure on the core, squeezing it and increasing
its density, resulting in a supercritical
condition and a nuclear explosion.
The implosion method used for
"Fat Man" is not only more efficient
than the gun-type method used for "Little
Boy," it is also far safer. Because a
perfect synchronization of the explosive charges
is required for the core to properly detonate,
the chances of an accidental nuclear detonation
due to a plane crash or fire are practically nil.
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