Source: http://www.childrenofthemanhattanproject.org/HISTORY/little_boy.htm
Weight: 9,700 lbs
Length: 10 ft.; Diameter: 28 in.
Fuel: Highly enriched uranium; "Oralloy"
Uranium Fuel: approx. 140 lbs; target - 85 lbs and projectile - 55 lbs
Target case, barrel, uranium projectile, and other main parts ferried to Tinian Island via USS Indianapolis
Uranium target component ferried to Tinian via C-54 aircraft of the 509th Composite Group
Efficiency of weapon: poor Approx. 1.38% of the uranium fuel actually fissioned
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Info on Fat Man
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 gm of plutonium (1/3 weight of penny) converted to energy
Explosive force: 21,000 tons of TNT equivalent