The Bethe-Feynman efficiency formula, a simple method for calculating the yield of a fission bomb, was first derived in 1943 after development in 1942. Aspects of the formula are speculated to be secret restricted data.
- a = internal energy per gram
- b = growth rate
- c = sphere radius
A numerical coefficient would then be included to create the Bethe–Feynman formula—increasing accuracy more than order of magnitude.
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