On Mon, 5 Feb 1996, Robert A. Rosenberg wrote:
I agree - Not only were there two different separation methods but the two bombs dropped on Japan were of different designs (I think that the Hiroshima bomb was the same design as the land test version and the Nagasaki one was the untested design [so that if used, there would have been a tested design for the first drop]).
Actually, it was the other way round. The bomb dropped on Hiroshima was an enriched uranium gun type bomb; the devices exploded at Trinity and Nagasaki were imploded plutonium devices. The Little-Boy design was not tested before being dropped as 1) the design was so (theoretically) simple that if it didn't work, nothing would, and 2) there wasn't enough enriched uranium to make two of them. Simon p.s. Everybody interested in this subject should read "The making of the Atom Bomb" by Richard Rhodes; it's an amazing book, well worth its Pulitzer. The section dealing with Hiroshima in the seconds and days after the explosion is incredibly painful to read.