re: #369 The Very Reverend Battleaxe of Knowledge

Not to be forgotten: The first bomb was a one off device, absolutely. That was a year and a half’s worth of material. They could have produced enough for a second one in maybe six months.

The situation with production of nuclear material was more complex than that.

The uranium bomb, Little Boy, dropped on Hiroshima was made from enriched uranium produced by several experimental techniques such as the calutron, gas diffusion and others all being developed during the Manhattan Project. This caused the designers some problems estimating the bomb’s performance as different parts of the core had differing enrichment levels. By the autumn of 1945 the gaseous diffusion line at Oak Ridge Tennessee was up and running although not at 100% levels and it could produce several kilogrammes of bomb-grade material each month. That line was the largest single building under one roof in the world at the time.

As for plutonium weapons like Fat Man dropped on Nagasaki (and the “Gadget” fired at Trinity) again it took time to get the production reactors built and operational but there was a complete weapons pit ready to go after Fat Man was dropped. It was actually being shipped out to Tinian Field via San Diego naval base when the war ended.

The US had three unused but ready-to-go nuclear weapons by the end of 1945, one Little Boy and two Fat Mans according to some references I’ve seen. By mid-1946 that had increased to about 20 or so. The Little Boy design was quickly retired since implosion was more efficient and safer to deploy and it worked with enriched uranium as well as Pu-239.

The really scary weapons production figure around that time wasn’t nuclear, it was aircraft. Boeing built three hundred B-29 bombers in the month of September 1945. That’s AFTER the war ended, it took time for them to stop building more aircraft of the sort that had firebombed much of Tokyo into smouldering rubble in March that year, killing as many as 200,000 people in the process. The European war aircrews flying B-17s were being retrained to do to the rest of Japan what had been done to Tokyo, Osaka, Yokohama and other cities by “conventional” bombing.