Comments by "Keit Hammleter" (@keithammleter3824) on "Oppenheimer Atomic bomb How it Works | First Nuclear Bomb" video.

It wasn't just a matter of being confident it would work. They didn't have enough enriched uranium to do a test, and took a calculated risk that it would work, as the need to give the Japanese a good war-ending whack was super urgent. In fact, post war analysis has shown that it didn't work all that well - yield (~15,000 tonnes TNT equivalent) was quite a bit below the design expectation (22,000 tonnes TNT equivalent)
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@kvom01 ; That would be correct. To have almost all the reaction occurring after teh masses have joined, the speed of coming together would have to be much greater than the neutron speed. Neutron speed is over 10,000,000 metres/sec, about 9,000 times the speed of sound in air. No gun that good could fit in an aircraft carrier, let alone a plane.
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@recoilrob324 ; That is a considerable exaggeration, however the amount of uranium that was converted into nuclear explosive energy in Little Boy was very small - about 0.7 grammes, whereas an average grain of rice is about 0.03 grammes. 0.7 grammes is about 0.001 percent of the total amount of uranium loaded in Little Boy. Given that fact, it is not at all surprising they could not calculate the yield very well (they were about 30% out) and gives lie to those armchair experts who claimed it was dead certain to work because it was simple . Simple is was, but that it did work was amazing.
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@recoilrob324 ; In such contexts, people usually mean weight/mass, as the quantity is then clear, and independent of sample shape. So, what do you mean by "size"? Length? Volume? You are right, though - it is a minor quibble - the energy contained in a tiny amount of matter is very large.
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@jameshoran8 ; Firstly, Little Boy was completed and ready first. Secondly, it didn't matter whether the first one dropped was a dud, or it worked and the second one was a dud. Both scenarios would have been disaster. The essence of why the bombs were used is this: first, the Japanese were warned, ""Give up now, or you'll get it with a new terrible bomb." then the first one was dropped. As turned out to be the case, they anticipated that one bomb might not enough to shake Japanese resolve. So they were warned again, "give up or you'll get it again."" That worked - the second bomb caused the Emperor to stop the fight. Thus if the first bomb dropped was a dud, the Japanese would have fought on. If the second one was a dud, the Japanese were still likely to fight on, perhaps more so. If you make a threat and don't carry it out, your influence is gone. Thirdly, Fatman was technically a much better bomb, and a test had shown it would work, but the US needed to get good data of its exact effects under combat conditions, and the USAAF was not quite ready to do that when the first one was dropped.
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