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Otto Hahn (a german) found out about nuclear fission in 1938, so that should have given the Germans a head start in developing a nuclear bomb. However they did not succeed in doing so during WWII. I've heard a lot of reasons why they couldn't do it:

  • allied bombing
  • shortages of heavy water and other important raw material
  • miscalculations (they thought graphite can't be used as moderator)
  • moral scruples by leading scientists
  • German intelligence didn't know about the Manhattan project

But does anybody know, which of these (or any others) have really been relevant? Why didn't the Germans succeed in building a nuclear bomb in second world war?

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  • $\begingroup$ Wikipedia has a detailed article on Uranverein including comparisons to the Manhattan Project, which had at least 3 major factors going for it that Uranverein did not, and still did not succeed until after the war. There are some conspiratorial theories out there, such as Heisenberg sabotaging it by suggesting heavy water as the moderator instead of graphite, but those are fanciful, see Why the Germans Failed to Accomplish a Nuclear Bomb $\endgroup$ – Conifold Oct 27 '16 at 19:32
  • $\begingroup$ Not good-quality enough to be a genuine answer: I have some recollection of having read that Hitler and his close advisors did not believe, or had not been persuaded, that pursuing nuclear stuff would be cost-effective, in any case, and they did indeed have some sense of their resource limits. Not that their scientists had no idea, obviously, although they did not have the resources to do Manhattan-project-like experiments to assay the feasibility, etc. $\endgroup$ – paul garrett Nov 17 '16 at 23:06
  • $\begingroup$ I thought we had tapes of German scientists in British house arrest after the war expressing their disgust that they miscalculated the amount of uranium needed. An order of magnitude, a kg vs 1000 kg and whereas a few kg was within reach a 1000 was certainly not. Is this story just a rumor? $\endgroup$ – James S. Cook Nov 29 '16 at 4:20
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On my opinion, there are two important reasons:

a) German government did not press the matter. Nobody convinced it that the thing is plausible and important. (In the US there was a lobby who could convince the US president in this. Szilard, V. Bush and Einstein played an important role).

b) I think even if they wanted, they could not do it. They simply had no enough resources for a project of such scale. I mean resources of all kinds, including human, industrial, economic etc. Look how many top scientists were employed in the Manhattan project. And how many of them were immigrants from Germany, Austria, Italy. There were also problems with all other resources, and bombing played some role too. Look at the Oak Ridge uranium enrichment plant. Where could the Germans build anything comparable? And even if built this could not be kept secret, and would be certainly bombed.

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  • $\begingroup$ I agree with (b) - there is no way that Germany (or Japan) could have produced the necessary amounts of enriched uranium or plutonium. At one point, the Y-12 plant (uranium isotope separation) was using something like 10-15% of the total electricity produced in the US (which was substantially more than produced in Germany). Germany never started down that road in the first place - there was no path to a real atomic bomb without isotope separation or plutonium production reactors. $\endgroup$ – Jon Custer Nov 4 '16 at 16:11
  • $\begingroup$ Exactly: the cost. To have feasible nuclear bomb, you need plutonium, which has to be manufactured in a breeder nuclear reactor, which is easy to bomb target (and extremely expensive to build). To develop the nuclear technology, you also need heavy water, and sabotage of it's production (in Norway) was one of the most successful sabotage operations of WWII. $\endgroup$ – Peter M. Dec 27 '17 at 15:09
  • $\begingroup$ @JonCuster - The scale of the of the complexity and cost of Y-12: for electromagnetic isotope separation, they used 12 300 tonnes (1 tonne = 1000 kg = 2204 lb) of silver (copper as strategic material was not available in necessary quantities) converted to wires for the coils. After manufacturing the wires, facility was burned down to extract spilled silver from the ashes. $\endgroup$ – Peter M. Dec 27 '17 at 15:23
  • $\begingroup$ @PeterMasiar - the racetracks were absolutely not burned down. The magnet windings, silver wire on steel frames, were returned to the UD Treasury for processing. One can easily find pictures on line of the frames stacked for shipment. Burning down the building would have made the task monumentally harder (and wasted a good building). $\endgroup$ – Jon Custer Dec 27 '17 at 18:05
  • $\begingroup$ @JonCuster - Floors in the facility which manufactured the wires from silver was burned down, not the calutrons. BTW your claim that Y-12 used 10% of total US electricity was disputed and estimated at 200MW ~ 0.9% (which is still a lot, for a single facility in a country fully manufacturing). $\endgroup$ – Peter M. Dec 27 '17 at 18:21
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By accident I stumbled upon a recent article about the topic in a german science journal:

It is based on a the following publication:

Popp. M.: Misinterpreted Documents and Ignored Physical Facts: The History of "Hitler’s Atomic Bomb" Needs to be Corrected. In: Berichte zur Wissenschaftsgeschichte 39, S. 265 – 282, 2016

It is shown that until the end of the war the German physicists did not know that an atomic bomb can only be made with fast neutrons, except Heisenberg, who, however, discovered it rather late, did not communicate it clearly and did not study any bomb physics.

In the article of the german science journal (spektrum.de) the author mentiones another important reason:

The physicists knew, that if they show the german government that it is possible to build a nuclear bomb they will all be forced to work on it. However if they would not succeed in two years, they would all be doomed to end in on of the infamous concentration camps.

So the german scientists tried to avoid a big project. Instead there were a lot of small projects, which were not striving for success. The scientists just wanted to avoid being sent to the battlefront. The small projects on nuclear physics were more seen as a life insurance.

So the author concludes:

The most important reason [for not developing the bomb] was fear of the Nazi regime. Already Goudsmit had written, that "science unser fascism was not, and in all probability could never be, the equal of science in a democracy".

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    $\begingroup$ Regarding "science unser fascism was not, and in all probability could never be, the equal of science in a democracy": Mutatis mutandis does this imply that science under Stalinist communism, which build an atomic bomb shortly after the US could be the equal of science in a democracy? $\endgroup$ – freecharly Nov 26 '16 at 1:03
  • $\begingroup$ The task the scientists of the Soviet Union had to do for building a nuclear bomb wasn't the same as what the US had done. The scientists of Soviet Union knew that they would succeed eventually, because the US had shown that it is possible at all to build such a bomb. This is a completely different situation. And besides this advantage for the scientists of the Soviet Union they still needed 4 years to replicate what the US had done. So I can't see how the the fact that the Soviet Union managed to build a nuclear bomb invalidates Goudsmit's statement. $\endgroup$ – asmaier Nov 26 '16 at 19:32
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    $\begingroup$ I think knowing that the bomb can be built was not the most essential factor that the Soviets could do it so quickly. Much more important was probably the very detailed technical know-how they received very early in the Manhattan project from a number of independently working spies (like Klaus Fuchs) that where even partly involved in the development. $\endgroup$ – freecharly Nov 26 '16 at 20:49
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Given enough time and resources, the Germans would have produced a bomb.

What held them back was firstly that they were persecuting a large section of their existing scientific and engineering community (many literally going up the chimney) - either for their political views (socialists and communists) or because of their ethnic background (Jews).

The Allied powers on the other hand were mopping up a lot of that German scientific community and were not generally expelling or persecuting anyone (and certainly not systematically killing).

The effect of the Nazi regime on scientific morale was also probably a factor. They had reasonably committed scientists like Von Braun, but not everybody was ideologically reconciled, and would have seen many friends and associates disappeared or forced to leave the country (the Nazi regime was promoted mainly to suppress growing socialist support amongst the populace in Germany).

Whereas the Allies did not seem to have the same ideological problem at the time - the majority were reasonably unified in their opposition to the Nazis, moreso as time went on. That would have been accentuated in scientific circles, surely, by the fact of working alongside refugee German scientists.

A third problem is that of resources. American industry was booming whilst German industry was being smashed.

In places like Britain where industry was also being pummelled, the economy was extensively nationalised at the outbreak of war in 1939 in order to organise and control it efficiently for war, whereas the Germans continued with private sector production until well into the 40s (prompted only because they were falling onto the back foot economically by then).

By time they might have wanted a bomb, they had decimated their scientific community (in numbers and morale), their economy was under siege, and there were too many competing demands (against a speculative nuclear bomb project) for the remaining resources, in a war that by that time was going against them.

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As regards the Soviet's quick progress on the bomb please read Dark Sun which is Richard Rhodes second book on the making of the atomic bomb. Early on he describes the wholesale shipping of plane loads of secrets to the soviets by their well respected U.S patriot spies here.

The reasons given are well considered but unmentioned is Hitler's impatience which I think was mentioned in The Making of the Atomic Bomb. The prospect of a multi year project for just a bomb would not interest him in the least. He turned down more development of the first working jet airplane for similar narrow minded reasons.

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