was her first atomic bomb close to completion at the end of the war?
Minor hijack, but if you ever get a chance to see Michael Frayn’s play Copenhagen, it’s well worth it. The play re-enacts the meeting between Bohr and Heisenberg in Copenhagen and covers many of the points raised in Demostylus’s quote. My paper copy of the play also contains numerous references to what is a very highly contested subject.
As I recall, the consesus is that Germany wasn’t close to building a bomb, but the reasons why are still subject to debate and the release of additional classified material. In particular, the Farm Hall Tapes, hold some answers as to “How much bomb knowledge did the Germans have?” Depending on how you read the tape transcripts, Heisenberg knew quite a bit about making a bomb, but his team didn’t.
The fundamental issue seems to be that Heisenberg either purposely or mistakenly calculated the amount of material necessary, and uses this to convince the German government that the project was impossible. The debate is about whether Heisenberg got the math wrong by accident or on purpose.
On any reading of Heisenberg’s understanding and motive, they were indeed a very long way short. The furthest they got was beginning to assemble a prototype reactor at Haigerloch, moderated with heavy water. Heisenberg seems to have believed this would work, but the more informed concensus is that it was still far from a functioning design. So they weren’t particularly close to a working reactor (something the US and the UK had acheived 2 1/2 years earlier), never mind a bomb.
However, these things are murky. Did Heisenberg even understand what a bomb would involve ? There are several arguments that can be used to suggest that he did. Thomas Powers’ case rests fairly heavily on the handful of contacts between physicists on both sides at the time, most famously the meeting between Bohr and Heisenberg that’s the subject of Copenhagen. One complication here is that a key set of documents - Bohr’s postwar drafts of letters to Heisenberg trying to explain his version of the meeting - have only relatively recently been released by the Niels Bohr Institute. No historian has yet produced an account incorporating this new evidence.
I personally find the main other evidence that Heisenberg was even thinking in terms of bombs extremely weak. His seminar at Farm Hall is a brilliant bit of physics, but it’s after the fact. He knows that a bomb is possible and so came up with an explanation of how it was done. The main other argument derives from the “grapefruit” quote in Speer’s Inside the Third Reich. I don’t have a copy to hand, but basically Speer was to claim that Heisenberg said he could destroy a city with an explosive the size of a grapefruit. That seems a plausible description of an atom bomb. Except (though it has to be said that the literature on Nazi nuclear research hasn’t picked up on this) that it was a common piece of popularisation in the 1930s to dramatise nuclear energy in this sort of way. A typical American quote of the period is that you could destroy a city with the energy in a baseball. But that’s just illustrating E = mc[sup]2[/sup], not proposing it can actually be done. I suspect Heisenberg used such a illustration to Speer and the latter misremembered it after Hiroshima and Nagasaki.
The contemporary evidence is consistent with Heisenberg perhaps realising that a bomb was possible, but only for a huge critical mass. Much larger than a grapefruit and so not acheiveable during wartime. What he did think was possible was a reactor. And given the importance of U-boats to German strategic thinking, this was possibly a significant project in its own right.
Then there’s the possibility that they might have been thinking of dropping a reactor as a bomb. Current ideas about dirty bombing make this seem incredibly insane as an efficient use of resources, but one never knows.
Powers is certainly worth reading, though I fail to find his thesis convincing. (The oddity is that it’s a rehash of Robert Jungk and yet Jungk had previously retracted the hypothesis.) The better portrait of the climate Heisenberg was operating in and the strategies he adopted is Uncertainty (Freeman ,1991), the excellent biography by David Cassidy. Mark Walker’s various contributions are also good.
While Copenhagen works very well as a piece of theatre, to judge by the original West End production, I personally thought it was slightly dodgy history. The odd thing is that I agree that Frayn’s Postscript to the printed edition (Mentuen, 1998) is a rather nice run round some of the issues involved.
Germany could never have built a bomb, because their calculations of the role of the moderationg materila (heavy water) were all wrong. Also, the Germans were never able to produce enriched uranium-their reduction process was faulty.
Conclusion: Heisenburg screwed up-whether on purpose or not will be never known!