It looks like Heisenberg wasn't wrong about the chemistry, only about the economics and willingness of Americans to throw massive amounts of resources at a project:
> HEISENBERG: I don’t believe a word of the whole thing. They must have spent the whole of their ₤500,000,000 in separating isotopes; and then it’s possible.
In reality, the Manhattan project cost about $2B, roughly ₤500,000,000 at the exchange rate of the time. And 85% of it went into building the huge isotope-separation plants in Oak Ridge and Hanford. Heisenberg's estimate was just about on the mark; he just didn't understand that America was willing to spend ₤400M building huge factories to do the necessary uranium separation.
> WIRTZ: We only had one man working on it and they may have had ten thousand.
In reality, America put 600,000 people to work on it. The Germans were incredulous because they could never get political buy-in for the massive scale mobilization needed to build the bomb. America was willing to spend more and employ more people.
Germany just wasn't the kind of industrial powerhouse that the US and USSR were. Their whole blitzkrieg strategy was based on the knowledge that they could not win a war of attrition.
> HEISENBERG: I don’t believe a word of the whole thing. They must have spent the whole of their ₤500,000,000 in separating isotopes; and then it’s possible.
In reality, the Manhattan project cost about $2B, roughly ₤500,000,000 at the exchange rate of the time. And 85% of it went into building the huge isotope-separation plants in Oak Ridge and Hanford. Heisenberg's estimate was just about on the mark; he just didn't understand that America was willing to spend ₤400M building huge factories to do the necessary uranium separation.
> WIRTZ: We only had one man working on it and they may have had ten thousand.
In reality, America put 600,000 people to work on it. The Germans were incredulous because they could never get political buy-in for the massive scale mobilization needed to build the bomb. America was willing to spend more and employ more people.