Rand Simberg wrote:
On Tue, 21 Feb 2006 00:21:46 +0800, in a place far, far away, "Neil
Gerace" made the phosphor on my monitor glow in
such a way as to indicate that:
snip
Either way I don't think Germany had the materials to make enough bombers to
do any damage to the country which had by then become the main enemy.

They did if they'd also managed to develop the bomb, another potential
oppurtunity cost of the V-2 program...
I am highly skeptical that not pursuing the V-2 program would have
given them the resources to pursue two large scale engineering
projects: long range bomber development and nuclear weapon development.
Nuclear weapon development alone would have been a stretch.

On the plus side the Germans had one of the best nuclear
experimentalists in Hahn, perhaps the best pure theorist in Heisenberg,
and the world's largest supply of Uranium after their capture of
Belgium.

On the negative side:
1. Germany was highly short of resources. While the US commitment to
three different means of producing fissile material (electromagnetic
U-235 separation, diffusive U-235 separation, and graphite moderated
reactor Pu-239 production) led to a more costly effort than was
strictly necessary, even the cheapest single approach required
significant resources.

2. Germany was short of time. Accurate predictions of the quantities
required for a bomb, required accurate measurements of cross sections,
and detailed numerical modeling by a relatively large body of (human)
computers. Neither were available in late 1941 early 1942 when the
German scientists were asked about the feasibility of nuclear weapons.
Without accurate cross sections and models estimates of the amount of
material required varied by several orders of magnitude, which in turn
led to large uncertainties in the time required. Germany could afford
to develop nuclear weapons if the effort took less than two years, it
could not afford to wait five years, particularly if the end result
would be a weapon so heavy it could not be delivered by an available
aircraft.

3. Personality and organizational issues hindered communication. Having
three different nuclear reactor efforts with leaders that did not get
along with one another was not conducive to progress.

4. The German scientists, particularly Heisenberg, were skeptical of
the feasibility of U-235 separation. But even if they decided to pursue
that route, U-235 separation is energy intensive, even for centrifugal
methods. In 1944 and 1945 Germany was increasingly constrained by its
energy supplies.

5. Focus on Pu-239 production meant that even if they were successful
in material production, the German nuclear weapons designers would
eventually have to confront the issue of pre-ignition, and the
subtleties of implosion design.

6. Errors in Carbon cross section measurements, due to insufficiently
pure Carbon, led to a more expensive approach of heavy-water reactors,
and a reliance on a single source of heavy water. While the problems
with Carbon purity was recognized by some, the competition for
resources meant the follow-on measurements were underfunded.

7. Allied recognition of the implications of Germany's interest in
heavy water meant that they put in a large (eventually successful)
effort into denying Germany that single source.

8. If the Germans had decided to develop nuclear weapons, Heisenberg's
potential effect on the resulting program is difficult to evaluate.
Given his reputation, his involvement was critical. His documented
estimates of material requirements varied by several orders of
magnitude: i.e., from a few tens of kilograms to a few tons. His most
influential estimates, at the time of that feasibility evaluations were
required, were on the high end of that range. It is unclear from the
available hard documentation whether that overestimate was due to a
combination of poor cross sections and an oversimplified model, or the
result of deliberate obstruction on his part. Comments by Heisenberg
and others on how his motives and abilities might have affected his
estimates are highly suspect. If the overestimate was unintentional
then detailed collaboration with others would have led to the rapid
correction of problems, if they were deliberate, then he could have
greatly delayed progress. (Note the Farm Hall transcripts are only an
additional source of confusion on this point. The first day after
hearing of Hiroshima, he repeats his estimate of several tons of
material. Another day, after being reminded that he had made lower
estimates at one time, he gives a more reasonable (a few tens of
kilograms of U-235) and well justified estimate of the material
required. Why did he repeat that overestimate that first day, when he
knew how to obtain a more accurate estimate? Forgetfulness, an
unwillingness to correct the most widely known number, a desire to
mislead the allies, or a combination of a disbelief in the feasibility
of U-235 separation and a lack of Pu data?)