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I am a bit skeptical of this. Not even the Germans were close to building an atom bomb and it was their scientists that figured out the physics. If Japan did ha

I am a bit skeptical of this. Not even the Germans were close to building an atom bomb and it was their scientists that figured out the physics. If Japan did have any real plans on the board it probably had more to do with stolen intelligence garnered from the States. Also, it is unlikely anyone would have realistically expected uranium to be delivered to Japan by U-boat in 1945.

dekhn 11y ago
This is well documented in detail in "Making of the Atomic Bomb". They had the will, but not the means. They had much of the knowledge, but not all of it. It's unlikely in any outcome of the war that they would have been able to refine enough uranium to make a useful bomb and then deliver it.
Someone 11y ago
The part of Germany sending uranium to Japan is well-documented, and I have never heard someone doubt that it is true. See https://en.m.wikipedia.org/wiki/German_submarine_U-234 https://en.m.wikipedia.org/wiki/German_submarine_U-234.
- peterfirefly 11y ago
  I love the name :)
hga 11y ago
it was [ German ] scientists that figured out the physics. Not exactly, although they contributed a lot to the early work. If we start from "splitting the [heavy] atom", the first practical method, a German radiochemist was the first to recognize what happened, and the German physicist he first forwarded this information and her nephew figured out how it worked. But those two were Jews in exile, and most of the following more practical stuff was figured out, correctly at least, by scientists outside of Germany. Inside, they suffered a couple of disasters, a silly failure to get an higher priority for the project, and an incorrect evaluation of using graphite as a moderator, limiting them to heavy water. Which we made sure through sabotage that they couldn't get more/enough of. But if you put on your alternate history cap, note Heisenberg and Himmer's relationship from when they were school kids, direct all the V-2 resources into the bomb, who knows? Many on both sides were legitimately worried the Germans would get the bomb in time. As for the Japanese, no way. Besides what you read in the article, thermal diffusion was all but a failure in the US, among other things required fantastically too much steam, and was only revived to provide somewhat enriched feed stock into the caltrons (modified cyclotrons), and later into the gaseous diffusion plant before it fed the caltrons. ADDED (forgotten while drafting): centrifuges were of course obvious, and about the first thing we tried, but were beyond the state of the art then. 1,200 pounds of uranium at the normal 0.72% U-235 would not come close to yielding one critical mass, and for gun assembly apparently you need more like 3 times the normal pressure critical mass, although it doesn't all have to be of the highest grade.
- argumentum 11y ago
  Imagine if Hitler's worldview focused cultural rather than racial superiority .. we might all be speaking German.
- sandworm101 11y ago
  I read somewhere that after being captured by the allies some german physicists were recorded speaking in disbelief about the bomb. They were under the impression that any bomb would have needed many many times as much enriched uranium (think tons) resulting in weapons too big for aircraft. That was an indication they hadn't done much criticality research with enriched material.
  - hga 11y ago
    Those guys at least weren't up on the state of the art. Early rough calculations indicated a huge mass might be required, which is why the Einstein–Szilárd letter to FDR said "A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air." On the other hand, with as far as I know no more info than the Germans had, Otto Frisch and Rudolf Peierls estimated in early 1940 that a kilogram of U-235 might do it, see https://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls_memorandum https://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls_memoran... They pretty much laid out the correct physics mechanism (fast neutrons) and were only off by a factor of 15 on the amount required; pity for Adolph that they were Austrian and German Jews self-exiled in England by then.
  - InclinedPlane 11y ago
    Google "Farm Hall transcripts", that's what you're thinking of. But you're quite right. Heisenberg used an incredibly faulty method of calculating critical mass. And everyone around him simply deferred to his expertise. His method involved considering a branching tree of neutron chain reactions inside a sphere of fissile material, and if this tree can grow to include about 1 mole of material then that should be about enough to release enough energy for a "bomb". The reality is that it's completely unnecessary for an entire neutron chain-reaction tree to be encompassed within fissile material. All that matters is that on average from generation to generation there is a multiplication of neutrons, which will then grow geometrically incredibly rapidly. And that can happen even with many "branches" of the tree leaving the sphere and not contributing to future reactions.
InclinedPlane 11y ago
Germany was severely hampered both by Hitler's poor leadership as well as several key mistakes by top nuclear scientists, which resulted in the perception of a bomb not being feasible.

dekhn 11y ago

This is well documented in detail in "Making of the Atomic Bomb". They had the will, but not the means. They had much of the knowledge, but not all of it. It's unlikely in any outcome of the war that they would have been able to refine enough uranium to make a useful bomb and then deliver it.

Someone 11y ago

The part of Germany sending uranium to Japan is well-documented, and I have never heard someone doubt that it is true. See https://en.m.wikipedia.org/wiki/German_submarine_U-234 https://en.m.wikipedia.org/wiki/German_submarine_U-234.

peterfirefly 11y ago
I love the name :)

hga 11y ago

it was [ German ] scientists that figured out the physics. Not exactly, although they contributed a lot to the early work. If we start from "splitting the [heavy] atom", the first practical method, a German radiochemist was the first to recognize what happened, and the German physicist he first forwarded this information and her nephew figured out how it worked. But those two were Jews in exile, and most of the following more practical stuff was figured out, correctly at least, by scientists outside of Germany. Inside, they suffered a couple of disasters, a silly failure to get an higher priority for the project, and an incorrect evaluation of using graphite as a moderator, limiting them to heavy water. Which we made sure through sabotage that they couldn't get more/enough of. But if you put on your alternate history cap, note Heisenberg and Himmer's relationship from when they were school kids, direct all the V-2 resources into the bomb, who knows? Many on both sides were legitimately worried the Germans would get the bomb in time. As for the Japanese, no way. Besides what you read in the article, thermal diffusion was all but a failure in the US, among other things required fantastically too much steam, and was only revived to provide somewhat enriched feed stock into the caltrons (modified cyclotrons), and later into the gaseous diffusion plant before it fed the caltrons. ADDED (forgotten while drafting): centrifuges were of course obvious, and about the first thing we tried, but were beyond the state of the art then. 1,200 pounds of uranium at the normal 0.72% U-235 would not come close to yielding one critical mass, and for gun assembly apparently you need more like 3 times the normal pressure critical mass, although it doesn't all have to be of the highest grade.

argumentum 11y ago
Imagine if Hitler's worldview focused cultural rather than racial superiority .. we might all be speaking German.
sandworm101 11y ago
I read somewhere that after being captured by the allies some german physicists were recorded speaking in disbelief about the bomb. They were under the impression that any bomb would have needed many many times as much enriched uranium (think tons) resulting in weapons too big for aircraft. That was an indication they hadn't done much criticality research with enriched material.
- hga 11y ago
  Those guys at least weren't up on the state of the art. Early rough calculations indicated a huge mass might be required, which is why the Einstein–Szilárd letter to FDR said "A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air." On the other hand, with as far as I know no more info than the Germans had, Otto Frisch and Rudolf Peierls estimated in early 1940 that a kilogram of U-235 might do it, see https://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls_memorandum https://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls_memoran... They pretty much laid out the correct physics mechanism (fast neutrons) and were only off by a factor of 15 on the amount required; pity for Adolph that they were Austrian and German Jews self-exiled in England by then.
- InclinedPlane 11y ago
  Google "Farm Hall transcripts", that's what you're thinking of. But you're quite right. Heisenberg used an incredibly faulty method of calculating critical mass. And everyone around him simply deferred to his expertise. His method involved considering a branching tree of neutron chain reactions inside a sphere of fissile material, and if this tree can grow to include about 1 mole of material then that should be about enough to release enough energy for a "bomb". The reality is that it's completely unnecessary for an entire neutron chain-reaction tree to be encompassed within fissile material. All that matters is that on average from generation to generation there is a multiplication of neutrons, which will then grow geometrically incredibly rapidly. And that can happen even with many "branches" of the tree leaving the sphere and not contributing to future reactions.

InclinedPlane 11y ago

Germany was severely hampered both by Hitler's poor leadership as well as several key mistakes by top nuclear scientists, which resulted in the perception of a bomb not being feasible.