5 ms·

I was going to say it fired a slug through a cylindrical piece of material, but decided to verify this on Wikipedia. It turns out: >> For the first fifty years

I was going to say it fired a slug through a cylindrical piece of material, but decided to verify this on Wikipedia. It turns out: >> For the first fifty years after 1945, every published description and drawing of the Little Boy mechanism assumed that a small, solid projectile was fired into the center of a larger, stationary target.[31] However, critical mass considerations dictated that in Little Boy the larger, hollow piece would be the projectile. I had never heard this before and was in denial reading the part above that. So either this key detail was kept secret for 50 years, or somehow history has been changed to confuse would-be bomb makers. I wonder how this detail came to light. Edit: Following the reference is was this guy: https://en.wikipedia.org/wiki/John_Coster-Mullen https://en.wikipedia.org/wiki/John_Coster-Mullen

ncmncm 5y ago
Moreso: a set of hollow rings. So, maybe the rings didn't nest together until they hit the target.
ramesh31 5y ago
>So either this key detail was kept secret for 50 years, or somehow history has been changed to confuse would-be bomb makers. I wonder how this detail came to light. Making a nuclear bomb has nothing to do with the knowledge of its' construction. Detailed plans are freely available to anyone who is interested. The reason you can't make a nuke is that the enrichment process of a suitable amount of fissile material requires nation-state level of industrial output. It is physically impossible for a small rogue actor to make a bomb from scratch. Germany during WWII, for example, was far advanced toward a bomb years before the Manhattan project, but their industrial capacity was simply never sufficient to build it.
- acchow 5y ago
  > The reason you can't make a nuke is that the enrichment process of a suitable amount of fissile material requires nation-state level of industrial output Is this still true in the 2020s?
  - ramesh31 5y ago
    >Is this still true in the 2020s? The laws of physics haven't changed in 80 years. Even if you started with yellow cake uranium (~70% enriched, and itself already nearly impossible for a non-state actor to acquire), to reach weapons grade at >95% you'd need hundreds of tons of it, and massive industrial scale chemical facilities to convert that into uranium hexafluoride and pull out the U235 isotopes [0], where the ratio of U235 to U238 (the non-fissile isotope) is 99:1. The vast majority of the Manhattan Project was in the engineering challenges required to do this, not really in the construction of the bomb. So far, only 5 countries in the world have been able to do it. [0] https://web.evs.anl.gov/uranium/guide/uf6/index.cfm#:~:text=Uranium%20hexafluoride%20is%20a%20chemical,solid%2C%20liquid%2C%20or%20gas https://web.evs.anl.gov/uranium/guide/uf6/index.cfm#:~:text=....
    - djrogers 5y ago
      > So far, only 5 countries in the world have been able to do it. I think you’re a tad optimistic there - sadly we have many more than 5 nuclear powers today.
      - speed_spread 5y ago
        5 countries have developed Uranium enrichment facilities.
        colechristensen 5y ago
        Argentina, Brazil, China, France, Germany, India, Iran, Japan, the Netherlands, North Korea, Pakistan, Russia, the United Kingdom, and the United States There’s the list of “known” meaning publicly acknowledged countries with operating enrichment facilities, more than 5. Notice it doesn’t include Israel which more or less everyone believes has nuclear weapons meaning enrichment facilities. There are several other countries which are very reasonably believed to have or have had enrichment programs.
        5y ago
- mandevil 5y ago
  The Nth Country Experiment, in 1964, took three freshly minted Physics Ph.D's without any security clearances of any kind, gave them access to a reasonably sized unclassified physics library, and asked them to design an implosion weapon. After approximately three man-years of effort (along with some basic calculation assistance from some 1964 unclassified calculators) those Ph.D's designed a workable implosion bomb. So by 1964 it is clear that design was not the limitation: every real country can scrape together a few Physics Ph.D's for three man years of effort. I would STRONGLY disagree that the Germans were ever more advanced than the Manhattan project. The British were a bit (~9 months) ahead of the US before S-1 started (December 1941), but I've never seen any evidence that the Germans were ahead of either country at any point. Certainly the fact that they never managed to replicate CP-1, which went critical in December 1942 (and was still years of hard work away from an actual nuclear bomb) suggests that they were never very close at all. The closest I can come up with is that the discovery of nuclear fission in 1938. In that work, there were five people who collaborated closely enough that today they would have all had their names on the one paper (because of Nazis the work was published in two papers, Aryans on one, Jews on the other): Otto Hahn, Fritz Strassman, Lise Meitner, Otto Frisch, and Wilhelm Traube. Hahn and Strassman were considered Aryan enough to stay in Germany. Meitner and Frisch escaped- Frisch ended up working on the MAUD report and then at Los Alamos, Meitner stayed in neutral Sweden. Traube did not manage to escape and died in Gestapo custody in 1942. So 20% of this team ended up at Los Alamos, and only 40% managed to stay in Germany, which does somewhat point to some of the underlying problems any German bomb project would have had.
- phkahler 5y ago
  >> Making a nuclear bomb has nothing to do with the knowledge of its' construction. Detailed plans are freely available to anyone who is interested. Yes, but you don't know if those plans are viable and correct. This whole thing about the gun firing a cylinder is a case in point. People *thought" they knew how it was built sans some detailed measurements and such, but it turns out they were completely wrong on a rather critical aspect of the design.
wolverine876 5y ago
> decided to verify this on Wikipedia Please, please don't say that. :(
mandevil 5y ago
http://blog.nuclearsecrecy.com/2011/11/08/the-mysterious-design-of-little-boy/ http://blog.nuclearsecrecy.com/2011/11/08/the-mysterious-des... Especially take note of Carey Sublette's comment on the design history in the blog comments: Mr. Sublette is definitely a name to be reckoned with, as far as unclassified nuclear analysis goes. His thought, that the design was basically taken direct from the Thin Man bomb design, is an especially interesting one. As for why the unclassified world thought what it thought for so long, I always presumed it was because men in the 1940's naturally assumed that the rod moves into the long tube, not the tube moves to surround the rod. (Cut to shot of train going into tunnel.)
- dylan604 5y ago
  You mean a shot of the tunnel engulfing the train?

ncmncm 5y ago

Moreso: a set of hollow rings. So, maybe the rings didn't nest together until they hit the target.

ramesh31 5y ago

>So either this key detail was kept secret for 50 years, or somehow history has been changed to confuse would-be bomb makers. I wonder how this detail came to light. Making a nuclear bomb has nothing to do with the knowledge of its' construction. Detailed plans are freely available to anyone who is interested. The reason you can't make a nuke is that the enrichment process of a suitable amount of fissile material requires nation-state level of industrial output. It is physically impossible for a small rogue actor to make a bomb from scratch. Germany during WWII, for example, was far advanced toward a bomb years before the Manhattan project, but their industrial capacity was simply never sufficient to build it.

acchow 5y ago
> The reason you can't make a nuke is that the enrichment process of a suitable amount of fissile material requires nation-state level of industrial output Is this still true in the 2020s?
- ramesh31 5y ago
  >Is this still true in the 2020s? The laws of physics haven't changed in 80 years. Even if you started with yellow cake uranium (~70% enriched, and itself already nearly impossible for a non-state actor to acquire), to reach weapons grade at >95% you'd need hundreds of tons of it, and massive industrial scale chemical facilities to convert that into uranium hexafluoride and pull out the U235 isotopes [0], where the ratio of U235 to U238 (the non-fissile isotope) is 99:1. The vast majority of the Manhattan Project was in the engineering challenges required to do this, not really in the construction of the bomb. So far, only 5 countries in the world have been able to do it. [0] https://web.evs.anl.gov/uranium/guide/uf6/index.cfm#:~:text=Uranium%20hexafluoride%20is%20a%20chemical,solid%2C%20liquid%2C%20or%20gas https://web.evs.anl.gov/uranium/guide/uf6/index.cfm#:~:text=....
  - djrogers 5y ago
    > So far, only 5 countries in the world have been able to do it. I think you’re a tad optimistic there - sadly we have many more than 5 nuclear powers today.
    - speed_spread 5y ago
      5 countries have developed Uranium enrichment facilities.
      - colechristensen 5y ago
        Argentina, Brazil, China, France, Germany, India, Iran, Japan, the Netherlands, North Korea, Pakistan, Russia, the United Kingdom, and the United States There’s the list of “known” meaning publicly acknowledged countries with operating enrichment facilities, more than 5. Notice it doesn’t include Israel which more or less everyone believes has nuclear weapons meaning enrichment facilities. There are several other countries which are very reasonably believed to have or have had enrichment programs.
        5y ago
mandevil 5y ago
The Nth Country Experiment, in 1964, took three freshly minted Physics Ph.D's without any security clearances of any kind, gave them access to a reasonably sized unclassified physics library, and asked them to design an implosion weapon. After approximately three man-years of effort (along with some basic calculation assistance from some 1964 unclassified calculators) those Ph.D's designed a workable implosion bomb. So by 1964 it is clear that design was not the limitation: every real country can scrape together a few Physics Ph.D's for three man years of effort. I would STRONGLY disagree that the Germans were ever more advanced than the Manhattan project. The British were a bit (~9 months) ahead of the US before S-1 started (December 1941), but I've never seen any evidence that the Germans were ahead of either country at any point. Certainly the fact that they never managed to replicate CP-1, which went critical in December 1942 (and was still years of hard work away from an actual nuclear bomb) suggests that they were never very close at all. The closest I can come up with is that the discovery of nuclear fission in 1938. In that work, there were five people who collaborated closely enough that today they would have all had their names on the one paper (because of Nazis the work was published in two papers, Aryans on one, Jews on the other): Otto Hahn, Fritz Strassman, Lise Meitner, Otto Frisch, and Wilhelm Traube. Hahn and Strassman were considered Aryan enough to stay in Germany. Meitner and Frisch escaped- Frisch ended up working on the MAUD report and then at Los Alamos, Meitner stayed in neutral Sweden. Traube did not manage to escape and died in Gestapo custody in 1942. So 20% of this team ended up at Los Alamos, and only 40% managed to stay in Germany, which does somewhat point to some of the underlying problems any German bomb project would have had.
phkahler 5y ago
>> Making a nuclear bomb has nothing to do with the knowledge of its' construction. Detailed plans are freely available to anyone who is interested. Yes, but you don't know if those plans are viable and correct. This whole thing about the gun firing a cylinder is a case in point. People *thought" they knew how it was built sans some detailed measurements and such, but it turns out they were completely wrong on a rather critical aspect of the design.

wolverine876 5y ago

> decided to verify this on Wikipedia Please, please don't say that. :(

mandevil 5y ago

http://blog.nuclearsecrecy.com/2011/11/08/the-mysterious-design-of-little-boy/ http://blog.nuclearsecrecy.com/2011/11/08/the-mysterious-des... Especially take note of Carey Sublette's comment on the design history in the blog comments: Mr. Sublette is definitely a name to be reckoned with, as far as unclassified nuclear analysis goes. His thought, that the design was basically taken direct from the Thin Man bomb design, is an especially interesting one. As for why the unclassified world thought what it thought for so long, I always presumed it was because men in the 1940's naturally assumed that the rod moves into the long tube, not the tube moves to surround the rod. (Cut to shot of train going into tunnel.)

dylan604 5y ago
You mean a shot of the tunnel engulfing the train?