6 ms·

... if you happen to have a critical mass of enriched Uranium [1] laying around in your garage. [1] Preferably not in a single lump.

m_mueller 4y ago
isn't getting the weapons grade Uranium (or Plutonium) what is most difficult about making a bomb anyways? My assumption is, once a terrorist group has achieved that, and has transported / smuggled it to their target, it's game over anyways. Harbor towns must be particularly vulnerable to this, considering the amount of shipping containers going through there...
- danbruc 4y ago
  For a simple bomb you want Uranium, Plutonium emits too many neutrons which are likely to cause a small chain reaction while your critical mass is in the process of forming and this predetonation can then blow everything apart before a proper critical mass has been formed. A gun type design where you just smash two subcritical lumps of metal into each other is, as I remember, nearly impossible to achieve with Plutonium you can realistically produce. EDIT: Interestingly another commenter says that this actually was a Plutonium design.
- tsimionescu 4y ago
  No, making a true atomic bomb is extremely difficult science and engineering. Now, a dirty bomb, which is just a conventional explosive together with radioactive material - designed to spread radioactive material instead of releasing the fission energy into one giant explosion - is easy to create, but not that much more effective than just a conventional bomb. It would trigger a massive cleanup effort, and it would surely give some people cancer later down the line, but it wouldn't be that spectacular.
  - danbruc 4y ago
    No, it is not that difficult, at least if you are fine with not having the most efficient weapon. You take a metal pipe, put a lump of Uranium and some explosive at each end and to a first approximation you are done. The USA did not even test their gun type design before dropping it onto Hiroshima because it was so simple that they were confident that it will just work.
- gonzo41 4y ago
  Extracting u238 from 235 is a hard process. Using flourine gas, it requires you to turn an ore, to a metal, then to gas and then back to metal. If terrorists can get that done they should quit terrorism and just open a chemical plant
  - GTP 4y ago
    But they would not, as terrorism isn't about making money.
    - SideburnsOfDoom 4y ago
      Terrorism isn't about solving extremely hard chemical engineering scaled process problem either.
      - throwaway0a5e 4y ago
        It's not about becoming a commercial pilot or truck driver either but those are a means to an end.
        SideburnsOfDoom 4y ago
        I'm not aware of any terrorist who actually became a commercial pilot, merely those who took a few lessons (1). And I think that's at the upper end of the lengths that terrorists will go to: Past a certain point the low-tech approaches are just way more "bang for the buck", so to speak. And past a certain specialisation of skills, it's way more effective to get that high-paying job and donate to political causes. 1) https://www.sandiegouniontribune.com/lifestyle/people/sdut-garza-flight-instructor-hijacker-september-11-2015jan25-story.html https://www.sandiegouniontribune.com/lifestyle/people/sdut-g...
adastra22 4y ago
It’s not hard to get uranium. You can buy it on Amazon. It is enriched uranium that is hard to come by. I’m guessing the low cost for this project is that he found a way for low enriched uranium to go supercritical.
- danbruc 4y ago
  Enriched Uranium was of course implied but I edited the comment now. Another commenter mentioned that it was a Plutonium design, in which case the Plutonium was almost certainly not part of the bill.
ddalex 4y ago
I feel(*) it's not about the critical mass, but the critical density - that's why you need strong compression (either chemical explosives, or xrays from a smaller nuclear bomb) to trigger the explosion (exponential runoff chain reaction). So this guy figured out how to create the critical density for 2k USD worth of components, which is actually the "hard" part of building a bomb. (*) not a nuclear physicist
- danbruc 4y ago
  You don't have to compress the material if you have enough but if you can compress it, then you can achieve detonation with less material.
  - thombat 4y ago
    But it's a plutonium design, which according to common wisdom is too fissile for slow assembly but needs both compression and enough inertia to stop it from exploding with a very low yield.
    - danbruc 4y ago
      I meant in general, for Plutonium you realistically need an implosion type design, but I think theoretically you could even have a gun type Plutonium bomb, just making clean enough Plutonium is totally uneconomical.
      - consp 4y ago
        And you still need a looooong barrel and a fast moving plutonium part (see the thin man design on wikipedia and then extrapolate from there) even creating near close enough pure plutonium since economically you won't have pure.
        bayouborne 4y ago
        "Parsons’ first order of business was the plutonium gun. Because it needed a muzzle velocity of at least 3,000 feet per second it would have to be 17 feet long. It should weigh no more than a ton, a fifth of the usual weight of a gun that size, which meant it would have to be machined from strong high-alloy steel. It would not require rifling but needed three independently operated primers to make sure it fired. Parsons arranged for the Navy’s gun-design section to engineer it." - Richard Rhodes - The Making of the Atomic Bomb
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thombat 4y ago
Apparently it's a plutonium design, which is interesting because if it's using implosion then the detonation timing and quality of the explosives is commonly thought to be critical (notably the "Fat Man" plutonium bomb was tested before being dropped on Hiroshima, whereas the uranium bomb design wasn't all-up tested before Nagasaki as it was held to be obviously reliable)
- dilyevsky 4y ago
  which means that's even harder to come by bc unlike uranium there's no naturally occurring plutonium on Earth
- topynate 4y ago
  I imagine that between the '40s and '70s many of the really hard problems became a lot easier. E.g. using solid-state electronics for the timing, modelling shaped charges as a textbook exercise rather than a research problem, etc. What surprises me is that he managed to get a dirt-cheap initiator.
  - manholio 4y ago
    Maybe he designed a geometry that can achieve the required implosion speeds with slow, easily available explosives ex. AN, KN, AP etc. The size of the device (a container) seems to suggest this. The actual initiation is the easy part and would have been easy in the 70s, exploding wires that are subjected to a number of kilo Ameperes by some kind of avalanche, solid state switch.
    - topynate 4y ago
      I meant a modulated neutron initiator, not the explosive detonator. India was still using vapour deposition of polonium to make theirs, around the same time. I'm no engineer but that sounds like it costs a lot more than $2000.
      - deleted 4y ago
        [deleted]
deleted 4y ago
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madaxe_again 4y ago
Or you can just buy a (literal) boatload of smoke detectors (americium) and medical waste (curium) and make an americium bomb - or use a neutron gun to transmute your americium into plutonium via curium.
- danbruc 4y ago
  The last time someone was going down that road it did not end too well.
oxfordmale 4y ago
....and you don't mind being lifted out of bed at 3am by the security services in your country, face a lengthy interrogation and a potential prison sentence.

m_mueller 4y ago

isn't getting the weapons grade Uranium (or Plutonium) what is most difficult about making a bomb anyways? My assumption is, once a terrorist group has achieved that, and has transported / smuggled it to their target, it's game over anyways. Harbor towns must be particularly vulnerable to this, considering the amount of shipping containers going through there...

danbruc 4y ago
For a simple bomb you want Uranium, Plutonium emits too many neutrons which are likely to cause a small chain reaction while your critical mass is in the process of forming and this predetonation can then blow everything apart before a proper critical mass has been formed. A gun type design where you just smash two subcritical lumps of metal into each other is, as I remember, nearly impossible to achieve with Plutonium you can realistically produce. EDIT: Interestingly another commenter says that this actually was a Plutonium design.
tsimionescu 4y ago
No, making a true atomic bomb is extremely difficult science and engineering. Now, a dirty bomb, which is just a conventional explosive together with radioactive material - designed to spread radioactive material instead of releasing the fission energy into one giant explosion - is easy to create, but not that much more effective than just a conventional bomb. It would trigger a massive cleanup effort, and it would surely give some people cancer later down the line, but it wouldn't be that spectacular.
- danbruc 4y ago
  No, it is not that difficult, at least if you are fine with not having the most efficient weapon. You take a metal pipe, put a lump of Uranium and some explosive at each end and to a first approximation you are done. The USA did not even test their gun type design before dropping it onto Hiroshima because it was so simple that they were confident that it will just work.
gonzo41 4y ago
Extracting u238 from 235 is a hard process. Using flourine gas, it requires you to turn an ore, to a metal, then to gas and then back to metal. If terrorists can get that done they should quit terrorism and just open a chemical plant
- GTP 4y ago
  But they would not, as terrorism isn't about making money.
  - SideburnsOfDoom 4y ago
    Terrorism isn't about solving extremely hard chemical engineering scaled process problem either.
    - throwaway0a5e 4y ago
      It's not about becoming a commercial pilot or truck driver either but those are a means to an end.
      - SideburnsOfDoom 4y ago
        I'm not aware of any terrorist who actually became a commercial pilot, merely those who took a few lessons (1). And I think that's at the upper end of the lengths that terrorists will go to: Past a certain point the low-tech approaches are just way more "bang for the buck", so to speak. And past a certain specialisation of skills, it's way more effective to get that high-paying job and donate to political causes. 1) https://www.sandiegouniontribune.com/lifestyle/people/sdut-garza-flight-instructor-hijacker-september-11-2015jan25-story.html https://www.sandiegouniontribune.com/lifestyle/people/sdut-g...

adastra22 4y ago

It’s not hard to get uranium. You can buy it on Amazon. It is enriched uranium that is hard to come by. I’m guessing the low cost for this project is that he found a way for low enriched uranium to go supercritical.

danbruc 4y ago
Enriched Uranium was of course implied but I edited the comment now. Another commenter mentioned that it was a Plutonium design, in which case the Plutonium was almost certainly not part of the bill.

ddalex 4y ago

I feel(*) it's not about the critical mass, but the critical density - that's why you need strong compression (either chemical explosives, or xrays from a smaller nuclear bomb) to trigger the explosion (exponential runoff chain reaction). So this guy figured out how to create the critical density for 2k USD worth of components, which is actually the "hard" part of building a bomb. (*) not a nuclear physicist

danbruc 4y ago
You don't have to compress the material if you have enough but if you can compress it, then you can achieve detonation with less material.
- thombat 4y ago
  But it's a plutonium design, which according to common wisdom is too fissile for slow assembly but needs both compression and enough inertia to stop it from exploding with a very low yield.
  - danbruc 4y ago
    I meant in general, for Plutonium you realistically need an implosion type design, but I think theoretically you could even have a gun type Plutonium bomb, just making clean enough Plutonium is totally uneconomical.
    - consp 4y ago
      And you still need a looooong barrel and a fast moving plutonium part (see the thin man design on wikipedia and then extrapolate from there) even creating near close enough pure plutonium since economically you won't have pure.
      - bayouborne 4y ago
        "Parsons’ first order of business was the plutonium gun. Because it needed a muzzle velocity of at least 3,000 feet per second it would have to be 17 feet long. It should weigh no more than a ton, a fifth of the usual weight of a gun that size, which meant it would have to be machined from strong high-alloy steel. It would not require rifling but needed three independently operated primers to make sure it fired. Parsons arranged for the Navy’s gun-design section to engineer it." - Richard Rhodes - The Making of the Atomic Bomb

deleted 4y ago

[deleted]

thombat 4y ago

Apparently it's a plutonium design, which is interesting because if it's using implosion then the detonation timing and quality of the explosives is commonly thought to be critical (notably the "Fat Man" plutonium bomb was tested before being dropped on Hiroshima, whereas the uranium bomb design wasn't all-up tested before Nagasaki as it was held to be obviously reliable)

dilyevsky 4y ago
which means that's even harder to come by bc unlike uranium there's no naturally occurring plutonium on Earth
topynate 4y ago
I imagine that between the '40s and '70s many of the really hard problems became a lot easier. E.g. using solid-state electronics for the timing, modelling shaped charges as a textbook exercise rather than a research problem, etc. What surprises me is that he managed to get a dirt-cheap initiator.
- manholio 4y ago
  Maybe he designed a geometry that can achieve the required implosion speeds with slow, easily available explosives ex. AN, KN, AP etc. The size of the device (a container) seems to suggest this. The actual initiation is the easy part and would have been easy in the 70s, exploding wires that are subjected to a number of kilo Ameperes by some kind of avalanche, solid state switch.
  - topynate 4y ago
    I meant a modulated neutron initiator, not the explosive detonator. India was still using vapour deposition of polonium to make theirs, around the same time. I'm no engineer but that sounds like it costs a lot more than $2000.
    - deleted 4y ago
      [deleted]

deleted 4y ago

[deleted]

madaxe_again 4y ago

Or you can just buy a (literal) boatload of smoke detectors (americium) and medical waste (curium) and make an americium bomb - or use a neutron gun to transmute your americium into plutonium via curium.

danbruc 4y ago
The last time someone was going down that road it did not end too well.

oxfordmale 4y ago

....and you don't mind being lifted out of bed at 3am by the security services in your country, face a lengthy interrogation and a potential prison sentence.