7 ms·

IIRC it seems impractical because it was intended for nuclear weapons research or something like that. It's a military boondoggle.

by pram 4y ago

RF_Savage 4y ago
Yep. It's an alternative to nuclear tests to see how the physics work in real life. Sometimes it's just nice to have something to compare your simulation results to.
- adastra22 4y ago
  Also if you wanted to make really small fission bombs—like hand grenade sized—I would guess this is how you’d go around doing it.
  - ncmncm 4y ago
    You may guess that if you like, but it is physically impossible in this universe.
    - adastra22 4y ago
      Project Orion used fission bombs "the size of a soda can" to power its propulsion. Designing such bombs was a big part of the military aspect of the project and how it got government funding. Now the results are still classified, of course, but it appears they were successful from a design angle. At least the scientists involved seem to think it was possible. This source gives an estimate that a 1 kg fissile mass plutonium can yield about 100 tonnes of explosive power, which is a sphere of plutonium about 2 inches in diameter: http://nuclearweaponarchive.org/Nwfaq/Nfaq4-2.html http://nuclearweaponarchive.org/Nwfaq/Nfaq4-2.html In principle there isn't really a limit to how small you can make it, just with decreasing efficiency and (with traditional implosive designs) a higher detinator-to-fissile material ratio. Things like laser implosion remove this design constraint, however, and would let you consider things like millimeter-sized pellets.
      - ncmncm 4y ago
        1 kg is the amount of fissile material, but it needs quite a lot of high explosive around it. The file you linked says 16kg, and 28 cm by 30 cm. I suspect the soda-can sized charges you recall were conventional explosives for the small, non-nuke prototype they tried out.
      - pfdietz 4y ago
        Project Orion did not use fission bombs the size of a soda can. It may have used bombs whose CORE was the size of a soda can, but to get that to explode requires much more high explosive (than in a typical nuclear weapon) to implode it more aggressively. That's fine, as the mass of all that high explosive acts as reaction mass.
- ISL 4y ago
  Experiment is the arbiter of truth -- being able to verify that aging fissile materials continue to function as-expected is very important. It really matters that nuclear weapons go bang when you want, but not when you don't. An example of why one needs to care about such things in stockpile stewardship -- plutonium's own radioactivity means that helium is effectively being born within the crystal lattice, causing damage, distortion, and swelling. It isn't a guarantee that a bomb that worked 50 years ago will work today. https://www.osti.gov/servlets/purl/1241955 https://www.osti.gov/servlets/purl/1241955
  - 4pkjai 4y ago
    I’m actually okay with nuclear weapons not working when someone wants them to
    - aplummer 4y ago
      Are you ok with them working when someone doesn’t want them to though?
      - labster 4y ago
        Only if they’re on Russian military bases.
      - geysersam 4y ago
        Do you need fusion plasma simulation to achieve that? Don't think so.
        JumpCrisscross 4y ago
        > Do you need fusion plasma simulation to achieve that? Don't think so. Would you prefer to know? Or go off a hunch?
        geysersam 4y ago
        I'll admit it's just a hunch telling me you don't actually need experiments on extremely high temperature plasma to prevent a reaction that never naturally takes place on earth. Intuitively, simply not building a bomb seems sufficient to prevent any accidental detonations. But I'm of course no expert.
XorNot 4y ago
I wouldn't say boondoggle. The need for nuclear deterrent is back in focus, and so long as that exists then I'd much prefer we do anything but actual weapons tests.
deleted 4y ago
[deleted]
hangonhn 4y ago
What was the expected long term outcome of the nuclear test ban treaties? It seems unless there is some breakthrough in simulations and NIF type experiments, all countries with nuclear weapons will end up unsure of their weapons efficacy. Is this intentional? Is the hoped for outcome that no one has nuclear weapons they are sure will work and thus effectively disarming them? If not, are facilities like NIF what was envisioned by all the countries who have nuclear weapons? Thanks.
- lovemenot 4y ago
  I cannot speak for the people responsible for drafting those treaties, but it appears to have been a timely effort to apply multi-lateral pressure against proliferation. Put another way: for some nations to pull up the ladder. Not long-term thinking perhaps, but medium term at least. In the longer term, who could have known then or even cared how to maintain the transition to a no-test regime? What the treaties' drafters might have been thinking is now moot. Those people are long gone, it's your problem now.
pjc50 4y ago
This is a serious albatross round the neck of nuclear technologies; if they're dual-use, they'll get lots of funding, making them look expensive, while the true purpose and feature set is obscured, making them look nonsensical.
- mavhc 4y ago
  That's why we got the nuclear reactors we have today, the ones that can make nuclear weapon material
  - JumpCrisscross 4y ago
    > why we got the nuclear reactors we have today, the ones that can make nuclear weapon material No, we got ones designed to work in nuclear submarines [1]. Civil reactors don’t make weapons-grade anything. [1] https://www.sciencedirect.com/science/article/pii/0301421584900260 https://www.sciencedirect.com/science/article/pii/0301421584...

IIRC it seems impractical because it was intended for nuclear weapons research or something like that. It's a military boondoggle.

by pram 4y ago

IIRC it seems impractical because it was intended for nuclear weapons research or something like that. It's a military boondoggle.

RF_Savage 4y ago

Yep. It's an alternative to nuclear tests to see how the physics work in real life. Sometimes it's just nice to have something to compare your simulation results to.

adastra22 4y ago
Also if you wanted to make really small fission bombs—like hand grenade sized—I would guess this is how you’d go around doing it.
- ncmncm 4y ago
  You may guess that if you like, but it is physically impossible in this universe.
  - adastra22 4y ago
    Project Orion used fission bombs "the size of a soda can" to power its propulsion. Designing such bombs was a big part of the military aspect of the project and how it got government funding. Now the results are still classified, of course, but it appears they were successful from a design angle. At least the scientists involved seem to think it was possible. This source gives an estimate that a 1 kg fissile mass plutonium can yield about 100 tonnes of explosive power, which is a sphere of plutonium about 2 inches in diameter: http://nuclearweaponarchive.org/Nwfaq/Nfaq4-2.html http://nuclearweaponarchive.org/Nwfaq/Nfaq4-2.html In principle there isn't really a limit to how small you can make it, just with decreasing efficiency and (with traditional implosive designs) a higher detinator-to-fissile material ratio. Things like laser implosion remove this design constraint, however, and would let you consider things like millimeter-sized pellets.
    - ncmncm 4y ago
      1 kg is the amount of fissile material, but it needs quite a lot of high explosive around it. The file you linked says 16kg, and 28 cm by 30 cm. I suspect the soda-can sized charges you recall were conventional explosives for the small, non-nuke prototype they tried out.
    - pfdietz 4y ago
      Project Orion did not use fission bombs the size of a soda can. It may have used bombs whose CORE was the size of a soda can, but to get that to explode requires much more high explosive (than in a typical nuclear weapon) to implode it more aggressively. That's fine, as the mass of all that high explosive acts as reaction mass.
ISL 4y ago
Experiment is the arbiter of truth -- being able to verify that aging fissile materials continue to function as-expected is very important. It really matters that nuclear weapons go bang when you want, but not when you don't. An example of why one needs to care about such things in stockpile stewardship -- plutonium's own radioactivity means that helium is effectively being born within the crystal lattice, causing damage, distortion, and swelling. It isn't a guarantee that a bomb that worked 50 years ago will work today. https://www.osti.gov/servlets/purl/1241955 https://www.osti.gov/servlets/purl/1241955
- 4pkjai 4y ago
  I’m actually okay with nuclear weapons not working when someone wants them to
  - aplummer 4y ago
    Are you ok with them working when someone doesn’t want them to though?
    - labster 4y ago
      Only if they’re on Russian military bases.
    - geysersam 4y ago
      Do you need fusion plasma simulation to achieve that? Don't think so.
      - JumpCrisscross 4y ago
        > Do you need fusion plasma simulation to achieve that? Don't think so. Would you prefer to know? Or go off a hunch?
        geysersam 4y ago
        I'll admit it's just a hunch telling me you don't actually need experiments on extremely high temperature plasma to prevent a reaction that never naturally takes place on earth. Intuitively, simply not building a bomb seems sufficient to prevent any accidental detonations. But I'm of course no expert.

XorNot 4y ago

I wouldn't say boondoggle. The need for nuclear deterrent is back in focus, and so long as that exists then I'd much prefer we do anything but actual weapons tests.

deleted 4y ago

[deleted]

hangonhn 4y ago

What was the expected long term outcome of the nuclear test ban treaties? It seems unless there is some breakthrough in simulations and NIF type experiments, all countries with nuclear weapons will end up unsure of their weapons efficacy. Is this intentional? Is the hoped for outcome that no one has nuclear weapons they are sure will work and thus effectively disarming them? If not, are facilities like NIF what was envisioned by all the countries who have nuclear weapons? Thanks.

lovemenot 4y ago
I cannot speak for the people responsible for drafting those treaties, but it appears to have been a timely effort to apply multi-lateral pressure against proliferation. Put another way: for some nations to pull up the ladder. Not long-term thinking perhaps, but medium term at least. In the longer term, who could have known then or even cared how to maintain the transition to a no-test regime? What the treaties' drafters might have been thinking is now moot. Those people are long gone, it's your problem now.

pjc50 4y ago

This is a serious albatross round the neck of nuclear technologies; if they're dual-use, they'll get lots of funding, making them look expensive, while the true purpose and feature set is obscured, making them look nonsensical.

mavhc 4y ago
That's why we got the nuclear reactors we have today, the ones that can make nuclear weapon material
- JumpCrisscross 4y ago
  > why we got the nuclear reactors we have today, the ones that can make nuclear weapon material No, we got ones designed to work in nuclear submarines [1]. Civil reactors don’t make weapons-grade anything. [1] https://www.sciencedirect.com/science/article/pii/0301421584900260 https://www.sciencedirect.com/science/article/pii/0301421584...