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Comment by pram | Hacker News Reader

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

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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.

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

Oddly, the US Department of Energy's statutory responsibility for "the safety and reliability of the nuclear arsenal" is officially interpreted within the department as: safety, it goes bang when you push the button; and reliability, it makes as big a bang as it says on the tin.

Of course this "safety" has absolutely nothing to do with what the public naturally assumes is meant, which is typically that it won't go bang when you don't push the button, or leak, or be hijacked, or fall out of a plane carrying it. The DoE considers none of those its responsibility under the law.

One might guess that going bang when the button is not pressed would be extremely unlikely. But when a B-52 crew made a booboo and dropped a pair of hydrogen bombs in a farmer's field, investigation showed that all of the processes that would have set them off completed; just not all on the same bomb.

I am listening to Eric Schlosser’s book “Command and Control” at the moment and it has quite a bit of detail on this and other nearly disastrous incidents and the complete lack of serious command & control around nuclear material/weapons. We are very lucky not to have had several accidental or unwanted nuclear detonations to this point. I’ve not finished the book but I am not optimistic the situation is very much better today.

I’m actually okay with nuclear weapons not working when someone wants them to

Are you ok with them working when someone doesn’t want them to though?

This is highly unlikely. An accident, where radiation leaks, maybe, but for a nuke to go off, everything has to work flawless.

Do you need fusion plasma simulation to achieve that? Don't think so.

> Do you need fusion plasma simulation to achieve that? Don't think so.

Would you prefer to know? Or go off a hunch?

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.

> to prevent a reaction that never naturally takes place on earth

The cores of these weapons are unlike any environment on Earth. Maintaining the stockpile without running simulations is negligent.

Not building nukes guarantees a nuclear detonation will occur on earth, because The Other Side (TM) will use theirs on you.

Only if they’re on Russian military bases.

It's actually worse though. If a bomb fails 50% of the time, they will just launch 5 to have a >95% chance of a hit.

I very much agree, except for the one case, where they are supposed to blow up, or deflect an incoming asteroid.

Yikes, that’s alotta dead people when a nuke isn’t working as designed and unexpectedly detonates

US ICBM silo map https://qph.fs.quoracdn.net/main-qimg-45b10c7543ed5219a77858...

Don't misrepresent what the comment said.

> okay with nuclear weapons not working when someone wants them to

Obviously s/he hoped the weapons not to explode when fired.

Since it's not trivial to start a chain reaction that lasts long enough to create a sizeable explosion, unexpected (nuclear) explosions are a very unlikely failure mode for nuclear weapons.

Agreed, though the comment wasn’t about the _likelyhood_ of a failure

And now you've made an abusive edit; your original comment here was mocking and pointing out that it was the GP "wishing" for a failure.

GP wished for a (moderately) likely failure: failure to detonate. GP obviously didn't wish for unlikely failures, like spontaneous detonation, ICBMs all flying to Washington DC, etc.

Everyone understands you are misrepresenting the GP comment. I hope it's on accident.

We all wish that were true. Experience has shown that it is not.

Considering that there have been 0 accidental nuclear detonations, no it doesn't.

You wish that is what that meant. But the more you learn about the topic, the less confident you will be.

Pure luck.

The US military has accidentally dropped dozens of nukes out of planes (this was on the front page a few days ago) and none of them accidentally went boom. They don't spontaneously ignite, they are designed with several levels of safeguards to prevent that.

You’d think that wouldn’t you.

There is the case of the Goldsboro B52 in 1961 crash in which three bombs could fell out of a plane and could have gone off but didn’t :

https://en.wikipedia.org/wiki/1961_Goldsboro_B-52_crash

Edit: of the four bombs one was only very close to going off, and a lot of lessons were learnt from this event 60 years ago.

It's a small miracle that none of them ever went off by accident and it got perilously close to that more than once. We just got very lucky.

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.

You may guess that if you like, but it is physically impossible in this universe.

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

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.

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.

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.

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.

That's why we got the nuclear reactors we have today, the ones that can make nuclear weapon material

> 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/0301421584...

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.

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.

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.

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