5 ms·

> The U.S. Government soon announced its safe return and loudly reassured the public that, thanks to the device’s multiple safety systems, the bomb had never co

by umvi 6y ago

> The U.S. Government soon announced its safe return and loudly reassured the public that, thanks to the device’s multiple safety systems, the bomb had never come close to exploding. Okay but seriously. How good are the safety mechanisms? Is there significant risk an unarmed nuke could explode if going fast enough or with enough vibrations?

nickff 6y ago
Most warheads are actually very safe, and require either a detonator, or very high heat/pressure to set them off. The most dangerous part of most weapons is actually the propellant (which free-fall bombs obviously do not contain). This is a product of what weapons are designed for; the warhead is designed to resist premature detonation, but the fuel (and oxidizer if present) must be readily and easily combustible in an engine.
Mindless2112 6y ago
> "Always/Never" shares the story of the national labs’ history of work for the safety and security of nuclear weapons. https://www.youtube.com/watch?v=DQEB3LJ5psk https://www.youtube.com/watch?v=DQEB3LJ5psk
- harywilke 6y ago
  related video on Compliant Mechanisms they briefly talk about a device to safety nuclear warheads. about a minute in and again at 10:20 https://www.youtube.com/watch?v=97t7Xj_iBv https://www.youtube.com/watch?v=97t7Xj_iBv
kryogen1c 6y ago
a relatable analog is a piece of firewood. there is enough combustible energy in a section of dead tree to kill or maim you and set off a chain reaction that will destroy everything in your house, but you neednt worry if you have wooden furnitire, even if theres a lighter on it.
- dghlsakjg 6y ago
  That doesn’t make me feel better at all. Uncontrollable fires happen all the time for predictable and unpredictable reasons
throwaway0a5e 6y ago
Really, really, really good. Making a nuclear weapon actually detonate in a nuclear manner is one of the hard problems of making a nuclear weapon. Basically you have to set the explosives off just right. An accidental detonation of the conventional parts of the bomb can't do that (short of like space re-entry speeds or some other thing that could provide the force needed even without an explosion). The fear has always been around the detonation systems since those are the only thing realistically capable of setting off a nuclear explosion. Since the 1950s as detonation systems have gotten more reliable they've added more and more redundancy so those have all sorts of interlocks to prevent them from going off if not armed and fired. It's not like an airbag where if you hook up 12v to the right pins it goes bang. They actually need to be armed and then fired which requires a whole bunch of systems doing their thing in a specific order. The systems that arm weapons (like the aircraft and rocket side hardware) are relatively sophisticated and robust and a hell of a lot of man hours have been put into them over the years because the last thing you need is a risk of ordinance going off when you're already trying to fight a fire.
- rtkwe 6y ago
  Though a conventional detonation would turn it into a dirty bomb which while almost infinitely better than a full blown nuclear detonation would still ruin a good number of lives.
- monocasa 6y ago
  Adding to this, I've heard on the grapevine that the parameters of the detonation sequence are generated from a hash of the arming code number. The arming code number isn't like a traditional code lock where there's a chip that's doing "strcmp(entered_code, CORRECT_CODE)", but instead the arming code number is a fundamental piece of how the bomb works. Without that you need the kind of state nuclear apparatus you'd need to build a bomb in the first place to reverse engineer (think a state run nuclear research lab), or at best you can remanufacture it into a much crappier bomb that probably duds to just being a dirty bomb.
  - megous 6y ago
    Seems more likely that the code is just a [part of] decryption key for the parameters, rather than some weird hashing scheme.
AnimalMuppet 6y ago
If I understand correctly, atomic weapons have a "strong link" and a "weak link". The detonation won't happen without everything firing correctly and on time; the signal to do that has to pass through both the strong link and the weak link. The strong link isn't in place until the bomb is armed. But couldn't a violent-enough accident knock the strong link into place? Yes, but that same amount of violence would destroy the weak link. (That's the point of the weak link.) So even if an atomic bomb had an accident hard enough (and lucky enough) to arm it, it still couldn't explode, because the weak link would be broken.
- megous 6y ago
  I suppose this was tested by throwing the non-armed bombs on the ground from various altitudes? :)
  - dreamcompiler 6y ago
    You are correct; no smiley needed. Plus a boatload of other torture scenarios.
jhayward 6y ago
These days, very safe. Back then? We came within one safety of h-bombing North Carolina. "The bomb’s arming mechanism had six or seven steps to go through to detonate, and it went through all but one.”
dreamcompiler 6y ago
Sandia National Labs spends huge amounts of time, energy, and money making sure US nuclear weapons turn into bricks if they are damaged or tampered with, while also being ultra-reliable if the President orders their use. It's a level of safety and reliability engineering that exists nowhere else; you simply cannot comprehend it unless you've worked there. It wasn't always this way but it's been true since the 1970s. The accident described in the article was one of several that created Sandia's engineering culture. If you somehow got your hands on a modern nuclear weapon and you had a team of PhD engineers, a year of time, and the best tools in the world, you might be able to get the radioactive material out, but you absolutely would not make it explode.
- haswell 6y ago
  This is all fascinating (and comforting). I'm curious about non-US nuclear weapons and how many of these safety measures are present in those weapons.
- nohat 6y ago
  That last sounds wildly implausible. Are you saying they booby trap it to set off the high explosive if someone tampers with it (making it a booby trapped dirty bomb)? Because otherwise there's really nothing stopping some dude with an angle grinder from getting the 'radioactive material' out in a day or two. Generally this sounds nice, but I don't really believe it without some evidence of actually motivated red teams testing the system.
  - dreamcompiler 6y ago
    When I said "you absolutely would not make it explode" I meant a nuclear explosion; I thought that was clear but perhaps not. I said you might be able to extract the radioactive materials by using brute force. You might also be able to extract the high explosives, but so what? There are far easier ways to obtain high explosive materials. The fact that you could conceivably extract the radioactive materials is why the weapons are very well guarded. The point is that if you somehow stole a weapon, you wouldn't be able to use it as designed. The engineering process for these things is highly adversarial. Layers and layers of red teams trying to break them in the conceptual phase, the design phase, the build phase, and the deployment phase. Plus coding extremely detailed computer models of the weapons and their usage scenarios and trying to make things fail in simulation. On the fastest supercomputers in the world. https://www.newswise.com/articles/sandia-weapons-program-meets-safety-design-requirements https://www.newswise.com/articles/sandia-weapons-program-mee... https://www.hpcwire.com/2020/10/01/hpe-strikes-deal-to-provide-crossroads-a-new-supercomputer-for-the-nuclear-stockpile/ https://www.hpcwire.com/2020/10/01/hpe-strikes-deal-to-provi...

by umvi 6y ago

nickff 6y ago

Most warheads are actually very safe, and require either a detonator, or very high heat/pressure to set them off. The most dangerous part of most weapons is actually the propellant (which free-fall bombs obviously do not contain). This is a product of what weapons are designed for; the warhead is designed to resist premature detonation, but the fuel (and oxidizer if present) must be readily and easily combustible in an engine.

Mindless2112 6y ago

> "Always/Never" shares the story of the national labs’ history of work for the safety and security of nuclear weapons. https://www.youtube.com/watch?v=DQEB3LJ5psk https://www.youtube.com/watch?v=DQEB3LJ5psk

harywilke 6y ago
related video on Compliant Mechanisms they briefly talk about a device to safety nuclear warheads. about a minute in and again at 10:20 https://www.youtube.com/watch?v=97t7Xj_iBv https://www.youtube.com/watch?v=97t7Xj_iBv

kryogen1c 6y ago

a relatable analog is a piece of firewood. there is enough combustible energy in a section of dead tree to kill or maim you and set off a chain reaction that will destroy everything in your house, but you neednt worry if you have wooden furnitire, even if theres a lighter on it.

dghlsakjg 6y ago
That doesn’t make me feel better at all. Uncontrollable fires happen all the time for predictable and unpredictable reasons

throwaway0a5e 6y ago

Really, really, really good. Making a nuclear weapon actually detonate in a nuclear manner is one of the hard problems of making a nuclear weapon. Basically you have to set the explosives off just right. An accidental detonation of the conventional parts of the bomb can't do that (short of like space re-entry speeds or some other thing that could provide the force needed even without an explosion). The fear has always been around the detonation systems since those are the only thing realistically capable of setting off a nuclear explosion. Since the 1950s as detonation systems have gotten more reliable they've added more and more redundancy so those have all sorts of interlocks to prevent them from going off if not armed and fired. It's not like an airbag where if you hook up 12v to the right pins it goes bang. They actually need to be armed and then fired which requires a whole bunch of systems doing their thing in a specific order. The systems that arm weapons (like the aircraft and rocket side hardware) are relatively sophisticated and robust and a hell of a lot of man hours have been put into them over the years because the last thing you need is a risk of ordinance going off when you're already trying to fight a fire.

rtkwe 6y ago
Though a conventional detonation would turn it into a dirty bomb which while almost infinitely better than a full blown nuclear detonation would still ruin a good number of lives.
monocasa 6y ago
Adding to this, I've heard on the grapevine that the parameters of the detonation sequence are generated from a hash of the arming code number. The arming code number isn't like a traditional code lock where there's a chip that's doing "strcmp(entered_code, CORRECT_CODE)", but instead the arming code number is a fundamental piece of how the bomb works. Without that you need the kind of state nuclear apparatus you'd need to build a bomb in the first place to reverse engineer (think a state run nuclear research lab), or at best you can remanufacture it into a much crappier bomb that probably duds to just being a dirty bomb.
- megous 6y ago
  Seems more likely that the code is just a [part of] decryption key for the parameters, rather than some weird hashing scheme.

AnimalMuppet 6y ago

If I understand correctly, atomic weapons have a "strong link" and a "weak link". The detonation won't happen without everything firing correctly and on time; the signal to do that has to pass through both the strong link and the weak link. The strong link isn't in place until the bomb is armed. But couldn't a violent-enough accident knock the strong link into place? Yes, but that same amount of violence would destroy the weak link. (That's the point of the weak link.) So even if an atomic bomb had an accident hard enough (and lucky enough) to arm it, it still couldn't explode, because the weak link would be broken.

megous 6y ago
I suppose this was tested by throwing the non-armed bombs on the ground from various altitudes? :)
- dreamcompiler 6y ago
  You are correct; no smiley needed. Plus a boatload of other torture scenarios.

jhayward 6y ago

These days, very safe. Back then? We came within one safety of h-bombing North Carolina. "The bomb’s arming mechanism had six or seven steps to go through to detonate, and it went through all but one.”

dreamcompiler 6y ago

Sandia National Labs spends huge amounts of time, energy, and money making sure US nuclear weapons turn into bricks if they are damaged or tampered with, while also being ultra-reliable if the President orders their use. It's a level of safety and reliability engineering that exists nowhere else; you simply cannot comprehend it unless you've worked there. It wasn't always this way but it's been true since the 1970s. The accident described in the article was one of several that created Sandia's engineering culture. If you somehow got your hands on a modern nuclear weapon and you had a team of PhD engineers, a year of time, and the best tools in the world, you might be able to get the radioactive material out, but you absolutely would not make it explode.

haswell 6y ago
This is all fascinating (and comforting). I'm curious about non-US nuclear weapons and how many of these safety measures are present in those weapons.
nohat 6y ago
That last sounds wildly implausible. Are you saying they booby trap it to set off the high explosive if someone tampers with it (making it a booby trapped dirty bomb)? Because otherwise there's really nothing stopping some dude with an angle grinder from getting the 'radioactive material' out in a day or two. Generally this sounds nice, but I don't really believe it without some evidence of actually motivated red teams testing the system.
- dreamcompiler 6y ago
  When I said "you absolutely would not make it explode" I meant a nuclear explosion; I thought that was clear but perhaps not. I said you might be able to extract the radioactive materials by using brute force. You might also be able to extract the high explosives, but so what? There are far easier ways to obtain high explosive materials. The fact that you could conceivably extract the radioactive materials is why the weapons are very well guarded. The point is that if you somehow stole a weapon, you wouldn't be able to use it as designed. The engineering process for these things is highly adversarial. Layers and layers of red teams trying to break them in the conceptual phase, the design phase, the build phase, and the deployment phase. Plus coding extremely detailed computer models of the weapons and their usage scenarios and trying to make things fail in simulation. On the fastest supercomputers in the world. https://www.newswise.com/articles/sandia-weapons-program-meets-safety-design-requirements https://www.newswise.com/articles/sandia-weapons-program-mee... https://www.hpcwire.com/2020/10/01/hpe-strikes-deal-to-provide-crossroads-a-new-supercomputer-for-the-nuclear-stockpile/ https://www.hpcwire.com/2020/10/01/hpe-strikes-deal-to-provi...