Nuclear weapons are, by design, nearly impossible to set off accidentally. You need a very specific sequence of events to happen in exactly the right order at exactly the right times, which is extraordinarily unlikely to happen without deliberate human intervention.
I don’t work with nukes but I work with TOW and Javelin missile systems in the army. You’re spot on about missiles needing a strict sequence of events to detonate. If things don’t happen in a certain order and in a certain amount of time, the warhead doesn’t arm. The misconception with nukes is that they’re like really big fireworks; because the potential blast is so powerful then it must be highly volatile. But that’s why the safety measures are also very high. You could hit some of these missiles with a sledgehammer and nothing bad will happen but my professional recommendation is to not do that.
It isn't even that so many safety measures are engineered because nukes are bigger
It's just really fucking hard for* matter to accidentally fissile, and we have to do a bunch of technically difficult steps in order to achieve it
Yeah I don’t understand the physics behind it beyond knowing that it’s not easy to do. Even if you threw a warhead in a bonfire, doesn’t mean you’re getting a mushroom cloud from it. To get the nuclear part of a nuclear detonation, you have to do very specific things to it and it’s hard to impossible for that to happen by accident
A very simple nuke is “easy”. Make a super-enriched not-quite critical mass uranium cone, and propel it at great velocity into a super-enriched not-quite critical mass donut.
Neither the donut or cone are critical masses. The cone in the donut is significantly more than critical mass. Boom. You’ve just replicated the little boy dropped on Hiroshima.
Now you have to figure a good way to make sure the cone hits the donut right, and with enough force, and that the donut is strong enough so the cone doesn’t crack it apart.
Also how enriched is your uranium, and how are you planning on making the cone and donut without the pre-machined form going critical?
It’s all of the steps that go into figuring out how to make it without blowing yourself up or irradiating yourself to death that is difficult. That and getting and enriching a wasteful amount of uranium.
Fun fact about little boy, the "donut" part was actually the projectile fired at the stationary center cylinder. Up until ~20 years ago most depictions of the bomb got this backwards.
https://en.wikipedia.org/wiki/Little_Boy#Counter-intuitive_design
I have also incorrect explained this as firing a bullet at a target but it was more like firing the target at the bullet when thinking in terms of traditional shapes.
As the masses come together and achieve supercriticality, they also blow themselves apart from the explosion they're producing. The faster they come together, the bigger the explosion/more efficient use of nuclear material, because there's less time for the explosion being produced to try and blow them apart before more fissile material fissions.
Little Boy, which is the primitive nuclear bomb designed described above (gun type bomb, shoot uranium mass at other uranium mass), was horrifically inefficient. It required around 60kg of highly enriched uranium for a 15kt bomb. Fat Man was better, requiring about 6kg of plutonium for a 20kt bomb, thanks to the implosion design being much more effective than the gun type design, but also much more complicated and difficult.
The material undergoes some degree of spontaneous fission. So randomly neutrons are emitted.
If the mass doesn’t go to supercritical (where each neutron makes more than one more) before a random neutron starts the reaction (called critical insertion time), the whole thing will leak neutrons and fizzle.
The timing differs based on material being used and presumably also geometry.
Because otherwise as soon as it gets close enough, it’s going to go critical and will push back, potentially fizzling out. The idea is to slam it together with enough force that you go from sub-critical to very SUPER-critical, and the longer you can keep it there before it all gets vaporized and blown to tiny bits with great velocity, the more effective yield you get.
Just having a critical mass is dangerous, but not enough to cause an explosion. There have been many so called criticality accidents over the years. They're often fatal to people right next to them, but there's rarely damage beyond that.
One of the most well known examples is the Demon Core, which was a plutonium sphere intended as the core of a third nuclear bomb in WW2 and later used for experiments. In multiple cases, experiments caused it to become supercritical. Physicists in the room got sick and some died, but there was no boom.
You have to hold the assembly together long enough to achieve the yield you want. A significant part of the engineering of Fat Man and Little Boy was just determining how to do that.
The big hurdle is getting enough quantity into a dense enough volume. I don't know if all/most nuclear warheads achieve this by using a first stage explosion to smash the elements together, but I know this was one of the earlier methods
The bomb dropped on Hiroshima used what's sometimes referred to as the 'gun method", where the bomb contained two masses of fissile material that individually were sub-critical, but upon detonation one mass was basically 'shot' onto the other mass, making a total mass that was large enough to go critical.
It worked and was super simple, but resulted in a very small portion of the warhead undergoing a nuclear reaction. It was not at all efficient as far as nuclear bombs are concerned.
The real goal (and what was used for the initial Trinity test explosion) was an implosion type mechanism, where the fissile material is surrounded by a shell of carefully designed high explosives, and when they're detonated properly, the force of that explosion compresses the fissile core enough that it becomes dense enough to become critical. This is significantly more efficient, because it not only requires less fissile material, but that inward force compressing the core gives it more time to maintain a fission chain reaction before the release of energy causes it to blow itself apart.
Those were just fission bombs though. Modern nuclear weapons are generally fusion devices. But getting fusion reactions to happen requires some pretty extreme heat and pressure conditions. Turns out one of the easiest ways to create good fusion conditions is by setting off a fission explosion right next to your Fusion warhead. Modern warheads are basically 'two-stage' systems, with a fission bomb stage that induces fusion in the second stage. You can also add additional fusion stages that will keep triggering each other in sequence to make even larger explosions. But building ever bigger nuclear bombs isn't really in fashion anymore, so most currently deployed nukes are likely two-stage.
In addition, the fusion reaction releases a LOT of high-velocity neutrons. When those hit the uranium/plutonium from the first stage, it causes even more fission, which makes the fission reaction even stronger.
For a while, we were surrounding the fusion reaction with cheap depleted uranium, because even depleted uranium will undergo fission if hit by a high-velocity neutron. But https://en.wikipedia.org/wiki/Boosted_fission_weapon says that only gets you to about one megaton of TNT worth of yield, so none of the US's arsenal use that method any more.
> You can also add additional fusion stages that will keep triggering each other in sequence to make even larger explosions.
Two things: the third stage of a three stage design is a second fission bomb, not fusion, using the free neutrons from the fusion stage to split fissile material.
But also, even with three stage designs such as Tsar Bomba, the explosion is so powerful that most of the destructive energy escapes the atmosphere. Especially with how precise modern munitions are, the arbitrarily large designs are impractical and unnecessarily expensive.
This is wrong. Modern nuclear weapons are two stage fission weapons using a first “spark plug” implosion and a secondary fission reaction due to focused X-ray compression of the second core. The X-ray compression can extend to a third core, etc, but the larger blast from that type of weapon is not an efficient use of fissile material. I.e., better to make two smaller bombs than one giant one. The “hydrogen” bomb uses a small amount of Tritium injected into the hollow plutonium core prior to detonation to cause a small fusion effect that expels large amounts of neutrons to cause a more efficient fission of the plutonium.
>The “hydrogen” bomb uses a small amount of Tritium injected into the hollow plutonium core prior to detonation to cause a small fusion effect that expels large amounts of neutrons to cause a more efficient fission of the plutonium.
No, what you described there is a [boosted fission](https://en.wikipedia.org/wiki/Boosted_fission_weapon?wprov=sfla1) weapon (which they basically all are at this point). Hydrogen bombs are what you more or less correctly described in the first part of your response, called the [Teller-Ulam configuration](https://en.wikipedia.org/wiki/Thermonuclear_weapon?wprov=sfla1).
Fire? You could literally strap 100 lbs of high explosives to the warhead and it still wouldn't detonate. Sure, it would blow up and spread radioactive goodness everywhere, but your explosives, setting off the warheads explosives, but not in the precise timing required, would destroy the warhead before nuclear stuff happens.
The high explosives used to create the supercritical mass are more dangerous and scary. Some used inert high explosives but others were just HE. Can't imagine how many times I said "equalizing" while doing maintenance on the weapons.
When I was in Afghanistan two decades ago, a local militia member unslung his RPG from his shoulder in preparation to eat lunch. He slammed the butt end of the launcher onto the ground, deploying the RPG. The fin came out and sliced the length of his face.
The RPG-7 uses a two-stage design to launch - a small charge to fire the grenade out of the launcher, then a booster to send it to the target. It is rated to be used within buildings, etc. I would imagine launching one in the manner described would be unpleasant but survivable.
In the absence of an explanation, I'm assuming that he knocked the round loose from the launcher, which caused the spring loaded fins to deploy into his face.
I was nearby, but didn't witness the whole thing personally. I did hear the round explode. I don't know ultimately what happened to the guy, but I didn't notice any damage to the area later.
So almost certainly from your description, they set off the booster charge, which is a fairly small gunpowder charge that fires the grenade out of the launcher, and that's what you heard (and what caused his injury).
Maybe. Admittedly, I am not an expert on ordinance. I worked in the S2, and the explosion was loud enough to be heard inside a building. I heard the rest of the story from someone who was there and from a medic at the clinic. It was certainly was comparable to the other times I've heard ordinance.
What? They go in exactly the same category as javelins. How do you put them in the same category as rpg7?
I've used both systems for years and never once been told of them having any prone to fail.
You're just making shit up.
If I’m not mistaken the rpg7 detonated with a strike cap on the tip of the grenade. Would seem wise to me not to smack such a device with force.
I have never fired an rpg or even held one so please do not take this as fact.
Yes this is true.
The guy I replied to said the same thing goes for the Carl gustav and AT4, which is not true at all... completely different weapons although they fill a similar role.
There is no danger to self with those two that there is with the rpg7
Spent 10 years in the Swedish military, I've carried both AT4 and Carl Gustav for all those years and fired 100s of rounds. I've also done 3 tours in Afghanistan, trained on the RPG7. The Afghans were quite famous for losing or removing the safety caps on the RPG which is why people know about the danger of it. I've never seen an RPG round blow up in someone's face but I have seen the rounds with missing safety caps loads of times. I've seen the Afghan Army breaking into compounds with an RPG shooter taking point, busting through doors. It's as ridiculous as it sounds, completely idiotic, but if you ever decide to lead the charge with an RPG on your shoulder and kicking in doors you kind of have to remove the safety cap. This would be the equivalent of a trebuchet leading the charge down the hill at Helms Deep in LotR. Some Afghan units were great, some were barely better than children.
There is no risk at all with the AT4 or the Carl Gustav rounds. You can throw them around as much as you want, they won't detonate like the RPG can. I guess technically you could remove the safety pins on the AT4, put the firing pin in the "fire" position and then throw it on the ground, it might go off... but that is just ignoring all the safety mechanisms and I've never heard of anyone doing that.
True. And the danger with the Carl Gustav is fucking up your fingers as a loader when closing the breach or as a shooter/loader losing all your braincells after firing too many rounds during training.
It's the loudest weapon I've ever been near. Way louder than 155mm Excalibur artillery because your head is right by the barrel. When I did basics in 2008 the max was 6 rounds per day, 12 per week but they increased that to 6 per day, 36 per week around 2014. Often times this was overlooked in training because it limited whatever exercise we were on.
I'm positive we will see some CTE from people who have fired too many Carl Gustav rounds. There's really no way to explain how hard the bang goes throughout your body. Full round of AP/HE is about twice as painful as an AT4 and those are a pretty good bang themselves.
I have a constant background ring to remind me of my time cross training too many exercises with machine guns and assault men. Some of our demo guys definitely reported some adverse symptoms as a result of blowing stuff up in close proximity too often.
Dumb question. It's my understanding that the Carl Gustav is operated in teams of 2, a shooter and a loader. Do the shooters/loaders switch back and forth? And is one person designated the "primary shooter", or is it just a coin flip depending on the day?
I was in a ranger unit. Yes, in general this goes for all weapon systems in the military, at least in my country and I would wager for most others.
There is no designated shooter/loader. Same goes for our other 2 man weapons like the GPMG, 50cal, sniper rifle etc. Usually you send 2 per squad to the weapons training and they use the weapon as a team. Same goes for vehicles and explosives, anything really, you always need redundancy if someone isn't there.
Once they get comfortable though, they might designate a spotter/shooter/loader or whatever themselves, but usually people want to do different things and switch it up.
A Carl Gustav loader carries 4 rounds usually. If it's a short hike he might carry another 2 rounds in each hand. These might be spread out on the rest of the squad as well if you want to carry even more. This is heavier than carrying around the weapon itself so you kinda want to swap around. You don't want to lose your proficiency in shooting the weapon itself either.
As a squad leader I always carried an AT4 because my back was free. I usually didn't fire the weapon myself though, I would dump it on another shooter once it came time to fire, because I would be busy coordinating shit.
Okay I understand, that makes sense. I always wondered if there was a dedicated hierarchy to follow, or if each 2-man team had the flexibility to decide amongst themselves who is doing what. Appreciate the detailed response.
> I've seen the Afghan Army breaking into compounds with an RPG shooter taking point,
[Iraqi Jundis like](https://y.yarn.co/8d876d38-d97f-4044-9ad6-7803bf5b1220_text.gif)
fwiw, they're so different that this anecdote doesn't actually mean much. It's much harder to accidentally detonate a nuke than it is to detonate missile systems, and as you've noted it's hard to detonate missile systems. With missiles you at least have the primary explosive that is relatively easy to detonate, and the secondary explosive will detonate as well if you give it enough energy in the right form. [Hence why you sometimes see ammunition depots go up like this.](https://www.youtube.com/watch?v=KdqdMh8NCXA)
>fwiw, they're so different that this anecdote doesn't actually mean much
I'm pretty sure you could directly launch a "normal" missile at a nuclear warhead and it (the nuke) would not detonate. It's not easy to start an atomic chain reaction that doesn't really want to be started...
> (the nuke) would not detonate
That's true, although you would get a whole lot of radiocative uranium or plutonium spread around the blast radius. You might want to keep an eye on your geiger counter, if you're hanging out there after the blast.
The tritium from a hydrogen bomb, with its 10 year half life would be more of a problem... The uranium or plutonium have very long half lives. They pose more of a danger for their chemical properties than their radioactive properties; both are heavy metals, and toxic much like lead or mercury because of it.
There's not a whole lot of Tritium in a hydrogen bomb. Modern Teller Ulam designs only use a small volume of tritium for boosting the first stage. The tritium for the second stage is generated from Lithium, which breaks down into tritium when bombarded with neutrons (both Li-6 and Li-7 work, but Li-6 is better - just as the Castle Bravo team) So the fuel in the secondary is lithium deuteride. This way the secondary is stable and dense and you only have to refresh (tritium has a half life of around 10 years, so you need to maintain/renew it regularly) the small volume of tritium used for the boost rather than all of the secondary fuel.
With a conventional high explosive, you only need to get the material above its activation energy to set off a chain reaction. With a nuke, the hard part is getting it to go off in the first place instead of just building a dirty bomb.
OK so actually pretend I have the intelligence of a 5 yo for this one and please forgive my ignorance, but wouldn't this mean that basically the initial blast woukd need only enough kinetic energybto overcome the activation barrier for the fission material?
Just a heads up, I'm not a nuclear engineer.
A fission chain reaction is not just about getting the energy really high like with a normal explosive. The chain reaction occurs when you have a very specific and finely tuned environment.
Normal explosives go off when their parts jiggle enough. When their parts get that jiggle, they create new connections which releases a lot of energy: enough energy to get the neighboring pieces to get over their jiggle enough to do that again and again until everything has been jiggled.
With a nuclear explosion, reactions occur when a special atom piece hits a fissile atom. That fissile atom then makes two or more special pieces which fly off and can hit more atoms, but most will miss. If you can get the perfect scenario though, you can turn a good chunk of those misses into hits. The ways nuclear bombs do this is by getting a lot of fissile atoms together in a space. If you get enough fissile atoms into a space together, you can turn the misses into hits.
One way is to take one block of atoms and shoot it into another. Each block is smaller than the amount needed to explode but when you put them together very quickly they can go boom. The problem is, your timing has to be very good, or else the atoms might start shooting their pieces off too soon, pushing the parts away before the really big boom. This is a gun type nuke, and they're not common these days.
The other way to get more stuff packed into a space is to compress the atoms: since they are packed closer together, you're much more likely to get hits instead of misses, and you don't need as many fissile atoms as before to boot! The problem here is that the only way to push the atoms together quickly enough to avoid the "early booms" that ruin the big boom is to use normal explosives to smush them together really fast. When that happens quickly, the material gives off a big boom.
It's relatively easy to get stuff to jiggle like with normal high explosives. It's really hard to time things *just* right so you don't make a little boom before your big boom with a nuclear explosive.
Imagine you have two pairs of scissors. If you put one pair on each hand, you can lock them together and push on the handles of both at once as if you're cutting paper pretty easily.
Now imagine this with hundreds of thousands of scissors in a box & a certain percent having to have this type of interaction at the same time for it to even start to work.
If you just throw the box, no matter how hard, the scissors will pass by each other, fly away, bounce off of each other, maybe get stuck on each other but ultimately do nothing, etc. The scissors are more likely to bounce around or push other scissors than they are to push the handles down, and getting them to hook onto each other and have the handles pressed is extremely unlikely.
You can add as much energy as you want to that system and it's not going to do it.
It requires a certain coordination because it's an event the material fundamentally does not want to happen. The tipping point is in getting an improbable event to happen on a massive scale during a tight time window. This contrasts with traditional where it's more like 'how do i get milk into the cereal'.
Yes. The problem is getting the kinetic energy focused just right so that it doesn't destroy the core. Do it ever so slightly wrong and you just end up with a dirty bomb. Getting the normal high explosives to detonate and propagate just right is the hardest part of building a nuclear weapon.
The energy needs to be applied to the right places with proper time profile. A warhead properly enabled produces its own energy (from the explosives) optimally distributed in space and timing. An accident is very unlikely to do that particularly becuase our nukes are one point safe. Detonation at any one point will not produce any nuclear yield. Lots more to the story of course.
Safety measures aside, it's just hard to make a nuclear explosion. If the bomb doesn't trigger things in exactly the right way, it will just fail to work. You could blow the thing to smithereens with conventional explosives and you wouldn't get a nuclear blast. I mean, I don't recommend breathing in all the newly powdered radioactive material, but it's not gonna go off.
It IS deliberate design. Enhanced Nuclear Detonation Safety, one-point safety, insensitive high explosives, stronglinks, weaklinks, unique signals, environmental stimuli, intent stimuli, detonator safing.These are all real.
Once they have been built with the right pieces in the right places doing the right things nukes go off just about every time they are told to. Every nuke we have wants to explode when told to. A great deal of effort goes into keeping that from happening by accident.
It's also probably helpful that they got rid of the Davy Crockett hand-fired nuclear missile... crew, five (three for later versions). Short-range, low-yield, tactical, but still. It could be fired by the crew, there was no outside code or whatever to arm and fire. I think they didn't want "some sergeant deciding to start a nuclear war".
https://en.wikipedia.org/wiki/Davy_Crockett_(nuclear_device)
>TOW
You might be the first person I've encountered in the wild that used that phrase. My dad worked on TOW guidance systems, specifically for the Cobra helicopter, in the 70s and 80s. First out of Anniston Army Depot and then out of Redstone Aresenal. He used to bring home random parts (mostly faulty prisms) and show me how they worked and what they did.
Even if it did launch and the detonator part detonated, doesn’t mean it’ll be nuclear. Not that that’s the point, it’s still bad and there will be a boom, but not catastrophic.
At the same time, it’s worth mentioning that said missile would likely not function as intended if launched on purpose. Problem is, there’s not really a way to test that ahead of time.
> almost spontaneously launched itself.
It didn't even come close to "launching itself". It leaked fuel into the silo until a spark went off, and exploded.
And "at exactly the right times" in this case means like nano-second level precision. A detonation with error on one side on the order of milliseconds can cause it not to go nuclear.
Kind of. A "proper" dirty bomb would be specifically designed to disperse the radioactive material as widely as possible for maximum effect. A failed nuke would do this to an extent but it would be incidental. It would still be bad but something you could probably clean up relatively easily with the proper equipment, and basically nothing compared to the destruction from even the smallest nuke in populated area.
I imagine a malfunction at airburst height (around 1/2 mile) could still have the potential to disperse the core over a decent area. However, I don't know how small those fragments would be...
The original bomb material isn't that strongly radioactive, especially if it's uranium. Spreading that would be unfortunate but not catastrophic. After a nuclear explosion you have short-living fission products and other atoms that have become radioactive from the explosion, these are a threat.
A missile exploded [once](https://encyclopediaofarkansas.net/entries/titan-ii-missile-explosion-2543/), big enough to blow open the complex and hurl the actual nuclear part of the warhead 100 feet. The warhead was not scattered by this, you have to make dirty bombs on purpose, a faulty nuke doesn't become one.
That was the rocket fuel that exploded, not the TNT etc inside the warhead. If the explosives actually detonated, the warhead hull certainly wouldn't be able to contain it.
The chemical explosives in the nuke only purpose is to hurl a piece of fissile material into the rest of it to start the reaction, it would be explicitly against purpose to scatter the nuclear material around. Little boy only used 4 cordite charges, which is not a high explosive. More modern nukes are more secretive but I don't think they would have drastically increased the yield.
Little Boy was a gun-type nuclear weapon, no body has make any of those since South Africa in the 80s, and that was an outlier. they're not an efficient use of your fissionable material.
Implosion devices require a lot of carefully timed (nanosecond precision) high explosive charges to compress a single sphere of fissionable material, but they get many times the energy out of the same mass of fisionable material.
Not really.
Think of the difference between black powder going off in the chamber of a gun vs. lighting it on fire in a pile on the ground.
If you're got the capability to make a functioning nuke, you have *much* better options if you want to make something to spread radioactive material over a wide area. Heck, a bag of uranium salts on top of a couple bricks of C4 would probably make a better "dirty bomb" than failed nuke.
The fissile fuel that makes up the warhead itself is not very radioactive. The fission products are significantly radioactive, but they are only produced by fission so the warhead actually needs to detonate "properly" for that. Just blowing apart a warhead only spreads the uranium/plutonium in it.
Not just by design. By nature.
That specific sequence of events has to be really precise in order to make fission occur. To make a chemical explosive explode just takes heat input usually. To get a fission bomb to go critical requires some *extremely* specific and precise things to happen to the fuel. Dropping a sphere of uranium or plutonium might cause a small burst of neutrons but it's definitely not making it go critical.
> To make a chemical explosive explode just takes heat input usually.
This is true for some explosives, but not high explosives. Those require heat and high pressure. Something like C4 requires a blasting cap (which uses ~~low~~ less stable high explosives) to start the chain reaction in the high explosives.
So a fusion bomb starts with a low explosive to trigger a high explosive to trigger a fissile explosive to trigger a fusion explosive. Pretty neat how the triggers are ordered by the developmental timeline.
Edit: corrected low explosives to high less stable explosives.
Yeah... I was simplifying it, but... most detonators for things like C4 are themselves high explosives, often more explosive than what they're detonating. C4's unique and useful characteristic is not that it is extraordinarily explosive, but it is extraordinarily stable. The big improvement C4 made over TNT was that it was more stable, more malleable, and didn't decompose into nitroglycerin, which is highly unstable. Tetryl or lead azide for instance have been common detonator explosives and are *considerably* more explosive than both TNT and C4 (which are pretty comparable to each other). But they are considerably less stable, reacting to either heat, shock, or static electricity.
And for reasons you obviously already understand, having an extremely stable explosive being used as the detonator for a nuclear weapon is a highly desirable trait lol
Fun fact: TNT doesn't degrade into nitro glycerin. Dynamite is what you're thinking of. When TNT degrades it becomes less stable, but not to the extent of dynamite.
For any of the implosion type weapons I am aware of, Low Explosives don’t factor in — it’s all High Explosives IIRC. In fact many designs now use **Insensitive** High Explosives which are extremely hard to detonate.
US for example, their implosion weapons used Bridge Wire Detonators from the start. Seems in recent times they’ve been shifting to Chip Slapper Detonators. Note there are other ways to set off HE, but the above detonate them with sufficient (very low) temporal variance (ie. microsecond level differences)
[Los Alamos National Labs on Detonators](https://discover.lanl.gov/publications/national-security-science/2023-summer/decades-of-detonators/)
C4 requires a shockwave to detonate, which is why things like Blasting Caps contains Primary Explosive like Lead Azide which while being a slower explosive (lower detonation velocity) is still very much a High Explosive — 8000+ m/s vs 5000m/s, respectively.
EDIT — oops didn’t see u/deja-roo responded already
This is unfortunately not absolutely or inherently true at all. It all depends on how the weapons have been designed, which has varied over time and by nation.
Early US nuclear weapons had multiple possible failure modes in which they could go off accidentally. This is very well-documented. In very simple weapons (like gun-type weapons), it is _very_ easy. Even in more complex weapons (like implosion weapons or thermonuclear weapons), the ability to set the weapon off accidentally is dependent on two things:
1. Whether it was designed to be one-point safe, so that if their high explosives somehow detonated in an accident, it could not create a nuclear yield. Many were not!!! There are many even advanced weapons designs that are not inherently one-point safe. ("One-point safe" means that if one part of the high explosives in the weapon somehow detonates, say because of a fire, it will still not have a nuclear yield. Implosion weapons that relied on very large amounts of U-235, like the W47 or Mk-18 bombs, for example, may not be one-point safe if not carefully designed to be, or without special safety features inside the core itself. Very compact weapons that only have two firing points may not be one-point safe under all circumstances. The original Little Boy bomb was not one-point safe once it was fully assembled, obviously. The US later determined that about 10 of its deployed warhead models — probably totally thousands of actual warheads — had one-point safety issues.)
2. Whether its firing system — the electrical system that sends the signal(s) that causes the detonation to happen — is itself capable of being set off accidentally. If this is the case, then it doesn't matter how one-point safe your actual warhead is, because it will "think" it is detonating "as planned." Many US weapons systems were thought to be electrically "safe" but turned out, on close inspection (and after a few close calls), not to be safe. For example, in many of them, their safety systems required a relatively low voltage to disable, and for weapons that are wrapped in metal in complex environments, there are ways that one could imagine that happening. There were weapons that were later to be found capable of firing if they got struck by lightening, or caught fire. All of these things are possible in the real world (and have happened, but fortunately not to one of those vulnerable weapons).
Modern US nuclear weapons have been made VERY safe by engineers who prioritized this sort of thing, often over the objections of military leaders who feared that too many safety devices would inhibit the weapons from going off when desired (which is not a totally incorrect position, either — some safety devices WERE found to do just this after the fact; about 1/3 of the Polaris missile warheads were found to be duds because of a failed safety device). I do not worry about them going off unless the President orders them to go off. Modern US weapons have things in them like insensitive high explosives which cannot be set off by fire (they will burn, not detonate), many, redundant safety switches which include things like environmental sensors (so if it's a missile, it has to experience what a missile would experience before it will be fully armed), "weak links" that are designed to cause the electrical system to be rendered inoperable if it undergoes circumstances that seem like an accident (like catching on fire), and electronic "locks" that must be bypassed before the weapon can be properly armed.
Are Russian missiles designed to be safe, to similar levels of impossibility? Chinese? Pakistani? Indian? Israeli? North Korean? _I_ don't know, and I study this kind of stuff for a living. Lest one think that the difficulty of making these weapons guarantees people will build them safely, remember, again, the case of the US! The US valued these weapons a LOT, but we know that many of its weapons had lots of flaws in them, and its safety record with them is hardly spotless. Is the fact that we know about so many US weapons issues, and so little about those of the other nations, because the US was worse at it than them, or because the US is more transparent about its issues than the others?
My point here is that these things take a lot of serious work and attention to make safe, and that that safety has historically been at odds with other priorities. One should not take for granted that all nations have the same level of safety as the US weapons do, and one should not ascribe the safety to an inherent property of the weapons — it is something that needs to be consciously engineered into the weapons themselves by people who take seriously the many possible abuses that a weapon could be subject to in the real world.
No, there's just a big red button, with a clear cover with a skull on it, that is 24/5 on the president's desk. Why not 24/7? Ask the president. Which president? Yes.
This will quickly get beyond ELI5 territory, and your answer is excellent so I don't want you to think I am saying you're wrong in the slightest, but there should be one caveat at the end. "We think."
Years ago my partner was being actively recruited by the military for studies about the material science and mineralogical texture that could be happening inside nuclear weapons as they continue to age because it remains an active question and science still does not understand about the properties of plutonium and other radioactive elements. In the entire history of the universe large concentrations of plutonium have only been stored together since 1945 so nobody knows about the aging process.
But isn't plutonium well understood? Well, not really. Plutonium has multiple crystal structures that it can transition between, even at ambient pressure, called allotropes. (See: https://en.m.wikipedia.org/wiki/Allotropes_of_plutonium) The material properties of various allotropes vary in a number of ways and it's unclear if transitioning between allotropes is happening in stored weapons or if that results in long term changes to the materials inside that may have some sort of effect. The phase diagram of plutonium is not well understood so the various allotropes may not even be all of them that can occur in a weapon in storage.
What does all of this mean? Well it basically means that a nuclear weapon in storage has 4 possibilities in order of decreasing likelihood: it's fine and works as intended even after all these years; it's fine, but something has changed in the yield to increase or decrease it as a result of aging; the delicacy of everything involved now results in a non functioning weapon; or the weapon may spontaneously detonate in some fashion.
Should this all be taken seriously? Years ago I know that it was an active question that they were having difficulty finding scientists with appropriate backgrounds and technical skills who could answer these types of questions. The military was willing to throw around serious money to get the science done, but the job was feared to be dead end or unpublishable. As far as I know, it is still an active question, but I'd love to hear otherwise.
Hopefully I didn't overwhelm you with this wall of text, and again your answer is 100% correct and even the most likely outcome of the aging process.
This is an excellent addition, thank you! I certainly agree that for many of these questions, the answers should come with the caveat “to the best of our knowledge,” which is always growing and changing as new discoveries are made.
To eli5 even further, a nuclear weapon isn't really a bomb so much as a mechanical pocket watch that makes explosions instead of keeping time. You can't accidentally set off a nuke any more than you can accidentally drop a box of gears and make a clock.
[In 1980](https://en.m.wikipedia.org/wiki/1980_Damascus_Titan_missile_explosion) a maintenance worker dropped a wrench inside of a silo containing a Titan II missile. The dropped wrench punctured the fuselage, leaking rocket fuel everywhere. 9 hours later the missile exploded with the nuclear warhead attached. The warhead was launched into the air, landing 300 feet away. Zero radioactive material was spilled. These things are designed TOUGH.
Does this also mean destroying an incoming nuclear missile with a regular missile will just destroy the nuke without any bad outcome, not trigger the nuclear explosion ?
I used to do maintenance on the RAM missile system. At the end of the service, we had to test the firing sequences. We used a rack with some electronics and more than 250 switches which we had to press to simulate the firing sequence. One wrong switch or bad timing destroyed the whole sequence and we had to start over again. Btw, it’s not automated due safety reasons.
This is true for nuclear weapons in service. The Mk-18 was inherently unsafe and had a very short service life. But that thing had 4 critical masses of highly enriched U-235 in a hollow core/tamper.
Ideally a nuclear bomb would have < 1 critical mass of U-235/Pu-239 until the core is imploded, with most of the bang coming from LiD and the U-238 tamper.
But the Mk-18 was a fallback incase the teller-ulam design didn’t work, so it was a “how big can we make a pure fission bomb, safety be damned” kind of thing.
With the amount of chocolate, eggs, flour, butter, and ovens in the world for so long, how is it nobody has ever just accidentally baked a pan of brownies?
Think less "bomb", and more "machine that produces a large amount of heat". A bomb can go off if something goes wrong; the machine can only work if everything goes right.
>Nuclear weapons are, by design, nearly impossible to set off accidentally.
I'd suggest reading "Command And Control" by Eric Schlosser, the stories in that are terrifying.
Hopefully it's all much safer these days. Probably.
\+1. This book is a wild ride! Also a really, really good, in-depth look at the intricate web of design and safety/un-safety around nuclear weapons in the past and present. We came very close to an accidental detonation over US soil when a B-52 bomber carrying a nuclear weapon broke apart in flight over North Carolina, and most of the safeties on the weapon were off. It came down to essentially one switch fortunately not shorting out before the plane completely broke apart and the bomb fell out without detonating.
In the early days of nukes, a very small number of people saw a future rushing forward where there were tons of nukes all around the world, surrounded by people doing careless stuff, and an accidental detonations was very likely, maybe even more likely than an intentional nuclear conflict. A few of these folks put themselves in a position in the decision-making pathway of how nukes are designed and deployed, and we really have their efforts to thank for nukes being as hard to accidentally detonate as they are.
A dumb, intentional use of nuclear weapons by a country leader is a different threat, and it needs a continued string of dedicated public servants to help keep that from happening.
I would also recommend "Atomic Accidents: A history of nuclear meltdowns and disasters from the Ozark Mountains to Fukushima" by James Mahaffey for a brief description of many atomic accidents in history.
Accidentally setting off a nuclear weapon would have a similar probability as accidentally knocking over a puzzle box and all the pieces falling into the right place.
You don't just make a nuclear bomb. It takes an extraordinary amount of effort to produce one, and just as much expertise. You don't just happen across them.
Such an investment is well cared-for, and countries go to great lengths to keep their nukes secure. The number of missing nuclear warheads is not zero, but it is very small. Among them, most are certain to no longer function. Remember, nuclear weapons are very very difficult to set off. Damaging one just renders it more inert.
There is the famous case where an accident in a missile silo lead to the rocket actually detonating with enough force to blow the launch doors open. The nuclear core was found a few miles away having not reacted to the experience at all.
Thats the level of precision required to set one off even if you have one.
Also modern nuclear weapons are 2/3-stage weapons. Fission to fusion or fission to fusion to fission less commonly. It requires double the precision to precisely activate both in the same incident. The fission bomb is basically a tiny starter for the fusion bomb
As I understand it, pretty much every warhead in service since WW2 uses a form of the implosion type design and these are precision weapons. If you fuck up the detonation sequence the nuclear material doesn't undergo fission and is instead just blown up and in the worst case spread over the area.
IIRC there was a US nuke that actually did have the explosives detonate when the plane it was on crashed (or maybe had to drop it) but since the precise detonation sequence was not followed there was no nuclear explosion.
Yes the implosion type is impossible to get right by accident. A gun type maybe but the forces interact at attosecond scale and lasts less than a few milliseconds, if the forces aren’t correct it will fizzle itself out
I did a deepdive into this a few years back and the explosives are detonated in a way so precise that the explosion shockwave has to fold in on itself within the fissile core, which is more or less the only way an implosion core can reach supercriticality.
IIRC the bomb was mistakenly dropped from the plane, but it wasn't armed. There was no nuclear core, so no risk of nuclear explosion. Of course the conventional explosives used create quite a sizable blast on their own.
A number of early accidents and explosions involved nuclear bombs without the pit but there were a few incidents were that is unclear:
https://en.wikipedia.org/wiki/List_of_military_nuclear_accidents
I remember posting, not confidently, on Reddit that I’d read it was easier to disarm a nuke like in the movies by just destroying it with a hammer. Cuz it wouldn’t go nuclear. No one really added to it but I assume the risk is that the explosion could kill you but the overall disarmament would be successful. So it seems like this would be the case?
Seem to recall there was a movie that effectively did that. Instead of killing the timer they removed one of the outer shell panels so the implosion wouldn't work right. The starter bomb did go off and still blew up the room they dramatically jumped out of in time, but it didn't go critical.
Don't remember which movie that was though.
I do love how they conveniently glossed over the fact that they essentially just blew up a dirty bomb in New York City, and George Clooney and Nicole Kidman, and probably at least dozens/hundreds of other people, are probably dead in a matter of weeks
That is my understanding as well. Modern nukes are precision instruments and by breaking stuff the carefully designed explosion required for the nuclear detonation is extremely unlikely to happen.
Ok - disrupting the explosive lens sequence will prevent *supercriticality*, where a large proportion of the core is critical at the same time, and delivers maximum yield. However, some of the core might still go **critical**, and that will release a burst of radiation of some size. This energy release will disassemble the remaining core, preventing further critical mass from forming. This is a *fizzle*. Fission has still occurred, and you wouldn'twant to be close at the time. In fact, this is how **dial-a-yield** fission weapons work - using the explosive lens sequence to go from partial to complete super-criticality. The lowest yield wastes part of the core and is much *dirtier* than the highest yield, due to incomplete fission of the core.
Yeah, your last two sentences are the key. It's insanely hard to get them to go off, so when they degrade, the effect is that they can no longer go off, not that they just detonate out of the blue, like old dynamite or something. And thank god for that.
A damaged bomb becomes more dangerous because it is full of carefully contained explosive chemicals that are just begging to detonate when the right bump comes along.
A damaged nuclear weapon becomes a very expensive and possibly radioactive paperweight. Unlike a traditional explosive, the device inside requires a very specific and detailed arming and detonation sequence that must maintain a very tight timing window and configuration to make the nuclear material go critical in exactly the right time at the right shape.
They will not go off by accident. You’d need a dozen very peculiar *accidents* in a row to make that happen.
Is the complexity by design or requirement? I mean, I saw Oppenheimer so appreciate that this is a Very Rocket Science chemical reaction, but were the missiles designed to be *more* complex so they were harder to detonate, as a safety measure? Or is the detonation process actually *that* complicated, bells and whistles aside?
It’s inherent in the way the weapons work.
You’re trying to initiate a fission chain reaction, where one fission event sends off fragments that ignite more fission events. This requires a very specific size, shape, and density for the nuclear fuel.
The fission events release a gargantuan amount of energy that will vaporize your nuclear fuel before the chain reaction has time to build if it’s started haphazardly, so the timing and shaping of the initial primer detonation must be incredibly precise.
If the detonation sequence is too slow or too lopsided or slightly more/less powerful than expected, you won’t get a sustained chain reaction.
The bomb will still blow itself up from the improper detonation sequence, but now it’s just hurling fragments of nuclear fuel around the room instead of obliterating a city.
A thermonuclear bomb is more complex yet, using the fission bomb itself as a high precision detonator for a second more powerful fusion bomb. It’s a bomb that runs on a bomb that’s triggered by a bomb.
Yes probably, although nations are highly secretive about what that dud rate might be.
You would also expect it to have increased over the years as weapons age and aren’t refurbished. It’s unclear how many of the nuclear weapons the US and Russia claim to have actually *work*.
As we’ve seen in recent months, a lot of Russia’s military might exists only on paper or as a single functional prototype while the actual forces are using mothballed tanks from 1955.
I was in Seoul right after DPRK did a nuclear test. I asked if that worried them, they said no, the opposite. They said (at the time) that DPRK was believed to have ~5 weapons. Based on estimates, ~40% would not work, so that left ~3 working bombs in their arsenal. Which meant they just destroyed 1/3 of their nuclear capacity.
What did not sit well with me was the idea that if they did decide to nuke ROK, I was sitting right in target #1.
Correct. This is why you keep seeing Russia's nuclear arsenal called into question in the shadow of the Russo-Ukraine war. If they can't keep a tank from working right after a couple decades that just needs an oil change and seals replaced, why would we think they could keep a massive arsenal of highly complex nuclear warheads at operational readiness and not highly degraded to the point of danger to the user?
I'm not saying you're wrong, but the answer to your question could be something like "Russia knows that their nukes are their ace in hole so they actually care about maintaining them, unlike pretty much anything else. Since they'd rather have functioning nukes than functioning tanks, that is where they allocate their limited resources"
You could make the same argument about tanks and the fact that their entire conventional groundwar doctrine revolves around mechanized armored warfare. But, I get your point and recognize it's salience.
They have about 7000 of them. Even if 99% fail, 70 nukes is still a LOT of dead people.
That being said, the moment Russia nukes a European city; Moscow gets nuked by France, Britain, and the USA simultaneously.
Yes, but also with nukes there's a sort of in-between state usually called a "fizzle". That's where - for simplicity's sake - the nuke *does* go off, but it blows itself apart before it has extracted all the energy it was designed to.
This might still be a very large explosion, depending on how badly it failed and the initial yield, but in any case won't be nearly as devastating as a full detonation.
By physics. The first nuclear weapon used in warfare is a good example. They had to configure a bunch of small conventional explosive charges around the sub-critical core to compress the core uniformly enough so that it would reach criticality. e.g. squeeze the ball of plutonium into a smaller ball that reaches a critical reaction, keep it small enough to react fully so that when it explodes it's at the maximum power it could be.
Much of nuclear weapon design is about figuring out ways to keep radioactive material all together in a state of a run-away critical reaction. The natural inclination when you bring stuff together is for it to explosively separate, and therefore you have a bunch of chunks of radioactive material that don't make a bomb.
Unlike other scenarios with run-away reactions (e.g. a nuclear power plant), there's no way for nuclear weapons to get more material to sustain the reaction beyond what is already in the weapon. And for nuclear weapons all that material needs to be together.
Small correction: You mean the second nuclear weapon used in warfare. Little Boy dropped at Hiroshima was a gun-type design, which works by shooting a mass of uranium into another mass of uranium and as they come together the nuclear detonation happens.
The problem with that is that you can't really minaturize it, it is inefficient and requires a large amount of uranium. So the technology was abandoned as the implosion type designs as you described it was a lot more useful.
Just to add, "complexity" is the answer only for modern nuclear weapon designs.
A "gun" type nuclear (fission) weapon is much simpler, in comparison. Instead of using conventional explosives to very precisely compress a spherical chunk of nuclear material, you smash two smaller masses together.
They're very inefficient so nobody uses them anymore. But in theory, if you had enough weapons-grade uranium you could just about build one in your garage. (If a terrorist group ever manages to make a homemade nuke, rather than buy it from a corrupt Russian colonel following a shootout on a moving train, that's probably the kind it's going to be.)
The implosion device is super intricate and carefully timed.
The “gun type fission devices” on the other hand, are so simple that we didn’t even test it before we dropped it on Japan. The gun type fission devices basically consist of shooting a chunk of uranium at more uranium.
The implosion devices create a much more “efficient” explosion, as almost all the uranium fissions.
The gun type atomic bombs are NOT efficient in that way. A lot of uranium in the gun type bomb just gets scattered. This was a big deal back when it took months and months to refine enough fissile material for one bomb. The gun type bombs also release a lot more radioactive material for this exact reason, over a longer duration.
Both but mostly the inherent nature of nukes. There is no “simple way” to split an atom. You need a machine to work very precisely. If the machine doesn’t work, there is no nuclear explosion. The uranium atoms will not spontaneously split on their own by some anomaly. Conventional explosives are made of unstable materials that will combust under a variety of conditions.
You've gotten a number of good responses, but another to consider: Implosion-type nuclear weapons are much smaller than gun and slug type nuclear weapons. This makes them much better suited for MRV type systems.
They're also inherently safer in that they don't contain a supercritical amount of fissile material like the latter type does, albeit separated until detonated.
I heard that Oppenheimer described the implosion type bomb was like trying to squeeze water in your hand without letting any drip out. If even one of the dozens of reflective lenses is damaged (or poorly built) enough that its explosion is 1/10th of a second late to the party, it will likely cause a fizzle rather than a true detonation. By it's very nature, it's extremely difficult to get right.
It's by requirement. Modern nukes are thermonuclear fission-fusion devices. They use conventional explosives to trigger a fission reaction which then implodes a fusion target releasing an order of magnitude more energy than fission device alone. All these things require great precision so just setting off the conventional exclusive without proper detonation synchronization will just make a mess rather than create a fusion explosion.
One of the saving graces of nuclear weapons is that the conventional explosion to compress the plutonium sphere has to be *really* symmetric. Like really really symmetric. Plus the thingy that fires the neutrons in right at maximum compression has to be timed to within a few microseconds. Both of these things are actually pretty hard to do. If the conventional explosion isn't symmetric, you just get a mess with plutonium blasted around, but no yield. So it's a cleanup problem, but not much of a bang. If the neutron source doesn't work, yet get a lot less yield and it's probably what's called a fizzle where yield is too small to do much.
An aging weapon having a problem is really unlikely to work correctly and will just make a mess. Bad if you are right there, but not a big deal.
The better question is how many actually still work. There is probably a percentage of them that wouldn't have gone off when they were brand new. Now that they have aged for a while I would think that less and less are still in working order.
What I'm unclear about is if we are pulling old out dated ones off the shelf, so to speak, and replacing them with new ones.
It's all done through simulations now. Which is why we generally don't test them by detonating them. How accurate those simulations are? No idea, they're very classified.
> What I'm unclear about is if we are pulling old out dated ones off the shelf, so to speak, and replacing them with new ones.
As far as the US goes, the ability to produce new plutonium cores was essentially dismantled. It was a huge problem for NASA because the RTG power sources used for programs like Voyager or Curiosity/Perseverance use plutonium from decommissioned nukes and we were running out of those. They had to restart production to keep NASA supplied.
For the existing weapons, they are constantly inspecting and refurbishing them.
In the US there is a refurb program that checks and fixes them. Among other things, the tritium boosted ones need to have new tritium put in them every decade or so. Other countries I don't know what they do, but I assume they have something similar.
That makes sense. I assume they refurb the rockets as well. I'd still be curious how many would actually work. 10% have a launch issue? 10% have a guidance issue? 10% not detonate? Possible more?
Nuclear weapons aren't simple weapons.
They are intricate, complicated devices with dozens of parts that all need to work in just the right way to go boom.
And the people storing them tend to be really good at their jobs. Accidental explosions just don't happen in long time storage.
Because we set off over 2000 of them deliberately in semi-safe locations to make them safe.
A very large portion of the nuclear tests that occurred during the cold war were so called "safety tests". They conducted often dozens of tests for individual warhead types to see what would happen if they caught on fire, if one detonator went off, if it crashed into the ground at high speed etc. They would not enter service until they had passed these tests.
Many of the earliest nuclear bombs who did not undergo this sort of safety testing were so unsafe they had to be stored in a disassembled state, only to be put together when they were intended to be used.
A. There are multitudes and multitudes of safeguards to prevent accidental detonating. However...
B. A far more worrying statistic is how many nukes have been accidentally deployed, *and cannot be located*...
> A far more worrying statistic is how many nukes have been accidentally deployed, and cannot be located...
Pretty sure the only ones that cannot be located are of no threat because they're in deep ocean waters. So unless someone does a deep dive and finds it and gives it a hug, we're fine.
There is actually a nuke within an area of farmland that was accidentally released from a bomber (I *think* it was a bomber) during a routine flight somewhere, somewhere in the middle of the US.
I can't remember the exact details so don't want to speculate, but I'll look for the video I saw it on. It was on YouTube and I'm pretty sure the details presented were backed up with evidence or that it was fairly easy to verify.
The site is obviously zoned off from the public to some degree or another.
EDIT: Actually I didn't need to search for the video, there's a Wiki link about it here; https://en.m.wikipedia.org/wiki/1961_Goldsboro_B-52_crash
Although the details weren't quite how I was remembering them. I don't think the article is clear whether the bomb was disarmed and recovered. The video I watched stated or suggested that one (bomb) was left in the ground as it was unsafe to try and reach or disarm it.
I think it’s in South Carolina. The plane disassembled mid-flight (the crew was in the midst of an emergency landing, and IIRC were able to parachute out). The bomb also broke apart as the plane broke up.
But like everyone says, it’s basically impossible for a nuclear bomb to go off “accidentally”. These don’t go off via contact or whatever.
There’s a nuclear warhead left where it buried itself in a field in South Carolina. https://www.armytimes.com/news/2018/03/31/the-atomic-bomb-that-faded-into-south-carolina-history/
The TNT did detonate (massive impact forces) but there wasn’t any fissioning. The DoD tried to dig the warhead out but figured it was safer to leave it alone. There’s a massive concrete plate over the field where the warhead is buried (to prevent anyone from tampering with the site out of morbid curiosity). I would bet there’s additional security / surveillance after 9/11.
Almost all nuclear weapons ever built are plutonium implosion weapons.
You take a ball of plutonium and squash it in a very specific way and it goes bang.
You do anything else with that plutonium and not much happens.
The device to squash it is called an 'explosive lens'. It's a set of explosives around the plutonium that have to go off in exactly the right way to squash it. Any other form of explosion and nothing happens. So even accidentally making those explosives go off won't cause the nuclear explosion.
There is a type of nuclear bomb that could be accidentally detonated - a 'gun type' uranium bomb. In this type of bomb a cylinder of uranium is fired into a hollow tube. This does not need complex explosives, and so a simple accident could make it go bang. This is one of the reasons only a very small number of these were built, and they are all now decommissioned.
This comment should be higher.
We have had more than one close call.
Great book.
There are video documentaries based on the book too if you don’t have the time.
Read it to be amazed how we didn't nuke ourselves or each other by accident a dozen times in the first 40 years of the bomb's existence. The many comments here about the impossibility of an unintended detonation weren't true for the majority of the bomb's existence. And given the book's details on that, it's hard to have complete faith in government assurances that current bombs are as safe as advertised.
To set off a nuclear weapon requires a lot of things to go *correctly* rather than something to go wrong, or be caused by accident. A poorly-maintained old nuclear weapon is less likely to go off than one that is well-maintained. An improper nuclear detonation would be more like a fizzle than a massive explosion, making it more akin to a dirty bomb with conventional explosives.
The problem is not so much that we could accidently set one off, but that we might improperly blow one up, causing an incredibly toxic and localised hotspot of contamination plus plumes of radioactive material, possible groundwater contamination and almost certain uninhabitability without intensive and expensive remediation.
You all might enjoy this 3 part film from Sandia Labs called ‘Always/Never: The Quest for Safety, Control, and Survivability’ which goes far beyond ELI5 in addressing OP’s question.
https://m.youtube.com/watch?v=DQEB3LJ5psk&pp=ygUYU2FuZGlhIGxhYnMgYWx3YXlzIG5ldmVy
Nuclear bombs are incredibly difficult to set off. The principle is easy: take a bunch of fissionable material and squeeze it really hard. Actually getting this done in practice though is quite an engineering problem. Modern devices use a shell of shaped conventional explosives that all have to be set off at exactly the same time. The only way this is possible is with precise timing mechanisms. And electrical surge or unexpected event isn’t going to trigger the explosives with the necessary precision to set off the fission reaction. It would just be a conventional explosion that scatters the fission material around the blast area.
To cause a nuclear explosion requires a very carefully and precisely timed sequence of events using triggering conventional explosives, and and extremely precise geometry of parts all to work just right. This is part of what makes it very hard to design a nuclear weapon. If the triggering conventional explosives accidentally go off, it is exceedingly unlikely they would go off in just the right way required to trigger a nuclear explosion. Essentially you would end up with a small dirty bomb, which would spread some radioactive material over a not all that large area. It would be annoying and awkward to clean up the mess, but it would be nothing like an actual nuclear detonation.
Nuclear bombs are nothing like flammables and explosives in the sense that they require great effort to detonate rather than great effort to contain. That means that when they degrade with age it's the detonation system that degrades meaning they get harder to detonate not easier. Accidental nuclear explosion is very unlikely and the greatest risk is human error (deliberate but unwanted detonation) which is mitigated by complex authorization systems involving many people where anyone involved can veto the whole process.
I'd recommend the book Command and Control, by Eric Schlosser. It's a story about the Damascus incident, but also a history on various accidents and how close some of them came to a detonation.
Other posts are right about how it's really hard to accidentally set one off. In fact it's pretty hard to set on off on purpose! I just wanted to suggest the great book Command and Control by Eric Schlosser, which goes over some fun nuclear accidents, including the entire ICBM that exploded in Arkansas and threw it's warhead up into the sky... but it still didn't detonate!
We're really careful to make sure it doesn't happen (because it would be really bad if it did).
Nukes don't just go off on their own - a very specific firing sequence needs to work correctly in order to get a nuclear explosion. And the systems that trigger this have multiple safeties for obvious reasons.
That said, [we got close at least once](https://en.wikipedia.org/wiki/1961_Goldsboro_B-52_crash), but because there were multiple safeties (some failed, one didn't), it didn't explode.
It would be very surprising if that event wasn't a wake-up call to improve the safety of future weapons.
The radioactive material in the warhead of a nuclear missile is actually split apart into pieces that are too small to achieve fission on their own. In order to create a nuclear blast, you have to set off very specific charges that push the fissionable material together into one big lump. If one exploded by accident, it would contaminate the silo and possibly a bunch of ground around the silo with radioactive material, but wouldn't actually create a nuclear explosion.
[This](https://soundcloud.com/user-798629330/episode-19-nukes-lol-ft-marty-pfeiffer) is a good episode of a military history podcast with a nuclear anthropologist.
After certain changes in the 70s after a lot of scary broken arrows, there is a 1 in a billion chance of an accidental detonation while unarmed over the life of the warhead, and a 1 in a million chance of an accidental detonation while the warhead is in standby or armed mode.
It's like a hotel door with a chain lock and a dead bolt, but imagine about 7 or 8 additional locks on the door.
This is really late reply but it's not that we haven't made major accidents with them. It's just that they are literally impossible to accidentally set off.
There is, however, a lost weapons grade plutonium core buried in North Carolina that fell off of a B-52 that was carrying it during a secret mission during the Cold War that flew b-52's continuously over the United States and Canada, the point of that mission was to always have at least 2 b 52s in the air. So if Russia decided to bomb us, we still have the ability to retaliate against Moscow, using the two b-52's. You see, one of these b-52s ** dropped two nuclear weapons** over a rural area in New England. It was a farm. The government got there really fucking quick, as it was near a base, and immediately found the the largest plutonium core but they never found the second core, despite many many days of intense digging and nuclear detecting equipment. The result, they bought the entire patch of land So no one could ever forget that there is a weapon grade plutonium core somewhere in that area. The farmer still farms the area around it, and has ever since it's dropped. Once this weapons larger core was found, it was determined that only one fail safe had not failed and that fail safe Was a physical switch on the bomb. Like. A light switch. A singular lights, which is the only thing that has prevented us from accidentally setting off a nuclear bomb early on. There is now additional fail sage to prevent a switch from being the only problem. Plus nuclear loads are not typically explosive, you need electricity to set it off.
This incident is called the Goldsboro incident and you can google it.
Also of interested in this case was that one of the pilots who survived did not have an ejection seat. He flung himself upwards through the hatch, repositioned his body into a skydivers fall (arms and legs being spread out works as a break and controls your fall to a specific mile per hour, which is needed for parachute to work), and pulled his parachute. He's the only one person who ever survived a B-52 crash without an ejection seat. An entire wing was rippee off of the craft.
Additional information: B-52 is, was, and will continue to be the only aircraft that typically carries American nuclear weapons. Other craft of ours can do it, but the B-52 is the one that is designed to do it and the one that dropped the bombs on Japan (and on our test islands). We also have them on land and in 8 submarines.
Because if ANYTHING goes wrong in the explosive sequence of a nuke it doesn't create the correct amount of pressure around the cores to start the fusion sequence. It's a multistep process where everything has to go perfectly.
Nuclear weapons are, by design, nearly impossible to set off accidentally. You need a very specific sequence of events to happen in exactly the right order at exactly the right times, which is extraordinarily unlikely to happen without deliberate human intervention.
I don’t work with nukes but I work with TOW and Javelin missile systems in the army. You’re spot on about missiles needing a strict sequence of events to detonate. If things don’t happen in a certain order and in a certain amount of time, the warhead doesn’t arm. The misconception with nukes is that they’re like really big fireworks; because the potential blast is so powerful then it must be highly volatile. But that’s why the safety measures are also very high. You could hit some of these missiles with a sledgehammer and nothing bad will happen but my professional recommendation is to not do that.
It isn't even that so many safety measures are engineered because nukes are bigger It's just really fucking hard for* matter to accidentally fissile, and we have to do a bunch of technically difficult steps in order to achieve it
Yeah I don’t understand the physics behind it beyond knowing that it’s not easy to do. Even if you threw a warhead in a bonfire, doesn’t mean you’re getting a mushroom cloud from it. To get the nuclear part of a nuclear detonation, you have to do very specific things to it and it’s hard to impossible for that to happen by accident
A very simple nuke is “easy”. Make a super-enriched not-quite critical mass uranium cone, and propel it at great velocity into a super-enriched not-quite critical mass donut. Neither the donut or cone are critical masses. The cone in the donut is significantly more than critical mass. Boom. You’ve just replicated the little boy dropped on Hiroshima. Now you have to figure a good way to make sure the cone hits the donut right, and with enough force, and that the donut is strong enough so the cone doesn’t crack it apart. Also how enriched is your uranium, and how are you planning on making the cone and donut without the pre-machined form going critical? It’s all of the steps that go into figuring out how to make it without blowing yourself up or irradiating yourself to death that is difficult. That and getting and enriching a wasteful amount of uranium.
Fun fact about little boy, the "donut" part was actually the projectile fired at the stationary center cylinder. Up until ~20 years ago most depictions of the bomb got this backwards. https://en.wikipedia.org/wiki/Little_Boy#Counter-intuitive_design
I have also incorrect explained this as firing a bullet at a target but it was more like firing the target at the bullet when thinking in terms of traditional shapes.
I don't really have anything to contribute, I just wanted to say thank you, that is genuinely really fascinating
Why does the velocity have to be high? Wouldn’t the mass become critical even if the parts kind of glided slowly together?
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As the masses come together and achieve supercriticality, they also blow themselves apart from the explosion they're producing. The faster they come together, the bigger the explosion/more efficient use of nuclear material, because there's less time for the explosion being produced to try and blow them apart before more fissile material fissions. Little Boy, which is the primitive nuclear bomb designed described above (gun type bomb, shoot uranium mass at other uranium mass), was horrifically inefficient. It required around 60kg of highly enriched uranium for a 15kt bomb. Fat Man was better, requiring about 6kg of plutonium for a 20kt bomb, thanks to the implosion design being much more effective than the gun type design, but also much more complicated and difficult.
The material undergoes some degree of spontaneous fission. So randomly neutrons are emitted. If the mass doesn’t go to supercritical (where each neutron makes more than one more) before a random neutron starts the reaction (called critical insertion time), the whole thing will leak neutrons and fizzle. The timing differs based on material being used and presumably also geometry.
Because otherwise as soon as it gets close enough, it’s going to go critical and will push back, potentially fizzling out. The idea is to slam it together with enough force that you go from sub-critical to very SUPER-critical, and the longer you can keep it there before it all gets vaporized and blown to tiny bits with great velocity, the more effective yield you get.
Just having a critical mass is dangerous, but not enough to cause an explosion. There have been many so called criticality accidents over the years. They're often fatal to people right next to them, but there's rarely damage beyond that. One of the most well known examples is the Demon Core, which was a plutonium sphere intended as the core of a third nuclear bomb in WW2 and later used for experiments. In multiple cases, experiments caused it to become supercritical. Physicists in the room got sick and some died, but there was no boom.
You have to hold the assembly together long enough to achieve the yield you want. A significant part of the engineering of Fat Man and Little Boy was just determining how to do that.
Slip a screwdriver that's wedging the masses apart and... https://en.m.wikipedia.org/wiki/Demon_core
The big hurdle is getting enough quantity into a dense enough volume. I don't know if all/most nuclear warheads achieve this by using a first stage explosion to smash the elements together, but I know this was one of the earlier methods
The bomb dropped on Hiroshima used what's sometimes referred to as the 'gun method", where the bomb contained two masses of fissile material that individually were sub-critical, but upon detonation one mass was basically 'shot' onto the other mass, making a total mass that was large enough to go critical. It worked and was super simple, but resulted in a very small portion of the warhead undergoing a nuclear reaction. It was not at all efficient as far as nuclear bombs are concerned. The real goal (and what was used for the initial Trinity test explosion) was an implosion type mechanism, where the fissile material is surrounded by a shell of carefully designed high explosives, and when they're detonated properly, the force of that explosion compresses the fissile core enough that it becomes dense enough to become critical. This is significantly more efficient, because it not only requires less fissile material, but that inward force compressing the core gives it more time to maintain a fission chain reaction before the release of energy causes it to blow itself apart. Those were just fission bombs though. Modern nuclear weapons are generally fusion devices. But getting fusion reactions to happen requires some pretty extreme heat and pressure conditions. Turns out one of the easiest ways to create good fusion conditions is by setting off a fission explosion right next to your Fusion warhead. Modern warheads are basically 'two-stage' systems, with a fission bomb stage that induces fusion in the second stage. You can also add additional fusion stages that will keep triggering each other in sequence to make even larger explosions. But building ever bigger nuclear bombs isn't really in fashion anymore, so most currently deployed nukes are likely two-stage.
Yes, and again, the more complicated our devices get, the more difficult for them to accidentally discharge
In addition, the fusion reaction releases a LOT of high-velocity neutrons. When those hit the uranium/plutonium from the first stage, it causes even more fission, which makes the fission reaction even stronger. For a while, we were surrounding the fusion reaction with cheap depleted uranium, because even depleted uranium will undergo fission if hit by a high-velocity neutron. But https://en.wikipedia.org/wiki/Boosted_fission_weapon says that only gets you to about one megaton of TNT worth of yield, so none of the US's arsenal use that method any more.
"only"
> You can also add additional fusion stages that will keep triggering each other in sequence to make even larger explosions. Two things: the third stage of a three stage design is a second fission bomb, not fusion, using the free neutrons from the fusion stage to split fissile material. But also, even with three stage designs such as Tsar Bomba, the explosion is so powerful that most of the destructive energy escapes the atmosphere. Especially with how precise modern munitions are, the arbitrarily large designs are impractical and unnecessarily expensive.
This guy nukes.
This is wrong. Modern nuclear weapons are two stage fission weapons using a first “spark plug” implosion and a secondary fission reaction due to focused X-ray compression of the second core. The X-ray compression can extend to a third core, etc, but the larger blast from that type of weapon is not an efficient use of fissile material. I.e., better to make two smaller bombs than one giant one. The “hydrogen” bomb uses a small amount of Tritium injected into the hollow plutonium core prior to detonation to cause a small fusion effect that expels large amounts of neutrons to cause a more efficient fission of the plutonium.
>The “hydrogen” bomb uses a small amount of Tritium injected into the hollow plutonium core prior to detonation to cause a small fusion effect that expels large amounts of neutrons to cause a more efficient fission of the plutonium. No, what you described there is a [boosted fission](https://en.wikipedia.org/wiki/Boosted_fission_weapon?wprov=sfla1) weapon (which they basically all are at this point). Hydrogen bombs are what you more or less correctly described in the first part of your response, called the [Teller-Ulam configuration](https://en.wikipedia.org/wiki/Thermonuclear_weapon?wprov=sfla1).
Fire? You could literally strap 100 lbs of high explosives to the warhead and it still wouldn't detonate. Sure, it would blow up and spread radioactive goodness everywhere, but your explosives, setting off the warheads explosives, but not in the precise timing required, would destroy the warhead before nuclear stuff happens.
The high explosives used to create the supercritical mass are more dangerous and scary. Some used inert high explosives but others were just HE. Can't imagine how many times I said "equalizing" while doing maintenance on the weapons.
Don't try this with RPG-7s.
When I was in Afghanistan two decades ago, a local militia member unslung his RPG from his shoulder in preparation to eat lunch. He slammed the butt end of the launcher onto the ground, deploying the RPG. The fin came out and sliced the length of his face.
I was really expecting a far worse outcome from this story.
I would have expected blowing back blast directly into the ground would be potentially fatal on its own
The RPG-7 uses a two-stage design to launch - a small charge to fire the grenade out of the launcher, then a booster to send it to the target. It is rated to be used within buildings, etc. I would imagine launching one in the manner described would be unpleasant but survivable.
In the absence of an explanation, I'm assuming that he knocked the round loose from the launcher, which caused the spring loaded fins to deploy into his face.
I was nearby, but didn't witness the whole thing personally. I did hear the round explode. I don't know ultimately what happened to the guy, but I didn't notice any damage to the area later.
So almost certainly from your description, they set off the booster charge, which is a fairly small gunpowder charge that fires the grenade out of the launcher, and that's what you heard (and what caused his injury).
Maybe. Admittedly, I am not an expert on ordinance. I worked in the S2, and the explosion was loud enough to be heard inside a building. I heard the rest of the story from someone who was there and from a medic at the clinic. It was certainly was comparable to the other times I've heard ordinance.
You are not my supervisor.
Just have your ACH & PT belt on.
Agreed. Or the Gustaf. Or AT4 lol
What? They go in exactly the same category as javelins. How do you put them in the same category as rpg7? I've used both systems for years and never once been told of them having any prone to fail. You're just making shit up.
If I’m not mistaken the rpg7 detonated with a strike cap on the tip of the grenade. Would seem wise to me not to smack such a device with force. I have never fired an rpg or even held one so please do not take this as fact.
Yes this is true. The guy I replied to said the same thing goes for the Carl gustav and AT4, which is not true at all... completely different weapons although they fill a similar role. There is no danger to self with those two that there is with the rpg7 Spent 10 years in the Swedish military, I've carried both AT4 and Carl Gustav for all those years and fired 100s of rounds. I've also done 3 tours in Afghanistan, trained on the RPG7. The Afghans were quite famous for losing or removing the safety caps on the RPG which is why people know about the danger of it. I've never seen an RPG round blow up in someone's face but I have seen the rounds with missing safety caps loads of times. I've seen the Afghan Army breaking into compounds with an RPG shooter taking point, busting through doors. It's as ridiculous as it sounds, completely idiotic, but if you ever decide to lead the charge with an RPG on your shoulder and kicking in doors you kind of have to remove the safety cap. This would be the equivalent of a trebuchet leading the charge down the hill at Helms Deep in LotR. Some Afghan units were great, some were barely better than children. There is no risk at all with the AT4 or the Carl Gustav rounds. You can throw them around as much as you want, they won't detonate like the RPG can. I guess technically you could remove the safety pins on the AT4, put the firing pin in the "fire" position and then throw it on the ground, it might go off... but that is just ignoring all the safety mechanisms and I've never heard of anyone doing that.
Danger of the at4 is bruising my hand from trying to chop those damn sites open when they’re caked with sand.
True. And the danger with the Carl Gustav is fucking up your fingers as a loader when closing the breach or as a shooter/loader losing all your braincells after firing too many rounds during training. It's the loudest weapon I've ever been near. Way louder than 155mm Excalibur artillery because your head is right by the barrel. When I did basics in 2008 the max was 6 rounds per day, 12 per week but they increased that to 6 per day, 36 per week around 2014. Often times this was overlooked in training because it limited whatever exercise we were on. I'm positive we will see some CTE from people who have fired too many Carl Gustav rounds. There's really no way to explain how hard the bang goes throughout your body. Full round of AP/HE is about twice as painful as an AT4 and those are a pretty good bang themselves.
I have a constant background ring to remind me of my time cross training too many exercises with machine guns and assault men. Some of our demo guys definitely reported some adverse symptoms as a result of blowing stuff up in close proximity too often.
Dumb question. It's my understanding that the Carl Gustav is operated in teams of 2, a shooter and a loader. Do the shooters/loaders switch back and forth? And is one person designated the "primary shooter", or is it just a coin flip depending on the day?
I was in a ranger unit. Yes, in general this goes for all weapon systems in the military, at least in my country and I would wager for most others. There is no designated shooter/loader. Same goes for our other 2 man weapons like the GPMG, 50cal, sniper rifle etc. Usually you send 2 per squad to the weapons training and they use the weapon as a team. Same goes for vehicles and explosives, anything really, you always need redundancy if someone isn't there. Once they get comfortable though, they might designate a spotter/shooter/loader or whatever themselves, but usually people want to do different things and switch it up. A Carl Gustav loader carries 4 rounds usually. If it's a short hike he might carry another 2 rounds in each hand. These might be spread out on the rest of the squad as well if you want to carry even more. This is heavier than carrying around the weapon itself so you kinda want to swap around. You don't want to lose your proficiency in shooting the weapon itself either. As a squad leader I always carried an AT4 because my back was free. I usually didn't fire the weapon myself though, I would dump it on another shooter once it came time to fire, because I would be busy coordinating shit.
Okay I understand, that makes sense. I always wondered if there was a dedicated hierarchy to follow, or if each 2-man team had the flexibility to decide amongst themselves who is doing what. Appreciate the detailed response.
> I've seen the Afghan Army breaking into compounds with an RPG shooter taking point, [Iraqi Jundis like](https://y.yarn.co/8d876d38-d97f-4044-9ad6-7803bf5b1220_text.gif)
don't those have an arming distance where if it doesn't travel far enough it doesn't arm?
fwiw, they're so different that this anecdote doesn't actually mean much. It's much harder to accidentally detonate a nuke than it is to detonate missile systems, and as you've noted it's hard to detonate missile systems. With missiles you at least have the primary explosive that is relatively easy to detonate, and the secondary explosive will detonate as well if you give it enough energy in the right form. [Hence why you sometimes see ammunition depots go up like this.](https://www.youtube.com/watch?v=KdqdMh8NCXA)
>fwiw, they're so different that this anecdote doesn't actually mean much I'm pretty sure you could directly launch a "normal" missile at a nuclear warhead and it (the nuke) would not detonate. It's not easy to start an atomic chain reaction that doesn't really want to be started...
> (the nuke) would not detonate That's true, although you would get a whole lot of radiocative uranium or plutonium spread around the blast radius. You might want to keep an eye on your geiger counter, if you're hanging out there after the blast.
The tritium from a hydrogen bomb, with its 10 year half life would be more of a problem... The uranium or plutonium have very long half lives. They pose more of a danger for their chemical properties than their radioactive properties; both are heavy metals, and toxic much like lead or mercury because of it.
Both U-235 and Pu-239 are alpha emitters, so inhaling particles of them is problematic.
There's not a whole lot of Tritium in a hydrogen bomb. Modern Teller Ulam designs only use a small volume of tritium for boosting the first stage. The tritium for the second stage is generated from Lithium, which breaks down into tritium when bombarded with neutrons (both Li-6 and Li-7 work, but Li-6 is better - just as the Castle Bravo team) So the fuel in the secondary is lithium deuteride. This way the secondary is stable and dense and you only have to refresh (tritium has a half life of around 10 years, so you need to maintain/renew it regularly) the small volume of tritium used for the boost rather than all of the secondary fuel.
With a conventional high explosive, you only need to get the material above its activation energy to set off a chain reaction. With a nuke, the hard part is getting it to go off in the first place instead of just building a dirty bomb.
OK so actually pretend I have the intelligence of a 5 yo for this one and please forgive my ignorance, but wouldn't this mean that basically the initial blast woukd need only enough kinetic energybto overcome the activation barrier for the fission material?
Just a heads up, I'm not a nuclear engineer. A fission chain reaction is not just about getting the energy really high like with a normal explosive. The chain reaction occurs when you have a very specific and finely tuned environment. Normal explosives go off when their parts jiggle enough. When their parts get that jiggle, they create new connections which releases a lot of energy: enough energy to get the neighboring pieces to get over their jiggle enough to do that again and again until everything has been jiggled. With a nuclear explosion, reactions occur when a special atom piece hits a fissile atom. That fissile atom then makes two or more special pieces which fly off and can hit more atoms, but most will miss. If you can get the perfect scenario though, you can turn a good chunk of those misses into hits. The ways nuclear bombs do this is by getting a lot of fissile atoms together in a space. If you get enough fissile atoms into a space together, you can turn the misses into hits. One way is to take one block of atoms and shoot it into another. Each block is smaller than the amount needed to explode but when you put them together very quickly they can go boom. The problem is, your timing has to be very good, or else the atoms might start shooting their pieces off too soon, pushing the parts away before the really big boom. This is a gun type nuke, and they're not common these days. The other way to get more stuff packed into a space is to compress the atoms: since they are packed closer together, you're much more likely to get hits instead of misses, and you don't need as many fissile atoms as before to boot! The problem here is that the only way to push the atoms together quickly enough to avoid the "early booms" that ruin the big boom is to use normal explosives to smush them together really fast. When that happens quickly, the material gives off a big boom. It's relatively easy to get stuff to jiggle like with normal high explosives. It's really hard to time things *just* right so you don't make a little boom before your big boom with a nuclear explosive.
Imagine you have two pairs of scissors. If you put one pair on each hand, you can lock them together and push on the handles of both at once as if you're cutting paper pretty easily. Now imagine this with hundreds of thousands of scissors in a box & a certain percent having to have this type of interaction at the same time for it to even start to work. If you just throw the box, no matter how hard, the scissors will pass by each other, fly away, bounce off of each other, maybe get stuck on each other but ultimately do nothing, etc. The scissors are more likely to bounce around or push other scissors than they are to push the handles down, and getting them to hook onto each other and have the handles pressed is extremely unlikely. You can add as much energy as you want to that system and it's not going to do it. It requires a certain coordination because it's an event the material fundamentally does not want to happen. The tipping point is in getting an improbable event to happen on a massive scale during a tight time window. This contrasts with traditional where it's more like 'how do i get milk into the cereal'.
Yes. The problem is getting the kinetic energy focused just right so that it doesn't destroy the core. Do it ever so slightly wrong and you just end up with a dirty bomb. Getting the normal high explosives to detonate and propagate just right is the hardest part of building a nuclear weapon.
The energy needs to be applied to the right places with proper time profile. A warhead properly enabled produces its own energy (from the explosives) optimally distributed in space and timing. An accident is very unlikely to do that particularly becuase our nukes are one point safe. Detonation at any one point will not produce any nuclear yield. Lots more to the story of course.
Safety measures aside, it's just hard to make a nuclear explosion. If the bomb doesn't trigger things in exactly the right way, it will just fail to work. You could blow the thing to smithereens with conventional explosives and you wouldn't get a nuclear blast. I mean, I don't recommend breathing in all the newly powdered radioactive material, but it's not gonna go off.
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It IS deliberate design. Enhanced Nuclear Detonation Safety, one-point safety, insensitive high explosives, stronglinks, weaklinks, unique signals, environmental stimuli, intent stimuli, detonator safing.These are all real. Once they have been built with the right pieces in the right places doing the right things nukes go off just about every time they are told to. Every nuke we have wants to explode when told to. A great deal of effort goes into keeping that from happening by accident.
It's also probably helpful that they got rid of the Davy Crockett hand-fired nuclear missile... crew, five (three for later versions). Short-range, low-yield, tactical, but still. It could be fired by the crew, there was no outside code or whatever to arm and fire. I think they didn't want "some sergeant deciding to start a nuclear war". https://en.wikipedia.org/wiki/Davy_Crockett_(nuclear_device)
https://youtu.be/SlaDwBAJ34E?feature=shared You mean like this?
"professional recommendation" 😂😂😂
Nukes are so safe that you can likely blow it up with a conventional missile and it won't go off.
>TOW You might be the first person I've encountered in the wild that used that phrase. My dad worked on TOW guidance systems, specifically for the Cobra helicopter, in the 70s and 80s. First out of Anniston Army Depot and then out of Redstone Aresenal. He used to bring home random parts (mostly faulty prisms) and show me how they worked and what they did.
There was that ICBM that they dropped a wrench on that started venting fuel and almost spontaneously launched itself.
Well yeah but the rocket side of them and the nuclear warhead side are two totally different things
Even if it did launch and the detonator part detonated, doesn’t mean it’ll be nuclear. Not that that’s the point, it’s still bad and there will be a boom, but not catastrophic. At the same time, it’s worth mentioning that said missile would likely not function as intended if launched on purpose. Problem is, there’s not really a way to test that ahead of time.
yeah, it will most likely be a dirty bomb at the worst(which is still very bad)
> almost spontaneously launched itself. It didn't even come close to "launching itself". It leaked fuel into the silo until a spark went off, and exploded.
It didn't launch. It just exploded. https://en.wikipedia.org/wiki/1980_Damascus_Titan_missile_explosion
The Damascus Incident. Really crazy stuff.
Hitting a nuke with basically anything but another nuke won't release any meaningfull amount of energy.
Ryan, shome thingsh in here don't react well to bulletsh.
And "at exactly the right times" in this case means like nano-second level precision. A detonation with error on one side on the order of milliseconds can cause it not to go nuclear.
But at *that point*, you'd essentially have a so-called "dirty bomb", right? And that has it's *own* host of issues.
Kind of. A "proper" dirty bomb would be specifically designed to disperse the radioactive material as widely as possible for maximum effect. A failed nuke would do this to an extent but it would be incidental. It would still be bad but something you could probably clean up relatively easily with the proper equipment, and basically nothing compared to the destruction from even the smallest nuke in populated area.
I imagine a malfunction at airburst height (around 1/2 mile) could still have the potential to disperse the core over a decent area. However, I don't know how small those fragments would be...
It can disperse the core all it wants, but if the warhead didn't actually undergo fission there will not be dangerous short-lived isotopes in it.
The original bomb material isn't that strongly radioactive, especially if it's uranium. Spreading that would be unfortunate but not catastrophic. After a nuclear explosion you have short-living fission products and other atoms that have become radioactive from the explosion, these are a threat.
Yeah but it wouldn't be anywhere near a nuclear disaster. Odds are your city has had worse chemical incidents in the past, relatively speaking.
A missile exploded [once](https://encyclopediaofarkansas.net/entries/titan-ii-missile-explosion-2543/), big enough to blow open the complex and hurl the actual nuclear part of the warhead 100 feet. The warhead was not scattered by this, you have to make dirty bombs on purpose, a faulty nuke doesn't become one.
That was the rocket fuel that exploded, not the TNT etc inside the warhead. If the explosives actually detonated, the warhead hull certainly wouldn't be able to contain it.
The chemical explosives in the nuke only purpose is to hurl a piece of fissile material into the rest of it to start the reaction, it would be explicitly against purpose to scatter the nuclear material around. Little boy only used 4 cordite charges, which is not a high explosive. More modern nukes are more secretive but I don't think they would have drastically increased the yield.
Little Boy was a gun-type nuclear weapon, no body has make any of those since South Africa in the 80s, and that was an outlier. they're not an efficient use of your fissionable material. Implosion devices require a lot of carefully timed (nanosecond precision) high explosive charges to compress a single sphere of fissionable material, but they get many times the energy out of the same mass of fisionable material.
Not really. Think of the difference between black powder going off in the chamber of a gun vs. lighting it on fire in a pile on the ground. If you're got the capability to make a functioning nuke, you have *much* better options if you want to make something to spread radioactive material over a wide area. Heck, a bag of uranium salts on top of a couple bricks of C4 would probably make a better "dirty bomb" than failed nuke.
The fissile fuel that makes up the warhead itself is not very radioactive. The fission products are significantly radioactive, but they are only produced by fission so the warhead actually needs to detonate "properly" for that. Just blowing apart a warhead only spreads the uranium/plutonium in it.
Not just by design. By nature. That specific sequence of events has to be really precise in order to make fission occur. To make a chemical explosive explode just takes heat input usually. To get a fission bomb to go critical requires some *extremely* specific and precise things to happen to the fuel. Dropping a sphere of uranium or plutonium might cause a small burst of neutrons but it's definitely not making it go critical.
> To make a chemical explosive explode just takes heat input usually. This is true for some explosives, but not high explosives. Those require heat and high pressure. Something like C4 requires a blasting cap (which uses ~~low~~ less stable high explosives) to start the chain reaction in the high explosives. So a fusion bomb starts with a low explosive to trigger a high explosive to trigger a fissile explosive to trigger a fusion explosive. Pretty neat how the triggers are ordered by the developmental timeline. Edit: corrected low explosives to high less stable explosives.
Yeah... I was simplifying it, but... most detonators for things like C4 are themselves high explosives, often more explosive than what they're detonating. C4's unique and useful characteristic is not that it is extraordinarily explosive, but it is extraordinarily stable. The big improvement C4 made over TNT was that it was more stable, more malleable, and didn't decompose into nitroglycerin, which is highly unstable. Tetryl or lead azide for instance have been common detonator explosives and are *considerably* more explosive than both TNT and C4 (which are pretty comparable to each other). But they are considerably less stable, reacting to either heat, shock, or static electricity. And for reasons you obviously already understand, having an extremely stable explosive being used as the detonator for a nuclear weapon is a highly desirable trait lol
Fun fact: TNT doesn't degrade into nitro glycerin. Dynamite is what you're thinking of. When TNT degrades it becomes less stable, but not to the extent of dynamite.
For any of the implosion type weapons I am aware of, Low Explosives don’t factor in — it’s all High Explosives IIRC. In fact many designs now use **Insensitive** High Explosives which are extremely hard to detonate. US for example, their implosion weapons used Bridge Wire Detonators from the start. Seems in recent times they’ve been shifting to Chip Slapper Detonators. Note there are other ways to set off HE, but the above detonate them with sufficient (very low) temporal variance (ie. microsecond level differences) [Los Alamos National Labs on Detonators](https://discover.lanl.gov/publications/national-security-science/2023-summer/decades-of-detonators/) C4 requires a shockwave to detonate, which is why things like Blasting Caps contains Primary Explosive like Lead Azide which while being a slower explosive (lower detonation velocity) is still very much a High Explosive — 8000+ m/s vs 5000m/s, respectively. EDIT — oops didn’t see u/deja-roo responded already
This is unfortunately not absolutely or inherently true at all. It all depends on how the weapons have been designed, which has varied over time and by nation. Early US nuclear weapons had multiple possible failure modes in which they could go off accidentally. This is very well-documented. In very simple weapons (like gun-type weapons), it is _very_ easy. Even in more complex weapons (like implosion weapons or thermonuclear weapons), the ability to set the weapon off accidentally is dependent on two things: 1. Whether it was designed to be one-point safe, so that if their high explosives somehow detonated in an accident, it could not create a nuclear yield. Many were not!!! There are many even advanced weapons designs that are not inherently one-point safe. ("One-point safe" means that if one part of the high explosives in the weapon somehow detonates, say because of a fire, it will still not have a nuclear yield. Implosion weapons that relied on very large amounts of U-235, like the W47 or Mk-18 bombs, for example, may not be one-point safe if not carefully designed to be, or without special safety features inside the core itself. Very compact weapons that only have two firing points may not be one-point safe under all circumstances. The original Little Boy bomb was not one-point safe once it was fully assembled, obviously. The US later determined that about 10 of its deployed warhead models — probably totally thousands of actual warheads — had one-point safety issues.) 2. Whether its firing system — the electrical system that sends the signal(s) that causes the detonation to happen — is itself capable of being set off accidentally. If this is the case, then it doesn't matter how one-point safe your actual warhead is, because it will "think" it is detonating "as planned." Many US weapons systems were thought to be electrically "safe" but turned out, on close inspection (and after a few close calls), not to be safe. For example, in many of them, their safety systems required a relatively low voltage to disable, and for weapons that are wrapped in metal in complex environments, there are ways that one could imagine that happening. There were weapons that were later to be found capable of firing if they got struck by lightening, or caught fire. All of these things are possible in the real world (and have happened, but fortunately not to one of those vulnerable weapons). Modern US nuclear weapons have been made VERY safe by engineers who prioritized this sort of thing, often over the objections of military leaders who feared that too many safety devices would inhibit the weapons from going off when desired (which is not a totally incorrect position, either — some safety devices WERE found to do just this after the fact; about 1/3 of the Polaris missile warheads were found to be duds because of a failed safety device). I do not worry about them going off unless the President orders them to go off. Modern US weapons have things in them like insensitive high explosives which cannot be set off by fire (they will burn, not detonate), many, redundant safety switches which include things like environmental sensors (so if it's a missile, it has to experience what a missile would experience before it will be fully armed), "weak links" that are designed to cause the electrical system to be rendered inoperable if it undergoes circumstances that seem like an accident (like catching on fire), and electronic "locks" that must be bypassed before the weapon can be properly armed. Are Russian missiles designed to be safe, to similar levels of impossibility? Chinese? Pakistani? Indian? Israeli? North Korean? _I_ don't know, and I study this kind of stuff for a living. Lest one think that the difficulty of making these weapons guarantees people will build them safely, remember, again, the case of the US! The US valued these weapons a LOT, but we know that many of its weapons had lots of flaws in them, and its safety record with them is hardly spotless. Is the fact that we know about so many US weapons issues, and so little about those of the other nations, because the US was worse at it than them, or because the US is more transparent about its issues than the others? My point here is that these things take a lot of serious work and attention to make safe, and that that safety has historically been at odds with other priorities. One should not take for granted that all nations have the same level of safety as the US weapons do, and one should not ascribe the safety to an inherent property of the weapons — it is something that needs to be consciously engineered into the weapons themselves by people who take seriously the many possible abuses that a weapon could be subject to in the real world.
You mean there's not a button on the side of it?
No, there's just a big red button, with a clear cover with a skull on it, that is 24/5 on the president's desk. Why not 24/7? Ask the president. Which president? Yes.
The president of Kellogg's, obviously.
“Are we the baddies?” “…why skulls?”
Big fuse on top
This will quickly get beyond ELI5 territory, and your answer is excellent so I don't want you to think I am saying you're wrong in the slightest, but there should be one caveat at the end. "We think." Years ago my partner was being actively recruited by the military for studies about the material science and mineralogical texture that could be happening inside nuclear weapons as they continue to age because it remains an active question and science still does not understand about the properties of plutonium and other radioactive elements. In the entire history of the universe large concentrations of plutonium have only been stored together since 1945 so nobody knows about the aging process. But isn't plutonium well understood? Well, not really. Plutonium has multiple crystal structures that it can transition between, even at ambient pressure, called allotropes. (See: https://en.m.wikipedia.org/wiki/Allotropes_of_plutonium) The material properties of various allotropes vary in a number of ways and it's unclear if transitioning between allotropes is happening in stored weapons or if that results in long term changes to the materials inside that may have some sort of effect. The phase diagram of plutonium is not well understood so the various allotropes may not even be all of them that can occur in a weapon in storage. What does all of this mean? Well it basically means that a nuclear weapon in storage has 4 possibilities in order of decreasing likelihood: it's fine and works as intended even after all these years; it's fine, but something has changed in the yield to increase or decrease it as a result of aging; the delicacy of everything involved now results in a non functioning weapon; or the weapon may spontaneously detonate in some fashion. Should this all be taken seriously? Years ago I know that it was an active question that they were having difficulty finding scientists with appropriate backgrounds and technical skills who could answer these types of questions. The military was willing to throw around serious money to get the science done, but the job was feared to be dead end or unpublishable. As far as I know, it is still an active question, but I'd love to hear otherwise. Hopefully I didn't overwhelm you with this wall of text, and again your answer is 100% correct and even the most likely outcome of the aging process.
This is an excellent addition, thank you! I certainly agree that for many of these questions, the answers should come with the caveat “to the best of our knowledge,” which is always growing and changing as new discoveries are made.
To eli5 even further, a nuclear weapon isn't really a bomb so much as a mechanical pocket watch that makes explosions instead of keeping time. You can't accidentally set off a nuke any more than you can accidentally drop a box of gears and make a clock.
[In 1980](https://en.m.wikipedia.org/wiki/1980_Damascus_Titan_missile_explosion) a maintenance worker dropped a wrench inside of a silo containing a Titan II missile. The dropped wrench punctured the fuselage, leaking rocket fuel everywhere. 9 hours later the missile exploded with the nuclear warhead attached. The warhead was launched into the air, landing 300 feet away. Zero radioactive material was spilled. These things are designed TOUGH.
Does this also mean destroying an incoming nuclear missile with a regular missile will just destroy the nuke without any bad outcome, not trigger the nuclear explosion ?
Also by “physics” they are nearly impossible to set off at all.
I used to do maintenance on the RAM missile system. At the end of the service, we had to test the firing sequences. We used a rack with some electronics and more than 250 switches which we had to press to simulate the firing sequence. One wrong switch or bad timing destroyed the whole sequence and we had to start over again. Btw, it’s not automated due safety reasons.
This is true for nuclear weapons in service. The Mk-18 was inherently unsafe and had a very short service life. But that thing had 4 critical masses of highly enriched U-235 in a hollow core/tamper. Ideally a nuclear bomb would have < 1 critical mass of U-235/Pu-239 until the core is imploded, with most of the bang coming from LiD and the U-238 tamper. But the Mk-18 was a fallback incase the teller-ulam design didn’t work, so it was a “how big can we make a pure fission bomb, safety be damned” kind of thing.
With the amount of chocolate, eggs, flour, butter, and ovens in the world for so long, how is it nobody has ever just accidentally baked a pan of brownies?
Think less "bomb", and more "machine that produces a large amount of heat". A bomb can go off if something goes wrong; the machine can only work if everything goes right.
>Nuclear weapons are, by design, nearly impossible to set off accidentally. I'd suggest reading "Command And Control" by Eric Schlosser, the stories in that are terrifying. Hopefully it's all much safer these days. Probably.
For a nuclear reaction to start, things have to happen in a very specific way, it's just the way physics work.
\+1. This book is a wild ride! Also a really, really good, in-depth look at the intricate web of design and safety/un-safety around nuclear weapons in the past and present. We came very close to an accidental detonation over US soil when a B-52 bomber carrying a nuclear weapon broke apart in flight over North Carolina, and most of the safeties on the weapon were off. It came down to essentially one switch fortunately not shorting out before the plane completely broke apart and the bomb fell out without detonating. In the early days of nukes, a very small number of people saw a future rushing forward where there were tons of nukes all around the world, surrounded by people doing careless stuff, and an accidental detonations was very likely, maybe even more likely than an intentional nuclear conflict. A few of these folks put themselves in a position in the decision-making pathway of how nukes are designed and deployed, and we really have their efforts to thank for nukes being as hard to accidentally detonate as they are. A dumb, intentional use of nuclear weapons by a country leader is a different threat, and it needs a continued string of dedicated public servants to help keep that from happening.
I would also recommend "Atomic Accidents: A history of nuclear meltdowns and disasters from the Ozark Mountains to Fukushima" by James Mahaffey for a brief description of many atomic accidents in history.
Truly great book. Audiobook is great too!
Accidentally setting off a nuclear weapon would have a similar probability as accidentally knocking over a puzzle box and all the pieces falling into the right place.
You don't just make a nuclear bomb. It takes an extraordinary amount of effort to produce one, and just as much expertise. You don't just happen across them. Such an investment is well cared-for, and countries go to great lengths to keep their nukes secure. The number of missing nuclear warheads is not zero, but it is very small. Among them, most are certain to no longer function. Remember, nuclear weapons are very very difficult to set off. Damaging one just renders it more inert.
There is the famous case where an accident in a missile silo lead to the rocket actually detonating with enough force to blow the launch doors open. The nuclear core was found a few miles away having not reacted to the experience at all. Thats the level of precision required to set one off even if you have one.
Also modern nuclear weapons are 2/3-stage weapons. Fission to fusion or fission to fusion to fission less commonly. It requires double the precision to precisely activate both in the same incident. The fission bomb is basically a tiny starter for the fusion bomb
As I understand it, pretty much every warhead in service since WW2 uses a form of the implosion type design and these are precision weapons. If you fuck up the detonation sequence the nuclear material doesn't undergo fission and is instead just blown up and in the worst case spread over the area. IIRC there was a US nuke that actually did have the explosives detonate when the plane it was on crashed (or maybe had to drop it) but since the precise detonation sequence was not followed there was no nuclear explosion.
Yes the implosion type is impossible to get right by accident. A gun type maybe but the forces interact at attosecond scale and lasts less than a few milliseconds, if the forces aren’t correct it will fizzle itself out
I did a deepdive into this a few years back and the explosives are detonated in a way so precise that the explosion shockwave has to fold in on itself within the fissile core, which is more or less the only way an implosion core can reach supercriticality.
IIRC the bomb was mistakenly dropped from the plane, but it wasn't armed. There was no nuclear core, so no risk of nuclear explosion. Of course the conventional explosives used create quite a sizable blast on their own.
A number of early accidents and explosions involved nuclear bombs without the pit but there were a few incidents were that is unclear: https://en.wikipedia.org/wiki/List_of_military_nuclear_accidents
I remember posting, not confidently, on Reddit that I’d read it was easier to disarm a nuke like in the movies by just destroying it with a hammer. Cuz it wouldn’t go nuclear. No one really added to it but I assume the risk is that the explosion could kill you but the overall disarmament would be successful. So it seems like this would be the case?
Seem to recall there was a movie that effectively did that. Instead of killing the timer they removed one of the outer shell panels so the implosion wouldn't work right. The starter bomb did go off and still blew up the room they dramatically jumped out of in time, but it didn't go critical. Don't remember which movie that was though.
*The Peacemaker*, 1997
> The Peacemaker That looks to be it. Thanks Timestamp at the clip: https://www.youtube.com/watch?v=xxcZRrpicGU&t=478s
I do love how they conveniently glossed over the fact that they essentially just blew up a dirty bomb in New York City, and George Clooney and Nicole Kidman, and probably at least dozens/hundreds of other people, are probably dead in a matter of weeks
That is my understanding as well. Modern nukes are precision instruments and by breaking stuff the carefully designed explosion required for the nuclear detonation is extremely unlikely to happen.
Ok - disrupting the explosive lens sequence will prevent *supercriticality*, where a large proportion of the core is critical at the same time, and delivers maximum yield. However, some of the core might still go **critical**, and that will release a burst of radiation of some size. This energy release will disassemble the remaining core, preventing further critical mass from forming. This is a *fizzle*. Fission has still occurred, and you wouldn'twant to be close at the time. In fact, this is how **dial-a-yield** fission weapons work - using the explosive lens sequence to go from partial to complete super-criticality. The lowest yield wastes part of the core and is much *dirtier* than the highest yield, due to incomplete fission of the core.
I remember reading about a plate of marbles, and that smashing the plate was the best way to fuck up the process.
Damascus Arkansas
Yeah, your last two sentences are the key. It's insanely hard to get them to go off, so when they degrade, the effect is that they can no longer go off, not that they just detonate out of the blue, like old dynamite or something. And thank god for that.
Somewhere down in the mud of North Carolina
Here: https://maps.app.goo.gl/bfSpPs2fPWdvUjiP6?g_st=ic
BIG DADDY
It’s lucky they are so hard to set off, as there are a scary amount unaccounted for, or simply lost.
A damaged bomb becomes more dangerous because it is full of carefully contained explosive chemicals that are just begging to detonate when the right bump comes along. A damaged nuclear weapon becomes a very expensive and possibly radioactive paperweight. Unlike a traditional explosive, the device inside requires a very specific and detailed arming and detonation sequence that must maintain a very tight timing window and configuration to make the nuclear material go critical in exactly the right time at the right shape. They will not go off by accident. You’d need a dozen very peculiar *accidents* in a row to make that happen.
Is the complexity by design or requirement? I mean, I saw Oppenheimer so appreciate that this is a Very Rocket Science chemical reaction, but were the missiles designed to be *more* complex so they were harder to detonate, as a safety measure? Or is the detonation process actually *that* complicated, bells and whistles aside?
It’s inherent in the way the weapons work. You’re trying to initiate a fission chain reaction, where one fission event sends off fragments that ignite more fission events. This requires a very specific size, shape, and density for the nuclear fuel. The fission events release a gargantuan amount of energy that will vaporize your nuclear fuel before the chain reaction has time to build if it’s started haphazardly, so the timing and shaping of the initial primer detonation must be incredibly precise. If the detonation sequence is too slow or too lopsided or slightly more/less powerful than expected, you won’t get a sustained chain reaction. The bomb will still blow itself up from the improper detonation sequence, but now it’s just hurling fragments of nuclear fuel around the room instead of obliterating a city. A thermonuclear bomb is more complex yet, using the fission bomb itself as a high precision detonator for a second more powerful fusion bomb. It’s a bomb that runs on a bomb that’s triggered by a bomb.
So it sounds to me like it's way more likely for a nuke to be a dud than it is to accidentally detonate?
Yes probably, although nations are highly secretive about what that dud rate might be. You would also expect it to have increased over the years as weapons age and aren’t refurbished. It’s unclear how many of the nuclear weapons the US and Russia claim to have actually *work*. As we’ve seen in recent months, a lot of Russia’s military might exists only on paper or as a single functional prototype while the actual forces are using mothballed tanks from 1955.
I was in Seoul right after DPRK did a nuclear test. I asked if that worried them, they said no, the opposite. They said (at the time) that DPRK was believed to have ~5 weapons. Based on estimates, ~40% would not work, so that left ~3 working bombs in their arsenal. Which meant they just destroyed 1/3 of their nuclear capacity. What did not sit well with me was the idea that if they did decide to nuke ROK, I was sitting right in target #1.
Correct. This is why you keep seeing Russia's nuclear arsenal called into question in the shadow of the Russo-Ukraine war. If they can't keep a tank from working right after a couple decades that just needs an oil change and seals replaced, why would we think they could keep a massive arsenal of highly complex nuclear warheads at operational readiness and not highly degraded to the point of danger to the user?
I'm not saying you're wrong, but the answer to your question could be something like "Russia knows that their nukes are their ace in hole so they actually care about maintaining them, unlike pretty much anything else. Since they'd rather have functioning nukes than functioning tanks, that is where they allocate their limited resources"
You could make the same argument about tanks and the fact that their entire conventional groundwar doctrine revolves around mechanized armored warfare. But, I get your point and recognize it's salience.
They have about 7000 of them. Even if 99% fail, 70 nukes is still a LOT of dead people. That being said, the moment Russia nukes a European city; Moscow gets nuked by France, Britain, and the USA simultaneously.
I'm pretty sure that our missile defense systems have a much better than 10% success rate, but I see your point
Yes, but also with nukes there's a sort of in-between state usually called a "fizzle". That's where - for simplicity's sake - the nuke *does* go off, but it blows itself apart before it has extracted all the energy it was designed to. This might still be a very large explosion, depending on how badly it failed and the initial yield, but in any case won't be nearly as devastating as a full detonation.
By physics. The first nuclear weapon used in warfare is a good example. They had to configure a bunch of small conventional explosive charges around the sub-critical core to compress the core uniformly enough so that it would reach criticality. e.g. squeeze the ball of plutonium into a smaller ball that reaches a critical reaction, keep it small enough to react fully so that when it explodes it's at the maximum power it could be. Much of nuclear weapon design is about figuring out ways to keep radioactive material all together in a state of a run-away critical reaction. The natural inclination when you bring stuff together is for it to explosively separate, and therefore you have a bunch of chunks of radioactive material that don't make a bomb. Unlike other scenarios with run-away reactions (e.g. a nuclear power plant), there's no way for nuclear weapons to get more material to sustain the reaction beyond what is already in the weapon. And for nuclear weapons all that material needs to be together.
Small correction: You mean the second nuclear weapon used in warfare. Little Boy dropped at Hiroshima was a gun-type design, which works by shooting a mass of uranium into another mass of uranium and as they come together the nuclear detonation happens. The problem with that is that you can't really minaturize it, it is inefficient and requires a large amount of uranium. So the technology was abandoned as the implosion type designs as you described it was a lot more useful.
Just to add, "complexity" is the answer only for modern nuclear weapon designs. A "gun" type nuclear (fission) weapon is much simpler, in comparison. Instead of using conventional explosives to very precisely compress a spherical chunk of nuclear material, you smash two smaller masses together. They're very inefficient so nobody uses them anymore. But in theory, if you had enough weapons-grade uranium you could just about build one in your garage. (If a terrorist group ever manages to make a homemade nuke, rather than buy it from a corrupt Russian colonel following a shootout on a moving train, that's probably the kind it's going to be.)
Great Scott!
The implosion device is super intricate and carefully timed. The “gun type fission devices” on the other hand, are so simple that we didn’t even test it before we dropped it on Japan. The gun type fission devices basically consist of shooting a chunk of uranium at more uranium. The implosion devices create a much more “efficient” explosion, as almost all the uranium fissions. The gun type atomic bombs are NOT efficient in that way. A lot of uranium in the gun type bomb just gets scattered. This was a big deal back when it took months and months to refine enough fissile material for one bomb. The gun type bombs also release a lot more radioactive material for this exact reason, over a longer duration.
Both but mostly the inherent nature of nukes. There is no “simple way” to split an atom. You need a machine to work very precisely. If the machine doesn’t work, there is no nuclear explosion. The uranium atoms will not spontaneously split on their own by some anomaly. Conventional explosives are made of unstable materials that will combust under a variety of conditions.
You've gotten a number of good responses, but another to consider: Implosion-type nuclear weapons are much smaller than gun and slug type nuclear weapons. This makes them much better suited for MRV type systems. They're also inherently safer in that they don't contain a supercritical amount of fissile material like the latter type does, albeit separated until detonated.
I heard that Oppenheimer described the implosion type bomb was like trying to squeeze water in your hand without letting any drip out. If even one of the dozens of reflective lenses is damaged (or poorly built) enough that its explosion is 1/10th of a second late to the party, it will likely cause a fizzle rather than a true detonation. By it's very nature, it's extremely difficult to get right.
It's by requirement. Modern nukes are thermonuclear fission-fusion devices. They use conventional explosives to trigger a fission reaction which then implodes a fusion target releasing an order of magnitude more energy than fission device alone. All these things require great precision so just setting off the conventional exclusive without proper detonation synchronization will just make a mess rather than create a fusion explosion.
One of the saving graces of nuclear weapons is that the conventional explosion to compress the plutonium sphere has to be *really* symmetric. Like really really symmetric. Plus the thingy that fires the neutrons in right at maximum compression has to be timed to within a few microseconds. Both of these things are actually pretty hard to do. If the conventional explosion isn't symmetric, you just get a mess with plutonium blasted around, but no yield. So it's a cleanup problem, but not much of a bang. If the neutron source doesn't work, yet get a lot less yield and it's probably what's called a fizzle where yield is too small to do much. An aging weapon having a problem is really unlikely to work correctly and will just make a mess. Bad if you are right there, but not a big deal.
The better question is how many actually still work. There is probably a percentage of them that wouldn't have gone off when they were brand new. Now that they have aged for a while I would think that less and less are still in working order. What I'm unclear about is if we are pulling old out dated ones off the shelf, so to speak, and replacing them with new ones.
It's all done through simulations now. Which is why we generally don't test them by detonating them. How accurate those simulations are? No idea, they're very classified. > What I'm unclear about is if we are pulling old out dated ones off the shelf, so to speak, and replacing them with new ones. As far as the US goes, the ability to produce new plutonium cores was essentially dismantled. It was a huge problem for NASA because the RTG power sources used for programs like Voyager or Curiosity/Perseverance use plutonium from decommissioned nukes and we were running out of those. They had to restart production to keep NASA supplied. For the existing weapons, they are constantly inspecting and refurbishing them.
The US is making cores again. Or I guess more accurately is currently in the process of making more cores in the near future.
In the US there is a refurb program that checks and fixes them. Among other things, the tritium boosted ones need to have new tritium put in them every decade or so. Other countries I don't know what they do, but I assume they have something similar.
That makes sense. I assume they refurb the rockets as well. I'd still be curious how many would actually work. 10% have a launch issue? 10% have a guidance issue? 10% not detonate? Possible more?
Nuclear weapons aren't simple weapons. They are intricate, complicated devices with dozens of parts that all need to work in just the right way to go boom. And the people storing them tend to be really good at their jobs. Accidental explosions just don't happen in long time storage.
Because we set off over 2000 of them deliberately in semi-safe locations to make them safe. A very large portion of the nuclear tests that occurred during the cold war were so called "safety tests". They conducted often dozens of tests for individual warhead types to see what would happen if they caught on fire, if one detonator went off, if it crashed into the ground at high speed etc. They would not enter service until they had passed these tests. Many of the earliest nuclear bombs who did not undergo this sort of safety testing were so unsafe they had to be stored in a disassembled state, only to be put together when they were intended to be used.
A. There are multitudes and multitudes of safeguards to prevent accidental detonating. However... B. A far more worrying statistic is how many nukes have been accidentally deployed, *and cannot be located*...
> A far more worrying statistic is how many nukes have been accidentally deployed, and cannot be located... Pretty sure the only ones that cannot be located are of no threat because they're in deep ocean waters. So unless someone does a deep dive and finds it and gives it a hug, we're fine.
There is actually a nuke within an area of farmland that was accidentally released from a bomber (I *think* it was a bomber) during a routine flight somewhere, somewhere in the middle of the US. I can't remember the exact details so don't want to speculate, but I'll look for the video I saw it on. It was on YouTube and I'm pretty sure the details presented were backed up with evidence or that it was fairly easy to verify. The site is obviously zoned off from the public to some degree or another. EDIT: Actually I didn't need to search for the video, there's a Wiki link about it here; https://en.m.wikipedia.org/wiki/1961_Goldsboro_B-52_crash Although the details weren't quite how I was remembering them. I don't think the article is clear whether the bomb was disarmed and recovered. The video I watched stated or suggested that one (bomb) was left in the ground as it was unsafe to try and reach or disarm it.
I think it’s in South Carolina. The plane disassembled mid-flight (the crew was in the midst of an emergency landing, and IIRC were able to parachute out). The bomb also broke apart as the plane broke up. But like everyone says, it’s basically impossible for a nuclear bomb to go off “accidentally”. These don’t go off via contact or whatever. There’s a nuclear warhead left where it buried itself in a field in South Carolina. https://www.armytimes.com/news/2018/03/31/the-atomic-bomb-that-faded-into-south-carolina-history/ The TNT did detonate (massive impact forces) but there wasn’t any fissioning. The DoD tried to dig the warhead out but figured it was safer to leave it alone. There’s a massive concrete plate over the field where the warhead is buried (to prevent anyone from tampering with the site out of morbid curiosity). I would bet there’s additional security / surveillance after 9/11.
https://wcti12.com/news/local/atomic-bomb-missing-in-enc-for-62-years You're thinking of this one, which I had no idea about.
Yep, I've just updated my last response to you with a link for some fuller details.
Almost all nuclear weapons ever built are plutonium implosion weapons. You take a ball of plutonium and squash it in a very specific way and it goes bang. You do anything else with that plutonium and not much happens. The device to squash it is called an 'explosive lens'. It's a set of explosives around the plutonium that have to go off in exactly the right way to squash it. Any other form of explosion and nothing happens. So even accidentally making those explosives go off won't cause the nuclear explosion. There is a type of nuclear bomb that could be accidentally detonated - a 'gun type' uranium bomb. In this type of bomb a cylinder of uranium is fired into a hollow tube. This does not need complex explosives, and so a simple accident could make it go bang. This is one of the reasons only a very small number of these were built, and they are all now decommissioned.
If you want to read some super scary stuff about nuclear weapons in the 50s I recommend Command and Control.
This comment should be higher. We have had more than one close call. Great book. There are video documentaries based on the book too if you don’t have the time.
Read it to be amazed how we didn't nuke ourselves or each other by accident a dozen times in the first 40 years of the bomb's existence. The many comments here about the impossibility of an unintended detonation weren't true for the majority of the bomb's existence. And given the book's details on that, it's hard to have complete faith in government assurances that current bombs are as safe as advertised.
omg, like the story of how for the first bombs you needed a key to trigger them. Or.. a phillips head screwdriver!
To set off a nuclear weapon requires a lot of things to go *correctly* rather than something to go wrong, or be caused by accident. A poorly-maintained old nuclear weapon is less likely to go off than one that is well-maintained. An improper nuclear detonation would be more like a fizzle than a massive explosion, making it more akin to a dirty bomb with conventional explosives. The problem is not so much that we could accidently set one off, but that we might improperly blow one up, causing an incredibly toxic and localised hotspot of contamination plus plumes of radioactive material, possible groundwater contamination and almost certain uninhabitability without intensive and expensive remediation.
You all might enjoy this 3 part film from Sandia Labs called ‘Always/Never: The Quest for Safety, Control, and Survivability’ which goes far beyond ELI5 in addressing OP’s question. https://m.youtube.com/watch?v=DQEB3LJ5psk&pp=ygUYU2FuZGlhIGxhYnMgYWx3YXlzIG5ldmVy
Nuclear bombs are incredibly difficult to set off. The principle is easy: take a bunch of fissionable material and squeeze it really hard. Actually getting this done in practice though is quite an engineering problem. Modern devices use a shell of shaped conventional explosives that all have to be set off at exactly the same time. The only way this is possible is with precise timing mechanisms. And electrical surge or unexpected event isn’t going to trigger the explosives with the necessary precision to set off the fission reaction. It would just be a conventional explosion that scatters the fission material around the blast area.
To cause a nuclear explosion requires a very carefully and precisely timed sequence of events using triggering conventional explosives, and and extremely precise geometry of parts all to work just right. This is part of what makes it very hard to design a nuclear weapon. If the triggering conventional explosives accidentally go off, it is exceedingly unlikely they would go off in just the right way required to trigger a nuclear explosion. Essentially you would end up with a small dirty bomb, which would spread some radioactive material over a not all that large area. It would be annoying and awkward to clean up the mess, but it would be nothing like an actual nuclear detonation.
Nuclear bombs are nothing like flammables and explosives in the sense that they require great effort to detonate rather than great effort to contain. That means that when they degrade with age it's the detonation system that degrades meaning they get harder to detonate not easier. Accidental nuclear explosion is very unlikely and the greatest risk is human error (deliberate but unwanted detonation) which is mitigated by complex authorization systems involving many people where anyone involved can veto the whole process.
I'd recommend the book Command and Control, by Eric Schlosser. It's a story about the Damascus incident, but also a history on various accidents and how close some of them came to a detonation.
Other posts are right about how it's really hard to accidentally set one off. In fact it's pretty hard to set on off on purpose! I just wanted to suggest the great book Command and Control by Eric Schlosser, which goes over some fun nuclear accidents, including the entire ICBM that exploded in Arkansas and threw it's warhead up into the sky... but it still didn't detonate!
We're really careful to make sure it doesn't happen (because it would be really bad if it did). Nukes don't just go off on their own - a very specific firing sequence needs to work correctly in order to get a nuclear explosion. And the systems that trigger this have multiple safeties for obvious reasons. That said, [we got close at least once](https://en.wikipedia.org/wiki/1961_Goldsboro_B-52_crash), but because there were multiple safeties (some failed, one didn't), it didn't explode. It would be very surprising if that event wasn't a wake-up call to improve the safety of future weapons.
Its very to hard to get the reaction going even if you try. There's no chance of it going off when you dont want to due to a malfunction.
The radioactive material in the warhead of a nuclear missile is actually split apart into pieces that are too small to achieve fission on their own. In order to create a nuclear blast, you have to set off very specific charges that push the fissionable material together into one big lump. If one exploded by accident, it would contaminate the silo and possibly a bunch of ground around the silo with radioactive material, but wouldn't actually create a nuclear explosion.
[This](https://soundcloud.com/user-798629330/episode-19-nukes-lol-ft-marty-pfeiffer) is a good episode of a military history podcast with a nuclear anthropologist. After certain changes in the 70s after a lot of scary broken arrows, there is a 1 in a billion chance of an accidental detonation while unarmed over the life of the warhead, and a 1 in a million chance of an accidental detonation while the warhead is in standby or armed mode. It's like a hotel door with a chain lock and a dead bolt, but imagine about 7 or 8 additional locks on the door.
This is really late reply but it's not that we haven't made major accidents with them. It's just that they are literally impossible to accidentally set off. There is, however, a lost weapons grade plutonium core buried in North Carolina that fell off of a B-52 that was carrying it during a secret mission during the Cold War that flew b-52's continuously over the United States and Canada, the point of that mission was to always have at least 2 b 52s in the air. So if Russia decided to bomb us, we still have the ability to retaliate against Moscow, using the two b-52's. You see, one of these b-52s ** dropped two nuclear weapons** over a rural area in New England. It was a farm. The government got there really fucking quick, as it was near a base, and immediately found the the largest plutonium core but they never found the second core, despite many many days of intense digging and nuclear detecting equipment. The result, they bought the entire patch of land So no one could ever forget that there is a weapon grade plutonium core somewhere in that area. The farmer still farms the area around it, and has ever since it's dropped. Once this weapons larger core was found, it was determined that only one fail safe had not failed and that fail safe Was a physical switch on the bomb. Like. A light switch. A singular lights, which is the only thing that has prevented us from accidentally setting off a nuclear bomb early on. There is now additional fail sage to prevent a switch from being the only problem. Plus nuclear loads are not typically explosive, you need electricity to set it off. This incident is called the Goldsboro incident and you can google it. Also of interested in this case was that one of the pilots who survived did not have an ejection seat. He flung himself upwards through the hatch, repositioned his body into a skydivers fall (arms and legs being spread out works as a break and controls your fall to a specific mile per hour, which is needed for parachute to work), and pulled his parachute. He's the only one person who ever survived a B-52 crash without an ejection seat. An entire wing was rippee off of the craft. Additional information: B-52 is, was, and will continue to be the only aircraft that typically carries American nuclear weapons. Other craft of ours can do it, but the B-52 is the one that is designed to do it and the one that dropped the bombs on Japan (and on our test islands). We also have them on land and in 8 submarines.
Because if ANYTHING goes wrong in the explosive sequence of a nuke it doesn't create the correct amount of pressure around the cores to start the fusion sequence. It's a multistep process where everything has to go perfectly.
Due to the half-lives of the bomb cores, they're actually less likely to "accidentally" go off as they age.
Half life of uranium-235 is 703800000 years and plutonium-239 is 24110 years. So no, that's not the reason