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Ask HN: What happens if a nuclear missile is air-destroyed before detonation?

So, Party A launches the nuclear missile at Party B, and Party B uses its now-apparently-at-least-occasionally-working missile defense systems to take out/destroy the missile/bomb before it can be detonated. What happens? I am thinking about how the US detonated its Hiroshima nuke about 45 seconds after dropping it from the plane, and how it was detonated, as designed I believe, about 1/3 mile above Hiroshima.

AgentK20 4y ago
Keep in mind that in order for a nuclear explosion to occur, a very precisely timed series of explosions must occur within the device to trigger fission (and then potentially fusion, depending on the type of device). If the inbound missile is kinetically damaged or destroyed before it gets the chance to trigger, then the conventional explosives will likely detonate within the missile in a way that does not reach criticality, resulting in a conventional explosion with a small amount of fallout from the nuclear core that wasn't triggered being dispersed.
- verdverm 4y ago
  https://www.youtube.com/watch?v=zVhQOhxb1Mc https://www.youtube.com/watch?v=zVhQOhxb1Mc has a good explanation of how nuclear weapons work. It may be possible that a missel is disabled and when it hits the ground, produces a much lower yield explosion than designed for, in particular a plutonium device, if I recall the video and extrapolate with sufficient accuracy
  - adastra22 4y ago
    It is basically impossible for a plutonium bomb to generate anything resembling what you think of as a nuclear explosion unless it is deliberately triggered and experiences ideal ignition conditions. If it were to crash into the ground, be blown up by an intercepting missile, or otherwise malfunction, you'll just get a normal-bomb-sized regular conventional explosion and a bunch of toxic and only mildly radioactive plutonium strewn all over the place.
    - zinekeller 4y ago
      Just adding about the so-called "dirty bombs" (https://en.wikipedia.org/wiki/Dirty_bomb https://en.wikipedia.org/wiki/Dirty_bomb). It's not dirty because it's lethal but rather because the construction of these bombs are rather crude, which allows nearly everyone with some knowledge of bomb building to construct them. In some sense, this is more dangerous than a proper fission-type nuclear bomb.
      - deleted 4y ago
        [deleted]
      - yakshaving_jgt 4y ago
        The explanation you gave for why a dirty bomb is called as such doesn't seem to be supported by the link you provided. Rather, it's dirty because it contaminates the area around the explosion with radioactive material.
      - xadhominemx 4y ago
        That is not correct
      - tsimionescu 4y ago
        The vast majority of effects of a dirty bomb are foiled by such advanced technologies as windows and showers. The initial conventional explosion will kill and injure far more people than the radioactive dust. At worst, that dust will slightly increase cancer rates for people relatively close to the location of the bomb (say, upto a few hundred meters) over their lifetime.
        mLuby 4y ago
        Dirty bombs are weapons of terror, not weapons of mass destruction. The true damage is caused by societal and economic overreaction from the target: fear leads to expensive security theatre, a desire for vengeance leads to lashing out with expensive unnecessary wars, uncertainty and political instability destabilizes financial markets, etc. Some diseases are similar: immune system overreaction causes more harm than the actual invader.
- mabbo 4y ago
  This is, imho, the correct answer. But setting aside the nuclear device, the rocket itself wouldn't survive any damage either. Rockets aren't built to be robust because that adds mass, which requires more fuel and reduces acceleration. Better to just go faster, avoid the danger. But that means any damage to the rocket is probably going to doom it.
  - perihelions 4y ago
    There's no rocket left after the boost phase. Everything separates off but the warhead and its encapsulating reentry vehicle -- a compact, tough shell designed to protect it from the stresses of reentry. So it's probably far from fragile. Here's what those look like: https://en.wikipedia.org/wiki/Multiple_independently_targetable_reentry_vehicle#/media/File:W87_MIRV.jpg https://en.wikipedia.org/wiki/Multiple_independently_targeta...
- denton-scratch 4y ago
  > then the conventional explosives will likely detonate within the missile in a way that does not reach criticality Why? The primary in a thermonuclear bomb needs careful timing of the conventional charge. But don't they go to a lot of trouble to ensure that conventional charge dowsn't go off except under the correct control? The detonators are timed and triggered electronically. The charges are not like nitrogycerin, they won't go off on impact. I don't see why damaging the delivery vehicle should affect the bomb, unless the vehicle explodes catastrophically, destroying the bomb. And unless, I suppose, there's a failsafe installed, so that a malfunctioning vehicle automatically disables the bomb. That would make sense to me; I don't want my ICBM exploding over some place that wasn't on the target-list. Basically, I want a warhead that goes off correctly over the target, or not at all. That appears to be a fairly straightforward engineering challenge; as they say, it's not rocket science.
  - ilyt 4y ago
    > The charges are not like nitrogycerin, they won't go off on impact. They will most likely go off if the warhead gets exploded tho. I doubt they test how the nuclear bombs react to getting shredded by AA
    - JoeAltmaier 4y ago
      Not bloody likely. Its a very delicate balance of geometry and timing. Hit it with a hammer (blow it up) and that's all destroyed. You'd get the same effect as blowing up a pile of parts not yet formed into the missile. That is, some radioactive material vaporized and spread around.
      - ilyt 4y ago
        I meant that the charges will blow off from explosion, not that they will blow off in exact way needed for nuclear bomb to happen
        JoeAltmaier 4y ago
        Ah. More likely.
- kidme5 4y ago
  The nuke could be programmed/signaled to actually detonate if it encounters an interceptor AND is within X distance of target territory. In which case, it is an atmospheric nuclear explosion probably with EMP effects. This is one reason people stress missile defense that hits the nuke immediately over their launch site (boost phase). For NK that might mean interceptor UAVs hovering off the Korean coast or ships. But for Russia or China it means a Starlink-style system with hypersonic interceptors staged in orbit around the globe. https://wikipedia.org/wiki/Space_Development_Agency https://wikipedia.org/wiki/Space_Development_Agency This obviously has tons of flaws though. It would cause a feedback increase in nuclear stockpiling to counteract the fraction intercepted to ensure MAD.
  - mikewarot 4y ago
    >if it encounters an interceptor How would it know? You can't have radar on it, because that would make it easier to hone in on, aiding interception. Also, on re-entry most objects have a highly ionized shock-wave around them, making forward facing radio communications quite difficult at best (assuming you could manage the cooling, etc)
    - kidme5 4y ago
      They (launcher of nuke) can use satellites to track their own missile and the interceptor. Also separately, communication/radar works fine through reentry plasma once you go up to 20-50 GHz frequency.
      - aPoCoMiLogin 4y ago
        that sounds like it still adds way to spot the nuke and intercept it.
      - positr0n 4y ago
        My intuition says, due to the speeds and sizes of the two vehicles and latency of communications there'd be no way to figure out if the interceptor will successfully hit the nuke until it's too late. If the interceptor misses the nuke's location by 50 microseconds it'll explode harmlessly a foot behind it. (The ICBM is probably traveling faster than the shockwave front of the explosive, depending on where it is) I don't think a radar from satellite could be that precise, that fast, and get a signal out.
- mikewarot 4y ago
  Shaped charges are used to penetrate Russian tank hulls in Ukraine, and work by using explosives shaped in a very specific way to invert a copper cone and turn it into a hypersonic jet of hot goo. A nuclear device is an spherical array of them, all focused inward. If any of them goes first, it pushes things out of the way, and you get a "fizzle" You also have to shower things with a neutron pulse at just the right time to kick off the chain reaction.... while all the inbound hypersonic jets of goo are in flight. I'm amazed they were ever able to pull it off, let alone make them reliable.
bell-cot 4y ago
Scenario I: The too-badly-damaged-to-properly-detonate nuclear warhead is now a piece (or maybe lots of pieces) of dangerous radioactive junk. Bad. But many orders of magnitude less bad than a successful nuclear detonation would have been. Scenario II: Your defenses knocked out the warhead's delivery system, but did not damage the actual (small, tough) nuclear warhead or its control systems badly enough to disable those. My bet is that the standard design spec. is "when fully armed and near-ish to the target(s), if a critical failure occurs in the delivery system, then detonate immediately". Hopefully your missile defenses intercepted it far, far away from anything that you care much about.
- ergonaught 4y ago
  I have visions of nuclear weapons systems programmers reading Scenario II and going, "Ohhhh, damn, why didn't we think of that?" and, a year from now, that's what we'll have.
  - atemerev 4y ago
    This problem was discovered and taken care of from the start of the development of modern nuclear weapon designs. See “strong link / weak link” and “always/never problem”, e.g. https://en.wikipedia.org/wiki/Strong_link/weak_link https://en.wikipedia.org/wiki/Strong_link/weak_link (I believe the diagram here is wrong, but it doesn’t require much thinking to deduce how the correct diagram should look like).
gggggg5 4y ago
Are we talking about boost phase, midcourse or terminal phase defense? In all of these cases, a successful intercept will happen tens if not thousands of kilometers from the target. A boost phase interception would happen above the launch area. A midcourse intercept would essentially happen in space and a terminal intercept would happen at the edge of the atmosphere. I'd recommend reading about Aegis, THAAD and GMD. Also see https://en.wikipedia.org/wiki/Ballistic_missile_flight_phases https://en.wikipedia.org/wiki/Ballistic_missile_flight_phase... Of course there are also stealth bombers and cruise missiles. In the case of stealth bombers, you either shoot them before the bombs are dropped or you don't (Barring some extremely conveniently located point defenses, like C-RAM) Cruise missiles? Shot down by conventional air defenses hundreds of kilometers from the target if terrain allows. Hypersonic cruise missiles? Maybe shot down by conventional air defenses.
- deleted 4y ago
  [deleted]
082349872349872 4y ago
The essence of MAD is that a strike is never "the" nuclear missile. It will consist of many missiles, more warheads, and yet more decoys. https://youtu.be/2yfXgu37iyI?t=136 https://youtu.be/2yfXgu37iyI?t=136
- mabbo 4y ago
  I wonder if there's a reasonable way to remotely guess which are the real warheads. Measure the flight profile, estimate the mass, compare the heat signature, etc. Perhaps even radiation? Could a "Star wars" system actually gain some statistical advantage given it doesn't have the resources to shoot down every missile?
  - coobird 4y ago
    The warhead(s) and decoys[1] are deployed in outer space[2]. I believe missile defense systems in this phase will use ground-based equipment like radars, and interceptors themselves use optical and other sensors to discriminate the warhead from the decoys. That said, as the linked page mentions, the decoys can have similar temperature and radar signatures as the warhead, so it's not easy. Let's not forget this is happening as these are travelling at several kilometers per second, which is no easy feat. It's best if the missile can be disabled during the boost phase before it ever deploys the warhead and decoys. [1] https://en.wikipedia.org/wiki/Penetration_aid https://en.wikipedia.org/wiki/Penetration_aid [2] https://en.wikipedia.org/wiki/Ballistic_missile_flight_phases https://en.wikipedia.org/wiki/Ballistic_missile_flight_phase...
    - chipsa 4y ago
      As sensors get better, the closer the penetration aid ends up having to have the same characteristics as a warhead filled RV. At which point you're better off just launching a real warhead than a decoy. Ex: Low orbit isn't free of air, just very very low density, so there's still some drag. Your decoy has to decelerate the same rate as the warheads (which is fractions of a mm/s^2, but still). Or the temperature of your decoy changes alot faster than the real thing, because it's light. So, they cool down faster, unless you add something to heat them up. But then we can also try to heat them up, and they'll still heat up faster than the real thing (space based laser or whatever to do this). And the newer sensors that we already have are imaging sensors, so they it's not just that the have to have the same radar signature, but it actually has to look the same to a certain extent (X band is ~2.5-4cm wavelength, so the features bigger than that need to be the same). But yes, best to do it before the missile debusses the warheads. Which is partly the point of GMD: yes, it's name has mid-course, but part of the point is that it pushes the point between post-boost and mid-course much closer to launch, which results in the warheads being released earlier and farther from the targets, which makes them less accurate. Another part of BMD that isn't commonly appreciated is that Aegis/SM-3 has sufficient performance to cover about half of the US.
fsloth 4y ago
I guess you would get a small cloud of radioactive dust without fission yield. Generally you need to create sufficient neutron flow of neutrons of very specific energy to start fission chain reaction. This happens by bringing more of the fissile material together - more neutrons cause more fissile reactions, leading to more neutrons-boom. An explosive fission will push matter away. If you create an explosion that parts the fissile material before most of the nuclei have split, it’s a dud. To get a really high yield you have to shape the geometry of the fissile material very precisely at a very specific moment so that most of the nuclei get flow of neutrons at exactly correct energy. It does not suffice to bring heat to nuclear material, or just lump it randomly together, you need to be very precise so that there is enough of the fissile at the right place at the right time. The non-nuclear detonators explosives in nukes serve two purposes: push the fissile material together fast enough, and shape the fissile material just-so due to the pressure effect. It’s really, really inmprobable to trigger the nuke by a random explosion other than the trigger one.
dazzawazza 4y ago
As an aside, if you're interested in these sort of issues read Command and Control [1]. Far too many accidents have happened and we've been lucky that there have been no accidental detonations. We've leaned heavily into safety systems that were hard to test and often poorly built. Plane crashes, fires, lost inventory, it's all in this book. An entertaining read. 1 - https://www.penguinrandomhouse.com/books/303337/command-and-control-by-eric-schlosser/9780143125785/ https://www.penguinrandomhouse.com/books/303337/command-and-...
- moosedev 4y ago
  Seconding this recommendation - great (and scary) book.
- qbasic_forever 4y ago
  It was turned into a fantastic documentary by PBS too. Very much a must watch: https://www.pbs.org/wgbh/americanexperience/films/command-and-control/ https://www.pbs.org/wgbh/americanexperience/films/command-an...
- readonthegoapp 4y ago
  i keep hearing this is a good book, and i'm sure it is. i kept trying to remember the 'nuclear author' i saw at a reading somewhere many-ish years ago, but couldn't figure out who, where, when. This is the book, if i had to guess: Nuclear Nightmares Securing the World Before It Is Too Late Joseph Cirincione Columbia University Press https://cup.columbia.edu/book/nuclear-nightmares/9780231164047 https://cup.columbia.edu/book/nuclear-nightmares/97802311640... I never read it, but I came away with the impression the guy knew what he was talking about. This video of the author doing a reading in DC seems familiar, but it doesn't fit my timeline: https://www.politics-prose.com/video/nuclear-nightmares https://www.politics-prose.com/video/nuclear-nightmares I do remember asking whatever author it was this question: What is more dangerous, nukes or global warming? And this could have been 8 or 15 years ago, not sure. But Global Warming was def not on the radar of regular people like it is today, in 2023. Author said 'nukes' and i thought to myself, 'Wrong'. Today I've changed my mind -- it's def nukes. Or global warming. I saw Daniel Ellsberg talk about nukes once, too -- he had the audience close our eyes, then he counts down from 30 seconds (the approximate amount of time from when the bomb is dropped until it detonates -- tho i guess it was actually 45 seconds) -- and he counts down, am about we set it to go off about about 8.15am, so it might inflict maximum damage and terror, kids and moms might still be rushing to/from school, people headed to work, etc. -- just kind of like another regular slow war day in Japan -- until it wasn't.
atemerev 4y ago
Well, after resolving some obvious issues (like “the warhead should execute its firing sequence precisely or nothing will happen”), we enter the realm of highly classified information, and can only speculate how the modern designs would behave (modern nuclear weapons are the product of decades of adversarial evolution, with ABMs, counter-ABM protection, and counter-counter-ABM measures being the focus of research efforts). Like, some designs were “one point unsafe”, but could be this exploited deliberately as counter-ABM protection? Or: we know that there were many efforts to allow nuclear warheads to detonate simultaneously and close to each other (so neutron flux from earlier detonations would not disrupt other devices’ firing sequences), but how exactly it relates to ABM protection? And so on and so on. Exact solutions are classified, and what we can learn from unclassified sources is mostly a speculation.
thedevindevops 4y ago
A cannonball of Uranium is ejected at high speed from the asymmetric detonation of its warhead, possibly slightly dented but otherwise intact and subcritical. If it lands in anything soft (a field, sand, etc), it ends up beneath the small crater, if anything like a building it'll have the same effect as said cannonball.
- fooblaster 4y ago
  It would be plutonium in any modern weapon.
LatteLazy 4y ago
Most interceptor systems are designed to hit missiles in the middle of their flight plan. For the US, that means over the Atlantic or Pacific ocean. So the warhead(s) likely break up and their radioactive materials are dumped into those oceans and the atmosphere above them, either in mostly intact chunks of debris, or in the form of dust when they burn up. If they did detonate (unlikely but not impossible) it would be well away from populated areas... Bare in mind that no one has actually managed to intercept
- readonthegoapp 4y ago
  don't missile get intercepted now all the time?
  - chx 4y ago
    GP is talking of ICBMs and AFAIK no one ever fired one of those in a war thanks God. The Iskanders Ukraine shoots down are short range.
    - gggggg5 4y ago
      Has there been a single documented interception of an Iskander ballistic missile? Iskander-K cruise missiles have almost certainly been intercepted, yeah.
  - LatteLazy 4y ago
    As the other commenter says I mean ICBMs. No one has intercepted one of those yet. It's a very difficult task compared to other missiles... The US navy say they managed to intercept an "ICBM like" test missile. But I don't think they've released any actual details so we wait to see.
    - chipsa 4y ago
      On the one hand, the speed makes the interception harder. On the other hand, Ballistic Missiles are ballistic. They don't maneuver, they go exactly as Newton says they go.
qbasic_forever 4y ago
It turns into a modest dirty bomb of weapons grade plutonium. This isn't actually as nasty as it sounds--in the 80s Iraq and Saddam Hussein apparently did a lot of research and testing of actual dirty bombs and found they really were not effective at all (they weren't even found to be likely to kill anyone, it would just make a small area slightly hot radioactively but was easily cleaned up like any other small nuclear fuel mishap/incident). Initiating the full nuclear chain reaction takes a very specific and controlled process which would not occur without the bomb intending it to happen. In the 80s a Titan 2 ICBM in the south actually exploded in its silo from a fuel mishap. The missile had a full hydrogen bomb on board and it was blown out of the silo and into a nearby field, still intact and unexploded. So in practice we've seen there's low risk for an unintended chain reaction. This is a great documentary on the incident: https://www.pbs.org/wgbh/americanexperience/films/command-and-control/ https://www.pbs.org/wgbh/americanexperience/films/command-an...
- kraussvonespy 4y ago
  The book Command and Control by Eric Schlosser is one of the best I've read on any subject. He intersperses the history of nuclear command and control with the AR missile silo near disaster story. Top notch reporting all around.
  - killjoywashere 4y ago
    Great book. He describes one related event: turns out the US did approximately this dirty bomb scenario once over Spain by accident. The plutonium pulverized to dust and they had to evacuate 3 square miles of farm land.
    - grugagag 4y ago
      How would that dust be cleaned up? Some kind of vacuum cleaners or is there a different way to neutralize the radioactive dust?
      - qbasic_forever 4y ago
hkpack 4y ago
Speaking from the experience of being under regular attacks from Russian cruise and ballistic rockets for the last year, I can tell you, that with enough missiles launched, you’ll have all the possible results: - some will explode in the mid air with full force - some will explode in the mid air with reduced force - some will disassemble on the intercept and won’t explode at all - some will fall to the ground and explode with variety level of force - some will fall and won’t explode at all - some will fall to the seas and rivers and may explode much later and make all other kinds of problems Successfully intercepted ballistic missiles on the final phase will arrive very close to the target, so chances for it to cause damage are much higher.
- wffurr 4y ago
  The HE warheads in conventional missiles are readily set off by impact or damage. The nuclear chain reaction in a fission warhead requires precisely timed detonation of shaped charges all around the nuclear pit; which is highly unlikely to happen in an uncontrolled fashion from damage.
  - hkpack 4y ago
    We don't know how warheads are configured. It is possible that detonating over enemy territory is still better than just falling down. So the sequence may be started if the rocket 1) knows that it is close to the enemy territory. 2) it senses damage.
- stouset 4y ago
  Not to discount your personal experience, but nuclear weapons are very different from conventional ones. A nuclear device has to go through a very specific, very precise sequence in order to create a nuclear or thermonuclear explosion. Conventional weapons don’t have this same design, and so could easily demonstrate your observed behavior. Without the firing sequence occurring, a nuclear bomb that is intercepted early becomes a dirty bomb. The nuclear material is spread out over a much smaller blast zone and can contaminate the area with fissile material. But the odds of it producing a nuclear explosion are virtually nil unless the bomb/missile has explicit countermeasures that force a detonation prior to intercept.
MarkusWandel 4y ago
If the fissile core is anything like the original Trinity test one, it relies on a solid ball of plutonium metal being compacted to reach criticality (modern ones may be hollow). This means the explosion wavefront needs to arrive simultaneously all around the ball. This is hard! A ton of the computational effort legendarily described by Feynman with his IBM tabulator/multiple coloured cards story was, I believe, just to make this work. Link to the relevant part (the whole lecture is a hoot). https://youtu.be/uY-u1qyRM5w?t=2800 https://youtu.be/uY-u1qyRM5w?t=2800 Anyway the original bomb had a lot of detonators all around that needed to be fired right. Modern ones have only two, from the little I've seen in published imagery. https://en.wikipedia.org/wiki/Pit_%28nuclear_weapon%29#Safety_considerations https://en.wikipedia.org/wiki/Pit_%28nuclear_weapon%29#Safet... One hopes this is arranged so simultaneous firing of both detonators results in a fizzle, and a precise stagger is needed. Either way though, an external explosive force will just disassemble the thing, not cause it to go off.
- tragomaskhalos 4y ago
  The Manhattan project was really two endeavours wasn't it: 1. Work out how to do the precise implosion you describe for the plutonium bomb - very difficult, and required the trinity test to verify 2. Separating enough of the the correct isotope to make the uranium bomb - the science for this was a solved problem, it was just about big engineering
kidme5 4y ago
Asking because of the renewed interest in a global missile defense system by the US? https://wikipedia.org/wiki/Space_Development_Agency https://wikipedia.org/wiki/Space_Development_Agency Lots of references in there, some seem to answer your question.

AgentK20 4y ago

Keep in mind that in order for a nuclear explosion to occur, a very precisely timed series of explosions must occur within the device to trigger fission (and then potentially fusion, depending on the type of device). If the inbound missile is kinetically damaged or destroyed before it gets the chance to trigger, then the conventional explosives will likely detonate within the missile in a way that does not reach criticality, resulting in a conventional explosion with a small amount of fallout from the nuclear core that wasn't triggered being dispersed.

verdverm 4y ago
https://www.youtube.com/watch?v=zVhQOhxb1Mc https://www.youtube.com/watch?v=zVhQOhxb1Mc has a good explanation of how nuclear weapons work. It may be possible that a missel is disabled and when it hits the ground, produces a much lower yield explosion than designed for, in particular a plutonium device, if I recall the video and extrapolate with sufficient accuracy
- adastra22 4y ago
  It is basically impossible for a plutonium bomb to generate anything resembling what you think of as a nuclear explosion unless it is deliberately triggered and experiences ideal ignition conditions. If it were to crash into the ground, be blown up by an intercepting missile, or otherwise malfunction, you'll just get a normal-bomb-sized regular conventional explosion and a bunch of toxic and only mildly radioactive plutonium strewn all over the place.
  - zinekeller 4y ago
    Just adding about the so-called "dirty bombs" (https://en.wikipedia.org/wiki/Dirty_bomb https://en.wikipedia.org/wiki/Dirty_bomb). It's not dirty because it's lethal but rather because the construction of these bombs are rather crude, which allows nearly everyone with some knowledge of bomb building to construct them. In some sense, this is more dangerous than a proper fission-type nuclear bomb.
    - deleted 4y ago
      [deleted]
    - yakshaving_jgt 4y ago
      The explanation you gave for why a dirty bomb is called as such doesn't seem to be supported by the link you provided. Rather, it's dirty because it contaminates the area around the explosion with radioactive material.
    - xadhominemx 4y ago
      That is not correct
    - tsimionescu 4y ago
      The vast majority of effects of a dirty bomb are foiled by such advanced technologies as windows and showers. The initial conventional explosion will kill and injure far more people than the radioactive dust. At worst, that dust will slightly increase cancer rates for people relatively close to the location of the bomb (say, upto a few hundred meters) over their lifetime.
      - mLuby 4y ago
        Dirty bombs are weapons of terror, not weapons of mass destruction. The true damage is caused by societal and economic overreaction from the target: fear leads to expensive security theatre, a desire for vengeance leads to lashing out with expensive unnecessary wars, uncertainty and political instability destabilizes financial markets, etc. Some diseases are similar: immune system overreaction causes more harm than the actual invader.
mabbo 4y ago
This is, imho, the correct answer. But setting aside the nuclear device, the rocket itself wouldn't survive any damage either. Rockets aren't built to be robust because that adds mass, which requires more fuel and reduces acceleration. Better to just go faster, avoid the danger. But that means any damage to the rocket is probably going to doom it.
- perihelions 4y ago
  There's no rocket left after the boost phase. Everything separates off but the warhead and its encapsulating reentry vehicle -- a compact, tough shell designed to protect it from the stresses of reentry. So it's probably far from fragile. Here's what those look like: https://en.wikipedia.org/wiki/Multiple_independently_targetable_reentry_vehicle#/media/File:W87_MIRV.jpg https://en.wikipedia.org/wiki/Multiple_independently_targeta...
denton-scratch 4y ago
> then the conventional explosives will likely detonate within the missile in a way that does not reach criticality Why? The primary in a thermonuclear bomb needs careful timing of the conventional charge. But don't they go to a lot of trouble to ensure that conventional charge dowsn't go off except under the correct control? The detonators are timed and triggered electronically. The charges are not like nitrogycerin, they won't go off on impact. I don't see why damaging the delivery vehicle should affect the bomb, unless the vehicle explodes catastrophically, destroying the bomb. And unless, I suppose, there's a failsafe installed, so that a malfunctioning vehicle automatically disables the bomb. That would make sense to me; I don't want my ICBM exploding over some place that wasn't on the target-list. Basically, I want a warhead that goes off correctly over the target, or not at all. That appears to be a fairly straightforward engineering challenge; as they say, it's not rocket science.
- ilyt 4y ago
  > The charges are not like nitrogycerin, they won't go off on impact. They will most likely go off if the warhead gets exploded tho. I doubt they test how the nuclear bombs react to getting shredded by AA
  - JoeAltmaier 4y ago
    Not bloody likely. Its a very delicate balance of geometry and timing. Hit it with a hammer (blow it up) and that's all destroyed. You'd get the same effect as blowing up a pile of parts not yet formed into the missile. That is, some radioactive material vaporized and spread around.
    - ilyt 4y ago
      I meant that the charges will blow off from explosion, not that they will blow off in exact way needed for nuclear bomb to happen
      - JoeAltmaier 4y ago
        Ah. More likely.
kidme5 4y ago
The nuke could be programmed/signaled to actually detonate if it encounters an interceptor AND is within X distance of target territory. In which case, it is an atmospheric nuclear explosion probably with EMP effects. This is one reason people stress missile defense that hits the nuke immediately over their launch site (boost phase). For NK that might mean interceptor UAVs hovering off the Korean coast or ships. But for Russia or China it means a Starlink-style system with hypersonic interceptors staged in orbit around the globe. https://wikipedia.org/wiki/Space_Development_Agency https://wikipedia.org/wiki/Space_Development_Agency This obviously has tons of flaws though. It would cause a feedback increase in nuclear stockpiling to counteract the fraction intercepted to ensure MAD.
- mikewarot 4y ago
  >if it encounters an interceptor How would it know? You can't have radar on it, because that would make it easier to hone in on, aiding interception. Also, on re-entry most objects have a highly ionized shock-wave around them, making forward facing radio communications quite difficult at best (assuming you could manage the cooling, etc)
  - kidme5 4y ago
    They (launcher of nuke) can use satellites to track their own missile and the interceptor. Also separately, communication/radar works fine through reentry plasma once you go up to 20-50 GHz frequency.
    - aPoCoMiLogin 4y ago
      that sounds like it still adds way to spot the nuke and intercept it.
    - positr0n 4y ago
      My intuition says, due to the speeds and sizes of the two vehicles and latency of communications there'd be no way to figure out if the interceptor will successfully hit the nuke until it's too late. If the interceptor misses the nuke's location by 50 microseconds it'll explode harmlessly a foot behind it. (The ICBM is probably traveling faster than the shockwave front of the explosive, depending on where it is) I don't think a radar from satellite could be that precise, that fast, and get a signal out.
mikewarot 4y ago
Shaped charges are used to penetrate Russian tank hulls in Ukraine, and work by using explosives shaped in a very specific way to invert a copper cone and turn it into a hypersonic jet of hot goo. A nuclear device is an spherical array of them, all focused inward. If any of them goes first, it pushes things out of the way, and you get a "fizzle" You also have to shower things with a neutron pulse at just the right time to kick off the chain reaction.... while all the inbound hypersonic jets of goo are in flight. I'm amazed they were ever able to pull it off, let alone make them reliable.

bell-cot 4y ago

Scenario I: The too-badly-damaged-to-properly-detonate nuclear warhead is now a piece (or maybe lots of pieces) of dangerous radioactive junk. Bad. But many orders of magnitude less bad than a successful nuclear detonation would have been. Scenario II: Your defenses knocked out the warhead's delivery system, but did not damage the actual (small, tough) nuclear warhead or its control systems badly enough to disable those. My bet is that the standard design spec. is "when fully armed and near-ish to the target(s), if a critical failure occurs in the delivery system, then detonate immediately". Hopefully your missile defenses intercepted it far, far away from anything that you care much about.

ergonaught 4y ago
I have visions of nuclear weapons systems programmers reading Scenario II and going, "Ohhhh, damn, why didn't we think of that?" and, a year from now, that's what we'll have.
- atemerev 4y ago
  This problem was discovered and taken care of from the start of the development of modern nuclear weapon designs. See “strong link / weak link” and “always/never problem”, e.g. https://en.wikipedia.org/wiki/Strong_link/weak_link https://en.wikipedia.org/wiki/Strong_link/weak_link (I believe the diagram here is wrong, but it doesn’t require much thinking to deduce how the correct diagram should look like).

gggggg5 4y ago

Are we talking about boost phase, midcourse or terminal phase defense? In all of these cases, a successful intercept will happen tens if not thousands of kilometers from the target. A boost phase interception would happen above the launch area. A midcourse intercept would essentially happen in space and a terminal intercept would happen at the edge of the atmosphere. I'd recommend reading about Aegis, THAAD and GMD. Also see https://en.wikipedia.org/wiki/Ballistic_missile_flight_phases https://en.wikipedia.org/wiki/Ballistic_missile_flight_phase... Of course there are also stealth bombers and cruise missiles. In the case of stealth bombers, you either shoot them before the bombs are dropped or you don't (Barring some extremely conveniently located point defenses, like C-RAM) Cruise missiles? Shot down by conventional air defenses hundreds of kilometers from the target if terrain allows. Hypersonic cruise missiles? Maybe shot down by conventional air defenses.

deleted 4y ago
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082349872349872 4y ago

The essence of MAD is that a strike is never "the" nuclear missile. It will consist of many missiles, more warheads, and yet more decoys. https://youtu.be/2yfXgu37iyI?t=136 https://youtu.be/2yfXgu37iyI?t=136

mabbo 4y ago
I wonder if there's a reasonable way to remotely guess which are the real warheads. Measure the flight profile, estimate the mass, compare the heat signature, etc. Perhaps even radiation? Could a "Star wars" system actually gain some statistical advantage given it doesn't have the resources to shoot down every missile?
- coobird 4y ago
  The warhead(s) and decoys[1] are deployed in outer space[2]. I believe missile defense systems in this phase will use ground-based equipment like radars, and interceptors themselves use optical and other sensors to discriminate the warhead from the decoys. That said, as the linked page mentions, the decoys can have similar temperature and radar signatures as the warhead, so it's not easy. Let's not forget this is happening as these are travelling at several kilometers per second, which is no easy feat. It's best if the missile can be disabled during the boost phase before it ever deploys the warhead and decoys. [1] https://en.wikipedia.org/wiki/Penetration_aid https://en.wikipedia.org/wiki/Penetration_aid [2] https://en.wikipedia.org/wiki/Ballistic_missile_flight_phases https://en.wikipedia.org/wiki/Ballistic_missile_flight_phase...
  - chipsa 4y ago
    As sensors get better, the closer the penetration aid ends up having to have the same characteristics as a warhead filled RV. At which point you're better off just launching a real warhead than a decoy. Ex: Low orbit isn't free of air, just very very low density, so there's still some drag. Your decoy has to decelerate the same rate as the warheads (which is fractions of a mm/s^2, but still). Or the temperature of your decoy changes alot faster than the real thing, because it's light. So, they cool down faster, unless you add something to heat them up. But then we can also try to heat them up, and they'll still heat up faster than the real thing (space based laser or whatever to do this). And the newer sensors that we already have are imaging sensors, so they it's not just that the have to have the same radar signature, but it actually has to look the same to a certain extent (X band is ~2.5-4cm wavelength, so the features bigger than that need to be the same). But yes, best to do it before the missile debusses the warheads. Which is partly the point of GMD: yes, it's name has mid-course, but part of the point is that it pushes the point between post-boost and mid-course much closer to launch, which results in the warheads being released earlier and farther from the targets, which makes them less accurate. Another part of BMD that isn't commonly appreciated is that Aegis/SM-3 has sufficient performance to cover about half of the US.

fsloth 4y ago

I guess you would get a small cloud of radioactive dust without fission yield. Generally you need to create sufficient neutron flow of neutrons of very specific energy to start fission chain reaction. This happens by bringing more of the fissile material together - more neutrons cause more fissile reactions, leading to more neutrons-boom. An explosive fission will push matter away. If you create an explosion that parts the fissile material before most of the nuclei have split, it’s a dud. To get a really high yield you have to shape the geometry of the fissile material very precisely at a very specific moment so that most of the nuclei get flow of neutrons at exactly correct energy. It does not suffice to bring heat to nuclear material, or just lump it randomly together, you need to be very precise so that there is enough of the fissile at the right place at the right time. The non-nuclear detonators explosives in nukes serve two purposes: push the fissile material together fast enough, and shape the fissile material just-so due to the pressure effect. It’s really, really inmprobable to trigger the nuke by a random explosion other than the trigger one.

dazzawazza 4y ago

As an aside, if you're interested in these sort of issues read Command and Control [1]. Far too many accidents have happened and we've been lucky that there have been no accidental detonations. We've leaned heavily into safety systems that were hard to test and often poorly built. Plane crashes, fires, lost inventory, it's all in this book. An entertaining read. 1 - https://www.penguinrandomhouse.com/books/303337/command-and-control-by-eric-schlosser/9780143125785/ https://www.penguinrandomhouse.com/books/303337/command-and-...

moosedev 4y ago
Seconding this recommendation - great (and scary) book.
qbasic_forever 4y ago
It was turned into a fantastic documentary by PBS too. Very much a must watch: https://www.pbs.org/wgbh/americanexperience/films/command-and-control/ https://www.pbs.org/wgbh/americanexperience/films/command-an...
readonthegoapp 4y ago
i keep hearing this is a good book, and i'm sure it is. i kept trying to remember the 'nuclear author' i saw at a reading somewhere many-ish years ago, but couldn't figure out who, where, when. This is the book, if i had to guess: Nuclear Nightmares Securing the World Before It Is Too Late Joseph Cirincione Columbia University Press https://cup.columbia.edu/book/nuclear-nightmares/9780231164047 https://cup.columbia.edu/book/nuclear-nightmares/97802311640... I never read it, but I came away with the impression the guy knew what he was talking about. This video of the author doing a reading in DC seems familiar, but it doesn't fit my timeline: https://www.politics-prose.com/video/nuclear-nightmares https://www.politics-prose.com/video/nuclear-nightmares I do remember asking whatever author it was this question: What is more dangerous, nukes or global warming? And this could have been 8 or 15 years ago, not sure. But Global Warming was def not on the radar of regular people like it is today, in 2023. Author said 'nukes' and i thought to myself, 'Wrong'. Today I've changed my mind -- it's def nukes. Or global warming. I saw Daniel Ellsberg talk about nukes once, too -- he had the audience close our eyes, then he counts down from 30 seconds (the approximate amount of time from when the bomb is dropped until it detonates -- tho i guess it was actually 45 seconds) -- and he counts down, am about we set it to go off about about 8.15am, so it might inflict maximum damage and terror, kids and moms might still be rushing to/from school, people headed to work, etc. -- just kind of like another regular slow war day in Japan -- until it wasn't.

atemerev 4y ago

Well, after resolving some obvious issues (like “the warhead should execute its firing sequence precisely or nothing will happen”), we enter the realm of highly classified information, and can only speculate how the modern designs would behave (modern nuclear weapons are the product of decades of adversarial evolution, with ABMs, counter-ABM protection, and counter-counter-ABM measures being the focus of research efforts). Like, some designs were “one point unsafe”, but could be this exploited deliberately as counter-ABM protection? Or: we know that there were many efforts to allow nuclear warheads to detonate simultaneously and close to each other (so neutron flux from earlier detonations would not disrupt other devices’ firing sequences), but how exactly it relates to ABM protection? And so on and so on. Exact solutions are classified, and what we can learn from unclassified sources is mostly a speculation.

thedevindevops 4y ago

A cannonball of Uranium is ejected at high speed from the asymmetric detonation of its warhead, possibly slightly dented but otherwise intact and subcritical. If it lands in anything soft (a field, sand, etc), it ends up beneath the small crater, if anything like a building it'll have the same effect as said cannonball.

fooblaster 4y ago
It would be plutonium in any modern weapon.

LatteLazy 4y ago

Most interceptor systems are designed to hit missiles in the middle of their flight plan. For the US, that means over the Atlantic or Pacific ocean. So the warhead(s) likely break up and their radioactive materials are dumped into those oceans and the atmosphere above them, either in mostly intact chunks of debris, or in the form of dust when they burn up. If they did detonate (unlikely but not impossible) it would be well away from populated areas... Bare in mind that no one has actually managed to intercept

readonthegoapp 4y ago
don't missile get intercepted now all the time?
- chx 4y ago
  GP is talking of ICBMs and AFAIK no one ever fired one of those in a war thanks God. The Iskanders Ukraine shoots down are short range.
  - gggggg5 4y ago
    Has there been a single documented interception of an Iskander ballistic missile? Iskander-K cruise missiles have almost certainly been intercepted, yeah.
- LatteLazy 4y ago
  As the other commenter says I mean ICBMs. No one has intercepted one of those yet. It's a very difficult task compared to other missiles... The US navy say they managed to intercept an "ICBM like" test missile. But I don't think they've released any actual details so we wait to see.
  - chipsa 4y ago
    On the one hand, the speed makes the interception harder. On the other hand, Ballistic Missiles are ballistic. They don't maneuver, they go exactly as Newton says they go.

qbasic_forever 4y ago

It turns into a modest dirty bomb of weapons grade plutonium. This isn't actually as nasty as it sounds--in the 80s Iraq and Saddam Hussein apparently did a lot of research and testing of actual dirty bombs and found they really were not effective at all (they weren't even found to be likely to kill anyone, it would just make a small area slightly hot radioactively but was easily cleaned up like any other small nuclear fuel mishap/incident). Initiating the full nuclear chain reaction takes a very specific and controlled process which would not occur without the bomb intending it to happen. In the 80s a Titan 2 ICBM in the south actually exploded in its silo from a fuel mishap. The missile had a full hydrogen bomb on board and it was blown out of the silo and into a nearby field, still intact and unexploded. So in practice we've seen there's low risk for an unintended chain reaction. This is a great documentary on the incident: https://www.pbs.org/wgbh/americanexperience/films/command-and-control/ https://www.pbs.org/wgbh/americanexperience/films/command-an...

kraussvonespy 4y ago
The book Command and Control by Eric Schlosser is one of the best I've read on any subject. He intersperses the history of nuclear command and control with the AR missile silo near disaster story. Top notch reporting all around.
- killjoywashere 4y ago
  Great book. He describes one related event: turns out the US did approximately this dirty bomb scenario once over Spain by accident. The plutonium pulverized to dust and they had to evacuate 3 square miles of farm land.
  - grugagag 4y ago
    How would that dust be cleaned up? Some kind of vacuum cleaners or is there a different way to neutralize the radioactive dust?
    - qbasic_forever 4y ago

hkpack 4y ago

Speaking from the experience of being under regular attacks from Russian cruise and ballistic rockets for the last year, I can tell you, that with enough missiles launched, you’ll have all the possible results: - some will explode in the mid air with full force - some will explode in the mid air with reduced force - some will disassemble on the intercept and won’t explode at all - some will fall to the ground and explode with variety level of force - some will fall and won’t explode at all - some will fall to the seas and rivers and may explode much later and make all other kinds of problems Successfully intercepted ballistic missiles on the final phase will arrive very close to the target, so chances for it to cause damage are much higher.

wffurr 4y ago
The HE warheads in conventional missiles are readily set off by impact or damage. The nuclear chain reaction in a fission warhead requires precisely timed detonation of shaped charges all around the nuclear pit; which is highly unlikely to happen in an uncontrolled fashion from damage.
- hkpack 4y ago
  We don't know how warheads are configured. It is possible that detonating over enemy territory is still better than just falling down. So the sequence may be started if the rocket 1) knows that it is close to the enemy territory. 2) it senses damage.
stouset 4y ago
Not to discount your personal experience, but nuclear weapons are very different from conventional ones. A nuclear device has to go through a very specific, very precise sequence in order to create a nuclear or thermonuclear explosion. Conventional weapons don’t have this same design, and so could easily demonstrate your observed behavior. Without the firing sequence occurring, a nuclear bomb that is intercepted early becomes a dirty bomb. The nuclear material is spread out over a much smaller blast zone and can contaminate the area with fissile material. But the odds of it producing a nuclear explosion are virtually nil unless the bomb/missile has explicit countermeasures that force a detonation prior to intercept.

MarkusWandel 4y ago

If the fissile core is anything like the original Trinity test one, it relies on a solid ball of plutonium metal being compacted to reach criticality (modern ones may be hollow). This means the explosion wavefront needs to arrive simultaneously all around the ball. This is hard! A ton of the computational effort legendarily described by Feynman with his IBM tabulator/multiple coloured cards story was, I believe, just to make this work. Link to the relevant part (the whole lecture is a hoot). https://youtu.be/uY-u1qyRM5w?t=2800 https://youtu.be/uY-u1qyRM5w?t=2800 Anyway the original bomb had a lot of detonators all around that needed to be fired right. Modern ones have only two, from the little I've seen in published imagery. https://en.wikipedia.org/wiki/Pit_%28nuclear_weapon%29#Safety_considerations https://en.wikipedia.org/wiki/Pit_%28nuclear_weapon%29#Safet... One hopes this is arranged so simultaneous firing of both detonators results in a fizzle, and a precise stagger is needed. Either way though, an external explosive force will just disassemble the thing, not cause it to go off.

tragomaskhalos 4y ago
The Manhattan project was really two endeavours wasn't it: 1. Work out how to do the precise implosion you describe for the plutonium bomb - very difficult, and required the trinity test to verify 2. Separating enough of the the correct isotope to make the uranium bomb - the science for this was a solved problem, it was just about big engineering

kidme5 4y ago

Asking because of the renewed interest in a global missile defense system by the US? https://wikipedia.org/wiki/Space_Development_Agency https://wikipedia.org/wiki/Space_Development_Agency Lots of references in there, some seem to answer your question.