8 ms·

Why is it so hard to shoot down a missle? I always thought that ballistic missles travel with a very predictable speed and direction. So hitting them should be

• Symmetry 9y ago
  They're going very fast and even small errors in the estimate of their position and velocity will be enough to miss. Also, the motion is less predictable if they're in the atmosphere.
  • agumonkey 9y ago
    Sure if you try to catch a bullet with a bullet you're making your life harder. Anyway to increase the interception surface/volume ?
    • trisimix 9y ago
      Explode the interceptor?
      • olympus 9y ago
        This doesn't work well for ballistic missiles. A few ounces of shrapnel doesn't knock the missile very far from it's trajectory. You'd have to get lucky to break the fuse, and even then you'd have a big hunk of explosives heading toward the target and making a big crater. Plus a lot of old missiles have such simple fusing systems that you probably won't break them with just a bit of shrapnel anyway.
        • Bartweiss 9y ago
          As I understand it, the only serious "explode the interceptor" proposal was to use nuclear interceptors against ICBMs. That provides a modest radius of non-projectile destruction, and more importantly provides a large radius of fuse/control-disrupting radiation. So when it comes to "shooting down a Scud near the ground over a city", you're exactly right. Blowing up your interceptor only works when you've got a high-tech target and are willing to make quite a mess yourself to stop the thing.
          • blattimwind 9y ago
            Well detonating nuclear warheads (literally) near some important asset of yours is probably always some kind of last ditch effort.
            • bigiain 9y ago
              I did a tour of the Nike missile site in the Marin Headlands / Golden Gate Park once. They were very careful to "neither confirm nor deny" whether the site ever had nuclear payloads, but they _did_ make a point to tell everyone that the beautiful mechanical targeting computers had Sacramento programmed in as a target, "just in case"...
            • Bartweiss 9y ago
              Yeah, probably not the sort of thing you go and do to stop a 5-kiloton conventional warhead.
            • Symmetry 9y ago
              Not necessarily, it would be going off pretty high. Much higher than in this video with people directly underneath. https://www.youtube.com/watch?v=BlE1BdOAfVc https://www.youtube.com/watch?v=BlE1BdOAfVc
      • agumonkey 9y ago
        having something deployed near encounter ... damaging flare/shrapnel, a flock of timed explosive ...
    • orclev 9y ago
      Not really, I mean, your opponent is the one controlling the size of the thing you're trying to intercept and they're not going to be trying to make things easier on you. The only viable option given that is to go for area saturation and basically play the odds, but that's really expensive because not only do you need lots of interceptors in that case, but each one needs to be capable of getting a kinetic kill since there's no guarantee which one (if any) will actually hit. At some point I imagine the interceptors become a bigger danger to each other than they are to the thing you're trying to intercept.
      • agumonkey 9y ago
        I see. Were there research into non destructive interception ? a missile catching up another one and binding to it to divert it ?
        • khuey 9y ago
          That would be even harder because now you need to match position and velocity instead of just position.
          • agumonkey 9y ago
            I understand but I'm still curious..
    • liotier 9y ago
      > Any way to increase the interception surface/volume ? Yes - the usual way is to fit the interceptor with a nuclear warhead (see Sprint, Spartan and Nike Zeus on the US side - Fakel 51T6, Novator 53T6 and S-300PS/S-300PM on the Soviet side)... But it has sort of fallen out of fashion...
      • nabla9 9y ago
        These weapons used enhanced radiation warhead (neutron bomb). The mechanism was use of neutron flux to disable incoming nuclear warhead. Radiation hardening the warhead against this type of attack would make it less effective.
        • rdtsc 9y ago
          Wouldn't the neutron flux mess with the properties of the nuclear payload? Shielding against a neutron flux from nuclear explosion probably not practical given the sizes warheads.
          • jhayward 9y ago
            If I recall correctly the case of the re-entry vehicle tends to be stuff like depleted uranium, which is pretty good protection against neutron flux up until the point where it begins significant breeder contributions. You'd basically have the hit the vehicle anyway to get close enough for that.
            • rdtsc 9y ago
              Uranium or lead, heavy nuclei that shield well against gamma radiation would do little for neutrons. Neutrons needs something with light atom like hydrogen - water or maybe polyethylene and lots of it to slow down. So a small nuclear explosion which emits a neutron pulse might work pretty well. It would hellish if it somehow exploded over a population center, though. Didn't get hit by the ICBM (good). Everyone's bones melted (bad).
          • nabla9 9y ago
• arethuza 9y ago
  Here is a video of the awesome Sprint ABM missile - (0 to Mach 10 in 5 seconds) - it includes a near miss of an ICBM RV and the RV makes the Sprint look slow: https://www.youtube.com/watch?v=msXtgTVMcuA https://www.youtube.com/watch?v=msXtgTVMcuA Edit: Sprint was meant to defend against ICBMs - but the idea is the same, ballistic missile warheads are going very fast and really aren't that big.
  • CalChris 9y ago
    My dad worked on Sprint. That near miss would have been a definite hit since Sprint was armed with an EMP warhead, a small nuclear device with a few kilotons of yield. Dunno how it would have faired against a MIRV. It was cancelled after the ABM treaty.
    • arethuza 9y ago
      You may know this already, but Vernor Vinge did a neat short story where an aged Sprint missile (or something very similar) plays an important role: "The Whirligig of Time".
      • Fjolsvith 9y ago
        Vernor Vinge. Best Sci-fi story I ever read that made me feel the VASTNESS of space was written by him: A Fire Upon The Deep.
        • eric_h 9y ago
          I'm not sure I'd give it the title of the Best scifi story, but it's definitely very good, so I'll at least second the recommendation.
          • Fjolsvith 9y ago
            I did qualify my "Best" recommendation.
• tossandturn 9y ago
  Ballistic missiles move very fast. Repost: http://www-users.math.umn.edu/~arnold/disasters/patriot.html http://www-users.math.umn.edu/~arnold/disasters/patriot.html
• timbrah 9y ago
  Some ballistic missiles deploy counter measures. So it can become difficult to know what object is dangerous or not.
  • Finnucane 9y ago
    Decoy warheads, waste material to confuse tracking systems, etc. For every offense there is a defense.
• saiya-jin 9y ago
  It was described as trying to hit a bullet with another bullet, but in this case both of them are super fast ones. Complications I can think of: 1) ever seen a missile being fired and flowing? It isn't a smooth movement, rather wobbling in +- target direction. I presume this is due to turbulence in the air and resulting corrections by guiding software. Double the issue due to target and pursuer facing random turbulence on their own 2) some SCUDs have some sort of simple 'randomizer' in their flight for exactly these reasons - to confuse simpler defense (ie boat-based gatlink types which fires dumb explosive projectiles) - the target is still in aim, but there are random movements around axis of movement 3) sensors are/were not perfect, non-ideal conditions (clouds, night, cold, humidity, dust), bugs in software etc
• abhi3 9y ago
  It's the velocity that makes things tricky. Imagine trying to hit a bullet with a bullet, you may know where it's being fired from and where it's headed, how fast it's going, the wind speed all other variables but hitting it would still be an impossible task. One way to improve missile defense accuracy would be to use a small nuclear warhead but that's impractical when defending populated areas and anyway your adversary can make new missiles more quickly an cheaply than you can make nuclear bombs. Modern missiles make things more complicated by using multiple re-entry vehicles, midflight maneuvering, creating a cloud around the warhead to prevent targetting etc.
• apocalyptic0n3 9y ago
  I don't recall the exact answer (and it looks like others have already supplied info) but I saw someone explain it in detail once and wrap it up with a quote from the Star Trek reboot: "It's like trying to hit a bullet, with a smaller bullet, while wearing a blindfold, riding a horse."
• zaarn 9y ago
  Atleast with an ICBM you are talking about velocities that are still close to suborbital, ie over a kilometer per second, Quora sets the terminal phase velocity at 30'000 kph (around Mach 30, pi by thumb, of by around 20%) Hitting something that is moving at Mach 30 towards you is already hard. Especially considering this thing moving towards you is also burning up in the atmosphere, thus you only have that bright spot which will be larger than the actual missile core. However, if it's moving exactly (or almost) at you, it's not impossible but still hard. If it is not moving towards you but rather along your view, you have to match a significant portion of it's speed, which basically means building a ICBM to hit another ICBM. And going that fast takes a while. If it's moving away from you, you can always give up.
• olympus 9y ago
  Missiles go extremely fast. Like stupid fast. Most ABM systems today use hit-to-kill, which means that you actually have to make contact with the missile to kill it. Physically hitting something that small and fast from a long distance away is hard even if you know exactly where it's going to be. Terminal guidance needs to be very accurate, since in the last second the missiles are a mile apart. With an update rate of about 10 hZ, you have to make your final correction that is accurate to about two feet (the diameter of the missile) over about 1/10th of a mile. That's tough. Most other missile systems (like surface-to-air or air-to-air systems designed to kill planes) have proximity fuses, and don't need direct contact, they just blow up nearby and throw shrapnel into the plane. That's enough to kill a plane, but doesn't work very well to knock a ballistic missile off it's trajectory.
  • pdelbarba 9y ago
    To add to this, the closing speeds are so fast that you would need to detonate explosives far in advance for anything to happen anywhere near the target. If you detonate at the usual anti-aircraft distances (a few meters), the time it takes for the detonator to fire and for the shock wave/chemical reaction to propagate though the explosive mass would leave the shrapnel cloud way behind the target.
    • grkvlt 9y ago
      Wow, I hadn't actually thought of this. So, I assume that's why you go for hit-to-kill kinetic warheads, then, and just solve the accuracy issue rather than accuracy plus tricky timing issues?
      • mohaine 9y ago
        I wouldn't think so. Hit to kill is going to have the same but worse timing issues as a proximity hit since the size is much smaller. I would guess the real reason is that if the target is ballistic, you need to actually "kill" it, not just wing it like you can with an airplane. If you wing it the warhead will still fall in roughly the same place with a probably intact warhead. To be safe you want to actually destroy the warhead. Worse case it goes off at point of impact, which is better than on the target.
• Amorymeltzer 9y ago
  Years ago, in my high school Phsyics C class, the teacher gave us an exam which was just the process of calculating how to intercept an (IC)BM. It was a really great exam, leading you through all the steps required, and gave the answer really clearly. It's incredibly hard. I won't repeat sibling comments about how difficult the actual interception is, but will add that you likely have seconds AT BEST for your own launch to take place. You can do guidance mid-air, but miss the window...
  • gozur88 9y ago
    As with any X vs Y weapon, the scenario matters a whole lot. If you know where the missile is going and your interceptors are launched from that area you have plenty of time. This is the situation the USN is looking at with the new Chinese anti-ship ballistic missiles. On the other hand, a system to protect the continental United States from incoming missiles from anywhere to anywhere was always fanciful.
• Nokinside 9y ago
  There is always cone on uncertainty around the missile position and speed and interceptor position and speed. Both the missile and interceptor must meet at the same place at the same time. The time window decreases with speed, so timing is everything. Faster the incoming missile, harder it is to intercept. If the speed delta between incoming missile and interceptor is to high, interceptor can't correct it's course fast enough to hit the missile. Interceptor has inertia and it's deflectors or thrust vectoring can correct it's course only so fast. Interceptor positioning on the ground is also important.
• jasonwatkinspdx 9y ago
  Why is it so hard to throw a bullseye in a game of darts? You know the weight of the dart and the location of the target. Why don't we hit it every time? Even if interception is conceptually simple, the speeds and distances involved make it a very challenging problem. Additionally, you're starting from a false premise that ballistic missiles don't maneuver. Some of them, particularly MIRV ICBMs, are highly maneuverable.
  • deleted 9y ago
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