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Nuclear weapons for anti-missile defense

  1. Jan 10, 2014 #1

    lavinia

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    I couldn't find an compatible heading for this question and decided to place it here since it deals with nuclear engineering, sort of.

    From the documentary movie, Trinity and Beyond, which is a history of the American nuclear weapons program, it seems that high atmosphere nuclear detonations were tested for anti missile and anti-bomber defence. Incoming missiles from the Soviet Union would be destroyed in transit by high altitude thermo-nuclear blasts. As soon as the enemy missiles were detected, nuclear tipped missiles would be launched to destroy them

    Does this technology work? Why wouldn't one use it instead of Star Wars technology?

    Also it seems that testing was done to created a radioactive debris shield in space that would disable incoming missiles. Why wouldn't this work?
     
  2. jcsd
  3. Jan 10, 2014 #2
    Nuclear explosions in the atmosphere are bad
     
  4. Jan 10, 2014 #3

    SteamKing

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    This article on the Nike program should answer your questions:

    http://en.wikipedia.org/wiki/LIM-49_Nike_Zeus

    Setting off a lot of 400 KT warheads overhead doesn't do anybody much good.
     
  5. Jan 11, 2014 #4
    It works. Sorta kinda. It is obviously not practical to perform a full-scale test of it, though (think of the fallout).
    E.g. how much EMP will this generate? Will radars still function and be able to track next wave of ICBMs to intercept?

    I think you are mistaken. Such shield needs to be incredibly dence to be able to affect incoming missiles in any way - tens of thousands of nukes at least. I don't think there ever was such a plan.
     
  6. Jan 11, 2014 #5

    Astronuc

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    Yes - adding fission products and activated elements (radionuclides/fallout) to the environment is generally considered undesirable.
     
  7. Jan 11, 2014 #6

    lavinia

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    Maybe so although the idea was mentioned in the documentary so it was certainly considered at least as an idea.
     
  8. Jan 11, 2014 #7

    lavinia

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    The link that SteamKing gave gives a sort a kinda answer as well. It seems that MIRV's were a big deterrent to the deterrent and the system was eventually abandoned for cost and doubt about its viability. Edward Teller for instance argued that it would be cheaper to get around the system than to develop it.
     
  9. Jan 11, 2014 #8

    lavinia

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    This is really an aside but the documentary said that over three hundred nuclear tests were done. What then was the actual fallout - so to speak - of all of these tests?
     
  10. Jan 11, 2014 #9
    The effect of fallout is time dependent. After a long time the radionuclides decay to much less active isotopes, and in doing so release all sorts of nasties. You could probably estimate the total dose inflicted on the planet give or take an order of magnitude...
     
  11. Jan 11, 2014 #10

    SteamKing

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    From the Nevada Test Site (north of Las Vegas), the fallout from the atmospheric tests there was caught by the prevailing winds and deposited over the eastern and central portions of the continental US. The atmospheric tests performed in the Pacific atolls produced fallout which largely was dispersed over water, except for a few incidents (like the early H-bomb tests) where fallout contaminated a Japanese fishing fleet and some nearby inhabited islands.
     
  12. Mar 14, 2014 #11

    Morbius

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    a_potato,

    The following table courtesy of the Health Physics Society chapter at the University of Michigan gives the comparison of how much dose is due to fallout from nuclear testing vis-a-vis other source:

    http://www.umich.edu/~radinfo/introduction/radrus.htm [Broken]

    Fallout is <0.03% of the background dose. Mother Nature gives you over 3000X the dose as does fallout.

    Greg
     
    Last edited by a moderator: May 6, 2017
  13. Mar 14, 2014 #12

    SteamKing

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    At the time that these tests were made, microelectronics were in their infancy and not very widespread. Vacuum tubes were still very common in radios, televisions, avionics, etc. High altitude nuclear detonations produce electromagnetic pulses (EMP), which fry unshielded microcircuits but which leave vacuum tubes unaffected. If you were to make a modern nuclear weapons defensive systems using high-altitude nuclear explosions, all computers and other systems dependent on microelectronics would have to be shielded against EMP or risk destruction.
     
  14. Mar 14, 2014 #13

    etudiant

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    The initial ABM nuclear warheads were very large, in the 2-5 megaton class, presumably because the intercept accuracy was low. The test ban treaty and the obviously damaging consequences from high altitude nuclear explosions helped end that effort. The explosion effects help blind the guidance radars for subsequent missiles, which undermines the defense effort.
    It is probable that the research labs are considering what could be done using much smaller nukes instead of the current 'hit to kill' warheads. A tiny nuke, say a kiloton, would be a very effective anti missile weapon with much less self impact. However, there is no practical effort ongoing, partly because of treaties, partly because Congress has prohibited new nuclear warhead development.
     
  15. Mar 16, 2014 #14

    lavinia

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  16. Mar 16, 2014 #15

    analogdesign

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  17. Mar 16, 2014 #16
    hahaha analogdesign;

    I think the problem of EMP, fallout, and radar blinding is probably overestimated. The first two effects are relatively localized: EMP is subject to the inverse square law and fallout, as another poster pointed out, of a single nuclear event would hardly register above background. Radar blinding can be mitigated, in part, with distributed sensors and diversified bandwidths.

    In the Nike Zeus program a nuclear warhead was used to make up for lack of targeting precision. Once hit-to-kill kinetic interceptors were proven there was no longer an incentive to use nuclear warheads; the kinetic interceptors were far cheaper.
     
  18. Mar 16, 2014 #17

    SteamKing

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    Yes, but the OP asked why nuclear warheads weren't being used for ABM defense. And, it's unlikely that an attack would involve the interception of just one missile; after all, modern strategic missiles are equipped with multiple re-entry vehicles which ALL have to be destroyed in order to prevent any nuclear hits.

    When atmospheric testing of nuclear devices was still permitted, several different atomic devices were detonated to gather data about the extent and damage the EMP could cause. As a result f these tests, military aircraft and naval vessels receive special hardening against the effects of EMP so that vital communications and other electronic systems remain operational in the event that an atmospheric nuclear blast is encountered.

    http://en.wikipedia.org/wiki/Nuclear_electromagnetic_pulse

    Because of various factors, it is hard to predict what the effect of EMP, fallout, and radiation will have on ground- and air-based systems, which is why these systems may be over-designed.
     
  19. Mar 16, 2014 #18
    True but if the MIRVs were deployed early they would have spread out enough to require multiple interceptors, nuke or not.

    For EMP I dont doubt the problem, just the range. If the intercept occurred over the artic or pacific then few systems would be close enough to be effected, including sats.
     
  20. Mar 17, 2014 #19

    Morbius

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    sparke_pony,

    You are limited by how far you can spread out your MIRVs; since you want to hit the target. For example, Russian warheads will probably be targeted at US ICBM sites in North Dakota, Montana, and Wyoming. That means there's a pretty narrow angle in which to disperse MIRVs.

    The concern about radioactivity is kind of a "red herring". At the time one would use this system, one would have Russian warheads inbound. So one has a choice; take out the incoming warheads with your own small warheads with the detonation at high altitude; or you can do nothing and suffer the detonation of a large Russian warhead near the surface. There's no avoiding the radioactivity if someone has launched nuclear missiles.

    As far as not being able to test; the aerodynamic tests of being able to intercept an incoming missile can be done with dummy warheads. As far as the nuclear testing of the interceptor warhead, that can be done underground, and was. For example, the Cannikin test which was conducted underground on Amchitka Island, Alaska was a test of the warhead for the Spartan interceptor missile. Here's a video about the test:



    Basically, the reason the programs were not pursued is that the USA and the Soviet Union decided not to pursue them and entered into the 1972 ABM - Anti-Ballistic Missile Treaty where both sides agreed to limit missile defenses.

    Greg
     
    Last edited by a moderator: Sep 25, 2014
  21. Mar 17, 2014 #20

    SteamKing

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    The EMP extends to the visual horizon from the initial burst point. If a single warhead were detonated at the proper altitude over Kansas, the effects of EMP would extend over the entire continental US. See the article in Post #17 for how the strength of the pulse drops off with distance from the blast.
     
  22. Mar 17, 2014 #21

    Morbius

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    sparkle_pony,

    Assume a position at which you are going to release your MIRVs and have them start to spread out.

    Now calculate the maximum angle that you can have them spread out, and still hit Wyoming, Montana, and North Dakota which is where our missiles are.

    Yes - you can spread your MIRVs out in a wide angle so they are difficult to hit; but then those MIRVs aren't close enough together to hit Wyoming, Montana, and North Dakota.

    The angle to hit the US missile fields in the above States from Russia is fairly narrow.

    Depending on where your interceptors hit; they are in a fairly narrow cone.

    Greg
     
  23. Mar 17, 2014 #22
    But even a narrow cone is enough spread. Our intuition tells us that nuclear weapons can destroy anything within 10s of km. Games like "Missile Command" reinforce this perception. That is true for soft targets (read: cities) but not true for hardened targets like an RV. MIRVs spread over even ~5 km would be too disperse to negate with a single nuclear warhead tipped interceptor but still close enough to effectively attack a distributed target such as a missile field (note that silos are separated by large distances) or a metropolis (think LA).

    But all this is irrelevant. Even if multiple RVs could be negated with a single nuclear tipped interceptor the enemy would just adapt their shot doctrine by spacing launches in time and from different launch points. That would ensure no RVs would be in roughly the same place at the same time. Hence it would be back to one interceptor for one warhead, and hit-to-kill kinetic interceptors would (economically) outperform nuclear interceptors.

    RE: EMP I don't know enough about it to say one way or the other but just note that the trajectories of missiles in a northern hemisphere conflict will have most interceptions occurring over the Artic, far from Kansas.
     
  24. Mar 18, 2014 #23

    SteamKing

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    You are assuming that the RVs can fly thru a nuclear blast and not suffer any ill-effects, either to the components inside the RV or to the ballistic trajectory the RV is on once it leaves the missile bus.

    Again, you are assuming that the interception over the Arctic has worked flawlessly. But what if it doesn't? What if it takes multiple shots to take out an incoming warhead, shots that can't be made over the Arctic?

    Further, not all nuclear strikes have to come over the Arctic. Russia has ballistic missile subs like the US, which are stationed off the Atlantic and Pacific coasts. If you want to cause some EMP chaos, detonate a nuke over the eastern seaboard. The EMP would wipe out a lot of financial and government records stored on unhardened computers, not to mention putting millions of people in the dark due to damaged electrical grids. It would make the aftermath of hurricane Sandy seem pleasant.
     
    Last edited: Mar 18, 2014
  25. Mar 18, 2014 #24

    Morbius

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    SteamKing,

    I'm making NO such assumptions about flying through nuclear blasts. I'm just pointing out that the missiles have to stay within a cone, and the base of that cone is one of our US Air Force bases that has ICBM missiles. The size of the the Air Force base relative to the distance to the Russian missile fields is small in comparison; and hence the cone angle is pretty narrow.

    I'm also well aware that not all launches will come over the pole and that Russia has missile subs. However, the Russians have a larger fraction of their missiles as land-based than we do.

    Nuclear-tipped missiles weren't a "one-size fits all defense" that was supposed to handle everything.

    You also have to separate the missile defense from whether you get into a war or not.

    The purpose of developing these interceptors was that *given* a Russian attack, and *given* that a large fraction, although not all; of the attack would be missiles coming over the pole; is there anything you can do to blunt the attack, or are you just going to have to absorb the full force of the attack. The answer is that one can certainly blunt the attack with nuclear-tipped missiles.

    However, both the USA and the then Soviet Union decided not to pursue this line of defense and save some money; and that is a purely political decision.

    Whether one gets into a nuclear war or not is a totally different question and the probability of a war is not increased by having a partial defense.

    Greg
     
  26. Mar 18, 2014 #25

    SteamKing

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    @Morbius: I was responding to sparkle_pony rather than to your posts. He wants to minimize the effect EMP would have on US electrical and electronic infrastructure, which I don't think can be easily ignored, given recent history with recovering from natural disasters like Katrina and Sandy, not to mention cascading power blackout incidents on the US East Coast in 2003.

    I agree that the whole idea behind nuclear-tipped interceptors was not well thought out, and even if it had survived into the 1970s or 1980s, absent the ABM treaty, it would have required that hardening of key assets against EMP be made lest these assets would be damaged or destroyed if an interceptor were used.
     
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