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Neutronium armor

  1. Jul 24, 2005 #1
    As many of you know, neutronium is a type of matter found in neutron stars. It is incredibly dense (hundreds of millions of metric tons per cubic centimeter) and consists of neutrons sitting right next to each other. In sci-fi (e.g. star trek) neutronium is sometimes used as nearly indestructible armor.

    Assuming neutronium armor could be made, how effective would it actually be for protection? IIRC, the force holding neutrons together is far stronger than what holds atoms and molecules together, so on the surface the purported toughness seems reasonable if such armor could be made. But I'd like to be sure. What do you physics experts think?
     
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  3. Jul 24, 2005 #2

    Hurkyl

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    The problem is trying to produce the force that holds the neutronium together, and how to avoid crushing the wearer and everything around him in a 30* mile radius in the process!

    Neutroniu does not stay together of its own volition: it very much wants to explode. It takes the man of an entire sun packed into the (much smaller) volume of a neutron star to keep it together.


    *: number picked out of thin air
     
  4. Jul 24, 2005 #3

    Astronuc

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    This sounds like Isaac Asimov's Foundation series and the 'nucleics' concept - micronuclear devices.

    As Hurkyl pointed out, the conditions required for neutron stars preclude the proximity to humans. The same goes for stars - one cannot develop a fusion power source comparable to a star - the pressures and radiation fluxes are simply too great.
     
  5. Jul 24, 2005 #4
    DOOMSDAY MACHINE!!!!!!!!!
    that episode was awesome.

    not suitable for like armor to wear on your person.be could for a VERY BIG spaceship, though....although that would make it really difficult to move...
     
  6. Jul 25, 2005 #5
    Interesting, but then what overcomes the strong force for neutronium to naturally explode? I had heard about the alleged instability of neutronium outside the pressures of a neutronium star on the Internet, but I was suspicious because I didn't know what could overcome the strong force that would seem to hold neutronium together.
     
  7. Jul 25, 2005 #6
    Perhaps so, but unfortunately that really doesn't answer my question. If such armor could be made...

    As I said earlier, I had heard about the alleged instability of neutronium outside the pressures of a neutronium star on the Internet, but I was suspicious because I didn't know what could overcome the strong force that would seem to hold neutronium together. See for instance, http://www.everything2.com/index.pl?node=neutronium I’m not sure which website to trust, though the latter does seem to make the most sense to my limited knowledge of physics.
     
  8. Jul 25, 2005 #7

    Hurkyl

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    Gravitational confinement.

    Think about this: what force is stopping the neutron star from collapsing into a black hole?
     
  9. Jul 25, 2005 #8
    Can you be a little more specific? Neutronium is very dense and thus has more gravity per cubic centimeter than normal matter. But how exactly would this overcome the strong nuclear force binding it together?


    To be honest, I don't know. All I remember is that given a radius r there must be certain amount of matter (often an enormous amount) needed within that radius for it to become a black hole. So, my best guess for that answer is that there is not enough matter for the star to collapse into a black hole.
     
  10. Jul 26, 2005 #9
    Basically what they're trying to say (I think) is that in a neutron star, the particles are held together out of the sheer incredible gravitational force that holds any celestial body together. Because of the opposite force the particles exert, the star does not collapse into a black hole.

    However, in a smaller "armor-like" usage, there would be no massive graviational force to hold the particles together. There would have to be some other substitute force to do this, which would render any kind of armor basically pointless.
     
  11. Jul 27, 2005 #10
    Except that the substitute force would (presumably) be the strong nuclear force--one that does not require a neutron star. In atoms, the strong nuclear force is what holds the nucleus of protons and neutrons together. The idea is that neutronium--albeit very dense--would be held together by the strong nuclear force as opposed to the relatively wimpy atomic bonds. If so, then it seems it could theoretically be used as nearly indestructible armor (as in Star Trek episodes).

    If neutronium were to "explode" or at least be unstable outside a neutron star it seems that there would have to be something countering the strong nuclear force that would ordinarily hold neutrons together. My question: what is it?

    In some websites such as http://www.everything2.com/index.pl?node_id=1185582 seem to say that neutronium could theoretically act as armor, whereas some say neutronium would be unstable outside of a neutron star. I'm not sure which website to trust, so I came here.
     
  12. Aug 4, 2005 #11

    Chronos

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    Hurkyl was hinting at the 'Pauli exclusion principle', which is what prevents a neutron star from further collapsing to form a black hole. If you attempted to ferry off with 'neutronium' you mined from a neutron star, it would decompress like a fish yanked from 10,000 feet, only worse... much worse.
     
  13. Aug 4, 2005 #12

    Haelfix

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    For that matter getting anywhere near a neutron star would be a pretty bad idea. EG how best to implode a human being in 1 short step.
     
  14. Aug 4, 2005 #13

    Nereid

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    Now, how quickly would a human, somehow 'instantly' transported to a spot some, say, 1 km above the surface of an NS:
    a ) be ripped to atoms/molecules, by the tidal force or the magnetic field?
    b ) 'fall' to the surface of the NS (how fast would they be going when they hit, assuming the NS has no 'atmosphere')?
    c ) become smeared as a monolayer (atoms? neutrons??) over the surface of the NS?
     
  15. Aug 4, 2005 #14

    russ_watters

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    You're missing the point (which is ok, because no one has said it yet) - the strong nuclear force does not apply here. The force that keeps electrons orbiting atoms and atoms from collapsing into neutronium is electromagnetism and that force doesn't just vanish when the star collapses. Its still there, trying to separate the electrons from the neutrons, but gravity is what prevents that. Free neutrons are not stable particles.

    If a ball of neutrons were a stable configuration of sub-atomic particles, every nuclear reactor would create one, because they are chock-full of free neutrons, floating around. They'd collect piles of them on the bottom of the reactor.

    Caveat: this isn't my area of expertise, so if I got this wrong, someone please correct me. :wink:
     
  16. Aug 4, 2005 #15

    Art

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    Although it takes intense gravitation to create neutronium, once made would it be necessarily unstable if removed from the environment that created it? However with regard to the op, the main problem with making armor from neutronium is that as far as I know neutronium in a neutron star is believed to be a liquid?
     
    Last edited by a moderator: Aug 4, 2005
  17. Aug 4, 2005 #16

    Art

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    The neutron (plus a neutrino) is created when a proton and an electron are combined together. The original electron and proton would no longer exist to seek separation.
     
  18. Aug 4, 2005 #17

    Hurkyl

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    I confess that I cannot prove that, once removed from the neutron star, that some other mechanism will manifest that will provide a confining force equal to that of the gravitation of the neutron star.

    However, I see absolutely no reason to suspect such a force will manifest. Do you?
     
  19. Aug 4, 2005 #18

    Astronuc

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    If it could be made, it would be an effective armor. The mass density (millions of metric tons per cubic millimeter) would be sufficient to effectively absorb any project impacting it.

    On the other hand, it would probably weigh a heck of a lot (millions of metric tons) which means it would take an enormous amount of energy to move anywhere - even just down the street. On the earth, it would probably collapse upon itself and crush whomever was inside, so as an armor it would seem counter-productive - not to mention all those neutrons decaying into protons and beta particles, which would irradiate the occupants of the armor.

    Neutrons don't accumulate in a reactor, which has normal atomic densities. Neutrons scatter and are absorbed by the fuel, coolant/moderator and structural materials. There are many more atoms (nuclei) than neutrons. A neutron flux in a power reactor is on the order of 1014 n/cm2-s, while the atomic density is on the order of 1022 n/cc.
     
  20. Aug 4, 2005 #19

    Art

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    Ignoring your sarcasm, why would a confining force be necessary? What is the force that would be trying to push the neutrally charged neutrons apart which needs to be overcome? When industrial diamonds are created using tremendous pressure they don't suddenly revert to their original form when the pressure is removed.

    Edit: From Wikipedia
    Seems perhaps it is not quite so obvious that neutronium would need a confining force.
     
    Last edited by a moderator: Aug 4, 2005
  21. Aug 4, 2005 #20

    Hurkyl

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    It comes from the Pauli pressure. (Or degeneracy pressure)


    In an ordinary solid or liquid, the electromagnetic force will tend to pull nearby molecules together (unless they're too close, in which case they'll be repelled). Without a sufficient force to contain the molecules, the substance would evaporate into a gas simply through the natural motion of the molecules within the substance.


    Because the neutrons of neutronium are packed so tightly, there is an enormous variance in their momentum, by the HUP. Without any sort of force to contain the neutrons, they'll simply go on their merry way, much like the particles of a gas.
     
  22. Aug 4, 2005 #21
    Why not?


    Ah, so it’s the electrons mixed into it that makes it unstable. I can understand that. A similar thing happens to elements with high atomic numbers. The positive charge of all those protons "add up" and make the nucleus unstable.

    Okay, but what if "pure" neutronium were extracted instead? That is, a big glop of neutrons sitting right next to each other side by side? Wouldn't the strong nuclear force hold them together? If not, why not?
     
  23. Aug 4, 2005 #22
    Agreed, but I was considering something more like armor for a starship or starbase. What about a coating of neutronium a few angstroms thick (supposedly being held together by the strong nuclear force)? It would certainly push its weight into more reasonable limits, but (kilogram for kilogram) would it be worth it? Would it really do a better job than conventional armor of the same mass? Neutronium would seem to have the benefit of the strong nuclear force, but I don’t know.

    So neutrons spontaneously decay into protons and beta particles? If so, why do they not do so in the nucleus of atoms (in stable elements, e.g. Titanium)?
     
  24. Aug 4, 2005 #23

    russ_watters

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    Covered in the rest of the post...
    Pretty much, yep.
    No. The strong force just doesn't act in that way. It doesn't exist for free neutrons. Neutrons are unstable and have about a 10 minute half life. They would simply decay.

    I hate to sound like a broken record, but this is kinda redundant and there isn't really anything else to say besides "it just doesn't work that way". 1 + 1 does not equal 3. Why? It just doesn't.

    Maybe it would be helpful if we turned this around: what basis do you have for believing the strong force would hold a free neutron together?
    Because inside atoms, the strong nuclear force does exist and holds them together.

    http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html

    Neutrons decay into a proton and an electron.
     
  25. Aug 5, 2005 #24

    Chronos

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    A neutron in the nucleus of an atom is prevented from decaying [in most cases] by the nuclear strong force. Free neutrons [i.e., not captured by an atom] are only constrained by the nuclear weak force. The quarks comprising the neutron are not rigidly bound to each other as they are when subject to the nuclear strong force and will decay [half life ~10 minutes] into the lighter and more stable proton by radiating out an electron and antineutrino. A neutron star is the exception to this general rule... we would otherwise be calling them proton stars! The enormous gravitational pressure basically makes the whole thing behave like a gigantic atomic nucleus. As Hurkyl noted, unless there are new physics waiting to be found [which is always a possibility] neutronium would not be stable once released from the crushing gravitational field. That aside, there are serious logistical issues... like what kind of 'scoop' would you use to harvest your neutronium? Any material composed of atoms would disintegrate before it reached the surface of a neutron star.
     
  26. Aug 5, 2005 #25

    Art

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    Doesn't the Pauli exclusion principle simply prevent 2 neutrons occupying the same place thus preventing the neutronium collapsing further and becoming a black hole? If there is a repulsive force causing an explosive like expansion where is this force coming from as I thought Bosons were not involved in the Pauli effect?
    Given that without the electromagnetic force, neutronium outside of a neutron stars gravitation would be subject to evaporation would it actually take the same amount of force as supplied by the neutron star's gravitation to prevent this evaporation?
     
    Last edited by a moderator: Aug 5, 2005
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