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A question or two for all you smart types

  1. Jul 11, 2006 #1

    Nux

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    I am not a scientific type, im quite the opposite. However I need to have your views on a topic that has come to light through my writing. I write contemporary fantasy and dabble in sci-fi. In the latter genre I have used a concept. It is as follows.

    I have used a material which is formed of a gas that with the correct electrical current solidifies.....so far so good you might say.

    However, the properties of the solidified material is to return any pressure applied to it, in equal amounts. Example being A sheet of Anti Kenetic Polymer (as I have called it) is hit with a bullet. The force of the bullets impact is repelled with exactly the same amount of force applied to the material, creating a null effect, leaving the material uneffected by the impact. In physics i think this is called equilibrium, though it might fall into the dynamic equilibrium catagory.
    The questions is this....

    Is such a material and its reactive properties theoretically possible?

    Also

    If such a material was created would it conflict with Newtons laws?


    On a fantastical note, if such a material was created it would I my belief change human progress entirely. Bullet proof really becomes bullet proof.....the pressure of deep beneath the ocean or the vacuum of space would be meaningless...

    ahh, I know Im a dreamer but Im not the only one!

    please, on a serious note, your views please.
     
  2. jcsd
  3. Jul 11, 2006 #2

    chroot

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    I don't know of any materials which solidify under the passage of electrical current. Such a material wouldn't make any sense, really -- the phase transition from gas to solid is exothermic. It liberates heat energy. The heat would have to go somewhere, and, certainly, passing electrical current through a material does not remove energy.

    The sort of armor you're describing -- which imparts an equal outword force to oppose an incoming force -- is commonly called "active" armor. An example might be using small, controlled explosive charges to deflect an incoming bullet or rocket-propelled grenade.

    On the other hand, "active" armor is not just a plain material. An incoming bullet has a lot of momentum, and momentum is always conserved. The "active" armor is called active because it includes a source of energy, which can be used to accelerate mass in the direction opposite of an incoming munition, cancelling its momentum. There's no way to make a "passive" material, without an energy source, which can simply "push back" on incoming bullets. Such a material would have to be perfectly rigid, completely incapable of deforming. The material you propose would be an idealized rigid material, which does not (cannot) exist.

    And even if you had such a perfectly rigid material, how could you possibly cut it into the right shapes to cover a tank? You'd need some idealized rigid scissors, too, would you not? :wink:

    Alas, I don't mean to be rude -- but I'd say you should work on your knowledge of science before trying to write plausible science fiction.

    - Warren
     
  4. Jul 11, 2006 #3

    Gokul43201

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    The former idea - converting a fluid to a "solid" - is in theory not impossible (note the quotes). This would not be the conventional phase transition (described by chroot, above) where all interactomic spacings are drastically reduced. However, you can create networks (usually chains) with enough atoms that are at close proximity so as to impart a much higher shear strength to the material. This, in short, is how electro- and magneto-rheological fluids work. However, I know of no ER/MR fluid that starts off as a gas - but that's where the "fi" could come in.

    As for the latter bit, your description of what happens is unphysical and uses a terminology that makes no physics sense. But simply put, for the armor to be undeformed by the bullet, you must have a material with an incredibly high elastic limit. This however, does not prevent recoil of the armor (as explained by chroot) - it only prevents deformation. Recoil, however, can be reduced by increasing mass.
     
    Last edited: Jul 11, 2006
  5. Jul 12, 2006 #4
    I don't think any such material is physically possible, Nux. But maybe there's some way to achieve the same result via some kind of higher-dimensional spacewarp. The allegorical "Flatlander" can be lifted off his two-dimensional world, flipped over, and returned. He'd then mysteriously find himself a mirror-image of his former self. Taking that up a dimension, a man might reappear with his heart on the wrong side. Maybe there's a way to contrive this sort of flipover for an oncoming bullet.
     
  6. Jul 12, 2006 #5

    DaveC426913

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    Giving the material a power source would go a long way towards plausibility. In Larry Niven's universe, his characters wear a type of clothing that goes rigid when something impacts it. But it uses a power source.

    That is not to say a material of the type you describe is completely implausible, but let me modify it a bit:

    1]
    Consider your two examples: If the material actually expelled the bullet with the same force it came in at (as opposed to simply stopping its momentum), what would that do in the example of the deep sea diving bell? It would shove the ocean away with the same pressure? Not simply halt the ocean, no, it would actively push it away with a hundred atmospheres of pressure. What would happen then? Would there be an ever-expanding shell of vacuum around the diving bell?

    No, the best the material should be able to do is act as if it were perfectly rigid.


    2]
    Say you have a bullet-proof vest made of the material, a pound or two. How does the material act to stop the bullet? Well, by spreading the momentum through its structure and diffusing it. Makes sense, right? Call it a sort of "kinetic energy superconductor" - it ensures that any energy impacting on it is instantly distributed throughout its volume, (like how water is heated - no part of it will boil until all of it reaches boiling temp.).

    Now, if you build a diving bell out of it, the force is on every surface of the material at the same time. There is nowhere for it to get its extra resilience from, since every part of the material is "under attack".

    What this means is that uniform pressure is the material's weakness. you may not be able to shoot him, but you can overwhelm the material's resilience with uniform pressure. (I can see the climax of a story where the otherwise indestructible, unstoppable villain finds himself in an airlock, and the pressure is cranked up and his suit has no way to distribute the pressure! He ultimately is crushed to death.)

    Now, come to think of it, it is still a great material to make diving bells and pressure suits out of - because it is immune to failure. You will never have a weak point where one part of the material is under great enough stress to leak, since the material will distribute this stress uniformly. Which explains why his indestructible spacesuit is made out of the material in the first place.
     
  7. Jul 12, 2006 #6
    Yes, i think the energy required for such a system is in the order of infinite magnitude wouldnt it?

    If the energy was to be instantly dissipated about the material, the material would either need to increase its temperature or emit that energy as radiation, and the duration of transitions required are finite, therefor the actual dissipation itself cannot be instantaneous [1]. As far as i know, even the shortest transitions in atomic energy levels are finite. But i dont know much about this, just an opinion.

    The last part sounds alot like diamond and other hard materials.
     
  8. Jul 12, 2006 #7

    Gokul43201

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    I wouldn't use water as an example - it is very easy to achieve localized boiling in water with an immersion heater and a variac. With a high specific heat and low thermal conductivity (hence very large thermal time constant), water is much more capable of sustaining large thermal gradients than most other materials (ie: it is very poor at distributing heat quickly unless stirred or agitated in some way).
     
    Last edited: Jul 12, 2006
  9. Jul 14, 2006 #8

    DaveC426913

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    Perhaps not a rigorous example, no. But as a layperson's analogy, I think it makes its point.

    Water is a good conductor, and will conduct the heat away and distribute it more evenly, reducing local boiling. (Or burning, which is why a water bath will prevent foods from burning. As long as there is still water present, the food temp. will not rise above 100C).

    Compare to a vest that "conducts" kinetic energy away until it is distributed evenly, greatly reducing concentrated impact force (the kind that ventilates organs).
     
  10. Jul 15, 2006 #9
    This super armour wouldn't be much use in a bomb blast. Or even simpler, falling off a high building.
     
  11. Jul 15, 2006 #10

    LURCH

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    An interesting idea, though.
    Nux, would this be a gas that hovers around the the body (I've already got that part handled, myself), and then becomes solid as a response to the approach of a projectlile? I could see great advantages to that.

    It would provide the wearer with armor more effective than kevlar, with no gaps anywhere, and would be virtually weightless. But you're hoping for a way to elliminate the kenetic energy of the impact, yes? Tricky business, that; needs a violation of equal and opposite reactions. Still, maybe we could approximate it somehow.

    But first let me ask; is this a personal suit of armor, or a wall to hide behind, shield for a spaceship, or what?
     
  12. Jul 17, 2006 #11
    Anybody got any ideas on armour that would protect if you fell off a high building then? Because I don't.

    :smile:




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    SPLAT
     
  13. Jul 17, 2006 #12

    Gokul43201

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    Springs 'n' dampers! What else?
     
  14. Jul 23, 2006 #13

    LURCH

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    Actually, this armor might be very helpfull in that type of situation. If the armor exists as a field of gas particles held in place around the wearer by a magnetic field, then an approaching object (like the ground) impinging on that field might distort it in such a way as to bring all the particles rushing together in front of that object. There, they might form an ionic bond, the strength of which would be dependant upon the magnetic field bringing them together. This could be set so that the particles of this newly-formed solid would fly apart when subjected to energies just short of those which would seriously injure a human being. So the solid barrier forms between the wearer and the ground, but the force of the impact with the ground vaporizes the solid back into a gas. The gas particles, being charged particles propelled by a magnetic field, could respond at a significant fraction of light speed, re-assembling to smash into the ground again and again.

    With each cycle, the force of the imopact would be transferred to the wearer through the magnetic field. But if the "shattering point" of the particles is set at about 20g's or so, (which is quite a jolt, but not enough to kill ya if it lasts only a short while) and the magnetic field extends about 2 meters out from the wearer, then the effect would be like having a 2-meter "crumple zone", or one of those airbags the stunt people use about 6ft deep. In that case, one could survive a fall that would ordinarily be fatal.
     
  15. Jul 24, 2006 #14

    Pythagorean

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    A smart suit (one that has a computer) with a power source (as mentioned) would probably be most digestable to anal sci-fi readers. Most people can accept that our computer chips and power sources will get smaller and smaller as time goes by, so you could easily hand-wave past the part of how super tiny chips and power cells were invented (what proper mix of materials or techniques they required), and have the suit wired every square millimeter with a set of electronic components (based of some sort of nanotech fabric circuit imprinting that allows you to make circuit boards on fabric) such as sensors (to to detect what's going on, probably by light or other particle echoes) and some sort of force employer to repel objects coming towards you with too much energy.

    I don't know how realistic it would be to user laser cooling, in which you use doppler-shifted lasers, tuned a frequency below the target material's frequency (based on the material itself and its speed, I believe) to actually absorb energy off of the object (it's been done with particles, it may be a stretch to do it with bullets.)

    It also depends on what kind of weapons the armor is being hit with. If it's ballistics, then we're on the same page, but if it's laser/plasma weapons, then we'll have different solutions.
     
  16. Aug 12, 2006 #15
    Last edited: Aug 12, 2006
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