Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Two questions i had a long time ago

  1. May 27, 2005 #1
    one day i was playing halo2, and wondering how accurate the physics are, i came up with two questions

    1) if i have an ordinary bullet gun, and i try to fire it in space, will it work? i asked this to my tutor and he said it would only fire with limited force, because the only air is that which is trapped in the bullet's and gun, but he is a chem' teacher so i just wanted to check...

    2) if i fire a ball of plasma in to ordinary window glass, what will happen, will it melt the glass?
     
  2. jcsd
  3. May 27, 2005 #2

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    All of the oxygen required for combustion in the bullet casing is contained in the chemicals within the gunpowder. No "air" is required. Anyway, whatever air might be "trapped" in the barrel of the gun would be pushed out in front fo the bullet.

    I suppose an old "flint-lock" gun would not work, but modern bullets would work just the same in space.

    As for the plasma ball melting glass: it could. IT depends how much plasma you got and how thick the glass is. Even though plasma would be on the order of thousands of degrees, the amount of matter at this temperature is relatively small, so there is not all that much heat. Since we're talking about science fiction here we could say that it is "not impossible."
     
  4. May 27, 2005 #3
    thanks,
    how about with a hand grenade?

    also, if a particle or vacuum has no sign's of avtivity, can you say that within that area there is no time, or that time is inactive?
     
  5. May 27, 2005 #4

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    Same thing. In the case of all chemical explosives, there is not enough time for the oxygen in the air to get to the combustable materials. Therefore, all the oxygen has to be part of the chemical makeup of the explosive material. This is why, for a grim example, Tim McVeigh needed so much fertilizer to make his truck bomb; the fertilizer was the oxygen supply for the explosion.


    That's philosophical. Someone else can take it.
     
  6. May 27, 2005 #5

    LURCH

    User Avatar
    Science Advisor

    Yes, if you fire a hand grenade through a window, it will break the glass :biggrin: .
     
  7. May 27, 2005 #6

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    Dang, I misunderstood the question! :uhh:
     
  8. May 27, 2005 #7

    Danger

    User Avatar
    Gold Member

    Unless it's a plasma grenade, in which case it will melt its way through. :tongue:

    The gunpowder in a flintlock still contains the oxydizer, so I think the relevant factor would be whether or not the spark from the flint is hot enough in space to initiate the reaction. Since it's essentially in contact with the priming powder, I don't think that it would cool much before taking effect. (Keeping the priming powder in the pan under zero-g is another matter.)
    I seem to recall that there's a condition called 'vacuum lock' that can befall any metallic mechanism in space, though. I don't know whether it's due to Van derWaals forces being more effective without air or what, but sometimes the parts can stick to each other enough to impair movement. I'd like some input about that from an expert if possible (Astronuc?) You'd also have to be careful about how the gun is prepared. Most lubricants, for instance, would gel or freeze in space. On the whole, if I had to choose a weapon for space combat, I'd take a Vulcan cannon any day.
     
  9. May 27, 2005 #8

    SGT

    User Avatar

    The burning of the chemical propellant in the gun or the detonation of the high explosive in the hand grenade are highly dependent of the ambient temperature. I don't know if at nearly 0 degrees Kelvin the chemical reactions would happen.
     
  10. May 27, 2005 #9

    Danger

    User Avatar
    Gold Member

    Good point. I've seen a lot about how firearms would be the best weapons for space combat, but this has never been addressed. I know even less about chemistry than I do about physics, so now you've got me worried.
     
  11. May 27, 2005 #10

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    Probably not if T was near 0 K , but a hand grenade or gun floating around space near Earth-orbit would be kept well above this temperature due to the sunlight constantly hitting it. I guess the lesson here is, don't keep it in your holster too long.
     
  12. May 28, 2005 #11

    Mk

    User Avatar

    I think a halo plasma grenade would break through the glass, not melt through it. Besides, doesn't the plasma grenade explode then, spew plasma everywhere, its not a ball of plasma. The exterior surfaces of the grenade are slightly higher than room temperture, and turn sticky after thrown by a SPARTAN/Covenent troop.
     
  13. May 28, 2005 #12
    in the game it just falls off, something to do with the sticking mechanism i would think, it thinks it's a wall and bounces back
     
  14. May 28, 2005 #13

    Danger

    User Avatar
    Gold Member

    Ooops... I forgot that this was about a (game? I've heard of HALO, but don't know what it is other than a type of paratrooper tactic.)
     
  15. May 29, 2005 #14

    SGT

    User Avatar

    The OP did not mention that the gun or the grenade should be near the Sun or any other star. In deep space the temperature must be very near 0 K.
    Even in near Earth-orbit, I doubt that the temperature would be very high. A gun or grenade have a very small area, so they must collect very little solar energy and this is radiated again into space.
    I don't know how to calculate the temperature of a black body this size. Can anyone more knowledgeable help?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?