Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Andy Leonard on 16/11/2008 10:39:49
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Andy Leonard asked the Naked Scientists:
Chris,
Firstly let me say that I am fairly new to listening to your podcast (http://www.thenakedscientists.com/HTML/podcasts/), and
subscribed to it after remembering hearing on you Dr Karl's Science Q&A
show on Triple J in Australia (Where I live).
I completely enjoy listening to your podcast (http://www.thenakedscientists.com/HTML/podcasts/).
I have been thinking some time about bullets and how they work, and decided to write in and ask you the question:
Do guns (or a bullet) need to be in an oxygen rich environment (i.e. in air) to work? Would a gun fire in a vacuum, underwater or other gas (without oxygen) such as Nitrogen etc?
Regards,
Andy Leonard
Adelaide, Australia
What do you think?
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The oxygen used in the combustion of the gunpowder is sealed in the shell along with the gunpowder.
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Close.
The oxygen used is already present in the gunpowder, but as compounds like potassium nitrate which decomposes to give oxygen on heating. For more modern propellants it is present as componds like cellulose nitrate or glyceryl trinitrate.
In any event they would work in a vacuum, but I wouldn't like to try firing a gun underwater. I don't know if the water in the barrel wiould effectively jam the gun.
Anyone out there know if guns work underwater?
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I sit corrected.
There's a few youtube videos of guns being fired underwater, here's one
It works, but the bullet doesn't seem to go far.
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Of course it doesn't go far. Water is a lot more dense than air so it disperses the Kinetic Energy much quicker.
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I know this is an old post, but recently this very question "Do guns work in space" came up between myself and a group of friends down the pub.
I strongly argued against the possibility on the grounds that chemical reactions are pressure dependent, and in a vacum there is no atmospheric pressure.
The science so to say, the greater the atmospheric pressure the bigger the bang, the lesser the pressure the weaker the reaction, down to the point where the reaction will simply fail to occure.
My point, bullets arn't pressurised containers, so in a vacum they won't work.
Was I horribly, horribly wrong on this point?
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I know this is an old post, but recently this very question "Do guns work in space" came up between myself and a group of friends down the pub.
I strongly argued against the possibility on the grounds that chemical reactions are pressure dependent, and in a vacum there is no atmospheric pressure.
The science so to say, the greater the atmospheric pressure the bigger the bang, the lesser the pressure the weaker the reaction, down to the point where the reaction will simply fail to occure.
My point, bullets arn't pressurised containers, so in a vacum they won't work.
Was I horribly, horribly wrong on this point?
Quite. [:)]
If they weren't 'pressurized', the very high pressures reached in the combustion would destroy the gun; atmospheric pressure is negligible, in comparison.
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If they weren't 'pressurized', the very high pressures reached in the combustion would destroy the gun; atmospheric pressure is negligible, in comparison.
Sorry I don't think I made myself clear. When I said bullets arn't pressurised containers what I meant was that the propellant would be exposed to the vacum.
Obviously a firearm is capable of withstanding the pressure of the explosion within its barrel when fired within a pressure of 1 atmosphere. Pressure inside the weapon only becomes a safety issue when the atmospheric pressure the weapon is being used in is increased, for example underwater.
My argument runs that as atmospheric pressure decreases, the power of the explosion within the bullet decreases with it, to the point that in a vacum, the absence of atmospheric pressure will totally inhibit the explosive reaction need for the bullet to be fired from the gun.
It should probably be stated at this point that we were talking about real, commercially available firearms, not hypothetical ones. I firmly believe it would be possible to engineer solutions to all of the problems associated with firing a gun in space, it's just no-ones gone on record as having done it yet. Probably because there's no commercially viable reason to do so.
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If they weren't 'pressurized', the very high pressures reached in the combustion would destroy the gun; atmospheric pressure is negligible, in comparison.
Sorry I don't think I made myself clear. When I said bullets arn't pressurised containers what I meant was that the propellant would be exposed to the vacum.
And which is the problem since most of propellants are solid?
My argument runs that as atmospheric pressure decreases, the power of the explosion within the bullet decreases with it, to the point that in a vacuum, the absence of atmospheric pressure will totally inhibit the explosive reaction needed for the bullet to be fired from the gun.
Sorry but it's a nonsense. The explosive reaction would be (almost exactly) the same, in the void. (Conventional) firearms would work in the same way (or better) in the void.