Guns in space
ShX
Even if it is somewhat tangential, I thought I'd throw my two cents into this
one (I just got off being a riflery instructor at a summer camp).
> > (From Frank Crary )
> >While gunpowder needs oxygen to burn, modern firearms do not use it. Instead
> >they use something called smokeless powder. I believe this does not need
> >oxygen to burn (I could easily be wrong). In any case, there exist many
> (Peter Cast)
> Sure. Think about it: the cartridge is _sealed_; only the explosion of the
> propellant pushing the bullet out of the case can break the seal. Where
> could the air come from? Clearly, oxygen is not necessary to fire a gun.
> Moreover, even black powder ("gun powder") can't require oxygen to burn:
> oxygen wouldn't be available to the charge in an old-fashioned
> muzzle-loader or cannon, either.
Modern gun powder (smokeless powder) is, I believe, largly nitrocellulose
(basically cotten soaked in nitric acid and processed) so I can see where
there would be plenty of Ox handy for combustion. I agree from the common
sense point of view too (fixed ammunition is sealed as you say). I vaguely
remember someone saying you could fire a gun underwater, wouldn't go very far.
Black powder = 75% K(NO3) + S + C. I doubt the oxygen in the nitrate becomes
unfixed. Black powder rifles were open at least somewhat at the breech
(had to light the powder some how -- percussion cap, flint, etc)
I imagine they got their Ox from the air.
> > . . . On the other hand, the torque from
> >firing the gun from either the shoulder or the hip results in the firer
> >spining rapidly (around 5rpm or 30 deg./sec.) This spin could be avoided
I'd be interested in seeing how you calculated the spin. I have no reason to
question your figures, I'm just curious.
> Probably the optimum weapon in a weightless environment would be the
> lightest, smallest caliber possible--maybe a .22 short. After all, even a
> very small hole in your space suit will be deadly--and range will be
> unlimited.
If you were in orbit, wouldn't the bullet's velocity cause it to occupy a
different orbit? i.e. lower if you fired it against your movement, higher if
you fired it forward? I'm not an expert on orbital physics . . . just a
thought. BTW, even .22's are considered dangerous up to 1.5 miles. Air
resistance stops 'em on earth though, or more likely the ground.
Personnally, I'd think I'd choose a .44 pistol . . . . w/blanks.
I think EVA's today use a nitrogen propellant. Having felt the kick of
something like a 30-06, it's hard for me to believe the propellant produces a
greater force that a firearm potentially could. (Not that NASA will be
visiting Remington anytime soon)
.-----------------------------------------------------------------------------.
{ Peter Kammer {|} Bitnet: 203PETER@STMARYTX }
{ St. Mary's University {|} Internet: 203P...@VAX.STMARYTX.EDU }
{ San Antonio, TX {|} THEnet: SMUCC::203PETER }
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Look around you my friends, for the curse has been fulfilled!
You DO live in interesting times.
Frank Crary
>> > . . . On the other hand, the torque from
>> >firing the gun from either the shoulder or the hip results in the firer
>> >spining rapidly (around 5rpm or 30 deg./sec.) This spin could be avoided
>
>I'd be interested in seeing how you calculated the spin. I have no reason to
>question your figures, I'm just curious.
>
consistant with a 5.56 NATO round, but I have been told that this is closer
to 7.62 NATO.
The total linear momentum is, therefore, 0.0088kg*950m/s = 8.36 kg-m/s
The firer will pick up a similar momentum in the opposite direction, so
(assuming a 75kg man) he will have a velocity of 8.36 kg-m/s / 75kg = 0.11 m/s
or .4 km/hr.
For the spin, I assumed a man could (roughly) be approximated by a 2m long
by .13m radius cylinder. This gives a monent of inertia about the long axis
(e.g. for spins from left to right) of
I = 0.5 M R^2 = 0.5 * 75kg * (0.13m)^2 = 0.63
The angular momentum transfer from the bullet, if fired from the waist (e.g.
so as to spin the firer ONLY along the long axis) would be (in the worst
case):
L = m * v * R = (0.0088kg)*(950m/s)*(0.13m) = 1.087
So the rotation rate would be L/I = 1.725 radians/sec = 16.5 rmp
The moment of inertia of the firer about his minor axis (e.g. spining head over
heels) would be:
I = M*H^2/12 = 6.25
And the angular momentum (If fired from the shoulder, so as to spin the firer
ONLY about this axis, in the worst case), would be
L = m*v*(.6m) = 5.02 (assuming the shoulder is 0.4m below the top of the head)
So the rotation rate would be:
L/I = 0.803 radians/sec = 7.67 rpm.
Since actually firing a rifle would spin the firer about BOTH of these axis in
some combination, the actual rotation rate would be somewhere between these
extremes.
I also assumed the bullet was fired along a line pointing at a right angle to
the firer's center of mass. Of course, if the line of fire went through the
firer's center of mass, there would be no spin .
I am not sure how accurately one could do this, however. I suspect that,
with care, the above spin rates could be reduced by a factor of ten or so.
A ~1 rpm spin would still be a problem...
Frank Crary
Paul M. Karagianis
> Date: Fri, 23 Aug 1991 0:00:23 CDT
> From: 203P...@VAX.STMARYTX.EDU (ShX)
>
> Black powder = 75% K(NO3) + S + C. I doubt the oxygen in the nitrate
> becomes unfixed. Black powder rifles were open at least somewhat at the
> breech (had to light the powder some how -- percussion cap, flint, etc)
> I imagine they got their Ox from the air.
After further thought it occurs to me that the above formula for black
powder probably isn't what is actually used. Let me anecdotally recall
something I remember reading as a kid: back around the 15th (?) century
some cannons were loaded with black powder "cakes" made by mixing some
variation of the above formula into a paste, using the urine of a wine
drinking priest. A priest because they had a bland diet that yielded
a consistent product (I *think* there was something in the large
amounts of cheese that they ate that turned up in the product), and a
wine-drinker for the alcohol. In other words the black powder used
500 years ago had already been enhanced with alcohol and ammonia and
God only knows what else. I'd *assume* that more modern stuff would be
more sophisticated. Maybe this debate is based on the assumption that
ammo is a lot simpler chemically than it really is? -Kary
Gary Coffman
>
> Black powder = 75% K(NO3) + S + C. I doubt the oxygen in the nitrate
> becomes unfixed. Black powder rifles were open at least somewhat at the
> breech (had to light the powder some how -- percussion cap, flint, etc)
> I imagine they got their Ox from the air.
No, KNO3 is a strong oxidizer and supplies the oxygen necessary for the
reaction. Black powder is classified as a primary explosive. A percussion
rifle is sealed by the patched ball from the muzzle end and the small
nipple hole in the breech is sealed by the copper percussion cap. *All*
firearms depend on sealed chambers to build the necessary pressure to propel
the bullet at high velocity out the barrel. None expose the powder to the
atmosphere. Typical modern firearms develop 40,000 CUP (roughly pounds
per square inch) to propel the bullet. *Any* opening other than the muzzle
would result in loss of pressure and loss of function.
KNO3 and sugar make a fine amateur rocket fuel often called carmel candy
fuel. A little too touchy for most amateurs however.
Gary
Paul M. Karagianis
What I wrote in two separate transactions starting...
> Date: Fri, 23 Aug 1991 0:00:23 CDT
>
> Black powder = 75% K(NO3) + S + C. I doubt the oxygen in the nitrate
> becomes unfixed. Black powder rifles were open at least somewhat at the
> breech (had to light the powder some how -- percussion cap, flint, etc)
> I imagine they got their Ox from the air.
The bottom line is that there is (or was) a contingent of readers under
the illusion that guns won't fire in a vacuum because they need ambient
oxygen. They don't, but some counter-arguments have been made on the
basis of the breech *having* to be sealed which they blantantly haven't
been in the past: e.g. (Match, Wheel, Snaphance, Flint)-locks, and, as
the above poster points out, even to an extent in percussion guns.
-Kary
Craig Milo Rogers
>*All*
>firearms depend on sealed chambers to build the necessary pressure to propel
>the bullet at high velocity out the barrel. None expose the powder to the
>atmosphere.
What about matchlocks?
Craig Milo Rogers
Eolid enthusiast
Just like flintlocks, they set off the main charge by lighting a smaller charge
at the head of a touch hole.
--
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The only drawback with morning is that it | Chasing nebulae till 3 am
comes at such an inconvenient time of day. | may explain it, though.
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Gary Coffman
Matchlocks, like flintlocks and other muzzleloaders, have a small opening
at the breech to allow ignition of the charge. This hole is much smaller
than the bore and is covered with the ignition charge, a flashpan or
a percussion cap, prior to firing. During firing, some gas leaks out
the touch hole, but is only a small percentage of the gas flow. The major
gas flow is out the muzzle, pushing the projectile. All of this gas flow
is *outward* from the main charge. There is no inflow from the atmosphere.
Typical numbers are .040 for the touch hole and .500 for the bore.
Gary