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Posted: 6/21/2011 4:33:06 AM EDT
The greatest movie guns thread elsewhere in GD got me thinking about Vera...



Now, in the scene where Jayne shoots at the control room of the scrapper station, they put Vera in a suit, and are able to fire the weapon. My question is this: Can anyone comment on what would happen in reality if a firearm was fired in a hard vacuum, similar to what would have existed almost immediately after the first round broke the suit's faceplate?

Not to speak of the difficulty of firing from a moving platform, I'm a zero-g, zero-drag environment with sights or optics that are designed to compensate for bullet drop. I'm just asking about internal ballistics, and maybe the first few feet past that.

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Link Posted: 6/21/2011 4:43:47 AM EDT
It would fire like it does here on earth, except in space it would go on till it hit something or got pulled into something with a major gravity field.
Link Posted: 6/21/2011 4:45:22 AM EDT



Originally Posted By Shockergd:


It would fire like it does here on earth, except in space it would go on till it hit something or got pulled into something with a major gravity field.


what he said....
 
Link Posted: 6/21/2011 4:49:28 AM EDT
Exactly. Bullet drop would be very different than we know it.
Link Posted: 6/21/2011 4:49:31 AM EDT
[Last Edit: 6/21/2011 4:50:48 AM EDT by Chris_1522]
Link Posted: 6/21/2011 4:51:11 AM EDT
Bullet drop would be measured in AUs


Link Posted: 6/21/2011 4:54:19 AM EDT
could you imagine calculating multiple gravity fields in a long range shot?
Link Posted: 6/21/2011 4:54:56 AM EDT
Assuming Vera uses ammunition with propellant similar to what we use in reality at the present time, the gun would have no problem being fired in a vacuum.
Link Posted: 6/21/2011 4:55:13 AM EDT
[Last Edit: 6/21/2011 4:56:13 AM EDT by -Duke-Nukem-]
In fact, they don't even need to put Vera in the spacesuit. Part of the chemical wonder of smokeless gunpowder is that the chemical mix oxygenates itself. This is why you can seat bullets to "crush depth" in cases, where there is very little air left in the case and the bullet is smooshed right against the powder, and the round's ballistics will depend on the amount of powder and the rate of burn of that powder, NOT the amount of air in the casing. Also, you aren't burning air in the barrel as propellant because the bullet is pushing against that air to move forward. Air in the barrel actually decreases velocity, so in a vacuum you would have a (very small) velocity gain.
Link Posted: 6/21/2011 4:56:25 AM EDT
[Last Edit: 6/21/2011 4:57:44 AM EDT by rcb1586]
Would it even fire?

If it were a true vacuum then there would be no oxygen present. Doesn't the powder require oxygen to ignite?

The whole operation of a firearm is based on the expanding gases within the barrel. How is a bullet propelled in the absence of any gases?


ETA: OK, I guess the above post answers this. Never knew that.
Link Posted: 6/21/2011 5:00:25 AM EDT
Originally Posted By rcb1586:
Would it even fire?

If it were a true vacuum then there would be no oxygen present. Doesn't the powder require oxygen to ignite?

The whole operation of a firearm is based on the expanding gases within the barrel. How is a bullet propelled in the absence of any gases?


ETA: OK, I guess the above post answers this. Never knew that.


It would certainly fire. Military ammunition is sealed to prevent water from contaminating the powder. There is no air besides what was sealed into the cartridge when it was loaded. Non military ammunition also has a pretty tight seal. There are plenty of youtube videos of it fired underwater.
Link Posted: 6/21/2011 5:00:59 AM EDT
Originally Posted By -Duke-Nukem-:
In fact, they don't even need to put Vera in the spacesuit.


Yep. There's even an interview where Whedon says their firearms "advisor" screwed the pooch in thinking they needed the suit. By the time they realized the advisor was wrong, it was too late.

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Link Posted: 6/21/2011 5:06:50 AM EDT
They put Vera in the space suit because, in Whedon's 'Verse, guns work a little bit differently, by principles that are never explained.

It's simply artistic license, the same way Zoe or Mal cocking their firearms produces a capacitor charging sound.

They're also understood to be cartridge weapons, but have you noticed that very few of the weapons actually ejects a spent shell?  they're caseless, for the most part, and they use two or more sources of propellant energy.

Notice how after Mal cocks his pistol once at the begining of the fight, it never falls forward even after being fired?  His 'hammer' simply acts like a safety or charging/priming device, like a switch to turn a camera on.
Link Posted: 6/21/2011 5:09:42 AM EDT
The trouble would be in keeping the bullet in the case before it was fired.  The case would have atmospheric pressure in it, bullet might need to be crimped in.
Link Posted: 6/21/2011 5:13:48 AM EDT



Originally Posted By dirtyboy:


The trouble would be in keeping the bullet in the case before it was fired.  The case would have atmospheric pressure in it, bullet might need to be crimped in.


This.





Im thinking the bullets would pop out of the cases when exposed to a vacuum.





.



 
Link Posted: 6/21/2011 5:15:33 AM EDT
For every action, an equal and opposite reaction.....
Link Posted: 6/21/2011 5:18:07 AM EDT
What is a "hard vacuum"?  Dyson?  A vacuum is a vacuum or it isn't.



Doesn't the powder need oxygen to burn?
Link Posted: 6/21/2011 5:20:08 AM EDT
Link Posted: 6/21/2011 5:20:58 AM EDT
Link Posted: 6/21/2011 5:24:11 AM EDT
Link Posted: 6/21/2011 5:26:55 AM EDT
Is the vacuum on a treadmill?

Are there magnets involved?

Is there gonna be a simple math problem?

These things matter people!
Link Posted: 6/21/2011 5:27:06 AM EDT
[Last Edit: 6/21/2011 5:27:43 AM EDT by MNJack762]
Is the vacuum on a treadmill?

Doh! Beat me to it.
Link Posted: 6/21/2011 5:31:17 AM EDT
[Last Edit: 6/21/2011 5:33:08 AM EDT by VBC]
Originally Posted By AeroE:
Originally Posted By dirtyboy:
The trouble would be in keeping the bullet in the case before it was fired.  The case would have atmospheric pressure in it, bullet might need to be crimped in.


How about calculating the force, instead of speculating?

The projected area of a 0.308 inch diameter bullet is 0.075 in^2.  Standard sea level pressure is 14.7 pounds-force per in^2.

The axial force is 0.075(14.7) = 1.1 pounds.



Boom head shot.


Might want to increase the crimp a little.

As far as ballistics, that would be easy.  It would fire straight, like a laser.  Unlimited range, though you might get some small deviations due to gravitation from other objects in space.  Plus the sound is already suppressed due to the vacuum.  Guns were made for outer space.
Link Posted: 6/21/2011 5:32:12 AM EDT
Originally Posted By TrojanMan:
They put Vera in the space suit because, in Whedon's 'Verse, guns work a little bit differently, by principles that are never explained.


Whedon's a libtard. When was the last time you met a libtard that understood how guns work?

Link Posted: 6/21/2011 5:36:57 AM EDT
Originally Posted By sigp226:
Originally Posted By rcb1586:
Would it even fire?

If it were a true vacuum then there would be no oxygen present. Doesn't the powder require oxygen to ignite?

The whole operation of a firearm is based on the expanding gases within the barrel. How is a bullet propelled in the absence of any gases?


ETA: OK, I guess the above post answers this. Never knew that.


It would certainly fire. Military ammunition is sealed to prevent water from contaminating the powder. There is no air besides what was sealed into the cartridge when it was loaded. Non military ammunition also has a pretty tight seal. There are plenty of youtube videos of it fired underwater.


It would fire, but this is not why.

Potassium nitrate acts as the oxidizer in black powder.
Smokeless powders use nitrocellulose, which reacts without external oxygen.
Link Posted: 6/21/2011 5:37:27 AM EDT
Link Posted: 6/21/2011 5:37:30 AM EDT


Considering that the self-contained metallic cartridge contains the propellant and oxidizer the gun is going to fire. The problem with shooting a gun in a hard vacuum is that it will eventually over heat(no air to transfer heat) and jam up because normal lubricants will boil off.

Link Posted: 6/21/2011 5:39:07 AM EDT
[Last Edit: 6/21/2011 5:45:01 AM EDT by Greenhorn]
If gunpowder used atmospheric air to burn, we could just use flour for gunpowder.  The special thing about nitrocellulose-based gunpowder is that it is an unstable molecule that reacts with itself when disturbed and releases gasses.  It doesn't need anything from the outside.  I'm always surprised that some people sometimes think that gunpowder needs atmospheric oxygen.  That doesn't make any sense.

Unless a bullet were loose in the shell, it would not pop out.  Even a .50 round, with a base area of about 0.2 square inches, would only have about 3 pounds of pressure pressing on it in a vacuum.  Have you ever tried to pull a bullet out of its casing?  It takes a LOT more than 3 pounds of pull.

Unless you had a water-cooled weapon, you would have a severe overheating problem.  Most firearms are air-cooled, meaning air runs past the hot areas, absorbs some heat, and then flows away, letting some cool air replace it and absorb some heat, etc.  It's slow since air has a low heat capacity (dunking it in water would be almost instantaneous since water has a high heat capacity), but it works.  In a vacuum, the only way for the firearm to lose heat is by radiation, which is slow.  The heat loss rate by radiation is directly proportional to its temperature.  The hotter something is, the faster it loses heat, exponentially.  At regular firearm temperatures (a few hundred degrees), the heat loss is rather slow.  It would have to be VERY hot to reach equilibrium with the heat gain from rapid firing.  It would quickly turn red hot.
Link Posted: 6/21/2011 5:44:45 AM EDT
Originally Posted By Skibane:
Originally Posted By TrojanMan:
They put Vera in the space suit because, in Whedon's 'Verse, guns work a little bit differently, by principles that are never explained.


Whedon's a libtard. When was the last time you met a libtard that understood how guns work?



Whedon's an artist, who is independently creative but has enough grey matter to understand that he also needs to work with other people.  Spielberg turned into an idiot once he decided he could do everything himself.  To Whedon's credit, he worked with a lot of people who had a lot of good input on the Firefly series.  It contains some of the best acting, writing, and special effects that has ever been seen on network TV.

I don't know about his politics, but I do know that Whedon makes good art.  You're free not to like it, if you choose.


And I also know that how guns work is irrelevant in art.  A shotgun blast will not send someone flying across the room, but it looks neat in movies sometimes.
Link Posted: 6/21/2011 5:45:35 AM EDT
Originally Posted By MNJack762:
Is the vacuum on a treadmill?

Doh! Beat me to it.


Wow ... Arfcom disappoints me .... Seriously folks? Smokeless powder makes it's own o2 to burn, bullets popping out of the case? Off the top of my head, < 2psi of force pressing against the projectile ... Bullet drop ? ... In a vacuum? Wtf it's basic physics here folks .... It keeps going at the velocity it left the barrel at ( friction slows it in the barrel)  until acted upon by an outside force, such as gravity ...and the poor girl, well the bullet goes forward, which means she goes backwards ..... Geeeesh

Posted Via AR15.Com Mobile
Link Posted: 6/21/2011 5:45:37 AM EDT
Originally Posted By Eric802:
Originally Posted By VBC:
Originally Posted By AeroE:
Originally Posted By dirtyboy:
The trouble would be in keeping the bullet in the case before it was fired.  The case would have atmospheric pressure in it, bullet might need to be crimped in.


How about calculating the force, instead of speculating?

The projected area of a 0.308 inch diameter bullet is 0.075 in^2.  Standard sea level pressure is 14.7 pounds-force per in^2.

The axial force is 0.075(14.7) = 1.1 pounds.



Boom head shot.


Might want to increase the crimp a little.


No, I think he's saying there's no way in hell the bullet would "pop" from the casing.  I think anyone who reloads would know that without doing the math.  I can reload .223 with no crimp and I can't push the bullet farther into the casing by pressing the tip against a tabletop, I really doubt they'd just "pop" out.


That's because of neck tension in the case.

I merely said add enough crimp to replicate the missing 1.1 lbs from atm, as a joke.
Link Posted: 6/21/2011 5:46:38 AM EDT
No problem with shooting in a vacuum.   The Soviets did this in the mid 70's...Using a 23mm or 30mm aircraft cannon hardmounted to their Salyut-3 space station.
http://en.wikipedia.org/wiki/Salyut_3

55_grain
Link Posted: 6/21/2011 5:48:30 AM EDT
I just came in because this thread was appropriate to check out my new avatar
Link Posted: 6/21/2011 5:49:57 AM EDT
[Last Edit: 6/21/2011 5:56:13 AM EDT by sleepdr]
Originally Posted By RaisedByWolves:

Originally Posted By dirtyboy:
The trouble would be in keeping the bullet in the case before it was fired.  The case would have atmospheric pressure in it, bullet might need to be crimped in.

This.


Im thinking the bullets would pop out of the cases when exposed to a vacuum.


.
 

I would think it takes far more than 14.7psi to unseat a bullet. Chamber pressure of even handgun rounds is in the tens of thousands. It would be interesting to check an inert round in a vacuum chamber. An uncrimped primer maye even pop out before a bullet.

A vacuum is after all only 0psi (or approaching that). Stuff gets sucked out of other stuff by pressure differential, not by some vacuum demon. We design firearms & cartridges for a much higher deltaP.

ETA: I typed too slowly. Already covered by several posters.

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Link Posted: 6/21/2011 5:51:13 AM EDT
Originally Posted By Greenhorn:
If gunpowder used atmospheric air to burn, we could just use flour for gunpowder.  The special thing about nitrocellulose-based gunpowder is that it is an unstable molecule that reacts with itself when disturbed and releases gasses.  It doesn't need anything from the outside.  I'm always surprised that some people sometimes think that gunpowder needs atmospheric oxygen.  That doesn't make any sense.

Unless a bullet were loose in the shell, it would not pop out.  Even a .50 round, with a base area of about 0.2 square inches, would only have about 3 pounds of pressure pressing on it in a vacuum.  Have you ever tried to pull a bullet out of its casing?  It takes a LOT more than 3 pounds of pull.

Unless you had a water-cooled weapon, you would have a severe overheating problem.  Most firearms are air-cooled, meaning air runs past the hot areas, absorbs some heat, and then flows away, letting some cool air replace it and absorb some heat, etc.  It's slow since air has a low heat capacity (dunking it in water would be almost instantaneous since water has a high heat capacity), but it works.  In a vacuum, the only way for the firearm to lose heat is by radiation, which is slow.  The heat loss rate by radiation is directly proportional to its temperature.  The hotter something is, the faster it loses heat, exponentially.  At regular firearm temperatures (a few hundred degrees), the heat loss is rather slow.  It would have to be VERY hot to reach equilibrium with the heat gain from rapid firing.  It would quickly turn red hot.


Interestingly, flour can be explosive when finely sifted and suspend in the air (e.g. enough atmospheric oxygen is present to allow a quick burn), silo explosions are not unheard of.
Link Posted: 6/21/2011 5:52:47 AM EDT
[Last Edit: 6/21/2011 5:53:33 AM EDT by Greenhorn]
Originally Posted By Lacoochee:
Originally Posted By Greenhorn:
If gunpowder used atmospheric air to burn, we could just use flour for gunpowder.  The special thing about nitrocellulose-based gunpowder is that it is an unstable molecule that reacts with itself when disturbed and releases gasses.  It doesn't need anything from the outside.  I'm always surprised that some people sometimes think that gunpowder needs atmospheric oxygen.  That doesn't make any sense.

Unless a bullet were loose in the shell, it would not pop out.  Even a .50 round, with a base area of about 0.2 square inches, would only have about 3 pounds of pressure pressing on it in a vacuum.  Have you ever tried to pull a bullet out of its casing?  It takes a LOT more than 3 pounds of pull.

Unless you had a water-cooled weapon, you would have a severe overheating problem.  Most firearms are air-cooled, meaning air runs past the hot areas, absorbs some heat, and then flows away, letting some cool air replace it and absorb some heat, etc.  It's slow since air has a low heat capacity (dunking it in water would be almost instantaneous since water has a high heat capacity), but it works.  In a vacuum, the only way for the firearm to lose heat is by radiation, which is slow.  The heat loss rate by radiation is directly proportional to its temperature.  The hotter something is, the faster it loses heat, exponentially.  At regular firearm temperatures (a few hundred degrees), the heat loss is rather slow.  It would have to be VERY hot to reach equilibrium with the heat gain from rapid firing.  It would quickly turn red hot.


Interestingly, flour can be explosive when finely sifted and suspend in the air (e.g. enough atmospheric oxygen is present to allow a quick burn), silo explosions are not unheard of.


Yes, I'm referring to flour packed into a cartridge, because others are insinuating that the tiny amount of oxygen in a cartridge is enough to burn up the fuel.
Link Posted: 6/21/2011 5:58:46 AM EDT
it doesn't matter really, since that's a mini 14 he'll miss whatever he's shooting at
Link Posted: 6/21/2011 5:58:50 AM EDT
[Last Edit: 6/21/2011 6:14:42 AM EDT by EastcARstle]

Originally Posted By DragoMuseveni:
Considering that the self-contained metallic cartridge contains the propellant and oxidizer the gun is going to fire. The problem with shooting a gun in a hard vacuum is that it will eventually over heat(no air to transfer heat) and jam up because normal lubricants will boil off.

















Ding ding we have a winnah 8-)
Getting rid of heat is always a major concern in space systems engineering, and vacuum tribology is more of an art than a science. But there shouldn't be any issues with firing one round, especially if it is already chambered and the firing mechanisms (and their tolerances) are similar to what is on current weapons.
BTW, the Russians have some experience with that kind of stuff





http://www.fourmilab.ch/documents/spaceguns/




"Salyut 3 had a machine gun.  The station had a 23
mm rapid-fire cannon mounted on the outside, along the long axis
of the station "for defence against US space-based
inspectors/interceptors”.  Combat engagements would have been
leisurely by <cite>Star Wars</cite> or fighter jet standards, since the only
way to aim the cannon was to point the entire station at the
target, using its attitude gyros.  A periscope connected to a
visor on the main control panel allowed drawing a bead on the
intended target."










And there's always a gun that's kept in the Soyuz spacecraft that is attached to the Russian part of the International Space Station





http://www.jamesoberg.com/russiangun_tec.html




"The triple-barreled gun can fire flares, shotgun shells, or rifle bullets,
           depending on how it's loaded. The gun and about 10 rounds for each barrel
           are carried in a triangle-shaped survival canister stowed next to the
           commander's couch. The gun's shoulder stock opens up into a machete for
           chopping firewood."







Soyuz survival gun and accessories




 
 
 

 
Link Posted: 6/21/2011 6:00:49 AM EDT
Originally Posted By rcb1586:
Would it even fire?

If it were a true vacuum then there would be no oxygen present. Doesn't the powder require oxygen to ignite?

The whole operation of a firearm is based on the expanding gases within the barrel. How is a bullet propelled in the absence of any gases?


ETA: OK, I guess the above post answers this. Never knew that.


The oxidizers needed are part of the powder blend.
Link Posted: 6/21/2011 6:19:58 AM EDT
And you would not need hearing protection!
Link Posted: 6/21/2011 6:28:09 AM EDT
Originally Posted By Fourays2:
it doesn't matter really, since that's a mini 14 he'll miss whatever he's shooting at


It's a Saiga 12ga.  If you care.

And yes, the actual prop is a functional firearm, it's just dressed up.

Shotguns are actually very easy to make stage flash rounds for, and it looks really neat on screen.  All the gunshots are foley'd in afterwards anyhow.
Link Posted: 6/21/2011 6:31:20 AM EDT
Originally Posted By Fourays2:
it doesn't matter really, since that's a mini 14 he'll miss whatever he's shooting at


Vera is a Saiga 12.
Link Posted: 6/21/2011 6:44:23 AM EDT
Gunpowder is self oxidizing so a gun would fire in space just as good as it would here on earth except with better velocity.
Link Posted: 6/21/2011 6:46:47 AM EDT
Originally Posted By outofstep:
Originally Posted By Fourays2:
it doesn't matter really, since that's a mini 14 he'll miss whatever he's shooting at


Vera is a Saiga 12.


That's what I thought.
Link Posted: 6/21/2011 6:51:53 AM EDT
[Last Edit: 6/21/2011 6:52:13 AM EDT by Greenhorn]
Originally Posted By motoguzzi:
And you would not need hearing protection!


You might.  The firearm would still produce a pressure wave from the escaping gasses.
Link Posted: 6/21/2011 6:53:09 AM EDT



Originally Posted By RABIDFOX50:



Originally Posted By outofstep:

Vera is a Saiga 12.
That's what I thought.

Yup.







 
Link Posted: 6/21/2011 6:54:20 AM EDT



Originally Posted By Greenhorn:



Originally Posted By motoguzzi:

And you would not need hearing protection!
You might.  The firearm would still produce a pressure wave from the escaping gasses.
I think being in a vacuum, a human would probably want to be in a space suit. I expect that would be protection enough.





 
Link Posted: 6/21/2011 6:55:41 AM EDT
Originally Posted By Greenhorn:
Originally Posted By motoguzzi:
And you would not need hearing protection!


You might.  The firearm would still produce a pressure wave from the escaping gasses.


The gas would be so dispersed by the time it got to your suit that it wouldn't do anything but roll right over it.
Link Posted: 6/21/2011 7:01:50 AM EDT
Originally Posted By RABIDFOX50:
Originally Posted By outofstep:
Originally Posted By Fourays2:
it doesn't matter really, since that's a mini 14 he'll miss whatever he's shooting at


Vera is a Saiga 12.


That's what I thought.


It's a slightly dressed up version of the rifles used in Showtime with Eddie Murphy and Robert DeNiro
Link Posted: 6/21/2011 7:11:05 AM EDT
Originally Posted By TrojanMan:
Originally Posted By Greenhorn:
Originally Posted By motoguzzi:
And you would not need hearing protection!


You might.  The firearm would still produce a pressure wave from the escaping gasses.


The gas would be so dispersed by the time it got to your suit that it wouldn't do anything but roll right over it.


I'm saying if the person were not in a suit.  They'd definitely hear it.  Remember, there is no atmospheric pressure to contain the gasses.  It will expand at supersonic speed.  It's not like on Earth where the gasses form a cloud of smoke around the firearm.

For a visual representation of this, watch a video of a rocket taking off.  Near the ground the exhaust forms a distinct tail.  This is because the atmospheric pressure is containing the gasses - they only expand enough to match the surrounding pressure, and then they just hang.  In space there is no such confinement.  Watch a video of a rocket that is 20 miles high.  The exhaust will actually travel UP the body of the rocket!  It will also come out in a wide fan.

Compare the beginning of the launch in the following video to around  2:30.

http://www.youtube.com/watch?v=XKtH0uzg8wU
Link Posted: 6/21/2011 7:13:17 AM EDT
In outer space,  you could zero at 10 yards, and have range out to Pluto.
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