Firing in a vacuum

[jimmyraythomason]

Thank you Cosmoline, I'ill take your smartazz comments into consideration.

 

[edrice]

I trust you're not poking "air holes" in the brass and chamber so the powder can "breath"

Exactly. The burn rate is too quick as compared to, say a campfire, that it could't suck enough oxygen out of the air quick enough to support that amount of ignition in such a short period of time. I could just see a machine gunner going dizzy from oxygen starvation...

Look at this on nitrocellulose -

The use of nitrocellulose film for motion pictures led to a widespread requirement for fireproof projection rooms with wall coverings made of asbestos. The US Navy shot a training film for projectionists that included footage of a controlled ignition of a reel of nitrate film, which continued to burn even when fully submerged in water. Unlike many other flammable materials, nitrocellulose does not need the oxygen in the air to keep burning and once it is burning, it is extremely difficult to put out. Immersing burning film in water may not extinguish the fire and it could actually increase the amount of smoke produced.[5] Owing to public safety precautions, the London Underground forbade transport of nitrate films on its system until well past the introduction of safety film.

--from http://en.wikipedia.org/wiki/Nitrocellulose

And regarding flash coming out of the barrel, look at this -

Flashless Powder
Nitrocellulose contains insufficient oxygen to completely oxidize its carbon and hydrogen. The oxygen deficit is increased by addition of graphite and organic stabilizers. Products of combustion within the gun barrel include flammable gasses like hydrogen and carbon monoxide. At high temperature, these flammable gasses will ignite when turbulently mixed with atmospheric oxygen beyond the muzzle of the gun. During night engagements the flash produced by ignition can reveal the location of the gun to enemy forces and cause temporary night-blindness among the gun crew by photo-bleaching visual purple. Flash suppression was attempted by structural modification of the muzzle of small arms. This approach was less successful for artillery, where a flame extending 150 feet (50 meters) from the muzzle might be reflected off clouds and be visible for distances up to 30 miles (50 kilometers).

Flash suppression was achieved by smokeless powder additives. Cooler burning explosives like nitroguanidine or ammonium nitrate were added to reduce the temperature of combustion gasses. Inorganic salts like potassium chloride were added so their specific heat capacity might reduce the temperature of combustion gasses and their finely divided particulate smoke might block visible wavelengths of radiant energy of combustion.

--from http://en.wikipedia.org/wiki/Smokeless_powder

Ed

 

[edrice]

I should think it would be comforting to know that you can placidly leave the confines of earth and still eradicate BGs as equipped and you don't even need a ray gun, much less a light saber.

Ed

 

[Colt Smith]

"I should think it would be comforting to know that you can placidly leave the confines of earth and still eradicate BGs as equipped and you don't even need a ray gun, much less a light saber."


No but you will probably need a permit. Good luck with that.

 

[smoketheresfire]

This has got to be the weirdest thread I've seen in a while. Love it.

 

[Shadow 7D]

Wow, nobody watches old sci-fi anymore, also didn't james bond shoot his pistol in moon raker?

 

[stanmo]

Space men carry 20th century guns. Like in "Firefly" and "Battlestar Galactica".

 

[oldgoat46]

Walking outside in the eye of a hurricane is the closest thing I have ever experienced to being in a vacuum and the sound was amplified ten fold

 

[dogface]

Water is two parts oxygen so a gun's ability to fire under water in no way proves that it will fire in a vacuum. I think the burning rate of powder will be diminished in the absence of oxygen. Just how much can be debated into infinity. Fun to talk about but how many here will ever test your theory?


whoa, have you ever taken a basic chemistry class??

 

[jimmyraythomason]

In what way is being under water anything like a vacuum? (BTW, I never intimated that oxygen in water could be utilized in any way,just that it was present). My point is and was ,you cannot prove that anything will perform the same in X environment as in Y environment when x and y are so dissimilar.

 

[GregGry]

In what way is being under water anything like a vacuum? (BTW, I never intimated that oxygen in water could be utilized in any way,just that it was present). My point is and was ,you cannot prove that anything will perform the same in X environment as in Y environment when x and y are so dissimilar.

Both environments are similar in the fact that neither has available oxygen that could be used in the combustion/expansion process that propels the bullet down the barrel. Unless your suggesting that a pistol which is submerged in water can utilize dissolved oxygen to promote combustion.

 

[natman]

Water is two parts oxygen so a gun's ability to fire under water in no way proves that it will fire in a vacuum. I think the burning rate of powder will be diminished in the absence of oxygen. Just how much can be debated into infinity. Fun to talk about but how many here will ever test your theory?

Every time the subject of firing a gun in space comes up somebody brings up "will it fire with no oxygen?".

The answer is yes, it will because the gunpowder contains its OWN oxygen.

However, I have to give you extra credit for originality for coming up with the "guns can fire underwater by burning water" theory.

 

[jimmyraythomason]

"guns can fire underwater by burning water" I never said that!

 

[edrice]

Water is two parts oxygen so a gun's ability to fire under water in no way proves that it will fire in a vacuum.

That appears to be a non sequitur. Water's chemical makeup has nothing to do with firing in a vacuum.

I think the burning rate of powder will be diminished in the absence of oxygen.

How do you figure? If smokeless propellant has no need of atmospheric oxygen, why would an absense of atmospheric oxygen have any effect?

It's hard to believe we're back here again. We've come full circle as if none of the previous posts ever happened. Solid fuel rocket propellants also are fully contained with their own oxidizers and have been fired in space.

The departure from the use of gunpowder to more powerful fuels (higher specific impulses) marks the development of modern solid fueled rockets. Once the chemistry behind rocket fuels (fuels provide their own "air" to burn) was discovered, scientists sought the evermore-powerful fuel, constantly approaching new limits. A composite propellant is a mechanically mixed combination of the oxidizer and the fuel. Some common solid oxidizers are: ammonium perchlorate (NH4-ClO4) and ammonium nitrate (NH4-KNO3), chemicals providing far more oxygen than potassium nitrate (KNO3), the oxidizing agent in gunpowder. These oxidizers are often mixed, in making composite propellants, with synthetic rubbers such as: polystyrenes, polysulfides, and polyurethanes. Another type of propellant is homogeneous where the oxidizer and the fuel are combined as one molecule. Propellants of this type often use a double-base (combination of two propellants) of nitrocellulose and nitroglycerin (C3H5(ONO2)3).

--from http://adc.gsfc.nasa.gov/adc/education/space_ex/solid.html

Maybe NASA didn't know they were doing it wrong? I'm not sure why this is being fought so hard. The science is certainly there.

whoa, have you ever taken a basic chemistry class??

Yes, and college chemistry. And the point would be...?

Ed

 

[GregGry]

"guns can fire underwater by burning water" I never said that!

Well what exactly are you saying then?

A) Gun under water: No useable oxygen to promote combustion

B) Gun in space: No usable oxygen to promote combustion

If a gun will fire under water then it will fire in space. In this case If A) is true then B) is true as well. In space there are less ways that the round could be prevented from being fired. Such in the case of water soaking into the cartridge and disabling the powder/primer, or the gun blowing up due to the increase in pressure.

Many people don't believe a gun will fire in space because of the lack of oxygen. Since the powder has its own oxidizer it would fire in space. Although a vacuum is different from water pressure, for the sake of this test the difference doesn't matter because its a issue of the absence of oxygen that is at the heart of the debate.

 

[edrice]

In what way is being under water anything like a vacuum?

Neither has available oxygen. Try breathing in either environment.

My point is and was ,you cannot prove that anything will perform the same in X environment as in Y environment when x and y are so dissimilar.

Do you honestly think a solid fuel rocket that will fire in the vacuum of space wouldn't fire underwater?

Ed

 

[edrice]

If a gun will fire under water then it will fire in space. In this case If A) is true then B) is true as well. In space there are less ways that the round could be prevented from being fired. Such in the case of water soaking into the cartridge and disabling the powder/primer, or the gun blowing up due to the increase in pressure.

And that's another point that hasn't been brought up. Firing a gun underwater would seem rather catastrophic, if not, at least, hard on the gun. I'd much rather fire one in space. Another advantage to space is that, while you'd have sorry ballistic coefficients underwater, you'd have great BC in a vaccum. I guess all bullets would be equal, wouldn't they? A boat tail spitzer being no better than a wadcutter...

Ed

 

[android]

If a gun will fire under water then it will fire in space. In this case If A) is true then B) is true as well. In space there are less ways that the round could be prevented from being fired. Such in the case of water soaking into the cartridge and disabling the powder/primer, or the gun blowing up due to the increase in pressure.

The increase/decrease in pressure is negligible. Take a 9mm with a max pressure of 34,084 psi. Space is 0 psi, 1 atm = 15 psi and 33 feet of water = 30 psi. so 30 vs 34000 means 34000 will always win. Heck, you could even got to 66 feet.

Absent wet powder, a bullet will make it out of the barrel just fine in all three cases. The drag on the bullet is much higher in water though and it will slow much more quickly.

 

[bruss01]

The increase/decrease in pressure is negligible. Take a 9mm with a max pressure of 34,084 psi. Space is 0 psi, 1 atm = 15 psi and 33 feet of water = 30 psi. so 30 vs 34000 means 34000 will always win. Heck, you could even got to 66 feet.

Not a valid comparison. You are comparing the ambient pressure of the environment, when what you ought to compare is the pressure of accelerating the additional mass and the friction involved. So however much water is in the barrel, the weight of that water gets added to the bullet weight because the propellant now has to accelerate that additional mass. When actually tested underwater, shotgun barrels get burst and rifle barrels get bulged. Pistols usually survive because the barrel is shorter and less water mass resists the bullet's acceleration.

BTW I too am surprised that we are having the conversation about firing in a vacuum. It is possible to deduce that it will fire by virtue of the oxygen needed for combustion already being contained in the powder in solid form. One question I have not seen addressed is whether any trapped air inside the cartridge would be sufficient to unseat the primer or bullet. It would be possible to test this. I have a vacuum chamber (NO I am not offering to donate it to the cause!) which I use for plastics forming (hobby). get a small gun and put it inside a vacuum chamber (large PVC pipe for instance) with a way to electrically trigger it remotely. Evacuate all the air down to 0 psi. Then remotely fire the gun electrically (solenoid of some sort). This is the kind of thing Mythbusters or box-of-truth should undertake just to put it to rest for good.

I CAN test whether bullets or primers would become unseated by exposure to high vacuum. Hmm, that would make a nifty little experiment.

 

[edrice]

The increase/decrease in pressure is negligible. Take a 9mm with a max pressure of 34,084 psi. Space is 0 psi, 1 atm = 15 psi and 33 feet of water = 30 psi. so 30 vs 34000 means 34000 will always win. Heck, you could even got to 66 feet.

That's fine as far as it goes. You didn't state bullet weight, but lets take a 124 grain 9mm (about 8 grams) that the propellant has to move out of that barrel. If the barrel is filled with water then how many more grams of water does that propellant have to push out of the barrel to get the bullet out? The longer the barrel the more weight in water that needs to be moved.

Seems this would cause a terrible pressure spike and I wouldn't want to be the one to fire it.

Ed

 

[edrice]

One question I have not seen addressed is whether any trapped air inside the cartridge would be sufficient to unseat the primer or bullet.

Since it takes way more than 15psi to seat a bullet or primer, I don't see where that would be an issue.

Ed

 

[edrice]

This guy has come up with an estimation for the force required to seat a bullet -

A bullet that has base surface area of say a typical .308 has an area of Pi x radius squared or .154 X .154 X 3.14159, or 0.07450594844 square inch. If it takes for example 15 lbs. of force to seat a bullet, it would take approximately the same to un seat it. By my calculations, to reach 15 lbs. of force it would take an internal pressure of 201.326 PSI to exert a 15 lb. force on the end of that bullet. (15 divided by the surface area of the bullet, 0.07450594844 = 201.326)

--from http://benchrest.com/articles/articles/12/1/How-Far-Apart/Bullet-Seating.html

A primer probably wouldn't be all that much different. It has a smaller diameter so wouldn't seem as if much force was being exerted.

Ed

 

[chris in va]

Which begs the question...if you fired a gun toward the earth, would it produce a 'meteor'?

 

[LibShooter]

if you fired a gun toward the earth, would it produce a 'meteor

I think it would produce a pretty good one. The little rocks and dust producing most meteors are a lot smaller than bullets. They're moving a whole lot faster, though. Could some rocket scientists out there do the math?

 

[Claude Clay]

if you fired a gun toward the earth, would it produce a 'meteor'

begs the answer---
depends on how fast you fire the gun

seriously, many man made things have fallen out of the sky--skylab 'landed' in Australia. some of it anyways. what metals survived and what burned are on film. details @11