Lets say you shoot a tracer round into a tree without it exiting. Will the tracer element burn inside the tree until its used up or go out immediately due to lack of O2? What about under water? I always thought you couldn't have combustion without 02 so my thinking would be "NO."

You can obtain oxygen from more sources than just the air. There are lots of chemical compounds which can release oxygen when manipulated, typically by heating (potassium permanganate) or by introduction of a catalyst (hydrogen peroxide). Other compounds, such as hydrazine, come to mind. The latter was used in liquid-fueled rocket motors. The Soviets use concentrated hydrogen peroxide to provide the oxygen for the motors in their torpedos. As a matter of fact, it is speculated that a leaky H2O2 container inside one of these torpedos triggered the catastrophic demise of the Kursk a couple of years ago.

The oxygen is included in the tracing chemical compound. Also, the cartridge propellant compound (gunpowder) also contains all the oxygen that it will ever get before the bullet leaves the muzzle. A supersonic bullet will have almost a complete vacuum at its base and no oxygen from the air could make its way into the tracer base cavity. The trace compound will continue to burn to completion unless something physically stops it such as hitting an object that shatters and disperses the compound (fragments and dust cooled below burning temperature) or is rapidly cooled below burning temperature (in water).

I wonder if the pressure differential between the atmosphere inside the cartridge and a vaccuum would cause a cartridge failure.
Sure the air would leak out, if not properly sealed, but would the pressure be enough to drive the bullet from the case?

If not would a .223 Rem be able to be fired on the moon?  Assuming the cartridge was viable upon detonation, would there be any other crazy stuff happening?

It would be cool to do some long range shooting on the moon!

(Yeah, you can tell where my head is)

Tracer mixtures are made from a metal fuel, almost always powdered magnesium metal, and an oxidizer, usually strontium nitrate.  The strontium nitrate, Sr(NO3)2, serves a duel purpose; it provides all the oxygen needed to burn the magnesium to magnesium oxide, and the heat given off by the reaction heats the strontium which gives off a red color.  The Russians use barium nitrate and when barium is heated, it gives off a green color (hence, green tracers).  

To answer your question, the formulas are balanced such that there is enough strontium nitrate to supply ALL the oxygen to burn the magnesium completely.  If it enters a tree and the bullet/tracer compound remains relatively intact, the tracer compound will continue to burn.  It is more than hot enough to ignite the center of the tree if it is rotted away and dry inside.  Probably wouldn't worry about this unless you live in a tinderbox like California.

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ArmyOrdGuy:
The trace compound will continue to burn to completion unless something physically stops it such as hitting an object that shatters and disperses the compound (fragments and dust cooled below burning temperature)
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True.  I have tried this.  But it doesn't stop burning if the bullet remains intact.  Only you can prevent forest fires!

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ArmyOrdGuy:
or is rapidly cooled below burning temperature (in water).
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Probably true.  I've burned tracer compound (mixed myself) in small 1/4" wax-paper tubes and they were not extinguished by submerging them in water.  But there is a lot less tracer compound at the base of a 5.56 tracer and this would likely be cooled and extinguished easily.  I've never fired tracers into water, but I have a feeling ArmyOrdGuy has and speaks from experience, the greatest teacher.

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zhukov:
There are lots of chemical compounds which can release oxygen when manipulated, typically by heating (potassium permanganate) or by introduction of a catalyst (hydrogen peroxide). Other compounds, such as hydrazine, come to mind. The latter was used in liquid-fueled rocket motors.
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Mostly true, except for the fact that hydrazine, N2H4, contains no oxygen.  Hydrazine was an excellent fuel for liquid rockets that powered the U.S. and Soviet nuclear arsenal but was burned with either nitric acid (HNO3) or nitrogen dioxide (NO2) which supplied the oxygen.  These were the missiles in heated silos.

TORF: I said that the oxygen is included in the compound, NOT THAT AIR WAS INCLUDED.Oxygen and calcium make chalk. Air does not leak out of chalk. Oxygen, hydrogen, and sodium make table salt. You won't see oxygen or hydrogen leak out of the salt. The oxygen is chemically joined in the tracing mix and is converted into waste products upon combustion. The next point is that any atmospheric pressure difference wouldn't rupture a bullet. It's a copper alloy jacket stuffed with lead and a burning chemical mix in the base (tracer round). This is a very sturdy chunk. The space shuttle or a submarine would be more likely to rupture. Lastly, do not use the term "detonation" when referring to the functioning of small arms ammunition (unless the weapon is in many pieces in your hands and chest). Projectile ammunition is driven by combustion, NOT detonation. Detonation is a blast wave of several thousands of feet per second and isn't pretty. When I first got into this field, I said "detonation" and got hammered by everyone in the area.

Also keep in mind that firing a firearm on the moon or a planetary body without an atmosphere or any vacum for that matter would actually be safer than here on earth. Recoil problems asside, the lack of atmospheric pressure should result in little to no chance of KB's resulting from extreme chamber or barrel pressure. In addition, our modern propellant has it's own oxygen in the mix, so don't worry about the lack of oxygen. Also without any atmospheric friction and little(moon) to no(space) gravity acting on the inflight projectile your range would be almost indefinite. Firing from just outside of earth orbit you could hit a target on pluto, assuming you time it right so that it does not get caught in the gravitational field of any other orbiting planet or large asteroids, and of course it would probably take 140 years to get there. And you would need a sighting device that could compentsate for plantetary movement, galactic gravitational variants, lag of light travel time for sight picture, yada yda yada.

The only thing you have to worry about is the recoil of the .223 throwing you back about 10 feet on the moon or an indefinite distance in open space...hehhehe

Man! I really do need to get a life. Don't I?

Thus ending the chemistry and physics lessons for today. Thanks for answering my question gentlemen. I learn something new on this website almost daily.

I understand, I didn't know if the small volume of oxygen in the case was needed or not.  Either way, I was wondering if the atmosphere in a cartridge (not loaded in a vaccuum) would leak its air out fast enough to blow out the primer or the bullet.  Think, explosive decompression.



Yeah, I figured the case itself was strong enough, but the chamber of the firearm is where MOST of the strength really is.  I was more thinking about the bullet seating and primer pocket strength.  How much pressure would it take to pop that out.  Ammo loaded in my garage has an internal pressure of about 30 inches of Hg.  The moon has almost zero.  If this ammo were exposed to lunar pressure, would the primer pop out or the bullet budge?



I'll keep that in mind, but I was mostly referring to the primer detonation.  I don't know what the compound is that they use now, but Mercury Fulminate is an explosive not a propellant like smokeless powder is.

I can't even begin to imagine how complex it would be to try to compensate for gravitational fields.  It would be pretty tough to hit an 'easy' target like the moon from an orbiting shooting platform.  Even from the surface of the moon to Mars, you would have to compensate not only for Sun/Earth/Moon/Mars gravity, but for the fact that you are shooting from a complexly moving platform.

Gunnery on the surface of the moon would be much simpler.  Recoil from a rifle round is transferred to the shooter in a horizontal direction, same as earth, and in the same amounts.  Your body also has the same mass on the moon, so recoil will be the same.
The difference would be the friction you would have with the soil.  Lunar soil would give a person plenty of friction to avoid a slow motion backwards skid.

A .02 Gee steel platform might present a little problem though!

I think the coolest thing would be being able to shoot at targets 10-20 klicks away and hitting your target with the same velocity as at the muzzle.  Not having to adjust for wind would be awesome.  Ballistic coeficcient would be moot, and so everyone would be using little 40 grain V-Max bullets to get their velocity close to 4000.

In outerspace I wouldn't be so sure that ammunition would work, the powder won't burn without the oxygen that is sealed inside of the case with the powder. The vaccume of space would probably cause the air pressure inside the case to eject the bullet, burst the case, or at least expand the case so it can't be used.

Inside the case the pressure is equal to or greater than the 14PSI air pressure at ground level, put it in the vaccume of space it will fail in one of the above ways. I would say firearms won't work in the vaccume of space.

Nothing will burn without oxygen, water will put out the magnesium tracer.

The air inside the cartridge is completely unimportant. The necessary oxygen is included within the propellant mix. An outside vacuum or very low pressure will not affect the cartridge.The primer won't pop out, the bullet be pushed forward, or the case bend. This was well proven in the mid 1940's at 30,000 feet in B-17 Bombers (an unpressurized airplane) with tens of thousands of rounds of .50 cal ammo. Yes, you could shoot a cartridge weapon in a vacuum.

Also catastrophic failure pressure limits would not be increased due to lack of outside atmospheric pressure, it's a sealed unit until the bullet leaves the barrel.  Kabooms most definitely would still be possible, even more likely given the lack of external pressure helping to compress and strengthen the barrel.

At 30,000 feet you still have somewhere in the area of 7 PSI, now go into the vaccume of space there is no air pressure, there is a vaccume on the case + air pressure on the inside = somethings got to give. The bullet or the primer will eject from the case.

Don't forget the Carbon.  CaCO3




Uh...what?  Salt = NaCl.  Where's the O2 and H2?

Nothing will "give". The cartridge case is more than strong enough to deal with the pressure differential. The primers and bullets will be held in place by friction and/or crimps. Both the priming and propellant compounds carry sufficient oxygen in their chemical make up to completely combust.  You need to do more research. Otherwise you might post something on the internet that will make you sound foolish.

BigD:  Good catch. I realized that I forgot the carbon later but figured nobody would notice. I totally missed the Sodium Hydroxide glitch (and I'm a Chemist). Thanks for keeping me straight.

Since none of us can get the real answer because none of us will be going into space anytime soon, it's all pure speculation. The powder alone dose not have enough oxygen in it's chemical make up, but there is oxygen sealed inside the case which allows it to burn.

I want to hear more about the B-17 gunners! I bet the ballistics of those 50 cal rounds was fantastic at that alltitude. Did they ever have to worry  about over-heating their guns or was it cold enough at alltitude to empty your gun out and attach a new belt with no worries. What type of ammo where they using? AP, FMJ tracer, Incindiary(sp). How much ammo did they carry for each gun? Did they typically use it all up on a misson? What was the average hit rate and stats on kills?

Those are the sort of things I'm talking about. You should really stop. You're embarassing yourself.

For a very simple example for those who don't understand the role of oxidizers in a chemical reaction, take a piece of water proof fuse, light it and then drop it in some water.  It will continue to burn because the oxidizer(potassium nitrate) provides the oxygen necessary for the reaction.  This is pretty much the same thing that occurs inside a cartridge case, just a lot slower.  No outside oxygen is needed.  

Just to continue bigdb1's thought.  Cellulose trinitrate is the completely nitrated product from the nitration of cellulose.  The chemical formula is [C6H7O2(ONO2)3]n, with the 'n' representing the fact that the molecule is in a chain as cellulose is a polymer of glucose.  If we double the formula and 'burn' it, we get the following products:  12CO + 14H2O + 3N2 + 3O2.  So, there is in fact more than enough oxygen to burn all of the carbon and hydrogen present in the smokeless powder molecule.  Smokeless powder does not contain fully nitrated cellulose, but close enough.  Since there is an excess of oxygen, this more than makes up for  the incompletely nitrated product used in commerce.  The muzzle flash is in part due to the carbon monoxide gas being burned to carbon dioxide gas as it leaves the muzzle and is exposed to fresh oxygen in the air.  Flash suppressors work, in part, by cooling the carbon monoxide gas enough so that it does not ignite.  BUT, your bullet is already out the barrel.  


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JustL00king:
The powder alone dose not have enough oxygen in it's chemical make up, but there is oxygen sealed inside the case which allows it to burn.
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No flame, but, where do you get your information?

My Reference:  Tenney L. Davis, Ph.D., The Chemistry of Powder and Explosives, p.256.  Also, do a quick patent search and you will find endless references.

Posted by JustLooking:
Nothing will burn without oxygen, water will put out the magnesium tracer.

Water and burning magnesium can be a very unfriendly combination.

Exactly, certain metals heated to a high enough temperature, will strip the Oxygen out of the water molecule and liberate Hydrogen.  Typically this is an exothermic (heat generating) reaction.

As to the internal pressure blowing cartridges apart in a vacuum, a little common sense will tell you that since we need a primer (at least) to even get a squib load, air pressure won't disassemble a cartridge.  And the gas inside a cartridge would most likely outgas slowly through primer pocket, the neck of the cartridge or diffuse through the brass as the external pressure dropped.

Drop any one of your Alkali metals into a bucket of water.

Start with Sodium, and you will see sparks.
Move up to Potassium and you will really get some fireworks!
Move up to Cesium and you will be missing body parts the instant the chunk hits the water.

The atmosphere allows our familiar chemical reactions to occur the way we are used to, but nothing will prevent chemical reactions when all the REQUIRED elements are present.

Quoted:
Since none of us can get the real answer because none of us will be going into space anytime soon, it's all pure speculation.

No, its not pure speculation.  The things we are taking about are freshman level chemical and mechanical engineering questions.  We can use the "magic" of science and math to predict with suprising accuracy what will happen in certian situations.  That's the beauty of science.

In the case of the bullets in the vacuum of space "exploding" due to the residual internal pressure from loading in earth's atmospere:

Givens:

1 atmosphere = 14.7 psi
.223 case approx. .38 dia.

Solutions:

Force on bullet base trying to pop it out of the case

(pi*.224^2)/4=.039 in.^2 (bullet area)

.039 in^2 * 14.7 lb/in^2 = 0.58 lbs force on bullet base.  (Not enough to force a bullet out based on my expiriences with a bullet puller.  Primers are even smaller in dia. giving less area for the pressure to work on.)

Axial stress on case (lengthwise stress):

pi*.38^2)/4=.113 in.^2 (case end area)

.113 in^2 * 14.7 lb/in^2 = 1.67 lbs force on case ends (axial load).  Not much straining the case there. (I bet it gets a harder yank (more stress) during ejection.)

Making an assumption for minimum case wall thickness (.040"), hoop stress (stress oriented like the hoops of a barrel) is about 70 psi.  Brass has a yield strength of around 50,000 psi.  You are at about 0.1% of the yield strength in a vacuum.  No danger of failure here either even if my assuption is way off.

Conclusion:  No danger, as stated earlier, of a case explosion or a bullet or primer coming unseated in the vacuum of space.

Now, how about the burning rates of the powder and primer at 0 deg. K?

Kent

And don't forget, 500 degrees K in the sun!

Temperature may be the only problem with our newly formed "Lunar Rifle Team".

Oh crap! I can't believe I forgot about the extreme tempuratures!

Here I go to my room to shinee up my space helmet and use 3 cans of gun-scrubber to make sure my AR has no lubrication. But that only helps for the shady side. what do I do when I'm on guard duty on the sunny side of Mir?

Guess What????  IT's ALREADY BEEN DONE!!!!

[url]http://www.astronautix.com/project/almaz.htm[/url]