So why did both reaction kinetics and reaction products change with atmosphere, and cease in a vacuum, based on first principles? No guessing. Honest critical thinking. Gas phase changes things, absolute lack of a gas phase stops the reactions. But using a vacuum to break the combustion of nitrocellulose is prima facia absolutely impractical for the group these tests were conducted for in 1992. No weasleing not being good at PChem voids ability to produce a rational reasoned answer supported at minimum by first principles.
The oxygen in the test flask mattered. The oxygen in a cartridge case also matters. The lack of oxygen in a vacuum matters.
What is the internal pressure in a cartridge case right before any combustion is initiated?.I'd say approximately one atmosphere absolute, same as the paper. I never said pressure does not increase when solids are converted to gas, in fact I've consistently said the opposite. Did you notice that yet?
I went back and put the most recent prior instance in bold font to help out.
The Estes Co, who makes model rocket motors, say otherwise. They use compressed black powder as their propellant.And be part of the reason smokeless and black powders are NOT used as solid rocket fuels?
Uhhhh.....HELLO!!! That's NOT black powder! It is American Pioneer black powder substitute. It contains no sulfur, and is chemically quite different from black powder.Another good video of black powder burning in a vacuum:
I did not recognize the bottle so I was not sure if it was actual black powder or a substitute. Either way it is still a self oxidizing propellant that burns in the absence of oxygen. In the same video he does burn rocket fuel from and Estes rocket which we know is a black powder.Uhhhh.....HELLO!!! That's NOT black powder! It is American Pioneer black powder substitute. It contains no sulfur, and is chemically quite different from black powder.
Well stated, sir !I did not recognize the bottle so I was not sure if it was actual black powder or a substitute. Either way it is still a self oxidizing propellant that burns in the absence of oxygen. In the same video he does burn rocket fuel from and Estes rocket which we know is a black powder.
While I agree that your upper limit is pretty close to the practical limit. The reasoning is a bit flawed. The flow does not choke, and the flow behind the bullet is supersonic.It is very very difficult to push a bullet faster than the speed of sound in the propellant gases pushing the bullet. Going faster than the speed of sound (of the propellant gases) forms a shock-wave in the barrel choking the gas flow and significantly lowering the pressure on the base of the projectile limiting further acceleration. In theory (IIRC), doing lots of funky things to optimize conditions like evacuating the air out of the barrel in front the projectile, things to reduce friction and similar difficult optimizations ~6500 fps should be theoretically possible with some modern propellants. In practice ~5700 fps is about the limit.
I believe the Rheinmetall Rh-120 (the main gun on the Abrams and the Leopard 2 tanks) holds the muzzle velocity max for a production weapon system using gun powder. The APFSDS rounds (tungsten or depleted uranium) can reach a bit over 5700 fps.
You can go much faster using two stage gun called a light gas guns. The first stage uses combustion like gun powder to compress the second stage of helium or hydrogen (speed of sound in these two gases is much higher) that accelerates the projectile. They have used light gas guns to launch projectiles at over 22,000 fps.
-rambling
Muzzle flash is caused by the fact that the combustion products of propellant burning are combustible, but there is a lack of oxygen in the barrel behind the bullet. After the bullet exits the barrel the combustion products mix with the ambient air and are ignited by a pressure wave formed by the expanding gas ejected from the barrel.Now think about why muzzle flash exists. I have yet to see or hear of a military or civilian, smokeless or black powder, that causes zero muzzle flash. Reduced, yes, but why not zero?
If your postulation is correct, why isn't the military especially not specifying their ammunition cases be filled with helium? Or the propellant charges of the 120mm Main Battle Tank cannon you mentioned, if it's all so simple? Those are smoothbores, the sabot provides a ballistic guidance seal along the walls and the gas seal at the rear of the projectile, right? No rifling to engrave. Energy on target is important enough to manufacture depleted uranium penetrators as you noticed, but with collateral side effects as noted in The Gulf War when that stuff vaporizes. But it sure looks good on paper.
While I agree that your upper limit is pretty close to the practical limit. The reasoning is a bit flawed. The flow does not choke, and the flow behind the bullet is supersonic.
The speed of sound is governed by:
v = sqrt [(gamma x R x T)/M]
with (metric units):
v = the speed of sound in m/s
gamma = the adiabatic constant, characteristic of the specific gas, for propellant gas, this is 1.24,
R = universal gas constant (8.314 J/mol K),
T = absolute temperature (typical propellant gas temperatures for small arms is in the 2500 K range), and
M = the average molar mass, for propellant gas, which is somewhere in the .035 to .040 kg/mol range.
Throw all that in a calculator the speed of sound for that gas would be around 800 m/s, well short of the 1750 m/s of a tank gun. It's actually a little short of your high velocity small caliber bullets like 5.56mm which run in the 1000 m/s range. Really hot tank gun propellants might reach 3500 K, but that only raises the speed of sound to around 950 m/s.
For those that don't speak metric 800 m/s = 2625 fps; 1000m/s = 3300fps; and 1750 m/s = 5750 fps,
For providing thrust in vacuum, as previously asked?The Estes Co, who make model rocket motors, say otherwise. They use compressed black powder as their propellant.
Untrue from stoichiometry to begin with. Plus containment of oxygen ions is required to sustain the reaction. The boundary layer is where the reactions occur including the external surface of individual solid propellant particles plus the pores. Without renewal of fresh oxygen whether atmospheric or evolved along that boundary layer while in a state above reaction energy threshold reaction ceases. Reaction kinetics are a teal world plank of science including these solid propellants, it must propagate. It is not quantum behavior with nothing intermediate existing between "ladder rungs" of reactants to products. CUP test pieces do not spring from fresh untested to elongated as "ladder rungs", but elastic deformation over time with intermediate states. Pressure curves are real outside true vacuum by definition of vacuum, which is absolute zero pressure; containment of any and all evolved gases is not vacuum. Dalton's Law applies.There is not enough atmospheric oxygen in a cartridge to matter.
IMR smokeless powder is mostly nitrocellulose. The density of nitrocellulose is 1.23 gm/ml. The bulk density of IMR 4350 powder is .945 gm/ml. Therefore the powder charge in a cartridge full up to the base of the bullet is 77% (mostly) NC, 23% air, or 4.6% oxygen by volume. But the density of air is only .00128 gm/ml.
A .308 case is 3.6 ml and so holds 3.4 gm of powder, but only .0002 gm of oxygen.
Combustion product of NC smokeless propellants is carbon dioxide 28%, carbon monoxide 23%, hydrogen 8%, nitrogen 15%, and water 26%. Therefore 31% combustible gases that might react with that oxygen.
So you are making about 1 gm of fuel for .0002 gm of oxygen.
You can break it down to moles but that is not going to account for four orders of magnitude.