But black powder and smokeless powder are NOT solid rocket fuels.
Go back and look what I wrote that you quoted first.
Would the helium not change the mach number behind the projectile based on your post?
Is that nothing?
So what creates the pressure?
Would loading a cartridge with no fluid between the powder interstitials and other void space similarly BUILD no appreciable pressure?
How does the pressure rise but not in space? Or helium?
Have you heard of flame front propagation rates, and how they can differ?
Could atmospheric oxygen in the cartridge case, or lack of it, affect flame propagation rates?
And be part of the reason smokeless and black powders are NOT used as solid rocket fuels?
Intermediate reaction pathways?
The dynamic picture being more important than the static state of initial reactants and final products?
Maybe seeing a minor issue ignores a major issue?
Helium in your cartridges would be kind of like nitrogen in your tires. Advertising.
Sure they are. What do you think Mr Congreve used? The British used Cordite as a rocket propellant. In suitable (large) grain size, of course.
So why doesn't it generate the pressure in the absence of atmospheric oxygen?You could not get enough helium in a conventional cartridge at 1 atmosphere pressure to make a measurable difference. I don't think the military would want a pressurized cartridge to get enough helium to make a measurable difference. The average molecular weight of the gas in the barrel would be significantly higher than pure helium as the propellant burned producing much heavier gases. Helium is also very difficult to contain as it tends to defuse through many solids especially at higher pressure making a 20 year shelf life typical of military ammo difficult to maintain.
And yet black powder and nitrocellulose and nitroglycerin (the two primary ingredients in smokeless powder) have all been used successfully in solid rocket motors. They are milled differently in to very different solid shapes than when used as gun powder for small arms but it is the same thing.
Yes there is sufficient oxidizers present to burn completely without external oxygen. With black powder the ratio of 75% potassium nitrate, 15% charcole, 10% sulfur results in a roughly stoichiometric balance of fuel (charcoal and sulfer) and oxidizer (potassium nitrate). In the case of single base smokeless propellants (nitrocellulose being that single base) there is again a near stoichiometric balance of fuel and oxidizer (assuming all the cellulose is fully nitrated) present in the nitrocellulose. If we are talking about a double base powder that also includes nitroglycerin then there will be an surplus of oxygen as for every two molecules of nitroglycerin that decomposes they produces an extra O2 molecule not consumed in the decomposition.
I always thought the limit was the speed of sound in the hot propellant gases. This sort of makes intuitive sense, sans any math.
There were some German guns being built on the principle of additional chambers containing propellant along the barrel length, to keep the pressure (and the temperature) up. I believe Jules Verne used this idea in one of his novels for the moon cannon.
Terry, 230RN
Well, let's see if Wikipedia can help.
"Nitrocellulose contains insufficient oxygen to completely oxidize its carbon and hydrogen. The oxygen deficit is increased by addition of graphite and organic stabilizers."
https://en.m.wikipedia.org/wiki/Smokeless_powder
But - but - but that means the powder stoichiometry isn't sufficient for complete combustion like the man said.
How do we make more gas molecules to raise the pressure?
Maybe we can react oxygen from the atmospheric air, but not helium, and not in space - so the same mass of gas isn't generated in the absence of atmospheric oxygen. And the cartridge case can hold enough if we load smart, like Quickload shows us!
And by golly, converting greater mass to gas in the same volume means pressure must increase! Then the bullet moves, but solids are still being converted, and so on until, and a short ways after, the bullet exits the muzzle. That's why muzzle flash can happen!
Not a minor point at all when & where I went to school. And Wikipedia and Google didn't exist then.
Clearly you remember more of your chemistry than I do. Nicely put.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.
I am a Chemical Engineer not mechanical, review that in my first post this thread.You seem to be on a crusade so i will grant you the victory. I was wrong about nitrocellulose being balanced fuel/oxygen wise. I am a mechanical engineer not a chemist. But it's close to balanced and there is sufficient amount of self oxidizing to keep the combustion reaction happening in the absence of external oxygen sources. This has been proven many times. There are plenty of articles and video showing gun powder burning in various oxygen-less atmospheres.
This also would be another reason why double base powers produce better performance in some circumstance as the excess oxygen from the nitroglycerin no doubt gets a more complete burn of the nitrocellulose. This is also why they probably burn hotter and in many cases cause increased rates of barrel erosion.
And we are now way off topic. Shockwave propagation in the propellant gases is the prime limiting factor in what limits the maximum velocity of a gun powder propelled projectile. It is not the only thing but it is the prime factor.
Light gas guns get more velocity by using a gas with a higher speed of sound in their working gas acting on the projectile.
Rail guns by using electromagnetic forces rather than shock limited gases as there motive force. Though some rail guns still use combustion initially to inject the projectile at high speed into the rails. A rail gun's efficiency is much higher as the projectile's speed increases.
Yes there is sufficient oxidizers present to burn completely without external oxygen. With black powder the ratio of 75% potassium nitrate, 15% charcole, 10% sulfur results in a roughly stoichiometric balance of fuel (charcoal and sulfer) and oxidizer (potassium nitrate). In the case of single base smokeless propellants (nitrocellulose being that single base) there is again a near stoichiometric balance of fuel and oxidizer (assuming all the cellulose is fully nitrated) present in the nitrocellulose. If we are talking about a double base powder that also includes nitroglycerin then there will be an surplus of oxygen as for every two molecules of nitroglycerin that decomposes they produces an extra O2 molecule not consumed in the decomposition.
Do a google search there are lots of articles and videos on the fact that gun powder will burn in the absence of oxygen. The problem with burning gun powder in a vacuum is not the lack of oxygen but the lack of pressure. If you do not have pressure then the gun powder will frequently stop burning due to the combustion front not being able to propagate. You see this even in standard atmosphere conditions. Go shoot a bunch of pistol ammo in short barreled handgun and you will find a bunch of partially burnt powder grain on the floor down range (380 ACP in pocket pistols due to its lower pressure is very good at this.) The powder does not completely burn before the bullet exits the short barrel and at atmospheric pressure (and the grains moving very fast through it) they can be extinguished and don't fully burn despite having sufficient oxygen.
One nice example of black powder burning and not burning in a vacuum due to the ability to produce pressure or not:
Explain the difference in pressure rise in absence of oxygen vs presence of oxygen.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.
Where are you seeing data that shows a pressure difference between a gun at standard atmospheric conditions and in the absence of external gaseous oxygen? Share that data if you have it I would like to see it.Explain the difference in pressure rise in absence of oxygen vs presence of oxygen.
Explain the difference in pressure rise in absence of oxygen vs presence of oxygen.
Yes there is sufficient oxidizers present to burn completely without external oxygen. With black powder the ratio of 75% potassium nitrate, 15% charcole, 10% sulfur results in a roughly stoichiometric balance of fuel (charcoal and sulfer) and oxidizer (potassium nitrate). In the case of single base smokeless propellants (nitrocellulose being that single base) there is again a near stoichiometric balance of fuel and oxidizer (assuming all the cellulose is fully nitrated) present in the nitrocellulose. If we are talking about a double base powder that also includes nitroglycerin then there will be an surplus of oxygen as for every two molecules of nitroglycerin that decomposes they produces an extra O2 molecule not consumed in the decomposition.
Do a google search there are lots of articles and videos on the fact that gun powder will burn in the absence of oxygen. The problem with burning gun powder in a vacuum is not the lack of oxygen but the lack of pressure. If you do not have pressure then the gun powder will frequently stop burning due to the combustion front not being able to propagate. You see this even in standard atmosphere conditions. Go shoot a bunch of pistol ammo in short barreled handgun and you will find a bunch of partially burnt powder grain on the floor down range (380 ACP in pocket pistols due to its lower pressure is very good at this.) The powder does not completely burn before the bullet exits the short barrel and at atmospheric pressure (and the grains moving very fast through it) they can be extinguished and don't fully burn despite having sufficient oxygen.
One nice example of black powder burning and not burning in a vacuum due to the ability to produce pressure or not:
Yes there is sufficient oxidizers present to burn completely without external oxygen. With black powder the ratio of 75% potassium nitrate, 15% charcole, 10% sulfur results in a roughly stoichiometric balance of fuel (charcoal and sulfer) and oxidizer (potassium nitrate). In the case of single base smokeless propellants (nitrocellulose being that single base) there is again a near stoichiometric balance of fuel and oxidizer (assuming all the cellulose is fully nitrated) present in the nitrocellulose. If we are talking about a double base powder that also includes nitroglycerin then there will be an surplus of oxygen as for every two molecules of nitroglycerin that decomposes they produces an extra O2 molecule not consumed in the decomposition.
Do a google search there are lots of articles and videos on the fact that gun powder will burn in the absence of oxygen. The problem with burning gun powder in a vacuum is not the lack of oxygen but the lack of pressure. If you do not have pressure then the gun powder will frequently stop burning due to the combustion front not being able to propagate. You see this even in standard atmosphere conditions. Go shoot a bunch of pistol ammo in short barreled handgun and you will find a bunch of partially burnt powder grain on the floor down range (380 ACP in pocket pistols due to its lower pressure is very good at this.) The powder does not completely burn before the bullet exits the short barrel and at atmospheric pressure (and the grains moving very fast through it) they can be extinguished and don't fully burn despite having sufficient oxygen.
One nice example of black powder burning and not burning in a vacuum due to the ability to produce pressure or not: