[Experimental] Liquid Propellant Powered Firearms

[scalper]

I was somewhat unsure where to place a post like this, so I figured 'research' might be as good as any.

I find the technology of firearms extremely fascinating. I was curious if anyone know about any past, present, or future research done with firearms powered with liquid or other alternative propellants. I am sure I will get some fun posts (like spudguns, tennis ball cannons, etc), but I am really curious if anyone has seen or heard about anything that has been seriously done. Seems like one could get some pretty clean burning high pressures with various alternative propellants.

I am not totally opposed to doing this type of research myself, since I have built some obscure types of firearms, both muzzleloading, cartridge, as well as, a few air powered guns.

 

[Jim Watson]

The US Army did some work on liquid propellants for tank and SP guns. The main advantage in an armored vehicle was that you only had to rack and load the shell; the propellant would be injected into the chamber from remote storage in well protected tanks that could make use of odd shaped spaces that would not accomodate fixed rounds.

When I heard of it, they were interested in the possibility of diluting unused or off-spec liquid propellant with water and using it for nitrogen fertilizer. I was then working in fertilizer R&D, but the ecologicaly sound disposal project never got started that I know of.

 

[SageMonkey]

I've always thought this could be an interesting means of designing a caseless ammunition system.

I know that there have been spudguns using pressurized liquid gas, including one that had a revolving cylinder offering multiple shots before reloading, I believe that it used butane. I suppose that with the right pressure and air to fuel ratios one could inject gasoline and air.

 

[Sunray]

"...the technology of firearms extremely fascinating..." Yep. And there's so much of it too.
Liquids require much more physical space than a solid material(smokeless gunpowder doesn't explode. It just burns really fast. The burn rate is controlled chemically.) does to get the same pressures. (Think in terms of the size of an engine cylinder compared to a cartridge.) Liquids weigh a whole lot more. A gallon of water, for example, weighs 10 pounds.
Other gases either don't build the pressures fast enough or don't give enough pressure. Mind you, the Swedes defended a castle with air rifles that were strong enough to kill at fairly long distances. I forget how far and exactly when. 15th or 16th century, I think.

 

[Jim Gwyn]

There are several problems with using liquid propellants in firearms or big guns.

The liquid propellants are going to be more or less similar to liquid rocket fuels. These offer greater energy per pound than solid propellants but are always trickier to handle. This is the basic reason that the armed services use solid fuels in their missiles and the space agencies use liquid propellants.

You could use cryogenic fuels such as liquid oxygen, etc. but they tend to evaporate on storage which can make resupply iffy in combat. Also, most flammable materials (wood, cloth, oil, asphalt pavement, for instance.) become either high explosives or /very/ flammable when saturated by leaking liquid oxygen.

Another option is to use so called "mono propellants." These are liquids that are mixed and ready to "go." The problem is that ~all~ of them are high explosives. Do you really want to be hauling them around, even if they are relatively insensitive? They also had the lovable habit of flashing back into the fuel tank and going boom. After lots of research, the rocket scientists gave up on them.

Yet another option is to use propellants where the fuel and oxidizer are non-cryogenic and are stored separately until they are used. The old Titan-II ICBM used a 50/50 mix of Unsymmetricaldimethylhydrazine and Hydrazine as fuel with dinitrogentetroxide as oxidizer. The problem is that both of these liquids are ~extremely~ toxic and corrosive. That thing was a maintenance nightmare and this was in a missile silo with all the comforts of home and plenty of dedicated specialists. For more info on the Titan-II, see:

http://en.wikipedia.org/wiki/Titan_II

In any event, it is just simpler and cheaper to use solid propellants.

For far more info try to find a copy of the book Ignition!: An informal history of liquid rocket propellants by John D Clark. (Amazon has them for about $ 150.00 each.)

 

[Jim K]

The comparison with rocket fuel may not be perfect. Gun powder is made to generate gas to propel a projectile. Rocket fuel is made to generate gas which will BE the projectile. In a gun, the projectile and gas moving forward causes the gun to recoil. In a rocket, the projectile (gas and burning particles) moving backwards causes the rocket to recoil forward. And because the projectile is light, a huge volume is needed to create the recoil to propel the rocket.

Jim

 

[GunTech]

There is really on one good book on LP guns, and my copy disappeared in the mail when I sent it to another THR member.

Look for "Liquid Propellant Gun Technology" by Klingenberg, et al

Be warned it is a very expensive book (i.e. $100+)

 

[PercyShelley]

But it's such a good book that postal workers are apparently inclined to steal it!

J/K I don't know what on earth happened to it.

I seem to recall some early work in the crusader project being done with HAN-based monopropellants. Being able to "dial-in" the amount of propellant you're using would be a nice perk for artillery.

 

[highorder]

A gallon of water, for example, weighs 10 pounds.

For clarity, a US gallon (231 cubic inches) weighs 8.34 pounds @ 4 degrees C.

An imperial gallon at 62deg F weighs 10 pounds.

 

[moooose102]

actually, i had thought about using gun powder as fuel in automobiles. i thought it might be a good way to get extra horsepoer on demand. not for use as the primary fuel. just like me, always getting stuff backwards!

 

[R.W.Dale]

actually, i had thought about using gun powder as fuel in automobiles. i thought it might be a good way to get extra horsepoer on demand.

The problem with this is a set volume of gasoline contains much more energy than the same volume of gunpowder.

http://www.youtube.com/watch?v=DO7R7hneQDc

about halfway through this clip is a very interesting experiment that illustrates this

IIRC I seem to remember an early 19th century internal combustion engine that used black powder as a fuel

 

[theotherwaldo]

You might also check into the "ladder gun" experiments of Nazi Germany and Saddam's Iraq. Some of these multi-chambered sequential-firing monsters used liquid propellant.

I don't want to experiment with man-portable liquid-propellant guns. I'm afraid that the errors would be spectacularly permanent.

 

[Jim K]

"The problem with this is a set volume of gasoline contains much more energy than the same volume of gunpowder."

Really? Try using gasoline in a cartridge case.

The main reason gasoline seems so powerful is that it flows and vaporizes so an explosion is spectacular. But to do so, it needs oxygen where powder contains its own oxidizer.

Jim

 

[R.W.Dale]

Really? Try using gasoline in a cartridge case.

try using gunpowder in an engine as per my reply to moose

 

[Jim Watson]

Not if the gasoline doesn't get air. 14:1 air:gasoline was the old carburetor setting, wasn't it?

 

[jeepmor]

14.7:1 to be exact.

 

[30mag]

14.7 is the (ideal) stochiometric ratio of air to fuel. Meaning 14.7 grams of air every gram of gasoline (ideally). This is the mixture not only for carburetors, but also for fuel injection, of anything else that mixes gasoline and air.

Just my two cents.

 

[solvability]

There was a German pellet rifle that used Benzine as a propellant - it worked and hit hard but was not very accurate - the point of impact and velocity changed as the barrel heated (the charges became less dense). I have always wanted to find one.

 

[Jim Watson]

The Barrakuda, made by Weirauch, I think, and advertised in Stoegers Shooters Bible for several years.
It was a conventional spring-air pellet rifle with an auxiliary chamber mounted beside the cylinder. You bought little sealed phials of, I think ether rather than benzine, and when you wanted to soup it up, you broke one into the auxiliary chamber that metered vapor into the cylinder. Intentional "dieseling", but the gun was beefed up to take it.

 

[AnaxImperator]

I'm still hoping to see a viable man or vehicle portable rail-gun developed; I know they're pretty close to having one able to be mounted on a ship. IMHO, rail-guns will be the next revolutionary step in projectile weaponry.

actually, i had thought about using gun powder as fuel in automobiles. i thought it might be a good way to get extra horsepoer on demand.

The problem with this is a set volume of gasoline contains much more energy than the same volume of gunpowder.

IIRC I seem to remember an early 19th century internal combustion engine that used black powder as a fuel

Mythbusters busted that one. They tried a couple different engine designs, including a small 4-stroke (IIRC) lawnmower engine. Didn't work.

 

[dagger dog]

Have you checked out the Gyro Jet concept , solid rocket propelled bullets from a handgun, failed marketing attempt from the '60's?