Gasoline-powered machine gun.

[Bud Tugly]

I've been watching Mythbusters and it got me thinking (always a dangerous thing). They tested out a steam-powered cannon (it worked great) and a gunpowder fueled engine (didn't work). Since both gunpowder and gasoline make explosions, could you make a machine gun that used gasoline instead of powder as the propellant?

I visualize a firing chamber with a tiny intake and exhaust valve, an injector system to squirt a drop or two of gasoline in, and a system to rapidly feed in bullets.

Advantages: The bullets wouldn't need casings so they'd be lots lighter than regular cartridges, gasoline burns a whole lot cleaner than gunpowder so fouling of the mechism would be much less, and a gallon of gas can propel a 4000 pound vehicle 20 or more miles so it would last through the firing of one heck of a lot of 1 ounce bullets.

Disadvantages: the mechanism of the firing chamber might be more complicated than a regular gun and you'd have to have ready access to a supply of gasoline (although that wouldn't be a problem in most battlefields).

Has it been tried? Is it a dumb idea?

 

[[Pb]]

The problem, as I see it, would be in compressing the gas and oxygen mixture prior to firing. There might be a way to do it, but it would be complicated.

 

[MachIVshooter]

The problem, as I see it, would be in compressing the gas and oxygen mixture prior to firing. There might be a way to do it, but it would be complicated.

Yup. Igniting the air/fuel mixture at atmospheric pressure would propel the bullet, but not very fast.

You'd esentially have to have a two-cylinder engine with the one cylinder driving it and the other to harness the pressure.

Gunpowder is just more efficient and reliable.

 

[kanook]

Have you ever seen a "spud gun"?

I nice single shot with some modification could be made to use gas or even propane. I've seen paintball guns that use propane as a source of fuel

 

[leadcounsel]

Yeah, you'd need a microscopic combustion engine with dozens, maybe, of small moving parts. Think of your car engine compressed down into the size of a single dice (die). And wouldn't it be vibrating and loud? Unreliable? Need to be cooled? Lots of signifcant problems. And you'd have to carry around a bottle of gas.

Nah- the gunpowder and casing works fine. Admittedly it's getting more pricey to shoot, but I don't think that a gasoline is the answer because that's also in finite supply.

 

[GunTech]

Actually, gasoline contains a lot more energy than gunpowder. There's a reason that the military pursued liquid propellant gun technology for almost 50 years. Only the advent of electromagnetic railguns ended research along these lines.

Cartridges of powder propellant have a lot of other advantages however. They are cheap, easy to handle, rugged and simple.

 

[rcmodel]

http://www.reedjoseph.com/lp_gas_cannons.htm

rc

 

[W.E.G.]

It might work -- after it warmed up.

(insert image of Snuffy yanking on a recoil starter, and trying to hold the choke lever back) while the zombies bear down)

 

[Jaws]

The biggest problem is storage. Do you want to run around on the battlefield with a tank of gasoline or propane on your back?
It's been tested for a long time but storing and handling cased ammunition is less dangerous than storing and handling liquid fuels, specially on the battlefield.
How about cookofs from heating up weapon under sustained fire? Brass cartridges are isolating the powder in small amounts, One cartridge cooks of in your MG is not a big deal. Brass cases also take a lot of the heat from the weapon when they are ejected, so they have a huge effect on keeping the gun cool.
That's why the caseless ammo didn't pick up yet, despite it's nice weight reduction and the amount of money poored into it until now.

 

[Avenger29]

*shudders* from a long memory of "Fun with Two Cycle Engines". No thanks at all.

 

[benEzra]

There are researchers studying something like that, actually, though they're primarily looking at fuels other than gasoline:

http://www3.interscience.wiley.com/journal/109618284/abstract?CRETRY=1&SRETRY=0

http://www.aiaa.org/content.cfm?pageid=360&id=231

http://yarchive.net/mil/liquid_propellant.html

The last one is an interesting read on a variety of related topics.

Interestingly, the now-cancelled Crusader mobile artillery system was originally intended to use a liquid-propellant gun, but it didn't work out; it was delicate and maintenance intensive, and if it malfunctioned, BOOM.

A big issue is that unlike regular gun powder, gasoline requires an external source of oxygen in order to burn. Since you won't be able to cram enough air into a gun's chamber to burn much gasoline (unless the chamber is huge), and most chemical oxidizers aren't stable when mixed with gasoline, you'd have to have a second injection system for the chemical oxidizer. So you don't just need one tank, you need two (assuming you use gasoline). You can get around this by using other fuels. From the last link above:

The specific propellent developed for Crusader is a mixture of HAN
(hydroxyl ammonium nitrate) and TEAN (tri-ethanol ammonium nitrate) in
water. HAN is the oxidizer, and TEAN is the fuel. The water makes it
very insensitive to fast and slow cookoff, bullet impact, and
fragments. It reacts only when under pressure.

An even bigger issue is that a lot of the fuel has to be injected while the projectile is accelerating down the bore. Meaning, really, really high pressure injectors. The Crusader LP system tapped gas pressure from the barrel and used it to inject more fuel; the piston is described as being as big as the breech plug of a 16" naval gun.

On the other hand, if you had a really long barrel, multiple injection points, and suitable fuels, you might could get 5000-6000 fps with relatively low peak pressures. I'll bet it would make a heck of a muzzle flash.

 

[Bud Tugly]

Gasoline certainly explodes without being compressed - compression just makes it more powerful. The firing chamber would also be lots less complex than a car engine since the bullet serves as the piston and there would be no connecting rod or crank. Model airplanes use a very tiny gasoline engine and it could possibly serve as a starting point.

How about a gasoline-powered muzzle loader? Squirt some gas down the tube, ram in the bullet and wadding, and use an electrical spark for ignition. It would be lots cheaper and cleaner to shoot than black powder, although not very traditional.

Sorry about all the silly ideas. Just got my brain shifted into gear and I can't get it to stop. It's all the danged Mythbusters fault. :banghead:

 

[GunTech]

I have a copy of the AIAA book if anyone is looking to buy a copy.