Hydrogen fired guns

It seems there are now two or three different ideas about this technology being discussed interchangeably here:

• Light gas guns that use compressed gas to propel the projectile.
• Light gas guns that burn the light gas to propel the projectile.
• Gas fueled guns that use both a gaseous fuel and oxidizer via sudden combustion to propel the 'projectile'.

The last idea is somewhat similar to 'carbide cannons' or 'movie machine guns' I have seen in use, however those two do NOT employ any projectiles in firing. only propelling the burnt and unburnt gasses out rapidly to generate the loud 'bang' and a flame at the 'muzzle'.

Perhaps the middle idea may be a laboratory curiosity as I have never heard of one outside a Laboratory as getting mixed fuel and oxidizer gases to heavily compress before potential self ignition is a problem. Further, such combustion is like a 'detonation' rather than a 'controlled rate burn', very fast and sharp pressure rise to very high values that can over stress the chamber in which it occurs.

A slightly more 'controllable' idea is using liquid fuel injected into a chamber of compressed oxidizer gas. This idea has been very well developed over the last couple of centuries in diesel engines, supercharged spark ignition engines, and experimental cannons.

Chev. William

I can't understand why they would use nitrogen in a light gas gun. As a diatomic molecule, it is just as heavy as carbon monoxide and heavier than water vapor and some other gunpowder gas species. The lab I visited with one of these light gas guns used supercompressed helium. Not as light as hydrogen, so it only got its projectiles to 17,000 fps, but then, helium doesn't become explosive when mixed with air, so you don't have to worry about muzzle blast. It also bears mentioning the gun was 40 feet long and about ten inches in diameter and suspended on air bearings for manipulation. Not exactly a concealed carry candidate.

Regarding Diesel and Hydrogen energy content, keep in mind the numbers assume mixing with enough air to supply the oxygen needed in the reaction, while gunpowder has that built in. Where a kiliogram of smokeless rilfe powder is typically in the range of around 1.8 liters of volume, at one atmosphere of pressure, a kilogram of hydrogen mixed with enough air to combust completely would occupy about 39,550 liters (about 1,400 cubic feet or about 5% bigger than a 10,000 gallon tank). Still, in an equal volume, that mix represents about 1.6 times more energy than powder. The problem then is that hydrogen and oxygen will not be progressive burning, so you would be limited to quantities that could not produce normal rifle velocities without also producing excessive pressures. A second problem is the hyudrogen gas molecules are so small and fast moving that hydrogen will not stay in a metallic cartridge case for very long, so the shooting system has to charge the combustion space immediately before firing. It would more resemble running a motor in that sense.