Monday, March 30, 2009

Should Helium Be Used In Airsoft Gas Blowback Guns?

Given that the laws of thermodynamics dictates that gases of low molecular weight have excellent work function, should Airsoft gas blowback guns use helium instead of Green Gas?

By: Vanessa Uy

It is well known in the Airsoft gaming community that gas blowback guns – especially handgun replica weapons systems – uses refrigerant like gases, like Green Gas and Red Gas as the working substance for these type of guns. But shouldn’t gases with low molecular weight like helium or hydrogen make better gases for use in gas blowback Airsoft weapons systems? After all, our current understanding of the laws of thermodynamics states that gases with very low molecular weights have a very excellent work function when used as the working substance in a typical mechanical system.

Though it never got used as a battlefield weapons system due to it’s relative complexity, the light-gas gun system is a good example of how a working substance of low molecular weight can produce very excellent performance – in projectile velocity terms – when used as a gun propellant. Oddly enough, the mechanical principle of the light-gas gun system is akin to that of a typical Airsoft AEG weapons systems’ piston, cylinder, catcher section, and launch tube set-up.

Operation of the light-gas gun system consists of igniting a conventional powder propellant in the propellant chamber, which forces the pump piston down the pump tube, compressing the helium or hydrogen gas – usually pressurized at 450 to 1200 pounds per square inch before firing the propellant. This gas eventually builds up sufficient pressure to cause the diaphragm to burst. It is the release of this pressure that propels the projectile from the launch tube. The catcher section of the gun serves to limit the forward motion of the pump piston.

Projectile velocities of the light-gas gun system are of the order of 7,000 to 15,000 feet per second, while conventional battlefield guns – like howitzers – are limited to 7,000 feet per second. Although the 7,000 feet per second figure is the sole domain of artillery pieces that fire tungsten carbide or depleted uranium cored disintegrating sabot projectiles, those that fire your typical high-explosive fragmentation projectiles are probably limited to under 5,000 feet per second in their muzzle velocities.

The higher level of performance attained with the light-gas gun system is attributable to the low molecular weight and the correspondingly high sound velocity of the working substance acting on the base of the projectile. These guns are typically used in research labs that investigate the hypervelocity impact damage of meteorites or space debris on satellites and manned spacecraft.

Given that hydrogen has the inherent hazard of flammability and the long term ozone layer and global warming hazards of Green Gas and Red Gas – i.e. HFC-134a and HCFC-22 – are yet to be determined. Even though one cannot directly substitute helium for Green Gas or Red Gas because your typical Airsoft gas blowback mechanical systems are pre-designed to work only with either Green Gas or Red Gas. It looks as if the use of helium as a working substance for Airsoft gas blowback guns has been unfairly overlooked.

Although Green Gas and Red Gas are now readily available in Airsoft shops throughout Southeast Asia, helium tanks typically sold to fill party balloons are more widely available. Also, helium has a greater commercial and industrial incumbency than either Green Gas - a mixture of propane, polysiloxane lubricant and HFC-134a refrigerant – or Red Gas – a mixture of carbon dioxide, nitrogen and the refrigerant HCFC-22. Because it has been sold for a while longer than either pre-packaged Airsoft working substances, plus the laws of thermodynamics proves that helium is a more efficient gas than either Green Gas or Red Gas - mystery of mysteries indeed.