Development of High Velocity Gas Gun With a New Trigger System

Abstract

In development of high performance armor vests, we need to carry out well controlled experiments using projectile muzzle velocity of more than 900 m/sec. After reviewing trigger systems used for high velocity gas guns, this research intends to develop a new trigger system, which can realize precise and reproducible impact tests. A new trigger system developed here is called a projectile trap. A projectile trap is placed between a reservoir and a barrel. A projectile trap has two functions of a sealing disk and triggering without time lag. Polyamidimide was selected for the trap material and dimensions of the projectile trap were determined by numerical analysis for several levels of launching pressure to change the projectile velocity. Numerical analysis results showed that projectile trap designed here could operate reasonably and stresses caused by launching operation were less than material strength. The experiment was carried with nitrogen gas as propellant gas because helium gas is very expensive compared to nitrogen gas. The maximum projectile muzzle velocity was 407.1 m/s with maximum launching pressure of 10.0 MPa. The experimental results on launching pressure well agreed with numerical analysis results. This means that the new trigger system developed in this research can be well designed and controllable through precise machining of a projectile trap. To examine performance of the gas gun with the new trigger system, the muzzle energy was compared between the developed gas gun and an air rifle charged with CO2 gas compressed to 13.8 MPa. The muzzle energy of the air rifle is 34.8 J while that of the developed gas gun is estimated as 42.2 J if the launching pressure is enhanced to 13.8 MPa. The developed gas gun is 1.24 times more powerful than the air rifle. This reflects that the new trigger system developed in this research is superior to the other trigger system in delivering propellant gas energy to a projectile. The developed gas gun can be easily powered up to accelerate a projectile to 1000 m/sec, if the barrel is elongated to 4.2 m and helium gas is used for a propellant gas.