Two-stage light gas guns

Fig. 5. Two-stage light gas gun showing the piston and H projectile where M = propellant charge and 1 = light gas (a), before firing (b), after firing propellant charge (c), as piston nears necked-down mouth of the launch tube (d), after completion of firing cycle. Piston is removed from neck of launch...

Shahinpoor, M., H.S. Lausen, J.L. Wise, J.R. Asay, C.H. Konrad, and R.D. Harday (1985), Ballistics Computer Code Manupulation for Optimal Design and Operation of Two-Stage Light Gas Guns, SNL—Solid Dynamics Department, Quarterly Report, October 1985. 

Impact velocities from about 2 to 6 kms which can produce shock pressures in the 110 GPa range, are routinely achieved with two-stage, light-gas guns. These systems are typically limited to diameters of from 12 to 25 mm. To achieve these velocities, propellant is used to accelerate a large piston which serves to compress a reservoir of helium or hydrogen gas to high pressure. The gas then accelerates the projectile over an acceleration distance of perhaps 25 m. 

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