Preliminary Assessment of the Use of Heavy Gases in Two-Stage Light Gas Guns

This paper discusses ballistic range testing at muzzle velocities of 0.7 to 2.7 km/s. Herein, we review several techniques for achieving these velocities - starting with the single stage gas gun and the powder gun. These techniques can have velocity limitations, both on the high end and on the low end, very high powder breech pressures, incomplete and inconsistent powder burn and can send unburned powder grains downrange to confound impact data. To try to resolve these issues, it was decided to study the use of the two stage light gas gun operated with a heavier working gas than is normally used. This would have the effect of lowering the usual muzzle velocity range of the two-stage gun using hydrogen to cover the desired low velocity range. Preliminary results are presented from firings with two NASA guns. Twenty-five shots were made with helium and nine shots with argon. Muzzle velocities of 1.1 to 4 km/s were obtained with helium and velocities of 0.7 to 2.7 km/s were obtained with argon. Overall, the heavy gas technique appears quite promising, but more firings are needed to fill out the data base.