Analysis of the second stage of the STAR 28 mm two-stage light gas gun

An engineering model of the second stage operation of the 28 mm two-stage light gas gun at the Shock Technology and Applied Research (STAR) facility of Sandia National Laboratories has been developed. It describes the piston motion and loading of the accelerated reservoir (AR) and the coupled projectile motion. The model was developed to better assess the safety of the AR and to determine the significance of various parameters to the gun performance. Validity of the model is supported by calculated results that compare closely with projectile velocity data over a range of piston masses, piston velocities, and projectile masses and correlate satisfactorily with AR diameter growth data in a typical high-performance test. For this test, bounds on the factor of safety (FS) for the piston velocity are determined to be 1.3 < FS < 1.5. Results indicate that the projectile velocity can be increased and the AR loading reduced by changes in the piston density and break diaphragm opening pressure.