Characterization of the Interior Ballistics of a Single-Stage Air Cannon for Free-Flight Projectile Testing

Author(s):

Macs Brown, Daniel Everson, and Edward Bukowski

Abstract:

The Single-stage Air-Initiated Launcher (SAIL) was developed to enable precise, repeatable free-flight projectile testing for ARL research. This report presents a comprehensive assessment of SAIL’s interior ballistics, combining theoretical modeling and experimental measurements. Simplified Newtonian models, which assume ideal gas expansion and neglect valve dynamics, were used to predict muzzle velocity but consistently overestimated performance. Empirical testing with mass simulant slugs, high-speed video, Doppler radar, and on-board recorders (OBRs) revealed that SAIL’s piston valve delivers rapid pressure rise and transient acceleration spikes, with peak in-bore accelerations up to 30% higher than predicted by tank pressure alone. OBR data confirmed oscillatory forcing pressures at the projectile base, attributed to compression waves in barrel dead volume. These results demonstrate that valve dynamics and system geometry significantly influence air cannon performance, and direct measurement is essential for accurate characterization. OBR-equipped slugs proved effective for rapid, reliable interior ballistics assessment, supporting ongoing research and system optimization.