Design of a Novel Technique to Measure In-Situ Gas Gun Projectile Flight Concentricity

Positional accuracy of gas gun projectiles is crucial for mitigation of potential catch tank damage and for the guarantee of personnel safety. For the Chamber 9 gas gun facility at Los Alamos National Laboratory, significant gun damage could jeopardize the core mission of the facility. For a set of experiments to be conducted at this facility, a new projectile was designed with uncertain flight characteristics. A novel way to measure the in-situ concentricity of the projectile was devised. Using an additively manufactured target fixture, the system can measure all 6 degrees of freedom of the projectile as it flies using an arrangement of 8 photonic doppler velocimetry probes. The concentricity measurement is obtained using an array of these probes measuring the point at which edges of the projectile pass known points in space. This, combined with data gathered of the projectile tilt as it impacts a known surface, allows the precise special coordinates of the projectile to be determined and used for shot performance evaluation. Three shots on the two-stage gas gun were completed with this diagnostic, producing a high confidence in the stability of the flight characteristics of this new projectile design.