Force Measurements On Small Caliber Supersonic Projectiles Using an External Force-Torque Transducer

In this work, we present a preliminary study on the use of an external force-torque transducer for the aerodynamic characterization of projectiles in small supersonic wind tunnels. We describe the implementation process of the sensor in our test section, using a 5.56 mm NATO M855 projectile model to carry out a series of experiments where we identify the limitations of different design and flow configurations. We present a feasible design which we then use to investigate the effects of model scale in the measured aerodynamic forces at Mach 2.5. The trends observed in the results demonstrate the non-negligible contributions of the projectile to the total force measurements. Finally, we propose a preliminary force decomposition procedure to isolate the projectile drag, based on scaling arguments and Kármán-Moore theory, with which we recover reasonable agreement in zero-yaw drag coefficient with live firing data from the literature.