Application of W-band, Doppler Radar to Railgun Velocity Measurements

This paper describes a W-Band Doppler radar system in use at the electromagnetic launch facility at the Naval Surface Warfare Center in Dahgren, VA. Experimental results for a medium caliber railgun launch at 2000 m/s are presented. A discussion of the radar signal characteristics is given and the Doppler velocity profile during launch is computed. The in-bore time history of the launch package derived from the radar system is found to have good agreement with that derived from traditional magnetic field flux sensors (B-dot sensors). Given the increased temporal resolution of the radar system over B-dot measurements, time resolved friction coefficients can be estimated based on launch parameters. Due to the capabilities of the Dahlgren test range, the radar is able to track the projectile for a portion of flight just after the projectile exits the launcher. Drag coefficients for the projectile in hypervelocity free-flight are also presented.