Rail Gun Muzzle Velocity Control With High Accuracy

A rail gun can be used as an experimental tool to accelerate small-mass specimens up to 300 m/s to study impact phenomena. In order to obtain comparable and reproducible results, it is desirable to achieve a low statistical deviation of the final velocity. To decrease the deviation during the launch for a railgun, the movement of the projectile is observed along the barrel and the difference between the desired and the measured velocity is calculated. The driving current is then adjusted dynamically by triggering the capacitor modules earlier or later than planned. This paper presents initial experimental results within this study. A light barrier system has been set up to monitor the projectile's position in real time. The special design of the system prevents disturbances caused by magnetic fields and electromagnetic radiation. This is reported in detail. A series of shots was performed under constant conditions to measure the deviation of the final velocity. Launches were performed using the French-German Research Institute Saint Louis's augmented railgun (caliber 15 mm x 15 mm, length 1.6 m), which was supplied by a 38-kJ capacitor bank. The bank consisted of four energy modules, each module containing one capacitor and a thyristor as a switch. The modules could be triggered independently from each other. In the second series of shots, the trigger-time of the last module was varied to investigate the effect on the final velocity. The experimental results are analyzed and discussed.