Actively controlling the muzzle velocity of a railgun

The muzzle velocity variation is a parameter of many kinds of accelerators. Actively reducing this value is achieved by observing the motion of the accelerated object during launch and by adjusting the propelling force to achieve the desired velocity. Applying this method to classical gas guns requires a controllable energy source. Experiments with Busy Lizzie type gas-driven accelerators resulted in limited success due to severe energy transfer and timing problems. The railgun overcomes these limitations as it uses an electromagnetic field as propellant being able to transport power with almost the velocity of light. Using multiple independent capacitor modules feeding the railgun enables a flexible release of energy. Results are presented from experimental investigations on the control of the acceleration in an augmented railgun. The observation of the accelerated object's motion is performed using a light barrier system. The output signal is read by a micro-controller that decides at which points in times the capacitor modules will be switched on based on a control algorithm. It is shown that the muzzle velocity variation can be reduced by shifting the switch-on points in time of the capacitor modules.