Ultrasonic measurement of solid propellant burning rate

Considering the inadequacy of current methods for measuring the burning rate of solid propellants, an ultrasonic device has been developed that measures the grain thickness at a rate up to 5000 Hz. Satisfactory results have been obtained on specimens up to 40 mm thick in steady or slowly varying conditions, such as erosive combustion. Composite, double base and autopyrolyzing propellants have been tested in various temperature and pressure conditions, and intermediate materials between grain and transducer have been determined. The precision during fast transient phases or unsteady combustion is still wanting, but this drawback may be overcome by further studies, especially on signal processing.