Pulse-echo measurements of unsteady propellant deflagration

This article discusses a laboratory test method for the measurement of nonsteady deflagration rates and combustion-stability properties of solid propellants. The method combines ultrasonic pulse-echo measurement, fluidic pressure modulation, and digital signal processing techniques to compute the real and imaginary components of pressure-coupled response functions of solid propellants. A description of the apparatus identifies the major components and their functions. A section on the experimental procedure illustrates the steps necessary to conduct a test, and a section on the data reduction technique describes the sequence of steps employed to compute the nonsteady burn rate and the pressure-coupled response. A detailed implementation of the technique as it applies to two representative tests follows, in which graphs and tables illustrate the intermediate data reduction steps. Details of the evaluation of the uncertainties associated with the technique and the data reduction algorithms are also presented.