Continuous measurement of the burning rate of a composite solid propellant

Abstract

A method for continuous, high-resolution measurement of the burning rate of a solid propellant has been devised and used successfully in preliminary tests. The method consists of using a solid-propellant strand as the dielectric material of a capacitor forming a part of a resonant L-C circuit oscillating at a center frequency of 10.7 MHz. The capacitance and resonant frequency of the circuit vary linearly with strand length during burning. This frequency variation, converted to a voltage proportional to the strand length, was electrically differentiated to obtain a voltage directly proportional to the burning rate of the strand. Preliminary tests in a Crawford burner at several different pressure levels indicate good agreement of this capacitance method with the standard fuse wire method of obtaining burning rates. Because of the high sampling frequency, the capacitance method should be applicable to continuous burning-rate measurements in a nonsteady pressure environment.