Propellant Burning Rate Uniformity Identified by Ultrasonic Acoustic Emissions

Abstract

The objectives of the study were to develop a methodology for measuring solid propellant burning rates and burning rate nonuniformities at high pressures. Burning rate variations of nitrocellulose-based propellants (Ml and M26), burning at pressures between 10,000 and 40,000 psi, are recognized by examining the level of the combustion-genera ted acoustic emissions. Multiperf orated propellant grains are burned lengthwise (1 to 1.5 cm) and the rms levels of ultrahigh-frequency acoustic emissions are recorded. The burning rate variations of singlebase propellants are attributed to incomplete dispersion of fibrous nitrocellulose. The double-base propellants produced neither irregularities in their acoustic emissions nor unusual variations in burning rate. These uniformities are attributed to the nitroglycerin, which acts to disperse the nitrocellulose and to enhance burning rate.