Ultrasound measurement method: Errors, noise, and sensitivity

At the National Center of Aerospace Research (ONERA), the burning rate of solid propellants has been determined by means of an ultrasound technique for many years. This paper presents the results obtained on composite propellants for different initial pressures and temperatures, which allow one to discuss the advantages and limitations of the method in terms of the measurement possibility and accuracy. The sensitivity of propagation of ultrasound waves to pertinent physical parameters or operating conditions is illustrated. The errors induced by inadequate corrective terms taken into account in the measurement theory, the effect of the electronic noise of the equipment, and the procedure of differentiating experimental data are shown. Selecting suitable operating conditions allows one to reduce the instrumental error down to 1% of the burning-rate value. Though the ultrasound method is not absolutely universal and perfect, the quality of the data obtained is good enough to be noted.