Ultrasound measurements of solid propellant burning rates: Theory and application

This paper reviews the development of a system for precisely measuring the instantaneous regression rate of a solid propellant under both steady-state and transient conditions using an ultrasound technique. Physical effects that degrade the ultrasound measurement, including attenuation in the solid, surface roughness, temperature profile in the solid, and diffraction effects are discussed. A measurement model is being developed to help account for these effects, with the goal of moving beyond simple regression rate measurements to obtaining information about the surface structure of the propellant while it is burning. Measurements from steady-state and transient experiments involving both non-aluminized and aluminized propellants are presented. Measurements of pressure effects and acoustic attenuation of the propellants, which will be useful in developing the measurement model, are also presented.