Burning rate anomaly of composite propellant grains

In this study, characteristics of the burning rate anomaly in composite propellant grains are investigated. The burning rate anomaly has been known as the “midweb anomaly” or the “hump effect.” This paper describes some results of an experimental study on effects of propellant formulations, casting processes, and viscosity of the propellant slurry on the phenomena. According to some past studies, it has been suggested that the geometry of the “isochrone surface” of the propellant slurry affects the local burning rate. To investigate the effect of the isochrone surface, visualization of the isochrone surface in composite propellant grains is carried out. A relation between the geometry and the local burning rate measured in motor firing tests and strand tests is proposed. As a result, besides the common static characteristics of the burning rate anomaly, i.e., the pressure hump effect and the nonisotropic characteristic of the local burning rate, a peculiar burning rate distribution in connection with the isochrone surface is obtained.