Design of a Solid Rocket Motor for Characterization of Submerged Nozzle Erosion

Abstract

Current understanding of physical and chemical processes involved in the erosion of submerged nozzles by highly-aluminized solid propellants is limited. The ability to predict the surface erosion rate of a given carbon-cloth phenolic (CCP) nozzle material is very important for the future design or modification of large solid rocket boosters for space launch applications. Although current erosion codes provide engineering accuracy for nozzle throat erosion rates, calculated rates for the forward surfaces of the submerged nozzle can vary significantly from observed values. The overall objective of this research study under the NASA Constellation University Institutes Project (NASA-CUIP) is to improve the understanding of nozzle erosion and related phenomena. In this work, the design of subscale solid rocket motor was performed based upon engineering analysis of the interior ballistic process and a series of CFD simulations of the flow and heat transfer processes in the region of the submerged nozzle. This motor design allows for the use a realtime X-ray radiography with a high-resolution image intensifier system to obtain submerged nozzle erosion data. From the CFD simulations, the maximum accretion rate of liquid alumina droplets was found to have a level of ~10 kg/s-m 2 in the nose-cone region. Elevated accretion rates in the submerged section of the nozzle were calculated and attributed to the impact of larger particles with higher inertia. These large particles could not follow the combustion product stream to flow out of the nozzle. Development of thermal waves in both the liquid film and the CCP material was investigated. Results showed that their interface temperature can reach 3,000 K in about 1 s. Future test results from this newly designed rocket motor will be highly beneficial for model validation as well as attaining in-depth understanding of interactions between the liquid alumina and nozzle material.