Update: A Subscale 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 previous work, the design of a subscale solid rocket motor was performed based upon engineering analysis of the interior ballistic process and a series of CFD simulations of the flow field in both the region of the submerged nozzle and the entire subscale motor. This motor design allows for the use of real-time X-ray radiography with a high-resolution image intensifier system to obtain submerged nozzle erosion data. An update on the design and fabrication of this subscale solid rocket motor is presented in the present work. In addition to this, 3D simulation of the internal flow-field of the rocket motor was performed including the effects of liquid alumina droplets. The modeling of the nozzle surface erosion, coupled with the flow field structure, addresses scientific understanding and characterization of the influence of a liquid layer formed due to deposition of Al2O3/Al droplets on the surface of the converging section of the submerged nozzle. Calculations have been performed which compute the accretion rate of alumina onto the nozzle surface, with accretion rates on the order of 20 kg/m 2 -s. As a part of the overall study, we examine several physicochemical processes on the nozzle surface due to the presence of this molten liquid layer. 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 materials.