An Automated Fluid-Structural Interaction Analysis of a Large Segmented Solid Rocket Motor

The ETM-3 motor is basically an RSRM motor with an additional center segment added. The propellant burn rate was lowered to account for the additional surface area of the motor and the nozzle throat diameter was increase. The additional segment also increased mass flow and mach number in the motor. Because of this harsher flow environment, it was thought necessary to chamber the leading edges of every segment and conduct a detailed fluid/structural interaction (FSI) analysis to ensure propellant grain stability against boot-strapping. The analyses showed that the addition of the 3 inch radial by 24 inch axial chamber on the leading edges of the center/forward, center, center/aft, and aft segments was sufficient to give the ETM-3 motor stable grain displacements at much lower than expected propellant moduli. This report documents the FSI analysis work done for ETM-3. The analyses conducted and documented in this report assumed linear elastic material behavior and quasi-steady state fluid behavior without time response in either the structural or fluid models. Thus, the analyses represented only an approximation at a single snapshot in time. This led to selecting the largest chamfer size analyzed herein to get the biggest safety factor against boot-strapping. Presented at the AIAA/ASME/SAE/ASEE Joint Propulsion Conference (39th) held in Huntsville, AL on 20-23 Jul 2003. AIAA-2003-4507.