A flow visualization study was conducted to analyze flow characteristics inside the solid rocket motor (SRM) used on the NASA space shuttle. The objective of this investigation was to determine whether the internal flow structure could adversely affect the nozzle/case joint and the surrounding casing. Also, it was hoped to learn more about causes of low level acoustic pressure oscillations observed during SRM test firings. The SRM was simulated by water flow through a plexiglas model mounted in a water tunnel. Dye and hydrogen bubble visualization techniques along with hot water analysis methods were used to detect flow patterns. Visual results recorded on video tape indicated strong circumferential and recirculation flows around the nozzle. Vortex formation near the nozzle inlet was also observed and was the prime focus of this investigation. Because the nozzle inlet geometry was very similar to an aircraft engine inlet operating close to the ground, vortices seen in this investigation were believed to behave like vortices seen around engine inlets. Based on the results from this investigation and the results of previous engine inlet vortex studies, it was concluded that the nozzle vortices could be the excitation source of SRM pressure oscillations. / Master of Science