VORTEX SHEDDING IN A LARGE SOLID ROCKET MOTOR WITHOUT INHIBITORS AT THE SEGMENT INTERFACES

The internal acoustic response of the Titan IV Solid Rocket Motor Upgr ade (SRMU) is analyzed using pressure oscillation time histories measu red during four static firing tests, Pressure oscillations for other l arge solid rocket motors are caused by vortex shedding at annular inhi bitors and acoustic feedback resulting from impingement of the vortice s on other inhibitors or on the solid rocket motor nozzle. The SRMU do es not have inhibitors, but it is shown that acoustic feedback also de fines its pressure oscillations, Vortices are shed around the cavity b etween the center and aft segments and impinge on the nozzle entrance. The frequencies of the pressure oscillations vary about that of the m otor fundamental acoustic mode and generally agree with a simple empir ical relationship that has been used to model acoustic feedback. The e ffect of the SRMU pressure oscillations on dynamics and control of the Titan IV system is minor.