Scale-Model Acoustic Studies—624A SSLV

A 1:33 scale model of the 624A SSLV solid-propellant booster was tested to determine the effects of flame-deflector configuration on launch acoustic levels. Aerothermodynamic and acoustic data were obtained from a series of firings in which exhaust-duct length, liftoff elevation, and exhaust-impingement distance were varied. The covered exhaust duct produces significant reductions in acoustic levels on the vehicle as compared to those occurring on an open flame deflector prior to and during vehicle liftoff. The model acoustic data were scaled in frequency by use of Strouhal numbers and the spectra were compared to predicted and measured data from large booster-engine firings. The relative reductions in sound-pressure levels achieved with the covered exhaust duct were then applied to the predicted launch-vibration environments for specific compartments in the vehicle.