Effects of grain and aft-dome configuration on aft-end SRB internal flows

Abstract

A series of cold-flow tests was conducted to determine the effects of configuration on the aft-end internal flowfield of candidate Space Shuttle boosters. Initially, the effects of Reynolds number were studied in an extension of earlier water flow-visualization tests in a Vs-scale model of the High-Performance Motor (HPM). No significant change in the nozzle-inlet vortex formation previously reported was noted at higher Reynolds number. Changes in aft-dome contour, submerged-nozzle contour, and aft-segment grain design were then evaluated in the water tunnel to aid in the selection of a candidate grain and dome for the Advanced Solid Rocket Motor (ASRM). Models representing the grain at ignition and at 35 s into the firing were fabricated and changes in the flow patterns documented. Using a tapered-grain model with the HPM nozzle/aft dome produced more intense vortex formation and circumferential flows than when a nontapered-grain configuration was employed. Significant changes were observed when the first ASRM nozzle/aft dome was installed with the tapered grain; no circumferential flow was observed when the nozzle was in the unvectored position. In addition, dye placed in the base of the aft dome cleared this region more rapidly than for any other configuration tested. Tests with the redesigned ASRM nozzle/aft dome and aft-slot grain design indicated that this redesigned aft dome led to reduced circumferential flows. The effects of nozzle vectoring on flow character were far less marked with this configuration than for the HPM. These models were then tested in a series of cold-gas tests. Pressure, velocity, and turbulence intensity were mapped near the nozzle entrance plane and in the aft dome. The results of the cold-gas tests showed the same effects of grain/dome configuration as did the observations made in the waterflow tests.