Internal flow investigation of an aft finocyl grain configuration in a solid rocket motor

Cold-flow tests were conducted in mediums of air and water to investigate the internal flow field about the nozzle region of a proposed solid rocket motor (SRM) configuration that would potentially replace the current external boosters on NASA's Space Shuttle. One-eighth-scale clear acrylic models of the proposed submerged aft-dome and aft finned grain elements were constructed to simulate the aft segment of the SRM at ignition and 35 seconds into the firing sequence. Pressure, velocity, and turbulence profiles were obtained during cold air testing, while air bubbles and dye were used for flow visualization during water tunnel testing.

The flow visualization experiments indicated the presence of strong inlet vortices, alternating vortex shedding from both grain models' fins, circumferential flow in the aft-dome and around the nozzle, and recirculatory flow in the aft-dome and near an upstream portion of the 35-second grain model. Data acquired during cold air testing showed a turbulent low-velocity flow field in the aft-dome for both grain models. With respect to pressure and mean velocity virtually the entire nozzle/aft-dome region exhibited a minimal sensitivity to nozzle vectoring.