Space Shuttle Solid Rocket Motor Plume Pressure and Heat Rate Measurements

The solid rocket booster main flame deflector at NASA Kennedy Space Center Launch Complex 39A was instrumented to measure heat rates, pressures, and temperatures on the final three space shuttle launches. Because the solid rocket booster plume is hot and erosive, a robust tungsten piston calorimeter was developed to compliment measurements made by off-the-shelf sensors. Witness materials were installed, and their melting and erosion response to the Mach 2, 4000°F, 4 s duration plume was observed. The data show that the specification used for the design of the main flame deflector thermal protection system overpredicts heat rates by a factor of three and underpredicts pressures by a factor of two. The discovery of short-duration heating spikes that occur when aluminum oxide slag solidifies on the main flame deflector explains this heat rate overprediction. This study allows improvement of solid rocket motor launch site and test stand computational fluid dynamics models and the concomitant slag deposition heat transfer models.