Surface Heating and Boundary-Layer Transition on a Hypersonic Inflatable Aerodynamic Decelerator

Abstract

The aerothermodynamic environment of a hypersonic inflatable aerodynamic decelerator with a flexible thermal protection system has been investigated through wind-tunnel testing. Boundary-layer transition onset locations and surface heating distributions were measured using global phosphor thermography on deflected, solid-surface models representative of a hypersonic inflatable aerodynamic decelerator aeroshell with a flexible surface. Data were obtained at Mach 6 for a wide range of surface deflection heights, angles of attack, and freestream Reynolds numbers. The surface deflections resulted in earlier boundary-layer transition onset and higher heating levels than for a smooth-wall surface, with the greatest effects occurring on the leeward side of the aeroshell. The heating augmentation and transition onset data were correlated using flowfield properties obtained from a complementary computational study. A method was developed to estimate flexible thermal protection system deflection effects using these correlations along with smooth-wall flowfield predictions. This method was validated through comparisons to the wind-tunnel data and then used to generate postflight predictions for aeroshell heating levels of the Inflatable Reentry Vehicle Experiment flight-test program. The results of this study provide a means for estimating flexible thermal protection system deflection effects for future flight tests as well as an experimental database for use in the development and validation of computational methods for simulations of hypersonic inflatable aerodynamic decelerator aerothermodynamic environments.