X-33 hypersonic boundary-layer transition

Boundary-layer and aeroheating characteristics of several X-33 configuratio ns have been experimentally examined in the NASA Langley Research Center 20 -Inch Mach 6 Air Tunnel. Global surface heat transfer distributions, surfac e streamline patterns, and shock shapes were measured on 0.013-scale models at Mach 6 in air. Parametric variations include angles of attack of 20, 30 , and 40 deg; Reynolds numbers based on model length of 9 x 10(5) to 6.6 x 10(6); and body-flap deflections of 0, 10, and 20 deg. The effects of discr ete and distributed (in the form of wavy wall bowed panels) roughness on bo undary-layer transition, which included trip height, size, location, and di stribution, both on and off the windward centerline, were investigated. The discrete roughness results on centerline were used to provide a transition correlation for the X-33 flight vehicle that was applicable across the ran ge of reentry angles of attack. The attachment line discrete roughness resu lts were shown to be consistent with the centerline results because no incr eased sensitivity to roughness along the attachment line was identified. Th e effect of bowed panels was qualitatively shown to be less effective than the discrete trips; however, the distributed nature of the bowed panels aff ected a larger percent of the aft-body windward surface than a single discr ete trip.