Experiments were performed in the T4 free-piston reflected shock tunnel to explore the transition process of hypervelocity boundary layers. The experiments took place on a 1000 mm long × 300 mm wide flat plate with a sharp leading edge at conditions that correspond to the post 6° forebody shock conditions for flight at Mach 12. A streamwise row of thin-film heat transfer gauges along the centerline of the plate was used to determine the state of the boundary layer. It was found that without any boundary layer trips, the boundary layer remained laminar for the entire length of the plate. Multiple combinations of trip geometry and size were then used in an attempt to force the boundary layer into turbulence. The most successful geometry was the diamond trip configuration which although did not act as an effective trip, for values of k/δ ＞ 1, transition was observed after a period of relaminarization.
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