BOLT-2 Roughness Side Flight Data Results and Analysis

This report provides an in-depth review of the flight data obtained from Side B, also known as the roughness side, of BOLT-2, which was developed and designed to measure the effectiveness of boundary layer trips at hypersonic conditions. Three discrete-roughness trips were implemented on Side B at specific locations, with the necessary sensor layout, to investigate the flight conditions at which they no longer maintained turbulence behind them. All three trips were the same type that were scaled and sized based on predictions of local boundary layer thicknesses to provide the same level of effectiveness. One trip was on the vehicle centerline, where the boundary layer is relatively thick, while the other two were symmetrically located outboard where the boundary layer is much thinner. The relative difference in boundary layer thickness between these locations was roughly on the order of 3-to-1, thus the centerline trip was geometrically about three times larger than the outboard trips. A first order assessment of the Side B flight results is indicated by these three trips forcing transition onset at the same time during flight. The enclosed flight data shows that the performance of each individual trip was nearly identical, with allowances for minor variations attributed to measurement accuracy.