BOLT-II Roughness Side Flight Results

The focus of this report is to provide a review of BOLT-2 roughness data obtained during flight. The BOLT-2 roughness experiment was designed to investigate discrete trips based on the diamond configuration, which has been shown to be an efficient vortex generator and boundary-layer trip from extensive ground-based testing. There were three trip locations chosen for the flight test, and their size (height and width) was tailored/scaled for the local boundary-layer thickness, one on the vehicle centerline and two identical trips near the swept leading edges. Details about the flight vehicle design, instrumentation, and best estimated trajectory are discussed. The thermocouple data are the primary data used to define the transition behavior induced by the discrete trips. Boundary-layer transition onset times, derived from the surface heating analysis of the thermocouple data, provide an assessment of the performance of the discrete trips. All three trips were sized to trip the boundary layer at the same time based on a previous ground test campaign. The present analysis indicates that the discrete trips performed as expected, thus validating the results obtained from the wind tunnel and the approach used to size the trips for flight.