Recent Orbiter wind tunnel data and flight data have been used to evaluate boundary-layer transition induced by discrete-roughness elements on the Orbiter windward surface. Orbiter flow field calculations have been used to compute transition parameten and disturbance parameters for correlating the results and companng the trends. Existing transition correlations have been modified and applied to the Orbiter. These correlations provide a means to predict transition on the Orbiter given a known

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... olated roughness element. Furthermore, these data and data reduction methods provide information and guidance for the prediction of transition due to &screte-roughness elements on future winged reentry vehicles. Velocity gradient parameter Roughness height Equivalent roughness height Orbiter reference length -107.75 ft fullscale Boundary-layer edge Mach number Displacement thickness Reynolds number Reynolds number based upon conditions at roughness height Nose radius Momentum thickness Reynolds number Edge temperature Wall temperature ~ ~ Copyright 0 1997 by the American Imtute of Aeronautics and Asuonautics, 1%. All nghts reserved.