Results of wind-tunnel tests that demonstrate a novel drag reduction technique for blunt-based vehicles are presented. For these tests, the forebody roughness of a blunt-based model was modified using micromachined surface overlays. As forebody roughness increases, the boundary layer at the model aft thickens and reduces the shearing effects of external flow on the separated flow behind the base region, resulting in reduced base drag. For vehicle configurations with large base drag, existing data predict that a small increment in forebody friction drag will result in a relatively large decrease in base drag.
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