Space Shuttle Orbiter aerodynamics induced by asymmetric boundary-layer transition

This paper provides the methodology and the results for the investigation of asymmetric boundary-layer transition (ABLT)-induced aerodynamic moments on the Space Shuttle Orbiter during entry. Asymmetric boundary-layer transition, which has been observed from flight data during several Orbiter entries, causes rolling and yawing moments that must be counteracted by aileron deflections and/or reaction control system (RCS) jet firings. These anomalies during Orbiter entry have raised concerns about the understanding of boundary-layer transition and its effect on the Orbiter aerodynamic performance and safety during entry. To address these issues, a method has been developed to compute the yawing and rolling moments induced by asymmetric boundary-layer transition during Orbiter entry. The results have been compared with the current flight-derived ABLT models, and will be used to assist in future mission planning and astronaut training.