Blunt-Body Entry Vehicle Aerothermodynamics: Transition and Turbulent Heating

Recent, current, and planned NASA missions that employ blunt-body entry vehicles pose aerothermodyamic problems that challenge state-of-the-art experimental and computational methods. The issues of boundary-layer transition and turbulent heating on the heat shield have become important in the designs of both the Mars Science Laboratory and Crew Exploration Vehicle. While considerable experience in these general areas exists, that experience is mainly derived from simple geometries; e.g., sharp-cones and flat-plates, or from lifting bodies such as the Space Shuttle Orbiter. For blunt-body vehicles, application of existing data, correlations, and comparisons is questionable because an all, or mostly, subsonic flowfield is produced behind the bow shock, as compared with the supersonic (or even hypersonic) flow of other configurations. Because of the need for design and validation data for projects such as Mars Science Laboratory and Crew Exploration Vehicle, many new experimental studies have been conducted in the last decade to obtain detailed boundary-layer transition and turbulent heating data on this class of vehicle. In this paper, details of several of the test programs are reviewed. The laminar and turbulent data from these various test are shown to correlate in terms of edge-based Stanton and Reynolds number functions. Correlations are developed from the data for transition onset and turbulent heating augmentation as functions of momentum thickness Reynolds number. These correlations can be employed as engineering-level design and analysis tools.