On parameters influencing the wake flow instabilities behind a discrete roughness element on a generic re-entry capsule

During the re-entry into Earth’s atmosphere the thermal protection system (TPS) of a re-entry capsule has to withstand very high heat loads. Due to a lack of understanding of the physics of laminar-turbulent transition on such blunt vehicles, the design philosophy so far assumed a fully turbulent flow in flight at all times. This conservative design should be replaced by considering the transition onset location for future returning space vehicles, supported by methods based on stability theory and transient growth considerations. Discrete surface inhomogeneities such as attachment-point cavities, compression pads, gaps or steps between heat shield tiles or unevenly ablated TPS material can lead to premature laminar-turbulent transition downstream of the protuberance element (the type of transition investigated in the present study)