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OTIC FLIGHT DYNAIMICS LABORATORY WRIGHT RESEARCH AND DEVELOPMENT CENTER AIR FORCE SYSPThS COW~hANDThis is a survey paper on the subject of hypersonic boundary-layer transition. Part 1 discusses boundary-layer stability theory, hypersonic boundary-layer stability experiments, and a comparison between theory and experiment. Part 2 contains comments on how many configuration and flow parameters influence transition. Part 3 discusses some additional general aspects of transition. Part 4 discusses problems of predicting transition and comments on three prediction methods. Part 5 contains some general guidelines for prediction methodology. Thus, much hvpersonic transition guidance must be speculated from subsonic and supersonic results and old hypersonic data must be retrieved and re-evaluated. E-1 S4AE AS RPTNot that it helps with the boundarv-layer transition prediction problems, but there is some small gratification in knowing that design uncertainties are been a considerable number of hypersonic transition experiments; however, these data generally provide only parametric trends (e.g. , the effects of nosetip bluntness on transition location). When the only information obtalned is the location of transition it is impossible to determine details of the boundary-layer disturbance mechanisms which caused the transition. In order to obtain fundamental information about hypersonic boundary-layer instability phenomena it is necessary to perform stability experiments which describe the disturbances in the laminar boundary layer prior to transition. It is unfor-tunate that such an important topic as hypersonic stability has received so little attention. -n understanding of hypersonic instability phenomena is __ortant for obtaining a better understanding of hypersonic transition and is esserclal for analytical prediction methods. The following discus.'ion will briefly discuss our current understanding of hypersonic boundary-layer instabilities. (I.b) STABILITY THEORYIt is now generally believed that the onset of boundary-layer turbulence is the result of instability waves in the laminar boundary layer; however, the direct relationship between instability and transition is unknown. Stability theory provides a means of understanding the characteristics of instability waves and, consequently, a better understanding of transition. Numerical solutions of the stability equations can provide important details of boundarylayer instability; such as, the identity of those disturbance frequencies which are stable and those which are unstable, the minimum critical ReynoldR number at which disturbances scart to grow, their growth rates, their return to a stable condition, the particular disturbance frequency which will cbtain the maximum distuibance amplitude, and the effect of various parameters (e.g., Mach number, pressure gradient, wall temperature, etc.) Stability theory can povIde much valuable information about boundary-layer disturbances, but it cannot predict transition. This Is an inportant point.There is no transition 3 t...