An innovative concept utilizing the natural porosity of refractory-composite materials and hydrogen coolant to provide CONvective and TRANspiration (CONTRAN) cooling and oxidation protection has been numerically studied for surfaces exposed to a high heat flux, high temperature environment such as hypersonic vehicle engine c0mbustor walls. A boundary layer codc and a porous media finite difference code were utilized to analyze the effect of convection and transpiration cooling on surface heat flux and temperature.The boundary layer code determined that transpiration flow is able to provide blocking of the surface heat flux only if it is above a minimum level due to heat addition from combustion of the hydrogen transpirant.The porous media analysis indicated that cooling of the surface is attained with coolant flow rates that are in the same range as those required for blocking, indicating that a coupled analysis would be beneficial.

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The paper reviews a recent study to identify practical, highly durable, alternate t~erma1 protection systems for the Shuttle Orb1ter and presents a status report on alternate TPS technology developments. The study identified candidate concepts, assessed the impact on the Shuttle Orbiter performance, life cycle cost, and risk and defined technology advances required to bring the selected TPS to operational readines~. Within the study guidelines the "best" system 1S a blend of mechanically attached metallic and carbon-carbon TPS concepts. These alternate concepts offer significant improvements in durabi1ity.and are mass competitive wi~h the. current ceramic tile reusable surface tnsu lat t on. Programmatic analysis indicates that, with a?equate resources, approximately five years are requ1red to bring the concepts to operational readiness.