The thermal protection system requirements on the windward pitchplane of a typical shuttle orbiter are evaluated using a recently developed computational procedure. This procedure treats chemically nonequilibrium inviscid and viscous flows for surfaces of arbitrary catalycity. Surface catalycities for typical shuttle materials were evaluated from arc plasma generator data. Computations for the shuttle orbiter demonstrated the significance of entropy swallowing on heat transfer and show that for representative catalycity values, nonequilibrium effects are small though not insignificant. It is shown that the reduced heat transfer rates, caused by surface effects, observed in arc plasma facilities, should be reviewed carefully since these reduced rates will not be as significant for the larger orbiter dimensions.
NomenclatureH T = total enthalpy k w (O) = surface catalycity for O recombination k w (N) = surface catalycity for N recombination M e = boundary-layer edge Mach number MOO = freestream or flight Mach number P = pressure Pt 2 = total pressure behind a normal shock wave q = heat flux cat = heat flux to catalytic surface Re e = Reynolds number based on momentum thickness s = surface or stream wise coordinate / = time C/oo = freestream or vehicle velocity a. = vehicle angle of attack
An optical instrument employing a He-Ne laser light source and a Fabry-Perot interferometer frequency (velocity) filter has been developed and successfully applied to the velocity and intensity measurements of backscattered, Doppler-shifted light signals from individual micron-sized particles in gas-particle flows. Distribution data of particle number flux and signal intensity vs velocity can be obtained at a point in a steady flow over an interval as short as 1 sec. An analytical study of the instrument's response characteristics is presented together with a description of the instrument design. Limited information regarding particle sizes is available from an indirect analysis. Results from laboratory cold flows and hybrid and solid-rocket exhaust flows (solid motors up to several thousand pounds thrust) are compared to the predictions of a constant-lag two-phase flow theory. Analysis of a limited number of solid-rocket test results suggests that the entire particulate mass may be approximated as an equivalent lumped mass that is traveling at the velocity of the largest particles in the flow, a velocity that is measured directly by the instrument.
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