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Air Radiation from Nonequilibrium Wakes of Blunt Hypersonic Reentry Vehicles
RAND CORP SANTA MONICA CA
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The wakes of reentry vehicles at altitudes of 100,000 ft or above will not be in chemical equilibrium. Under these conditions the wake radiation cannot be obtained from the ordinary equilibrium calculations, but a detailed study must be made of the chemical kinetics of the nonequilibrium wake. This memorandum presents the results of such a study for the case of a blunt, nonablating vehicle. Knowledge of the important chemical reactions for a pure air wake is fairly complete. However, large uncertainties exist with respect to hypersonic turbulence. For that reason, two recently proposed models of the turbulent mixing process are used in this memorandum the inviscid random convection model, and the homogeneous mixing model. These two models give radiant intensities for the various chemiluminescent reactions that differ as much as several orders of magnitude. This large difference is another illustration of the importance of increasing our knowledge of hypersonic turbulence. The radiation estimates presented here show that the nonequilibrium wake radiation in the UV, visible, and near IR should dominate the gas cap and surface radiation at altitudes above about 100,000 ft.
APPROVED FOR PUBLIC RELEASE