Accession Number : ADA307679

Title :   Measurement of Optical Radiation from the Wake of Ablating Blunt Bodies in Flight at Speeds up to 10 KM Per Second.

Descriptive Note : Technical note,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCH CENTER

Personal Author(s) : Stephenson, Jack D.

PDF Url : ADA307679

Report Date : APR 1965

Pagination or Media Count : 53

Abstract : Optical wavelength radiation from the wakes of small gun-launched models (spherically blunted bodies) has been measured at speeds from 5 to 10 km/sec and at stream densities from 0.001 to 0.2 atmosphere. Results indicate that radiation in the wavelength range, 0.2 to 1.0 micron, is caused primarily by the presence of ablation material in the wake. The radiation intensity and spectral quality differ considerably among the various plastic materials tested (a polycarbonate, polyethylene, an epoxy, and polymerized formaldehyde). For conditions at which a majority of the data were obtained, the peak radiant intensity from the wake varied directly with stream density and approximately with the 7.5 power of the flight velocity. The variation of intensity of the wake radiance with downstream distance along the wakes of polycarbonate models, following the region of peak intensity, could be approximated by exponential decay functions. The decay rates varied with the square root of the stream density. When the intensity of the wake radiation is high, the radiative heat load on the body base can be significant. Results of calculations of heating rates on the model base are presented and relations for scaling heating rates are discussed.

Descriptors :   *WAKE, *THERMAL RADIATION, HEAT TRANSFER, ABLATION, OPTICAL PROPERTIES, ULTRAVIOLET RADIATION, ATMOSPHERE ENTRY, SHOCK WAVES, BOUNDARY LAYER, RADIATIVE TRANSFER, POWER SPECTRA, MASS FLOW, FLOW FIELDS, RADIANCE, VISIBLE SPECTRA, AEROTHERMODYNAMICS, FREE STREAM, EPOXY RESINS, THERMAL STRESSES, POLYCARBONATES, BLUNT BODIES, GUN LAUNCHED, FORMALDEHYDE, HYPERSONIC FLOW, POLYETHYLENE, RADIANT INTENSITY, RADIANT HEATING, RADIANT FLUX DENSITY.

Subject Categories : Fluid Mechanics
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE