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Radiation Measurements in Simulated Ablation Layers

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Final rept. 1 Jul 2009-30 Jul 2010

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In this study, radiation in ablating shocklayers over a scale Stardust model at 9 kms was measured during the 80 microsecond steady test flow produced in a high enthalpy super-orbital expansion tunnel. The presence of an ablating shock layer when an epoxy coating is used with air and nitrogen test gases is shown by spectrometric and high speed camera data, and is in agreement with previous experimental results. Shock layer radiation is found to be strongest in the UV and visible portions of the electromagnetic spectrum, in both ablating and non-ablating shock layers. Shock layer radiation is greatly increased in ablating shock layers than in non-ablating shock layers when both air and nitrogen test gases are used. A nitrogen test gas is thought to produce a higher temperature shock layer than when air is used, implying that oxygen in air has a cooling effect on shocklayer radiation, due to the dissociation of the oxygen molecules which occurs. Shocklayer radiation in the near-IR is far weaker than that in the UV and consists of atomic, rather than molecular, transitions. As such, no distinct ablation layer is visible in the IR spectral data, however there is a doubling in radiance in the presence of an epoxy coating.

Subject Categories:

  • Fluid Mechanics
  • Mechanics
  • Thermodynamics

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