Re-entry vehicles designed for space exploration are usually equipped with thermal protection systems made of ablative material. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple ow chemistry models. In order to obtain better predictions, an appropriate gas ow chemistry model needs to be included in the CFD calculations. Although more arc-jet experimental data is becoming available for model comparison, very little flight data exists for comparison and validation. However, because of the observation mission campaign led by NASA, data is available for the re-entry of the Stardust sample return vehicle, which employed a heat shield constructed of phenolic impregnated carbon ablator (PICA). Using a recently developed chemistry model for ablating carbon-phenolic-in-air species, a CFD calculation of the Stardust re-entry at 71 km is presented. The result demonstrates the need to account for different species in the flow field than the ones composing the pyrolysis gas. It is also shown that the main heat flux reduction phenomenon is through mass diffusion, and not through translational-rotational conduction, as is the case at higher altitude. The flow field solutions are also used to generate nonequilibrium radiation spectra, which are compared to the experimental data obtained during Stardust re-entry by the Echelle instrument. The predicted emission from the CN lines compares quite well with the experimental results, demonstrating the validity of the current approach.

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Conference Proceeding

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Published in the Proceedings of the 42nd AIAA Thermophysics Conference, Paper 2011-3125, p. 1-15.

Copyright © 2011 by Alexandre Martin.

The copyright holder has granted the permission for posting the article here.

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