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Modeling of the Ablation of Fibrous Materials in the Knudsen RegimeDuring atmospheric entry of planetary probes, the thermal protection system (TPS) of the probe is exposed to high temperatures under low pressures. In these conditions, carbonous TPS materials undergo gasification in the Knudsen regime leading to mass loss and wall recession called ablation. This work aims to improve the understanding of materiaVenvironment interactions through a study of the coupling between carbon dioxide transport in the Knudsen regime, heterogeneous oxidation of carbon, and sutface recession. A 3D Monte-Carlo simulation tool is used for this study. The fibrous architecture of the materiils, consisting of high porosity random array of carbon fibers, is numerically reproduced on a 3D Cartesian grid. Mass transport in the Knudsen regime from the boundary layer to the surface, and inside this porous material is simulated by random walk. A reaction probability is used to simulate the heterogeneous oxidation reaction. The surface recession is followed by front tracking using a simplified marching cube approach. The output data of the simulations are ablation velocity and dynamic evolution of the material porosity. A parametric study is carried out to analyze the material behavior as a function of Knudsen number for the porous media (length of the mean free path compared to the mean pore diameter) and the intrinsic reactivity of the carbon fibers. The results enable extrapolation of laboratory experimental data to actual entry conditions.
Document ID
20090027646
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Lachaud, J.
(NASA Ames Research Center Moffett Field, CA, United States)
Mansour, N. N.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 24, 2013
Publication Date
August 17, 2008
Subject Category
Composite Materials
Report/Patent Number
ARC-E-DAA-TN110
Meeting Information
Meeting: The Nineteenth International Symposium on Transport Phenomena
Location: Reykjavik
Country: Iceland
Start Date: August 17, 2008
End Date: August 21, 2008
Sponsors: Iceland Univ.
Distribution Limits
Public
Copyright
Other

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