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Permeability of Rigid Fibrous Refractory InsulationsRigid fibrous refractory insulations (TPS tiles) are integral components of many spacecraft thermal protection systems. These materials are composed of refractory fibers With diameters on the order of 1 to 15 micrometers. They are lightweight and have an open, highly porous microstructure. Typical densities are less than 500 kilograms per cubic meters, and porosities generally exceed 0.8. Because of their open porosity, these materials are permeable to gas glow. There are numerous instances in which internal gas transport in a thermal protection system could be important; examples include the penetration of hot boundary-layer gases into the insulation, the flow of decomposition (pyrolysis) products from the interior, the use of convective flows to mitigate ice formation caused by cryopumping, and the design of refractory vents for pressure equilibration during atmospheric entry. Computational analysis of gas flow through porous media requires values of permeability which have not previously been available for the rigid fibrous insulations used in thermal protection systems. This paper will document measurements of permeability for a variety of insulations from NASA's LI, FRCI, and AETB families of lightweight ceramic ablators. The directional anisotropy of permeability and its dependence on gas pressure and material density will be presented. It will be shown that rarified-flow effects are significant in the flow through such materials. Connections will be drawn between the insulation microstructure and permeability. The paper will also include representative computations of flow through rigid fibrous insulations.
Document ID
20020039971
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Marschall, J.
Milos, F. S.
Rasky, Daniel J.
Date Acquired
August 20, 2013
Publication Date
January 1, 1996
Subject Category
Nonmetallic Materials
Meeting Information
Meeting: AIAA 32nd Thermophysics Conference
Location: Atlanta, GA
Country: United States
Start Date: June 23, 1997
End Date: June 25, 1997
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
PROJECT: RTOP 242-80-01
CONTRACT_GRANT: NAS2-14031
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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