An investigationof the use of aerogel beads as thermal insulation for cryogenic applications was conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center.https://ntrs.nasa.gov/search.
This paper presents the development of a flexible, easy-to-use superinsulation. The innovative material system employs ultralow density aerogels within a flexible fiber rnatrix for minimum heat transfer and maximum applicability and durability. The core of the system is aerogels formed at the fiber-fiber contacts of the matrix, forcing solid conduction to occur through the aerogels. This composite configuration improves both the ease of handling aerogels and the overall thermal resistance. The close-packed structure of the aerogels also eliminates the open spaces in the fiber rnatrix and thereby reduces gas conduction.Excellent thermal resistance was achieved for both evacuated and nonevacuated insulation systerns while maintaining structural flexibility. The aerogels were also produced in an opacified fiber rnatrix. Testing of these composites indicated a significant inhibition of radiation in the infrared range. Thermal performance was measured by transient heat flux and liquid nitrogen boiloff methods. The apparent thermal conductivity of the silica-aerogeVfiber composite was lower than 1 milliwatt per rneterkelvin (mW/m-K) at a high vacuum Ievel [below 1x10· 5 millibars (mbar)] and below 10 mW/m-K in ambient pressure nitrogen (boundary temperatures were approxirnately 77 K and 280 K for all tests). Performance was found to be insensitive to residual gas pressure up to a vacuum Ievel of about 1x10· 1 mbar. Aerogel-based superinsulation systerns have been produced and tested in blanket, sheet, and clarnshell forrns for use on a variety of cryogenic equipment.
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