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Cryogenic Insulation System for Soft VacuumThe development of a cryogenic insulation system for operation under soft vacuum is presented in this paper. Conventional insulation materials for cryogenic applications can be divided into three levels of thermal performance, in terms of apparent thermal conductivity [k-value in milliwatt per meter-kelvin (mW/m-K)]. System k-values below 0.1 can be achieved for multilayer insulation operating at a vacuum level below 1 x 10(exp -4) torr. For fiberglass or powder operating below 1 x 10(exp -3) torr, k-values of about 2 are obtained. For foam and other materials at ambient pressure, k-values around 30 are typical. New industry and aerospace applications require a versatile, robust, low-cost thermal insulation with performance in the intermediate range. The target for the new composite insulation system is a k-value below 4.8 mW/m-K (R-30) at a soft vacuum level (from 1 to 10 torr) and boundary temperatures of approximately 77 and 293 kelvin (K). Many combinations of radiation shields, spacers, and composite materials were tested from high vacuum to ambient pressure using cryostat boiloff methods. Significant improvement over conventional systems in the soft vacuum range was demonstrated. The new layered composite insulation system was also shown to provide key benefits for high vacuum applications as well.
Document ID
19990062736
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Augustynowicz, S. D.
(Dynacs Engineering Co., Inc. Cocoa Beach, FL United States)
Fesmire, J. E.
(NASA Kennedy Space Center Cocoa Beach, FL United States)
Date Acquired
September 6, 2013
Publication Date
June 1, 1999
Subject Category
Nonmetallic Materials
Meeting Information
Meeting: Cryogenic Engineering
Location: Montreal
Country: Canada
Start Date: July 12, 1999
End Date: July 16, 1999
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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