This paper describes the development and testing of two advanced cryogenic thermal switch (CTSW) options for use in long-life cryogenic space systems. The principal application for these two CTSW options in such systems is in implementing cryocooler redundancy with a minimum parasitic heating penalty. The two CTSW configurations covered in the paper are a hydrogen gas-gap ( H 2 -GG ) design, flown on STS-95 in October 1998 as part of the CRYOTSU Hitchhiker flight experiment, and a differential thermal expansion (DTE) design. Both options are constructed primarily of beryllium for CTE compatibility with beryllium cryogenic components. The H 2 -GG design utilizes a flat 2-mil gap between two cylindrical beryllium halves that are supported by a thin-walled titanium tube. A highly convoluted stainless steel bellows seals the unit. The H 2 -GG CTSW is nominally “off” (evacuated) until actuated “on” by heating a metal hydride getter, which evolves hydrogen and provides thermal conductance across the gap. The H 2 -GG design has demonstrated an “on” conductance of 1.0 W/K, an “off” resistance of 1000–1500 K/W and a range of operation from 15K–300K. The DTE design, which has just three parts, is very similar to the H 2 -GG design except that a stainless steel tube replaces the titanium tube and the bellows and getter are no longer needed. The DTE CSTW is actuated “on” (both sides cold) by the higher CTE of stainless steel compared to beryllium and actuated “off” by temporarily applying power to a small heater on the stainless steel tube to expand the tube enough to open the gap. After the smaller of the two beryllium parts warms sufficiently, the heater is no longer needed and the DTE CTSW remains “off” (one side cold, one side warm). The DTE design has demonstrated the potential for an “on” conductance greater than 1.0  W/K , an “off” resistance of 1400 K/W and a range of operation from less than 4K to 300K. This paper describes the design of each CTSW option and the testing that was carried out to verify their performance.


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    Title :

    Development and testing of advanced cryogenic thermal switch concepts


    Contributors:

    Conference:

    SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM - 2000 ; 2000 ; Albuquerque, New Mexico (USA)


    Published in:

    AIP Conference Proceedings ; 504 , 1 ; 837-846


    Publication date :

    2000-01-19


    Size :

    10 pages





    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



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