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 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 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 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 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 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 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.
Development and testing of advanced cryogenic thermal switch concepts
SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM - 2000 ; 2000 ; Albuquerque, New Mexico (USA)
AIP Conference Proceedings ; 504 , 1 ; 837-846
19.01.2000
10 pages
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
Development and Testing of Advanced Cryogenic Thermal Switch Concepts
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