High Capacity Flexure Bearing Stirling Cryocooler On-Board the ISS

Abstract

A high capacity Stirling cryocooler has been demonstrated at Development Model level during the year 2001 under AL/DTA and THALES Cryogenics co-funding. This development is based on a commercially-off-the-shelf LSF9320 type cryocooler from THALES Cryogenics (flexure bearing compressor and a standard wearing Stirling cold finger). It is now featuring a dual opposed piston compressor modified in order to drive pneumatically a Stirling cold finger also implementing flexure bearing technology. The pneumatically driven cold finger does not use any motor to obtain the movement and correct phase shift between the Stirling displacer and the pressure wave. The absence of this motor enhances the reliability of the system and simplifies the electronic control required to drive the system. This reliable and powerful cooler concept has been selected as the cooling system for the ESA / CRYOSYSTEM vial freezers to be delivered by AL/DTA to ASTRIUM for use on board the International Space Station in 2006. The CRYOSYSTEM is a set of facilities for ultra-rapid cooling, preservation and storage of biological samples and protein crystals at-180°C. The actual performances are presented for various water heat sinking locations taking into account the benefit of the Medium Temperature Loop (MTL) available on-board. Future performance improvements are discussed.