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G. Nellis, F. Dolan, W. Swift, and H. Sixsmith
Creare Inc.
Hanover, NH, USA 03755
S. Castles, and J. Gibbon
NASA Goddard Space Flight Center
Greenbelt, MD, USA 20771
A Single Stage Reverse Brayton (SSRB) cryocooler is planned for installation on the Hubble Space Telescope (HST) during the 1999 servicing mission. The cooler will provide refrigeration to the NICMOS (Near Infrared Camera and Multiple Object Spectrometer) instrument cryostat which is presently cooled by the sublimation of solid nitrogen. A thermal short is causing the solid nitrogen to be consumed more rapidly than expected, reducing the useful life of the instrument to about two years or less. Implementation of the cryocooler will extend the life of the instrument for a period of five to ten years.
Design of the cooler is based on the 5 W 65 K engineering model version presently under life test at the Air Force Research Laboratory at Kirtland AFB. The NICMOS cooler will provide approximately 7 W of refrigeration at 70 K with 300 W of electrical input power. Key components of the cooler are a centrifugal compressor, high effectiveness recuperator, and expansion turbine. Except for external structural features, the compressor and recuperator are identical to their engineering model versions. The expansion turbine is a turboalternator that uses a permanent magnet generator to absorb power from the turbine.
A miniature centrifugal pump circulates cryogenic neon between the cryocooler and the NICMOS cryostat. The neon absorbs approximately 7 W of heat, including parasitic loads, which is transferred to the cryocooler through a heat exchanger called the cold load interface (CLI). At the warm end, the 300 W input power is rejected to a capillary pumped loop and external radiator.
This paper presents a description of the cooler, initial test results, and a summary of planned pre-launch tests.
Cryocoolers 10, pp. 431 - 438, Kluwer Academic, Plenum Publishers, 1999.