For the past years, a significant effort has been performed at the Jet Propulsion Laboratory to characterize commercial-off-the-shelf (COTS) Pulse-tube cryocoolers for use in cost-effective spaceflight applications. This has resulted in the selection of the Thales LPT9310 cryocooler for the ECOSTRESS instrument that will fly on the Japanese Experiment Module – Exposed Facility (JEM-EF) of the International Space Station. The Thales LPT9310 cryocooler nominally provides over 4 W of cooling capacity at 80 K, and has been produced in large quantities with a proven capability of multi-year continuous operation without any instances of cooler failure. However, this capability has only been proven in terrestrial (commercial) applications. In order to provide sufficient justification for using an off-the-shelf cooler for a flight application, additional tests have been performed on the delivered flight coolers, to attain a sufficiently controlled level of quality while leveraging the heritage of the COTS cooler. The test program philosophy will be explained, and results will be discussed. Restrictions in both the available electrical power and the heat exchanger fluid inlet temperature to the instruments onboard the JEM-EF eroded the performance margin book kept for the cryocoolers, prompting the need to find more efficient operating cryocoolers. Thales Cryogenics responded with an upgrade to the LPT9310, replacing the stainless steel pulse tube with titanium alloy, and a re-optimization of the regenerator matrix for 60K while leaving the baseline, qualified design parameters intact. The resulting performance enhancement from the additional cryocooler efficiency at lower temperatures will be presented.
R. Arts, J. Mullié, D. Johnson (1), I. McKinley (1), J. Rodriguez (1), T. Benschop.
Thales Cryogenics B.V., Eindhoven, The Netherlands
(1) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA