Abstract One of the most important characteristics of a space cryocooler is its reliability over a lifetime, typically in excess of 7 years. While design improvements have reduced the probability of mechanical failure, performance degradation directly traceable to internal contamination has been observed across the industry in significant numbers, both in endurance test units and flight units. Therefore, the risk posed by excessive contamination is still a major concern and should be addressed in a consistent standard throughout industry. This paper first describes the cryocooler contamination problem in general terms and then describes one company’s efforts and experiences in addressing and resolving the problems. The general discussion identifies a number of sources of internal contamination, the subsequent degradation and failure mechanisms, and the observed impact to a cryocooler’s operational efficiency. The paper suggests some specific contamination prevention procedures and their resultant beneficial impact on cooler performance. The most common and preventable source of contamination is the actual working gas charge, and through a comprehensive charge, purge, and fill procedure, the risk of even long term contamination can be significantly minimized. One major source of unexpected contamination is from the vendor supplied gas bottles. The addition of an in-line getter or cold trap to the fill lines helps reduce such contamination. Internal contamination sources that slowly release volatile gases can also be a problem. This paper also describes the lessons learned during Raytheon’s Standard Spacecraft Cryocooler (SSC) and Improved Standard Spacecraft Cryocooler (ISSC) development programs in the area of internal contamination, and the subsequent cryocooler gas sample analysis. The exceptionally impressive results before and after the incorporation of identified changes are presented. Based on the authors’ observations, the cryocoolers are much more robust to contamination than expected. Contaminant levels generally have to exceed 100 ppm before noticeable piston-to-cylinder or cold-tip temperature degradation is observed.


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    Titel :

    Space Cryocooler Contamination Lessons Learned and Recommended Control Procedures


    Beteiligte:
    Castles, S. (Autor:in) / Price, K. D. (Autor:in) / Glaister, D. S. (Autor:in) / Gully, W. (Autor:in) / Reilly, J. (Autor:in) / Nast, T. (Autor:in) / Kotsubo, V. (Autor:in)

    Erschienen in:

    Erscheinungsdatum :

    2002-01-01


    Format / Umfang :

    9 pages




    Medientyp :

    Aufsatz/Kapitel (Buch)


    Format :

    Elektronische Ressource


    Sprache :

    Englisch




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