Long Duration Exposure Facility
(LDEF) Archive System

NASA Langley Research Center
Hampton, Virginia

Materials


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Interior Hardware
As part of Materials Special Investigation Group (MSIG) activities, Boeing Defense and Space Group studied selected interior materials from LDEF. Their results are contained in the report, Analysis of Selected Materials Flown on Interior Locations of the Long Duration Exposure Facility, NASA CR-4586, April 1994, and is summarized here.

The interior of LDEF contained heat shrink tubing, fiberglass shims, nylon wire harness clamps, and silver-coated hex nuts. These materials were subjected to the vacuum of space, some degree of thermal cycling, and intermittent exposures to external environmental factors at some locations. Post-retrieval examinations of this hardware revealed that it was, generally, in excellent condition and it performed there functions as designed. Exposure to the vacuum of space and mild thermal cycling resulted in outgassing of some materials. Localized contamination was observed on some interior hardware.

The following specific conclusions regarding the interior hardware was evident:
  • KaptonTM thermal-control blankets used on the interior facing sides of the experiment trays appeared to be in excellent condition upon retrieval.
  • The total mass loss (TML) and collectable volatile condensable matter (CVCM) measurements of the structure facing and interior facing side of the heat-shrink tubing had different post-flight properties when comparing the leading and trailing locations with those on the side and edge locations. The flight versus non-flown material had different TML values, while the results or CVCM values had a much lower level of confidence becasue the data was from different populations. The lower confidence value for the CVCM data may be due to the moisture that the flight samples absorbed upon retrieval prior to testing.
  • The TML data from the composite shims indicates that there are significant differences between the leading- and trailing-edge locations with specimens from other locations, and between the flight and ground samples.
  • A variety of different tests were conducted on the nylon wire bundle clamps which showed no significant differences in pre- and post-flight properties other than those attributed to random variations in the material. The maximum changes detected had no real effect on the performance of the clamps.
  • Silver-plated nuts from the intercostal clips showed no erosion or degradation of the protective silver coating. However, the nuts were tarnished, with the amount and color of the tarnish varying over each nut and between nuts. The tarnish consisted of silicone and silica/silicates from the decomposition of silicone and of amide material which may have originated from urethane paints.
  • A principal lesson from LDEF is that properly selected materials, placed on the interior of a structure, subjected to vacuum and mild thermal cycling may be expected to perform well over extended periods of time. The interior-facing materials examined did not appear to be close to the end of their performance life. However, for satellites experiencing harsher themal conditions, the performance of some of the materials examined here could be significantly affected. While it is unlikely that high-energy particles caused any significant damage to LDEF materials examined, electronics on interior surfaces are known to be affected by cosmic rays. These subjects merit further examination on future flights.

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