NASA Langley Research Center
Hampton, Virginia

Technical Discipline Area: Systems

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Responsible Parties: Page Content: William H. Kinard Page Construction: Thomas H. See

The Systems Special Investigation Group (Systems SIG) was chartered to investigate the effects of LDEF's extended mission on both spacecraft and experiment systems, and to coordinate and integrate all systems analysis. LDEF carried a remarkable variety of mechanical, electrical, thermal and optical systems, subsystems, and components. A total of 19 of the 57 experiments flown on LDEF contained functional systems that were active on-orbit. Almost all the other experiments possessed at least a few specific components of interest to the Systems SIG (adhesives, seals, fasteners, optical hardware, etc.). The hardware of interest to the Systems SIG included an enormous diversity of systems, subsystems, and components.

The management of this hardware was facilitated by dividing it into the four major engineering disciplines represented by LDEF hardware: mechanical, electrical, thermal, and optical. In order to assist the post-flight testing and analysis of LDEF hardware, the Systems SIG developed a set of standarized test plans for each of the four engineering disciplines. Beginning with support of LDEF deintegration activities at the Kennedy Space Center (KSC), Systems SIG personnel supported testing of active systems associated with various experiments at KSC, the experimenters' facilities, or at Boeing Defense and Space Group facilities.

The LDEF Systems SIG produced two summary documents from their studies: Analysis of Systems Hardware Flown on LDEF - Results of the Systems Special Investigation Group, NASA CR-189628, April 1992, and Analysis of Systems Hardware Flown on LDEF - New Findings and Comparisons to Other Retrieved Spacecraft Hardware, NASA CR, May 1995. These two documents are the primary sources for the majority of the information contained within Systems-related areas of this archive.

Analysis of various LDEF systems indicated that the primary cause of on-orbit system anomalies or inadequate system performance related to poor design, poor workmanship, and/or the lack of adequate pre-flight testing. There were several major system anomalies, however, analysis indicated that none of these could be solely attributed to the long-term exposure in low-Earth orbit (LEO). With the exception of on-orbit contaminated optics, effects of the LEO space environment on system performance has proven to be negligible. However, this finding should be tempered by the fact that LDEF received relatively low radiation dosages.

No system anomalies occurred that indicated any new fundamental limitations to extended mission lifetimes in LEO. However, shielding from the effects of atomic oxygen, micrometeoroids, space debris, and ultraviolet radiation must be considered. The combination of any of the individual LEO environmental factors such as UV, atomic oxygen, thermal cycling, meteoroid and/or debris impacts, and contamination can produce synergistic conditions that may accelerate the onset and rate of degradation of space-exposed systems and materials.

• Experiments
• Special Investigations
  • Mechanical Systems
  • Thermal Systems
  • Electrical Systems
  • Optical Systems
• Contamination Issues
• References

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