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Atomic Oxygen Durability of Second Surface Silver Microsheet Glass ConcentratorsSecond surface silver microsheet glass concentrators are being developed for potential use in future solar dynamic space power systems. Traditional concentrators are aluminum honeycomb sandwich composites with either aluminum or graphite epoxy face sheets, where a reflective aluminum layer is deposited onto an organic leveling layer on the face sheet. To protect the underlying layers, a SiO2 layer is applied on top of the aluminum reflective layer. These concentrators may be vulnerable to atomic oxygen degradation due to possible atomic oxygen attack of the organic layers at defect sites in the protective and reflective coatings. A second surface microsheet glass concentrator would be inherently more atomic oxygen durable than these first surface concentrators. In addition, a second surface microsheet glass concentrator design provides a smooth optical surface and allows for silver to be used as a reflective layer, which would improve the reflectivity of the concentrator and the performance of the system. A potential threat to the performance of second surface microsheet glass concentrators is atomic oxygen attack of the underlying silver at seams and edges or at micrometeoroid and debris (MMD) impacts sites. Second surface silver microsheet glass concentrator samples were fabricated and tested for atomic oxygen durability. The samples were iteratively exposed to an atomic oxygen environment in a plasma asher. Samples were evaluated for potential degradation at fabrication seams, simulated MMD impact sites, and edges. Optical microscopy was used to evaluate atomic oxygen degradation. Reflectance was obtained for an impacted sample prior to and after atomic oxygen exposure. After an initial atomic oxygen exposure to an effective fluence of approx. 1 x 10(exp 21) atoms/cm(exp 2), oxidation of the silver at defect sites and edges was observed. Exposure to an additional approx. 1 x 10(exp 21) atoms/cm(exp 2) caused no observed increase in oxidation. Oxidation at an impact site caused negligible changes in reflectance. In all cases oxidation was found to be confined to the vicinity of the seams, impact sites, edges or defect sites. Asher to in-space atomic oxygen correlation issues will be addressed.
Document ID
19960023954
Document Type
Conference Paper
Authors
deGroh, Kim K. (NASA Lewis Research Center Cleveland, OH United States)
Jaworske, Donald A. (NASA Lewis Research Center Cleveland, OH United States)
Smith, Daniela C. (Cleveland State Univ. OH United States)
Mroz, Thaddeus S. (NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
September 6, 2013
Publication Date
April 1, 1996
Subject Category
Spacecraft Propulsion and Power
Report/Patent Number
E-10226
NASA-TM-107210
NAS 1.15:107210
Meeting Information
International Conference on Protection of Materials and Structures from the Low Earth Orbit Space Environment(Toronto)
Funding Number(s)
PROJECT: RTOP 233-1A-1E
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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