Xinetics, Inc. NAS898243

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• Xinetics, Inc. NAS8-98243
• Large, Low Temperature Silicon Carbide Mirrors
• Ultramet, Inc. NAS8-99094
• Ultralightweight Pyrolytic Graphite Mirror
  Structures

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Xinetics . NAS8-98243 Large, Cryogenic
Ultralightweight Mirror Technology

• Phase II completion date August 31, 2001
• Objective lt15 kg/m2 rigid cryo mirror
• Mirrors
• CeraformSilicon Carbide
• Six, 20 cm diameter flats
• One, 50 cm diameter, sphere (20m RoC)
• Technology
• Reactor Design and Process Optimization
• Polishing Method (removal rate, rms P-V,
  roughness)
• Si Clad and Unclad
• Vendor Survey(General Optics, Kodak, Zygo)

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Xinetics . NAS8-98243 Large, Cryogenic
Ultralightweight Mirror Technology

• 50 cm Design Approach
• Primary Ribs
• 0 .1 cm thick
• Cathedral Ribs used to Increase Stiffness with
  Minimal Weight Penalty
• Facesheet 0.15 cm thick w/ 20 m RoC
• Targeting 10 to 15kg/m2 areal density

• 8 inch cryo testing
• Mounted to Cold Plate Can be Chilled to 10 K
• Copper Straps Added to Improve Heat Flow
• Tested unclad mirror polished by general optics
• Figure was 1/20 wave P-V outside of cryo chamber
  at room temperature
• Figure measured was 1/10 wave P-V inside
  cryochamber at room temperature (due to windows
  of cryochamber)
• Figure gradually changed to 1/5 wave P-V as it
  was cooled to 77K

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Ultramet . NAS8-99094 Ultralightweight
PyrolyticGraphite Mirror Structures

• Phase II completion date September 17, 2001
• Objective lt5 kg/m2 rigid cryo mirror
• Mirrors
• CVD surface on open-cell foam
• Two, 15 cm diameter flats
• One, 30 cm diameter flat
• Technology
• Reactor Design and Process Optimization
• PG foam production (low density, high strength)
• Surface deposition (microhardness, deposition
  rate)
• Polishing(rms, roughness)

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