Project Title:

Ultra-Lightweight, Silicon-Carbide Mirrors for Cryogenic Infrared and Sub-Millimeter Reflectors

92-1-08.16-0204                                                    NAS07-1240
Ultra-Lightweight, Silicon-Carbide Mirrors for
     Cryogenic Infrared and Sub-Millimeter Reflectors
and Grazing Incidence Applications
SSG, Inc.
150 Bear Hill Road
Waltham, MA  02154
Michael Anapol                                       (617-890-0204)

Abstract:

     NASA's advanced instrumentation requirements call for the
development of large, ultra-low mass mirrors as a replacement for
current glass and beryllium technologies. This project uses
silicon-carbide (SiC) honeycomb, foam, and chemical vapor
composites to achieve a revolutionary reduction in areal density
from current 20 -50 kg/m2 to 2 - 5 kg/m2. The company has demon-
strated near-diffraction-limited performance at < 1 ĉm at 20 K on
sample lightweight SiC mirrors. An IR&D program has produced a 3-
inch sample mirror weighing only 15 grams and an ultra-lightweight
structural assembly. This project extends the SiC lightweight
mirror development to larger sizes with near-net-shape surfaces.
Another application for SiC composites is grazing incidence EUV
mirrors; forming of the intricate mirror surface to near net shape
is a critical attribute. Thin layers of silicon applied to the
mirror surface easily achieve high quality, low-scatter surfaces
by diamond turning and/or conventional polishing. SiC has superb
stiffness, allows lightweight designs (equal to or better than
beryllium), has superior thermal stability to cryogenic
temperatures, and can be produced at low cost. The demonstration
mirror fabricated in Phase 1 will have a ÷9" diameter with a
weight goal of <0.2 kg.

Potential Commercial Application:

Potential Commercial Applications:  These mirrors can be used in
infrared reflectors and airborne extreme-ultraviolet telescopes.

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