Foam-core sandwich panels offer exceptional stiffness-to-weight ratios, and Ultramet has used this architecture for advanced mirror systems. Foam-core mirrors employ an optical faceplate that is attached to the surface of a foam billet, and, if stiffness requirements demand, a second faceplate can be added to the rear surface. Mirrors have been fabricated with both flat and curved optical surfaces, and several material systems have been used. Silicon and silicon carbide systems offer the greatest stiffness-to-weight ratio.
- Optical properties meet or exceed those of current glass, ceramic, and metal reflectors while maintaining a substantially lower areal density.
- Foam structural support yields high specific strength and low mass.
- Fully dense, isotropic, near-net-shape faceplate is highly polishable.
- Thermal conductivity is high.
- Fluids can be passed through foam for actively cooled structures.
- Less complex and less expensive positioning systems are required.
Ultramet combines a precision silicon carbide reflector surface and a high specific strength, low-mass silicon carbide structural support to fabricate optical composite reflectors for space- and Earth-based telescopes.
Left, low-density, high-stiffness silicon carbide foam structural support (50×); right,cross-section of silicon carbide mirror surface (top) applied over silicon carbide foam (bottom).
Silicon carbide foam-based mirror, 10″ diameter, after polishing