Carbon Foam-Based Lightweight Mirrors

"Several current and upcoming space-based telescope and laser beam director designs, such as the Next-Generation Space Telescope and the Space-Based Laser, call for large aperture optical components, often tens of meters in diameter. Using conventionalmirror/director technologies, the cost and weight of these systems would be prohibitive. In addition, conventional materials, such as glass, offer insufficient stiffness and their performance is affected by vibration and thermal service conditions. Amethod of fabricating mirrors/directors by infiltrating coal-based carbon foam with sol-gel glass compositions is proposed. The coal-based foam can be tailored with regard to stiffness, thermal expansion, and graded in density and pore structure throughits thickness to provide localized stiffness and thermal expansion control while maintaining an overall weight-efficient structure. The sol-gel derived glass provides the optical surface - in a form amenable to foam infiltration by common resin transfermolding practice. Both materials are very inexpensive (cents per pound) and, together, offer broad design flexibility. Polishability to obtain optical quality surfaces and thermomechanical performance in simulated space service conditions will beconsidered in the proposed effort. Carbon, when graphitic and highly ordered as in fiber or deposited film forms, can exhibit unmatched stiffness and thermal stability (e.g., near-zero thermal expa