Advances in earth and space instrumentation will come from future optical systems that provide large, deployable collecting areas of low areal mass density (< 10 kg/sq meter), affordable costs of fabrication ($10k/sq meter), and production times of a few years or less. Laminated optics comprised of an electroformed, replicated nickel optical surface supported by a reinforced shape memory resin composite substrate have the potential to meet the requirements for rapid fabrication of lightweight, monolithic, stowable, large optics, where large is defined to be 8 meters in diameter or larger. The high stiffness of a deployable composite substrate and a high quality, thin, electroformed metal optical surface combine the best properties of these disparate materials to provide a robust yet lightweight mirror system to meet the needs of future missions. The unique properties of shape memory resins in the composite provide a larger range of design parameters for production of usable optics. Results are presented from optical and structural tests of various surface and substrate constructions that may be solutions to the key issues, which are primarily material interface stress control, stability, and deployment repeatability. Initial requirements analysis and material properties measurements that determine both system and individual material target performance are presented.
Research and development in multi-component composites demonstrated new material and fabrication concepts for mirrors for space-based optics. Cornerstone Research Group, Inc., effort, conducted under contract to the Air Force Research Laboratory, developed new organic and inorganic composite materials and investigated their potential for application as light-weight, low-cost alternatives mitigating the drawbacks of conventional materials (glass and metals) and fabrication processes for space-based mirrors. This development demonstrated the feasibility of multi-component organic composites integrating cyanate ester resin with several reinforcements, especially carbon fabric and nanofibers. It demonstrated feasibility of high-quality cyanate ester-based syntactic composite (structural foam composed of microspheres embedded in resin). The development also demonstrated initial feasibility of multi-component inorganic composites integrating a proprietary inorganic resin with particulate and nanofiber reinforcements. These new materials (both organic and inorganic composites) show strong potential for achieving major reduction in mirror areal density (compared with current operational mirrors) while achieving strength, stiffness, and thermal properties required for space applications. Finally, this project demonstrated feasibility of a replication approach to mirror fabrication. With this fabrication technology, a composite mirror is cast directly to net figure and finish. This dramatically simplifies the mirror fabrication process, thereby enabling less expensive tooling than conventional practice for glass or metal mirrors. In production lots of identical mirrors (e.g., spacecraft constellations), the replication approach will provide radical reduction in mirror costs by eliminating the lengthy, expensive grinding and polishing processes for individual units.