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Although large cryogenic space telescopes may provide a means of answering compelling astrophysics questions, the required increase in the primary mirror diameter presents technical challenges. Larger primaries are more flexible, and cryogenic mirrors are typically very lightly damped-the material damping is negligible, and common damping methods break down. To address these challenges, we propose placing flux-pinning mechanisms along the edges of adjacent mirror segments. These mechanisms consist of a collection of magnets and superconductors, and like flexures, they preferentially allow motion in specific degrees of freedom. Motion in nonpreferred degrees of freedom is resisted by a force analogous to a damped spring force, and the stiffness and damping can be adjusted independently. As an example, we consider simple mechanisms consisting of an inexpensive magnet and a single superconductor. These mechanisms provide increasing resistance as the magnet and superconductor-or mirror segments attached to each-come closer to colliding. These mechanisms, with typical stiffness and damping values on the order of 5000 N∕m and 5 kg∕s, respectively, also provide modest improvements to the mirror performance. Greater gains can be achieved by using stronger magnets or smaller separations, or by placing nonmagnetic conductive materials near the mechanism.

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We are developing grazing-incidence x-ray optics for astronomy. The optics are full-cylinder mirror shells fabricated using electroformed-nickel replication off super-polished mandrels. For space-based applications where weight is at a premium, very-thin-walled, light-weight mirrors are required. Such shells have been fabricated at MSFC with < 15 arcsec resolution. The challenge, however, is to preserve this resolution during mounting and assembly. We present here a status report on a mounting and alignment system currently under development at Marshall Space Flight Center to meet this challenge.