ABSTRACT
Various configurations for lightweight substrates for larger mirrors are considered from the mechanical design viewpoint in this chapter. It is important to study this subject before examining mounting arrangements for such mirrors, since the performance of the assembly depends significantly on the design compatibility of the substrate and the mount. Here, we deal primarily with the mirror’s geometric configuration. Because mirror size is a prime driver of design and of material choice, we consider sizes ranging from about 51 cm ( 20 in.) (the upper limit considered in Chapter 8) to large, astronomical telescope-sized ones with diameters up to 8.4 m (27.6 ft). As diameters increase, minimizing weight is increasingly important from the total system weight viewpoint and to minimize self-weight deflection effects. We therefore consider various ways of reducing mirror weight by removing unnecessary material from a solid piece or combining separate pieces to create a built-up structure. Mounting methods for larger nonmetallic mirrors are discussed in Chapters 10-12. Metal mirrors and their mounts are also not included here; those are the subjects of Chapter 13.
