ABSTRACT
According to U.S. MIL-STD-1472D, an average man using both hands can safely pick up an object from the floor, carry it, and place it on a horizontal surface 5 ft (1.52 m) high if it weighs no more than 56 lb (25.4 kg). If we assume a cylindrical plane-parallel mirror of 9:1 diameter-to-thickness ratio made of ULE, this weight would correspond to a diameter of 20.0 in. ( 51 cm) and a thickness of 2.23 in. (5.66 cm). Although arbitrary, this calculation forms the basis for the size boundary used here to delineate between a “small” and a “large” mirror. Designs for single-substrate mirrors as large as 8 m ( 26 ft) — for which the main considerations are ways to reduce weights and surface deflections to tolerable levels — are discussed in Chapter 9. Techniques for mounting large mirrors in different orientations relative to gravity are considered in Chapters 10-12. Chapter 12 also includes some considerations of segmented-aperture mirror arrays of large size. The design and mounting of metallic mirrors of various sizes are the subjects of Chapter 13.
