Hyperhemispherical windows with included spherical angles in the 260–270 degree range have been fabricated from acrylic plastic and glass for a variety of undersea applications. When seated in NOSC rigid metallic mountings with conical seats they withstood cyclic design working pressures without failure, or cracking providing that a thin elastomeric gasket was interposed between the mating conical bearing surfaces, and two elastomeric O-rings served as compliant bushings between the spherical surfaces of the window and the retaining surfaces of the mounting. Tests have shown that (1) critical pressures of acrylic plastic hyperhemispheres can be predicted with acceptable accuracy by analytical and empirical relationships developed previously for acrylic plastic hemispheres and spheres, (2) the mounting retains and seals plastic or glass windows in −40 to 120° F ambient temperature range even when subjected to lateral dynamic loading of 17G magnitude, and (3) dimensionally identical hyperhemispheres fabricated from glass and seated in the same mounting do not fail under a single pressurization at twice the critical pressure of acrylic windows.

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