Observation windows of the deep submersible Alvin

The basis of the design of ALVIN plexiglas windows is presented. Results of several tests of plexiglas windows are presented and discussed. It is concluded that the lapping of windows into their seats is unnecessary and that a close fit is not required. ALVIN windows are conservative in design for the operating depth of 6000 feet. The use of a test window seat which does not simulate the hull strains is satisfactory for window test. It is recommended that the conical window seat be extended inward beyond the window to allow for normal elastic extrusion. Plexiglas windows are susceptible to collision damage due to brittleness and low strength of the material. An external rubber gasket is required to prevent low pressure leakage.