Underwater observatories with panoramic visibility

Spherical and cylindrical acrylic shells are ideal external pressure hulls for underwater observatories and submersibles providing their occupants with panoramic visibility. To date, the maximum working pressure of diving systems with acrylic pressure hulls has been the 450 to 1450 psi (3 to 10 MPa) range, but it could be extended to 3560 psi (79 MPa). Since the ASME PVHO-1 Safety Standard for Pressure Vessels for Human Occupancy accepts spherical and cylindrical hulls for external pressure, all the statutory authorities worldwide have approved spherical and cylindrical acrylic shells as pressure hulls for manned diving systems. This paper serves as an introduction to design of acrylic spherical pressure hulls.