INTRODUCTION 

 Objectives 



1 . Accumulate experimental test data on full-scale viewports under 

 simulated operational conditions. 



2. Develop a rational failure criterion for conical acrylic viewports. 



3. Develop parametric design curves based on the failure criterion. 



Purpose 



The presence of viewports in practically every undersea vehicle is 

 indicative of their importance for visibility in undersea research. Piccard^ 

 first introduced conical acrylic viewports in 1939 and, presently, 18 submer- 

 sibles, or about half the total number, utilize Piccard's 90° conical frustum 

 design for a wide range of operating depths. Figure 1 shows full-scale, 90° 

 conical viewports while Reference 2 contains a historical background on 

 viewports along with a summary of viewport designs for about 40 vehicles. 



This study is intended to satisfy a need in the design of conical 

 viewports that has existed and has seen no improvement for the past 30 

 years. The need was to develop parametric design curves based on the 

 viewports functional use and to include time effects (creep) in the design 

 curves. 



A thorough structural analysis of a conical viewport was not even 

 available until just recently.-^ '^'^ All three of these references provide good 

 insight into the structural response of a conical viewport, however, they do 

 not provide any information for the designer. 



Although acrylic viewports have accumulated a large amount of 

 operational time, thereby generating some confidence in the material, trepi- 

 dations still do exist. Design curves based on accurate experimental material 

 tests, a rational failure theory, and complete structural analysis should relieve 

 these fears and provide more confidence in viewport design. 



Design recommendations for conical acrylic viewports would not be 

 complete without a section on sealing. Therefore, Appendix A contains 

 information on methods of sealing and how they affect the viewport design 

 economically, operationally, and structurally. 



