The diameter chosen at that time for the operationally most useful 

 panoramic capsule concept was 120 inches. That diameter was arrived at 

 on the basis of two considerations: ( 1 ) that this is the minimum size that 

 will permit a two-man crew to remain comfortably on the ocean bottom 

 submerged longer than a day, and (2) that this is the largest capsule for 

 continental shelf depth that can be built around the required t/R = 0.0685 

 from 4.125 inch thick material, the thickest commercially available acrylic 

 plastic plate. Since during the course of the acrylic plastic capsule program 

 a smaller prototype operational capsule of 66-inch diameter was to be built, 

 the operators would have to put up with scaled-down hatches, penetrations, 

 attachments, etc., of less than ideal proportions from the human factors 

 viewpoint. To permit as many subsequent changes in the capsule design as 

 possible, only as many details were to be incorporated in the first capsule 

 design as were needed to permit the construction of a 15-inch model for 

 experimental validation of the capsule design. To save time in drafting and 

 detail design, it was decided to bypass one step generally required between 

 the formulation of the full-scale concept and the fabrication drawings for 

 a scale model needed for experimental validation of the full-scale concept. 

 The step bypassed was the detailed design drawing of the full-scale concept, 

 which when scaled down and simplified would have become the fabrication 

 drawing for the small-scale (15-inch) model. Thus, the fabrication drawings 

 for the small-scale model of the capsule were prepared directly from the 

 rough concept sketches. This shortcut made it possible to complete fabri- 

 cation drawings of the small-scale capsule model in less than 2 months after 

 the formulation of the concept. Because of the elimination of this step in 

 arriving at small-scale model dimensions, the fabrication drawings for any 

 subsequent capsules with diameters larger than 15 inches became only 

 scaled-up versions of the 1 5-inch model capsule. There are some short- 

 comings associated with this approach. However, it was felt that the 

 advantage of being able to check experimentally the quite radical concept 

 before considerable time and money were expended on engineering the 

 details of the concept offset the major shortcoming: freezing the design 

 of the capsule during the first 2 or 3 months of the acrylic plastic capsule 

 program before a thorough engineering study could be undertaken on the 

 many feasible design trade-offs. 



The resulting fabrication drawings (Figures 15 through 23) of the 

 capsule model reflect quite faithfully the previously discussed conceptual 

 approaches to (1) means of ingress and egress, (2) penetrations for electric 

 and hydraulic circuits, (3) attachment of the capsule to other NEMO struc- 

 tural systems, (4) magnitude of working stresses, (5) specification of 

 construction materials, and (6) hull thickness. No attempt was made to 



37 



