3. The good reproducibility of material properties and capsule dimensions 

 from one capsule to another as well as from small-scale models to large-scale 

 capsules results in reliable structural performance, which varies for individual 

 capsules less than ±10% from the average collapse pressure of the group. 



4. The 66-inch prototype capsule for incorporation into the NEMO system 

 met the initial requirements for ( 1 ) 1 ,000 dives to design depth of 1 ,000 feet 

 and (2) implosion under uncontrolled dive conditions only at depth in excess 

 of 3,000 feet. 



5. Both the design and the fabrication method developed for the 66-inch 

 large-scale capsule prototype are applicable directly to the 120-inch-diameter 

 capsule concept, the ultimate goal of the acrylic plastic capsule program. 



6. Although the chosen polar plate dimensions appear to be adequate for the 

 1,000-foot design depth when the plate is fabricated from type 316 stainless 

 steel, the safety margin of the metal plates would be substantially increased 



if they were fabricated instead from Inconel 625 or cadmium plated SAE 4130, 

 both with a minimum yield point of 60,000 psi. 



7. The use of models for validation of spherical capsule designs in acrylic 

 plastic is acceptable; there appears to be no mass scaling factor associated 

 with the scaling up of models to full-scale operational capsules. 



CONCLUSION 



The spherical hull concept of acrylic plastic developed in the NEMO 

 program provides an economical, reliable, and safe pressure resistant capsule 

 with panoramic visibility for continental shelf depths. 



RECOMMENDATIONS 



These recommendations are based on a conservative engineering 

 evaluation of existing data. 



1. On the basis of the experimental and analytical data developed in the 

 66-inch-OD x 61-inch-ID acrylic plastic capsule program the NEMO capsule 

 merits certification to 600-foot depth. Brief proof-test dives are not to 

 exceed 1,200-foot depth. 



2. The crack-free fatigue life of the capsule for dives to 600-foot depth 

 shown in Figure 121 is recommended as a very safe fatigue rating for 

 manned service. 



156 



