Appendix E 



EXPLORATORY INVESTIGATION INTO THE FEASIBILITY 



OF ACRYLIC PLASTIC CAPSULES FOR 



OCEAN DEPTHS BEYOND 600 FEET 



DISCUSSION 



The experiments constituting the main body of this report have 

 shown conclusively that the spherical acrylic plastic capsules with nominal 

 t/D = 0.033 are safe for depths up to 1 ,000 feet and therefore merit certifi- 

 cation for manned use to at least 600 feet. But this information does not 

 provide the necessary basis for predicting the safe operational pressure of 

 thicker acrylic plastic capsules. Since there may be future requirements to 

 predict what the capsule thickness should be for some greater operational 

 depth (for example, 2,000 feet), a brief exploratory study was performed 

 on the collapse depth of thicker acrylic plastic capsules. 



EXPERIMENTAL PROGRAM 



Model capsules were used to investigate the performance of one 

 nominal t/D ratioonly: 0.066. The outside diameter and polar opening 

 closure designs remained essentially the same as in the model capsules with 

 t/D = 0.033. The only differences between the simulated end closure used 

 on the thin capsules and on the thick capsules (Figure E-1) are (1 ) increase 

 in thickness of closure, (2) use of titanium instead of steel, and (3) a gasket 

 instead of an O-ring seal system. Since only four thick capsule models were 

 available for the exploratory study, it was decided to test them under long- 

 term loading conditions, as in this manner a long-term failure prediction 

 curve, similar to the one derived for thin capsules (Figure 87) could be 

 derived. On the basis of the long-term failure curve, the safe operational 

 depth of such a capsule could be predicted with reasonable accuracy by 

 selecting the same span of time for definition of safe operational pressure 

 as was found to correspond with the 600-foot operational depth for thin 

 capsules (Figure 87). 



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