Hydrostatic loading of 

 the capsules was performed in 

 NCEL's 18-inch-diameter pressure 

 vessel with a 20,000-psi pressure 

 rating. Pressure was raised at a 

 90 to 1 10-psi/min rate based on 

 the maximum planned descent 

 rate for the large-scale operational 

 NEMO system. The pressure was 

 generated with pneumatically 

 powered positive displacement 

 pumps. Their operation generated 

 some pulsations during the pres- 

 surization, but the small magnitude 

 of these pulsations (approximately 

 10 psi) was considered insignificant 

 for the purpose of these hydro- 

 static tests. In all of the short-term 

 tests, the average pressurization 

 rate of 100 psi/min was maintained 

 until implosion of the model 

 occurred. After implosion, the 

 pressure vessel was opened and 

 the fragments inspected for clues 

 pointing to the source of failure 

 (Figure 69). 

 Prior to performance of the short-term tests to implosion, some of 

 the models were subjected to other types of hydrostatic tests. For example, 

 Models 8 and 1 5 were subjected to cyclic loading prior to their implosion 

 under short-term test conditions (see Table 6). Although subjecting the same 

 model to other test conditions prior to short-term implosion testing is gener- 

 ally not desirable, the small number of models available for the evaluation of 

 the capsule design made this test policy necessary. 



Long-term tests were performed on 13 NEMO models (Table 5). 

 These tests were to provide data on the structural response of acrylic plastic 

 hulls to sustained hydrostatic loadings of different magnitudes. After the 

 models imploded under the sustained loading, the duration of loading prior 

 to implosion at a given pressure level would be compared to the short-term 

 implosion pressure. The difference between these pressures would constitute 

 a valid measurement of strength degradation as a function of load duration. 

 Several pressure levels had to be chosen for the long-term test program to 

 establish with sufficient accuracy the relationship between implosion pres- 

 sure and duration of sustained loading. 



End Plate (two required) 

 Material: Titanium T..-GAL-4V 



Figure 65. Heavy-duty polar penetration 

 closures for low temperature 

 implosion testing of 15-inch- 

 diameter model capsules. 



100 



