Stachiw 



4400 to 4600 psi range at 1000 psi exterior pressure. 



The time dependent strain rate of the model's interior under 

 3350 feet operational depth submersion (Figures 17 and 18) decreased 

 from 100 microinches/hour , one half hour after submersion to 0.15 

 microinches/hour after 200 hours of submersion at operational depth 

 indicating that only very little additional time dependent strain 

 would take place in the future if the model was left at operational 

 depth permanently. 



OPERATIONAL PERFORMANCE OF HABITAT MODELS - The operational 

 performance of the habitat models was successful. No leakage occur- 

 red through the four window assemblies, three wire feed-throughs , 

 and the single instrumentation tower assembly. Inspection of the 

 penetration insert assembly components after implosion of the models 

 showed that no yielding took place in any of the components. 



CONCLUSIONS 



Findings based on experimental data resulting from testing to 

 destruction of spherical concrete pressure hulls show that concrete 

 is a reliable material and that buoyant external pressure hulls with 

 a safety factor of two can be built from it on land that will per- 

 form successfully undersea at 3350 foot depth for at least one to 

 two week periods of time. Whether concrete hulls with a safety 

 factor of two will perform successfully at 3500 feet design depth 

 for periods of time measured in years will have to be experimentally 

 established. Indications exist that they will be able to do so 

 successfully. 



In view of the fact that concrete is a very economical material 

 whose composition is well known, and that construction techniques of 

 large concrete shells on land are well developed, more emphasis 

 should be placed by the U. S. Navy on utilization of this material 

 to permanent, or semi permanent ocean bottom installations in the 

 to 3500 foot depth range. 



233 



