It would be an omission not to mention here also small low-quality 

 buoys made for the fishing trade. Although not designed or fabricated 

 for deep submergence application but for use as fishing net surface 

 buoys, some of these buoys can withstand safely depths of 20,000 feet. 

 Available from Blenco Manufacturing Company in the United States, and 

 as imports from Japan and in sizes from 2 to 10 inches in diameter, their 

 cost is less than $1 per pound of buoyancy when purchased in small lots 

 and less than 50 cents per pound of buoyancy in large lot quantities. 

 Their price is very attractive, and because of it they have found some 

 use in deep submergence applications; 10 but unless each buoy is proof 

 tested to its operational depth prior to use in the ocean, they cannot 

 be relied upon. It may be that improved mass production techniques will 

 improve the reliability of these inexpensive glass spheres to such an 

 extent that they can be used, without testing, to some specified oper- 

 ational depths. 



SUBMARINES 



The most glamorous application for which glass and ceramics are being 

 groomedll is that of a hull for deep submergence submarines. At last a 

 hull will be in the possession of man which will permit him to descend to 

 the very bottom of the oceans without recourse to flotation buoys or 

 liquid- filled dirigibles, like Trieste, for support of the hull containing 

 the crew. Glass or ceramic spherical and cylindrical hulls are certainly 

 capable of providing a weight to displacement ratio of .4 which is thought 

 sufficient for providing buoyancy to men and associated equipment in a 

 submarine with an operational depth of 35,000 feet. Glass, in particular, 

 is desirable for such an application because it would not only provide the 

 necessary strength for the hull, but would also provide almost unlimited 

 visibility for the crew, a dream long cherished by submarine crews who 

 today feel that they are actually strangers and intruders in the sea. 



Work initiated in 1962-'- in this area has brought forth many fruits. 

 It has been confirmed in both theoretical studies and in actual experi- 

 ments that the resistance of unprotected glass hulls of different shapes 

 to underwater shock increases with depth to more than 20,000 feet of 

 depths. It was also discovered that a plastic or rubber overlay on the 

 glass hull increased its resistance to shock waves still further. Models 

 of surface- compressed glass spherical hull with a simple circumferential 

 joint, glass entry hatch, and metallic feed throughs were tested to more 

 than 20,000 feet depth without failure while the compressive stress in 

 the hull was approximately 65,000 psi. Silver foil was used as the gasket 

 material for the joints between the hemispheres and between the hatch and 

 its seat. The use of tensioned metallic cages on surface- compressed glass 

 hulls was shown to prevent shattering of the hull when it was locally cut 

 or fractured. 



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