equal to their width. Since sufficient polylithic cylinders were not 

 tested to establish optimum gasket materials and their thickness, compres- 

 sive stresses of only 200,000 psi were carried by these polylithic cylinders 

 before failure. The need for an external envelope to make such ceramic 

 structure waterproof makes it heavier than if it was a monolithic cylinder. 

 Depending on the material and thickness of such an envelope, the weight 

 penalty to be sustained by the glass or ceramic cylindrical would vary 

 anywhere from 10 to 20 percent of the monolithic hull's weight. Some 

 penalty must also be paid for the presence of the many joint surfaces 

 which necessitate the lowering of the compressive design stress in the 

 structure so that surface imperfections in the joints will not cause the 

 structure to fail. 



Since it appears that the proliferation of joints in a glass or ceramic 

 structure for the reduction of size of the modular structure components 

 carries with it a penalty in reduced design stresses, the polylithic hull 

 construction should be resorted to only when absolutely necessary. It is 

 for this reason that t;he glass and ceramic industry's present size fabri- 

 cation capability should be doubled before major emphasis is placed on 

 basic modular polylithic construction techniques for deep submergence hulls. 

 The intermediate polylithic construction techniques — cylindrical hulls 

 assembled either from several monolithic or several segmented cylindrical 

 shell sections and spheres assembled from two hemispheres or several 

 spherical polygons — promise to be a happy medium between the high reli- 

 ability and high cost of one-piece monolithic hull construction, and the 

 low cost and low reliability of basic module polylithic construction. 

 When to the already developing intermediate polylithic construction capa- 

 bility will be added soon the increased size fabrication capability of the 

 United States glass and ceramic industry, there will be available by 1970 

 a design and fabrication technology that will permit the construction of 

 deep submergence oceanographic capsules of 5 to 10 tons displacement. 



POST SCRIPT 



Glass and ceramics are at the present time exotic and expensive 

 materialsl^ resorted to by oceanographers only in cases where extremely 

 great depths (Figures 36-38) are to be penetrated by their buoyant research 

 probes. As the usage of these materials increases in the oceanographic 

 capsule field, they will lose some of their exotic lustre and instead gain 

 the sheen of reliable noncorrodible and inexpensive every-day hull con- 

 struction materials. 



311 



