material over that of some other material is based on cost per pound of 

 buoyance. For oceanographic instrumentation systems that do not need the 

 payload- carrying performance afforded only by the lowest obtainable weight 

 to displacement ratios, the above-mentioned approach to fabrication of glass 

 hulls is reasonable, and if proven successful in testing of actual hardware, 

 acceptable. 



Benthos System 



The approach to the design and fabrication of ceramic hulls for 

 Benthos^ (Figure 18) has been just the opposite used in the design and 

 fabrication of DIVEAR glass hull. The different approach used to design 

 and fabricate Benthos followed from a completely different set of systems' 

 operational requirements. The requirements were, in this case, for a 

 hydrodynamically streamlined vehicle with smallest weight to displacement 

 ratio, capable of carrying out oceanographic or ASW missions to depths of 

 35,000 feet. To accomplish these requirements the hull proportions and 

 finishes had to present minimum hydrodynamic drag, while the design stresses 

 had to be of maximum allowable magnitude in order to give the vehicle the 

 utmost in payload- carrying capability for its displacement. 



To meet the low hydrodynamic drag requirements, a cylindrical shape 

 was chosen which was capped at the front with a hemispherical nose and at 

 the rear with a gradually tapered afterbody (Figure 19) terminating in 

 shrouded cruciform fins. Both the ceramic and metallic sections of the 

 hull were fabricated to 32 RMS finish requirements to insure low hydro- 

 dynamic drag. To make the interior of the vehicle accessible and the 

 fabrication costs more economical, the hull was conceived as an assembly 

 of five ceramic and one metallic shell sections joined together by metallic 

 breech- lock joints. As much of the hull was made of ceramic as possible 

 to capitalize on the material's high- strength (Figures 20-22), and only 

 the shrouded fins mounted on a short conical plug were made from metal 

 (Figure 23) . 



The structure itself had to be designed to operate under very high 

 working stresses. Only by stressing the materials to the maximum possible 

 stress level could the hull provide Benthos with the utmost in payload- 

 carrying capability. The fact that Benthos was to provide the utmost in 

 buoyancy for a given displacement at 35,000 feet dictated that only 

 materials with maximum compressive strength-weight ratios and reliable 

 fabrication methods with predictable dimensional control could be employed 

 in the construction of this vehicle. Although all glasses and ceramics 

 are described as being capable of withstanding extremely high compressive 

 stresses, only those could be considered for the construction of Benthos 

 whose compressive strength had been experimentally proven by hydrostatic 



288 



