to payload requirements by varying the total number of cylindrical shell 

 sections in the hull. As far as fabrication is concerned, it is much 

 easier to fabricate cylindrical shell sections than spherical shell sec- 

 tions of equal diameter; and since a sphere must be of much larger diameter 

 than a long cylinder in order to carry the same payload, the comparison 

 between the cost and difficulty of fabricating spherical and cylindrical 

 hulls for the same payload becomes more and more favorable for the cylin- 

 drical hulls. 



There are, however, some problems connected with the use of cylindrical 

 shell sections, too. The two major problems are, first, the need to incor- 

 porate ribs into the cylindrical shells to make them elastically stable, 

 and, second, the need to provide the many shell sections in the hull with 

 mechanically reliable and strong metallic joints. The incorporation of 

 ribs into the shell structure makes their design more complicated and 

 fabrication more difficult, but without the ribs the walls of the cylinder 

 would have to be excessively thick in order to prevent failure of the glass 

 or ceramic shell by elastic instability. The need to join the many shell 

 sections by metallic joints requires the design of a joint that is not 

 only compatible with the glass or ceramics that it joins, but that is also 

 capable of withstanding the large column loads and hydrostatic pressure 

 loading at operational depths not to mention the high bending moments 

 imposed on the hull during launchings or retrieval operations. 



Experimental Deep Submergence Ceramic Shell Series 



To provide the cylindrical hulls for glass and ceramic deep sub- 

 mergence free-diving instrumentation capsules, it was necessary then to 

 investigate the design of ribs for glass and ceramic shells and their 

 fabrication. For this purpose a series of ceramic rib-stiffened shells 

 was designed" in 1962. Two materials were used, Coming's Pyroceram #9606 

 and Coor's 99-percent alumina. These two materials were chosen because of 

 their high moduli of elasticity, high compressive strength, and above 

 average flexural strength. Since transparency of the deep submergence 

 hull for ASW weapons or instrumentation capsules is not necessary for 

 ultimate utilization, no drawbacks were considered to be associated with 

 the selection of opaque ceramics for the experimental series of cylindri- 

 cal hulls. Although the behavior of rib- stiffened ceramic shells under 

 hydrostatic pressure was the main objective of the investigation, suffi- 

 cient additional shells were ordered to permit investigation also of 

 several additional points of interest. As the depth capability of 20,000 

 feet is considered to be sufficient to operate in 90 percent of the hydro- 

 space, all of the shells in the exploratory series were designed for that 

 operational depth. In order to cover the field adequately, one shell 

 design had only end stiffeners (Figure 2) , one design had an additional 



264 



