shells is maintained for longer periods of time. When nylon or teflon 

 gaskets are employed that are only ,010 to .030 thick, then their ten- 

 dency to extrude is less pronounced, but benefits accruing from their 

 use are still questionable. 



PRACTICAL DEEP SUBMERGENCE CERAMIC AND GLASS OC EANOGRAPHIC INSTRUMENTATION 

 CAPSULES 



Once the design and fabrication of cylindrical rib- stiffened shells 

 and their mechanical joints were proven feasible by the experimental deep 

 submergence ceramic shell series described beforehand, no further impedi- 

 ments remained in the path for the design and fabrication of glass and 

 ceramic capsules that would be capable of carrying commercially available 

 oceanographic instrumentation to abyssal depths. Decision, however, had 

 to be made on the type of glass or ceramic to use and how to fabricate it. 



Besides the choice of several different ceramic materials available 

 at the time and experimented with previously, there are many other ceramics 

 and glasses that could be utilized for the construction of glass or ceramic 

 oceanographic capsules. The choice, to say the least, was not easy, parti- 

 cularly when only limited funding was available. Since the requirements at 

 that time were for two distinct capsule operational requirements, it was 

 decided to approach the design and fabrication of these capsules from two 

 different viewpoints. The operational requirements for the two- capsule 

 systems differed considerably. One capsule system, to be composed of 

 several individual capsules diving simultaneously, was to collect data 

 on the relationship between depth, water temperature and sound propagation 

 parameters. Since low dive and rise velocities are more desirable for this 

 system than fast ones, and no restrictions were placed on the overall weight 

 and size of the individual capsules, no effort was made to optimize the 

 structural or fabrication parameters of these capsules. The other capsule 

 system, in which the capsules were to be used individually, was to perform 

 measurements of hydrodynamic parameters as the capsule's ballast was varied 

 to achieve different rise velocities. As the hydrodynamic performance of 

 the capsule was its main operational requirement, low weight, larger dis- 

 placement and optimum hydrodynamic shape were of utmost importance. Since 

 these two approaches used in the design and fabrication of the glass or 

 ceramic capsules are quite different, they bear further discussion. 



In the design for external pressure shells, there are basically two 

 approaches to the utilization of a given structural material. One approach, 

 generally applied to vehicles where strength to weight ratio of the hull, 

 regardless of cost, is the overriding requirement, relies on exhaustive 

 quality control of the material, and painstaking adherence to very tight 

 dimensional tolerances. Being assured of the quality of the material and 



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