only a few applications. Aluminaut uses aluminum 
forged rings for hull construction, and the Alvin 
employed titanium buoyancy spheres. Aluminum 
spheres with yield strength of approximately 
75,000 psi, and small titanium spheres with yield 
strength of 120,000 psi have been fabricated. 
b. Future Needs Extensive development and 
improvement of fabrication techniques must be 
done to realize the full potential of nonferrous 
materials. For example, bottom habitats probably 
will be manufactured in large sections on shore, 
transported by surface ship or towed to the site, 
and lowered. Since most, if not all, structural 
fabrication will take place on land, dry weight will 
be extremely important in handling such large 
structures. 
Operating costs of current submersibles are 
related to vehicle weight due to surface support 
difficulties. Thus, advanced structural materials 
and improved supplement buoyancy that reduce 
vehicle weight can be economically rewarding. In 
the future submerged support of submersibles 
could make dry weight a much less important 
factor. Further, continuing development of non- 
ferrous metals and alloys for ocean equipment and 
components is necessary. Included are gunmetals, 
cupronickels, and cast and wrought aluminum 
alloys. 
3. Nonmetallic Materials 
a. Current Situation Operation of vehicles at 
20,000-foot depths will require pressure hulls 
having weight-to-displacement ratios approaching 
the ideal 0.4. These can be achieved only by using 
the very high strength steels with yield strengths 
above 240,000 psi, titanium with a 180,000 psi 
yield strength, glass-reinforced plastics, advanced 
composites, or massive glass. 
Glass is expected to be developed to a usable 
compressive strength level of 250,000 psi during 
1970-1980. The attractiveness of massive glass lies 
in its low density and theoretical compressive 
strength, possibly as high as 4,000,000 psi. Failure 
generally initiates at the glass surface when tension 
forces are present and occurs long before compres- 
sive capabilities are reached. 
Annealed glass spheres up to 56 inches diameter 
have been fabricated and tested, but results are 
inconsistent, and adequate fabrication control 
techniques have not been developed. Unfortu- 
nately, the failure of glass spheres is unpredictable 
and usually catastrophic; once a crack begins, the 
entire assembly disintegrates. In metallic structures 
the failure mode is usually buckling; initial cracks 
and structural anomalies usually can be detected 
prior to complete failure. 
Glass technology is being applied in construc- 
tion of the Naval Undersea Warfare Center’s 
(NUWC) Deepview, a vehicle having a 44-inch glass 
end hemisphere (Figure 6). Also NUWC’s Hikino 
design has a total glass sphere with no pene- 
trations. The sphere incorporates a titanium ring 
joint between hemispheres and utilizes an acrylic 
inner and outer lining. Other glass construction 
techniques include pouring, sagging by heat, sag- 
ging by vacuum, and injection molding. The Naval 
Civil Engineering Laboratory is working on acrylic 
sphere construction by assembly of 12 identical 
spherical pentagons. 
Figure 6. Artist’s concept of Deepview sub- 
mersible vehicle. (Navy photo) 
Properties and performance characteristics of a 
glass filament, originally developed for Polaris 
rocket cases, have been evaluated under simulated 
conditions. Complex ring-stiffened cylindrical 
models have been tested, demonstrating a capa- 
bility to withstand short-term exposure to 30,000 
feet of hydrostatic pressure and long-term static 
and cyclic exposures at depths to 20,000 feet. 
Glass fiber reinforced plastics (GRP) are of very 
low density and offer the possibility of compres- 
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