Recommendations: 
More efficient, reliable, lighter weight external 
subsystems are critical to deeper ocean operating 
capability. Development has not received the 
attention given materials and power sources, al- 
though of equal importance. A program specifi- 
cally aimed at improving reliability and developing 
new external machinery systems and equipment— 
propulsion systems, buoyancy, and trim control 
systems—is needed. 
The Navy’s Deep Ocean Technology Program 
should be funded to the requested levels. 
Civilian technology funding levels should allow 
the development of fundamental knowledge 
needed to produce low-cost systems for non- 
military users. 
D. Materials 
Materials problems enter critically into every 
aspect of underwater technology. The economy 
and effectiveness of ocean activities are dependent 
upon development of improved materials for 
submersible vehicles, underwater structures, equip- 
ment, and all types of components. Material 
development involves not only basic metallurgical 
and mechanical properties but problems of pro- 
duction, design, fabrication, testing, in-service in- 
spection, corrosion, and marine fouling. 
Developments are needed in metallics, non- 
metallics, and composites of increased strength 
with sufficient notch toughness, corrosion resist- 
ance, fatigue strength, producibility, weldability, 
and economy for pressure hulls and other struc- 
tural applications. Included in the nonmetallic 
category are fiber-reinforced plastics, glass, and 
other ceramics. 
Neutral buoyancy is an operating requirement 
for submersibles. Applying a principle that buoy- 
ancy is best provided by the pressure hull and 
auxiliary buoyancy material is used primarily for 
trim—the pressure hull should have a weight-to- 
displacement (W/D or buoyancy) ratio of 0.4 to 
0.6. This allows for the buoyancy required for 
external machinery and equipment, outer hull and 
payload. In the discussions following, a spherical 
geometry is assumed, because this shape provides 
minimum W/D ratios. 
No currently available production material suit- 
able for pressure hulls can achieve a W/D ratio 
lower than 0.5 for 10,000-foot operations. For 
greater depths, supplemental buoyancy material or 
advanced hull materials will be required. The 
amount of such material will be a function of the 
hull’s W/D ratio and the density of the buoyancy 
material. 
The pressure hull buoyancy ratio must increase 
with depth. A recently constructed submersible, 
for example, with an 8,000-foot operating capabil- 
ity has a pressure hull made of a 190,000 pounds 
per square inch (psi) compressive yield strength 
steel and a buoyancy ratio of 0.43. 
The Deep Submergence Search Vehicle (DSSV) 
designed to operate to 20,000 feet would have a 
pressure hull buoyancy ratio of 0.9 if fabricated of 
the same material. The buoyancy ratio of the 
DSSV pressure hull would be reduced to 0.7 if a 
titanium alloy of 125,000 psi compressive yield 
strength were used. 
Higher yield strength titanium alloys have not 
been used in deep submergence pressure hulls 
because of lower toughness and possible suscepti- 
bility to stress corrosion. If a titanium alloy with 
a 180,000 psi yield strength and acceptable tough- 
ness became available, a pressure hull buoyancy 
ratio as low as 0.5 could be attained for 20,000 
feet. 
~ Complementary needs include (1) hatches that 
form an integral part of the structure when closed, 
but which can open for mating operations at great 
depth without dangerously degrading the struc- 
ture, (2) techniques to utilize more than one 
material in a hull to capitalize on the unique 
advantages of each, (3) analytical tools to predict 
and evaluate preliminary design choices, and (4) 
fabrication techniques. 
Development is needed of undersea antifouling 
coatings to inhibit biological growth (Figure 5), 
new coatings to protect against corrosion, and 
cathodic and impressed current techniques for 
combating corrosion. Materials are required for a 
variety of underwater applications in addition to 
pressure hulls: 
—Gaskets, sealants, and pressure hull penetrations. 
—Rubberized fabrics for pipelines, storage con- 
tainers, and buoyancy bladders. 
—Nylon and other materials for mooring cable, 
insulation, and protective sheaths. 
—Transparent materials for viewports. 
VI-41 
