may operate. Excluding Navy submarines, only batteries have 

 been employed for main power in manned submersibles. Until fuel 

 cells, thermal dynamic systems, small nuclear plants and other 

 power sources can be developed for deep ocean service our under- 

 sea activities will be limited. 



Materials 



Material developments for hydrospace structures and equip- 

 ment are basic to advances in most other technological areas and 

 are essential for advances in ocean engineering capability. Im- 

 provements are necessary in strength-to-weight ratio, corrosion 

 resistance and manufacturability. Because of the necessity to use 

 materials with a low strength/weight ratio, our pressure hull 

 structures have a weight displacement ratio too high for penetrat- 

 ing deep depths unless auxiliary buoyancy is utilized. Develop- 

 ment of high strength-to-weight ratio pressure-hull material is 

 necessary. HY 180 steel, the best material available today, still 

 produces a pressure hull heavier than the water it displaces for 

 depths greater than approximately 24, 000 feet. 



In the field of metals our major developments have been in 

 high strength steels and titanium. When developing a new material, 

 like the HY 130 presently being certified as a Class I steel for sub- 

 marine construction, the Navy must not only look at the base metal 

 and its properties, but also must consider the problems associated 

 with fabrication, manufacturing, welding, fatigue strength, corro- 

 sion resistance, and non- destructive testing. Thus, it is inaportant 

 to develop a new material as a system. Our work presently under- 

 way in the HY 130/150 steel is an illustration of material being de- 

 veloped as a system, and of work previously carried out under ex- 

 ploratory development and being picked up and continued under 

 advanced development. The development of HY 130 as a Class 1 

 material will be about a 4- year program costing $16 million. This 

 does not include the exploratory development effort on HY-130 or 

 account for the knowledge gained and carried over from other steel 

 developments, such as HY-80. 



The DSRV tri- sphere pressure hulls, made from HY-140 steel, 

 are examples of the progress that has been made in applying high 

 strength steels to relatively small structures. 



Titanium shows great potential for deep submergence applica- 

 tions in the area of pressure hulls, buoyancy spheres and outer hull 

 structural members. This fiscal year the Navy is starting con- 

 struction of a titanium (100, 000 psi yield strength) replacement hull 



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