UNDERSEA TECHNOLOGY 55 



Progress has been made in the development of open- and closed-cycle 

 dynamic powerplants in recent years. A number of solid, liquid, and 

 gaseous fuel/oxidizer combinations are feasible for closed-cycle energy- 

 conversion loops. However, it appears that chemical-dynamic heat engines 

 cannot approach the efficiency of fuel cells. Lightweight conversion 

 equipment for this type of powerplant which will allow a relatively low 

 fixed weight is available or realizable. 



MACHINERY FOR OCEAN ENGINEERING 



The extreme weight sensitivity of small deep-sea vehicles imposes 

 severe restraints on the machinery-system designer from concept to the 

 end of construction. Small, Hghtweight systems must be achieved without 

 degrading the safety, rehability, efficiency, maintainability, and many 

 other factors which contribute to the overall suitabihty of the vehicle. 



To minimize pressure hull penetrations, much of the machinery is 

 located outside the pressure hulls. This equipment must either be en- 

 capsulated in a pressure-resistant container or designed to operate at sea 

 pressure in a compensated system. The first alternative permits the use 

 of more conventional equipment at the expense of the weight of the 

 pressure container, the provision of high-pressure seals, and the inherent 

 risk of flooding the container. The second alternative avoids these risks 

 but raises other problems in design of machinery which must operate 

 over a range of ambient pressures varying from sea level atmospheric to 

 the maximum design depth of the vehicle. 



Equipment that is inherently resistant to sea water erosion may be 

 directly exposed to the sea water. However, much equipment (electrical 

 equipment and speed reducers) must be surrounded with a more com- 

 patible hquid (insulating oU) and compensated to sea pressure. The effi- 

 ciency of high-speed rotating equipment is significantly affected by the 

 hydraulic losses encountered in such a system. The requirement for guard- 

 ing against contamination of the compensating liquid introduces additional 

 system complexities. 



These considerations are particularly important in the propulsion area, 

 because the overall suitability of the vehicle to perform useful tasks in the 

 hostile deep-sea environment will depend in a large degree on its speed, 

 maneuverability, endurance, and reUability. Many comparative studies 

 are required to provide a basis for selection of the optimum propulsion 

 plant. 



