nal to the hull alleviates the internal volume 

 problem and significantly eases the weight 

 (or buoyancy) problem. The potential for 

 short circuits or other failures due to leakage 

 is virtually nil when the power system is 

 inside the hull, but the gain is partially 

 offset by occupant safety considerations. 



Operational Handling 



Recharging or turn-around time of bat- 

 tery-type power systems and fuel cells is an 

 important factor. Submersibles of the DEEP- 

 STAR series require 6 to 8 hours for recharg- 

 ing between each 4- to 6-hour dive. Vehicles 

 of the BEN FRANKLIN and ALUMINAUT 

 variety require 12 hours and longer. The 

 only reported experience with fuel cells (4) 

 indicates that very little time is required to 

 place new fuel and oxidant aboard the vehi- 

 cle. It is the practice with several vehicles 

 simply to replace a used battery package 

 with a charged one after each dive, thereby 

 significantly decreasing turn-around time. 

 This latter option assumes that the design of 

 the vehicle permits such modular replace- 

 ment. Short turn-around time is critical to 

 the economic utilization of a submersible 

 operating in areas where weather dictates 

 the deployment of vehicles. In the North Sea, 

 for example, periods of relative calm can be 

 quite short, and the submersible requiring 6 

 to 8 hours turn-around time works at a dis- 

 advantage. 



Maintainability and Repairs 



Few submersibles are furnished with an 

 enclosed area for repairs or maintenance 

 aboard their support ship. Consequently, 

 weather plays an important role in the time- 

 ly correction of malfunctions or in routine 

 maintenance. Where repairs to an internal 

 power package are required the problem re- 

 mains, but is less severe because the work 

 may be performed within the shelter of the 

 pressure hull and, depending upon the na- 

 ture of the casualty, may be performed dur- 

 ing the dive itself. External power systems 

 are limited to repairs only when the vehicle 

 is aboard ship or ashore. BEN FRANKLIN 

 and ALUMINAUT present the advantages 

 and disadvantages of the opposing power 

 system location strategies. Both vehicles are 

 generally towed to the operating site and 



remain in the water during the operation 

 because their size and weight preclude 

 launch/retrieval in a routine fashion, li BEN 

 FRANKLIN undergoes a significant battery 

 malfunction, the vehicle must be towed to a 

 port where facilities are available to lift the 

 142-ton vehicle out of the water. Conversely, 

 ALUMINAUT, with silver-zinc batteries in- 

 side the pressure hull, may be repaired in 

 the water and on site — thereby negating a 

 long tow and expensive lift to ascertain the 

 nature of the problem. 



To digress for a moment, the future sub- 

 mersible designer should note that while 4L- 

 UMINAUT's internal batteries allow easier 

 maintenance and repair than BEN FRANK- 

 LIN^s external, keel-mounted, lead-acid bat- 

 teries, ALUMINAUT's electrical penetrators 

 are below its waterline. Hence, when ALUMI- 

 NAUT's penetrators fail (as was the case in a 

 1968 Puerto Rican operation) it must be 

 lifted out of the water. BEN FRANKLIN, on 

 the other hand, has all its electrical penetra- 

 tors above the waterline, thereby allowing 

 in-water repairs. 



Reliability 



There are a variety of candidate power 

 systems which offer considerable advantages 

 over lead-acid batteries, but the extreme in- 

 hospitality of the deep sea, and the size and 

 weight limitations imposed on the system by 

 small submersibles precludes a number of 

 redundant measures incorporated in most 

 marine designs (3). For such reasons and the 

 overriding need for a reliable power source, 

 many potentially better power systems fail 

 to make it through thelcompetitive selection 

 process. 



Cost 



The U.S. Navy's NR-1 receives its power 

 from a nuclear reactor and may remain sub- 

 merged and cruising for 30 days or longer. 

 NR-1 is acknowledged to have cost some $99 

 million. What portion of this value repre- 

 sents the power package is unknown, but is 

 certainly at least an order of magnitude be- 

 yond the budgets of present, private sub- 

 mersible builders. Likewise, the increased 

 size and weight of the vehicles needed to 

 accommodate nuclear reactors would impose 

 severe penalties on mobility and maneuvera- 



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