ible to rival and perhaps to exceed the endurance 
of fuel cell powered submersibles. 
2. Fuel Cells 
a. Current Situation Deep submersible vehicles 
and habitats with power requirements in the 10 to 
100 kilowatt range may well use fuel cells in the 
coming decade. The hydrogen-oxygen fuel cell has 
by far the most extensive development history, 
albeit for highly specialized and costly space 
applications. 
Another major fuel cell type being considered 
for undersea use, hydrazine-hydrogen peroxide, 
has received relatively less attention but is in an 
advanced state of development for terrestrial 
applications by the U.S. Army. It is a much less 
expensive device probably in part because of less 
stringent qualification and documentation require- 
ments. Like the battery, the fuel cell is a static 
energy converter producing electrical energy from 
chemical energy. 
Unlike the battery, the fuel cell can produce 
energy as long as fuel and oxidant are supplied. 
Fuel cells produce waste products (heat and water 
from the hydrogen-oxygen cell or heat, water, and 
nitrogen from the hydrazine-hydrogen peroxide 
cell) which may be of use. 
The basic concept of the fuel cell has received 
much conceptual development during the first half 
of this century. Nevertheless, it took the impetus 
of the space race and the expenditure of over $100 
million to provide the operational hydrogen- 
oxygen fuel cell systems used in the Gemini and 
Apollo projects. Such accelerated technology de- 
velopment ultimately may have applications in 
automobiles, recreational boats, and undersea 
systems. 
A fuel cell is planned as the power source for 
the Navy’s Deep Submergence Search Vehicle 
(DSSV). The 34-hour DSSV mission time and 
power consumption rate demand peak power of 
50 kilowatts and a 1,000-kilowatt-hour energy 
supply. The system, including required buoyancy 
material, will weigh about 10,000 pounds, or 10 
pounds per kilowatt hour. A silver-zinc battery 
system providing the same energy would weigh 
about 30,000 pounds. The additional vehicle 
weight and size required to utilize silver-zinc 
batteries would seriously affect the performance 
of DSSV. 
b. Future Needs Fuel cells appear essential to 
efficient undersea operations. Hydrogen-oxygen 
fuel cells for undersea use require hard tanks for 
both the fuel cell module and the fuel. The fuel 
could be stored cryogenically as a liquid, but 
substantial insulation would be required. 
Tankage, designed to withstand ambient pres- 
sure at operating depth, adds considerable weight 
to the power system. If a fuel cell could be 
developed capable of pressure-balanced ambient 
operation without hard tank protection, system 
weight would be independent of operating depth, 
and a weight-to-energy ratio of six to eight pounds 
per kilowatt hour might be achieved. This could 
result in important weight improvement in power 
systems for 20,000-foot submersible operations. 
3. Thermal Conversion 
a. Current Situation Thermodynamic power 
systems may range from the simplest, using jet fuel 
and an oxydizer with a reciprocating engine, to 
very advanced systems, using such high energy 
sources as the reaction of sodium with seawater. 
Application of thermodynamic cycle systems most 
likely will be in the shallow zero to 2,000-foot 
zone, thereby allowing wastes to be exhausted 
directly to sea. For covert operations, it would be 
necessary to condense the exhaust and store it 
aboard so no trail would be left, and neutral 
buoyancy maintained. 
An extensive engineering effort was devoted to 
closed cycle thermodynamic power systems in the 
early 1950’s. A complete evaluation was made of 
long-term submerged operations, and_ several 
usable concepts were developed to permit sub- 
merged operations of days or weeks. The pressur- 
ized water nuclear reactor development in 1955 
supplanted the thermodynamic power concept for 
fleet submarines, and little additional work has 
been done since. 
b. Future Needs Few undersea applications will 
require a nuclear reactor energy source. Chemical 
dynamic systems (operating on the Brayton, 
Rankine, or Sterling cycles and utilizing a re- 
ciprocating engine or a turbine driving an electrical 
generator) could produce electrical energy at much 
less cost and weight than a nuclear plant and 
should receive renewed development attention. 
