Fuel Storage. Transportation is the variable factor in fuel costs, which 

 vary in proportion to the quantity of fuel and the distance of delivery. The 

 number of surface hulls serviced affects the cost of fuel. For distant surface 

 hulls, fuel costs can be a significant percentage of the total operating cost. 

 Optinnum quantities for delivery would be 1 50,000 gallons. Quantities larger 

 than this require tanker-size ships. Typically, delivery costs are 0.4 cents per 

 gallon for a 90-mile delivery and 1.1 cents per gallon for a 240-mile delivery. 

 These delivery distances would represent the average distances necessary to 

 reach depths of 600 to 6,000 feet, respectively. The largest surface hull 

 considered had a fuel capacity of 65,000 gallons. 



The fuel storage capacities of a surface hull, shown in Table 7, were 

 obtained by trading off reserve buoyancy capacity, hull diameter, and height. 

 The maximum proportion of diameter and height for surface hulls was 

 established at 55-1/2 feet by 11-1/2 feet; these values are based on values 

 scaled from the monster buoy to maintain good hydrodynamic characteristics. 



Trim System. An automatic trim system was recommended to trim 

 the surface hulls as fuel is consumed. An emergency system is also incorpo- 

 rated and is capable of pumping overboard all fuel and seawater ballast and 

 securing all engines in the event of serious flooding or collision. This 

 emergency system requires air banks and compressors which would normally 

 be required for the larger generator plants. The trim system would also 

 compensate for variations of the external transmission cable loading. 



Upkeep Schedule. A major factor in deploying a surface hull is the 

 laying and installation of the multipoint mooring system. It is not considered 

 feasible after deployment to take the hull up periodically for overhaul or 

 component replacement. For this reason, a mean-time-between-overhaul 

 was established at 5 years for the surface plant hull. This may not be con- 

 sistent with machinery overhaul within the plant; however, the machinery 

 can be interchanged with overhauled equipment. This arrangement is 

 preferred to at-sea overhaul or lengthy maintenance of the machinery. 



Surface Plant Mooring Systems 



The forces and phenomena involved in mooring thick-disc hulls for 

 surface-tendered power plants were defined and analyzed. Once the mooring 

 requirements were established, mooring system configurations were developed 

 and evaluated for the most cost effective systems. An investigation of mooring 

 systems, forces acting on mooring systems, and auxiliary mooring equipment 

 and components were all included in the analysis. 



37 



