off-the-shelf. These constraints left very few 

 candidates from which to select. A golf cart 

 motor of 3.5 horsepower mounted in a pres- 

 sure-resistant housing designed by General 

 Oceanographies was selected and has been 

 quite successful. The power for this motor 

 was provided by golf cart batteries. Addi- 

 tional guidance was provided by assaying 

 the field to see what other similarly sized 

 vehicles were using. This approach is just as 

 successful for the NEKTON vehicles of Gen- 

 eral Oceanographies as the more sophisti- 

 cated approach taken by the giant Aerospace 

 Corporation for their vehicles. 



The common unit for expressing the power 

 delivered by a motor is horsepower (hp) (one 

 horsepower is defined as 550 ft-lb/sec). In 

 both submersibles and surface ships the 

 power delivered by the engine to the propel- 

 ler is called shaft horsepower (SHP), and is 



the product of the torque and revolutions per 

 minute of the shaft. Another definition of 

 SHP deducts shaft seal and bearing losses 

 from the engine output to derive actual 

 power delivered to the propeller (2). The 

 power required to propel a submersible 

 through the water is expressed as effective 

 horsepower (EH?) and is equal to the prod- 

 uct of the resistance in pounds and the speed 

 (ft-lb/sec) divided by 550. 



In the4LV/A^ model tests (8), the total drag 

 (Rt) was measured by a dynamometer at 

 varying speeds. By performing the calcula- 

 tions defining EHP, the horsepower needed 

 to propel ALVIN through a range of speeds 

 was found. A plot of these values, including 

 EHP, is shown in Figure 8.26. 



Another example of deriving required 

 horsepower was given by Daubin (18) for 

 General Motor's DOWB . In these calcula- 



X 



V) 



o 



z 



D 



o 



(3 

 < 



DC 



a 



m 

 O 



I 

 O 



33 



cn 

 m 

 -o 

 O 



m 



33 



Fig. 8.26 EHP curves for ALVIN. [From Ref. (17)] 

 396 



