tions DOWB's similarities to ALVIIS in fine- 

 ness ratio, Reynolds number and shape were 

 considered close enough to justify using the 

 same drag coefficient of 0.027, from this was 

 calculated: Drag, EHP and SHP. 



A first approximation of SHP required to 

 drive a submersible is presented by Rechnit- 

 zer and Gorman (19) as 



SHP = 0.005 V3 A2'3 

 where V = Speed in knots 



^2/3 = propelled displacement. An ap- 

 proximation of the weight in- 

 cluding water confined within 

 the fairing: = LBD/60 in. long 

 tons (2,240 lb); L = length, B = 

 breadth. D = depth in feet. 



From these examples it is apparent that 

 there are several ways to determine and 

 obtain the required SHP for a submersible: 

 The first involves off-the-shelf availability of 

 candidate motors and intuition, the second 

 encompasses model testing and a variety of 

 calculations from model tests of similarly 

 configured vehicles. In addition there are 

 other means proprietary to various manufac- 

 turers. Perry Submarine Builders uses a 

 method based on past vehicle performance 

 with various propulsion plants and, in some 

 manner, observes drag on the vehicle itself 

 instead of a model. (Personal communication 

 with F. Cunningham, Perry Submarine 

 Builders.) 



Regardless of the method used to derive 

 required SHP, the results are fairly consist- 

 ent: Low SHP is the rule. Where rated horse- 

 power data is available (58 submersibles), the 

 following groupings are found: 1-5 hp = 50%; 

 5-10 hp = 35%; 10-15 hp = 9%; 15-20 hp = 

 2%; the remaining 4%, AUGUSTE PICCARD 

 and BEN FRANKLIN, use 75 hp and 100 hp, 

 respectively. (These values are for main pro- 

 pulsion only and do not include thruster 

 values.) The low horsepower reflects not only 

 the undesirability of high speed, but also the 

 quite limited supply of electrical power 

 which is the only power source for a variety 

 of other tasks. 



The term V^ in the above equation is a 

 paramount consideration when high speed is 

 desired, because it represents a heavy toll 

 one must pay in power for merely a small 

 increase in speed. 



Consider the following for the submersible 

 BEAVER which, from reference (20), has a 

 A2/3 = 15. If BEAVER is to cruise at 2 knots 

 then by the formula: 

 SHP = 0.005 V3 A2/3 = 0.005 (2)^ (15) 

 SHP = 0.60 



If a 50 percent increase in speed (3 knots) is 

 desired, then the SHP required increases to 

 2.03, over a three-fold increase. Let us now 

 consider what this requires in the form of 

 electrical power. A 0.60-hp requirement is 

 equal to 0.45 kWh (hp x 0.745), while 2.03 hp is 

 equal to 1.51 kWh. An increase in speed, 

 therefore, calls for electrical power which is 

 in competition with other tasks equal to, or 

 exceeding, the importance of higher speed. 



CONTROL DEVICES 



The means of controlling a submersible's 

 maneuvering devices are as varied as the 

 devices themselves. At one end of the spec- 

 trum the control is entirely manual; at the 

 other end the necessary controls are so com- 

 plex that computer assistance is necessary. 

 Between these two extremes are combina- 

 tions of manual, manual-hydraulic, electro- 

 hydraulic and electrical. Instead of listing 

 each and every means used on individual 

 vehicles, which would be exhaustive, a repre- 

 sentative selection of vehicles is described. 



There is one area of commonality through- 

 out the field: All vehicles can be controlled 

 by one person. While several of the larger, 

 more complex vehicles have a co-pilot, the 

 second person is not required for basic con- 

 trol of the vehicle. The co-pilot serves mainly 

 to relieve the pilot and assist in special ma- 

 neuvers or functions. The similarity in tasks 

 between an aircraft crew and the crew of a 

 large submersible is, in many respects, very 

 close. 



While the major control functions occupy- 

 ing the operator are those when submerged, 

 there are certain functions some operators 

 must perform during launch and retrieval. 

 The great majority of vehicles place no re- 

 sponsibility on the pilot during launch or 

 retrieval other than to secure the hatch and 

 wait until the vehicle is in the water. Once it 

 is in the water and free of steadying lines 

 and lift cable, the operator's work and con- 



397 



