the right stick. The information shown on 

 the ICAD can be seen from the labels on the 

 general component layout. 



Of the seven control systems described, 

 combinations thereof may be found in sister 

 submersibles. It has been emphasized re- 

 peatedly that a number of options are availa- 

 ble to the operator to gain more motions 

 than the control system alone provides. 

 While the ICAD system is a wonder of tech- 

 nology, it is unnecessary for the kind of 

 maneuverability required of most submers- 

 ibles. Indeed, an ICAD system wouldn't fit in 

 the majority of vehicles, and its cost alone 

 exceeds many times that of all but one or two 

 government-owned submersibles. 



With operational experience many of the 

 propulsion and control devices listed in this 

 chapter were found unnecessary on some 

 vehicles and inadequate on others. STAR III, 

 for example, eventually discontinued using 

 its rudder because it was awkward and slow 

 to react and adequate control could be ob- 

 tained by the thrusters alone. Because the 

 majority of submersibles were one-of-a-kind 

 prototype models, they reflected the design- 

 ers' best initial thoughts on propulsion and 

 control and the then state-of-the-art in avail- 

 able hardware. Because few vehicles are sim- 

 ilar in design and mission, there are only 

 broad precedents on which to draw, and, in 

 many instances, the operating life of the 

 vehicle was too short to evolve the "best" 

 approach to maneuvering and control. 



The benefits a submersible may gain under 

 an extended operational life is related by 

 Goudge (21). In this example the submersible 

 PISCES II had worked for some time in the 

 areas off Victoria, B.C., where strong cur- 

 rents were not a severe operational consider- 

 ation, but with its transfer to the North Sea, 

 that harsh environment brought to light de- 

 ficiencies theretofore unappreciated. 



"A speed of some four knots was 

 expected for PISCES II, but the craft 

 ivas so unstreamlined and the appen- 

 dages caused so much drag, that 1 V4 

 knots only was achieved. This and the 

 fact that three steps of speed control 

 only was provided, which meant that 

 steering by differential use of the 

 screws was very imprecise, caused 



great difficulties in maneuvering in 

 strong currents tvhich are common 

 round Britain and even in the middle 

 of the North Sea. The first stage was to 

 measure the bollard pull and, by 

 spring balance, the towing pull needed 

 to produce i V4 knots. From this, the 

 overall efficiency w€is found to be 14 

 percent. By fitting cowling extensions 

 and flow straighteners this was raised 

 to 28 percent. A false buoyant nose 

 was fitted forward, Thyristor controls 

 were provided to give stepless speed 

 control and the motor windings al- 

 tered from compound to series, with 

 higher ratio gear box between motors 

 and propellers. 



The net result of till these has been 

 to push the top speed up to 4.1 knots 

 on the log with an overall efficiency of 

 some 60 percent. Water tunnel tests at 

 Newcastle University have also showed 

 the way to still further improvements 

 should these become economic. The 

 costs of the greater streamlining that 

 would be needed are quite heavy. 



During the above improvements, op- 

 portunity was taken to try improved 

 brushes, gear and operating fluid (the 

 motors run at ambient sea pressure in 

 a special oil). Taken all together, the 

 above measures have reduced a heavy 

 maintenance load to almost nil, mean 

 time between failures having changed 

 from a few hours to a still unknown 

 but very large number. (The only fail- 

 ure since, in several hundred hours of 

 running, has been a cable fault. ^ 



Such modifications and improvements are 

 commonplace in submersibles, and more can 

 be expected as they find wider ranging and 

 longer undersea employment. 



REFERENCES 



1. Strasburg, D. W. 1965 A submarine for 

 research in fisheries and oceanography. 



Trans. Mar. Tech. Soc. and Amer. Soc. 

 Limnology and Oceanog., 14-17 June 

 1965, Wash., D.C., v. 1, p. 568-571. 



2. Taggert, R. 1969 Marine Propulsion. 

 Gulf Pub. Co., Houston, Tex., 368 pp. 



406 



