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with reference to the performance required for particular types of task. 

 It is possible that the answer may lie in a hybrid approach; in any 

 event it is probable that a greater degree of integration of the vehicle's 

 navigation and control systems is required. 



Nearly all vehicles built to date receive power and transmit data through 

 an umbilical. The diameter of the umbilical which governs the drag 

 it creates and therefore the propulsive power required by the vehicle 

 is partly determined by the diameter of the core which carries the power. 

 Minimization of vehicle power requirements through increased propulsive 

 efficiency, etc, therefore can lead to reduction in umbilical drag 

 which in turn reduces vehicle power consumption. Efforts devoted to 

 improving propulsive efficiency and to low power on board systems are 

 therefore indicated. Umbilical diameter is minimized if efficient 

 data transmission at high data rates requiring few transmission lines 

 is used. Fibre optics offer a possible solution, but the mechanical 

 properties of the fibres when continuously flexed and the matching of 

 their modulii to the other cable materials require study. The effects 

 of umbilical drag can be reduced by operating the vehicle from an under- 

 water garage, or eliminated if free swimming vehicles can be developed. 



The first stage, which has proved difficult in the past, is to provide 

 sufficient onboard power to ensure useful mission durations and at the 

 same time retain maximum maneuverability. Conventional batteries do 

 not appear to hold the answer. Other, more expensive battery systems 

 may have greater capacity per unit volume but these often have problems 

 in production and disadvantages in use. Hydrocarbon power packs utilizing 

 a Stirling or Rankine engine have been suggested but could have problems 

 due to the size and weight of the propulsion unit with fuel and oxidant 

 for long duration missions. It might also be worthwhile examining once 

 again the prospects of using 100 percent hydrogen peroxide as a fuel. 

 Until a proper study of power requirements involving power packs, 

 recharging, and measures to reduce power requirements has been carried 

 out, a sound approach to the problem will not be possible. 



A further problem is through water transmission of information. For 

 manned free-swimming submersibles information density requirements are 

 relatively low and the method of communication has traditionally been 

 acoustic. Acoustic methods have problems in this application however 

 because of diffraction and distortion effects in thermal layers, shadow 

 zones and low propagation velocity. Band width is too narrow to transmit 

 all sensor, control and video data at present needed for unmanned 

 operation. Electro magnetic transmission underwater is often dismissed 

 because the attenuation rates are so high at useful frequencies. 

 However, although far-field radiation will not propagate through sea 

 water, near-field radiation may be a possibility within a limited 

 envelope (say 100 meters) . 



The operator station is the area which has been most neglected in remote 

 control systems. The whole rationale of manned submersibles depends 

 on the need to have the human being close to and moving round the 

 worksite, so he can get a 'feel' for it. This feel is removed in the 

 present operator stations which at best are not much more than one or 

 two monochromatic TV screens and a joystick. With such a system unless 



