Ch. 4— Technologies for Exploring the Exclusive Economic Zone • 149 



The foregoing prices are quoted for new vehi- 

 cles only. However, in today's depressed offshore 

 service market, there are numerous opportunities 

 for obtaining used manned and remotely operated 

 vehicle systems for a fraction of the prices quoted 

 above. Likewise, support ships can be purchased 

 at similar savings. This generalization does not ap- 

 ply to the towed or the hybrid systems, since they 

 were built by their operators and are not commer- 

 cial vehicles. 



Capabilities 



The environmental limits within which a vehi- 

 cle can work are determined by such design fea- 

 tures as operating depth, speed, diving duration, 

 and payload. These factors are also an indication 

 of a vehicle's potential to carry equipment. The ac- 

 tual working or exploration capabilities of a manned 

 or unmanned vehicle are measured by the tools, 

 instruments, and/or sensors that it can carry and 

 deploy. These capabilities are, in large part, de- 

 termined by the vehicle's carrying capacity (pay- 

 load), electrical supply, and overall configuration. 

 For example. Deep Tow represents one of the most 

 sophisticated towed vehicles in operation. Its equip- 

 ment suite includes virtually every data-gathering 

 capability available for EEZ exploration that can 

 be used with this type of vehicle. On the other hand, 

 there are towed vehicles with the same depth ca- 

 pability and endurance as Deep Tow but which 

 cannot begin to accommodate the vast array of in- 

 strumentation this vehicle carries, due to their de- 

 sign. Table 4-8 is a current worldwide listing of 

 towed vehicles and the instrumentation they are de- 

 signed to accommodate. Towing speed of these ve- 

 hicles ranges from 2 to 6 knots. 



Tethered, free- swimming ROVs offer another 

 example of the wide range in exploration capabil- 

 ities available in today's market. Vehicles with the 

 most basic equipment in this category have at least 

 a television camera and adequate lighting for the 

 camera (although lighting may sometimes be op- 

 tional). However, there is an extensive variety of 

 additional equipment that can be carried. The 

 ROV Solo, for example, is capable of providing 

 real-time observations via its television camera, 

 photographic documentation with its still camera, 

 short-range object detection and location by its 

 scanning sonar, and samples with its three-function 



grabber (i.e., manipulator). The vehicle is also 

 equipped for conducting bathymetric surveys. As- 

 suming it is supported by an appropriate subsea 

 navigation system, it can provide: 



• a high-resolution topographic profile map on 

 which the space between sounding lanes is 

 swept and recorded by side-looking sonar, 



• a sub-bottom profile of reflective horizons be- 

 neath the vehicle, 



• a chart of magnetic anomalies along the tracks 

 covered, 



• television documentation of the entire track, 



• selective stereographic photographs of objects 

 or features of interest, and 



• the capability to stop and sample at the sur- 

 veyor's discretion. 



With adequate equipment on the vehicle and 

 support ship and the proper computer programs, 

 the entire mapping program, once underway, can 

 be performed automatically with litde or no human 

 involvement. At least a dozen more competitive 

 models exist that can be similarily equipped. 



In addition to ROVs of the Deep Tow and So7o 

 class, several vehicles have been designed to con- 

 duct a single task rather than multiple tasks. One 

 such vehicle is the University of Georgia's Con- 

 tinuous Seafloor Sediment Sampler, discussed 

 earlier in the section on nuclear methods. 



Untethered, manned vehicles are, for the most 

 part, equipped with at least one television camera, 

 still camera, side-looking sonar, and manipulator, 

 and with pingers or transponders compatible with 

 whatever positioning system is being used. The ab- 

 sence of an umbilical cable has an advantage that 

 received little attention until the Challenger space 

 shuttle tragedy in 1986. Challenger's debris was 

 scattered under the Atlantic Ocean's Gulf Stream, 

 which flows at maximum speed on the surface but 

 decreases to less than 0.25 knot at or near the bot- 

 tom. Once the manned submersibles used in the 

 search descended below the swift flowing surface 

 waters (upwards of 3 knots), they worked and ma- 

 neuvered without concern for the current. The 

 ROVs used, on the other hand, were all tethered, 

 and, even though the vehicle itself might be oper- 

 ating within litde or no discernable current, the um- 

 bilical had to contend with the current at all times. 

 This caused considerable difficulty at times during 

 the search operation. 



