POSITIONING AND GUIDANCE OF LOADS 



Accurate placement of ocean bottom resting loads has not necessarily 

 been a serious requirement in the past. Emplacement of NCEL's Submersible 

 Test Units, for example, requires only that the bottom site is reasonably flat, 

 that the bottom sediments have sufficient strength to support the weight of 

 the test rack, and that the coordinates of the surface ships, during emplace- 

 ment, be known within the degree of accuracy provided by LORAC. Future 

 sea floor installations, however, may require very precise alignment of two or 

 more construction modules. The positioning of the first module in the 

 complex may not be as critical as the positioning for those which follow. The 

 first unit will be positioned at a site which is reasonably flat, where turbidity 

 is at a minimum, and where the soil has the desirable strength properties. 

 Subsequent units must mate with those emplaced with a fairly high degree of 

 precision. 



Concepts proposed as feasible for positioning and guidance systems 

 include: 



1 . Manned and unmanned submersibles capable of grasping 

 suspended leads and translating and/or rotating them for accurate 

 alignment. 



2. Multiple underwater winches, mounted either on the load or 

 anchored to the sea floor, which would be used to position modules over 

 preselected sites. 



3. Bottom crawling vehicles which would depend upon tractive 

 force for displacing loads. 



4. Dynamic ship positioning systems sensitive enough to provide 

 accurate displacement of loads suspended 6,000 feet below. 



5. Guidelines and templates similar to those used in the offshore 

 oil industry. 



It is too early in the technology of underwater construction to state 

 with certitude the necessary alignment tolerances. The Deep Ocean Technology 

 (DOT) program TDP can serve as a point of departure. As previously stated, 

 this document specified the following alignment tolerances for 10- to 30-ton 

 loads to be handled by the near bottom transport subsystem (no tolerances 

 were specified for positioning loads handled by the lifting/lowering subsystem): 



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