Power System. Conventional integral power sources such as lead/acid 

 and silver/zinc storage cells are impractical for providing the power needed to 

 drive the electric motors. Consequently, a surface supported, air breathing 

 generator would provide power to the hydrocopter via a buoyant electrical 

 conductor. 



Miscellaneous Considerations. As is the case with the heavy-lift 

 submersible, the hydrocopter would have a load lifting system. It should be 

 simple in design and operation. A single hook, jettisonable in event of an 

 emergency, is one possible solution. 



A surface support vessel will be needed which is capable of lowering 

 and lifting the hydrocopter into and out of the sea. For short distances, 

 perhaps the hydrocopter can be towed to the offshore construction site. A 

 more detailed discussion of the hydrocopter can be found in Appendix C. 



Compared to the heavy-lift submersibles previously discussed, the 

 hydrocopter is much heavier 'dry weight in excess of 250,000 pounds), 

 bulkier (overall diameter of 41 feet), and dependent on a surface power 

 supply. The principal advantage of the hydrocopter is its considerable 

 lateral thrust capacity wnich could be used to augment the prime, surface 

 supported, load positioning and guidance svstem. 



CONCLUSIONS 



Three basic approaches for achieving a 20- to 30-ton lift at 6,000 feet 

 have been discussed. One approach, employing a bottom crawling vehicle, 

 has been discounted altogether — at least for loads of this magnitude. The 

 remaining concepts, heavy-lift submersible and hydrocopter, however, appear 

 to have potential as heavy load lifters. 



The hydrocopter not only is capable of lifting heavy loads (up to 

 30 tons), but also has substantial lateral thrust capability. The latter would 

 be an important consideration for load positioning. The hydrocopter could 

 conceivably function in concert as a work monitor with the tubular support 

 or cable lifting-lowering system. If needed, the hydrocopter NBTS could also 

 use its considerable thrust to assist in translating heavy, suspended loads to 

 the proper bottom construction site. The principle disadvantage of the 

 hydrocopter is its dependence on an external power source. Power would be 

 provided by surface generators through one or more electrical conductors. 

 Such conductors, made buoyant if possible, could entangle in the lifting- 

 lowering suspension system or break due to a sudden downward movement 



86 



