Shipyards are not particularly well-suited for constructing platforms. In 

 addition, special facilities are needed for alterations and repairs on platforms, 

 especially if drydocking is required. 



Mobility. There is no question that ships are more mobile than any 

 platform yet built. In fact, many platforms have no means of propulsion 

 and must be towed between work sites. 



Platforms can be designed to accommodate a propulsion system. A 

 large amount of power is required to move a platform, since the hull con- 

 figuration is not the best for movement through the water. It can be safely 

 assumed that unless a tremendous (almost unrealistic) amount of power is 

 provided, a platform is considerably slower than a ship. 



Accommodations. Small ships are out of the question for the heavy- 

 lift project simply because they do not have enough room for all of the 

 equipment needed for a cable system or pipe string and derrick system. 

 Intermediate size ships may be large enough to accommodate the derrick 

 and pipe string or cable equipment, but there are some limitations on the 

 volume of the load. In general, any vessel discussed in this report is large 

 enough to accommodate the lift equipment of any candidate system. 



Platforms are or can be considerably larger than ships. They are 

 clearly superior to ships in that they are not restricted by beam width and 

 deck space. Moreover, it is much easier to build a platform with a large 

 centerwell. For a ship, there is obviously a restriction on how large the well 

 can be; for instance, the Glomar Challenger has a beam of 65 feet, yet the 

 well is only 20 feet by 22 feet. 



Type of Operation. There appear to be two general types of 

 operations that could be encountered in heavy-lift operations: (1 ) fast 

 placement or recovery of objects on the ocean floor or (2) a test operation 

 where a subsea system or component is held at depth for testing (similar to 

 the FORDS platform'' ). As far as the surface vessel is concerned, these 

 distinctly different operations are not compatible. For the first type of 

 operation, i.e., lowering or recovery, a ship would be satisfactory — 

 assuming the crew were given some leeway in the timing of the operation. 

 For the second type of operation, simply holding a test specimen, there is 

 no choice but to use a platform since the test could take some time and the 

 support craft would have to be capable of withstanding the severest sea 

 states. In this respect the platform is more versatile, since it can perform 

 both types of operations. 



15 



