/ 



20,000 ft). That vessel has demonstrated the capability to apply a 

 lifting force estimated at 36 MN (8 x 10 lb) in 5,100 m (17,000 ft) 

 water depth. However, the Glomar Explorer is one of a kind, is quite 

 costly to mobilize, maintain, and operate, and may not be available when 

 needed for OTEC anchor emplacements. 



The idea of dividing the anchor into components or building blocks 

 as a means of reducing the payload weights was referred to above when 

 discussing the possibility of anchor emplacement by drillship. The idea 

 of adding buoyancy to the anchor during lowering was alfo investigated 

 as a possible means of facilitating anchor emplacement by drillship. 

 Light ipetroleum products (e.g., aviation gasoline), syntactic foams, and 

 air-filled pressure hulls were all considered as possible sources of 

 buoyancy. Buoyancy did serve to reduce the net static load on the lift 

 system; however, the added mass of «"he buoyancy also acted to increase 

 the dynamic forces arising from vessel motion. This evaluation of buoy- 

 ancy assist in anchor handling showed that the probability of developing 

 a snap-load condition when lowering the complete 18 MN anchor by drill- 

 ship, assuming no motion compensation, was quite high. It was also 

 determined that buoyancy-assist in handling 3.6 MN (0.8 x 10 lb) anchor 

 components by drillship (again assuming no motion compensation) would 

 make technically feasible the controlled lowering of those components to 

 water depths of 6,000 m (20,000 ft). A buoyancy system using air-filled 

 pressure hulls, reusable for lowering several OTEC anchors, is the best 

 buoyancy assist approach. However, this system requires five trips to 

 the seafloor to complete the anchor installation. In addition, a sophis- 

 ticated seafloor positioning control system would be required in order 

 to assemble the anchor components on the seafloor. 



In summary, techniques and systems for contrclled lowering and 

 emplacement of the 18 MN OTEC ?r.rhor are technically feasible, but will 

 prove complicated and expensive. 



Initially, free-fall emplacement of 18 MN anchors, though con- 

 sidered, was not highly regarded because of apprehensions regarding 

 stability during free-fall and structural integrity on landing. The \ 



