CONCLUSIONS 



It is important to note that no consideration Inas been given in the 

 preceding analyses to damping. The added mass of the water column above 

 the load and the water columns above the rubber pipe protectors will serve 

 as buffers against undue stresses being imposed at the support point. The 

 environment is one of random shock and vibrations, making dynamic stresses 

 difficult to determine. However, the fact that there is damping would tend 

 to decrease the dynamic loads at the points of maximum stress. The low 

 frequency, high amplitude motions of the ship would be reduced to an 

 acceptable maximum by a well-designed damping system. 



To assure that the drill pipe on the Glomar Challenger would not 

 resonate, ordinary rubber pipe protectors were installed every 5 feet along 

 the pipe. It was predicted and later proven at sea that the protectors would 

 sufficiently dampen any motion of the ship and thereby eliminate resonant 

 buildup. A side benefit was that of eliminating the need for a tapered drill 

 string. Similar approaches have been either suggested or attempted; of the 

 latter, all have proven invaluable in avoiding resonance and increasing the 

 safety factor. 



Longitudinal oscillations are the most severe and, fortunately, the 

 best known. These vibrations have been given a fair amount of attention in 

 the preceding pages. It is safe to conclude that the proper drill string design 

 with an efficient damping system, combined with a ship of suitable motion 

 response characteristics, will successfully lower and lift heavy loads to depths 

 of 6,000 feet. A ship the size of a T-2 tanker with 10-3/4-inch CD pipe is 

 particularly promising and could meet any reasonable design criteria. There 

 is no question that a floating platform, such as FORDS, could handle loads 

 of this type in all but extraordinary seas. 



138 



