FINDINGS 



As a result of the investigation described above, it was found that: 



1. The theoretical analysis presented by Arthur D. Little, Inc., in Project Trident 

 Technical Report No. 1370863 of the Bureau of Ships' was readily adaptable to a 

 design procedure for heavily loaded cables for deep ocean emplacement or recovery 

 operations. 



2. This design procedure is relatively straightforward, but the results of its applica- 

 tion require confirmation by prototype measurements. 



3. The most important unknowns in the input parameters for the design procedure are 

 the coefficients of drag and virtual mass, which at this stage must of necessity be 

 estimates, again requiring confirmation by prototype measurements. 



4. For the two prototype examples given, the operations are unsafe with respect to 

 the specified maximum allowable dynamic stresses when the load is between zero and 

 approximately 200 feet below the ocean surface. 



5. Using polypropylene cable, there exists a possibility that under certain conditions 

 of motion of the working vessel the operation will again become unsafe at depths on 

 the order of 5, 000 feet and greater. The reason is not difficult to visualize. As the 

 length increases the natural period also increases, eventually corresponding to periods 

 of the exciting waves. If the damping is small, very large stresses may be induced by 

 relatively small input amplitudes. 



CONCLUSIONS 



It is concluded that the proposed design procedure is applicable to heavily 

 loaded cables in deep ocean emplacement or recovery operations. However, the 

 results of its application may not be considered rigorous in view of the estimates of 

 values of coefficients of drag and mass required for the calculations. In order to 

 make the design procedure applicable to a prototype situation with a greater degree 

 of confidence, it is considered necessary to make measurements of cable tensions 

 and load and ship motions during a full-scale operation to provide a basis for com- 

 parison between theory and prototype. 



ACKNOWLEDGMENTS 



Acknowledgment is made to NCEL personnel for their assistance in the 

 preparation of this report: to Mr. W. L. Wilcoxson for assistance in the analysis 

 given in Appendix B; to Mr. R. E. Jones for valuable discussions in relation to the 

 practicalities involved in lowering heavy loads to the deep ocean floor; to Mr. B. J. 

 Muga for overall guidance of the task effort and the preparation of Appendix D; and 

 to Mr. Richard Tu for preparation of Appendix E. 



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