I. INTRODUCTION 



The use of E-M (electro-mechanical) cables in fixed ocean installa- 

 tions has become an area of concern to the Navy which has recently begun 

 to construct such installations on the deep seafloor. One major factor 

 in determining success or failure of militarily significant installations 

 is the proper use of cable, and its performing as specified. In order to 

 improve the technology in E-M cables for such installations, a thorough 

 look at past experiences, present technology, and into the future is 

 necessary. 



There are three types of cable in use in the ocean today, electrical 

 cables, mechanical cables, and E-M cables. For purposes of this study, 

 only E-M cables are considered. An E-M cable is defined as a cable used 

 in support of, a component of or part of a fixed ocean installation; 

 containing electrical conductors, either power or signal, or both; and 

 a strength member, under continuous or intermittent loading. The elec- 

 trical function of the cable is transmission and distribution of power, 

 or signal communication, or both. The strength member is for tensile 

 loading. A fixed installation includes such systems as cable arrays, 

 and manned or unmanned structures. 



An electrical cable with armor that serves only for protection, 

 rather than load bearing is not the type of cable to which this study is 

 addressed. Tow cables or cables used in ship or vehicular systems are 

 not included except where a problem associated with these cables is ap- 

 plicable to the E-M cables considered. Seafloor, or E-M ocean cables are 

 laid on the ocean floor and see only their own weight during handling and 

 deployment, but usually are under some additional tension when installed. 

 These cables may have a strength member, but the oceanic E-M cables are 

 considered in this study to a lesser degree than the other electro- 

 mechanical cables. 



Two types of suspended electro-mechanical cables are the objects of 

 this study. They are working E-M cable and structural E-M cable. The 

 working cable is one which supports a load in excess of its own weight 

 during repeated raising and lowering operations. It may be fixed at 

 both ends or may have one end fixed and the other free to rotate. The 

 load may be continuous or may be relaxed, e.g., when the load is set on 

 the ocean floor. A system used for support of a fixed installation would 

 be the Seafloor Deep Corer, which is approximately 8 tons in water, is 

 raised and lowered on a 1 1/2-inch-diameter cable which supplies power 

 and signals to the system when it is on the seafloor. A structural cable 

 is that part of the installations which is not generally raised and 

 lowered repeatedly, but remains in the ocean providing an electrical and 

 mechanical function. An example of such a cable is that used in surveil- 

 lance arrays between acoustic sensors. To maintain a given configuration, 

 the cable must be under tension. 



Although seafloor and suspended E-M cables have been used in the ocean 

 for years with a high degree of success in some applications, many new 

 uses are being conceived. It is these new requirements which are pushing 

 the technology into areas requiring the ultimate in reliability under the 

 most severe conditions. Considerable time and money are being spent on 

 design and handling each time an electro-mechanical cable is used for a 



