Plow Insertion: Difficulties in inserting the plow in the seafloor 

 require about 1 nautical mile (nm) before the plow is fully engaged. The 

 cable is left partially buried in the interim. 



Availability: Because the plow relies on one or two ships for opera- 

 tion (the French ship may not be capable of supporting Sea Plow IV) , and 

 because the plow is owned by private industry, the cable plowing system 

 is not readily available to the military. 



The only other method that has been used to bury cables in the 

 deep ocean is water jetting. Repeaters that had not been buried by the 

 Sea Plow were jetted into the sediment. In one case a jet pump was held 

 by a submersible manipulator [2], and in the other case a specially de- 

 signed jet fixture was mounted on the end of a drill string [3]. Both 

 attempts were successful, but this type of operation is very slow (and, 

 therefore, not suitable for burying hundreds of miles of cable), expensive, 

 and has been accomplished only in sandy bottoms. In addition, submersible 

 operations of this type are quite dangerous. The drill string mounted 

 jetting device is limited to about 600 feet because the string excursion 

 becomes too great to control. 



It is clear, then, that the Navy requires an improved means of bury- 

 ing deep-ocean cable installations in the seafloor. The approach taken 

 to complete the first phase of this program, and reported here, is the 

 following. 



1 . Establish the operational requirements that the improved cable 

 burial system must meet, such as burial depth, water depth, soil type, 

 available surface support, and characteristics of present and future cable 

 installations which must be protected. 



2. Analyze existing techniques for burying cables (and pipelines) 

 underwater and on land, identifying methods that are applicable to the 

 deep -ocean cable burial problem at hand. 



3. Define deep-ocean burial system concepts that utilize feasible 

 burying means previously identified. Consider various methods of self- 

 propulsion, and compare these with a passive (towed) system. 



4. Specify, quantify where possible, and analyze the system concepts, 

 taking into account their capabilities vis a vis established operational 

 requirements, physical embodiment, power requirements and efficiency, 

 problem areas requiring preliminary research or development , engineering 

 and technical difficulties, shipboard requirements, and probability of 

 success. 



5. Select the most promising concept or concepts, and establish 

 development plans necessary to bring the conceptual system to the 

 experimental hardware stage. 



While it has been demonstrated that burying a cable provides an ex- 

 cellent measure of protection against fishing activities, it is clear 

 that not all cable failures can be avoided. Failure of a buried cable 

 presents several problems unique to buried cables; that is, how is the 



