in importance, has the furthest reaching effect on the burial system 

 concepts. Because available ships have limited weight -handling and thrust 

 capabilities, a smaller, lighter -weight system is required. Force reduction 

 techniques and/or elimination of towing for propulsion will be necessary. 

 The burial system must be capable of burying previously laid cables since 

 the support ship will not necessarily be a cable layer. Surface support 

 systems must be modularized and self-contained such that they can be read- 

 ily installed on a variety of ships. A deck-handling system and portable 

 power generation system must be supplied. The importance of not damaging 

 the buried cable increases, as the support ship may not have a cable repair 

 capability. Many specific requirements, discussed later, result from this 

 general operating requirement. 



c. The system must bury cable in all seafloor soils except rock and 

 coral. 



Most deep -ocean cable routes occur on sand, silt, or clay bottoms. 

 Because of the areal variability of soil type and the difficulty of 

 changing to different burial systems in mid-operation, the selected burial 

 system must be capable of operating in all seafloor soils. Bottom-trawling 

 techniques cannot be used in rocky areas; therefore, cable burial in rock 

 is not required. Nearshore rock and coral cable route installations are 

 being developed separately. 



d. The burial machine power requirement must not exceed 500 hp. 



Although this value is somewhat arbitrary, this power level is 

 within current capabilities of power generation, distribution, and cable 

 and connector technology. If the power load is much higher than 500 hp, 

 a higher frequency distribution system would be desirable to save trans- 

 former weight [4]. This would require non-standard components which would 

 adversely affect the simplicity and reliability of the system. Higher 

 voltage levels could be used to reduce the conductor size, but cable and 

 connector insulation would present problems. Also, a higher power level 

 would require a larger power generation system which impacts on the ship 

 support requirement discussed earlier. 



e. The cable burier must be capable of avoiding minor obstacles. 



This requirement is essential to the integrity of the burying machine 

 and of the cable. Minor obstacles include glacial erratics (boulders 

 deposited by melting glaciers), debris, small rocky areas, reefs, or 

 depressions. An obstacle detection system will be required, that can feed 

 information to the burier control system. Large obstacles, such as exten- 

 sive rocky areas, ridges or valleys, will have to be avoided by employing 

 carefully selected and investigated cable routes. 



f. Repeaters must be buried. 



Repeaters occur only occasionally, and, if they were left unburied, 

 a large measure of protection would still be afforded to the cable system. 



