Soil Capability - (Weighting Factor: 3). The burial system must 

 perform in sand and clay, and it would be ideal if it could cut rock 

 as well. Concepts were downgraded significantly if they were limited 

 to either sand or clay. 



Steering J Control - (Weighting Factor: 3). Since the burial system 

 must be capable of burying previously laid cables, a good capability 

 for steering the machine to follow the cable is important. This factor 

 also impacts on cable damage probability. 



Target Weight/Size - (Weighting Factor: 2). Meeting the weight and 

 size target values is desirable from the standpoint of ship handling, 

 transportation, and ease of operation. 



Ship Support Impact - (Weighting Factor: 2). The requirement that 

 the system be operable from ships of opportunity was judged, taking into 

 account ship power, control, handling, and predicted deck space require- 

 ment s . 



State-of-the-Art - (Weighting Factor: 2). Since a cable burial system 

 is needed soon, concepts were downgraded if they required extensive re- 

 search and development to prove their validity, or if the probability of 

 success was judged to be poor. 



Obstacle Effects - (Weighting Factor: 2). The obstacles considered 

 in this category included buried or partially buried items such as rocks, 

 cables, or debris. Concepts were downgraded if encountering such an obsta- 

 cle would severely damage the machine or cable, or preclude continued 

 operation. 



Complexity - (Weighting Factor: 1). The complexity of the system 

 impacts mainly on reliability and maintainability of the system. A complex 

 system will require more comprehensive design and testing efforts, but 

 will have minor impact on the eventual success of the system. 



The selection process was done in two stages. The major subsystem 

 candidates (excavation, propulsion and running gear/subsystems) were 

 rated and selected, then the survivors were combined into the various 

 overall system candidates, and these candidates were rated. 



Excavation Subsystem (Table 7) 



The candidates under consideration include vibratory plowing, water 

 jetting, auger trenching, and trenching. For a climbmilling trencher, a 

 score of 6 is possible as a bonus for aiding in propulsion. Vibratory 

 plowing and wat-er jetting scored the highest, specifically because of 

 their low probability of damaging the cable, high probability of success, 

 and minimal effect of buried obstacles. Climbmilling bucket trenching 

 also scored well enough to be retained. Although the excavation method is 

 relatively complicated, the force assistance is a considerable benefit. 

 The other candidates were downgraded mainly in the complexity and effect 

 of buried obstacles categories. Vibratory plowing, water jetting, and 

 climbmilling bucket trenching are retained as candidate excavation 

 subsystems. 



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