Propulsion Subsystem (Table 8) 



Propulsion system candidates include towing, tracks /wheels, thrusters, 

 and the alveolator concept. Note that the power input for towing is zero 

 since it is assumed that the support ship already has the shaft horsepower 

 for towing. Towing was downgraded mainly in the limitations it places 

 on the support ship and in steering/control, which impacts on its ability 

 to bury previously laid cables. Nevertheless, towing scored high in other 

 areas and is retained as a propulsion candidate. Tracks /wheels scored 

 low in the state-of-the-art and complexity areas, but scored well enough 

 in control and ship support requirements to be retained. Thrustors scored 

 the highest in spite of the high power requirement. The alveolator concept 

 was discarded due to its complexity, the fact that it is unproven, and 

 the predicted difficulty in controlling its direction. Thus, the remaining 

 propulsion concepts are towing, track/wheel, and thrusters. 



Running Gear Subsystem (Table 9) 



The potential candidates include lubricated and unlubricated skids, 

 rolling elements (wheels or tracks) , and a water cushion vehicle (WCV) . 

 The WCV scored very low in power, complexity, and state-of-the-art areas, 

 and, therefore, was eliminated. Of the remaining concepts, it remains 

 questionable whether or not lubrication will effect the predicted force 

 reduction; therefore, lubricated skids were rated questionable in the 

 state-of-the-art parameter. Nevertheless, the score was high enough to 

 retain lubricated skids along with unlubricated skids and rolling elements. 



Overall System Evaluation (Tables 10 and 11) 



The excavation, propulsion, and running gear subsystems that were 

 retained were combined in all possible ways to select the best overall 

 concepts. Table 10 presents a force and power summary of the twenty-one 

 combinations. Note that the ship power required for towing is not included 

 in the power estimate. Also, the concepts with track/wheel propulsion 

 have rolling elements for the running gear subsystem because of the 

 propulsion subsystem. 



Each concept is rated in Table 11. The results show that all the 

 concepts that included trenching as the excavation means scored low 

 no matter what the other subsystems were. These low scores are due mainly 

 to complexity, obstacle effects, chance of success, and, to some extent, 

 power. Towing also scored low in all combinations because of the lack 

 of steering control, and the impact on ship support requirements. The 

 four best scoring combinations are: 



Concept 



Excavation 

 Subsystem 



Propulsion 

 Subsystem 



Running Gear 

 Subsystem 



16 and 17 



Water Jet 



Thruster 



Skids (lubricated 

 or unlubricated) 



13 and 14 



Vibratory Plow 



Thruster 



Skids (lubricated 

 or unlubricated 



43 



