also feel that the instrument modules can be passed through 

 the treads without damage either to modules or to tread 

 faces. 



As for the size of "Caterpuller" required for this 

 application, (5) reports that a track loading of 500 pounds 

 per inch is a reasonable design value. With such a loading 

 "tractive pulls of from 100 to 300 pounds per inch of effec- 

 tive track have been achieved." Thus, to provide a maximum 

 pull of 10,000 pounds, an effective track length of 33 to 100 

 inches would be required. 



Figure 8 shows that at one or two knots, the tension in 

 the cable, attributable chiefly to the combined weight of the 

 body and cable is only about 6000 pounds. If the traction 

 unit is designed to inhaul only at low towing speeds, the 

 power required would not be large. Since inhaul and payout 

 at frequent intervals should not be necessary, it would seem 

 vmreasonable to design for inhaul at the highest towing 

 speed. Even if the inhaul load is not high, however, there 

 is still a question regarding the normal loading that can be 

 applied to the cable by the tread faces. This question arises 

 as a result of the fairing. Even though the fairing is of 

 rubber and of a thickness equal to eight-tenths the cable 

 diameter, prevention of slippage of the cable relative to 

 the fairing has not been demonstrated. The friction coeffi- 

 cient for the armored cable in contact with the tread faces 



49 



