Sohreiher J Bentkowsky and Kerr 



Nc = C, cos tt^ + Co sin g. 



F = 



r C^_ sin Cfg - Cq cos <x^ 



and 



■^shroud ~ "^822 8 -^SB 



The moments on the shroud are the product of the shroud force and 

 the distance of the shroud center from the center of the axis system 

 as shown in the moment equations. 



THRUSTER FORCES 



The propulsion system of the DSRV consists of a single con- 

 ventional screw propeller for axial thrust and four ducted screw 

 propellers arranged in forward and aft pairs for lateral and normal 

 thrust. This system provides the vehicle with five degrees of 

 maneuvering freedom (heave, sway, surge, pitch and yaw) and pro- 

 vides forces and moments sufficient to meet hovering requirements 

 in currents of the order of one knot. The control of the sixth degree 

 of freedom, roll, is provided by the trim and list system, A com- 

 plete treatment of the development of the maneuvering system is 

 contained in Ref. 7. The following treatment will present the data 

 used in the simulation with a little explanation of its development. 



Main Propeller 



The main propeller is a 6-foot diameter, wake adapted, 

 three-bladed propeller with a blade area ratio of 0. 24 and a maxi- 

 mum speed of 1.64 revolutions per second. 



For estimates of the vehicle maneuvering performance the 

 propeller thrust and torque characteristics are required for ahead 

 and astern motion of the vehicle and for positive as well as negative 

 propeller rpm. "Behind-the- ship" tests of the DSRV propeller were 

 performed for all four operating modes at the Naval Ship Research 

 and Development Center (Ref. 8). 



The curves of the thrust and torque coefficients. Fig. 6, are 

 typical for ahead and astern operation of a propeller and can be 

 expressed in the form 



K = a +bj + cJ^ 



1138 



