Cruising and Hovering Response of a Tail-Stabilized Submersible 



because of the extreme sensitivity of the 

 hovering control and motions of the ve- 

 hicle to small positive or negative buoy- 

 ancy forces and vertical currents. It 

 also will be difficult to apply in the hor- 

 izontal plane where large lateral cur- 

 rents can act. In these cases, control 

 saturation can cause loss of hovering 

 control of the inherently unstable sub- 

 mersible. 



The second method is to increase 

 the inherent vertical plane hovering sta- 

 bility of the vessel by increasing its 

 metacentric height. The larger meta- 

 centric pitch moment acts as an inher- 

 ent pitch angle control, and a reduction 

 in cruising capability can be avoided by 

 increasing the maximum elevator force 

 coefficient \z'A • b . However, in hori- 

 zontal plane motions where metacentric 

 yaw moments are absent, large sway- 

 to-yaw coupling effects cannot be avoided 

 with the tail-stabilized vessel. 



O.IO 0.30 



Fig. 17 - Effect of metacentric 

 height on hovering heave ma- 

 neuver response for otherwise 

 standard run conditions 



Another approach to the design of 

 a submersible which must cruise and 



hover also has been considered. If all appendages are confined to lie within the 

 maximum hull radius, this is to use bow and stern stabilizers which are hydro- 

 dynamically equivalent. A design of this type is inherently stable with respect 

 to all equilibrium hovering conditions, and its fore -aft symmetry eliminates one 

 source of hydrodynamic coupling that is present in the tail-stabilized submers- 

 ible. The elevators can be part of the stern stabilizers for better turning and 

 diving effectiveness in cruising. The bow stabilizers are not expected to have 

 any detrimental influence on cruising performance. In particular, they do not 

 affect cruising stability, and may have a beneficial effect on turning ability. 



VII. ACKNOWLEDGMENTS 



The author wishes to thank Mrs. Kae Wilkens, Mr. Conrad Sedlak, and Mr. 

 Herant Deroian for their assistance in preparing this manuscript. 



VIII. REFERENCES 



1. Strumpf, A. and Eda, H., "Vertical Plane Cruising and Hovering Limit Ma- 

 neuvers of a Tail-Stabilized Submersible," Davidson Laboratory Report No. 

 1132, July 1966 



2, Feldman, S. and Cathers, L., "Design of the Deep Submergence Rescue Ve- 

 hicle," prepared by U.S. Navy Special Projects Office 



303 



