compartments by radial bulkheads. Water ballast is pumped between the 

 compartments, subjecting the cylinder to a moment, and thereby forcing 

 it to rotate. Wire rope lines attached to the cylinder wind around it as it is 

 turning. The system is illustrated in Figure 3. 



A second type of unconventional surface craft is patterned after the 

 "Flip" vessel used by the Navy to test sonar. It is discussed briefly. 



Surface Independent 



The surface independent systems are virtually free of surface support 

 during operation. Two basic concepts of surface independent systems are 

 investigated in this report: (1 ) free ascent/descent and (2) winch-down. 



Free Ascent/Descent. Free ascent/descent techniques are charac- 

 terized by the need for slight negative buoyancy during descent and slight 

 positive buoyancy during ascent. Two candidates of this category are 

 considered in this study: (1 ) the hydrochute and (2) the buoyed load. 



The hydrochute is simply an underwater parachute. It is attached to 

 the load and the entire assembly is released. The chute provides enough drag 

 to slow the load to an acceptable terminal velocity. 



In the buoyed load concept, the negative buoyancy of the load is 

 compensated for by a buoy system. The buoy system, which may or may 

 not be expendable, can be adjusted for a calculated amount of lift for 

 descent (slightly negative) or ascent (slightly positive) based on the 

 permissible accelerations to which the load and/or buoys may be subjected. 

 Only the buoyed load concept is considered in the systems effectiveness 

 analysis. 



Winch-Down. An excellent example of the winch-down concept is 

 the Manned Underwater Station proposed by General Dynamics."' In this 

 system, the load, which is slightly buoyant, pulls itself down a cable anchored 

 to the bottom. A winch mounted on the load provides the power for the 

 lowering process. If need be, the load can be made positively buoyant by 

 adding buoys of suitable size and characteristics. 



The candidate systems are discussed in much greater detail in the 

 following pages. The merits and liabilities of candidate subsystems common 

 to all of the basic lifting and lowering systems are also discussed. 



10 



