3. Corrosion of the component materials. 



At first, DIVERCON engineers used a lift device consisting of an open-ended 

 buoyancy chamber equipped with a lifting hook. The diver operator could 

 add gas to the chamber for increased lift and could decrease lift by bleeding 

 gas through a vent valve. The buoyancy chamber, however, proved to be 

 unstable. In lift tests, divers discovered that they would either add or 

 remove too much air, resulting in the buoy/load assembly accelerating 

 upward or falling to the sea floor. The adjustment for the desired state of 

 neutral buoyancy was not readily achieved. The developers next tried a 

 "tethered lift" system using the same sky hook principle, but with the 

 buoyancy chamber at all times tethered to the bottom with a two-point 

 moor (Figure 8). One mooring point was a portable anchor equipped with 

 five cylindrical variable ballast tanks which could be blown dry to reduce 

 the submerged weight of the anchor and which, when flooded, would 

 provide 2,000 pounds of deadweight. The other moor was provided by the 

 steel/concrete anchor clump of the DIVERCON habitat. 



A hydraulic winch mounted in the bottom of the lifting chamber 

 served two functions; (1 ) lifting and lowering of the prefabricated habitat 

 ring modules and (2) displacement of the chamber along the trolley line 

 connecting the two mooring points. The winch runs on hydraulic power 

 supplied from the control console by a hydraulic pump and electric motor. 

 In shallow water test, the tethered lift system proved to be a workable 

 scheme for providing both lateral and vertical displacement of the ring 

 modules. 



The sequence of events for mating the ring modules consist, first, of 

 coarse rotational alignment using the painted pattern on the module extension 

 as a guide. A series of fluted rods projecting from the lower module then 

 engage the edge of the upper module. Thus, translational guidance is assured 

 between modules. Two V-blocks insure that the appropriate guide rods are 

 engaged and also provide the final rotational alignment. It is estimated that 

 divers utilizing this system were able to align 10-foot diameter modules to 

 within a tolerance of + 1/8 inch. 



After a thorough survey of commercially available latch and fastening 

 devices, a drawhook container latch was selected since it best met the required 

 criteria: strength, durability, ability to provide sufficient force to effect a 

 seal between modules, and easy operability by free-swimming divers. The 

 first choice from among several candidate sealants was an elastomeric sealing 

 tape of 1/4-inch thickness used in conjunction with a silicone grease lubricant. 



50 



