probably concrete, which would compensate for the positive buoyancy of 

 the foam or petroleum. Once on the bottom, the vehicle would search for 

 the load, attach the lift gear to the load, drop the ballast weight (ballast 

 weight and load weight are assumed equal), transport the load to the site 

 where the vehicle would find another ballast weight placed there earlier by 

 the lifting/lowering system, retrieve the new ballast weight, release the load, 

 and then return either to the surface or search for another load. This load 

 transport system has several serious limitations, perhaps the greatest being 

 the possibility of rapid and hazardous ascent in the event that either the 

 ballast weight or the load were detached prematurely. 



The second concept differs from the preceeding one in that positive 

 ballast is provided by high-strength steel, external pressure vessels. These 

 tanks could be HY-130 or HY-150 ring-stiffened cylinders with hemispherical 

 end caps. The air-filled cylinders, sealed at the surface, would provide a net 

 buoyancy equal to the submerged weight of the load. The vehicle would 

 submerge with the aid of an expendable concrete ballast weight, pick up the 

 load, jettison the ballast weight, and transport the load to the new bottom 

 site. After carefully positioning the load in the proper attitude and alignment, 

 the submersible would flood its ballast tanks until the submerged weight of 

 the vehicle (excluding the weight of the load) was nearly neutral. With 

 neutral buoyancy achieved, the submersible would detach the load, drop a 

 small amount of fixed ballast such as lead shot, pig iron, or concrete, and 

 return to the surface. This submersible differs in one important detail from 

 the first system; it has the ability to control the buoyancy of its main lift 

 tanks, and thus, is not dependent on finding and securing a second concrete 

 ballast weight. 



Both of the preceding heavy-lift submersible systems are dependent 

 on somewhat unwieldy lift subsystems: in one case, fixed buoyancy provided 

 by syntactic foam or other buoyant solids and liquids and in the other case, 

 high-strength steel, external pressure chambers. If instead, a submersible 

 carried a gas generator or a containment reservoir of high-pressure gas, 

 buoyant lift could be created by displacing water from tanks with low-density 

 gases. Whether filled with water or gas, the main ballast tanks would at all 

 times be maintained at an internal pressure nearly equal to the surrounding 

 hydrostatic pressure. Thus, the ballast tanks could be relatively inexpensive, 

 thin-walled chambers having none of the fabrication and operational problems 

 encountered with pressure vessels. Two approaches for the production of 

 deballasting gas at 6,000 foot depths were considered: (1 ) the use of hydra- 

 zine or other reactant gas generators and (2) the use of a low-density gas, 

 helium or hydrogen, for example, stored in reservoirs at high pressure. 



75 



