A mission profile for this type of veliicle would be as follows: 

 (1 ) The vehicle, consisting of personnel sphere, propulsion system, lift tanks, 

 and high-pressure gas reservoir (or gas generator systems), is launched from 

 the support vessel; (2) the vehicle descends due to its slightly net negative 

 buoyancy; (3) the lift tanks are open to the surrounding water at the sea 

 floor, the submersible jettisons a small ballast weight and achieves near 

 neutral buoyancy; (4) the submersible searches for, locates, and secures the 

 load; (5) gas, stored at high pressure in spherical reservoirs, or produced by a 

 gas generator, is allowed to flow into the lift tanks, displacing water and 

 creating the force necessary to lift the load; and (6) the vehicle transports 

 the load to the construction site. When the operators are certain that the 

 load is aligned properly, vents are opened on the top of the lift tanks allowing 

 gas to escape. The vehicle detaches the load, repeats its mission if there is 

 sufficient gas left in the storage reservoirs, or returns to the surface by 

 jettisoning additional lead shot or pig iron ballast. 



Three conceptual designs for a heavy-lift submersible were studied. 

 Two concepts employ the gas purging principle just described, while the 

 other system relies on buoyant pressure chambers for lift. 



Conceptual Design for a Helium Deballasting Vehicle 



In this concept, helium, stored under high pressure, is used for 

 deballasting water from the lift tanks. It was assumed that all candidate 

 submersibles would be capable of at least a single 20-ton lift at 6,000 feet. 

 Mission duration and maximum cruising speed were specified at 10 hours 

 and 5.0 ft/sec, respectively. The conceptual design proceeded according to 

 the following steps: 



1. Estimate the vehicle drag force. 



2. Estimate the total power requirement. 



3. Estimate the weight and volume of the power source. 



4. Determine the size and weight of the personnel sphere. 



5. Design the two cylindrical ballast tanks. 



6. Estimate the quantity of helium required. 



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