7. Determine the size and weight of the helium reservoirs. 



8. Estimate the amount of syntactic foam required to give the 

 vehicle neutral buoyancy. 



Detailed calculations are included in Appendix C. 



The prototype submersible will have dimensions of approximately 

 40 feet in length, 16 to 20 feet in width, and a height of 6 to 8 feet. Dry 

 weight will probably be in excess of 91 ,000 pounds. The submersible is 

 dependent on a surface support vessel which will be equipped with means 

 to launch and retrieve the submersible, track it during a mission, and have 

 the on-board capability of charging the submersible's batteries and filling the 

 high-pressure helium reservoirs. 



With the exception of the helium reservoirs and associated valves and 

 fittings, this concept represents application of current thinking. The detailed 

 design of the reservoirs, however, will require special thought and considera- 

 tion. Each of the 6-foot diameter spheres (five will be needed) will be welded 

 from 2-inch thick plates of HY-130 steel. Pressurized at an internal pressure 

 of 7,650 psi, the helium tanks will have a safety factor against rupture of 

 about 2.0. This is a fairly small safety factor for high internal pressure vessels 

 which undergo repeated cyclic loadings. The helium must be allowed to 

 expand in the ballast tanks at a rate slow enough to prevent freezing of valves 

 and water ballast. Further study will be required to estimate the magnitude 

 of this problem. 



Load attachment will be kept as simple as possible. Loads, whether 

 power sources, equipment modules, or concrete foundation slabs, will be 

 equipped with lifting eyes positioned above the mass centroid of the load. 

 A hook, suspended beneath the submersible's centroid, will be used to engage 

 the load lifting eye. Lifting arrays employing slings or multiple lifting points 

 should be avoided due to the potential hazard of submersible entanglement. 



The cost of the prototype heavy-lift submersible is estimated at 

 $1,500,000 exclusive of the high-pressure helium deballasting system. Cost 

 of the latter is more difficult to estimate but a conservative figure would 

 probably be on the order of $250,000. Daily operating costs will probably 

 be several times the cost of existing deep-diving submersibles. Gray reports 

 that the operating cost of three such submersibles are as follows:^^ 



WestinghouseDS4000 $3,800/day 



General Dynamics Sfar /// $4,600/day 



Reynolds >4/ty/77//7atyf $5,400/day 



These cost figures include the operating cost of the surface support vessel. 



77 



