Conceptual Design for a Hydrazine Deballasting Vehicle 



This design differs from the preceding one in that the deballasting 

 gas is provided by a hydrazine generator. The design is based largely on the 

 results of a study conducted by the Naval Ordnance Test Station (NOTS) for 

 an emergency deballasting system using liquid gas generators^" The NOTS 

 study requirements were for a system capable of displacing seawater at a rate 

 of 100 lb/sec. Total volume to be displaced was 210 ft^ (equivalent to a lift 

 of about 8 tons) at an ambient pressure of 3,550 psi (8,000 ft). Correcting 

 the NOTS data for a hydrazine system using 5% ammonia, for an operating 

 depth of 6,000 feet, it was found that: 



1 . 690 ft^ of water must be displaced for each 20-ton lift. 



2. At a fuel density of 61 .9 lb/ft^ 5,230 lb of hydrazine fuel are 

 required. 



3. At a deballasting rate of 100 lb/sec (7 minutes total time 

 required for a 20-ton lift) a 12-horsepower pump will be needed. 



The choice of hydrazine gas generation over stored helium for 

 variable ballast control has several operational advantages. First, the dry 

 weight of the hydrazine generator including fuel, pump, and catalyst bed is 

 likely to be lower in weight than the helium reservoirs, thus simplifying 

 vehicle handling at the surface. A serious problem with the stored helium 

 system is the hazard presented by the high-pressure reservoirs which are 

 subject to impact damage during launching and through fatigue failure due 

 to repeated. cyclic loading of the tanks. 



On the debit side, however, hydrazine gas generators produce 

 dangerous gaseous end products: hydrogen and ammonia. Although the 

 mission profile calls for "dumping" deballasting gas at the sea floor, an 

 alternate mission where the lift vehicle brings loads to the surface, would 

 require retention of the lift gases (allowing, of course, for venting of excess 

 gas due to expansion). Hydrogen in contact with atmospheric oxygen is a 

 hazardous mixture. The hydrazine generator is a developmental item. Its 

 feasibility will depend on several years of research and development effort. 

 Additional information on the hydrazine gas generator system is included 

 in Appendix C. 



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