Stewart and Poudrier 



for use with towed instruments at relatively shallow depths. 

 Hydrazine and Hydrazine base fuel mixtures decompose in a catalyst in 

 a gas generator to produce an exhaust gas consisting of hydrogen, 

 nitrogen, and ammonia. These fuels are classed as corrosive liquids, 

 with toxic vapors, and safety precautions very similar to those for 

 handling aviation gas must be observed. Gas temperature, ranging from 

 200 to 2000°F, can be controlled by varying the fuel mixture and the 

 length of the catalyst bed. Two types of catalyst pellets are used: 

 spontaneous and non-spontaneous. Both are composed of alumina, 

 but with different impregnated active metals. Shell 405 catalyst, 

 developed under NASA contract, is spontaneous, but has the disadvantage 

 of high cost. The non-spontaneous catalyst (nA-3) is low in cost but 

 required an electric cartridge heater or a hypergolic reaction to 

 start the decomposition, after which the reaction is self-sustaining. 

 Our applications use a layered catalytic bed, using the 405 to initiate 

 the reaction and the less expensive HA3 to sustain and complete it. 

 Both types are true catalysts; that is they are not altered in the 

 decomposition process and are indefinitely reusable. 



The key to successful use of hydrazine generators for deep recovery has 

 been the development of a suitable method of transfer of the fuel from 

 its container to the catalytic chamber. In circumstances where system 

 weight and size have not been critical this transfer has been made by 

 use of compressed nitrogen or hydraulic pistons. Neither method is 

 practical at great depths, since a pressure vessel to contain the 

 fuel and compressed nitrogen or pumping system would add too much 

 weight to the total instrument package. This has been overcome by 

 storing the fuel in a rubber container, so that it is always exposed 

 to ambient pressure. The small pressure differential needed to 

 cause the fuel to flow from the storage container through the catalytic 

 chamber is achieved through use of polymeric springs arranged to keep 

 the ends of the fuel container under tension. Thus the entire system 

 is very nearly neutrally buoyant in sea water, with only the small 

 catalytic chamber and piping being required to withstand the ambient 

 pressure. Feasibility of this approach was demonstrated in tests 

 conducted in the Tongue of the Oceans in December, 1966, using a 

 system put together from available components with a mechanical spring. 

 TTie tests now being conducted use the arrangement shown on slide and 

 will approximate an actual recovery from greater depth than previously 

 accomplished. 



It now appears that it will be possible to equip our deep instrumenta- 

 tion packages with a system which will bring them back to the surface 

 in the event of cable failure. We will also need an actuating system 

 to tell the recovery system to get to work and start generating its 

 buoyant gas. At the moment a timer is used, and probably for most 

 applications this will be all that is necessary. IVhen an instrument 

 is lowered over the side the oceanographers know within reasonable 

 limits how long it should take to accomplish a certain operation. A 

 timer can be set to start the recovery system if the package has not 

 been retrieved normally within that time. Since the weight of cable 



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