Stewart and Poudrier 



used in lowering a package to 20,000 feet is considerable, it may 

 prove necessary to jettison the cable and recover only the instrument. 

 This can be done by use of an explosive cutting device. Other methods 

 of actuating the system can also be assembled, using equipment now 

 commerically available. An acoustic command unit of the type now used 

 on anchor release devices could be modified slightly to open a fuel 

 valve on a hydrazine recovery system. This would also permit use of 

 the hydrazine system for recovery of instrument which may be 

 deliberately placed on the ocean floor for a longer period, or to 

 provide additional life for buoyed instrument systems where the 

 buoyancy of the supporting submerged buoy is marginal or has been 

 impaired accidentally. 



Light Metal hydrides offer another chemical source for gas generation. 

 The basic chemicals are considerably more expensive than hydrazine, and 

 unless properly compounded and handled can be more hazardous. Advantages 

 are that the gas evolved is pure hydrogen, giving maximum buoyancy 

 per pound of chemical, and that the reaction is easily started by 

 exposure to sea water. 



A wide variety of instruments are towed by survey and research ships 

 at depths ranging from just below the surface to several hundred feet. 

 Tlie transducer housing described previously is one of this type, and 

 in this case it was practical to install a complete recovery system 

 within the housing. Since in many cases this would not be possible, 

 it is desirable to have available a series of modular systems which 

 can be used in conjunction with equipment such as sparker sleds, 

 gravimeters, etc. The second recovery system now being tested aboard 

 USNS GILLISS consists of a towed body containing the recovery system 

 only. This will be neutrally buoyant and will be towed astern of the 

 instrument it is intended to protect against loss. As shown in the 

 slide, the housing consists of two fiber-glass dishes containing the 

 flotation bag and containers of hydride. Again an overpressure 

 mechanism will actuate the system, permitting the dishes to separate 

 and extend the bag. The same motion will operate a lid-flipper to 

 open the hydride containers to sea water, and hydrogen will be 

 evolved to inflate the bag. The shape of the housing is designed to 

 offer low drag while in the normal towing mode. When the system is 

 actuated, the bridle separates to permit the dishes to spread apart. 

 Weight of the instrument package is then suspended below the container, 

 and the upper disli will act as a drogue to slow the descent of the 

 entire assembly while the bag is filling. 



Again it has been necessary to devise an actuating system, in this case 

 to release the bridle. The same rupture disc and sea water battery 

 used in the air operated system are employed, with the squib used to 

 ignite an explosive wire. When this wire is burned, the cable 

 connector is released. The slide shows a cut-away of the device, and 

 a quick demonstration of its operation will be shown. 



300 



