The DSRV is equipped with a haul-down 

 system to assist it in mating in unfavorable 

 underwater currents. The system consists of 

 a winch and cable located in the DSRV skirt. 

 A grapnel hook at the end of the cable is 

 lowered and attached to the escape hatch. 

 The winch is then operated to haul the DSRV 

 down to the rescue seat. A suitable bail must 

 be provided on the escape hatch. 



It is necessary to have an air sampling and 

 pressure equalization valve operable from 

 outside of the submersible. The fitting must 

 be located within the area covered by the 

 skirt. Its purpose is to permit sampling of the 

 air within the submersible for toxicity, tem- 

 perature, and radioactivity, and to equalize 

 pressure between the DSRV and the subma- 

 rine. The DSRV is capable of operating with 

 an internal pressure of 5 atmospheres abso- 

 lute. 



2) SRC Requirements: The SRC mating 

 surface is a construction around the bottom 

 of the lower chamber consisting of a rubber 

 gasket and a steel retaining ring. The 1^/4- 

 inch-wide pure rubber gasket at the mating 

 surface provides a seal against sea pressure 

 when the SRC is mated to the submarine. 



The disabled submersible must have an 

 equivalent mating surface around its hatch 

 to be used for the rescue. The strength re- 

 quired of the rescue seat depends on the 

 depth at which the mating will be performed. 

 Since the system has a depth capability of 

 850 feet, the static load on the rescue seat 

 after dewatering and venting of the lower 

 chamber will be the hydrostatic pressure at 

 850 feet acting over the corresponding area 

 exposed to the lower pressure plus the net 

 buoyancy of the chamber and the force ex- 

 erted by the pressure and the force exerted 

 by the haul-down cable. Seat loading of 3,640 

 psi will therefore result if the mating sur- 

 faces are perfectly flat. A safety factor 

 should be utilized to allow for surface irregu- 

 larities, corrosion, and minor impact loads. 

 The strengthened area of the rescue seat 

 should have a minimum outside radius of 35 

 inches and a maximum inside radius of 23 

 inches, both as measured from the center of 

 the submersible's hatch. 



The rubber gasket at the SRC mating sur- 

 face is designed to seal rescue seat surface 

 irregularities such as scratches, nicks, and 



waviness. The gasket is capable of sealing 

 gaps up to Vs inch. The seal limitation re- 

 quires the rescue seat to be flat within Vs 

 inch. Figure 15.5 (bottom) illustrates the 

 mating of an SRC with a typical submarine 

 hatch. 



Projections and obstructions above the 

 hull of the disabled submarine in the vicinity 

 of the rescue seat present hazards to the 

 SRC mating surface and seal. Damage to 

 these systems could prevent mating. In the 

 area of the submersible's rescue hatch there 

 can be no projections above the submarine 

 hull which would impact an SRC descending 

 vertically to a submersible that is inclined 30 

 degrees from the vertical in either the fore- 

 and-aft or athwartships planes, or both. 



If the haul-down cable is not permanently 

 attached to the submersible, a strengthened 

 connection point must be available at the 

 hatch to permit hook-up of the down-haul 

 cable by external means. The maximum 

 depth at which this can be accomplished is a 

 function of AS R maximum deep diving capa- 

 bility, and is generally around 400 feet. The 

 connection point should be as nearly cen- 

 tered on the hatch as possible. The padeye or 

 bail must be able to withstand a load of 

 12,500 pounds. 



In addition to the cable connection point, 

 two other requirements are placed on the 

 submarine hatch. To permit egress from the 

 submersible the hatch must be of such size 

 to allow it to be opened, without interfer- 

 ence, into the lower chamber of the SRC with 

 the SRC mated to the submersible. SRCs 

 lower chamber minimum internal clearances 

 are shown in Figure 15.6. 



The hatch area should include tiedown at- 

 tachment points so that the SRC can be 

 firmly secured to the submersible before the 

 haul-down cable is slacked. The SRC has four 

 hold down rods with shackles on their ends 

 which will be emplaced by the rescue crew 

 before the hatch is opened. The tiedown 

 points must be padeyes or staples with open- 

 ings through which the IVs-inch-diameter 

 pins of the hold down rod shackles can be 

 passed and secured. They must be placed 

 around the submarine's hatch inside the 

 area of SRC/submarine mating (orientation 

 is not critical). The tiedown attachments 

 must be individually capable of withstanding 

 a holding down load of 10,000 pounds. 



699 



