the cabin is counteracted with flashlights. 

 The remaining two options are discussed be- 

 low. 



Emergency Batteries: 



Some 25 percent of all submersibles carry 

 an emergency source of power within the 

 pressure hull. The source of this power may 

 be from nickel-cadmium, silver-zinc, or non- 

 gassing lead-acid batteries. In the event of a 

 power failure the emergency batteries are 

 used to jettison equipment or weights and to 

 operate the underwater telephone, surface 

 radio or surface flashing light, depending on 

 the submersible. 



Non-Electrical Ascent: 



A number of vehicles have the capability 

 to drop weights or blow water ballast inde- 

 pendently of electrical power. In the water 

 ballast blow the system is operated simply by 

 introducing high pressure air, which is con- 

 trolled by a manual valve within the pres- 

 sure hull, into the external ballast tanks 

 and, consequently, force the water out 

 through the open orifice on the bottom of the 

 tanks. As the vehicle surfaces, the air ex- 

 pands and continues to vent through the 

 bottom orifice, thus maintaining pressure in- 

 side the tank equal to ambient and prevent- 

 ing the re-entry of water. In the weight drop 

 situation a solid shaft through the pressure 

 hull is manually rotated to actuate a cam- 

 like release. Both systems are common in the 

 shallow (less than 1,000-ft) submersibles. 



EMERGENCY SYSTEMS 

 (SURFACED) 



In spite of the various tracking systems 

 available, not all submersibles use them, and 

 it is common to spend some time searching 

 for a vehicle after it has surfaced. In a flat, 

 calm sea visual sighting is relatively easy, 

 but swell or waves only a few feet high can 

 make the low silhouetted submersible a diffi- 

 cult target to spot. Most difficult to locate 

 are those vehicles painted white and sur- 

 faced in a white-capped sea where they blend 

 unobtrusively into the background. A fur- 

 ther complication is added when the search 

 is conducted at night, although it is some- 

 times easier to locate the vehicle by its lights 



at night than in the daytime. Location by 

 radar from the support ship is seldom feasi- 

 ble because the small target offered by the 

 submersible is lost in the sea return. More 

 than any other hazard, separation or lost 

 contact between submersible and support 

 craft is the most likely to occur. A small 

 submersible adrift on the open ocean offers 

 little in the way of comfort or sustained 

 survival to its occupants. To avoid this situa- 

 tion a number of devices are carried on and 

 within the submersible. 



If contact has been lost, an immediate 

 concern is the life support endurance of the 

 vehicle. Most submersibles have a sail sur- 

 rounding their hatch which permits it to be 

 opened in moderate sea without taking 

 water aboard. Some vehicles are constructed 

 such that the hatch is integral with the 

 pressure hull and extends a few feet above 

 the surface to allow opening. A small number 

 incorporate neither of these characteristics 

 and must rely on inflatable trunks which 

 surround the hatch or on other means. Such 

 designs are discussed below and the equip- 

 ment and procedures employed to assist in 

 emergency surface situations are listed in 

 Table 14.4. 



Separation from Support Craft 



The following devices are carried aboard 

 submersibles to establish surface contact 

 and bring together the vehicle and its sup- 

 port craft. 



Radio: 



The type and characteristics of radios 

 aboard submersibles vary widely. Two-way 

 citizen band radio transceivers are common 

 where the submersible has sufficient free- 

 board to permit its use. Range of communica- 

 tions with the surface ship is limited to line- 

 of-sight (5 to 10 miles). Hand-held radios are 

 sometimes used, but to use these the hatch 

 must be opened to extend the antennae, 

 which is not always acceptable in a low free- 

 board submersible. 



Radios serve two major post-dive func- 

 tions: 1) By virtue of radio communications, 

 they verify that the vehicle has surfaced; 

 and 2) they establish that the surface sup- 

 port craft has or has not visually located the 

 surfaced submersible. If the latter is the 



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