ries, use a hard line telephone attached to a 

 radio-equipped surface buoy, thereby obtain- 

 ing both a tracking and communications ca- 

 pability on a single system. 



A most fundamental means of communica- 

 tion is found in BE1\ FRANKLIN's SAS. This 

 consists of a small cylindrical chamber in the 

 top of the pressure hull into which hollow 

 glass balls are placed and "locked-out" to the 

 surface. The diameter of the hatch is 150 

 mm. Messages were sent in the glass spheres 

 to the support ship during the Gulf Stream 

 Drift mission. While this system is obviously 

 limited and irreversible, it does constitute a 

 means of one-way communications when all 

 else fails. 



Marker Buoys 



Undoubtedly, the surest method of locat- 

 ing a submersible is by the attachment of a 

 buoy. Several submersibles have the capabil- 

 ity of releasing a buoy which is held to the 

 vehicle by a thin line. Depending on the 

 submersible, the buoy and line may serve 

 several purposes. At the least, it provides a 

 visual target which potential rescuers may 

 follow to the vehicle; at most, a hook and 

 stronger salvage line can be slid down the 

 marker line to automatically attach to a lift 

 padeye on the vehicle. SEA OTTER incorpo- 

 rates this latter feature which is shown in 

 Figure 14.17. 



Acoustics 



The function of acoustic pingers and trans- 

 ponders was discussed earlier to the extent 

 that they are used to maintain a given range 

 and bearing between support craft and sub- 

 mersible. In an emergency situation these 

 devices may be used by a rescuer to locate 

 and home in on the submersible, using either 

 another submersible or an unmanned rescue 

 device. Several factors control usefulness of 

 pingers. At the very least the rescuer must 

 be able to receive the frequency of the trans- 

 mitting device. Further, the majority of pin- 

 gers and transponders are self-powered and, 

 therefore, limited in duration. The variety 

 and capabilities of pingers and transponders 

 are so numerous that to list all could be 

 confusing. For example, some 40 companies 

 in the U.S. manufacture pingers, and 46 



manufacture transponders. To further ex- 

 pand the list, a variety of pingers and trans- 

 ponders is available from each manufac- 

 turer. A current list of pingers from Helle 

 Engineering shows 23 models with ranges of 

 0.5 to 5 miles, duration of 2 days to 5 years, 

 frequencies of 8 to 50 kHz and depth ranges 

 of 600 to 10,000 feet. Many competitors offer 

 an equally wide variety. 



It should be mentioned that other sources 

 of acoustic transmissions are available on 

 submersibles, in addition to pingers and 

 transponders. The majority of underwater 

 telephones listed in Table 14.7 are capable of 

 continuous wave (CW), as well as voice, 

 transmission. In the CW mode a telephone 

 can also serve as a homing beacon. 



Likewise, upward-looking echo sounders, 

 side scan sonars, obstacle avoidance sonars 

 and other acoustic devices found on some 

 submersibles offer some degree of homing 

 capability. At the lower end of the spectrum 

 is sound produced by the occupants tapping 

 on the hull which may serve as a crude 

 source of communications and a very limited 

 homing beacon. 



In order for any system to be an effective 

 communications or homing device for res- 

 cuers or for assistance from sources other 

 than its support craft, the support craft must 

 carry a ship-to-shore radio and some form of 

 surface positioning system. When a submers- 

 ible is working out of sight of land the sup- 

 port craft may attain its own position via a 

 sextant or an electronic aid to navigation 

 which may be accurate to within several 

 miles to a few hundred yards. In any event, 

 because of the considerable difficulty in re- 

 turning to the same position and reestablish- 

 ing acoustic contact with the submersible, it 

 would be unwise for the support craft to 

 leave the scene to seek assistance (or for any 

 other reason). On the other hand, one might 

 expect the support craft to immediately 

 plant a buoy to aid in maintaining and/or 

 regaining the submersible's position in the 

 event of a pinger or other critical electronic 

 component failure. Planting a marker buoy 

 may be easily done if the submersible is in 

 shallow (200-ft) water, but in the case of the 

 deeper vehicles, the thousand or more feet of 

 line required is not generally a part of the 

 support craft's on-board inventory. 



680 



