TABLE 14.5 DEVICES TO ASSIST UNDERWATER RESCUE 



Marker Buoy 



Underwater Telephone 



Pingers/Transponder 



External Lights 



External Gas/Air/Electrical Connections 



Salvage/Lift Padeye 



Environmental Sensors 



Obstacle Avoidance Sonar 



Of equal importance is the life support 

 endurance — in the 1-man submersible K-250 

 it is 6 hours; in the 6-man BEN FRANKLIN it 

 is 252 man-days. Obviously the time availa- 

 ble to locate, mobilize and employ rescue 

 devices is virtually nil in the former and 

 optimum in the latter. A histogram of total 

 life support endurance (normal and emer- 

 gency) is presented in Table 14.6. This infor- 

 mation was obtained mainly from manufac- 

 turers' brochures and technical articles de- 

 scribing the vehicle. Total life support is 

 given in man-hours and the normal maxi- 

 mum number of occupants is noted in paren- 

 theses. Dividing the number of occupants 

 into total man-hours makes one fact quite 

 clear: In an emergency, there is precious 

 little time to respond and act. Of the total 79 

 submersibles on which life support data are 

 available, the following are the percentages 

 of vehicles wherein life support will expire 

 between the given hour intervals: 

 6—24 hours: 36% 



24—48 hours: 44% 



48—72 hours: 15% 

 72 hours: 5% 



The later into a mission an emergency 

 occurs the less time there is, of course, to 

 assess the situation, attempt self-cures and/ 

 or to call in outside assistance. Just how 

 critical the situation can become is obvious if 

 you subtract the time necessary to mobilize, 



transport and deploy rescue teams and de- 

 vices. This subject will be dealt with in a 

 later section of this chapter. It is sufficient 

 to note that 80 percent of past and present 

 vehicles have a life support duration of no 

 more than 48 hours, a precariously short 

 time in which to effect underwater rescue. 



Depth, water temperature, visibility, cur- 

 rents, surface conditions and a variety of 

 other environmental factors govern both the 

 type of rescue attempts or devices that can 

 be used and the methods in which they may 

 be deployed. These factors, of course, cannot 

 be controlled by the submersible, but infor- 

 mation as to their presence and scope can be 

 provided by the vehicle's occupants to aid 

 the rescuer in his choice and deployment of 

 rescue devices. 



In order for any external devices to be 

 effective, the submersible must be accom- 

 panied by a surface support craft of some 

 description either to effect rescue or to call 

 in assistance. There are no hard and fast 

 rules applied to submersible diving, but few 

 submersibles, if any, dive without a surface 

 support craft in attendance. 



Telephones 



Table 14.1 shows that over 75 percent of all 

 submersibles carry an underwater tele- 

 phone. This does not mean that all have the 

 same communications capacity; some are 



676 



