into the hull. However, in a lock-out vehicle 

 where the divers may be at cabin pressure in 

 excess of 29.4 psia, the oxygen closed-circuit 

 system is a definite hazard. For this reason 

 none of the lock-out submersibles covered 

 herein employs an oxygen closed-circuit sys- 

 tem for emergency breathing. 



The duration of an emergency breathing 

 system is difficult to pre-determine. The 

 closed-circuit systems may supply sufficient 

 oxygen for 1 to 4 man-hours of breathing. 

 The key, however, is the user and his activ- 

 ity. In an emergency the average person's 

 respiration will increase and the emergency 

 breathing gasses will expire much sooner 

 than under non-stress conditions. Other fac- 

 tors which will increase rate of gas consump- 

 tion are cold and physical exertion. The ideal 

 situation in an emergency is for the occu- 

 pants to remain calm and breathe at a slow, 

 even rate to conserve their air. Some individ- 

 uals are capable of controlling themselves 

 under times of stress; others are not. There- 

 fore, the maximum duration of emergency 

 life support is, by and large, an intelligent 

 approximation. 



Chlorate Candles: 



Though rarely used in submersibles, an- 

 other source of emergency oxygen is from 

 chlorate candles composed of sodium chlor- 

 ate (82-88%), barium peroxide (3%) and a 

 binding material. When the candles are ig- 

 nited, a chemical reaction ensues which re- 

 leases high purity oxygen at a rate depend- 

 ing mainly on the candle's cross section. The 

 oxygen produced is passed through a filter 

 which removes salt spray and cools the oxy- 

 gen. The average property of chlorate can- 

 dles (3) are: 



Oxygen produced 



per pound of candle 0.32-0.38 lb 



Specific gravity 



of candle 2.4 



Heat generated 100 Btu ft^ 



Storage life 10-15 years 



Gas purity better than 99% 



Loss of Electrical Power 



The total loss of electrical power in all 

 submersibles means loss of horizontal ma- 

 neuverability, external lighting and avoid- 

 ance sonars. In a number of submersibles it 



may also mean loss of normal life support, 

 and, perhaps, underwater communications. 

 Loss of maneuverability, lighting and avoid- 

 ance sonar or other working instruments is 

 not in itself critical if the vehicle is clear of 

 overhead obstructions. In this situation the 

 operator informs the surface support ship of 

 his plight and surfaces by non-electrical de- 

 ballasting or by using emergency power to 

 drop ballast. Where fail-safe deballasting 

 systems are incorporated, such as the bathy- 

 scaph's automatic dumping of iron shot with 

 loss of power, surfacing is automatic. The 

 situation can become critical, however, if 

 power failure occurs when the submersible is 

 under ice, in an overhanging canyon or un- 

 der a cable or bottom-mounted hardware. In 

 such situations submersibles, as far as can 

 be determined, have no other option but to 

 ascend vertically. The threat to safety is 

 obvious, and the only recourse may be to 

 wait for surface assistance. In the fail-safe 

 jettison situation there is no recourse but to 

 surface, since, without power, the vehicle 

 cannot stop ascending by using its vertical 

 thruster. As discussed earlier in this section, 

 the safety of the operation must take into 

 account such contingencies prior to its initia- 

 tion. Historically, submersibles rarely oper- 

 ated under conditions where a vertical as- 

 cent would be dangerous. Hence, loss of lat- 

 eral maneuverability, lighting and other in- 

 struments generally resulted only in an 

 aborted mission and delay in the diving 

 schedule. 



Loss of power, while not critical to most 

 life support systems, may nevertheless have 

 an adverse effect. The supply of oxygen 

 would not be affected by a power loss, since it 

 is released into the cabin by virtue of its 

 being under compression. Removal of carbon 

 dioxide, however, is dependent upon an elec- 

 trically-powered blower which circulates 

 cabin air through a scrubber. If the scrubber 

 fails, carbon dioxide builds up. The only 

 known exception to this is the BEN FRANK- 

 LIN wherein cabin air is circulated through 

 thin panels of lithium hydroxide by natural 

 convection currents. 



Upon loss of electrical power there are 

 several options open to the occupants (Table 

 14.3). One of these, automatic weight drop, 

 has been discussed. Loss of lighting within 



669 



