directed downward, because when this de- 

 vice was initially used in DS-4000 the flow 

 was upward and the occupants emerged from 

 a 6- or 8-hour dive with bloodshot eyes and 

 dry nasal passages caused by the air blowing 

 into their faces when at the viewport. 



Automatic systems are not common on 

 submersibles but can be found on the more 

 sophisticated vehicles, such as DEEP 

 QUEST and DSRV. Because life support con- 

 trol is so critical, the operator is still re- 

 quired periodically to monitor cabin oxygen. 

 It only takes a little more time to check and 

 regulate a flowmeter while performing the 

 monitoring functions. If such checks are not 

 routine, then a warning system is impera- 

 tive, and, while this does add to the complex- 

 ity and cost of the vehicle, it frees the opera- 

 tor for other tasks. 



The quantity of oxygen carried varies from 

 vehicle-to-vehicle. A comparison is shown in 

 Table 9.4. The MTS recommends that the 

 oxygen capacity of a system should be stated 

 in cubic feet of oxygen at 70°F and 760 mm 

 Hg, but this procedure is frequently not fol- 

 lowed, hence, many of the values shown are 

 approximate and were calculated from the 

 barest of details. 



From an efficiency point of view, Beving 

 and Duddleston (5) point out that a typical 

 cylindrical steel tank holds approximately 15 

 pounds of usable oxygen at 2,200 psi. The 

 cylinder plus oxygen weighs about 150 

 pounds. With a usable weight ratio of 1-to-lO, 

 a considerable weight penalty is encountered 

 if many tanks have to be carried. A more 

 efficient solution, according to these authors, 

 is to carry oxygen in liquid form. In a typical 

 double-walled liquid oxygen tank, a pound of 

 oxygen can be carried for each pound of tank 

 with corresponding savings in volume. While 

 Beving and Duddleston's efficiency figures 

 for liquid vs. gaseous oxygen are impressive, 

 the cost, complexity and logistic problems 

 are unacceptable to most of today's commer- 

 cial vehicle owners. Furthermore, it is not 

 life support endurance which restricts pres- 

 ent vehicles to short dives; rather, it is elec- 

 trical endurance. 



Food and Water: 



There is no submersible now operating 



that routinely remains submerged for more 

 than 8 or 10 hours; consequently, food and 

 water are generally provided in the form of 

 sandwiches, fruit, candy and thermos jars of 

 coffee, tea or whatever. Exceptions to this 

 are BEN FRANKLIN (now inactive) and NR- 

 1. The latter, in view of its size, mission 

 endurance and nuclear electrical generating 

 plant, presumably uses freeze-dried foods or 

 prepackaged "TV" trays which are prepared 

 and heated in a kitchen. 



While such a casual approach to suste- 

 nance, at first glance, may seem alarming, it 

 has produced no ill effects. Indeed, in most 

 vehicles the support ship cook errs, if at all, 

 in favor of quantity, for more often than not 

 a portion of the lunch is returned uneaten. 

 This procedure works well as long as the dive 

 is routine. All have not been routine (see 

 Chap. 15), however, and then emergency ra- 

 tions became a consideration; in this respect 

 most are deficient. 



In case retrieval is impossible or the sub- 

 mersible is lost from its support ship, 

 emergency food and water could be a critical 

 factor in survival. A wide variety of nutriti- 

 ous foods which can serve as emergency ra- 

 tions are available at sporting goods stores 

 and have a shelf like of many months. Such 

 fare is not necessarily a gourmet's delight, 

 but survival, not comfort, is the order of busi- 

 ness. The amount of emergency food and 

 water required is difficult to ascertain, but 

 little space is required for storage of these 

 foods and a minimum of 72 hours of 

 emergency supply does not appear unreason- 

 able. Freeze-dried foods would be ideal, but in 

 the small confines of a submersible their pre- 

 paration is awkward and, without hot water, 

 they are difficult to mix. 



The recent JOHNSON SEA LINK and 

 PISCES III incidents have increased the 

 submersible community's awareness of life 

 support, and a number of vehicles have in- 

 creased their supply of oxygen and carbon 

 dioxide removal compounds to extend support 

 to 72 hours/occupant and longer. The Na- 

 tional Oceanic and Atmospheric Administra- 

 tion (NOAA) requires at least 72 

 hours/occupant before it will allow its emp- 

 loyees to dive in the vehicle. Oddly, no one has 

 addressed the possibility of decreased human 



416 



