oxygen which exceeds 100 percent (±10%) of 

 the floodable volume of the pressure hull, 

 then it must be stored in an independent 

 subsystem. Locating the oxygen flask out- 

 board of the pressure hull apparently satis- 

 fies this ABS requirement. Approximately 

 one-third of all submersibles (for which such 

 information is available) stores oxygen ex- 

 ternally; correspondingly, all of these vehi- 

 cles have operating depths of 2,000 feet or 

 less. A number of Perry-built vehicles in- 

 clude this feature (Fig. 9.1). 



Arguments against internal storage de- 

 crease with operating depth, for at some 



point the oxygen flask must be made resist- 

 ant to external pressure (as its internal pres- 

 sure decreases with oxygen consumption), 

 and the necessary strengthening adds 

 weight. Other advantages of internal storage 

 include the reduction of thru-hull penetra- 

 tions and the security of having the entire 

 system inside where it runs no risk of dam- 

 age from external agents. In the final analy- 

 sis, however, there appears to be no recom- 

 mended location (inside vs. outside), for not 

 MTS, ABS or the Navy addresses the subject 

 as such. There is, however, a requirement in 

 the 1974 ABS manual that the flask be lo- 



Fig 9 1 Perry Submarines DEEP DIVER carries tour oxygen flasks topside between the diver lock-out chamber and helium sphere (NAVOCEANO) 



413 



