lower values (40 ml) can be obtained. 

 l\o evidence of degradation of Primol 

 207 dielectric fluid as a consequence 

 of discharging the battery at pressures 

 up to 1000 psi can be noted." 



In a companion paper R. S. Evans (16) 

 discussed the whole range of pressure com- 

 pensation considerations based on analyses 

 of the behavior of lead-acid batteries in ASH- 

 ERAH, STAR II and STAR III. Evans' report 

 is succinct and in very few words he presents 

 a wealth of experience the submersible de- 

 signer would do well to review. Several as- 

 pects of batteries and pressure compensation 

 systems, not dealt with elsewhere in this 

 section, are summarized below and are taken 

 directly from Evans. 



Vehicle Dynamics: 



List, trim and attack angles and angular 

 rates affect such parameters as acid and oil 

 movement, structural fatigue and distortion. 

 Relative to a surface craft, a surfaced sub- 

 mersible is more vulnerable to sea forces 

 which produce bending and impact loads in 

 components of the pressure compensation 

 system and battery containers. 



In a rapid emergency ascent (300 to 600 

 fpm) the gasses entrained or in solution 

 might rupture the system or accumulate to a 

 potentially explosive volume. Introduction of 

 sufficient seawater via a rupture invites cer- 

 tain explosion or rapid combustion of oil and 

 gas. 



A series of relatively shallow dives and 

 quick ascents will cause compensating oil to 

 push out of the vents in front of the expand- 

 ing gas which is produced continuously. If 

 the bladder design cannot accommodate such 

 losses, insufficient compensation volume 

 may result on an ensuing deep dive with 

 possible leakage into or destruction of the 

 batteries. 



Pressure; 



Interior system pressure should be kept 

 slightly positive with respect to ambient. In 

 this vein Evans offers the following precau- 

 tions in selection of materials for sea pres- 

 sure service: Battery lead deforms plasti- 

 cally; bulk moduli of adjoining materials 

 should be as nearly equal as possible for in- 

 cell connection and wedging. 



Biological: 



Evans relates the following experience 

 with respect to biological considerations: 

 ''STAR III was so busy in 1966-67 

 that over one year passed before the 

 battery box interiors were inspected. 

 When they were finally opened, a film 

 of biological material was discovered 

 deposited across the cell tops. The 

 organism was cultured and tentatively 

 identified as Pullularia pullulens, a 

 black, yeast^like mold. The system had 

 been anaerobic for the period, yet this 

 organism apparently thrived and de- 

 clined several times in this supposedly 

 hostile environment. If the ecology 

 were not controlled by additive inhibit 

 tors or occasional flushing with anti^ 

 septics, it is conceivable that orga- 

 nisms could flower under the proper 

 conditions and c€iuse short circuits by 

 entrapping water and/or acid, or 

 could clog lines and valves with their 

 detritus. Such a case was reported by 

 TRIESTE which had an open sea/oil 

 interface compensator at the time. Of 

 course, any additive or purgative 

 would first have to be proved mate- 

 rials compatible.^^ 



Utilizing this and other information 

 gained over several years' experience with 

 the STAR class vehicles, Evans and co- 

 worker B. B. Miron proceeded to draw up the 

 design specifications for pressure compensa- 

 tion of the SEA CLIFF and TURTLE battery 

 pods (19). 



The best compensating fluid for battery 

 systems has been particularly difficult to 

 define. According to Work (11), "The ideal 

 compensating fluid is non-reactive, non-com- 

 pressible, and probably non-existent." In an 

 attempt to solve this dilemma, the Naval 

 Ship Research and Development Center 

 (NSRDC) performed an assessment of appli- 

 cable experience with such fluids and tests of 

 their own to issue a guide (20) providing 

 critical properties, evaluation methods and 

 other pertinent fluid and lubricant informa- 

 tion to the workers in deep submergence. 



NSRDC not only dealt with fluids for com- 

 pensation and shielding from the seawater 

 environments, but also looked at fluids for 



330 



