WET SUITS 



279 



PER CENT ABSOLUTE AMBIENT PRESSURE 

 INCREASE /P^Po\ X ,00 ^ 



Fig. 107. Insulation thickness of open- 

 cell Laytex vs external pressure 



Table 32 



THERMAL CONDUCTIVITY k OF GASES 



[cal / (sec-cm-) (°C/cm)] 



(Approximate Values at Ordinary 



Temperatures and 1 ATM A) 



Carbon dioxide is a likely candidate from the point of view of bulk and weight since, under 

 adequate pressure, it can be stored in the liquid phase. The thermal conductivity of CO 2 is ap- 

 proximately one-tenth that of helium. Small amounts of CO2 are readily scrubbed from the at- 

 mosphere by chemical absorbents, permitting use of the gas in a life-support enclosure. (CO 2 

 was selected as the insulating gas prior to the Sealab II evaluations, and a filling manifold was 

 provided for filling two suits simultaneously. But the cramped space in the Sealab 11 diving 

 locker would not permit use of the CO 2 filling manifold. The Sealab E habitat atmosphere was 

 used rather than CO2.) 



Another interesting candidate for an insulating gas is the family of fluoromethane refrig- 

 erants (DuPont's Freons), some of which are nontoxic in small concentrations. Although these 

 gases are good insulators, they cannot be scrubbed from a closed high-pressure breathing en- 

 vironment and would accumulate as the gas diffused from the garments. The properties of the 

 Freon gases suitable for the heated-suit application are shown in Table 33. Freon-13Bl is the 

 best choice, comparing all of its properties with the other Freons. Its thermal conductivity is 

 only 64 percent that of carbon dioxide. Aside from their thermal characteristics, Freons are 



