24 



MAJOR PROGRAM AREAS 



In general, for deep-excursion diving to 300 ft the Mk-VI was considered outstanding. All 

 aquanauts agreed that the Mk-VI was superior to the open-circuit scuba. The men liked the 

 Arawak, but preferred free diving with the Mk-VI. 



With the Mk-VI, using 85 percent He, 15 percent Oj, gas-supply duration was, in many 

 cases, lower than the expected 70 minutes at 205 ft. 



ATMOSPHERE CONTAMINANTS 



Prior to Sealab II it was expected that some contaminants would be present in the atmo- 

 sphere. It was thought that the major problems would be presented by hydrocarbons, the ma- 

 jority of which would be produced by cooking. To combat this possibility, any type of frying 

 was prohibited, and a 50-pound charcoal filter was installed in the Sealab air-conditioning sys- 

 tem to remove hydrocarbons. Although there was some hydrocarbon buildup, the charcoal 

 proved to be effective and hydrocarbons were no problem. 



During the latter part of the operation, however, the aquanauts frequently complained of 

 headaches (Chapter 48). The presence of carbon monoxide in the atmosphere was suspected 

 as the possible cause, and tests were carried out for its detection. Values of approximately 

 20 ppm CO were reported. 



In an attempt to remove the CO from the atmosphere, four of the lithium hydroxide canis- 

 ters in the CO, removal system were partially filled with Hopcalite, a catalyst used aboard 

 nuclear submarines for the oxidation of CO. 



Later it was surprising to find that the CO concentration in Sealab had been decreasing 

 for several days prior to placing Hopcalite in the system. Also, there was no noticeable 



Fig. 19. Aquanaut Tolbert uses a special plant nutrient 

 for plants grown in Sealab II 



