100 feet - far more than needed to raise the minitat. Each compartment of 

 the pontoons is also fitted with a pressure relief valve pre-set at 50 psi. 



FIGURE 3.— CONTROL CONSOLE. 



Forty 240 SCF (2200 psi) compressed gas bottles are stored xmder the deck 

 with manifolding to blow the pontoons dry for ascent or to provide compressed 

 gas for scuba charging or emergency breathing. Each pontoon displaces about 

 630 cubic feet of water, exerting about 40,000 pounds of buoyancy when sub- 

 merged. Ballast trays having a capacity of 47,000 pounds of cast iron ingots 

 (100 to 500 lb. size) are built into the deck. Deck supports are 12 inch wide 

 flange steel beams and the deck is galvanized steel mesh. The deck extends 

 over the pontoons, and fenders are provided. Towing kingposts are provided 

 on each corner of the barge. 



ENVIRONMENTAL CONTROL SYSTEM 



The minitat environmental control system (ECS) controls the composition, 

 pressure, temperature, and humidity of the minitat breathing gas. It consists 

 of a thermal control subsystem, a CO2 removal subsystem, a breathing gas 

 supply subsystem, and a breathing gas monitoring subsystem. 



The thermal control subsystem provides dehumidif ication, heating and cooling. 

 A refrigeration unit mounted outside the pressure vessel provides both heat- 

 ing and cooling. The evaporator and condenser are placed in hot and cold 

 reservoirs in two separate water/ethylene glycol heat exchange loops. The 

 water /glycol mixture is pumped to hot and cold heat exchangers in the vessel. 

 The breathing gas is circulated past the cold heat exchanger for dehumidif ica- 

 tion and through the hot heat exchanger as necessary for comfort. The thermal 

 control subsystem is designed to maintain the atmosphere at temperatures be- 

 tween 70° and 85° F and the relative humidity between 45% and 65%. Figure 4 

 is a schematic diagram of the thermal control subsystem. 



III-4 



