marine operations, and by the Navy Sealab experi- 
ments. 
1. Current Situation 
Life support activities may be divided into 
seven functions: 
—Atmosphere control (breathing mixture and con- 
taminant control). 
—Climate control (temperature and relative hu- 
midity). 
—Water supply (potable, wash, and machinery 
makeup). 
—Food supply (preparation, refrigeration, freezing, 
and storage). 
—Waste removal (solid and liquid waste products). 
—Habitability (human factors design considera- 
tion). 
—Personnel (crew’s psychological wellbeing). 
a. Atmosphere Control Atmosphere control, al- 
though the most difficult of life support functions, 
is not a new problem. Submarine and, more 
recently, space vehicle designers have devoted 
considerable time and effort to its solution. 
However, only recently have human beings been 
subjected to a completely closed environment for 
extended periods without frequent rotation. 
Miners, although exposed for many hours, have 
daily recuperative periods before re-entry into the 
mine, as do diesel submariners during surfacing or 
snorkeling. Polaris submariners regularly spend 60 
or more consecutive days submerged with no 
opportunity for their bodies to recuperate. 
Since relatively little is known about the 
cumulative effects of long-duration exposure, it is 
extremely important to keep the atmosphere of 
manned underwater structures as pure as possible. 
Once the desired atmosphere has been defined, 
various methods to maintain it can be analyzed. 
The simplest method is a ducted supply and 
exhaust system with filters using the earth’s 
atmosphere to provide air. This method is appli- 
cable to land-linked mining operations having 
tunnels extending under the ocean floor or to 
shallow underwater habitats. 
A second method is to bleed fresh air from 
storage tanks, to filter the habitat atmosphere, and 
to pump contaminants overboard. Considerable 
power and frequent resupply are necessary; the 
method has proved to be extremely inefficient in 
providing a uniform clean atmosphere. 
The third and most feasible method is to 
provide a sealed habitat with oxygen supplied 
either from storage or from an oxygen generator. 
Oxygen storage can be either high pressure or 
cryogenic; the advantages and disadvantages of 
each must be analyzed for a particular application. 
Oxygen generators have been improved over the 
early years of nuclear submarine operation. The 
current units provide good service but require 
assiduous care in operation and maintenance; 
improvements are necessary to enhance reliability 
and safety. Currently, a very promising oxygen 
generator module (a byproduct of fuel cell re- 
search) is under evaluation for the Navy. 
Chlorate candles and chlorate candle furnaces 
have been used on nuclear submarines. However, 
control is presently impossible, because once 
ignited the whole candle is consumed; hence, an 
automatic system appears impractical. Other meth- 
ods combining oxygen generation with carbon 
dioxide removal are in preliminary stages. Some 
appear promising but only for limited compart- 
ments and small crews. 
Filters, catalytic burners, and carbon dioxide 
scrubbers may be used to purify habitat 
atmosphere. Activated charcoal filters, electro- 
static precipitators, and mechanical means may be 
considered also. Catalytic burners (as carbon 
monoxide-hydrogen burners) perform well with 
little maintenance or adjustment. Carbon dioxide 
removal can be accomplished by liquid scrubbers 
or dry chemical plates. To date only mono- 
ethanolamine scrubbers have proved efficient and 
reliable for large volume purification. Smaller 
volumes may be cleaned by lithium hydroxide 
plates or crystals. 
The problems of sealed atmosphere control in 
submerged structures can be solved with present 
technology, but the system selected will depend 
upon the structure’s volume, crew number, mis- 
sion duration, and to some extent power source 
chosen. 
Another problem is monitoring habitat atmos- 
phere for contamination from materials and con- 
sumables. Hardware in the market for both auto- 
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