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Life in Space
Shuttle
Atmosphere
control, supply and recycling
In a space shuttle, the following things are needed:
- atmosphere similar to Earth
- breathed out carbon dioxide removed
- contaminating or trace gases removed
- normal humid environment
Our atmosphere is a mixture of gases (78 percent nitrogen, 21 percent
oxygen, 1 percent other gases) at a pressure of 1 atm. Liquid oxygen and
liquid nitrogen are carried on board in two systems of pressurized tanks,
which are located in the mid-fuselage (each system has two tanks for a
total of four tanks), for the purpose of providing a similar atmosphere.
The cabin pressurization system combines the gases in the correct mixture
at normal atmospheric pressure.
The atmosphere is circulated by five loops of fans. The circulated air
picks up carbon dioxide, heat and moisture:
- Chemical carbon dioxide canisters remove carbon dioxide by reacting
it with lithium hydroxide.(see The
Jobs of a Typical Spacesuit --- Remove carbon dioxide)
- Filters and charcoal canisters remove trace odors, dust and volatile
chemicals from leaks, spills and outgassing.
- A cabin heat exchanger in the lower deck cools the air and condenses
the moisture, which collects in a slurper. Water from the slurper is moved
with air to a fan separator, which uses centrifugal force to separate
water from air. The air is recirculated and the water goes to a wastewater
tank.
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Water
Apart from air, water is the most important thing. Water is made form
liquid oxygen and hydrogen in the space shuttle's fuel cells. The water
is stored in four water storage tanks, which are pressurized by nitrogen
so that water can flow to the mid-deck for use by the crew. Drinkable
water is then filtered to remove microbes and can be warmed or chilled
through various heat exchangers depending upon the use (food preparation,
consumption, personal hygiene). Excess water produced by the fuel cells
gets routed to a wastewater tank and then is dumped overboard.
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Temperature
Control
Outer space is an extremely cold environment and temperature varies drastically
in different parts of the orbiter. But the space shuttle will get rid
of excess heat because the electronic equipment generates more than enough
heat for the ship.
So the temperature control system has to carry out two main functions:
- Distribute heat where it is needed on the orbiter so that vital systems
do not freeze in the cold of space
- Get rid of the excess heat
The shuttle has two methods to handle temperature control:
- Passive methods - generally simple, handle small heat loads and require
little maintenance.
Insulating
materials, surface coatings, paints - reduce heat loss through the wall
Electrical heaters - use electrically-heated wires to heat various areas.
Active methods
- more complex, use fluid to handle large heat loads, require maintenance.
Cold plates
- metal plates that collect heat by direct contact with equipment or
conduction
Heat exchangers - collect heat from equipment using fluid. The equipment
radiates heat to a fluid which in turn passes heat on to freon. Both
fluids are pumped and recirculated to remove heat.
Pumps, lines, valves - transport the collected heat from one area to
another.
Radiators - located on the inside surfaces of the cargo bay doors that
radiate the collected heat to outer space.
Light
The orbiter has internal fluorescent floodlights that illuminate the crew
compartment. Besides, the orbiter has external floodlights to illuminate
the cargo bay. Moreover, the control panels are lighted internally for
easy viewing.
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Food
Food comes in several forms, dehydrated, low moisture, heat-stabilized,
irradiated, natural and fresh.
The orbiter has a galley-style kitchen module along the wall next to the
entry hatch, which is equipped with the following:
- Food storage compartments
- Food warmers
- A food preparation area with warm and cold water outlets
- Metal trays so the food packages and utensils do not float away
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Waste
Removal
The orbiter must be kept clean, especially in space when floating dirt
and debris could present a hazard. Wastes are made from cleaning, eating,
working and personal hygiene. For general housecleaning, various wipes
(e.g. wet, dry, fabric, detergent and disinfectant), detergents, and wet/dry
vacuum cleaners are used to clean surfaces, filters and the astronauts.
Trash is consisted of wet trash bags and dry trash bags. All trash bags
are placed in the lower deck to be returned to Earth for disposal. Solid
waste from the toilet is compacted, dried and stored in bags where it
is returned to Earth for disposal. Liquid waste from the toilet goes to
the wastewater tank where it is dumped overboard.
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Fire
Protection
Fire is one of the most dangerous hazards in space.
The orbiter has a Fire Detection and Suppression Subsystem that consists
of the following:
- Area smoke detectors on each deck
- Smoke detectors in each rack of electrical equipment
- Alarms and warning lights in each module
- Non-toxic portable fire extinguishers (carbon dioxide-based)
- Personal breathing apparatus - mask and oxygen bottle for each crew
member
After a fire is extinguished, the atmosphere control system will filter
the air to remove particulates and toxic substances.
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NASA
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