Astronauts --- Life in Space Shuttle

The orbiter of the space shuttle must provide astronauts with an environment similar to the Earth.
It must be capable of providing the following things:
- Atmosphere control, supply and recycling
- Water
- Temperature control
- Light
- Food supply
- Waste removal
- Fire protection

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.

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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Weightlessness Spacesuit Life in Space Shuttle Life in Space Station