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Environmental Controls

Environmental Controls

When astronauts travel to space, they need to carry along basic life support elements from Earth, such as the ability to produce food, purify their water, regenerate oxygen, and remove harmful microbes and elements from the air. The environmental control systems (in addition to other life-support systems) on the space shuttle and the International Space Station perform these functions, which keep the passengers and crew onboard alive.

Space Shuttle Climate

Temperature, which is controlled by an air revitalization system (ARS), is vital for the operation of a space shuttle, but heating and cooling systems need to be delicately monitored because some portions of the shuttle need cool air to operate, whereas others need warm air. The ARS maintains a relative humidity level of between 30 percent and 75 percent, in addition to keeping the carbon dioxide and carbon monoxide at safe levels. The ARS also regulates temperature, ventilation, and pressure in the crew compartment, in addition to providing cool air to the crew compartment and various flight-deck and mid-deck electronic mechanisms.

Environmental Controls Onboard the International Space Station

Technological advances in the field of environmental controls are a significant part of the International Space Station (ISS). These advances were designed by the National Aeronautics and Space Administration's Marshall Space Flight Center in Huntsville, Alabama, and are collectively called the Environmental Control and Life Support Systems (ECLSS). The ECLSS consists of an ARS, waste collection systems, and water purification systems. Innovations will enable the space crew to not only survive but also to live and work on the ISS for months and maybe years.

Water recycling and oxygen generation are two of the most important aspects of the ECLSS, because water and oxygen are the two basic necessities for life. One of the initial aims of the ECLSS is to recycle wastewater (including urine) to produce purified water for drinking. This recycled water will also be used to produce oxygen for the flight crew. The systems also need to remove dangerous gases from the cabin atmosphere. These gases may be generated only in trace amounts, but they can still be dangerous. In addition, gases such as nitrogen, oxygen, carbon dioxide, methane, and hydrogen must be kept at specific pressures to ensure the safety of the crew and shuttle. Because ventilation and air distribution are also important, the environmental control systems ensure that all air circulates properly through the ISS modules.

see also Closed Ecosystems (volume 3); Life Support (volume 3).

Julie L. McDowell


National Research Council. Committee on Advanced Technology for Human Support in Space. Advanced Technology for Human Support in Space. Washington, DC: National Academy Press, 1997.

Internet Resources

Environmental Control and Life Support System. National Aeronautics and Space Administration. <>; <>.

International Space Station Life Support Systems. NASA Marshall Space Flight Center.<>.

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