Life support system

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For other uses of "Life support", see Life support (disambiguation).

In human spaceflight, the life support system is a group of devices that allow a human being to survive in outer space. NASA often uses the phrase Environmental Control and Life Support System or the acronym ECLSS when describing these systems for its human spaceflight missions.[1] The life support system may supply: air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life support system are life-critical, and are designed and constructed using safety engineering techniques.

Contents

[edit] Life support functions

[edit] Human physiological & metabolic needs

A crewmember of typical size requires approximately 5 kg (total) of food, water, and oxygen per day to perform the standard activities on a space mission, and outputs a similar amount in the form of waste solids, waste liquids, and carbon dioxide.[2] The mass breakdown of these metabolic parameters is as follows: 0.84 kg of oxygen, 0.62 kg of food, and 3.52 kg of water consumed, converted through the body's physiological processes to 0.11 kg of solid wastes, 3.87 kg of liquid wastes, and 1.00 kg of carbon dioxide produced. These levels can vary due to activity level, specific to mission assignment, but will correlate to the principles of mass balance. Actual water use during space missions is typically double the specified values mainly due to non-biological use (i.e. personal cleanliness). Additionally, the volume and variety of waste products varies with mission duration to include hair, finger nails, skin flaking, and other biological wastes in missions exceeding one week in length. Other environmental considerations such as radiation, gravity, noise, vibration, and lighting also factor into human physiological response in space, though not with the more immediate effect that the metabolic parameters have.

[edit] Atmosphere

Space life support systems provide atmospheres composed primarily of oxygen, nitrogen, water, carbon dioxide, and other trace gases. The partial pressures of each component gas additively combine to the overall barometric pressure, typically 101.3 kPa (Earth standard atmospheric pressure at sea-level). However, atmospheric pressure can be significantly lower (25-26 kPa for EVAs) given a corresponding increase in the partial pressure of oxygen. Lower atmospheric pressures are advantageous for designing spacecraft with less structural mass and reduced atmospheric loss. The two primary ways of achieving this are by reducing atmospheric pressure while keeping the percent of oxygen the same (~21%) or through allowing the oxygen concentration to remain at sea-level pressure while reducing the overall barometric pressure.

[edit] Temperature control

[edit] Water

Water is consumed by crewmembers through drinking, cleaning activities, EVA thermal control, and emergency uses. It must be stored, used, and reclaimed (from waste water) efficiently since no in-situ sources currently exist for the environments reached in the course of human space exploration.

[edit] Food

[edit] Waste

[edit] Space vehicle systems

[edit] Gemini, Mercury, & Apollo

[edit] Space Shuttle

For the Space Shuttle, NASA includes in the ECLSS category systems that provide both life support for the crew and environmental control for payloads. The Shuttle Reference Manual contains ECLSS sections on: Crew Compartment Cabin Pressurization, Cabin Air Revitalization, Water Coolant Loop System, Active Thermal Control System, Supply and Waste Water, Waste Collection System, Waste Water Tank, Airlock Support, Extravehicular Mobility Units, Crew Altitude Protection System, and Radioisotope Thermoelectric Generator Cooling and Gaseous Nitrogen Purge for Payloads.[3]

[edit] Orion Crew Module

The Orion crew module life support system is being designed by Lockheed Martin in Houston, Texas.

[edit] Soyuz

The life support system on the Soyuz spacecraft is called the Kompleks Sredstv Obespecheniya Zhiznideyatelnosti (KSOZh).

 Please help improve this section by expanding it.
Further information might be found on the talk page or at requests for expansion. (June 2007)

[edit] Space station systems

[edit] Spacelab

[edit] Mir

[edit] International Space Station

In May of 1996, NASA published Technical Memorandum 108508, the International Space Station ECLSS Technical Task Agreement Summary Report.[4] It covers work done to develop and test both water recovery and air revitalization systems for the ISS. The diagram below shows the general functions of the life support system for the ISS.

International Space Station Life Support System

[edit] Water recovery systems

[edit] Air revitalization systems

Oxygen Generating Systems

The Oxygen Generating System (OGS) currently used aboard the ISS (International Space Station) is the Elektron, located in Zvezda. Destiny also contains an OGS which is not yet in use. Initial use of the Destiny OGS is planned for late Summer, 2007. During one of the spacewalks conducted by STS-117 astronauts, a hydrogen vent valve required to begin using the system was installed. Additionally, the ISS crew has sometimes used backup sources of bottled oxygen and Solid Fuel Oxygen Generation canisters.

The OGS aboard Destiny will electrolyze water the from the Water Recovery System to produce oxygen and hydrogen. The oxygen will be delivered to the cabin atmosphere and the hydrogen will be vented overboard.[5]

[edit] EVA Systems

Extra-vehicular activity (EVA) systems primarily consist of the traditional space suit, but can also include self-contained individual spacecraft.

[edit] Space suits

Both space suit models currently in use, the U.S. EMU and the Russian Orlan, include Primary Life Support Systems (PLSSs) allowing the user to work independently without an umbilical connection from a spacecraft. A space suit must provide life support, either through an umbilical connection or an independent PLSS.

[edit] References

  1. ^ Breathing Easy on the Space Station. NASA.
  2. ^ F.M. Sulzman & A.M. Genin, Space, Biology, and Medicine, vol. II: Life Support and Habitability, American Institute of Aeronautics and Astronautics, 1994.
  3. ^ HSF - The Shuttle: Environmental Control and Life Support System. NASA.
  4. ^ International Space Station ECLSS Technical Task Agreement Summary Report. NASA.
  5. ^ International Space Station Environmental Control and Life Support System. NASA.

[edit] Further reading

  • Eckart, Peter. Spaceflight Life Support and Biospherics. Torrance, CA: Microcosm Press; 1996. ISBN 1881883043.
  • Larson, Wiley J. and Pranke, Linda K., eds. Human Spaceflight: Mission Analysis and Design. New York: McGraw Hill; 1999. ISBN 007236811X.
  • Reed, Ronald D. and Coulter, Gary R. Physiology of Spaceflight - Chapter 5: 103-132.
  • Eckart, Peter and Doll, Susan. Environmental Control and Life Support System (ECLSS) - Chapter 17: 539-572.
  • Griffin, Brand N., Spampinato, Phil, and Wilde, Richard C. Extravehicular Activity Systems - Chapter 22: 707-738.

[edit] See also

Spaceflight Portal

[edit] External links