A Spacesuit is a garment worn to keep a human alive in the harsh environment of outer space, vacuum and temperature extremes. Essentially it is a thick, heated suit that provides oxygen and presses tightly against the skin to stabilize pressure.
They are a primary part in Gravity.
Spacesuits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, and are necessary for extra-vehicular activity (EVA), work done outside spacecraft. Space suits have been worn for such work in Earth orbit, on the surface of the Moon, and en route back to Earth from the Moon. Modern space suits augment the basic pressure garment with a complex system of equipment and environmental systems designed to keep the wearer comfortable, and to minimize the effort required to bend the limbs, resisting a soft pressure garment's natural tendency to stiffen against the vacuum. A self-contained oxygen supply and environmental control system is frequently employed to allow complete freedom of movement, independent of the spacecraft.
Some of these requirements also apply to pressure suits worn for other specialized tasks, such as high-altitude reconnaissance flight. Above Armstrong's line (around 19,000 m (62,000 ft)), the atmosphere is so thin that pressurized suits are needed. The first full-pressure suits for use at extreme altitudes were designed by individual inventors as early as the 1930s. The first space suit worn by a human in space was the Soviet SK-1 suit worn by Yuri Gagarin in 1961.
- A space suit must perform several functions to allow its occupant to work safely and comfortably, inside or outside of a spacecraft. It must provide:
- A stable internal pressure. This can be less than earth's atmosphere, as there is usually no need for the space suit to carry nitrogen (which comprises about 78% of earth's atmosphere and is not used by the body). Lower pressure allows for greater mobility, but requires the suit occupant to breathe pure oxygen for a time before going into this lower pressure, to avoid decompression sickness.
- Mobility. Movement is typically opposed by the pressure of the suit; mobility is achieved by careful joint design. See the Theories of space suit design section.
- Supply of breathable oxygen and elimination of carbon dioxide; these gases are exchanged with the spacecraft or a Portable Life Support System (PLSS)
- Temperature regulation. Unlike on Earth, where heat can be transferred by convection to the atmosphere, in space, heat can be lost only by thermal radiation or by conduction to objects in physical contact with the exterior of the suit. Since the temperature on the outside of the suit varies greatly between sunlight and shadow, the suit is heavily insulated, and air temperature is maintained at a comfortable level.
- A communication system, with external electrical connection to the spacecraft or PLSS
Means of collecting and containing solid and liquid bodily waste (such as a Maximum Absorbency Garment)
- Advanced suits better regulate the astronaut's temperature with a Liquid Cooling and Ventilation Garment (LCVG) in contact with the astronaut's skin, from which the heat is dumped into space through an external radiator in the PLSS.
Additional requirements for EVA include:
- Shielding against ultraviolet radiation
- Limited shielding against particle radiation
- Means to maneuver, dock, release, and/or tether onto a spacecraft
- Protection against small micrometeoroids, some traveling at up to 27,000 kilometers per hour, provided by a puncture-resistant Thermal Micrometeoroid Garment, which is the outermost layer of the suit. Experience has shown the greatest chance of exposure occurs near the gravitational field of a moon or planet, so these were first employed on the Apollo lunar EVA suits (see United States suit models below).
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