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A space suit is a complex system of garments and equipment and environmental systems designed to keep a person alive and comfortable in the harsh environment of outer space. This applies to extra-vehicular activity outside spacecraft orbiting Earth and has applied to walking, and riding the Lunar Rover, on the Moon.

Some of these requirements also apply to pressure suits worn by people such as high-altitude fighter pilots who may fly so high that breathing pure oxygen at surrounding pressure would not provide enough oxygen for them to function: see hypoxia.

Spacesuit requirements

Several things are needed for the spacesuit to function properly in space. It must provide:

• a stable internal pressure. This can be less than earth's atmosphere, as there is usually no need for the spacesuit to carry nitrogen.
• breathable oxygen. Usually a rebreather is used along with a supply of fresh oxygen.
• temperature regulation. Heat can only be lost in space by thermal radiation, or conduction with objects in physical contact with the space suit. Since heat is lost very slowly by radiation, a space suit almost always has only a cooling system and heavy insulation on the hands and possibly feet.
• electromagnetic radiation shielding.
• micrometeoroid protection.
• mobility.
• a communication system.
• means to recharge and discharge gases and liquids.
• means to maneuver, dock, release, and tether on space craft.

Theories of Spacesuit Design

A space suit should allow its user natural and unencumbered movement. The only way this is possible is for the space suit to maintain a constant volume no matter what position the wearer is in. This is because mechanical work is needed to change the volume of a constant pressure system. If moving an arm or hand causes a change in the volume of the space suit, then the astronaut has to do extra work every time he bends that joint, and he has to maintain a force to keep the joint bent. Even if this force is very small, it can be seriously fatiguing to constantly fight against your suit. It also makes delicate movements very difficult.

All space suit designs try to minimize or eliminate this problem. The most common solution is to form the suit out of multiple layers. The bladder layer is a rubbery, airtight layer much like a balloon. The restraint layer goes outside the bladder, and provides a specific shape for the suit. Since the bladder layer is larger than the restraint layer, the restraint takes all of the stresses caused by the pressure of the suit. Since the bladder is not under pressure, it will not "pop" like a balloon, even if punctured. The restraint layer is shaped in such a way that bending a joint will cause pockets of fabric, called gores, to open up on the outside of the joint. This makes up for the volume lost on the inside of the joint, and keeps the suit at a constant volume. However, once the gores are opened all the way, the joint cannot be bent anymore without a considerable amount of work.

In some Russian spacesuits strips of cloth were wrapped tightly round the spaceman's arms and legs outside the spacesuit to stop the spacesuit from ballooning when in space.

There are three theoretical approaches:

• Hard-shell suits are usually made of metal or composite materials. While they resemble suits of armor, they are also designed to maintain a constant volume. However they tend to be difficult to move, as they rely on bearings instead of bellows over the joins, and often end up in odd positions that must be manipulated to regain mobility.
• Mixed suits have hard-shell parts and fabric parts. NASA's Extravehicular Mobility Unit uses a hard-shell torso and fabric limbs.
• Skintight suits, or mechanical counterpressure suits, use a heavy elastic body stocking to compress the body. The head is encompassed in a pressurized helmet, but the rest of the body is pressurized only by the elastic effect of the suit. This eliminates the constant volume problem, and reduces the possibility of a space suit depressurization. However, these suits are very difficult to put on and face problems with providing a constant pressure everywhere. Most proposals use the body's natural sweat to keep cool. See space activity suit for more information.

One inconvenience with some spacesuits is the head being fixed facing forwards and being unable to turn to look sideways: astronauts call this effect "alligator head".

Contributing technologies

Related preceding technologies include the gas mask used in WWII, the oxygen mask used by pilots of high flying bombers in WWII, the high altitude or vacuum suit required by pilots of the Lockheed U-2 and SR-71 Blackbird, the diving suit, rebreather, scuba diving gear and many others.

The development of the spheroidal dome helmet was key in balancing the need for field of view, pressure compensation, and low weight.

Spacesuit models of historical significance

• High altitude suits
  • Evgeniy Chertanovskiy created his full-pressure suit or high-altitude skafander in 1931.
  • Wiley Post experimented with a number of hard-shell designs for record-breaking flights
• Russian suit models
  • SK-1, the space suit of Yuri Gagarin, first man in space orbits Earth
  • Berkut, the space suit of Alexey Leonov, the cosmonaut who made first spacewalk.
  • the Yastreb space suit for extra-vehicular activity
  • the Orlan suits for extra-vehicular activity
  • the Sokol suits worn by Soyuz crew members during lift-off and re-entry
  • the Strizh space suit developed for pilots of Buran space shuttle
• Mercury high-altitude/vacuum suit
• Gemini spacewalk suits
• Apollo lunar surface suits
• Skylab
• Advance Crew Escape System Pressure Suit on the Space Shuttle
• Emerging technologies
  • Hard shell
  • Space activity suit

Spacesuits in fiction

Fiction authors have been trying to design spacesuits since the beginning of space fiction, as far as there was need to describe them in their stories. Most of them are flexible pressure suits, but usually not as bulky as in real spacesuits. Design was influenced by the real old-type Siebe Gorman Standard diving dress, including sometimes such features as side windows on the helmet. In H.G. Wells's The First men in the Moon (publ. 1901) Standard Diving Dresses are fitted with a big backpack cylinder each and used as spacesuits. Many fictional spacesuits have two big backpack cylinders as their only life-support gear, as if the wearer breathes out to space like in ordinary sport open-circuit scuba. In the well-known Dan Dare series which started in April 1950 in the `Eagle' comic, the usual Spacefleet spacesuit has no backpack, and a corselet like in Standard Diving Dress. Comic-strip space story authors often do not know about the effects of internal pressure inflating the spacesuit in space, but draw the spacesuit in space hanging in folds like a boilersuit: that can often be seen in the Dan Dare stories.

Skintight spacesuits (skinsuits) appear in the original Buck Rogers comics. The Buck Rogers scenario has become familiar enough to cause expressions such as "Buck Rogers outfit" for real protective suits that look somewhat like spacesuits. Skinsuits are more common in modern science fiction. On the other end of the spectrum one can find the ideas of heavy powered armor. Robert A. Heinlein's novel Have Space Suit-Will Travel draws on his experience designing pressure suits during World War II.

It is possible that fictional spacesuit design influenced real spacesuit design somewhat, at least in getting real spacesuits to use a hard helmet and not a soft pressurized hood.

Alien spacesuits in the Gerry Anderson UFO series are filled with a breathable liquid to resist acceleration stresses.

After NASA started, fictional spacesuits often followed real spacesuit design, in such features as having a large rectangular backpack. In making the spacesuits that are seen in the Dune movie, the prop and costume designers stated a need to avoid "that NASA look", and the same consideration may have arisen in some other movies and series.

Spacesuits are commonly used in the Gundam anime metaseries, but are often renamed to avoid confusion with space-use mobile suits (which are said to take their names from the fact that they are mechanically mobile evolutions of spacesuits). In the Universal Century timeline, spacesuits are called "normal suits", while the After Colony timeline uses the term "astrosuit". Gundam spacesuits often feature a pouch full of adhesive strips, used to temporarily seal tears in the suit or cracks in the helmet (as demonstrated in Mobile Suit Gundam and Char's Counterattack respectively).

See also

• Manned maneuvering unit
• Space activity suit
• Human adaptation to space

External links

• Russian Space Suits

• NASA JSC Oral History Project: See link near page end to Walking to Olympus: An EVA Chronology PDF document.
• NASDA Online Space Notes
• Apollo Extravehicular mobility unit. Volume 1: System description - 1971 (PDF document)
• Apollo Extravehicular mobility unit. Volume 2: Operational procedures - 1971 (PDF document)
• Skylab Extravehicular Activity Development Report - 1974 (PDF document)
• Analysis of the Space Shuttle Extravehicular Mobility Unit - 1986 (PDF document)
• NASA Space Shuttle EVA tools and equipment reference book - 1993 (PDF document)
• Interactive EVA with MMU

"Space Suit" is an instrumental track from They Might Be Giants' 1992 album Apollo 18.

• Environmental suits
• Space exploration
• Spacecraft components