page_title: Space suit
section_title: Design concepts
hierarchical_section_title: Space suit / Design concepts
caption_attribution_description: English: NASA Ames AX-5 rigid spacesuit. Español: Traje espacial rígido AX-5 de la NASA Galego: Traxe espacial ríxido AX-5 da NASA
context_page_description: A space suit or spacesuit is a garment worn to keep a human alive in the harsh environment of outer space, vacuum and temperature extremes. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, and are necessary for extravehicular activity, 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.
  Three types of space suits exist for different purposes: IVA, EVA, and IEVA. IVA suits are meant to be worn inside a pressurized spacecraft, and are therefore lighter and more comfortable. IEVA suits are meant for use inside and outside the spacecraft, such as the Gemini G4C suit.
context_section_description: A space suit should allow its user natural unencumbered movement. Nearly all designs try to maintain a constant volume no matter what movements the wearer makes. This is because mechanical work is needed to change the volume of a constant pressure system. If flexing a joint reduces the volume of the space suit, then the astronaut must 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 one's suit. It also makes delicate movements very difficult. The work required to bend a joint is dictated by the formula
  where Vᵢ and Vf are respectively the initial and final volume of the joint, P is the pressure in the suit, and W is the resultant work. It is generally true that all suits are more mobile at lower pressures. However, because a minimum internal pressure is dictated by life support requirements, the only means of further reducing work is to minimize the change in volume.
  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 inside 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 causes pockets of fabric, called "gores," to open up on the outside of the joint, while folds called "convolutes" fold up on the inside of the joint. The gores make up for the volume lost on the inside of the joint, and keep the suit at a nearly constant volume. However, once the gores are opened all the way, the joint cannot be bent any further without a considerable amount of work.
  In some Russian space suits, strips of cloth were wrapped tightly around the cosmonaut's arms and legs outside the space suit to stop the space suit from ballooning when in space.
  The outermost layer of a space suit, the Thermal Micrometeoroid Garment, provides thermal insulation, protection from micrometeoroids, and shielding from harmful solar radiation.
  There are four main conceptual approaches to suit design:
caption: NASA's experimental AX-5 hard-shell space suit (1988)
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