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Aviation Supplies
A space suit is a complex system of garments, 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 (EVA) 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 for other specialized tasks, such as high-altitude reconnaissance flight. Above Armstrong's Line (~63,000 ft/~19,000 m), pressurized suits are needed in the sparse atmosphere. Hazmat suits that superficially resemble space suits are sometimes used when dealing with biological hazards. A G-suit is worn by aviators and astronauts who are subject to high levels of acceleration ('G') during flight. It is designed to prevent a black-out and g-LOC (g-induced Loss Of Consciousness), due to the blood pooling in the lower part of the body when under G, thus depriving the brain of blood. Spacesuit requirementsSeveral things are needed for the space suit to function properly in space. It must provide:
Operating pressureGenerally, to supply enough oxygen for respiration, a spacesuit using pure oxygen must have a pressure of about 4.7 psi (32.4 kPa), equal to the 3 psi (20.7 kPa) partial pressure of oxygen in the Earth's atmosphere at sea level, plus 40 torr (5.3 kPa) CO2 and 47 torr (6.3 kPa) water vapor pressure, both of which must be subtracted from the alveolar pressure to get alveolar oxygen partial pressure in 100% oxygen atmospheres, by the alveolar gas equation.[1] The latter two figures add to 87 torr (11.6 kPa, 1.7 psi), which is why many modern spacesuits don't use 3 psi, but 4.7 psi (this is a slight overcorrection, as alveolar partial pressures at sea level are not a full 3 psi, but a bit less). In spacesuits that use 3 psi, the astronaut gets only 3 - 1.7 = 1.3 psi (9 kPa) of oxygen, which is about the alveolar oxygen partial pressure attained at an altitude of 6100 ft (1860 m) above sea level. This is about 78% of normal sea level pressure, about the same as pressure in a commercial passenger jet aircraft, and is the realistic lower limit for safe ordinary space suit pressurization which allows reasonable work capacity. Theories of spacesuit designA 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 changes the volume of the spacesuit, 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 your 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. Because pressure is dictated by life support requirements, the only means of 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 round the spaceman's arms and legs outside the spacesuit to stop the spacesuit 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 three theoretical approaches to suit design: Hard-shell suitsHard-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 joints, and often end up in odd positions that must be manipulated to regain mobility. Mixed suitsMixed suits have hard-shell parts and fabric parts. NASA's Extravehicular Mobility Unit uses a fiberglass Hard Upper Torso (HUT) and fabric limbs. ILC Dover's I-Suit replaces the hard upper torso with a fabric soft upper torso to save weight, restricting the use of hard components to the joint bearings, helmet, waist seal, and rear entry hatch. Virtually all workable spacesuit designs incorporate hard components, particularly at interfaces such as is the waist seal, bearings, and in the case of rear-entry suits, the back hatch, where all-soft alternatives are not viable. Skintight suitsSkintight suits, also known as mechanical counterpressure suits or space activity suits, are a proposed design which would use a heavy elastic body stocking to compress the body. The head is 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, reduces the possibility of a space suit depressurization and gives a very lightweight suit. 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. Contributing technologiesRelated 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. 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". Spacesuit models of historical significanceHigh altitude suits
Russian suit models
American suit models
Chinese suit models
Emerging technologiesSeveral companies and universities are developing technologies and prototypes which represent improvements over current spacesuits. Mark IIIThe Mark III is a NASA prototype, constructed by ILC Dover, which incorporates a hard lower torso section and a mix of soft and hard components. The Mark III is markedly more mobile than previous suits, despite its high operating pressure (8.3 psi/57kPa), which makes it a "zero-prebreathe" suit, meaning that astronauts would be able to transition directly from a one atmosphere, mixed gas space station environment, such as that on the International Space Station, to the suit, without health risks such as the bends which can occur with rapid depressurization from an atmosphere containing Nitrogen. I-SuitThe I-Suit is a spacesuit prototype also constructed by ILC Dover, which incorporates several design improvements over the EMU, including a weight-saving soft upper torso. Both the Mark III and the I-Suit have taken part in NASA's annual Desert Research and Technology Studies (D-RATS) field trials, during which suit occupants interact with one another, and with rovers and other equipment. Bio-SuitBio-Suit is a space activity suit under development at the Massachusetts Institute of Technology, which as of 2006 consists of several lower leg prototypes. Bio-suit is custom fit to each wearer, using laser body scanning MX-2The MX-2 is a space suit analogue constructed at the University of Maryland's Space Systems Laboratory. The MX-2 is used for manned neutral buoyancy testing at the Space Systems Lab's Neutral Buoyancy Research Facility. By approximating the work envelope of a real EVA suit, without meeting the requirements of a flight-rated suit, the MX-2 provides an inexpensive platform for EVA research, compared to using EMU suits at facilities like NASA's Neutral Buoyancy Laboratory. The MX-2 has an operating pressure of 2.5–4 psi. It is a rear-entry suit, featuring a fiberglass hard upper torso. Air, LCG cooling water, and power are open loop systems, provided through an umbilical. The suit includes a mac mini to capture sensor data, such as suit pressure, inlet and outlet air temperatures, and heart rate.[5] Resizable suit elements and adjustable ballast allow the suit to accommodate subjects ranging in height from 68 in. to 75 in., and with a weight range of 120 lb.[6] North Dakota suitBeginning in May 2006, five North Dakota schools collaborated on a new spacesuit prototype, funded by a $100,000 grant from NASA, to demonstrate technologies which could be incorporated into a planetary suit. The suit was tested in the Theodore Roosevelt National Park badlands of western North Dakota. The suit weighs 47 pounds without a life support backpack, and costs only a fraction of the standard $22,000,000 cost for a flight-rated NASA spacesuit. The suit was developed in just over a year by students from the University of North Dakota, North Dakota State, Dickinson State, the state College of Science and Turtle Mountain Community College.[7] The mobility of the North Dakota suit can be attributed to its low operating pressure; while the North Dakota suit was field tested at a pressure of 1 psi differential, NASA's EMU suit operates at a pressure of 4.7 psi, a pressure designed to supply approximately sea-level oxygen partial pressure for respiration (see discussion above). NASA Constellation Space Suit SystemOn August 2, 2006, NASA indicated plans to issue a Request for Proposal (RFP) for the design, development, certification, production, and sustaining engineering of a space suit system to meet the needs of Project Constellation.[8] NASA foresees a single suit capable of supporting: survivability during launch, entry and abort; zero-gravity EVA; lunar surface EVA; and Mars surface EVA. Spacesuits in fiction
For as long as there has been fiction set in space, authors have tried to describe the space suits worn by their characters. These fictional suits vary in appearance and technology, and range from the highly authentic to the utterly improbable. A very early fictional account of space suits can be seen in the book Edison's Conquest of Mars (1898). Later comic book series such as Buck Rogers (1930s) and Dan Dare (1950s) also featured their own takes on space suit design. Science fiction authors such as Robert A. Heinlein contributed to the development of fictional space suit concepts. See also
References
External links Wikimedia Commons has media related to:
A G-suit is worn by aviators and astronauts who are subject to high levels of acceleration ('G'). It is designed to prevent a black-out and g-LOC (g-induced Loss Of Consciousness), due to the blood pooling in the lower part of the body when under G, thus depriving the brain of blood.
OperationA G-suit does not so much increase the G-threshold, but makes it possible to sustain high G longer without excessive physical fatigue. Pilots still need to practice the 'G-straining maneuver' that consists of tensing the abdominal muscles in order to tighten blood vessels so as to reduce blood pooling in the lower body. High G is not comfortable, even with a G-suit. In older fighter aircraft, 6 G was considered high, but with modern fighters 9 or even 10 G can be sustained aerodynamically making the pilot the critical factor in maintaining high maneuverability in close combat. DesignA 'G Suit' is a special garment and generally takes the form of tightly-fitting trousers, which fit either under or over (depending on the design) the flying suit worn by the aviator or astronaut. The trousers are fitted with inflatable bladders which, when pressurized through a G-sensitive valve in the aircraft or spacecraft, press firmly on the abdomen and legs, thus restricting the draining of blood away from the brain during periods of high acceleration. In addition, in some modern very high-G aircraft, the Anti-G suit effect is augmented by a small amount of pressure applied to the lungs (partial pressure breathing), which also enhances resistance to high G. The effects of Anti-G suits and partial pressure breathing are straightforward to replicate in a simulator, although the continuous G forces themselves can only be produced artificially in devices such as centrifuges. Various designs of G-suit have been developed. They first used water-filled bladders around the lower body and legs. Later designs used air under pressure to inflate the bladders. These G-suits were lighter than the fluid-filled versions and are still in extensive use. However, the Swiss company Life Support Systems AG and the German Autoflug GmbH collaborated to design the new Libelle suit for use with the Eurofighter Typhoon aircraft, which reverts to liquid as the medium and improves on performance. The Libelle suit is under consideration for adoption by the United States Air Force. If blood is allowed to pool in the lower areas of the body, the brain will be deprived of blood leading to temporary hypoxia. Hypoxia causes first a brownout (a dimming of the vision), also called grey-out, followed by tunnel-vision and ultimately a blackout (unconsciousness), that is G-induced Loss of Consciousness or 'G-LOC'. The danger of G-LOC to aircraft pilots is magnified because on relaxation of G there is a period of disorientation before full sensation is re-gained. Need for trainingG-LOC has resulted in a number of fatalities in which the aircraft and crew are lost. There is a need for high-G training and this can be accomplished in a man-rated centrifuge training system. Such systems are made by AMST Systemtechnik in Austria (Austria Metall SystemTechnik), the Environmental Tectonics Corporation (ETC) and in the USA. HistoryAs early as 1917, there were documented cases of loss of consciousness due to g-forces in pilots. In 1931 a Professor of Physiology from the University of Sydney described a new way of determining the center of gravity of the human body. This made it possible to describe the displacement of mass within the body under acceleration. With the development of high-speed monoplane fighters in the late 1930s, G-effects in combat became more critical. In the Battle of Britain in 1940, some German aircraft had foot-rests above the rudder pedals so that the pilot's feet and legs could be raised during combat, in which large use of the rudder was often not necessary but turning inside the opponent, was. The Franks G-UnitThe first G-suit was developed by a team led by Wilbur R. Franks at the University of Toronto's Banting and Best Institute in 1941. This used water filled bladders around the legs and two Marks were developed:
Prone pilot positions
Air-based G-suits were very common in NATO aircraft of all nations from the 1950s onwards and are still in common use today. Later jets such as the BAe Hawk, F-16 Falcon, F-18 Hornet, Eurofighter Typhoon and the Dassault Rafale can sustain high-G for longer periods, and are therefore more physically demanding. However, by using a modern g-suit a pilot can now be expected to sustain flight forces of up to 9 G without blacking out. Astronauts wear similar G-suits to aviators but face different challenges due to the effects of microgravity. Aviator G-suits apply uniform pressure to the lower legs to minimize the effects of high acceleration but research from the Canadian Space Agency implies there might be a benefit in having a suit for astronauts that uses a "milking action" to increase blood flow to the upper body. External links
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia Encyclopedia article "Space Suit" |
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