Space activity suit
Encyclopedia
A space activity suit or mechanical counterpressure suit is an experimental spacesuit which applies stable pressure against the skin by means of skintight elastic garments. The SAS is not inflated like a conventional spacesuit: it uses mechanical pressure, rather than air pressure, to compress the human body in low pressure environments. Development was begun by NASA and Paul Webb in the late 1960s but was discontinued in the early 1970s. Pressurized suits are still used . Research is under way at the Massachusetts Institute of Technology
(MIT) on a "Bio-Suit" System which is based on the original SAS concept.
of space unprotected, despite contrary depictions in some popular science fiction
. Human flesh expands to about twice its size in such conditions, giving the visual effect of a body builder rather than an overfilled balloon. Consciousness is retained for up to 15 seconds as the effects of oxygen starvation
set in. No snap freeze effect occurs because all heat must be lost through thermal radiation
or the evaporation
of liquids, and the blood does not boil because it remains pressurized within the body. The greatest danger is in attempting to hold one's breath before exposure, as the subsequent explosive decompression can damage the lungs. These effects have been confirmed through various accidents (including in very high altitude conditions, outer space and training vacuum chambers). Human skin does not need to be protected from vacuum and is gas-tight by itself. Instead it only needs to be mechanically compressed to retain its normal shape. This can be accomplished with a tight-fitting elastic body suit and a helmet to contain breathing gases and protect the ears and eyes.
Original development of such a suit was funded by NASA
and conducted by Paul Webb, who published a paper entitled "The Space Activity Suit: An Elastic Leotard for Extravehicular Activity" in the April 1968 issue of Aerospace Medicine. The report was extremely positive, so further work was contracted in order to test various design concepts. Between 1968 and 1971 ten designs of increasing sophistication were built, leading eventually to a series of successful tests in vacuum chambers. The longest test was two hours and forty-five minutes.
The tests were successful: the practicality of a mechanical counter pressure spacesuit was demonstrated conclusively. The energy needed to move about was considerably less than conventional designs, which was a major improvement for long-duration spacewalks. Tests of punctures showed that up to a square millimeter of skin could be directly exposed to vacuum for extended periods with no permanent effect. Conventional suits under the same conditions which would lose pressure and breathing air. It weighed half as much as the the primary pressure suit
worn by NASA
astronauts for Project Apollo
, the A7L
.
A number of problems also turned up, primarily related to the problem of keeping the suit in strong mechanical contact at every point on the body. Concavities or small folds in the fabric could lead to fluid pooling in the gaps; the crotch area proved extremely difficult to tailor successfully. To correct this, small pads of polyurethane foam were inserted into concavities and were successful in most problem areas. The suits had to be tailored to each individual, although the same was true of the earlier Apollo suits. The largest difficulty was donning and removing the suit. In order to effectively provide the minimum pressure of 29.6 kPa (222 mmHg; 4.3 psi) necessary for human physiology, the suit had to be extremely tight-fitting, making donning and doffing a highly strenuous task.
In 1971, Webb, along with James F. Annis, published their findings in NASA CR-1892, "Development of a Space Activity Suit". The report remained positive, and the researchers felt that further improvements were possible. Quoting the Report:
weave for lower-tension areas. Both were based on a heavy elastic warp
thread with a much less elastic weft
thread to form a netting. The terms warp and weft are used loosely here, as the material was not woven
using traditional means. Powernet used spandex
cord as the warp with nylon cord as the weft, allowing movement primarily along the warp axis. Bobbinet used cotton-wrapped rubber warp and nylon or dacron weft, and was flexible in both directions. The cotton wrapping limited the maximum stretch to 200% of the rest length. The amount of over-pressure bobbinet could create was about 2 kPa (15 mmHg; 0.290075475467502 psi) over the torso, the largest volume, and up to 5.3 kPa (39.8 mmHg; 0.76870000998888 psi) over smaller radius curves on the wrist and ankles. Powernet could produce about 6.7 kPa (50.3 mmHg; 0.971752842816131 psi) even on the torso. A minimum of 17.3 kPa (129.8 mmHg; 2.5 psi) is needed for normal breathing.
Multiple layers and patches of the two materials were used to control the overall mechanical pressure around the body. Starting at the skin, a "slip layer" of light powernet was used to allow the outer layers to slide over the skin without binding. Under this layer a number of foam pads were placed on various concavities on the body to keep them in contact with the suit. On top of this was the counter-pressure bladder, part of the breathing system. On top of this were up to six additional layers of powernet over the trunk with bobbinet arms and legs, or all-bobbinet garments covering the trunk only. The garments were put on like a normal bodysuit with a large zipper closing the front, with additional drawstrings at some points to help close the garment. Zippers on alternating layers were offset.
The positive-pressure breathing system consisted of three main portions: the pressurized helmet, the breathing bladder, and the tankage system in a backpack. The bladder and helmet were connected together to pump air out of the bladder and over the torso when the user breathed in, reducing the amount of pressure on the user's chest. The helmet was secured by means of a non-elastic garment of Nomex
cloth which wrapped around the chest and under the under the arms, and by the elastic layers above and below it.
at the direction of professor Dava Newman
, with support from the NASA Institute for Advanced Concepts
. Similar to the SAS in concept, the BioSuit applies a number of advances in engineering and measurement to produce a dramatically simplified version of the SAS design.
Newman has worked extensively in biomechanics
, especially in the field of computerized measurement of human movement. Applying this knowledge, Newman's team looked for points on the body where stretching motions did not take place by painting a series of circles over a portion of the body and then watching their deformations as the wearer walked around or performed various tasks. The circles deform into ellipses as the skin stretches over the moving musculature, and these deformations were recorded. After a huge number of such measurements the data is then examined to find all of the possible deformations of the circles, and more importantly, the non-moving points on them where the original circle and the deformed ellipse intersect (at four points per circle). By mapping these points over the entire body, a series of lines are produced that Newman refers to as "lines of non-elongation". These lines generally follow the musculation; for instance, there is a prominent line of non-elongation running from the shoulder area, down the front of the body, then curving under the armpit. This follows the line where the subscapularis connects to the skeleton.
The primary structure of the BioSuit is built by placing elastic cords along lines of non-elongation. As the cords will not be stretched along these lines - at least in normal movements - whatever pressure they provide will be constant even as the wearer moves. In this way, they can very accurately control the mechanical counter-pressure the suit applies. The rest of the suit is then built up from spandex
lying between the primary pressure cords. The Bio-Suit team has thus far constructed a number of lower leg prototypes using different materials, including nylon-spandex, elastic, and urethane-painted foam. In one experimental design, kevlar
fabric was used between the cords for areas where the expansion was limited. Each suit has to be custom tailored for the wearer, but the complexity of this task is greatly reduced through the use of whole-body laser scans.
The result is a one-layer version of the SAS; it is lighter than the original and considerably more flexible, allowing much more natural motion and decreasing the energy cost of motion. Current versions of portions the BioSuit have consistently reached 25 kPa (187.5 mmHg; 3.6 psi), and the team is currently aiming for 30 kPa (225 mmHg; 4.4 psi) for a baseline design. As mechanical counter-pressure has proven difficult for small joints such as those in the hands, the BioSuit baseline design uses gas-filled gloves and boots, in addition to a gas-filled helmet.
and Larry Niven
have made use of space activity suits in their stories. The potential for greater mobility and simpler operation with a space activity suit make it an attractive choice for fiction, where flexibility of use can be a boon to plot development. The aesthetic qualities of a sleek, form-fitting space activity suit also contrast the traditional image of rigid, diving-suit-style spacesuits, lending a futuristic look to costumes. Most anime
with futuristic themes include the skintight spacesuit (with the notable exception of Planetes
and, to a lesser extent, the Gundam
franchise). In the Mars Trilogy
by Kim Stanley Robinson, a suit similar to this is referred to as a "walker".
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
(MIT) on a "Bio-Suit" System which is based on the original SAS concept.
Development
The human body can briefly survive the hard vacuumVacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
of space unprotected, despite contrary depictions in some popular science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
. Human flesh expands to about twice its size in such conditions, giving the visual effect of a body builder rather than an overfilled balloon. Consciousness is retained for up to 15 seconds as the effects of oxygen starvation
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
set in. No snap freeze effect occurs because all heat must be lost through thermal radiation
Thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....
or the evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
of liquids, and the blood does not boil because it remains pressurized within the body. The greatest danger is in attempting to hold one's breath before exposure, as the subsequent explosive decompression can damage the lungs. These effects have been confirmed through various accidents (including in very high altitude conditions, outer space and training vacuum chambers). Human skin does not need to be protected from vacuum and is gas-tight by itself. Instead it only needs to be mechanically compressed to retain its normal shape. This can be accomplished with a tight-fitting elastic body suit and a helmet to contain breathing gases and protect the ears and eyes.
Original development of such a suit was funded by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
and conducted by Paul Webb, who published a paper entitled "The Space Activity Suit: An Elastic Leotard for Extravehicular Activity" in the April 1968 issue of Aerospace Medicine. The report was extremely positive, so further work was contracted in order to test various design concepts. Between 1968 and 1971 ten designs of increasing sophistication were built, leading eventually to a series of successful tests in vacuum chambers. The longest test was two hours and forty-five minutes.
The tests were successful: the practicality of a mechanical counter pressure spacesuit was demonstrated conclusively. The energy needed to move about was considerably less than conventional designs, which was a major improvement for long-duration spacewalks. Tests of punctures showed that up to a square millimeter of skin could be directly exposed to vacuum for extended periods with no permanent effect. Conventional suits under the same conditions which would lose pressure and breathing air. It weighed half as much as the the primary pressure suit
Pressure suit
A pressure suit is a protective suit worn by high-altitude pilots who may fly at altitudes where the air pressure is too low for an unprotected person to survive, even breathing pure oxygen at positive pressure. Such suits may be either full-pressure or partial-pressure...
worn by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
astronauts for Project Apollo
Project Apollo
The Apollo program was the spaceflight effort carried out by the United States' National Aeronautics and Space Administration , that landed the first humans on Earth's Moon. Conceived during the Presidency of Dwight D. Eisenhower, Apollo began in earnest after President John F...
, the A7L
Apollo/Skylab A7L
The A7L Apollo & Skylab spacesuit is the primary pressure suit worn by NASA astronauts for Project Apollo, the three manned Skylab flights, and the Apollo-Soyuz Test Project between 1968 and the termination of the Apollo program in 1975. The "A7L" designation is used by NASA as the seventh Apollo...
.
A number of problems also turned up, primarily related to the problem of keeping the suit in strong mechanical contact at every point on the body. Concavities or small folds in the fabric could lead to fluid pooling in the gaps; the crotch area proved extremely difficult to tailor successfully. To correct this, small pads of polyurethane foam were inserted into concavities and were successful in most problem areas. The suits had to be tailored to each individual, although the same was true of the earlier Apollo suits. The largest difficulty was donning and removing the suit. In order to effectively provide the minimum pressure of 29.6 kPa (222 mmHg; 4.3 psi) necessary for human physiology, the suit had to be extremely tight-fitting, making donning and doffing a highly strenuous task.
In 1971, Webb, along with James F. Annis, published their findings in NASA CR-1892, "Development of a Space Activity Suit". The report remained positive, and the researchers felt that further improvements were possible. Quoting the Report:
Construction
The original SAS design was based on two new fabrics: a type of "powernet" (or "girdle fabric") for high-tension areas, and an elastic bobbinetBobbinet
Bobbinet or genuine tulle is a specific type of tulle netting which has been made in the United Kingdom since the invention of the bobbinet machine in 1806 by John Heathcoat. John Heathcoat coined the term "bobbin net", or bobbinet as it is spelled today, to distinguish his machine-made tulle from...
weave for lower-tension areas. Both were based on a heavy elastic warp
Warp (weaving)
In weaving cloth, the warp is the set of lengthwise yarns that are held in tension on a frame or loom. The yarn that is inserted over-and-under the warp threads is called the weft, woof, or filler. Each individual warp thread in a fabric is called a warp end or end. Warp means "that which is thrown...
thread with a much less elastic weft
Weft
In weaving, weft or woof is the yarn which is drawn through the warp yarns to create cloth. In North America, it is sometimes referred to as the "fill" or the "filling yarn"....
thread to form a netting. The terms warp and weft are used loosely here, as the material was not woven
Weaving
Weaving is a method of fabric production in which two distinct sets of yarns or threads are interlaced at right angles to form a fabric or cloth. The other methods are knitting, lace making and felting. The longitudinal threads are called the warp and the lateral threads are the weft or filling...
using traditional means. Powernet used spandex
Spandex
Spandex or elastane is a synthetic fibre known for its exceptional elasticity. It is strong, but less durable than natural Latex, its major non-synthetic competitor. It is a polyurethane-polyurea copolymer that was co-invented in 1959 by chemists C. L. Sandquist and Joseph Shivers at DuPont's...
cord as the warp with nylon cord as the weft, allowing movement primarily along the warp axis. Bobbinet used cotton-wrapped rubber warp and nylon or dacron weft, and was flexible in both directions. The cotton wrapping limited the maximum stretch to 200% of the rest length. The amount of over-pressure bobbinet could create was about 2 kPa (15 mmHg; 0.290075475467502 psi) over the torso, the largest volume, and up to 5.3 kPa (39.8 mmHg; 0.76870000998888 psi) over smaller radius curves on the wrist and ankles. Powernet could produce about 6.7 kPa (50.3 mmHg; 0.971752842816131 psi) even on the torso. A minimum of 17.3 kPa (129.8 mmHg; 2.5 psi) is needed for normal breathing.
Multiple layers and patches of the two materials were used to control the overall mechanical pressure around the body. Starting at the skin, a "slip layer" of light powernet was used to allow the outer layers to slide over the skin without binding. Under this layer a number of foam pads were placed on various concavities on the body to keep them in contact with the suit. On top of this was the counter-pressure bladder, part of the breathing system. On top of this were up to six additional layers of powernet over the trunk with bobbinet arms and legs, or all-bobbinet garments covering the trunk only. The garments were put on like a normal bodysuit with a large zipper closing the front, with additional drawstrings at some points to help close the garment. Zippers on alternating layers were offset.
The positive-pressure breathing system consisted of three main portions: the pressurized helmet, the breathing bladder, and the tankage system in a backpack. The bladder and helmet were connected together to pump air out of the bladder and over the torso when the user breathed in, reducing the amount of pressure on the user's chest. The helmet was secured by means of a non-elastic garment of Nomex
Nomex
Nomex is a registered trademark for flame resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.- Properties:...
cloth which wrapped around the chest and under the under the arms, and by the elastic layers above and below it.
Bio-Suit
The Bio-Suit is an experimental space activity suit under construction at the Massachusetts Institute of TechnologyMassachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
at the direction of professor Dava Newman
Dava Newman
Dava J. Newman is Professor of Aeronautics and Astronautics and Engineering Systems at the Massachusetts Institute of Technology. She is most notable for assisting NASA in developing new space activity suits, namely the Bio-Suit, which will provide pressure mechanically, rather than with...
, with support from the NASA Institute for Advanced Concepts
NASA Institute for Advanced Concepts
right|200pxNASA Institute for Advanced Concepts was a NASA-funded program that was operated by the Universities Space Research Association for NASA from 1998 until its closure on 31 August 2007. NIAC sought proposals for revolutionary aeronautics and space concepts that could dramatically impact...
. Similar to the SAS in concept, the BioSuit applies a number of advances in engineering and measurement to produce a dramatically simplified version of the SAS design.
Newman has worked extensively in biomechanics
Biomechanics
Biomechanics is the application of mechanical principles to biological systems, such as humans, animals, plants, organs, and cells. Perhaps one of the best definitions was provided by Herbert Hatze in 1974: "Biomechanics is the study of the structure and function of biological systems by means of...
, especially in the field of computerized measurement of human movement. Applying this knowledge, Newman's team looked for points on the body where stretching motions did not take place by painting a series of circles over a portion of the body and then watching their deformations as the wearer walked around or performed various tasks. The circles deform into ellipses as the skin stretches over the moving musculature, and these deformations were recorded. After a huge number of such measurements the data is then examined to find all of the possible deformations of the circles, and more importantly, the non-moving points on them where the original circle and the deformed ellipse intersect (at four points per circle). By mapping these points over the entire body, a series of lines are produced that Newman refers to as "lines of non-elongation". These lines generally follow the musculation; for instance, there is a prominent line of non-elongation running from the shoulder area, down the front of the body, then curving under the armpit. This follows the line where the subscapularis connects to the skeleton.
The primary structure of the BioSuit is built by placing elastic cords along lines of non-elongation. As the cords will not be stretched along these lines - at least in normal movements - whatever pressure they provide will be constant even as the wearer moves. In this way, they can very accurately control the mechanical counter-pressure the suit applies. The rest of the suit is then built up from spandex
Spandex
Spandex or elastane is a synthetic fibre known for its exceptional elasticity. It is strong, but less durable than natural Latex, its major non-synthetic competitor. It is a polyurethane-polyurea copolymer that was co-invented in 1959 by chemists C. L. Sandquist and Joseph Shivers at DuPont's...
lying between the primary pressure cords. The Bio-Suit team has thus far constructed a number of lower leg prototypes using different materials, including nylon-spandex, elastic, and urethane-painted foam. In one experimental design, kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
fabric was used between the cords for areas where the expansion was limited. Each suit has to be custom tailored for the wearer, but the complexity of this task is greatly reduced through the use of whole-body laser scans.
The result is a one-layer version of the SAS; it is lighter than the original and considerably more flexible, allowing much more natural motion and decreasing the energy cost of motion. Current versions of portions the BioSuit have consistently reached 25 kPa (187.5 mmHg; 3.6 psi), and the team is currently aiming for 30 kPa (225 mmHg; 4.4 psi) for a baseline design. As mechanical counter-pressure has proven difficult for small joints such as those in the hands, the BioSuit baseline design uses gas-filled gloves and boots, in addition to a gas-filled helmet.
Space activity suits in fiction
Writers including Stephen BaxterStephen Baxter
Stephen Baxter is a prolific British hard science fiction author. He has degrees in mathematics and engineering.- Writing style :...
and Larry Niven
Larry Niven
Laurence van Cott Niven / ˈlæri ˈnɪvən/ is an American science fiction author. His best-known work is Ringworld , which received Hugo, Locus, Ditmar, and Nebula awards. His work is primarily hard science fiction, using big science concepts and theoretical physics...
have made use of space activity suits in their stories. The potential for greater mobility and simpler operation with a space activity suit make it an attractive choice for fiction, where flexibility of use can be a boon to plot development. The aesthetic qualities of a sleek, form-fitting space activity suit also contrast the traditional image of rigid, diving-suit-style spacesuits, lending a futuristic look to costumes. Most anime
Anime
is the Japanese abbreviated pronunciation of "animation". The definition sometimes changes depending on the context. In English-speaking countries, the term most commonly refers to Japanese animated cartoons....
with futuristic themes include the skintight spacesuit (with the notable exception of Planetes
Planetes
is a Japanese hard science fiction manga by Makoto Yukimura. It was adapted as a 26-episode television anime by Sunrise, which was broadcast on NHK from October 2003 through April 2004...
and, to a lesser extent, the Gundam
Gundam
The is a metaseries of anime created by Sunrise studios that features giant robots called "Mobile Suits" ; usually the protagonist's MS will carry the name Gundam....
franchise). In the Mars Trilogy
Mars trilogy
The Mars trilogy is a series of award-winning science fiction novels by Kim Stanley Robinson that chronicles the settlement and terraforming of the planet Mars through the intensely personal and detailed viewpoints of a wide variety of characters spanning almost two centuries...
by Kim Stanley Robinson, a suit similar to this is referred to as a "walker".
Further reading
- Webb, Paul. "The Space Activity Suit: An Elastic Leotard for Extravehicular Activity". Aerospace Medicine, April 1968, pp. 376--383.
External links
- One giant leap for space fashion: MIT team designs sleek, skintight spacesuit
- The Space Activity Suit: An Elastic Leotard for Extravehicular Activity, the original 1968 paper (Microsoft DOC format)
- Development of a Space Activity Suit, the 1971 NASA contractor report, NASA CR-1892, as a PDFPortable Document FormatPortable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....
file - Physiological Effects of a Mechanical Counter Pressure Suit, PDF file