Space suit

A space suit is a garment worn to keep an astronaut[1] alive in the harsh environment (vacuum and temperature extremes) of outer space. Space suits 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 Union SK-1 suit worn by Yuri Gargarin in 1961.

Contents

Spacesuit requirements

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:

Optional requirements

Additional requirements for EVA include:

As part of astronautical hygiene control (i.e., protecting astronauts from extremes of temperature, radiation, etc.), a spacesuit is essential for extravehicular activity. The Apollo/Skylab A7L suit included eleven layers in all: an inner liner, a liquid cooling and ventilation garment, a pressure bladder, a restraint layer, another liner, and a thermal micrometeoroid garment consisting of five aluminized insulation layers and an external layer of white Ortho-Fabric. This spacesuit is capable of protecting the astronaut from temperatures ranging from −156 °C (−249 °F) to 121 °C (250 °F).

It is expected that manned exploration of the Moon and Mars will occur within the next two decades. During exploration, there will be the potential for lunar/Martian dust to be retained on the spacesuit. When the spacesuit is removed on return to the spacecraft, there will be the potential for the dust to contaminate surfaces and increase the risks of inhalation and skin exposure. Astronautical hygienists are testing materials with reduced dust retention times and the potential to control the dust exposure risks during planetary exploration. Novel ingress/egress approaches, such as suitports, are being explored as well.

In NASA spacesuits, communications are provided via a cap worn over the head, which includes earphones and a microphone. Due to the coloration of the version used for Apollo and Skylab, which resembled the coloration of the comic strip character Snoopy, these caps became known as "Snoopy caps".

Operating pressure

Generally, to supply enough oxygen for respiration, a spacesuit using pure oxygen must have a pressure of about 32.4 kPa (240 Torr; 4.7 psi), equal to the 20.7 kPa (160 Torr; 3.0 psi) partial pressure of oxygen in the Earth's atmosphere at sea level, plus 5.3 kPa (40 Torr; 0.77 psi) CO2 and 6.3 kPa (47 Torr; 0.91 psi) 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.[2] The latter two figures add to 11.6 kPa (87 Torr, 1.7 psi), which is why many modern spacesuits do not use 20.7 kPa (160 Torr; 3.0 psi), but 32.4 kPa (240 Torr; 4.7 psi) (this is a slight overcorrection, as alveolar partial pressures at sea level are slightly less than the former). In spacesuits that use 20.7 kPa, the astronaut gets only 20.7 kPa − 11.7 kPa = 9.0 kPa (68 Torr; 1.3 psi) of oxygen, which is about the alveolar oxygen partial pressure attained at an altitude of 1,860 m (6,100 ft) 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 capacity for work.

When space suits below a specific operating pressure are used from craft that are pressurized to normal atmospheric pressure (such as the space shuttle), this requires astronauts to "pre-breathe" (meaning pre-breathe pure oxygen for a period) before donning their suits and depressurizing in the air lock. This procedure purges the body of dissolved nitrogen, so as to avoid decompression sickness ("the bends") due to overrapid depressurization from a nitrogen-containing atmosphere.

Exposure to space without a spacesuit

The human body can briefly survive the hard vacuum of space unprotected,[3] 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).[4][5] 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 for containing breathing gases, known as a Space activity suit.

Theories of spacesuit design

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 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 one's suit. It also makes delicate movements very difficult. The work required to bend a joint is dictated by the formula

W=\int_{V_i}^{V_f} \,P\,dV

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 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 four theoretical approaches to suit design:

Soft suits

Soft suits typically are made mostly of fabrics. All soft suits have some hard parts, some even have hard joint bearings. Intra-vehicular activity and early EVA suits were soft suits.

Hard-shell suits

Hard-shell suits are usually made of metal or composite materials and do not use fabric for joints. Hard suits joints use ball bearings and wedge-ring segments similar to an adjustable elbow of a stove pipe to allow a wide range of movement with the arms and legs. The joints maintain a constant volume of air internally and do not have any counter force. Therefore, the astronaut does not need to exert to hold the suit in any position. Hard suits can also operate at higher pressures which would eliminate the need for an astronaut to pre-breath oxygen to use a 5.0 PSI space suit before an EVA from the 14.7 PSI space shuttle as astronauts currently do. The joints may get into a restricted or locked position requiring the astronaut to manipulate or program the joint. The Nasa Ames AX5 suit had a flexibility rating of 95%. The wearer could move into 95% of the positions he or she could while nude.

Hybrid suits

Hybrid 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 the waist seal, bearings, and in the case of rear-entry suits, the back hatch, where all-soft alternatives are not viable.

Skintight suits

Skintight 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 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. 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 significance

High-altitude suits

Russian suit models

American suit models

Chinese suit models

Emerging technologies

Several companies and universities are developing technologies and prototypes which represent improvements over current spacesuits.

Mark III

The 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 (57 kPa/8.3 psi), 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 risking decompression sickness, which can occur with rapid depressurization from an atmosphere containing Nitrogen or another inert gas

I-Suit

The 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-Suit

Bio-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-2

The 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 contains a Mac mini computer to capture sensor data, such as suit pressure, inlet and outlet air temperatures, and heart rate.[20] Resizable suit elements and adjustable ballast allow the suit to accommodate subjects ranging in height from 68 to 75 inches (170–190 cm), and with a weight range of 120 lb (54 kg).[21]

North Dakota suit

Beginning in May 2006 five North Dakota colleges 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 has a mass of 47 pounds (21 kg) without a life support backpack, and costs only a fraction of the standard $12,000,000 cost for a flight-rated NASA spacesuit.[22] 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.[23] 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 (6.9 kPa; 52 Torr) differential, NASA's EMU suit operates at a pressure of 4.7 psi (32 kPa; 240 Torr), a pressure designed to supply approximately sea-level oxygen partial pressure for respiration (see discussion above).

Aouda.X

Since 2009, the Austrian Space Forum [24] has been developing "Aouda.X", an experimental Mars analogue spacesuit focusing on an advanced man-machine interface and on-board computing network to increase situational awareness. The suit is designed to study contamination vectors in planetary exploration analogue environments and create limitations depending on the pressure regime chosen for a simulation. An advanced human-machine interface, a set of sensors and a purpose designed software act as a local virtual assistant to the crewman. It is designed to interact with other field components like the a rover, georadar and subsurface drilling instruments. Aouda.X weighs 45 kg, and is based upon a Hard-Upper-Torso system with ambient air ventilation. The outermost layer consists of a Panox/Kevlar tissue with aluminium coating; the pressure simulation is implemented via a modifiable exoskeleton able to simulate various pressure regimes for all major human joints including fingers. A biomedical and engineering telemetry package communicates via via W-Lan (including continuous video & audio, various temperatures, CO2, GPS, air pressure, humidity, acceleration,…), the man-machine interface is realized using speech recognition and accelerometer input devices in the gloves.

NASA Constellation Space Suit system

On August 2, 2006, NASA indicated plans to issue a Request for Proposal (RFP) for the design, development, certification, production, and sustaining engineering of the Constellation Space Suit to meet the needs of Project Constellation.[25] NASA foresees a single suit capable of supporting: survivability during launch, entry and abort; zero-gravity EVA; lunar surface EVA; and Mars surface EVA.

On June 11, 2008, NASA awarded a $745 million contract to Oceaneering International to create the new spacesuit.[26]

Suitports

A suitport is a theoretical alternative to an airlock, designed for use in hazardous environments and in human spaceflight, especially planetary surface exploration. In a suitport system, a rear-entry space suit is attached and sealed against the outside of a spacecraft, such that an astronaut can enter and seal up the suit, then go on EVA, without the need for an airlock or depressurizing the spacecraft cabin. Suitports require less mass and volume than airlocks, provide dust mitigation, and prevent cross-contamination of the inside and outside environments. Patents for suitport designs were filed in 1996 by Philip Culbertson Jr. of NASA's Ames Research Center and in 2003 by Joerg Boettcher, Stephen Ransom, and Frank Steinsiek.[27][28]

Astronaut Glove Challenge

There are certain difficulties in designing a dexterous spacesuit glove and there are limitations to the current designs. So to build a better glove the Centennial Astronaut Glove Challenge was created. Competitions have been held in 2007 and 2009, and another is planned. The 2009 contest required the glove to be covered with a micro-meteorite layer.

Spacesuits in fiction

For more details on this topic, see Spacesuits in fiction.

The oldest space fiction ignored the problems of traveling through a vacuum, and launched its heroes through space without any special protection. In the later 19th century, however, a more realistic brand of space fiction emerged, in which authors have tried to describe or depict 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

  1. ^ Astronaut is used here in the generic sense, to include both cosmonauts (Russian or Soviet) and astronauts (all other nationalities). The term taikonaut, while popularly used by English media, is not officially used in the English-language Chinese press.
  2. ^ The Four Most Important Equations In Clinical Practice By Lawrence Martin
  3. ^ http://www.damninteresting.com/outer-space-exposure
  4. ^ "Ask an Astrophysicist, Human Body in a Vacuum". NASA's Imagine the Universe. http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html. Retrieved 2008-12-14. 
  5. ^ "Outer Space Exposure". Damn Interesting. http://www.damninteresting.com/?p=741. Retrieved 2008-12-14. 
  6. ^ "Siegfried Hansen, space suit father; inventor was 90". New York Times. 24 July 2002. http://query.nytimes.com/gst/fullpage.html?res=9B02E7DD1238F937A15754C0A9649C8B63. Retrieved 9 February 2008. 
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  8. ^ US Spacesuits. Chichester, UK: Praxis Publishing Ltd.. 2006. ISBN 0-387-27919-9. http://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s. 
  9. ^ Astronautix
  10. ^ "为中华航天史册再添辉煌". 国防科工委新闻宣传中心. November 14, 2005. http://www.costind.gov.cn/n435777/n509091/n509092/24810.html. Retrieved July 22, 2008. 
  11. ^ "航天服充压实验". 雷霆万钧. September 19, 2005. http://tech.tom.com/1121/1122/2005919-251558.html. Retrieved July 24, 2008. 
  12. ^ "中国最早研制的航天服为桔黄色 重10千克". 雷霆万钧. September 16, 2005. http://tech.tom.com/1121/1122/2005916-250971.html. Retrieved July 24, 2008. 
  13. ^ "舱外航天服液冷服散热特性研究". 北京航空航天大学图书馆. March 1, 2000. http://lib.buaa.edu.cn/buaa/detail_degreethesis.jsp?channelid=75044&record=8443. Retrieved July 23, 2008. 
  14. ^ Oberg, James (2004-04-27). "Testimony of James Oberg: Senate Science, Technology, and Space Hearing: International Space Exploration Program" (in English). Washington D.C.. http://www.spaceref.com/news/viewsr.html?pid=12687. Retrieved 12 April 2011. 
  15. ^ Seedhouse, Erik (2010). The New Space Race: China Vs. USA. Chichester, UK: Praxis Publishing Ltd.. http://books.google.com/books?id=ey51Hy677mgC&pg=PA180&lpg=PA180&dq=Sokol-KV2+suit,+but+it+is+believed+to+be+a+Chinese-made+version+rather+than+an+actual+Russian+suit&source=bl&ots=F1iOX4jJYU&sig=h3YX7XWa5GYDd_WiF-lOzgRoi9c&hl=en&ei=BayvTKzOBYHGlQeThaDlDw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CCAQ6AEwAw. 
  16. ^ Space.com - China Ramps Up Human Spaceflight Efforts - Nov. 8th, 2004
  17. ^ "神七准备中俄产两套航天服 出舱者穿国产航天服". 搜狐. July 22, 2008. http://news.sohu.com/20080722/n258298683.shtml. Retrieved July 22, 2008. 
  18. ^ "China's astronaut outfitters design material for spacewalk suits". Xinhua. June 1, 2007. http://news.xinhuanet.com/english/2007-06/01/content_6182498.htm. Retrieved June 1, 2007. 
  19. ^ "Chinese astronauts begin training for spacewalk". People Daily Online. July 18, 2007. http://english.peopledaily.com.cn/90001/90781/6218810.html. Retrieved August 1, 2007. 
  20. ^ MARS Suit: MX-2
  21. ^ Jacobs, Shane; Akin, Dave, Braden, Jeffrey (July 2006). "System Overview and Operations of the MX-2 Neutral Buoyancy Space Suit Analogue". International Conference On Environmental Systems. Norfolk, Virginia. http://www.sae.org/technical/papers/2006-01-2287. Retrieved 12 June 2007. 
  22. ^ How Space Suits Work | HowStuffWorks
  23. ^ That's one small step toward Mars mission | The San Diego Union-Tribune
  24. ^ PolAres Spacesuit system
  25. ^ CONSTELLATION SPACE SUIT SYSTEM (CSSS), SOL NNJ06161022R
  26. ^ Get your first look at NASA’s next spacesuit, MSNBC
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  28. ^ Boettcher, Joerg; Stephen Ransom, Frank Steinsiek (17 July 2003). "Apparatus and method for putting on a protective suit — United States Patent 6959456". freepatentsonline.com. http://www.freepatentsonline.com/6959456.html. Retrieved 15 June 2006. 

US Spacesuits. Chichester, UK: Praxis Publishing Ltd.. 2006. ISBN 0-387-27919-9. http://books.google.com/books?id=cdO2-4szcdgC&source=gbs_navlinks_s. 

Russian Spacesuits. Chichester, UK: Praxis Publishing Ltd.. 2003. ISBN 1-85233-732-X. http://books.google.com/books?id=f7pZosHqkbEC&dq=S-901J+suit&source=gbs_navlinks_s. 

Young, Amanda (2009). Spacesuits: The Smithsonian National Air and Space Museum Collection. Brooklyn, NY, USA: House Cultural Entertainment, Inc.. ISBN 978-1-57687-498-1. http://books.google.com/books?id=D-sxPQAACAAJ&dq=Spacesuits&cd=2. 

Kozloski, Lillian D. (1994). U.S. Space Gear: Outfitting The Astronaut. Smithsonian Institution Press. ISBN 0874744598. http://books.google.com/books?id=v5JOPgAACAAJ&source=gbs_navlinks_s. 

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