Space suit

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 (around convert|19000|m|ft|abbr=on|disp=/), the atmosphere is so thin that pressurized suits are needed. Hazmat suits that superficially resemble space suits are sometimes used when dealing with biological hazards.

Spacesuit requirements

A space suit must perform several functions to allow its occupant to work safely and comfortably. 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. Lower pressure allows for greater mobility, but introduces the requirement of pre-breathing to avoid decompression sickness.
* Mobility. Movement is typically opposed by the pressure of the suit; mobility is achieved by careful joint design. See the "Theories of spacesuit design" section.
* Breathable oxygen. Circulation of cooled and purified oxygen is controlled by the Primary Life Support System.
* Temperature regulation. Unlike on Earth, where heat can be transferred by convection to the atmosphere, in space heat can only be lost by thermal radiation or by conduction to objects in physical contact with the space suit. Since the temperature on the outside of the suit varies greatly between sunlight and shadow, the suit is heavily insulated, and the temperature inside the suit is regulated by a Liquid Cooling Garment in contact with the astronaut's skin, as well as air temperature maintained by the Primary Life Support System.
* Shielding against ultraviolet radiation
* Limited shielding against particle radiation
* Protection against small micrometeoroids, provided by a Thermal Micrometeoroid Garment, which is the outermost layer of the suit
* A communication system
* Means to recharge and discharge gases and liquids
* Means to maneuver, dock, release, and/or tether onto spacecraft
* Means of collecting and containing solid and liquid waste (such as a Maximum Absorbency Garment)

Operating pressure

Generally, to supply enough oxygen for respiration, a spacesuit using pure oxygen must have a pressure of about convert|32.4|kPa|psi|sigfig=2|abbr=on, equal to the convert|20.7|kPa|psi|sigfig=2|abbr=on partial pressure of oxygen in the Earth's atmosphere at sea level, plus convert|5.3|kPa|Torr|sigfig=2|abbr=on CO₂ and convert|6.3|kPa|Torr|sigfig=2|abbr=on|link=on 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. [ [http://www.globalrph.com/martin_4_most2.htm The Four Most Important Equations In Clinical Practice By Lawrence Martin ] ] 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, but 32.4 kPa (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 of oxygen, which is about the alveolar oxygen partial pressure attained at an altitude of convert|1860|m|ft|abbr=on 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.

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 your 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 "V_i" and "V_f" 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 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 three theoretical approaches to suit design:

Hard-shell suits

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 joints, and often end up in odd positions that must be manipulated to regain mobility.

Mixed suits

Mixed 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.

kintight 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

* Evgeniy Chertanovskiy created his full-pressure suit or high-altitude "skafandr" (скафандр) in 1931. (скафандр also means "diving apparatus").
* Wiley Post experimented with a number of hard-shell designs for record-breaking flights.
* Russell Colley created the spacesuits worn by the Project Mercury astronauts, including fitting Alan B. Shepard Jr. for his historic ride as America's first man in space on May 5, 1961.

Russian suit models

* SK-1, the space suit of Yuri Gagarin, the first man in space
* Berkut (Беркут = "golden eagle"), the space suit of Alexei Leonov, the cosmonaut who first made a spacewalk
* Krechet (Кречет = "gyrfalcon") suit, designed for the cancelled Soviet manned moon landing
* Yastreb (Ястреб = "hawk") space suit for extra-vehicular activity, based on the Krechet
* Orlan (Орлан = "sea-eagle" or "bald eagle") suits for extra-vehicular activity
* Sokol (Сокол = "falcon") suits worn by Soyuz crew members during lift-off and re-entry
* Strizh (Стриж = "swift (bird)") spacesuit developed for pilots of the Buran space shuttle

American suit models

*In the early 1950s Siegfried Hansen and colleagues at Litton Industries designed and built a working hard-shell suit, which was used inside vacuum chambers and was the predecessor of hard space suits used in NASA missions. [cite news |title= Siegfried Hansen, space suit father; inventor was 90 |work= New York Times |url=http://query.nytimes.com/gst/fullpage.html?res=9B02E7DD1238F937A15754C0A9649C8B63 |date=2002-07-24 |accessdate=2008-02-09]
*Navy Mark V high-altitude/vacuum suit used for Project Mercury
*Gemini spacewalk suits, used for Project Gemini
*Manned Orbiting Laboratory MH-7 space suits
*Apollo/Skylab A7L EVA and moon suits. 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.
*Advance Crew Escape System Pressure Suit used on the Space Shuttle. The Advanced Crew Escape Suit or ACES suit, is a full pressure suit currently worn by all Space Shuttle crews for the ascent and entry portions of flight. The suit is a direct descendant of the U.S. Air Force high-altitude pressure suits worn by SR-71 Blackbird and U-2 spy plane pilots, X-15 and Gemini pilot-astronauts, and the Launch-Entry Suits worn by NASA astronauts starting on the STS-26 flight, the first flight after the Challenger Disaster
*Extravehicular Mobility Unit used on both the Space Shuttle and International Space Station. The EMU is an independent anthropomorphic system that provides environmental protection, mobility, life support, and communications for a Shuttle or ISS crew member to perform extra-vehicular activity (EVA) in earth orbit.

Chinese suit models

* Shuguang EVA space suit. First generation EVA space suit developed by China for the 1967 "Project 714" manned space program. Weighing about 10 kilograms, of orange colour, made of high-resistance multi-layers polyester fabric. The astronaut could use it inside the cabin and conduct EVA as well. [cite web|url=http://www.costind.gov.cn/n435777/n509091/n509092/24810.html|title =为中华航天史册再添辉煌|publisher= 国防科工委新闻宣传中心|date=November 14, 2005|accessdate=July 22|accessyear=2008] [cite web|url=http://tech.tom.com/1121/1122/2005919-251558.html|title =航天服充压实验|publisher= 雷霆万钧|date=September 19, 2005|accessdate=July 24|accessyear=2008] [cite web|url=http://tech.tom.com/1121/1122/2005916-250971.html|title =中国最早研制的航天服为桔黄色 重10千克|publisher= 雷霆万钧|date=September 16, 2005|accessdate=July 24|accessyear=2008]

* Project 863 EVA space suit. Cancelled project of second generation Chinese EVA space suit. [cite web|url=http://lib.buaa.edu.cn/buaa/detail_degreethesis.jsp?channelid=75044&record=8443|title =舱外航天服液冷服散热特性研究|publisher= 北京航空航天大学图书馆|date=March 1, 2000|accessdate=July 23|accessyear=2008]

* Shenzhou 5 space suit. The suit worn by Yang Liwei on "Shenzhou 5", the first manned Chinese space flight, closely resembles a Sokol-KV2 suit, but it is believed to be a Chinese-made version rather than an actual Russian suit.

* Shenzhou 6 space suit. Pictures show that the suits worn by Fei Junlong and Nie Haisheng on "Shenzhou 6" differ in detail from the earlier suit, they are also reported to be lighter.

* Haiying EVA space suit. The imported Russian Orlan-M EVA suit is called "Haiying" (海鹰号航天服).

* Feitian EVA space suit (飞天号航天服). New generation indigenously developed Chinese-made EVA space suit to be used for the Shenzhou 7 mission. [cite web|url=http://news.sohu.com/20080722/n258298683.shtml|title =神七准备中俄产两套航天服 出舱者穿国产航天服|publisher= 搜狐|date=July 22, 2008|accessdate=July 22|accessyear=2008] New space suits for the extravehicular activity (舱外航天服) will be used, notably made with intelligent materials (“聪明材”). [http://scitech.people.com.cn/GB/4650572.html] . The suit is designed for a spacewalk mission of up to seven hours. [cite web|url=http://news.xinhuanet.com/english/2007-06/01/content_6182498.htm|title =China's astronaut outfitters design material for spacewalk suits|publisher= Xinhua|date=June 1, 2007|accessdate=June 1|accessyear=2007] The astronauts had been training in the out-of-capsule space suits since July 2007, and movements are seriously restricted in the suits, with a mass of more than 110 kilograms each. [cite web|url=http://english.peopledaily.com.cn/90001/90781/6218810.html|title =Chinese astronauts begin training for spacewalk|publisher= People Daily Online|date=July 18, 2007|accessdate=August 1|accessyear=2007]

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 (convert|57|kPa|psi|abbr=on|disp=/), 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. [ [http://ssl.umd.edu/projects/MARSsuit/index.shtml MARS Suit: MX-2 ] ] 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 convert|120|lb|abbr=on. [cite conference
first = Shane
last = Jacobs
coauthors = Akin, Dave, Braden, Jeffrey
title = System Overview and Operations of the MX-2 Neutral Buoyancy Space Suit Analogue
booktitle = International Conference On Environmental Systems
date = July 2006
location = Norfolk, Virginia
url = http://www.sae.org/technical/papers/2006-01-2287
accessdate = 2007-06-12 ]

North Dakota suit

Beginning 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 Fact|date=July 2007 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. [ [http://www.signonsandiego.com/uniontrib/20060507/news_1n7suit.html That's one small step toward Mars mission | The San Diego Union-Tribune ] ] 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 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. [ [http://prod.nais.nasa.gov/cgi-bin/eps/synopsis.cgi?acqid=121486 CONSTELLATION SPACE SUIT SYSTEM (CSSS), SOL NNJ06161022R ] ] 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. [ [http://www.msnbc.msn.com/id/25130313 Get your first look at NASA’s next spacesuit] , MSNBC]

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.cite web
last = Culbertson
first = Philip, Jr.
title = Suitlock docking mechanism — United States Patent 5697108
publisher = freepatentsonline.com
date = 1996-09-30
url = http://www.freepatentsonline.com/5697108.html
accessdate = 2006-06-15 ] [cite web
last = Boettcher
first = Joerg
coauthors = Stephen Ransom, Frank Steinsiek
title = Apparatus and method for putting on a protective suit — United States Patent 6959456
publisher = freepatentsonline.com
date = 2003-07-17
url = http://www.freepatentsonline.com/6959456.html
accessdate = 2006-06-15 ]

pacesuits in fiction

For as long as there has been fiction set in space, 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.

ee also

* Pressure Suit
* Sokol space suit
* Orlan space suit
* Space activity suit
* Extra-vehicular activity
* Manned maneuvering unit
* Human adaptation to space
* List of spacewalks
* List of Mir spacewalks
* List of ISS spacewalks
* List of spacewalks and moonwalks
* List of cumulative spacewalk records

References

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External links

* [http://aesp.nasa.okstate.edu/fieldguide/pages/spacesuit/index.html A Field Guide to American Spacecraft] : A list compiled by Lee Sledge and James H. Gerard of American space suits and the museum locations where they are displayed.
* [http://www.astronautix.com/craftfam/spasuits.htm Astronautix.com complete list of Space Suits]
* [http://www.zvezda-npp.ru/english/04.htm Russian Space Suits]
* [http://epizodsspace.testpilot.ru/bibl/n_i_j/1978/6/skaf.html Design of Soviet/Russian Space Suits]
* [http://www.jsc.nasa.gov/history/hsf_history.htm NASA JSC Oral History Project] : See link near page end to "Walking to Olympus: An EVA Chronology" PDF document.
* [http://web.archive.org/web/20010716093905/http://spaceboy.nasda.go.jp/note/yujin/e/yuj101_eva_e.html NASDA Online Space Notes]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730064704_1973064704.pdf Apollo Extravehicular mobility unit. Volume 1: System description - 1971 (PDF document)]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730064705_1973064705.pdf Apollo Extravehicular mobility unit. Volume 2: Operational procedures - 1971 (PDF document)]
* [http://trs.nis.nasa.gov/archive/00000173/01/tmx64855.pdf Skylab Extravehicular Activity Development Report - 1974 (PDF document)]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900001621_1990001621.pdf Analysis of the Space Shuttle Extravehicular Mobility Unit - 1986 (PDF document)]
* [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19940017339_1994017339.pdf NASA Space Shuttle EVA tools and equipment reference book - 1993 (PDF document)]
* [http://www.hq.nasa.gov/alsj/apollo.engin.html Engineering Aspects of Apollo] : Section on the Apollo space suit and portable life support system.