The Extravehicular Mobility Unit (EMU) is an independent anthropomorphic

spacesuit 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, ...

that provides environmental protection, mobility, life support, and communications for astronauts performing extravehicular activity (EVA) in

Earth orbit Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi) in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes days (1 sidereal year), during which time E ...

. Introduced in 1981, it is a two-piece semi-rigid suit, and is currently one of two types of EVA spacesuits used by crew members on the

International Space Station The International Space Station (ISS) is the largest Modular design, modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos ( ...

(ISS), the other being the Russian Orlan space suit. It was used by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...

astronauts prior to the end of the Shuttle program in

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Suit components

The EMU, like the Apollo/Skylab A7L spacesuit, was the result of 21 years of research and development. It consists of a Hard Upper Torso (HUT) assembly, a Primary Life Support System (PLSS) which incorporates the life support and electrical systems, arm sections, gloves, an Apollo-style "bubble" helmet, the Extravehicular Visor Assembly (EVVA), and a soft Lower Torso Assembly (LTA), incorporating the Body Seal Closure (BSC), waist bearing, brief, legs, and boots. Prior to donning the pressure garment, the crew member puts on a Maximum Absorbency Garment (MAG) (basically a modified

incontinence Incontinence or Incontinent may refer to: *Fecal incontinence, the involuntary excretion of bowel contents * Urinary incontinence, the involuntary excretion of urine * Lack of moderation or self-control, especially related to sexual desire - see ...

diaper – Urine Collection Devices (UCDs) are no longer used), and possibly a Thermal Control Undergarment ( long johns). The final item donned before putting on the pressure suit is the Liquid Cooling and Ventilation Garment (LCVG), which incorporates clear plastic tubing through which chilled liquid

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

flows for body temperature control, as well as ventilation tubes for waste gas removal. After donning the LCVG, the astronaut then puts on the LTA, before entering the airlock. The astronaut then dons the HUT, connects the LCVG umbilical to the umbilical in the HUT, and then locks the two parts of the suit together using the Body Seal Closure. Once the suit is turned on and checked out, the astronaut dons a "

Snoopy cap A Snoopy cap, or communication cap, is a part of a space suit worn by American astronauts on the head and incorporating an audio headset for communication. The cap is nicknamed after the Peanuts character, whom its black and white paneling resemb ...

", a brown and white fabric communications cap dating back to the

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days, which incorporates a pair of earphones and microphones, allowing the EVA astronaut to communicate with both the crew members in the orbiter and ground controllers in

Houston Houston (; ) is the most populous city in Texas, the most populous city in the Southern United States, the fourth-most populous city in the United States, and the sixth-most populous city in North America, with a population of 2,304,580 ...

. After donning the "Snoopy cap", the gloves and helmet are then locked on, pressurizing the suit. The suit's regulator and fans activate when the servicing umbilicals are removed and the suit reaches an internal pressure of . A typical EMU can support an astronaut for 8.5 hours, including 30 minutes of reserves in the case of primary life support failure. To perform an EVA from the shuttle, the cabin pressure was reduced from for 24 hours, after which an astronaut had to pre-breathe for 45 minutes. For EVAs on board the ISS, the astronaut must pre-breathe for about four hours.

Specifications

Baseline EMU

*Manufacturer: ILC Dover (suit) and

Collins Aerospace Collins Aerospace is an American technology corporation that is one of the world's largest suppliers of aerospace and defense products. Headquartered in Charlotte, North Carolina, it is a subsidiary of Raytheon Technologies. History On N ...

(primary life support systems) *Missions:

STS-6 STS-6 was the sixth NASA Space Shuttle mission and the maiden flight of the . Launched from Kennedy Space Center on April 4, 1983, the mission deployed the first Tracking and Data Relay Satellite, TDRS-1, into orbit, before landing at Edwar ...

(1983) to STS-110 (2002) *Function:

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

al extra-vehicular activity *Operating pressure: 4.5 psi (29.6 kPa) *EVA suit weight: 109 lb (49.4 kg) *Total shuttle EVA suit weight: 254 lb (115 kg) *Primary life support: 8 hours (480 minutes) *Backup life support: 30 minutes

Enhanced EMU

*Manufacturer: ILC Dover (suit), Collins Aerospace (primary life support systems) and NASA (SAFER) *Missions: 1998 to present *Function: orbital extra-vehicular activity *Operating pressure: 4.5 psi (29.6 kPa) *EVA suit weight: 122 lb (55.3 kg) *Total shuttle EVA suit weight: 275 lb (124.7 kg) *Total ISS EVA suit weight: 319 lb (145 kg) *Primary life support: 8 hours (480 minutes) *Backup life support: 30 minutes

Manufacturer

The EMU hardware and accessories (PLSS, helmet, communications cap, and locking rings for the helmet and gloves), is manufactured by Hamilton Standard (now the Hamilton Sundstrand division of

) out of

Windsor Locks, Connecticut Windsor Locks is a town in Hartford County, Connecticut, United States. As of the 2020 census, its population was 12,613. It is the site of Bradley International Airport, which serves the Greater Hartford-Springfield region and occupies approxi ...

, while the suit's soft components (the arms of the HUT and the entire LTU) are produced by ILC Dover (a former division of

Playtex Playtex is an American brand name for undergarments, baby products, gloves, feminine hygiene products, and sunscreen. The brand began in 1947 when International Latex Corporation (ILC) created a division named Playtex to produce and sell latex p ...

) out of Frederica, Delaware. The two companies, who were rivals during the early days of Apollo for the contract to build the "Block II" (moonwalking) space suit, teamed up in 1974 against the

David Clark Company David Clark Company, Inc. is an American manufacturing company. DCC designs and manufactures a wide variety of aerospace and industrial protective equipment, including pressure-space suit systems, anti-G suits, headsets, and several medical/safet ...

and

Garrett AiResearch Garrett AiResearch was a manufacturer of turboprop engines and turbochargers, and a pioneer in numerous aerospace technologies. It was previously known as Aircraft Tool and Supply Company, Garrett Supply Company, AiResearch Manufacturing Compa ...

for the EMU development and construction. During Apollo, the ILC Dover-produced A7L used the life support backpack, helmet, and locking rings supplied by Hamilton Standard, but originally, ILC Dover was to just supply the arms and legs of the suit, a similar process that is still going on today. In total 18 EMU suits with PLSS were manufactured; 5 were lost during missions, 1 was lost in ground test, and, as of 2017, 11 remain complete and functional.

History

Upon receiving the contract to build the EMU in 1974, Hamilton Standard and ILC Dover delivered the first EMU units to NASA in 1982. During the research and development phase (1975–1980), a suit being tested caught fire, injuring a technician and forcing a redesign on the regulator and circulation fan. On STS-4 in July 1982, the astronauts practiced donning and doffing the suit in the Shuttle's airlock. The first Shuttle EVA was to occur on STS-5, but an electrical failure on the circulation fan forced the EVA to be cancelled. The first EVA of the new EMU finally occurred on

when Story Musgrave and Donald Peterson went out in the payload bay of the Space Shuttle ''Challenger'' and tested techniques to lower the launch cradle of a solid-fuel upper stage used to boost a

Tracking and Data Relay Satellite A tracking and data relay satellite (TDRS) is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System (TDRSS) used by NASA and other United States government agencies for communications to and fr ...

(TDRS-A) into a geostationary orbit. Other EVAs followed on the Shuttle, notably those on

STS-41-B STS-41-B was the tenth NASA Space Shuttle mission and the fourth flight of the . It launched on 3 February 1984, and landed on 11 February 1984 after deploying two communications satellites. It was also notable for including the first untethere ...

(the first

Manned Maneuvering Unit The Manned Maneuvering Unit (MMU) is an astronaut propulsion unit that was used by NASA on three Space Shuttle missions in 1984. The MMU allowed the astronauts to perform untethered extravehicular spacewalks at a distance from the shuttle. ...

flight),

STS-41-C STS-41-C (formerly STS-13) was NASA's eleventh Space Shuttle mission, and the fifth mission of Space Shuttle ''Challenger''. The launch, which took place on April 6, 1984, marked the first direct ascent trajectory for a Space Shuttle mission. ...

(the Solar Max repair mission),

STS-41-G STS-41-G (formerly STS-17) was the 13th flight of NASA's Space Shuttle program and the sixth flight of Space Shuttle ''Challenger''. ''Challenger'' launched on October 5, 1984, and conducted the second shuttle landing at Kennedy Space Center o ...

(the first American EVA involving a woman), and STS-51-A (where two stranded satellites were retrieved and returned to Earth), but the majority of EMU uses occurred on the servicing missions of the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

. For those flights, two sets of EVA astronauts would venture out of the orbiter, thus requiring NASA to fly four sets of suits (along with repair parts). 41 EVAs using EMUs had been conducted out of the Space Shuttle airlock prior to the start of ISS assembly in November 1998. With the building of the ISS, Hamilton Sundstrand and ILC Dover refined the existing Shuttle EMU by making the suit modular. This allowed an EMU to be left on the ISS for up to two years and resized on-orbit to fit various crew members. The ISS EMUs also have increased battery capacity, the

Simplified Aid For EVA Rescue Simplified Aid For EVA Rescue (SAFER) is a small, self-contained, propulsive backpack system (jet pack) worn during spacewalks, to be used in case of emergency only. If an untethered astronaut were to lose physical contact with the vessel, it wou ...

(SAFER), improved cameras and radios, and a new caution and warning system. Another feature incorporated into the ISS suits is an additional battery to power heaters built into the glove, allowing astronauts to keep their hands warm during nighttime passages on each 95-minute orbit. Currently, the ISS EMUs and the Russian Orlan suits are used by crews of all nationalities on the International Space Station. The two EMUs are stored within the Quest Joint Airlock.

Future use and replacement

, NASA plans to use Exploration Extravehicular Mobility Unit (xEMU) system during Artemis program, derived from the spacesuit technologies used in the past. On June 1st, 2022, NASA announced it had selected Axiom Space and

to develop and provide astronauts with next generation spacesuit and spacewalk systems to work outside the International Space Station, explore the lunar surface on Artemis missions, and prepare for human missions to Mars.

Gallery

Image:NASA EMU without visor.jpg , Image:STS51 EVA cropped.jpg ,

Notes

References

External links

Learn About Spacesuits NASA

ILC Spacesuits & Related Products

NASA EMU PDF

Donning a Spacesuit

{{Use American English, date=January 2014 American spacesuits Extravehicular activity