Spacewalk: Wikis

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Mike Fossum works on the Kibo Module (JPM) during the second spacewalk of STS-124.

Extra-vehicular activity (EVA) is work done by an astronaut away from the Earth, and outside of a spacecraft. The term most commonly applies to an EVA made outside a craft orbiting Earth (a spacewalk), but also applies to an EVA made on the surface of the Moon (a moonwalk). In the later lunar landing missions (Apollo 15, 16, and 17) the command module pilot (CMP) did an EVA to retrieve film canisters on the return trip; he was assisted by the lunar module pilot (LMP) who remained at the open CM hatch. These trans-Earth EVAs were the only spacewalks ever conducted in deep space.

Due to the different designs of the early spacecraft, the American and Soviet space programs also define an EVA differently. Russians define an EVA as occurring when a cosmonaut is in a vacuum. An American EVA begins when the astronaut switches the Extravehicular Mobility Unit (EMU) to battery power. A "Stand-up" EVA (SEVA) is where the astronaut does not fully exit a spacecraft, but is completely reliant on the spacesuit for environmental support.[1] Its name derives from the astronaut "standing up" in the open hatch, usually to film or assist a spacewalking astronaut.

EVAs may be either tethered (the astronaut is connected to the spacecraft, oxygen can be supplied through a tube, no propulsion is needed to return to the spacecraft) or untethered. When the tether performs life support functions such as providing oxygen, it is called an umbilical. Untethered spacewalks were only performed on three missions in 1984 using the Manned Maneuvering Unit (MMU), and on a flight test in 1994 of the Simplified Aid for EVA Rescue (SAFER). A SAFER is a safety device worn on tethered U.S. EVAs, since the capability of returning to the spacecraft is essential.

As of 2009, Russia, the United States, and China are the only countries with a demonstrated capability to conduct an EVA.

Contents

Camp out

For EVAs from the International Space Station, NASA now routinely employs a camp out procedure to reduce the risk of decompression sickness.[2] This was first tested by the Expedition 12 crew. During a camp out, astronauts sleep overnight prior to an EVA in the airlock, and lower the air pressure to 10.2 psi (70 kPa), compared to the normal station pressure of 14.7 psi (101 kPa).[2] Spending a night at the lower air pressure helps flush nitrogen from the body, thereby preventing "the bends".[3][4]

EVA milestones

Capture of Intelsat VI in 1992 on STS-49. This hand-capture of a satellite is the only EVA to date to be performed by three astronauts.
Stephen Robinson riding the robotic arm during STS-114, doing a first in-flight repair of the Space Shuttle.(Landmass in the backdrop is the Bari region of Somalia).
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Capability milestones

Personal cumulative duration records


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National, ethnic and gender firsts

International Space Station assembly EVA made during the STS-116 mission. Robert Curbeam (with red stripes) together with Christer Fuglesang over Cook Strait, New Zealand.
  • The first EVA by an American was made on June 3, 1965 by Edward White during the Gemini 4 mission.
  • The first EVA by a non-Soviet, non-American was made on December 9, 1988 by Jean-Loup Chrétien of France during a three-week stay on the Mir space station.
  • The first EVA by a Briton was on February 9, 1995 by Michael Foale (who carries dual British-American citizenship).
  • The first EVA by an African-American was on February 9, 1995 by Bernard A. Harris, Jr..
  • The first EVA by a Australian-born person was on March 13, 2001 by Andy Thomas (although he is a naturalized US citizen).
  • The first EVA by a Canadian was made on April 22, 2001 by Chris Hadfield. During his spacewalk, Hadfield installed the Canadarm2 onto the International Space Station.
  • The first EVA by a Chinese astronaut was made on September 27, 2008 by Zhai Zhigang during Shenzhou 7 mission. The spacewalk, using a Feitian space suit, made China the third country to independently carry out an EVA.

Designations

NASA "spacewalkers" are desingated as EV-1, EV-2, EV-3 and EV-4 (assiged to Mission specialists for each mission, if applicable).[7][8]

See also

References

External links


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