Extra-vehicular activity
From Wikipedia, the free encyclopedia
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 the command module pilot did an EVA to retrieve film canisters on the return trip.
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 astronaut EVA begins when the astronaut switches the Extravehicular Mobility Unit (EMU) to battery power. The term stand-up EVA (SEVA) is used for being partly outside.
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. For untethered EVAs during space flight, capability of returning to the spacecraft is essential; see Manned Maneuvering Unit (MMU) and Simplified Aid for EVA Rescue (SAFER).
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[edit] EVA milestones
- The first EVA was carried out by Aleksei Leonov on March 18, 1965 from the Voskhod 2 spacecraft.
- The first EVA by an American astronaut was made on June 3, 1965 by Edward White during the Gemini 4 mission.
- The first EVA that was a moonwalk rather than a spacewalk was made by American astronaut Neil Armstrong on July 20 1969 when the Apollo 11 Lunar Module Eagle landed on the Moon. He was joined by crewmate Buzz Aldrin, and their EVA lasted 2 hours and 32 minutes.
- The first untethered spacewalk was by American astronaut Bruce McCandless II on February 7 1984, during Challenger mission STS-41-B. He was subsequently joined by astronaut Robert L. Stewart during the 5 hour 55 minute spacewalk.
- The first woman to perform an EVA was Cosmonaut Svetlana Savitskaya on July 25 1984 while aboard the Salyut 7 space station.
- The first American woman to make an EVA was Kathryn D. Sullivan, who stepped into space on October 11 1984 during Space Shuttle Challenger mission STS-41-G.
- The first (and only) three-person EVA was performed on May 13, 1992, as the third EVA of STS-49, the maiden flight of Endeavour.[1] Pierre Thuot, Richard Hieb, and Thomas Akers conducted the EVA to capture and repair a non-functional Intelsat VI-F3 satellite, and equipped the satellite with a new motor, that after release, moved it into its planned geosynchronous orbit.
- The first EVA by a non-Soviet, non-American astronaut was made on December 9 1988 by Jean-Loup Chrétien of France during a three-week stay on the Mir space station.
- On February 9 1995, Bernard A. Harris, Jr. and Michael Foale became the first African American and the first Briton, respectively, to perform an EVA.
- The first EVA to perform an in-flight repair of the Space Shuttle was by American astronaut Steve Robinson on August 3 2005, during "Return to Flight" mission STS-114. Robinson was sent to remove two protruding gap fillers on the Space Shuttle Discovery's heat shield, after engineers determined they might cause damage to the shuttle upon re-entry. Robinson successfully removed the loose material while the Discovery was docked to the International Space Station.
- The longest EVA was 8 hours and 56 minutes, performed by Susan J. Helms on March 11, 2001.[2]
- Anatoly Solovyev, with 16 spacewalks, totaling 77 hours, 41 minutes EVA, holds the record for most spacewalks (16), and total duration (82 hours, 22 minutes).[2]
- Captain Michael Lopez-Alegria holds the all time American record for number of EVA's (10), and for total EVA duration (67 hours and 40 minutes).[2]
[edit] EVA hazards
An EVA is dangerous for a number of different reasons. The primary one is collision with space debris. Orbital velocity at 300 km above the Earth (typical for a Space Shuttle mission) is 7.7 km/s. This is 10 times the speed of a bullet, so the kinetic energy of a small particle with a mass 1/100th is that of a bullet (e.g. a fleck of paint or a grain of sand) is equal to that of a bullet. Every space mission creates more orbiting debris, so this problem will continue to worsen (see also Kessler Syndrome).
Another reason for danger is that external environments in space are harder to simulate before the mission, though approximate simulations can be achieved at facilities like NASA's Neutral Buoyancy Laboratory. Space walks are avoided for routine tasks because of their danger. As a result the EVAs are often planned late in the project development when problems are discovered, or sometimes even during an operational mission. The exceptional danger involved in EVAs inevitably leads to emotional pressures on astronauts.
Other possible problems include a space walker becoming separated from his or her craft or suffering a spacesuit puncture which would depressurize the suit, causing anoxia and rapid death if the space walker is not brought into a pressurized spacecraft quickly.
One astronaut has suffered a spacesuit puncture. During STS-37, a small rod punctured the glove of one of the astronauts (the name is undisclosed, but it was either Jerry L. Ross or Jay Apt). However, the puncturing object held in place, resulting in no detectable depressurization. In fact, the puncture was not noticed until after the space walkers were safely back inside Atlantis.[3]
Aleksei Leonov's EVA did not pass smoothly, although this was not reported at the time. During the EVA, Leonov's suit had become overinflated to the point he could no longer re-enter and seal the door of the airlock. Because he was breathing pure oxygen, he was able to reduce his suit pressure to under 4 psi (28 kPa) and, with much effort, climb back inside.[4]
For EVAs from ISS NASA now routinely employs a camp out procedure to reduce the risk of decompression sickness. This was first tested by the Expedition 12 crew. During a camp out, astronauts shut themselves in the airlock and lower the air pressure to 10.2 psi (70 kPa). The station is kept at 14.7 psi (101 kPa); spending a night at the lower air pressure helps flush nitrogen from the body, thereby preventing "the bends."[5][6]
As of 2007, no catastrophic incident has ever occurred during an extra-vehicular activity, and no astronaut or cosmonaut has ever died during one. However, given the considerable hazards inherent in EVAs, and the resultant risk to astronauts, some scientists are working to develop tele-operated robots for outside construction work, to potentially eliminate or reduce the need for human EVAs.
[edit] 2007 EVAs
This is a list of EVAs conducted or scheduled to be conducted in 2007.
- See also: List of spacewalks and moonwalks and List of ISS spacewalks
| Spacewalk Start time | End time | Duration | Spacewalker | Origin | Mission/ Function | Outcome | Remarks |
|---|---|---|---|---|---|---|---|
| January 31, 15:14 UTC | January 31, 23:09 UTC | 7 hours, 55 minutes | Michael Lopez-Alegria | | Second Expedition 14 EVA - reroute ISS cooling lines.[7] | | |
| Sunita Williams | |||||||
| February 4, 13:38 UTC | February 4, 20:49 UTC | 7 hours, 11 minutes | Michael Lopez-Alegria | | Third Expedition 14 EVA - reroute ISS cooling lines.[8] | | precautionary decontamination conducted at end due to ammonia flakes seen earlier. |
| Sunita Williams | |||||||
| February 8, 13:26 UTC | February 8, 20:06 UTC | 6 hours, 40 minutes | Michael Lopez-Alegria | | Fourth Expedition 14 EVA - jettison shrouds; prep for cargo carriers; connect cables for SSPTS[9] | | Fourth EVA for Williams is the most for any woman; Lopez-Alegria sets U.S. record for cumulative EVA time |
| Sunita Williams | |||||||
| February 22, 10:27 UTC | February 22, 16:45 UTC | 6 hours, 18 minutes | Michael Lopez-Alegria | | Fifth Expedition 14 EVA - Progress antenna retraction; photography of Russian satellite antenna; Russian experiment changeout; Automated Transfer Vehicle (ATV) antenna photography/inspection; German experiment photography; Strela crane photography/inspection.[10] | | |
| Mikhail Tyurin | |||||||
| May 30, 19:05 UTC | May 31, 00:30 UTC | 5 hours, 25 minutes | Oleg Kotov | | First Expedition 15 EVA - install protective panels to shield ISS from space debris.[11] | | started 45 minutes late due to communications issues. |
| Fyodor Yurchikhin | |||||||
| June 6, 14:23 UTC | June 6, 20:00 UTC | 5 hours, 37 minutes | Oleg Kotov | | Second Expedition 15 EVA - install Biorisk experiment; install ethernet cable; install more debris panels.[12] | | 15 minutes faster than planned |
| Fyodor Yurchikhin | |||||||
| June 11, 20:02 UTC | June 12, 02:17 UTC | 6 hours, 15 minutes | James F. Reilly | | First STS-117 EVA - connect S3/S4 bolts, cables and connectors; prepare for deployment solar arrays.[13] | | started late due to loss of CMG attitude control |
| John D. Olivas | |||||||
| June 13, 18:28 UTC | June 14, 01:44 UTC | 7 hours, 16 minutes | Patrick G. Forrester | | Second STS-117 EVA - assist with P6 solar array retraction; prep SARJ for rotation.[14] | | SARJ launch restraints still in place |
| Steven Swanson | |||||||
| June 15, 17:24 UTC | June 16, 01:22 UTC | 7 hours, 58 minutes | James F. Reilly | | Third STS-117 EVA - OMS blanket repair; install H2 vent valve for OGS; P-6 SAW retraction.[15] | | |
| John D. Olivas | |||||||
| June 17, 16:25 UTC | June 17, 22:54 UTC | 6 hours, 29 minutes | Patrick G. Forrester | | Fourth STS-117 EVA - SARJ activation; cable install on Unity; GPS antenna removal; debris shield install on Destiny | | |
| Steven Swanson | |||||||
| July 23, 10:25 UTC | July 23, 18:06 UTC | 7 hours, 41 minutes | Clayton Anderson | | Third Expedition 15 EVA (aka EVA-9) - replace component for mobile transporter redundant power; jettison ammonia tank and flight support equipment; clean CBM on nadir Unity port.[16][17] | | |
| Fyodor Yurchikhin | |||||||
| August 11, 16:28 UTC | August 11, 22:45 UTC | 6 hours, 17 minutes | Richard Mastracchio | | First STS-118 EVA - S5 installation; P6 Radiator retraction and cinch. | | |
| Dafydd Williams | |||||||
| August 13, 15:32 UTC | August 13, 22:00 UTC | 6 hours, 28 minutes | Richard Mastracchio | | Second STS-118 EVA - Failed CMG removal; new CMG installation. | | |
| Dafydd Williams | |||||||
| August 15, 14:37 UTC | August 15, 20:05 UTC | 5 hours, 28 minutes | Richard Mastracchio | | Third STS-118 EVA - SASA relocation; CETA Cart relocation; P6 Transponder retrieval. S-band antenna relocation from P6 to P1. | | EVA ended early due to possible hole in Mastracchio's glove. All but one activity completed. |
| Clayton Anderson | |||||||
| August 18, 14:17 UTC | August 18, 19:19 UTC | 5 hours, 02 minutes | Dafydd Williams | | Fourth STS-118 EVA - OBSS Boom Stand Installation; MISSE retrieval; EWIS Antenna Installation; Secured Z1 gimbal locks | | EVA plan altered due to Hurricane Dean (2007), planned shorter EVA for early undocking. |
| Clayton Anderson | |||||||
| October 26, 10:02 UTC | October 26, 16:16 UTC | 6 hours, 14 minutes | Scott E. Parazynski | | First STS-120 EVA - Harmony (Node 2) installation preparation, S-Band Antenna Support Assembly (SASA) retrieval, P6/Z1 fluid line disconnections, P6 aft radiator shroud installations.[18] | | Precautionary decontamination conducted at end of EVA. |
| Douglas H. Wheelock | |||||||
| October 28, 09:32 UTC | October 28, 16:05 UTC | 6 hours, 33 minutes | Parazynski | | Second STS-120 EVA. Z1 to P6 umbilical disconnections, P6 detach from Z1, S1 radiator configuration, Node 2 handrail installations. S4 starboard SARJ inspection. | | Metallic looking particulates noted in the starboard SARJ by Tani. Samples collected. |
| Daniel M. Tani | |||||||
| October 30, 08:45 UTC | October 30, 15:53 UTC | 7 hours, 08 minutes | Parazynski | | Third STS-120 EVA. P6 to P5 attachment. P6/P5 umbilical connections, S1 configure post-redeploy, port SARJ inspection. | | |
| Wheelock | |||||||
| November 3, 10:03 UTC | November 3, 17:22 UTC | 7 hours, 19 minutes | Parazynski | | Fourth STS-120 EVA. Inspection and repair of P6 Solar Array. | | |
| Wheelock | |||||||
| November 9, 09:54 UTC | November 9, 16:49 UTC | 6 hours, 55 minutes | Peggy Whitson | | First Expedition 16 EVA. SSPTS cable disconnect and stowage, PMA2 umbilical stowage, Node 2 avionics umbilical temp stowed. | | |
| Yuri Malenchenko | |||||||
| November 20, 10:10 UTC | November 20, 17:26 UTC | 7 hours, 16 minutes | Whitson | | External configuration of PMA-2 and Harmony: Fluid, electrical, and data line hookups, avionics line hookup, heater cable hookups, Fluid tray relocation. | | Precautionary decontamination conducted at the end of EVA due to ammonia flakes seen during the spacewalk. |
| Daniel M. Tani | |||||||
| November 24, 09:50 UTC | November 24, 16:54 UTC | 7 hours, 04 minutes | Whitson | | Third Expedition 16 EVA. Completion of fluid, electrical, and data line hookups for PMA-2 and Harmony. Loop B Fluid Tray connection to port side of Destiny. Photographic analysis of starboard Solar Alpha Rotary Joint to assist with troubleshooting on the ground. | | |
| Tani | |||||||
| December 18, 09:50 UTC | December 18, 16:46 | 6 hours, 56 minutes | Whitson | | Fourth Expedition 16 EVA. Inspection of the S4 starboard Solar Alpha Rotary Joint (SARJ), and a Beta Gimbal Assembly (BGA). The EVA is the 100th in support of building the International Space Station.[19] | | Records set: 100th EVA in support of ISS assembly and maintenance. Whitson became the female astronaut with most EVAs (five) and with the most cumulative EVA time, 32 hours, 36 minutes, surpassing Sunita Williams.[20] |
| Tani |
Planned EVAs:
| Spacewalk Start time | End time | Duration | Spacewalker | Spacecraft or Space station | Mission/ Function | Outcome | Remarks |
|---|
[edit] See also
- Space suit
- Orlan space suit
- Sokol space suit
- Manned Maneuvering Unit
- List of spacewalks
- List of Mir spacewalks
- List of ISS spacewalks
- List of spacewalks and moonwalks
- List of cumulative spacewalk records
[edit] References
- ^ NASA (2001). STS-49. NASA. Retrieved on December 7, 2007.
- ^ a b c William Harwood (2007). ISS EVA Statistics. CBS News. Retrieved on November 8, 2007.
- ^ Landis, Geoffrey. "Human Exposure to Vacuum", Geoffrey A. Landis personal website, 2000-06. Retrieved on 2007-08-20.
- ^ Encyclopedia Astronautica (2007). Berkut Chronology. Encyclopedia Astronautica. Retrieved on November 8, 2007.
- ^ NASA. International Space Station Status Report #06-7. NASA. Retrieved on 2006-02-17.
- ^ NASA. Pass the S'mores Please! Station Crew 'Camps Out'. NASA. Retrieved on 2006-04-01.
- ^ NASA. Station Crew Members Wind Up Successful Spacewalk. NASA. Retrieved on 2007-01-31.
- ^ NASA. Crew Completes Scheduled Spacewalk Tasks, and More. NASA. Retrieved on 2007-02-04.
- ^ NASA. International Space Station Status Report #07-08. NASA. Retrieved on 2007-02-08.
- ^ NASA (2007-02-22). accessdate = 2007-08-18 Spacewalkers Successfully Retract Progress Antenna. NASA.
- ^ NASA. Spacewalk Complete, Debris Panels Installed. NASA. Retrieved on 2007-05-31.
- ^ NASA. Cosmonauts Wrap Up Debris-Panel Spacewalk. NASA. Retrieved on 2007-06-06.
- ^ NASA. STS-117 MCC Status Report #07. NASA. Retrieved on 2007-06-12.
- ^ NASA. STS-117 MCC Status Report #11. NASA. Retrieved on 2007-06-14.
- ^ NASA. STS-117 MCC Status Report #15. NASA. Retrieved on 2007-06-16.
- ^ William Harwood - CBS News. Shuttle Endeavour readied for rollout to launch pad. Spaceflight Now. Retrieved on 2007-07-23.
- ^ NASA. Station Crew Winds Up Ammonia Reservoir Jettison Spacewalk. NASA. Retrieved on 2007-07-23.
- ^ NASA (2007). STS-120 Mission Status Report #08. NASA. Retrieved on October 28, 2007.
- ^ Associated Press (2007). Astronauts Take Spacewalk to Inspect Defective Solar Wing Mechanisms. Fox News. Retrieved on December 18, 2007.
- ^ NASA (2007). Spacewalkers Find No Solar Wing Smoking Gun. NASA. Retrieved on December 18, 2007.
[edit] External links
- NASA JSC Oral History Project Walking to Olympus: An EVA Chronology PDF document.
- NASDA Online Space Notes
- Apollo Extravehicular mobility unit. Volume 1: System description - 1971 (PDF document)
- Apollo Extravehicular mobility unit. Volume 2: Operational procedures - 1971 (PDF document)
- Skylab Extravehicular Activity Development Report - 1974 (PDF document)
- Analysis of the Space Shuttle Extravehicular Mobility Unit - 1986 (PDF document)
- NASA Space Shuttle EVA tools and equipment reference book - 1993 (PDF document)
Space suits | ||
|---|---|---|
| American models | Navy Mark V • Gemini Space suit • MOL Space suit • Apollo/Skylab A7L • Extravehicular Mobility Unit • Advanced Crew Escape Suit | Image:Apollo 15 Space Suit David Scott.jpg |
| Russian models | SK-1 • Berkut • Krechet • Yastreb • Sokol • Orlan • Strizh | |
| Developing technologies | Mark III • I-Suit • Space activity suit | |
| Components | Hard Upper Torso • Liquid Cooling and Ventilation Garment • Maximum Absorbency Garment • Primary Life Support System • Thermal Micrometeoroid Garment | |
| Related topics | Extra-vehicular activity • Manned Maneuvering Unit • Pressure suit | |
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