Extravehicular activity (EVA) is any activity done by an astronaut or cosmonaut outside a spacecraft beyond the Earth's appreciable atmosphere. The term most commonly applies to a spacewalk made outside a craft orbiting Earth (such as the International Space Station), but also has applied to lunar surface exploration (commonly known as moonwalks) performed by six pairs of American astronauts in the Apollo program from 1969 to 1972. On each of the last three of these missions, astronauts also performed deep-space EVAs on the return to Earth, to retrieve film canisters from the outside of the spacecraft. Astronauts also used EVA in 1973 to repair launch damage to Skylab, the United States' first space station.
A "Stand-up" EVA (SEVA) is when an astronaut does not fully leave a spacecraft, but is completely reliant on the spacesuit for environmental support. Its name derives from the astronaut "standing up" in the open hatch, usually to record or assist a spacewalking astronaut.
EVAs may be either tethered (the astronaut is connected to the spacecraft; oxygen and electrical power can be supplied through an umbilical cable; no propulsion is needed to return to the spacecraft), or untethered. 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 safety device worn on tethered U.S. EVAs.
The Soviet Union/Russia, the United States, and China have conducted EVAs.
NASA planners invented the term extravehicular activity (abbreviated with the acronym EVA) in the early 1960s for the Apollo program to land men on the Moon, because the astronauts would leave the spacecraft to collect lunar material samples and deploy scientific experiments. To support this, and other Apollo objectives, the Gemini program was spun off to develop the capability for astronauts to work outside a two-man Earth orbiting spacecraft. However, the Soviet Union was fiercely competitive in holding the early lead it had gained in manned spaceflight, so the Soviet Communist Party, led by Nikita Khrushchev, ordered the conversion of its single-pilot Vostok capsule into a two- or three-person craft named Voskhod, in order to compete with Gemini and Apollo. The Soviets were able to launch two Voskhod capsules before U.S. was able to launch its first manned Gemini.
The Voskhod's avionics required cooling by cabin air to prevent overheating, therefore an airlock was required for the spacewalking cosmonaut to exit and re-enter the cabin while it remained pressurized. By contrast, the Gemini avionics did not require air cooling, allowing the spacewalking astronaut to exit and re-enter the depressurized cabin through an open hatch. Because of this, the American and Soviet space programs developed different definitions for the duration of an EVA. The Soviet (now Russian) definition begins when the outer airlock hatch is open and the cosmonaut is in vacuum. An American EVA began when the astronaut had at least his head outside the spacecraft. The USA has changed its EVA definition since.
The first EVA was performed on March 18, 1965, by Soviet cosmonaut Alexey Leonov, who spent 12 minutes outside the Voskhod 2 spacecraft. Carrying a white metal backpack containing 45 minutes worth of breathing and pressurization oxygen, Leonov had no means to control his motion other than pulling on his 15.35 m (50.4 ft) tether. After the flight, he claimed this was easy, but his space suit ballooned from its internal pressure against the vacuum of space, stiffening so much that he could not activate the shutter on his chest-mounted camera.
At the end of his space walk, the suit stiffening caused a more serious problem: Leonov had to re-enter the capsule through the inflatable cloth airlock, 1.2 m (3 ft 11 in) in diameter and 2.5 m (8 ft 2 in) long. He improperly entered the airlock head-first and got stuck sideways. He could not get back in without reducing the pressure in his suit, risking "the bends". This added another 12 minutes to his time in vacuum, and he was overheated by 1.8 °C (3.2 °F) from the exertion. It would be almost four years before the Soviets tried another EVA. They misrepresented to the press how difficult Leonov found it to work in weightlessness and concealed the problems encountered until after the end of the Cold War.
The first American spacewalk was performed on June 3, 1965, by Ed White from the second manned Gemini flight, Gemini 4, for 21 minutes. White was tethered to the spacecraft, and his oxygen was supplied through a 25-foot (7.6 m) umbilical, which also carried communications and biomedical instrumentation. He was the first to control his motion in space with a Hand-Held Maneuvering Unit, which worked well but only carried enough propellant for 20 seconds. White found his tether useful for limiting his distance from the spacecraft but difficult to use for moving around, contrary to Leonov's claim. However, a defect in the capsule's hatch latching mechanism caused difficulties opening and closing the hatch, which delayed the start of the EVA and put White and his crewmate at risk of not getting back to Earth alive.
No EVAs were planned on the next three Gemini flights. The next EVA was planned to be made by David Scott on Gemini 8, but that mission had to be aborted due to a critical spacecraft malfunction before the EVA could be conducted. Astronauts on the next three Gemini flights (Eugene Cernan, Michael Collins, and Richard Gordon), performed several EVAs, but none was able to successfully work for long periods outside the spacecraft without tiring and overheating. Cernan attempted but failed to test an Air Force Astronaut Maneuvering Unit which included a self-contained oxygen system.
On November 13, 1966, Edwin "Buzz" Aldrin became the first to successfully work in space without tiring, on the Gemini 12 last flight. Aldrin worked outside the spacecraft for 2 hours and 6 minutes, in addition to two stand-up EVAs in the spacecraft hatch for an additional 3 hours and 24 minutes. Aldrin's interest in scuba diving inspired the use of underwater EVA training to simulate weightlessness, which has been used ever since to allow astronauts to practice techniques of avoiding wasted muscle energy.
On January 16, 1969, Soviet cosmonauts Aleksei Yeliseyev and Yevgeny Khrunov transferred from Soyuz 5 to Soyuz 4, which were docked together. This was the second Soviet EVA, and it would be almost another nine years before the Soviets performed their third.
American astronauts Neil Armstrong and Buzz Aldrin performed the first EVA on the lunar surface on July 21, 1969 (UTC), after landing their Apollo 11 Lunar Module spacecraft. This first Moon walk, using self-contained portable life support systems, lasted 2 hours 36 minutes. A total of fifteen Moon walks were performed among six Apollo crews, including Charles "Pete" Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, James Irwin, John Young, Charles Duke, Eugene Cernan, and Harrison "Jack" Schmitt. Cernan was the last Apollo astronaut to step off the surface of the Moon.
Apollo 15 Command Module Pilot Al Worden made an EVA on August 5, 1971, on the return trip from the Moon, to retrieve a film and data recording canister from the Service Module. He was assisted by Lunar Module Pilot James Irwin standing up in the Command Module hatch. This procedure was repeated by Ken Mattingly and Charles Duke on Apollo 16, and by Ronald Evans and Harrison Schmitt on Apollo 17.
The first EVA repairs of a spacecraft were made by Charles "Pete" Conrad, Joseph Kerwin, and Paul J. Weitz on May 26, June 7, and June 19, 1973, on the Skylab 2 mission. They rescued the functionality of the launch-damaged Skylab space station by freeing a stuck solar panel, deploying a solar heating shield, and freeing a stuck circuit breaker relay. The Skylab 2 crew made three EVAs, and a total of ten EVAs were made by the three Skylab crews. They found that activities in weightlessness required about 2½ times longer than on Earth because many astronauts suffered spacesickness early in their flights.
After Skylab, no more EVAs were made by the United States until the advent of the Space Shuttle program in the early 1980s. In this period, the Soviets resumed EVAs, making four from the Salyut 6 and Salyut 7 space stations between December 20, 1977, and July 30, 1982.
When the United States resumed EVAs on April 7, 1983, astronauts started using an Extravehicular Mobility Unit (EMU) for self-contained life support independent of the spacecraft. STS-6 was the first Space Shuttle mission during which a spacewalk was conducted. Also, for the first time, American astronauts used an airlock to enter and exit the spacecraft like the Soviets. Accordingly, the American definition of EVA start time was redefined to when the astronaut switches the EMU to battery power.
China became the third country to independently carry out an EVA on September 27, 2008 during the Shenzhou 7 mission. Chinese astronaut Zhai Zhigang completed a spacewalk wearing the Chinese-developed Feitian space suit, with astronaut Liu Boming wearing the Russian-derived Orlan space suit to help him. Zhai completely exited the craft, while Liu stood by at the airlock, straddling the portal.
The first spacewalk, made by Soviet cosmonaut Alexey Leonov, was commemorated in 1965 with several Eastern Bloc stamps (see Alexey Leonov#Stamps). Since the Soviet Union did not publish details of the Voskhod spacecraft at the time, the spaceship depiction in the stamps was purely fictional.
The U.S. Post Office issued a postage stamp in 1967 commemorating Ed White's first American spacewalk. The engraved image has an accurate depiction of the Gemini IV spacecraft and White's space suit.
For EVAs from the International Space Station, 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 sleep overnight in the airlock prior to an EVA, lowering the air pressure to 10.2 psi (70 kPa), compared to the normal station pressure of 14.7 psi (101 kPa). Spending a night at the lower air pressure helps flush nitrogen from the body, thereby preventing "the bends". More recently astronauts have been using the In-Suit Light Exercise protocol rather than camp-out to prevent decompression sickness.
Alexey Arkhipovich Leonov (Russian: Алексе́й Архи́пович Лео́нов, IPA: [ɐlʲɪˈksʲej ɐˈrxʲipəvʲɪtɕ lʲɪˈonəf]; born 30 May 1934) is a retired Soviet/Russian cosmonaut, Air Force Major general, writer and artist. On 18 March 1965, he became the first human to conduct extravehicular activity (EVA), exiting the capsule during the Voskhod 2 mission for a 12-minute spacewalk.Apollo 9
Apollo 9 was the third crewed mission in the United States Apollo space program and the first flight of the command and service module (CSM) with the Apollo Lunar Module (LM, pronounced "lem"). The mission's three-person crew consisted of Commander James McDivitt, Command Module Pilot David Scott, and Lunar Module Pilot Rusty Schweickart. The crew spent ten days in low Earth orbit testing several aspects critical to landing on the Moon, including the LM engines, backpack life support systems, navigation systems, and docking maneuvers. The mission was the second crewed launch of a Saturn V rocket.
After launching on March 3, 1969, the crew performed the first crewed flight of a LM, the first docking and extraction of a LM, one two-person spacewalk (EVA), and the second docking of two crewed spacecraft—two months after the Soviets performed a spacewalk crew transfer between Soyuz 4 and Soyuz 5. The mission proved the LM worthy of crewed spaceflight. Further tests on the Apollo 10 mission would prepare the LM for its ultimate goal, landing on the Moon. They returned to Earth on March 13, 1969.Astronaut propulsion unit
An astronaut propulsion unit (or astronaut maneuvering unit) is used to move an astronaut relative to the spaceship during a spacewalk. The first astronaut propulsion unit was the Hand-Held Maneuvering Unit (HHMU) used on Gemini 4.Berkut spacesuit
The Berkut (Russian Беркут, meaning golden eagle) is a space suit model developed to be used for extravehicular activity for the Voskhod 2 mission aboard a Voskhod spacecraft on the first spacewalk. It was developed by NPP Zvezda in 1964-1965. It was a modified SK-1 suit. It was only used by the Voskhod 2 crew.Extravehicular Mobility Unit
The Extravehicular Mobility Unit (EMU) is an independent anthropomorphic spacesuit that provides environmental protection, mobility, life support, and communications for astronauts performing extravehicular activity (EVA) in Earth orbit. Introduced in 1981, it is a two-piece semi-rigid suit, and is currently one of two EVA spacesuits used by crew members on the International Space Station (ISS), the other being the Russian Orlan space suit. It was used by NASA's Space Shuttle astronauts prior to the end of the Shuttle program in 2011.Feitian space suit
A Feitian space suit (Chinese: 飞天航天服; pinyin: Fēitiān Hángtiān Fù) is a Chinese spacesuit that was developed for the Shenzhou 7. Astronaut Zhai Zhigang wore it during China's first-ever extra-vehicular activity (EVA) on September 27, 2008.The Feitian spacesuit was modelled after the Orlan-M spacesuit developed by Russia. The two kinds of suits are similar in shape and volume and are designed for spacewalks of up to seven hours, providing oxygen and allowing for the excretion of bodily waste.The suit is reported to have cost $4.4 million, and weighs 120 kg (260 lb). The name Fēi tiān literally and separately means "flying" and "sky" in Mandarin. It is a reference to the apsara, translated as feitian, or the "flying deva", in Chinese, and most famously depicted in Chinese art in the grottoes of Dunhuang. Images of the feitian from Dunhuang appear on the arm badge of the space suit.Gemini 10
Gemini 10 (officially Gemini X) was a 1966 manned spaceflight in NASA's Gemini program. It was the 8th manned Gemini flight, the 16th manned American flight and the 24th spaceflight of all time (includes X-15 flights over 100 kilometers (54 nautical miles)).Gemini 11
Gemini 11 (officially Gemini XI) was the ninth manned spaceflight mission of NASA's Project Gemini, which flew from September 12 to 15, 1966. It was the 17th manned American flight and the 25th spaceflight to that time (includes X-15 flights over 100 kilometers (54 nmi)). Astronauts Charles "Pete" Conrad Jr. and Richard F. Gordon Jr. performed the first-ever direct-ascent (first orbit) rendezvous with an Agena Target Vehicle, docking with it one hour and thirty-four minutes after launch; used the Agena rocket engine to achieve a world record high-apogee earth orbit; and created a small amount of artificial gravity by spinning the two spacecraft connected by a tether. Gordon also performed two extra-vehicular activities for a total of 2 hours and 41 minutes.Gemini 12
Gemini 12 (officially Gemini XII) was a 1966 manned spaceflight in NASA's Project Gemini. It was the 10th and final manned Gemini flight, the 18th manned American spaceflight, and the 26th spaceflight of all time, including X-15 flights over 100 kilometers (54 nmi). Commanded by Gemini VII veteran James A. Lovell, the flight featured three periods of extravehicular activity (EVA) by rookie Edwin "Buzz" Aldrin, lasting a total of 5 hours and 30 minutes. It also achieved the fifth rendezvous and fourth docking with an Agena target vehicle.
Gemini XII marked a successful conclusion of the Gemini program, achieving the last of its goals by successfully demonstrating that astronauts can effectively work outside of spacecraft. This was instrumental in paving the way for the Apollo program to achieve its goal of landing a man on the Moon by the end of the 1960s.List of cumulative spacewalk records
This is a list of cumulative spacewalk records for the 30 astronauts who have the most extra-vehicular activity (EVA) time. The record is currently held by Anatoly Solovyev of the Russian Federal Space Agency, with 82:22 hours from 16 EVAs, followed by NASA's Michael Lopez-Alegria with 67:40 hours in 10 EVAs. This list is current as of August 2017. The RSA designation includes spacewalks under the earlier Soviet space program.List of spacewalks since 2015
This list contains all spacewalks performed since the beginning of 2015 where an astronaut has fully, or partially left the spacecraft.
As of 19 August 2016, 215 astronauts have made spacewalks (out of 549 people who have gone into Earth orbit).Lists of spacewalks and moonwalks
Lists of spacewalks and moonwalks include:
List of spacewalks and moonwalks 1965–1999
List of spacewalks 2000–2014
List of spacewalks since 2015By space station:
List of Salyut spacewalks
List of Mir spacewalks
List of International Space Station spacewalksOther:
List of cumulative spacewalk recordsManned 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 EVA spacewalks at a distance from the shuttle. The MMU was used in practice to retrieve a pair of faulty communications satellites, Westar VI and Palapa B2. Following the third mission the unit was retired from use. A smaller successor, the Simplified Aid For EVA Rescue (SAFER), was first flown in 1994, and is intended for emergency use only.Orlan space suit
The Orlan space suit (Russian: Орлан meaning sea eagle) is a series of semi-rigid one-piece space suit models designed and built by NPP Zvezda. They have been used for spacewalks (EVAs) in the Russian space program, the successor to the Soviet space program, and by space programs of other countries, including NASA.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 would provide free-flying mobility to return to it. It is worn on spacewalks outside the International Space Station (ISS), and was worn on spacewalks outside the Space Shuttle. So far, there has not been an emergency in which it was needed. SAFER is a small, simplified version of the Manned Maneuvering Unit (MMU), which was used for regular maneuvering.Skylab 2
Skylab 2 (also SL-2 and SLM-1) was the first manned mission to Skylab, the first U.S. orbital space station. The mission was launched on a Saturn IB rocket on May 25, 1973, and carried a three-person crew to the station. The name Skylab 2 also refers to the vehicle used for that mission. The Skylab 2 mission established a twenty-eight-day record for human spaceflight duration. Furthermore, its crew were the first space station occupants ever to return safely to Earth – the only previous space station occupants, the crew of the 1971 Soyuz 11 mission that had manned the Salyut 1 station for twenty-four days, died upon reentry due to unexpected cabin depressurization.
The manned Skylab missions were officially designated Skylab 2, 3, and 4. Miscommunication about the numbering resulted in the mission emblems reading Skylab I, Skylab II, and Skylab 3 respectively.Skylab 3
Skylab 3 (also SL-3 and SLM-2) was the second manned mission to the first American space station, Skylab. The mission began July 28, 1973, with the launch of three astronauts on the Saturn IB rocket, and lasted 59 days, 11 hours and 9 minutes. A total of 1,084.7 astronaut-utilization hours were tallied by the Skylab 3 crew performing scientific experiments in the areas of medical activities, solar observations, Earth resources, and other experiments.
The manned Skylab missions were officially designated Skylab 2, 3, and 4. Mis-communication about the numbering resulted in the mission emblems reading Skylab I, Skylab II, and Skylab 3 respectively.Skylab 4
Skylab 4 (also SL-4 and SLM-3) was the third manned Skylab mission and placed the third and final crew aboard the first American space station.
The mission started on November 16, 1973 with the launch of three astronauts on a Saturn IB rocket from the Kennedy Space Center, Florida and lasted 84 days, one hour and 16 minutes. A total of 6,051 astronaut-utilization hours were tallied by Skylab 4 astronauts performing scientific experiments in the areas of medical activities, solar observations, Earth resources, observation of the Comet Kohoutek and other experiments.
The manned Skylab missions were officially designated Skylab 2, 3, and 4. Mis-communication about the numbering resulted in the mission emblems reading Skylab I, Skylab II, and Skylab 3 respectively.Zhai Zhigang
Zhai Zhigang (born October 10, 1966) is a major general in the People's Liberation Army Air Force and a CNSA astronaut. During the Shenzhou 7 mission in 2008, he became the first Chinese citizen to carry out a spacewalk.