astronaut
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What is an astronaut?
An astronaut is a person who has journeyed into outer space. The term comes from Greek words meaning "star" and "sailor." While "astronaut" often refers to space travelers from the United States, Canada, Europe, and Japan, those from Russia are called cosmonauts. China's space travelers are sometimes called taikonauts.
Astronauts can be pilots, mission specialists with scientific or engineering backgrounds, or payload specialists focused on specific experiments. They undergo intense training at facilities like NASA's Johnson Space Center, learning about spacecraft systems, survival skills, and how to work in weightlessness. Spaceflight presents challenges, including microgravity-induced muscle and bone loss and exposure to radiation.
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What kind of training does an astronaut need?
Astronaut candidates, whether civilian or military, need a college degree in engineering, life science, physical science, or mathematics. NASA expects them to be team players, skilled generalists, and self-reliant.
Selected candidates undergo intense training for one to two years at NASA’s Johnson Space Center in Houston. They study shuttle and space station systems, guidance and navigation, orbital dynamics, and materials processing, plus mathematics, geology, meteorology, oceanography, astronomy, and physics. Training also includes land and sea survival, scuba diving, space suits, and coping with weightlessness. Russian language proficiency is also required. They also train in survival and simulations for high g-forces and zero-gravity environments. After completing training, they are designated NASA career astronauts.
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Why do astronauts wear space suits?
Astronauts wear space suits as a self-contained environment, supplying everything needed for survival and comfort in the vacuum of space. Without a pressurized suit, an astronaut's blood would boil. Space suits provide a pressurized interior, oxygen, and a system for removing carbon dioxide and water vapor. They also offer protection against extreme temperatures and radiation, as well as eye protection from the sun's rays.
Modern space suits have multiple layers of materials such as Dacron, nylon, and aluminum. They have built-in backpacks that hold life-support systems and other equipment. Special joints are designed to allow astronauts as much free movement as possible.
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What do astronauts do aboard the International Space Station?
Astronauts aboard the International Space Station (ISS) conduct scientific research in microgravity, maintain the station, and study the effects of extended space travel. They perform experiments in life sciences, fluid dynamics, and materials science, using unique space conditions to gain insights impossible to achieve on Earth.
Living in microgravity poses challenges like muscle atrophy and bone density loss, countered with regular exercise. The ISS has labs and habitats, solar panels for power, and relies on cargo spacecraft for essentials. Crews typically stay for about six months. English is the operating language, but astronauts must also be proficient in Russian to travel via the Soyuz spacecraft.
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How do astronauts travel to and from space?
Astronauts journey to and from space using launch vehicles that propel a spacecraft beyond Earth's atmosphere. These vehicles must reach a minimum velocity of 28,000 km per hour to achieve Earth orbit.
To return to Earth, spacecraft re-enter the atmosphere, using it as a braking force via aerodynamic drag. This generates severe heating, managed through heat shields made of ablative or refractory materials. Precise control of the reentry angle is crucial to prevent bouncing off the atmosphere or burning up. Some spacecraft use parachutes for a soft landing, while others, like the Space Shuttle, glide to a runway landing.
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Who are some famous astronauts, and what are their achievements?
Several astronauts have made significant contributions to space exploration.
- Yuri Gagarin was the first human in space, orbiting Earth in Vostok 1 on April 12, 1961, marking a major milestone in space exploration.
- Alan Shepard became the first American in space on May 5, 1961, with a suborbital flight.
- John Glenn was the first American to orbit Earth, completing three orbits in Friendship 7 on February 20, 1962.
- Neil Armstrong was the first person to walk on the Moon on July 20, 1969, during the Apollo 11 mission.
- Valentina Tereshkova was the first woman in space, orbiting Earth for three days aboard Vostok 6 in June 1963.
- Sally Ride was the first American woman in space, flying aboard the space shuttle Challenger in June 1983.
- Guion Bluford was the first African American in space, flying on the space shuttle Challenger in August 1983.
- Mae C. Jemison became the first African American woman in space in September 1992, aboard the space shuttle Endeavour.
- Chris Hadfield is a Canadian astronaut who was the first Canadian to command the International Space Station (ISS) and the first Canadian to walk in space.
- Yang Liwei was the first person sent into space by China's space program, orbiting Earth 14 times in Shenzhou 5 in October 2003.
8 Britannica Sources- Chris Hadfield
- astronaut: History and highlights
- 5 Unforgettable Moments in the History of Spaceflight and Space Exploration: First Man in Space
- How Many People Have Been to the Moon?
- 12 Questions About the History of Space Exploration Answered: Who was the first woman in space?
- history of technology: Space exploration
- space exploration: Biomedical, psychological, and sociological aspects
- Yang Liwei
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
News •
astronaut, designation, derived from the Greek words for “star” and “sailor,” commonly applied to an individual who has flown in outer space. More specifically, in the West, astronaut refers to those from the United States, Canada, Europe, and Japan who travel into space. Those Soviet and later Russian individuals who travel into space are known as cosmonauts (from the Greek words for “universe” and “sailor”). In Russia the word cosmonaut is used for space travelers of all nations. In the West, Chinese space travelers have come to be referred to as taikonauts (from the Chinese word for “space” and the Greek word for “sailor”), but in China the word yuhangyuan (from the Chinese words for “space” and “traveler”) is used.
History and highlights
As of 2022, 587 individuals from 41 countries had gone into orbit; 518 of these space fliers were men, and 69 were women. The longest time spent in space on one mission is the 438 days spent aboard the Russian space station Mir by cosmonaut Valery Polyakov in 1994–95. The longest individual cumulative time is the 878 days spent by cosmonaut Gennady Padalka on one mission to Mir and four missions to the International Space Station. Two U.S. astronauts, Franklin Chang-Díaz and Jerry Ross, made seven spaceflights, the most by any single individual. The youngest person to go into space was Oliver Daemen, who was 18 when he flew on the first flight of Blue Origin’s suborbital spacecraft New Shepard in 2021. The oldest astronaut was William Shatner, who was 90 when he flew on the second New Shepard flight in 2021.
Twenty-one space fliers—4 Russian cosmonauts and 17 American astronauts—have died during spaceflight activities. In January 1967 a three-man crew perished during a ground test of the first Apollo spacecraft; in April 1967 and June 1971, first one and then three cosmonauts died during reentry of their Soyuz vehicles; in January 1986 an entire seven-member crew died when the U.S. space shuttle Challenger exploded shortly after launch; and in February 2003 seven more astronauts were lost when the shuttle Columbia broke up on reentry.
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The first seven U.S. astronauts were chosen for Project Mercury in April 1959. They were selected from some 500 candidates, all members of the U.S. military. Each candidate was required to have experience as a pilot of high-performance jet aircraft and, because of the cramped conditions inside the Mercury spacecraft, to be no more than 5 feet 11 inches (180 cm) tall and weigh no more than 180 pounds (82 kg). These astronauts were U.S. Air Force Captains L. Gordon Cooper, Jr., Virgil (“Gus”) Grissom, and Donald (“Deke”) Slayton; Marine Lieutenant Colonel John H. Glenn, Jr.; and Navy Lieutenant M. Scott Carpenter and Lieutenant Commanders Walter M. Schirra, Jr., and Alan B. Shepard, Jr. On May 5, 1961, Alan Shepard made a brief suborbital flight, becoming the first U.S. astronaut to go into space. John Glenn became the first American in orbit with his February 20, 1962, three-orbit flight.
The Soviet Union selected 20 air force pilots from 102 candidates for cosmonaut training in February 1960. These individuals also had to meet restrictions on height (170 cm, or 5 feet 7 inches) and weight (70 kg, or 154 pounds) because of the small size of the Soviet Vostok spacecraft. The identity of these individuals was kept secret until they were actually launched into space. Most of the cosmonaut candidates were between 25 and 30 years old and thus did not have the extensive test pilot experience of their U.S. counterparts. One of these 20 young men, Yuri Gagarin, became the first human in space with his April 12, 1961, one-orbit flight.
In 1997 China selected 12 military test pilots, all men, for its first group of taikonaut trainees; the first of these to go up in space, Yang Liwei, made a 14-orbit flight in October 2003 on Shenzhou 5.
India selected four astronauts, pilots in the Indian Air Force, for the Gaganyaan program, which is scheduled to have its first crewed flight in 2024. The astronauts did the first part of their training in Russia in early 2020 and the remainder at the Indian Space Research Organisation’s astronaut training facility in Bengaluru.
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In both the United States and the Soviet Union, no women were initially selected as astronauts. (In the United States, 13 women, the “Mercury 13,” underwent some of the same testing as the seven Mercury astronauts. Wally Funk, who later became the oldest person in space in 2021, was among them.) In 1962 the Soviet Union chose five women as cosmonaut trainees; one of them, Valentina Tereshkova, went into orbit in June 1963, becoming the first woman in space. The United States did not select women for astronaut training until 1978, and the first female U.S. astronaut, Sally Ride, was launched aboard the space shuttle Challenger in June 1983. China selected two women in its second group of taikonaut trainees in 2010, and the first to fly in to space was Liu Yang on Shenzhou 9 in June 2012.
The United States selected only pilots as astronauts until 1965, when six scientists with technical or medical degrees were chosen for astronaut training. One of them, geologist Harrison (“Jack”) Schmitt, became a crew member of Apollo 17, the final Apollo mission to the Moon, in December 1972.
All told, 24 astronauts (all Americans) have gone to the Moon, and 12 of them walked on its surface. As part of the Artemis space program, launched in 2017, NASA aims to return astronauts to the Moon by 2025, with the goal of establishing a sustainable presence there and on other planets. The program also seeks to land the first woman and first person of colour on the Moon, and that woman may be Jessica Meir.