---
title: "Astronaut"
chunk: 1/6
source: "https://en.wikipedia.org/wiki/Astronaut"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:47:08.658762+00:00"
instance: "kb-cron"
---

An astronaut (from the Ancient Greek ἄστρον (astron), meaning 'star', and ναύτης (nautes), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member of a spacecraft. Although generally reserved for professional space travelers, the term is sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and space tourists. In the United States, it is a designated term used by three agencies: NASA, the FAA, and the military. The term is also used for people who are trained to fly in a spacecraft after passing certain training courses, regardless of their experience of space travel.
"Astronaut" technically applies to all human space travelers regardless of nationality. However, astronauts fielded by Russia or the Soviet Union are typically known instead as cosmonauts (from the Russian "kosmos" (космос), meaning "space", also borrowed from Greek κόσμος). Comparatively recent developments in crewed spaceflight made by China have led to the rise of the term taikonaut (from the Mandarin "tàikōng" (太空), meaning "space"), although its use is somewhat informal and its origin is unclear. In China, the People's Liberation Army Astronaut Corps astronauts and their foreign counterparts are all officially called hángtiānyuán (航天员, meaning "celestial navigator" or literally "heaven-sailing staff").
As of April 2026, 781 humans have flown in space. Until 2002, astronauts were sponsored and trained exclusively by governments, either by the military or by civilian space agencies. With the suborbital flight of the privately funded SpaceShipOne in 2004, a new category of astronaut was created: the commercial astronaut.

== Definition ==

The word "astronaut" is sometimes used in a strictly defined sense, such as in the United States, where it is a designated term used by three agencies: NASA, the Federal Aviation Administration, and the military, with slightly different criteria for each. NASA and the military only use the term for their own employees who meet specific criteria. In Europe, the European Astronaut Corps calls graduates of their training program "ESA astronauts", being "active ESA staff having successfully completed Basic Astronaut training recognised by ESA or who have participated in a mission to space".  People who have completed this training are generally described as astronauts in the press, and the Collins and Cambridge English Dictionaries define "astronaut" as people who are trained to fly in a spacecraft. 
In addition, the criteria for what constitutes human spaceflight vary, with some focus on the point where the atmosphere becomes so thin that centrifugal force, rather than aerodynamic force, carries a significant portion of the weight of the flight object. The Fédération Aéronautique Internationale (FAI) Sporting Code for astronautics recognizes only flights that exceed the Kármán line, at an altitude of 100 kilometers (62 mi). In the United States, professional, military, and commercial astronauts who travel above an altitude of 80 kilometres (50 mi) are awarded astronaut wings.
As of 17 November 2016, 552 people from 36 countries had reached 100 km (62 mi) or more in altitude, of whom 549 reached low Earth orbit or beyond.
Of these, 28 people have traveled beyond low Earth orbit, either to lunar orbit, the lunar surface, or a loop around the Moon. Three of them—Jim Lovell, John Young and Eugene Cernan—did so twice.
As of 8 November 2026, 676 humans had flown to space under the U.S. definition. Of eight X-15 pilots who exceeded 50 miles (80 km) in altitude, only one, Joseph A. Walker, exceeded 100 kilometers (about 62.1 miles) and he did it two times, becoming the first person in space twice. Space travelers have spent over 41,790 man-days (114.5-man-years) in space, including over 100 astronaut-days of spacewalks. As of 2026, the man with the longest cumulative time in space is Oleg Kononenko, who has spent over 1100 days in space. Peggy A. Whitson holds the record for the most time in space by a woman, at 695 days.

=== Schirra definition ===
The veteran American astronaut, Wally Schirra (1923–2007), had firm views on the criteria that should apply for membership of the Society of Experimental Test Pilots (SETP) – and on the definition of an astronaut. He devoted a whole chapter (My Ultimate Peer Group) of his 1988 autobiography, Schirra's Space, to a discussion of the subject. He argued that aircraft personnel not piloting an aircraft are not aviators, and applied the strict criterion that anyone in space not in control of the flight of the spacecraft is not an astronaut:My world as a test pilot is the fighter world. You don't see bombers in my inventory. [...] Before the shuttle—in Mercury, Gemini and Apollo—astronauts were aviators. [...] But then NASA began putting others on board, people they called mission and payload specialists. Now I think of them as similar to members of a bomber crew—a bombardier, a navigator. The specialists have important duties to perform, but they should not be confused with pilots. Nor should people who don't fly the spacecraft be called astronauts.

== Terminology ==

In 1959, when both the United States and Soviet Union were planning, but had yet to launch humans into space, NASA Administrator T. Keith Glennan and his Deputy Administrator, Hugh Dryden, discussed whether spacecraft crew members should be called astronauts or cosmonauts. Dryden preferred "cosmonaut", on the grounds that flights would occur in and to the broader cosmos, while the "astro" prefix suggested flight specifically to the stars. Most NASA Space Task Group members preferred "astronaut", which survived by common usage as the preferred American term. When the Soviet Union launched the first man into space, Yuri Gagarin in 1961, they chose a term – космонавт – which anglicizes to "cosmonaut".

=== Astronaut ===