Crewed spaceflight Summary

  • Last updated on November 10, 2022

Any flight that carries humans into space.


The flight of humans into space had been the dream of science-fiction writers and explorers for more than a century before the first crewed spaceflight. Explorers regarded the first human step into space as the beginning of a new age of exploration, in which humans eventually explored the Moon, Mars, the asteroids, and all of the solar system.

Humans were preceded into space by robotic spacecraft containing instruments to monitor the earth and space environment and to explore the solar system. These uncrewed spacecraft frequently suffered from a lack of intelligence, or, the ability to adapt to unforseen circumstances. Thus, after a new discovery was made, it was frequently necessary to design a follow-on spacecraft, with new equipment intended to help scientists to understand more fully the measurements from the previous mission. Crewed spaceflight was expected to allow human intelligence and ingenuity to respond and adapt to discoveries or problems encountered during flight.

Neither the drive to explore the unknown nor the need for human intelligence in space provided the motivation for the vast expenditure of government funds needed to send humans into space. The real motivation was the intense political competition between the capitalist and communist political systems during the Cold War. The political leaders of both the United States and the Soviet Union saw success in space exploration as a way to demonstrate to their own citizens and to the rest of the world the superiority of one political system over the other.

The First Humans in Space

Following the launch of the world’s first artificial Earth satellite, Sputnik 1, on October 4, 1957, both the United States and the Soviet Union began serious efforts to launch humans into space. The U.S. effort was called Project Mercury, and the Soviet program was called Vostok.

The formal selection process for the Mercury astronauts began in January, 1959, when the National Aeronautics and Space Administration (NASA) chose 110 military test pilots from 508 candidates submitted by the Department of Defense. The 110 candidates were carefully screened for physical fitness, experience, skill, and size, to accommodate the small size of the Mercury spacecraft. On April 27, 1959, NASA announced the names of the seven astronauts chosen for Project Mercury: Navy lieutenant M. Scott Carpenter; Air Force captain Leroy Cooper; Marine lieutenant colonel John Glenn, Jr.; Air Force captain Virgil “Gus” Grissom; Navy lieutenant commander Walter Schirra; Navy lieutenant commander Alan Shepard; and Air Force captain Donald “Deke” Slayton. The Soviet Union was, at the same time, conducting its own selection process, although the Soviet selection effort received less publicity than did the U.S. effort. On March 14, 1960, the Soviet Union selected a group of twelve cosmonauts: Pavel Belyayev, Valeri Bykovsky, Yuri Gagarin, Viktor Gorbatko, Yevgeny Khrunov, Vladimir Komarov, Alexei Leonov, Andrian Nikolayev, Pavel Popovich, Georgi Shomin, Gherman Titov, and Boris Volynov.

The Soviet Union’s second artificial satellite, Sputnik 2, launched on November 3, 1957, demonstrated the technology that was required for humans to fly in space. Sputnik 2 carried an 11-pound dog named Laika into orbit. Monitors on Sputnik 2 demonstrated that the interior temperature could be maintained in a range suitable for human survival and that a suitable atmosphere could be maintained using a system of reactive chemicals that give off oxygen and another chemical system to absorb exhaled carbon dioxide.

During the spring of 1960, engineers in both the United States and the Soviet Union were working to place the first human into space. The timetable for the U.S. program was highly publicized, whereas little information about the Soviet Union’s effort was released. A series of uncrewed test vehicles preceded the crewed flights. The first flight of the Vostok capsule, on May 15, 1960, failed after the capsule did not reenter Earth’s atmosphere. The second Vostok flight, in August, 1960, carried two dogs who were recovered successfully after reentry. The third flight, in December, 1960, suffered a failure to reenter the atmosphere, and the dog carried on board was killed. In March, 1961, the final Vostok test flight successfully carried a dog into orbit. The United States made successful suborbital flights of the Mercury spacecraft in December 19, 1960, and January 31, 1961. The January, 1961, flight carried a chimpanzee named Ham, the first primate to fly into space, on a 15-minute spaceflight to an altitude of over 100 miles.

At 9:07 a.m. Moscow time on April 12, 1961, the era of human spaceflight began with the launching of Vostok 1, carrying cosmonaut Yuri Gagarin, into orbit from a launch pad at the Baikonur Cosmodrome in Kazakhstan. Gagarin completed one Earth orbit and landed near Smelovka, on the Volga River, 108 minutes after liftoff.

Only three weeks later, the first crewed flight of the U.S. Mercury project was launched. At 9:34 a.m. on May 5, 1961, a Redstone rocket carried astronaut Alan Shepard from the Cape Canaveral Air Force Station. Five minutes after liftoff, Shepard’s spacecraft, Freedom 7, reached its peak altitude of 107 miles above Earth’s surface. Shepard’s flight lasted 15 minutes and 22 seconds and carried him 290 miles over the Atlantic Ocean.

On May 25, 1961, fewer than three weeks after Shepard’s successful suborbital spaceflight, President John F. Kennedy publicly committed the United States to the goal of landing a man on the Moon and returning him safely to the earth before the end of the 1960’s. Recognizing that Shepard’s suborbital flight did not match either the orbital flight conducted by Gagarin or the Soviet Union’s leadership in space exploration, Kennedy established a more long-term goal for the space race.

On August 6, 1961, the Soviet Union launched cosmonaut Gherman Titov, the backup pilot for Gagarin’s flight, on a seventeen-orbit spaceflight lasting 25 hours and 18 minutes. During his flight, Titov suffered severe space sickness in response to weightlessness, demonstrating that human flight into space would present physiological problems.

The United States matched Gagarin’s orbital flight on February 20, 1961, when astronaut Glenn was launched into space. Glenn completed three orbits before returning to Earth after 4 hours and 55 minutes. During the flight, the ground controllers received a signal that the heatshield, which proctected Glenn and his Friendship 7 capsule from burning up during the extreme heat of reentry, had come loose from the spacecraft. Ground controllers instructed Glenn to override the planned separation of the retrorocket package from the spacecraft and to use the straps that held the retrorockets to the spacecraft to hold the heatshield in place. Although the difficulty turned out only to be a faulty sensor, Glenn’s intervention could have been vital to the successful completion of the mission if the heatshield had indeed come loose.

The Soviet Union followed its Vostok program with the Soyuz program, using a spacecraft that could carry up to three cosmonauts on spaceflights lasting several days. The nation also developed a series of space stations, called Salyuts, which were visited by cosmonauts carried aloft in the Soyuz spacecraft.

The U.S. Mercury project was followed by the Gemini Program, in which two astronauts flew in a single spacecraft. In the Gemini missions, astronauts demonstrated orbital rendezvous and spacewalking techniques that would be required for lunar landings. The Gemini Program was followed by the Apollo Program, which had the goal of landing astronauts on the Moon. A total of twelve Apollo astronauts walked on the Moon, beginning with astronauts Neil Armstrong and Edwin “Buzz” Aldrin, who landed on the Moon on July 20, 1969. Leftover Apollo hardware was used to launch the first U.S. space station, called Skylab, and to perform the first joint U.S.-Soviet spaceflight, Apollo-Soyuz.

On April 23, 1967, cosmonaut Vladimir Komarov became the first human to die in space. Komarov was piloting the first test flight of Soyuz 1. On the spacecraft’s eighteenth orbit, its maneuvering system began to malfunction, and Komarov attempted to make a landing. However, he could not control the spacecraft, which became entangled in the cords of its parachute and hit the ground at more than 200 miles per hour, killing its pilot.

In June, 1971, three cosmonauts, George Dobrovolsky, Vladislav Volkov, and Viktor Patsayev, were killed when the Soyuz 11 spacecraft returned to Earth after a twenty-three-day stay at the Salyut 1 space station. A valve, designed to open after the spacecraft reentered the atmosphere, opened while the Soyuz was still in space, allowing the spacecraft’s air to escape and suffocating the crew.

The United States has also suffered human losses in its development of spaceflight. On January 27, 1967, during a preflight Apollo test, a fire swept rapidly through the Apollo Command Module, killing all three astronauts participating in the test, Roger Chaffee, Virgil “Gus” Grissom, and Edward White. After the fire, NASA officials designated the test as Apollo 1, honoring the crew. An extensive investigation revealed numerous design flaws, and manned launchings were postponed for more than a year while an extensive redesign was conducted.

On January 28, 1986, the space shuttle Challenger exploded shortly after liftoff. It carried a crew of seven astronauts: Francis Scobee, the commander; Michael Smith, the pilot; Judith Resnik, Ellison Onizuka, and Ronald McNair, all mission specialists; Gregory Jarvis, a payload specialist; and America’s first schoolteacher in space, Sharon Christa McAuliffe. Below-freezing temperatures had hardened the O-ring seals between the segments of the solid-fueled rocket boosters causing one joint in the right solid rocket booster to develop a leak. After liftoff, hot gases cut through metal on the shuttle, and seventy-three seconds into the flight, the Challenger disintegrated, and all seven astronauts were killed.

More recent developments have been more positive. On February 20, 1986, the Soviet Union launched the Mir Space Station, which would be almost continuously occupied by a succession of crews for fifteen years before being deorbited on February 23, 2001. In 1999, NASA, working with a group of international partners including Canada, Japan, Russia, and the European Space Agency (ESA), began construction of the International Space Station (ISS). By 2001, after forty years of human exploration of space, more than 400 astronauts and cosmonauts had flown into space.

Risks Versus Benefits

Because space is not a natural environment for humans, sophisticated life-support systems are required to maintain atmospheric composition, temperature, and other features within a range suitable for human survival. The failure of any critical system can result in death for the crew.

Crewed spaceflight is also inherently more costly than robotic spaceflight, because the crew and its life-support systems must be carried into orbit at a cost of about $10,000 per pound. During the 1970’s, NASA officials had decided that the space shuttle would carry all future payloads into space, even simple satellites that required no human intervention. NASA began to phase out rockets, such as the Delta, that had been used to launch uncrewed satellites. A highly focused debate developed over the next two decades over the relative merits of crewed versus uncrewed spaceflight. Critics of crewed spaceflight specifically targeted NASA’s planned space station as a high-cost project whose scientific return would be less than if an equivalent amount of money were spent on robotic spacecraft. Following the Challenger accident, NASA officials decided that the crewed space shuttle fleet would be used only to launch satellites that required human intervention, and a fleet of new booster rockets was developed to launch robotic satellites.

However, in crewed spaceflight, humans can accomplish many tasks that may not be performed by robotic spacecraft. For example, when thrusters on his Gemini spacecraft began firing, causing the craft to rotate rapidly, astronaut Neil Armstrong was able to regain control of the spacecraft and return it safely to Earth. After an explosion on board the Apollo 13 mission to the Moon, astronauts modified the spacecraft’s air-purification system so that they could survive the return to Earth. Cosmonauts overcame damage from an onboard fire and the leaks and damage caused by the impact of a resupply spacecraft, keeping the Mir Space Station operational. Space shuttle astronauts have repaired the Hubble Space Telescope, salvaged the improperly orbiting Westar-VI and Palapa-B2 satellites, and assembled large structures, including the International Space Station.

  • Catchpole, John. Project Mercury: NASA’s First Manned Space Programme. London: Springer-Praxis, 2001. A extensive account of Project Mercury, including its history, accomplishments, and personalities.
  • Olberg, James E. Red Star in Orbit. New York: Random House, 1980. A comprehensive account, drawn mainly from Soviet media reports, of the Soviet space program, including the Vostok series of crewed spacecraft and the development of the ICBM that served as the Vostok launch vehicle.
  • Stoiko, Michael. Soviet Rocketry. New York: Holt, Rinehart and Winston, 1970. Provides an exhaustive discussion of the design, flight, and accomplishments of the first Vostok satellites and describes the development of the R-7 ICBM that launched the early Vostok satellites.
  • Yenne, Bill. The Astronauts: The First Twenty-five Years of Manned Space Flight. New York: Exter, 1986. A comprehensive account of all crewed space missions from Yuri Gagarin’s flight in 1961 through the Challenger accident in 1986, with extensive coverage of the flights of both the United States and the Soviet Union.

Apollo Program

Neil Armstrong

Astronauts and cosmonauts

Yuri Gagarin

John Glenn

Gemini Program

Mercury project

National Aeronautics and Space Administration

Russian space program

Alan Shepard

Space shuttle

By the time Skylab 3 was launched in 1973, astronauts were able to dispense with their heavy spacesuits once in orbit and could even take showers while in space.

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