Flight beyond Earth’s atmosphere through the use of artificial satellites, space probes, or crewed spacecraft.


Humans have long dreamed of leaving Earth to explore extraterrestrial worlds. Ancient writers told stories of trips beyond Earth, and natural philosophers speculated that heavenly bodies were made of an element completely different from terrestrial elements. In the sixteenth century, Polish astronomer Nicolaus Copernicus vastly expanded humanity’s knowledge of the space containing these heavenly bodies by locating the Sun, instead of Earth, at the universe’s center. As astronomical knowledge increased, storytellers imagined spaceflights of increasing sophistication.

In the nineteenth century, writers such as Jules Verne depicted space travel in elaborate technical detail. In the twentieth century, science-fiction writers described spaceflight with scientific accuracy, and their stories became more popular than they ever had been, as the practical means of going into space became a reality.


Just as Orville and Wilbur Wright had to solve several basic problems before achieving success in their first airplane, so, too, did spaceflight pioneers need to solve such problems as discovering a way to escape Earth’s gravity. Rockets were first proposed for spacecraft propulsion in the twentieth century. The Russian engineer Konstantin Tsiolkovsky wrote extensively on the theory of spaceflight, including the need for multistage rockets, where two or more rockets are ignited in turn. The American physicist Robert H. Goddard designed, built, and launched the first liquid-fueled rockets. During World War II, the German rocket pioneer Wernher von Braun led a team of scientists who developed the first rocket-powered ballistic missile. Although the Germans designed this V-2 as a weapon, it became the model for all rockets—military, scientific, civilian, and commercial—that followed it.

Toward the end of World War II, the U.S. and Soviet military captured German scientists and engineers who had worked on the V-2 project. These scientists formed the core of postwar rocket-research programs. The United States launched more than fifty captured V-2 rockets and began using two-stage rockets for upper-atmosphere studies. Some of these vehicles achieved spaceflight, reaching the point where space begins, about 62 miles (100 kilometers) above Earth’s surface. However, they did not have enough speed to go into orbit.

The Soviet Union was the first country to achieve orbital spaceflight when Sputnik 1 began to circle Earth on October 4, 1957. This first artificial satellite ushered in the age of spaceflight. A month later, the Russians launched Sputnik 2, which contained the dog Laika, the world’s first space traveler.

These first Soviet spaceflights created a sensation around the world and especially in the United States, where it had long been assumed that Americans would be the first to achieve spaceflight. The Sputnik flights did much to change the nature of the Cold War from a political conflict between the United States and the Soviet Union to a comprehensive competition involving science, technology, and economics. Spaceflight became a symbol of the achievements of two different societies, capitalist and communist.

After civilian rockets failed to launch American satellites, President Dwight D. Eisenhower turned to the military for assistance. Five days after Sputnik 2 entered orbit, the U.S. Army used a Jupiter C rocket to orbit Explorer 1, whose instrumentation had been developed by University of Iowa physics professor James Van Allen. This Explorer mapped a doughnut-shaped region of high radiation surrounding the Earth that was later named the Van Allen radiation belts.

After the Soviet Union launched Sputnik 3 on May 15, 1958, U.S. leaders realized that the United States was falling behind in the space race. An acrimonious debate between Congress and the Eisenhower administration ensued, with the final resolution that the U.S. space program needed an effective legislative foundation. This legislation, the National Aeronautics and Space Act of 1958, created a civilian agency to explore space: the National Aeronautics and Space Administration (NASA). The act made no mention of crewed spaceflight, but its broad charter gave NASA the responsibility for the scientific, but not military, exploration of space.

During the first few years of the space age, uncrewed spaceflight characterized both U.S. and Soviet programs. These uncrewed spaceflights ranged from satellites in low-Earth orbit to probes aimed at interplanetary space. The first successful lunar probe was the Soviet Union’s Luna 1, which flew by the Moon in January, 1959. In March of that year, the United States Pioneer 4 glided by the Moon, and in September, the Soviet’s Luna 2 became the first human artifact to land on the Moon. A month later, the Russians used their circumlunar probe Luna 3 to photograph the far side of the Moon.

Soon after these uncrewed satellites and probes were launched, both Soviet and American scientists began work on crewed space vehicles. Because of their lead in large rockets, the Soviet Union was able, on April 12, 1961, to launch the world’s first crewed spacecraft, Vostok 1, a 3-ton sphere with a 2-ton service module. Soviet cosmonaut Yuri Gagarin thus became the first person to orbit Earth. After Gagarin’s single orbit and safe return to Earth, the Soviet Union achieved several firsts and set several records. It launched several endurance record-setting crewed spaceflights and had a cosmonaut take the first space walk. Furthermore, Vostok 6 was piloted by Valentina Tereshkova, the first woman to make a spaceflight. The Soviets were also the first to orbit a spacecraft containing three cosmonauts.

The initial U.S. program for crewed spaceflight was called Mercury, and it became the responsibility of the newly formed NASA. A few months into John F. Kennedy’s presidency and less than one month after Gagarin’s flight, Alan Shepard became the first American astronaut launched into space, though his suborbital flight in a Mercury capsule lasted only about fifteen minutes. The first American orbital flight was made by astronaut John Glenn on February 20, 1962. Other Mercury flights stretched the spacecraft’s orbital time to more than one day, and scientists and astronauts gained much valuable experience and information from the program, including the fact that humans should be active pilots rather than passive passengers during the missions.

While the United States and the Soviet Union developed their crewed spaceflight programs, both countries continued to develop uncrewed satellites and probes. For example, Americans launched the Television Infrared Observations Satellite (TIROS), the first weather satellite, in 1960, and it recorded more than 23,000 cloud images. Mariner 2, sent off by U.S. scientists in 1962, became the first spacecraft to explore another planet, Mars. From 1962 to 1965, the United States sent a series of Ranger probes to the Moon to take close-up photographs of its surface. The first successful soft landing on the Moon was that of the Soviet Union’s Luna 9 on February 3, 1966. The United States achieved a successful soft landing on June 2, 1966, with its Surveyor 1. On April 3, 1966, the Soviet’s Luna 10 became the first probe to successfully orbit the Moon. The first American lunar orbiter went around the Moon on August 14, 1966. With these and other lunar projects, it seemed obvious to many that the United States and the Soviet Union were engaged in a race to land humans on the Moon.

Crewed Lunar Spaceflights

The early Soviet successes in spaceflight placed intense political pressure on the U.S. president and lawmakers to find some accomplishment by which the United States could pull ahead of the Soviet Union. President Kennedy’s advisors suggested a crewed landing on the Moon as such an achievement, and on May 25, 1961, Kennedy stood before Congress to ask the nation to “set the goal of landing a man on the Moon, before this decade is out, and safely returning him to Earth.”

To attain this goal, NASA officials first had to decide how to get to the Moon. Eventually NASA scientists chose a lunar orbit rendezvous method, and consequently astronauts practiced rendezvous and docking techniques as part of the Gemini Program, a series of increasingly demanding missions with a two-person spacecraft. The Gemini missions had three phases. In the earliest missions, which began in 1965, astronauts tested the spaceworthiness of the Gemini spacecraft. They also performed the first American extravehicular activities (EVAs) and made the first-ever use of a personal propulsion unit. The middle Gemini missions, Gemini 4, Gemini 5, and Gemini 7, explored human endurance in space by progressively extending stays to two weeks, the maximum time that an Apollo lunar trip was expected to take. The final Gemini missions allowed astronauts to master the techniques of chasing a target vehicle and docking with it.

Apollo was the name of the mission to land men on the Moon. Tragically, before its first orbital trial, the Apollo Program came to an abrupt halt when, on January 27, 1967, a fire killed three astronauts, Roger Chaffee, Virgil “Gus” Grissom, and Edward White, in the Command Module (CM) during a countdown exercise. The spacecraft had a pure oxygen atmosphere and much flammable material, and a spark caused by an electrical short circuit ignited flames that rapidly engulfed the astronauts, who died of asphyxiation. Until the fire, the Apollo Program had proceeded without major difficulties, but these deaths delayed the first missions. NASA scientists redesigned the CM by minimizing flammable materials and changing the prelaunch cabin atmosphere to a mixture of 60 percent oxygen and 40 percent nitrogen.

The success of the Apollo missions depended on the gigantic Saturn V rocket that had been developed by Wernher von Braun. The initial missions in the Apollo series were uncrewed tests of the Saturn and CM engines. For example, on April 4, 1968, the CM and the Lunar Module (LM) were tested on Apollo 8. The first crewed test, which began on October 11, 1968, was Apollo 7, the objective of which was to test the safety and reliability of all the spacecraft’s systems. The first spaceflight involving humans leaving Earth orbit and traveling to the Moon was Apollo 8. This flight began on December 21, 1968, and the spacecraft went into lunar orbit on December 24, when the astronauts described the Moon’s surface and read a passage from the first book of the Bible. The Apollo 9 mission in March, 1969, tested the Command and Service Module (CSM) and the LM in Earth orbit, and the Apollo 10 mission in May tested the CSM and LM in a lunar orbit.

Apollo 11, the lunar landing mission, took place between July 16 and July 24, 1969. On July 20, Neil Armstrong, after adeptly piloting the LM to its destination, became the first person to step onto the surface of the Moon, and he was later joined by Edwin “Buzz” Aldrin. Armstrong and Aldrin spent about two and one-half hours collecting rocks and setting up scientific experiments. Several hours later, their capsule, the Eagle, rocketed from the Moon to rendezvous with the CSM, the Columbia, which was piloted by Michael Collins. All three astronauts returned safely to Earth, where they received a jubilant reception.

From 1969 through 1972, six other Apollo missions traveled to the Moon, although Apollo 13 was unable to land on the lunar surface because of an explosion in one of its oxygen tanks. The Apollo 13 crew had to use the life-support systems of the LM Aquarius to help them survive the long trip back to Earth. NASA engineers consequently redesigned the oxygen tanks, and the final four Apollo lunar missions were able to explore the Moon safely and extensively. The hundreds of pounds of Moon rocks that were returned to Earth have given scientists a deep understanding of the origin and evolution both of the Moon and of the entire solar system.

Spaceflight After Apollo

Travel to the Moon was a risky and expensive enterprise, and neither the United States nor the Soviet Union made the trip in the 1980’s and 1990 s. Critics of crewed spaceflight pointed out that science was much better and more inexpensively served by space satellites and probes. In the three decades after Apollo, robotic explorers such as Viking, Voyager, and Galileo proved to be highly efficient knowledge-gatherers. In 1976, two Viking spacecraft arrived at Mars: an orbiter that photographed the planet from above and a lander that analyzed rocks on the surface.

In 1977, two Voyagers were launched by NASA to start their twelve-year journey to the outer reaches of the solar system. The scientific instruments and cameras on the Voyagers sent back highly detailed information about the giant planets of Jupiter, Saturn, Uranus, and Neptune, along with the planets’ fifty-seven moons. Voyager highlights included dramatic pictures of the turbulent storms of Jupiter’s complex atmosphere, revelations of the complexities of Saturn’s many rings, active volcanoes on Jupiter’s moon Io, Neptune’s Great Dark Spot, and nitrogen geysers on Neptune’s moon Triton.

In 1997, Galileo became the first spacecraft to orbit an outer planet, and it has gathered much useful information about Jupiter’s moons. The Soviets, too, used robotic probes in their scientific studies of the solar system. For example, in 1975, Venera 9 landed on the surface of Venus and returned the first pictures of its rocks and soil.

These uncrewed missions did not mean the end of crewed explorations of space. In 1971, Soviet scientists launched Salyut, the world’s first space station. The Americans later launched their own space station, Skylab, which was visited by three-person crews in the 1970’s, during which time astronauts made detailed studies of Earth’s continents, oceans, and atmosphere. In 1975, the United States and the Soviet Union cooperated in the first international docking in space, when astronauts and cosmonauts performed an orbital rendezvous between an Apollo and a Soyuz capsule.

To make crewed spaceflight less expensive and more frequent, NASA developed the Space Transportation System (STS), commonly known as the space shuttle. Because landings at airfields are much less expensive than splashdowns at sea, and because it makes economic sense to reuse rockets, NASA engineers designed the space shuttle as a winged vehicle that was launched as a rocket, with two recoverable rocket boosters, and landed as an airplane.

In 1981, the space shuttle Columbia made its first flight. The other orbiting space shuttles of the 1980’s and 1990’s were Challenger, Atlantis, and Discovery. The missions of these shuttles included launching artificial satellites and retrieving them for servicing and repairs; performing scientific experiments in space; conducting secret military missions; and launching commercial communication satellites.

Despite NASA’s aim for routine trips to space, the shuttle was plagued with problems, most notably the Challenger explosion on January 28, 1986. All seven crew members, including Sharon Christa McAuliffe, a New Hampshire schoolteacher, were killed. NASA stopped all shuttle missions while a special commission appointed by President Ronald Reagan studied the accident in order to determine the cause of the accident and the prevention of future such tragedies. The cause was a failure of a rubber ring that sealed the joint between two segments of one of the rocket boosters. To prevent any recurrence of this disaster, NASA engineers redesigned the booster joints and added a bailout system that improved chances for crew survival in a crisis. The space shuttle resumed flying on September 28, 1988, with the liftoff of a redesigned Discovery.

One of the successes of the revamped STS was the Hubble Space Telescope (HST), which was launched from an orbiting shuttle in 1990. The HST was an uncrewed observatory far above the atmosphere of the earth, whose haze, clouds, and turbulence hampered telescopes on the ground. Unfortunately, after the HST was in orbit, astronomers discovered a problem with its mirror that seriously hindered its effectiveness. A shuttle repair mission in 1993 helped the HST achieve its astronomical potential. The HST was then able to take dramatic photographs of star births in the Eagle nebula and of galaxies 10,000,000,000 light-years away. It also measured an unimaginably gigantic burst of gamma rays in a distant galaxy that is the most powerful explosion ever observed.

The 1980’s and 1990’s were also characterized by an increasing number of spaceflights from countries other than the United States. On February 20, 1986, the Soviets launched the large Mir Space Station, which remained in orbit until 2001, when it was manipulated to fall harmlessly into the Pacific Ocean. During Mir’s fifteen-year existence, cosmonauts set endurance records and learned much about how humans can live for long periods in space. After the Soviet Union ceased to exist in 1991, Russia took over the operation of Mir. Space cooperation between America and Russia resumed in 1995, when the space shuttle began to dock with Mir, which was periodically occupied by astronauts from various countries, including the United States.

With the end of Mir, crewed spaceflight centered on the International Space Station (ISS). The idea behind ISS was to share among several nations the cost of the construction and operation of a large space station. However, the structure and timetable of the ISS was continually changed during the presidencies of Ronald Reagan and Bill Clinton. The United States, Canada, Japan, Russia, and the European Space Agency (ESA) agreed to cooperate in building the redesigned ISS, whose construction actually began in outer space in 1998. The completed space station, planned to be the size of a football field, is the focus of spaceflights in the twenty-first century.

The participation of several nations in ISS was but another indication of the increasing involvement in spaceflight of countries around the world. Although the United States and the Soviet Union monopolized the early history of spaceflight, France launched its first satellite in 1965, and Britain its first in 1971. Fourteen nations founded the ESA in 1975 to combine their economic and scientific resources to develop new spacecraft for various missions. One of ESA’s achievements was the space probe Giotto, sent to study Halley’s comet in 1986. Japan also sent a probe to Halley’s comet, and the nation’s Advanced Earth Observing Satellite, launched in 1995, has gathered important information on Earth’s lands, seas, and atmosphere. Other nations that have become actively involved in spaceflight are China, India, Canada, Israel, Australia, Brazil, Sweden, and South Africa.

Another trend of the late twentieth and early twenty-first centuries has been the commercialization of spaceflight. Various communications satellites have proved to be successful moneymakers for several companies. Some companies and governments have begun research on commercial crewed spaceflight, but these efforts have encountered serious difficulties because of the high cost of spaceflight. Similar problems have hindered plans for interplanetary travel, such as a crewed voyage to Mars. Critics of crewed spaceflight argue that it redirects funds from useful uncrewed programs and from important social and medical programs. In contrast, enthusiasts of crewed spaceflight emphasize the dreams that have energized scientists and engineers throughout history and the ineradicable desire to explore other worlds.


  • Burrows, William E. Exploring Space: Voyages in the Solar System and Beyond. New York: Random House, 1990. An account of how rivalries—between the United States and the Soviet Union and between advocates of crewed and uncrewed spaceflight within NASA—drove lunar and planetary explorations.
  • Chaikin, Andrew W. A Man on the Moon: The Voyages of the Apollo Astronauts. New York: Viking Penguin, 1994. The definitive history of the Apollo Program, which put a man on the Moon, with an emphasis on the lives and personalities of the chief participants.
  • McDougall, Walter A. The Heavens and the Earth: A Political History of the Space Age. New York: Basic Books, 1985. A highly praised account of the space race between the United States and the Soviet Union and its lessons about the relationship between technology and social change.
  • Murray, Bruce. Journey into Space: The First Thirty Years of Space Exploration. New York: Norton, 1989. An account of America’s pioneering explorations of the solar system benefits from the insights of its author, director of the Jet Propulsion Laboratory from 1976 to 1983.
  • Neal, Valerie, Cathleen S. Lewis, and Frank N. Winter. Spaceflight: A Smithsonian Guide. New York: Macmillan, 1995. This heavily illustrated manual surveys the history of spaceflight from the dreams of the ancients to the speculations of the futurists.

Aerospace industry, U.S.

Apollo Program

Wernher von Braun

Crewed spaceflight

Gemini Program

Robert H. Goddard


Mercury project

National Advisory Committee for Aeronautics

National Aeronautics and Space Administration





Saturn rockets

Space shuttle


Konstantin Tsiolkovsky

Uncrewed spaceflight

Uninhabited aerial vehicles

Vanguard Program