Space Exploration

Space Exploration

On October 4, 1957, scientists in the Soviet Union (now Russia) listened anxiously for a radio signal. The whole world waited. Then it came, a lonely “Beep Beep Beep” sound. It was the signal from the first spacecraft to be placed in orbit around the Earth—Sputnik 1. The age of space exploration had begun.

HOW DID WE FIRST GO INTO SPACE?

Gravity makes it difficult to send things into space. The Earth’s pull is so great that to get a spacecraft up beyond the atmosphere you need a powerful rocket. When it is in orbit, a spacecraft still feels the pull of gravity towards the Earth.

Small rockets had been used as weapons for centuries, but rocket science became serious during World War II when German scientists developed the V-2 rocket. After the war, many of these scientists went to the United States, while some went to the Soviet Union. These two powerful countries vied with each other to take the first steps into space.

The Soviet Union got there first with Sputnik 1. Sputnik was a tiny satellite, just an aluminium sphere 58 centimetres in diameter. It orbited the Earth for 21 days before re-entering the atmosphere, where it burnt up. The Americans sent up their first satellite, called Explorer 1, on January 31, 1958. Soon, several unmanned craft had been sent into orbit. By this time, engineers could bring a craft safely back to Earth, too. The next step was to send a human being into space.

This too was first achieved by the Soviet Union. On April 12, 1961, the cosmonaut (that is what Russians call astronauts) Yuri Gagarin made one orbit of the Earth in his spacecraft, Vostok 1. Just a month afterwards, Alan Shepard, Jr., became the first American astronaut in space, but his short flight did not take him into orbit. The first American to orbit the Earth was John Glenn, Jr., in 1962.

The first woman in space followed soon after. Cosmonaut Valentina Tereshkova went up into space on June 16, 1963. She made 48 orbits of the Earth.

Human beings could clearly survive in space. The next challenge was to reach the Moon.

WHEN DID WE FIRST GO TO THE MOON?

The first unmanned missions to the Moon followed soon after, with the Soviet Union’s Luna 2 spacecraft crash landing on the lunar surface in 1959.

With the Soviet Union beating them into space, the Americans were determined to be first to put a man on the Moon. The early Gemini and Apollo missions were rehearsals for the big event. Apollo 11 was launched on July 16, 1969.

On July 20, 1969, a small figure in a big space suit climbed down the short ladder of the lunar landing module Eagle on to the lunar surface. His name was Neil Armstrong. As he took the first human step on another world, he said: “That’s one small step for man; one giant leap for mankind.” His fellow astronaut, Edwin “Buzz” Aldrin, followed him. All over the world, millions of people watched the historic moment live on television.

Soon, other astronauts followed in Apollos 12, 14, 15, 16 and 17. Apart from Apollo 13, which was forced to turn back without landing because of problems on the spacecraft, the missions were a great success. The astronauts did many experiments, and the Apollo 15 astronauts were the first to drive on the lunar surface, in a special four-wheeled jeep or lunar rover.

WHAT TYPES OF ROCKETS AND SPACECRAFT DO WE USE?

Manned missions are exciting and a great achievement for humankind. But they are very expensive and risky. Unmanned spacecraft need not carry air and water, and need not come back to Earth. Manned spacecraft are rather heavier and more difficult to design. Inside, there must be food, a good supply of air and living and sleeping accommodation for the astronauts. The outside of the spacecraft must have a heat shield to protect the insides from heating up as the spacecraft re-enters the atmosphere.

The Apollo missions were launched by the massive Saturn V rocket, which used liquid fuel. The rocket had separate stages, and each stage would fall away as its fuel was used up.

All the early American spacecraft landed in the ocean, while the Soviet spacecraft landed on solid ground. From the early 1980s, NASA (National Aeronautics and Space Administration) began to use the space shuttle to launch spacecraft. Unlike the Saturn V rockets, the space shuttle was a “spaceplane”, which could launch satellites and then return, making a powered landing like an ordinary aeroplane. Space shuttles have launched many missions since then. They have also been used to collect and repair faulty spacecraft. But in 1986, seven astronauts, including Christa McAuliffe, who was hoping to be the first schoolteacher in space, died when the space shuttle Challenger broke up soon after take-off.

WHICH PLANETS HAVE WE VISITED?

It was not long before spacecraft were sent to our nearby planets, in the inner part of the solar system. Venus was an important target and Soviet Venera and American Mariner spacecraft flew past it in the early 1960s. Other missions have followed, landing on the very hot surface and mapping it with radar. Mercury has only been visited by NASA’s Mariner 10, which flew past in 1974-1975.

Of the inner planets, the most important for exploration and the hope of finding life has been Mars. Many missions have been sent to it, with the first landings by Vikings 1 and 2 in 1976. Mars has been carefully mapped, and the Mars Pathfinder mission, which reached the planet in 1997, was the first to carry a little robot rover that wandered around the surface near the landing craft, studying the soil and rocks. No signs of life have been found so far, but in 2004 the robot rover Opportunity found evidence that there had once been water on the surface. This is an exciting discovery because it means there may have been life too. More missions are planned.

As well as the planets, spacecraft have also visited asteroids, and the European Space Agency’s Giotto probe was one of several that took close up pictures of Halley’s Comet on its last visit to the Sun in 1986.

HAVE WE VISITED THE OUTER PLANETS?

Beyond Mars, and past the asteroid belt, like the big gas giants of Jupiter, Saturn, Uranus, and Neptune. They have all now been visited by spacecraft.

The first spacecraft to visit Jupiter was Pioneer 10 and Pioneer 11 in 1973 and 1974. Pioneer 11 then went on to fly past Saturn in 1979. Both spacecraft are now on their way out of the solar system.

Even more successful were the Voyager missions. Voyagers 1 and 2 were launched in 1977 and reached Jupiter two years later. Both spacecraft sent back spectacular detailed views of the planet’s atmosphere before going on to Saturn. Voyager 1 flew close to Saturn’s big moon Titan before going off towards the edge of the solar system.

Voyager 2 headed towards Uranus, sending back the first close-up views of this unusual planet in 1986. With all its instruments still working, it then became the first spacecraft to visit the last of the gas giants, Neptune, in 1989. It too is now heading out into deep space. After 26 years in space, both Voyagers are still sending back information. They are the first to explore these farthest reaches of our solar system.

Since the visits of Pioneer and Voyager, Jupiter has been studied in great detail by another spacecraft, Galileo. It spent eight years orbiting Jupiter and sending back lots of intriguing data about the planet and its biggest moons.

There are lots more missions planned, including one to the dwarf planet Pluto, and preparations are being made to send astronauts to Mars. It may be a while before that happens. In the meantime, astronauts living in space stations in orbit around the Earth can help scientists learn what problems human beings might have on long space flights.

WHAT IS A SPACE STATION?

A space station can keep orbiting the Earth while different spacecraft are sent up to dock with it, perhaps carrying a crew of several astronauts who stay at the station for a few months before returning to Earth on their spacecraft. It is a good way for astronauts to spend some time in space, doing detailed experiments.

The first space stations, called Salyut, were launched by the Soviet Union in the 1970s. Cosmonauts from many countries, including Britain, Cuba and India, visited the Salyut space stations. The Americans launched Skylab in 1973, and the Soviet Mir space station remained in space for 13 years.

The United States and Russia have worked together to build the International Space Station, together with the European Space Agency, Canada, Japan, and Brazil. Its first module was sent up by the Russians in 1998, and other modules have been added since. Different crews of astronauts have lived in the space station since 2000.

WHY DO WE USE SPACE OBSERVATORIES?

There are now several satellites in orbit about the Earth carrying telescopes and other kinds of detectors for studying the universe. Many kinds of radiation, like X-rays and ultraviolet, are blocked by the Earth’s atmosphere, and can only be studied from space.

Space observatories have been very successful. The Hubble Space Telescope, launched in 1990, has given us amazing pictures of stars forming inside gas clouds and distant galaxies.

Human beings have taken their first steps beyond our home planet. We are going further and seeing farther than ever before. That first “beep Beep beep” of Sputnik 1 already seems remote, as though it belonged to a bygone age.

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