Space exploration

Sputnik
Buzz Aldrin
(From TOP to BOTTOM)
- First man-made satellite in space Sputnik 1;
- First human being in space Yuri Gagarin;
- Astronaut Buzz Aldrin on the surface of the Moon. The Moon is currently the only extraterrestrial object that humans have walked upon.

Space exploration is the physical exploration of outer space by both manned and unmanned spacecraft. The development of large liquid-fueled rocket engines during the early 20th century allowed space exploration to become a practical possibility; it is distinct from the earth-based observation of outer space, known as astronomy, which has occurred for millennia. Common rationales for the pursuit of space exploration include advancing scientific research and ensuring the future survival of humanity. Significant political and ethical questions surround space exploration, and it has often been used as a proxy competition for geopolitical rivalries such as the Cold War.

The early era of space exploration was driven by a space race between the Soviet Union and the United States; the launch of the first man-made object to orbit the Earth, the USSR's Sputnik 1, on October 4, 1957, and the first Moon landing by the American Apollo 11 craft on July 20, 1969 are often taken as the boundary for this initial period. The Soviet Union achieved many of the first milestones, including putting the first man in space, Yuri Gagarin aboard Vostok 1 in 1961, and completing the first spacewalk (by Aleksei Leonov in 1965). In 1971, the Soviets launched the first space station, Salyut 1.

After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station. From the 1990s onwards, private interests began promoting space tourism. Larger government programs have advocated manned missions to the Moon and possibly Mars sometime after 2010.

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First orbital flights

The first successful orbital launch was of the Soviet unmanned Sputnik I mission on October 4, 1957. The satellite weighed about 83 kg (184 pounds), and is believed to have orbited Earth at a height of about 250 km (150 miles). It had two radio transmitters (20 and 40 MHz), which emitted "beeps" that could be heard by any radio around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It incinerated upon re-entry on January 3, 1958.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch Vanguard 1 into orbit two months later. On January 31, 1958, the US successfully orbited Explorer I on a Juno rocket. In the meantime, the Soviet dog Laika became the first animal in orbit on November 3, 1957.

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First human in space

Yuri Gagarin
Yuri Gagarin

The first manned spaceflight was Vostok 1, carrying 27 year old cosmonaut Yuri Gagarin on the historic date April 12, 1961. The spacecraft completed one orbit around the globe, which lasted about 1 h 48 min. Currently this Gagarin's flight resonated around the globe not only showing the then-superiority of the Soviet space program but opening an entirely new era in space exploration - manned space flights. The U.S. would launch its first man into space within a month of Gagarin's flight with the first Mercury flight, by Alan Shepard. However, orbital flight was not achieved until John Glenn's flight nearly a year later. China would launch its first taikonaut into space 42 years later, with the flight of Colonel Yang Liwei aboard the Shenzhou 5 spacecraft.

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Key people in early space exploration

The dream of stepping into the outer reaches of the Earth's atmosphere was driven by rocket technology. The German V2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for inter-continental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when USSR launched the first man into space, the US declared itself to be in a "Space Race" with Russia.

Other key people included:

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Criticisms

It is more expensive to perform certain tasks in space with humans rather than by robots or machines. Humans need large spacecraft that contain provisions such as a hermetic and temperature controlled cabin, production of breathable air, food and drink storage, waste disposal, voice- and other communication systems, and safety features such as crew escape systems, medical facilities, etc. There is also the question of the security of the spacecraft as whole; losing a robot is nowhere near as dramatic as human loss, so overall safety of non-human missions isn't as much of an issue. All of these extra expenses have to be weighed against the value of having humans aboard. Some critics argue that those few instances where human intervention is essential do not justify the enormous extra costs of having humans aboard.

   
Space exploration
Twenty-first-century space advocates continue to dream about winged spaceships, rotating space stations, lunar bases, and colonies on Mars. Some of these visions will come true. To a large extent, however, the motivating visions rest on a foundation made of sand.... Space exploration is not the twenty-first-century equivalent of the Oregon Trail, certainly not in the romantic manner that modern people remember that episode.
   
Space exploration

—Roger D. Launius & Howard E. McCurdy, Imagining Space

Other critics, such as the late physicist and Nobel-prize winner Richard Feynman, have contended that space travel has never achieved any major scientific breakthroughs. However, others have counter-argued that, besides the large (and otherwise unavailable) amount of planetary data returned by spacecraft, there have been many indirect scientific achievements: development of the modern computer, lasers, etc.

Some critics contend that in light of the huge distances in space, human space travel will never be able to do more than achieve an earth orbit or at best visit our closest neighbours in the solar system--barring any advances in the at present purely theoretical idea of faster-than-light travel--and even this will consume large amounts of money and will require complex spacecraft that will accommodate only a handful of people. Supporters of human space travel state that this is irrelevant, because its real value lies in providing a focal point for national prestige and patriotism. They suggest that this was the reason why the Clinton administration cooperated closely with Russia on the International Space Station: it gave Russia something to take pride in, and as such became a stabilizing factor in post-communist Russia. From this point of view, the ISS was a justifiable cash outlay.

Some people also have moral objections to the huge costs of space travel, and say that even a fraction of the space travel budget would make a huge difference in fighting disease and hunger in the world. However, compared to much more costly endeavors, like military actions, space exploration itself receives a very small percentage of total government spending (nearly always under 0.5%).

Overall, the public remains largely supportive of both manned and unmanned space exploration. According to an Associated Press Poll conducted in July 2003, 71% of US citizens agreed with the statement that the space program is "a good investment", compared to 21% who did not (Pollingreport.com).

Some supporters of space explorations, such as Robert Zubrin, have criticized on-orbit assembly of spacecraft, and argue for a direct approach for human exploration, such as Mars Direct.

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Reusable spacecraft

The Space Shuttle Columbia seconds after engine ignition, 12 April 1981 (NASA)
The Space Shuttle Columbia seconds after engine ignition, 12 April 1981 (NASA)

The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963. The first partially reusable orbital spacecraft, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the Challenger, Discovery, Atlantis, and Endeavour. The Endeavour was built to replace the Challenger when it was lost in January 1986. The Columbia broke up during reentry in February 2003.

The first (and so far only) automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the U.S. Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran.

Per the Vision for Space Exploration, the Space Shuttle is due to be retired in 2010 due mainly to its old age and high cost of program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2014. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.

Scaled Composites SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company will build its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic should begin reusable private spaceflight carrying paying passengers in 2008.

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Space colonization

Space colonization, also called space settlement and space humanization, is the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets (Moon, Mars...).

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Space agencies

While only the United States, Soviet Union/Russian and Chinese space programs have launched humans into orbit, a number of other countries have space agencies which design and launch satellites, conduct space research and coordinate national astronaut programs. In Europe, the European Space Agency serves several nations. Several nations have launched their own satellites including India, Japan and France.

See also List of space agencies

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Gallery

Here are pictures of some space exploration firsts

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See also

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Unmanned missions

Main article: Unmanned space mission

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Animals in space

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Humans in space

Main articles: Astronauts and human spaceflight

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Recent and future developments

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Timelines

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Other

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External links

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National agencies

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Other

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