Space flights
Author: Bartosz Rychlak
Space exploration is the physical exploration of outer space, both by human spaceflights and by robotic 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, uniting different nations and ensuring the future survival of humanity.
Space exploration 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 boundaries 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.
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 Explorer 1 into orbit two months later. On March 17, 1958, the US successfully orbited Vanguard I. In the meantime, the Soviet dog Laika became the first animal in orbit on November 3, 1957.
The first human spaceflight was Vostok 1, carrying 27 year old cosmonaut Yuri Gagarin on April 12, 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin's flight resonated around the world; it was a demonstration of the superior Soviet space program and it opened an entirely new era in space exploration - manned space flights. The U.S. launched 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 by the United States until John Glenn's flight nearly a year later. China launched its first taikonaut into space 42 years later, with the flight of Colonel Yang Liwei aboard the Shenzhou 5 spacecraft.
NASA's Space Shuttle, officially called Space Transportation System (STS), is the United States government's current manned launch vehicle. A total of five usable orbiters were built, of which three remain. The winged shuttle orbiter is launched vertically, usually carrying five to seven astronauts (although eight have been carried and eleven could be accommodated in an emergency) and up to 50,000 lb (22,700 kg) of payload into low earth orbit (the thermosphere). When its mission is complete, it fires its maneuvering thrusters to drop out of orbit and re-enters the Earth's atmosphere. During the descent and landing, the shuttle orbiter acts as a glider and makes a completely unpowered landing.
The Shuttle is the first orbital spacecraft designed for partial reusability. It carries large payloads to various orbits, provides crew rotation for the International Space Station (ISS), and performs servicing missions. The orbiter can also recover satellites and other payloads from orbit and return them to Earth, but this capacity has not been used often. However, it has been used to return large payloads from the ISS to Earth, as the Russian Soyuz spacecraft has limited capacity for return payloads. Each Shuttle was designed for a projected lifespan of 100 launches or 10 years' operational life.
The first orbiter, Enterprise, was not built for actual space flight, and was used only for testing purposes. Enterprise was followed by four operational space shuttles: Columbia, Challenger, Discovery and Atlantis. Challenger was destroyed on launch in 1986, and Endeavour was built as a replacement. Columbia was destroyed on re-entry in 2003.
NASA announced in 2004 that the Space Shuttle will be retired in 2010 and replaced by the Orion, a new vehicle that is designed to take humans to the Moon and beyond.
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