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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 millenia. 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 5, 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 Alexei 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. 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 2 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. First human in space 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 milestone date is celebrated as Cosmonautics Day (Space Day). 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. 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: 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. 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 counter-argued that 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, 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 point out 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 ideas about in orbit assemblies, and argues for a direct approach for human settlement of Mars called Mars Direct. Timeline of space exploration , Timeline of solar system exploration, Timeline of artificial satellites and space probes, Spaceflight records 1942-1975 1Project Vanguard was transferred from the NRL to NASA immediately before launch. Post-1975 In addition, virtually all manned duration records have been set by the USSR, due largely to their Salyut/Mir series of space stations. Reusable spacecraft
Space colonization Space colonization, also called space settlement and space humanization, is the permanent autonomous (self-sufficient) human habitation of locations outside Earth, specially in natural satellites or planets (Moon, Mars...). 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 See also Unmanned missions Main article: Unmanned space mission Animals in space Humans in space Main articles: Astronauts and human spaceflight Recent and future developments Other National agencies Other | |||||||||
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