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Space exploration is the physical exploration of outer space. The politics, science, and engineering behind space flight all fall under the auspices of space exploration. There are many rationales behind space exploration; among the most common are ones focusing on scientific research or the future survival of humanity. This endeavour has been to some degree a dream and goal of humanity for the past several centuries, but it was not until the development of large liquid-fueled rocket engines during the early 20th century that it really began to be seriously developed.

The first major milestone of this endeavour was the launch of the USSR's Sputnik 1 on October 5, 1957, the first man-made object to orbit the Earth. After this event, the USA declared itself to be in a space race with the Soviet Union. Major achievements of the first era of space exploration (which lasted until 1969) were putting the first man in space, (Yuri Gagarin aboard Vostok 1) on April 12, 1961 (again by the USSR), the first spacewalk (by Alexei Leonov, also a Soviet cosmonaut) in 1965, and the first Moon landing by Neil Armstrong and Buzz Aldrin aboard Apollo 11 on July 20, 1969 (by the USA). The next notable achievement in space was the launch of first space station, Salyut 1, from the USSR. After the first 20 years of exploration, focus began shifting from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as on the International Space Station. Recently, private interests have begun pushing space tourism, while larger government programs have been advocating a return to the Moon and possibly missions to Mars in the near future.

Reaching space

The most commonly used definition of space, at least from the perspective of spacecraft, is everything more than 100km (60 mi) above the Earth's surface. The United States sometimes uses a 50 mile definition. (See boundary to space.)

One can distinguish between sub-orbital spaceflight and the orbital spaceflight (cf. Difference between sub-orbital and orbital spaceflights). For sub-orbital flights, on October 3, 1942 a German A4 rocket (a prototype for the V2 rocket used to bomb London), became the first successful launch of an object into space. The first organisms launched into space were bacteria trapped aboard the same flight. Another milestone was achieved on May 17, 2004 when Civilian Space eXploration Team launched the GoFast Rocket on a suborbital flight, the first amateur space flight. On June 21, 2004, SpaceShipOne became the first privately-funded manned spacecraft.

Achieving orbit is not essential for manned or unmanned interplanetary voyages. Early Russian space vehicles successfully achieved very high altitudes without going into orbit. The early Apollo mission planning also considered using a direct ascent to the moon, but abandoned that idea later due to weight considerations. Many unmanned space probes to the outer planets use direct ascent -- they do not orbit the earth before departing.

However, plans for future manned exploration often include final vehicle assembly in earth orbit.

Because suborbital space flights are by definition short (less than 1.7 hours) any longer mission requires orbital flight (with elliptical or circular trajectory), or superorbital flight (over parabolic or hyperbolic trajectory). However, orbital flight requires much higher velocities than suborbital making it technologically challenging to achieve.

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 emmited "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. In February of 1958, the US successfully orbited Explorer 1 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.

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.

  • Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth and Reinhold Tilling laid the groundwork of rocketry in the early years of the 20th century.
  • Wernher von Braun was the lead rocket engineer for Nazi Germany's World War II V-2 rocket project. After the war he was captured and brought to the USA to work on U.S. rocket development. He acquired American citizenship and led the team that developed and launched Explorer I, the first American satellite. Von Braun later led the team at NASA's Marshall Space Flight Center which developed the Saturn V moon rocket.
  • Initially the race for space was often led by Sergei Korolev, whose legacy includes both the R7 and Soyuz - which remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Russian space program.

Other key people included:

  • Valentin Glushko held role of Chief Engine Designer for USSR. Glushko designed many of the engines used on the early Soviet rockets, but was constantly at odds with Korolev.
  • Vasily Mishin, Chief Designer working under Sergei Korolev and one of first Soviets to inspect the captured German V2 design. Following the death of Sergei Korolev, Mishin was held responsible for the Soviet failure to be first country to place a man on the moon.
  • Bob Gilruth, was the NASA head of the Space Task Force and director of 25 manned space flights. Gilruth was the person who suggested to John F. Kennedy that the Americans take the bold step of reaching the Moon in an attempt to reclaim space superiority from the Soviets.
  • Christopher C. Kraft, Jr., was NASA's first flight director and oversaw development of Mission Control and associated technologies and procedures.

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, 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 planetary exploration, Timeline of solar system exploration, Timeline of artificial satellites and space probes, Spaceflight records

1942-1975

Nazi GermanyUSAUSSR USSR USSR USA-ABMA USA-ABMA USSR USA-NASA (NRL)1 USA-NASA USSR USA-Air Force USSR USSR USSR USSR USA-NASA USSR USA-NASA USSR USSR USSR Flag of the United States.svg USA-NASA
Date First Success Country Mission Name
October 3, 1942 Rocket to reach 80 km V2 rocket, military program
July 1946 Animals in space (fruit flies) V2
August 21, 1957 Intercontinental ballistic missile (ICBM) R-7 Semyorka/SS-6 Sapwood
October 4, 1957 Artificial satellite Sputnik 1
November 3, 1957 Animal in orbit (dog) Sputnik 2
January 31, 1958 Detection of Van Allen belts Explorer I
December 18, 1958 Communications satellite Project SCORE
September 14, 1959 Probe to Moon Luna 2
February 17, 1959 Weather satellite Vanguard 2
August 7, 1959 Photo of Earth from space Explorer 6
October 4, 1959 Photo of far side of the Moon Luna 3
August 18, 1960 Reconnaissance satellite KH-1 9009
April 12, 1961 Human in orbit Vostok 1
November 1, 1962 Mars flyby Mars 1
June 16, 1963 Woman in space Vostok 6
March 18, 1965 Extra-vehicular activity Voskhod 2
December 15, 1965 Orbital rendezvous Gemini 6A/Gemini 7
March 1, 1966 Probe to another planet Venera 3
July 21, 1969 Human on the Moon Apollo 11
December 15, 1970 Landing on another planet Venera 7
April 23, 1971 Space station Salyut 1
July 15, 1975 U.S.-USSR joint mission Apollo-Soyuz Test Project
1Project Vanguard was transferred from the NRL to NASA immediately before launch.

Post-1975

USSR USA-NASA USA-NASA RussiaFlag of Japan.svg Japan RussiaUSA-MAV

Date First Success Country Mission Name
October 2 1978 Non-American and non-Soviet in space Soyuz 28
April 12 1981 Reusable manned spacecraft STS-1
June 13 1983 Pioneer 10
December 2 1990 Space tourist Soyuz TM-11
July 7 1998 Submarine-launched spacecraft K-407
June 21 2004 SpaceShipOne 15P

Reusable spacecraft

The first partially reusable 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 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 orbiter Atlantis (Space Shuttle) may be retired as early as 2008. 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.

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

External links

Space exploration

Exploració espacial | Rumfart | Raumfahrt | Kosmoseuurimine | Exploración espacial | Kosmoesploro | Conquête de l'espace | Romtefeart | 우주 탐사 | Penjelajahan angkasa | Űrkutatás | Ruimtevaart | 宇宙開発 | Romfart | Podbój kosmosu | Exploração espacial | Космонавтика | Rymdfart | Космонавтика | 太空探索

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Space exploration".

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