Space exploration

2007 Schools Wikipedia Selection. Related subjects: Engineering; Space transport

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 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.

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. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were 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 Centre 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.

	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.
—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 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

1942-1975

Date	First Success	Country	Mission Name
1944	Rocket to reach 100km ( boundary to space)	Nazi Germany	V2 rocket, military program
July 1946	Animals in space (fruit flies)	USA-ABMA	V2
August 21, 1957	Intercontinental ballistic missile (ICBM)	USSR	R-7 Semyorka/SS-6 Sapwood
October 4, 1957	Artificial satellite Signals from space	USSR	Sputnik 1
November 3, 1957	Animal in orbit (dog)	USSR	Sputnik 2
January 31, 1958	Detection of Van Allen belts	USA-ABMA	Explorer I
December 18, 1958	Communications satellite	USA-ABMA	Project SCORE
January 2, 1959	Firing of a rocket in Earth orbit Reaching escape velocity Detection of solar wind	USSR	Luna 1
January 4, 1959	Orbit around the Sun	USSR	Luna 1
February 17, 1959	Weather satellite	USA-NASA ( NRL)¹	Vanguard 2
August 7, 1959	Photo of Earth from space	USA-NASA	Explorer 6
September 13, 1959	Landing on another world (the Moon)	USSR	Luna 2
October 4, 1959	Photos of far side of the Moon	USSR	Luna 3
August 18, 1960	Reconnaissance satellite	USA-Air Force	KH-1 9009
1961	Launch from orbit Mid-course corrections Spin-stabilisation Venus fly-by	USSR	Venera 1
April 12, 1961	Human in space Human in orbit	USSR	Vostok 1
November 1, 1962	Mars flyby	USSR	Mars 1
June 16, 1963	Woman in space	USSR	Vostok 6
July 19, 1963	Reusable Manned Spacecraft (suborbital)	USA-NASA	X-15 Flight 90
October 12, 1964	Multi-man crew (3)	USSR	Voskhod 1
March 18, 1965	Extra-vehicular activity	USSR	Voskhod 2
April 6, 1965	Commercial communications satellite	Intelsat	Intelsat 1
December 15, 1965	Orbital rendezvous (parallel flight, no docking)	USA-NASA	Gemini 6A/ Gemini 7
February 3, 1966	Soft landing on another world (the Moon) Photos from another world	USSR	Luna 9
March 1, 1966	Landing on another planet (Venus)	USSR	Venera 3
April 3, 1966	Artificial satellite around another world (the Moon)	USSR	Luna 10
April 23, 1967	Spaceflight casualty	USSR	Soyuz 1
October 30, 1967	Unmanned rendezvous with docking	USSR	Cosmos 186/ Cosmos 188
January 16, 1969	Manned docking and exchange of crew	USSR	Soyuz 4/ Soyuz 5
July 21, 1969	Human on the Moon	USA-NASA	Apollo 11
September 24, 1970	Automatic sample return from the Moon	USSR	Luna 16
November 23, 1970	Lunar rover	USSR	Lunokhod 1
December 15, 1970	Soft landing on another planet (Venus) Signals from another planet	USSR	Venera 7
April 23, 1971	Space station	USSR	Salyut 1
December 1971	Orbit around Mars	USSR	Mars 2
November 27, 1971	Mars landing	USSR	Mars 2
December 2, 1971	Soft Mars landing signals from Mars surface	USSR	Mars 2
July 15, 1975	Multinational manned mission	USSR USA-NASA	Apollo-Soyuz Test Project
October 20, 1975	Orbit around another planet (Venus)	USSR	Venera 9
October 22, 1975	Photos from the surface of another planet (Venus)	USSR	Venera 9

¹Project Vanguard was transferred from the NRL to NASA immediately before launch.

Post-1975

Date	First Success	Country	Mission Name
March 2, 1978	Non-American and non-Soviet in space	USSR Czechoslovakia	Soyuz 28
April 12, 1981	Reusable manned spacecraft (orbital)	USA-NASA	Columbia
March 1, 1982	Venus soil samples & sound recording of another world	USSR	Venera 13
June 13, 1983	Spacecraft beyond the orbit of Neptune	USA-NASA	Pioneer 10
July 25, 1984	Extra-vehicular activity by a woman	USSR	Salyut 7
December 2, 1990	Commercial manned-spaceflight	USSR Japan	Soyuz TM-11
July 7, 1998	Submarine-launched spacecraft	Russia	K-407
April 28, 2001	Space tourist	Russia USA	Soyuz TM-32
October 15, 2003	Third nation to achieve manned spaceflight	China	Shenzhou 5
June 21, 2004	Private human spaceflight / spacecraft (suborbital)	USA-MAV	SpaceShipOne 15P

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

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

The first partially 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 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.

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.