During this period the United States launched its only true space station. Called Skylab, it was placed in orbit in May, 1973. Skylab housed three three-person crews, the last remaining aboard for 84 days, which at that time was a record for continuous residency in space. Among the tasks accomplished by the Skylab astronauts were biomedical studies to evaluate the effects of weightlessness, photographing the earth to monitor volcanoes and earthquake faults, astronomical observations of optical sources (including extensive studies of Comet Kohoutek), and materials-processing activities such as brazing and welding (to see how they were affected by the lack of gravity). Skylab fell to earth in July, 1979, showering debris over uninhabited parts of Australia and the Indian Ocean.
The Soviet Union launched the core module of the Mir space station in Feb., 1986. It was enlarged several times so that it could accommodate a crew of up to six cosmonauts. The Mir program was enhanced by having international teams conduct experiments at the station; Afghanistan, Bulgaria, France, Germany, Great Britain, India, Japan, Syria and the United States, in addition to Russia and other nations that were formerly part of the Soviet Union, participated. In 1995, Mir cosmonaut Valery Polyakov set an endurance record of nearly 439 days in space, eclipsing the previous record of 326 days set in 1987 by Yuri Romanenko (also while on Mir). In Aug., 1999, its extended 13-year mission concluded, Mir was abandoned. During its lifetime, it orbited the earth 86,331 times and was home to 104 people, including 42 Russian cosmonauts and 7 American astronauts. In Mar., 2001, Mir fell to earth, the largest spacecraft (143 tons/130 metric tons) ever to decay, showering an estimated 1,500 fragments of 44 lb (20 kg) or more over an uninhabited area 120 mi (193 km) wide by 3,600 mi (5795 km) long in the South Pacific.
The United States, Japan, Canada, Brazil, Russia, and members of the European Space Agency (ESA) have contributed to the development of the International Space Station (ISS), which has been assembled in space since 1998. Each partner has contributed a portion of the complex. The first element, Zarya (the control module), was orbited by a Russian Proton rocket in Nov., 1998. A month later the U.S. space shuttle Endeavour initiated the first assembly sequence of the ISS, linking the Unity module, a passageway that connects living and work areas of the station, to Zarya. In July, 2000, the Russian-built Zvezda service module was mated with the two existing components. The first permanent crew—two Russian cosmonauts and an American astronaut—began living aboard the ISS in Nov., 2000; it now supports a crew of up to seven. The ISS with its modules and solar arrays now spans 357.5 ft by 167.3 ft (109 m by 51 m), or roughly the size of the U.S. football field; its mass is nearly a million pounds (454,000 kg). Its construction has involved more than 110 space flights by five space vehicles (including the space shuttle, the Russian Soyuz rocket, and the Russian Proton rocket) to deliver the various ISS components to earth orbit. Assembly of the more than 100 components has utilized a combination of human spacewalks and robot technologies. Components added since 2000 include the Destiny Laboratory (2001, United States), Pirs Docking Compartment (2001, Russia), and Columbus laboratory (2008, ESA). The station's fourth and final set of solar panels was erected in 2009. The ISS has been resupplied by European, Japanese, Russian, and U.S. spaceflights.
In Sept., 2011, China placed Tiangong 1 [heavenly palace], an experimental prototype space station, in orbit, and it was subsequently visited (2011–13) by three spaceflights (Shenzhou 8–10), the last two of which had crews; all three Shenzhou spacecraft docked with Tiangong 1. Tiangong 2, a second experimental space station designed as a testing laboratory and precursor to a more permanent space station, was launched in Sept., 2016. The following month, Shenzhou 11 docked with the station for a monthlong mission.
See P. Bizony, Island in the Sky: The ISS (1996); D. M. Harland, The Mir Space Station: Precursor to Space Colonization (1997); M. D. Cole, International Space Station: A Space Mission (1999).
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