Space Stations, post Apollo direction

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The space station was designed to remain in low Earth orbit as an artificial satellite with crew onboard, to be docked with another spacecraft, and to perform scientific or other experiments.  The first serious reference to a space station was Konstantin Tsiolkovsky in early 20th century. Herman Potočník published The problem of Space Travel in 1929, which was the first vision of rotating wheel to create artificial gravity. For example in 1951, Wernher von Braun published his designed for rotating wheel space station in reference to Potočník's concept. On the other hand Soviets were following Tsiolkovsky's ideas.

First space stations:
Salyut (see Soyuz spacecraft second generation), Almaz, Skylab (see Skylab) (1971 - 1986)

The first space station was Soviet Salyut 1 launched on April 19, 1971. As every space stations in the beginning it was launched as a compact piece with supplies necessary for the crew before it was used by the crew launched separately later. After the station was used up, it was abandoned.

Left: Potočník: space station rotating wheel. Right: Salyut 1 seen from Soyuz 11

Space stations Salyut 2, 3, and 4 were also known as Almaz and they were military stations. Civilian space stations were Salyut 6 and Salyut 7 with two docking ports which allowed to other crew to dock with station leading the station to be permanently manned. Soyuz spacecraft could spend 90 days in space, after which in needed to be switched. Progress supply spacecraft was possible to dock with the second port to bring new stuff for the crew. 

Left: Drawing of Salyut 6 S6 (docked F Soyuz Ferry and P Progress supply cargo). Right: Skylab

 Skylab had also two docking ports, but the second port was never in use. Skylab was also launched unmanned by modified Saturn V rocket. Skylab was visited by 3 missions, each mission consisted of 3 astronauts. The mission was delivered in the Apollo Command/Service Module launched by smaller Saturn IB rocket. 

Next generations of space stations:
Mir (see Mir, see also Shuttle-Mir) (1986-2001) was a new type of space station in low orbit which had a modular design. Mir was also the first space station inhabited continuously and long term research station. 
All modules of the station had specific objective. The first core module was launched in 1986, followed by 6 modules, all launched by Proton rockets except the docking module, which was carried by US Space Shuttle STS-74 in 1995. 

Left: Mir space station. Right: Mir space station docked with US Space Shuttle 

Some planned projects:  
Mir 2 was a space station project which began already in February 1976. Some of modules were built and were used for the International Space Station (ISS). The core module DOS-8 was used as Zvezda module in the ISS. Its design reaches back to Salyut space station. 

Freedom (see Freedom) was planned NASA project in 1980s as a response to Mir space station. However the station was never built and after the successful joint Shuttle - Mir Program (see Shuttle-Mir) the project evolved into the ISS. 

Current missions:
ISS (1998-now) is first joint international project. The first module Zarya was launched in 1998. The ISS is divided into two main parts: the Russian Orbital Segment and the US Orbital Segment. ISS components were launched by Russian Proton and Soyuz rockets and US Space Shuttles. 
US segments were manually attached to the ISS by crew during EVA (extravehicular activity). Manual connections are made for electrical power, data, propulsion and cooling fluids. It results in one piece which is not supposed to be taken apart. 
Russian segment's modules are able to dock themselves, without human intervention using Proton rockets. Connections are made for power, data, propulsion and fluids and gases. Russian modular space station allows to be reconfigured according to needs. 

Note EVA: EVA is any activity by human being outside the spacecraft. The term spacewalk is also used, and it applies for spacecraft in Earth orbit, such as ISS, but it can be also used for lunar surface missions, where the term moonwalks was used. 
ISS: Left: May 2010, from Atlantis STS-132. Right: Station configuration by June 2017
Tiangong (2011-now) was the first Chinese space laboratory. Tiangong 1 was launched in September 2011. First the unmanned mission Shenzhou 8 performed successful rendezvous and docking in November 2011. Later the manned Shenzhou 9 docked with the station in June 2012, later the manned Shenzhou 10 in 2013. Tiangong 2 is ongoing mission and was launched in September 2016. The planned Tiangong 3 was merged with the Tiangong-2. Tiangong 1 deorbited and reentered over the South Pacific Ocean on April 2, 2018. 


Situation by June 2018


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