Space station

The International Space Station was assembled in geocentric orbit, and is the largest artificial object in space

Part of a series on
Spaceflight
History
Space Race Timeline of spaceflight Space probes Lunar missions
Applications
Earth observation satellites Spy satellites Communications satellites Military satellite Satellite navigation Space telescopes Space exploration Space tourism Space colonization
Spacecraft
Robotic spacecraft Satellite Space probe Cargo spacecraft Human spaceflight Space capsule Space station Spaceplane
Space launch
Spaceport Launch pad Expendable and reusable launch vehicles Escape velocity Non-rocket spacelaunch
Spaceflight types
Sub-orbital Orbital Interplanetary Interstellar Intergalactic
Space agencies
Further information: List of government space agencies
Space forces
PLASSF AAE IRGCASF VKS USSF
Space commands
COMAE NORAD CDE DSA COS SOS NATO SC CONIDA KV ADD UKSC USSPACECOM
Private spaceflight
Axiom Space ARCAspace Astra Bigelow Aerospace Blue Origin Copenhagen Suborbitals Northrop Grumman Perigee Aerospace Rocket Lab Sierra Nevada Corporation SpaceX Virgin Galactic XCOR Aerospace
Spaceflight portal
v t

A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. Stations must have docking ports to allow other spacecraft to dock to transfer crew and supplies.

The purpose of maintaining an orbital outpost varies depending on the program. Space stations have most often been launched for scientific purposes, but military launches have also occurred. As of 2021, there is one fully operational and permanently inhabited space station in low Earth orbit: the International Space Station (ISS), which is used to study the effects of spaceflight on the human body as well as to provide a location to conduct a greater number and longer length of scientific studies than is possible on other space vehicles. China's Tiangong Space Station is under construction. Both India and Russia have proposed to build stations for the coming decades.

History[]

Rotating wheel space station. Wernher von Braun 1952 concept

The first mention of anything resembling a space station occurred in Edward Everett Hale's 1869 "The Brick Moon".^[1] The first to give serious, scientifically grounded consideration to space stations were Konstantin Tsiolkovsky and Hermann Oberth about two decades apart in the early 20th century.^[2] In 1929 Herman Potočnik's The Problem of Space Travel was published, the first to envision a "rotating wheel" space station to create artificial gravity.^[1] Conceptualized during the Second World War, the "sun gun" was a theoretical orbital weapon orbiting Earth at a height of 8,200 kilometres (5,100 mi). No further research was ever conducted.^[3] In 1951, Wernher von Braun published a concept for a rotating wheel space station in Collier's Weekly, referencing Potočnik's idea. However, development of a rotating station was never begun in the 20th century.^[2]

The first space station, Salyut-1. As seen from departing Soyuz 11

In 1971, the Soviet Union developed and launched the world's first space station, Salyut 1.^[4] The Almaz and Salyut series were eventually joined by Skylab, Mir, and Tiangong-1 and Tiangong-2. The hardware developed during the initial Soviet efforts remains in use, with evolved variants comprising a considerable part of the ISS, orbiting today. Each crew member stays aboard the station for weeks or months, but rarely more than a year. Starting with the ill-fated flight of the Soyuz 11 crew to Salyut 1, all recent human spaceflight duration records have been set aboard space stations. The duration record for a single spaceflight is 437.75 days, set by Valeri Polyakov aboard Mir from 1994 to 1995. As of 2016, four cosmonauts have completed single missions of over a year, all aboard Mir. The last military-use space station was the Soviet Salyut 5, which was launched under the Almaz program and orbited between 1976 and 1977.^[5]

Early monolithic stations (1971–1986)[]

The U.S. Skylab station of the 1970s

Early stations were monolithic designs that were constructed and launched in one piece, generally containing all their supplies and experimental equipment. A crew would then be launched to join the station and perform research. After the supplies had been used up, the station was abandoned.^[4]

The first space station was Salyut 1, which was launched by the Soviet Union on April 19, 1971. The earlier Soviet stations were all designated "Salyut", but among these there were two distinct types: civilian and military. The military stations, Salyut 2, Salyut 3, and Salyut 5, were also known as Almaz stations.^[6]

The civilian stations Salyut 6 and Salyut 7 were built with two docking ports, which allowed a second crew to visit, bringing a new spacecraft with them; the Soyuz ferry could spend 90 days in space, at which point it needed to be replaced by a fresh Soyuz spacecraft.^[7] This allowed for a crew to man the station continually. The American Skylab (1973–1979) was also equipped with two docking ports, like second-generation stations, but the extra port was never utilized. The presence of a second port on the new stations allowed Progress supply vehicles to be docked to the station, meaning that fresh supplies could be brought to aid long-duration missions. This concept was expanded on Salyut 7, which "hard docked" with a TKS tug shortly before it was abandoned; this served as a proof-of-concept for the use of modular space stations. The later Salyuts may reasonably be seen as a transition between the two groups.^[6]

Mir (1986–2001)[]

Earth and the Mir station

Unlike previous stations, the Soviet space station Mir had a modular design; a core unit was launched, and additional modules, generally with a specific role, were later added to that. This method allows for greater flexibility in operation, as well as removing the need for a single immensely powerful launch vehicle. Modular stations are also designed from the outset to have their supplies provided by logistical support craft, which allows for a longer lifetime at the cost of requiring regular support launches.^[8]

Modules are still being developed based on the design and capabilities of Mir.

Tiangong 1 and Tiangong 2 (2011–2019)[]

China's first space laboratory, Tiangong-1 was launched in September 2011.^[9] The uncrewed Shenzhou 8 then successfully performed an automatic rendezvous and docking in November 2011. The crewed Shenzhou 9 then docked with Tiangong-1 in June 2012, followed by the crewed Shenzhou 10 in 2013. A second space laboratory Tiangong-2 was launched in September 2016, while a plan for Tiangong-3 was merged with Tiangong-2.^[10]

In May 2017, China informed the United Nations Office for Outer Space Affairs that Tiangong-1's altitude was decaying and that it would soon reenter the atmosphere and break up.^[10] The reentry was projected to occur in late March or early April 2018.^[11] According to the China Manned Space Engineering Office, Tiangong-1 reentered over the South Pacific Ocean, northwest of Tahiti, on 2 April 2018 at 00:15 UTC.^{[12][13][14][15][16]}

In July 2019 the China Manned Space Engineering Office announced that it was planning to deorbit Tiangong-2 in the near future, but no specific date was given.^[17] The station subsequently made a controlled reentry on 19 July and burned up over the South Pacific Ocean.^[18]

Current[]

ISS (1998–present)[]

International Space Station under construction

Size comparisons between current and past space stations as they appeared most recently. Solar panels in blue, heat radiators in red. Note that stations have different depths not shown by silhouettes.

The ISS is divided into two main sections, the Russian Orbital Segment (ROS) and the US Orbital Segment (USOS). The first module of the International Space Station, Zarya, was launched in 1998.^[19]

The Russian Orbital Segment's "second-generation" modules were able to launch on Proton, fly to the correct orbit, and dock themselves without human intervention.^[20] Connections are automatically made for power, data, gases, and propellants. The Russian autonomous approach allows the assembly of space stations prior to the launch of crew.

The Russian "second-generation" modules are able to be reconfigured to suit changing needs. As of 2009, RKK Energia was considering the removal and reuse of some modules of the ROS on the Orbital Piloted Assembly and Experiment Complex after the end of mission is reached for the ISS.^[21] However, in September 2017 the head of Roscosmos said that the technical feasibility of separating the station to form OPSEK had been studied, and there were now no plans to separate the Russian segment from the ISS.^[22]

In contrast, the main US modules launched on the Space Shuttle and were attached to the ISS by crews during EVAs. Connections for electrical power, data, propulsion, and cooling fluids are also made at this time, resulting in an integrated block of modules that is not designed for disassembly and must be deorbited as one mass.^[23]

The Axiom Orbital Segment is a planned commercial segment to be added to the ISS starting in the mid 2020s. Axiom Space gained NASA approval for the venture in January 2020. Up to three Axiom modules will attach to the International Space Station. The first module could be launched no later than 2024 and will be docked to the forward port of Harmony, requiring relocation of the PMA-2. Axiom Space plans to attach up to two additional modules to its first core module, and send private astronauts to inhabit the modules. The modules could one day detach into the Axiom Station in a manner similar to Russia's proposed OPSEK.^[24]

Tiangong Space Station (2021–present)[]

The Tiangong Space Station (Chinese: 天宫; pinyin: Tiāngōng; lit. 'Heavenly Palace'), the first module of which was launched on 29 April 2021,^[25] is in low Earth orbit, 340 to 450 kilometres above the Earth at an orbital inclination of 42° to 43°. Its planned construction via 11 total launches across 2021-22 is intended to extend the core module with two laboratory modules, capable of hosting up to six crew.^[26][27]

Planned projects[]

This section is an excerpt from List of space stations § Planned and proposed.[]

These space stations have been announced by their host entity and are currently in planning, development or production. The launch date listed here may change as more information becomes available.

Name	Entity	Program	Crew size	Launch date	Remarks
Lunar Gateway	NASA ESA CSA JAXA	Artemis	4	November 2024[28][29]	Intended to serve as a science platform and as a staging area for the lunar landings of NASA's Artemis program and follow-on human mission to Mars.
Russian Orbital Service Station (ROSS)	Roscosmos		TBD	2025[30]
TBD	ISRO	Indian Human Spaceflight Programme	3	~2030[31][32][33][34]	ISRO chairman K. Sivan announced in 2019 that India will not join the International Space Station and will instead build a 20 tonne space station on its own.[35] It is intended to be built in the next 5–7 years,[36]
Lunar Orbital Station[37] (LOS)	Roscosmos		TBD	after 2030[38]
(SLARI)	LAPAN		TBD	2030–2035[39]

Canceled projects[]

This section is an excerpt from List of space stations § Canceled projects.[]

The interior of Skylab , on display at the Smithsonian's National Air and Space Museum

Most of these stations were canceled due to financial difficulties. However, Mir-2 was merged to Freedom and formed the basis of the International Space Station.

Name	Entity	Crew size	Remarks
Manned Orbiting Laboratory 1–7	NASA	2[40]	Canceled due to excessive costs in 1969[41]
Skylab B	NASA	3[42]	Constructed, but launch canceled due to lack of funding.[43] Now a museum piece.
OPS-4	USSR		Constructed but never launched, due to cancellation of the Almaz program.
Freedom	NASA	14–16[44]	Merged to form the basis of the International Space Station
Mir-2	USSR Roscosmos	2[45]
Columbus MTFF	ESA	3 (visiting from Hermes)
Galaxy	Bigelow Aerospace	Robotic[46]	Canceled due to rising costs and ability to ground test key Galaxy subsystems[47]
Almaz commercial	Excalibur Almaz	4 or more	Lack of funds.
OPSEK	Roscosmos	More than 2	Canceled in 2017. OPSEK components will instead remain attached to the ISS.

Architecture[]

Astronauts peer out of Destiny Laboratory, 2001

Astronaut taking a hot bath in the crew quarters of the Orbital Workshop (OWS) of the Skylab space station cluster in Earth orbit. In deploying the shower facility the shower curtain is pulled up from the floor and attached to the ceiling. The water comes through a push-button shower head attached to a flexible hose. Water is drawn off by a vacuum system.

Two types of space stations have been flown: monolithic and modular. Monolithic stations consist of a single vehicle and are launched by one rocket. Modular stations consist of two or more separate vehicles that are launched independently and docked on orbit. Modular stations are currently preferred due to lower costs and greater flexibility. Both types can be refueled by cargo craft, such as Progress.^{[citation needed]}

A space station is a complex vehicle that must incorporate many interrelated subsystems, including structure, electrical power, thermal control, attitude determination and control, orbital navigation and propulsion, automation and robotics, computing and communications, environmental and life support, crew facilities, and crew and cargo transportation. Stations must serve a useful role, which drives the capabilities required.^{[citation needed]}

Materials[]

Space stations are often made from durable materials that have to weather space radiation, internal pressure, micrometeoroids, and thermal effects of the sun and cold temperatures for very long periods of time. They are typically made from stainless steel, titanium and high-quality aluminum alloys, with layers of insulation such as Kevlar as a ballistics shield protection.^[48]

Habitability[]

Play media

Video of activities on and around the International Space Station

The space station environment presents a variety of challenges to human habitability, including short-term problems such as the limited supplies of air, water and food and the need to manage waste heat, and long-term ones such as weightlessness and relatively high levels of ionizing radiation. These conditions can create long-term health problems for space-station inhabitants, including muscle atrophy, bone deterioration, balance disorders, eyesight disorders, and elevated risk of cancer.^[49]

Future space habitats may attempt to address these issues, and could be designed for occupation beyond the weeks or months that current missions typically last. Possible solutions include the creation of artificial gravity by a rotating structure, the inclusion of radiation shielding, and the development of on-site agricultural ecosystems. Some designs might even accommodate large numbers of people, becoming essentially "cities in space" where people would reside semi-permanently.^[50]

Environmental microbiology[]

Molds that develop aboard space stations can produce acids that degrade metal, glass and rubber. Despite an expanding array of molecular approaches for detecting microorganisms, rapid and robust means of assessing the differential viability of the microbial cells, as a function of phylogenetic lineage, remain elusive.^[51]

See also[]

• Human outpost
• Research station – Station that is built for the purpose of conducting scientific research
• Space observatory
• Artificial satellite
• List of films featuring space stations
• Lunar outpost
• Martian outpost
• Space stations and habitats in fiction
• Timeline of Solar System exploration
• Underwater habitat

References[]

Bibliography[]

External links[]

• Read Congressional Research Service (CRS) Reports regarding Space Stations
• ISS - on Russian News Agency TASS Official Infographic(in English)
• "Giant Doughnut Purposed as Space Station", Popular Science, October 1951, pp. 120–121; article on the subject of space exploration and a space station orbiting earth