Early concepts

The first mention of anything resembling a space station occurred in Edward Everett Hale's 1868 "The Brick Moon".^[7] 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.^[8] 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.^[7] 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.^[9] 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.^[8]

First advances and precursors

The first human flew to space and concluded the first orbit on April 12, 1961 with Vostok 1.

The Apollo program had in its early planning instead of a lunar landing a crewed lunar orbital flight and an orbital laboratory station in orbit of Earth, at times called Project Olympus, as two different possible program goals, until the Kennedy administration sped ahead and made the Apollo program focus on what was originally planned to come after it, the lunar landing. The Project Olympus space station, or orbiting laboratory of the Apollo program, was proposed as an in-space unfolded structure with the Apollo command and service module docking.^[10] While never realized, the Apollo command and service module would performe docking maneuvers and eventually become a lunar orbiting module which was used for station-like purposes.

But before that the Gemini program paved the way and achieved the first space rendezvous with Gemini 6 and Gemini 7 in 1965.

This section is an excerpt from Space rendezvous § First docking.[edit]

The first docking of two spacecraft was achieved on March 16, 1966 when Gemini 8, under the command of Neil Armstrong, rendezvoused and docked with an uncrewed Agena Target Vehicle. Gemini 6 was to have been the first docking mission, but had to be cancelled when that mission's Agena vehicle was destroyed during launch.^[11]

The Soviets carried out the first automated, uncrewed docking between Cosmos 186 and Cosmos 188 on October 30, 1967.^[12]

The first Soviet cosmonaut to attempt a manual docking was Georgy Beregovoy who unsuccessfully tried to dock his Soyuz 3 craft with the uncrewed Soyuz 2 in October 1968. Automated systems brought the craft to within 200 meters (660 ft), while Beregovoy brought this closer with manual control.^[13]

The first successful crewed docking^[14] occurred on January 16, 1969 when Soyuz 4 and Soyuz 5 docked, collecting the two crew members of Soyuz 5, which had to perform an extravehicular activity to reach Soyuz 4.^[15]

In March 1969 Apollo 9 achieved the first internal transfer of crew members between two docked spacecraft.

The first rendezvous of two spacecraft from different countries took place in 1975, when an Apollo spacecraft docked with a Soyuz spacecraft as part of the Apollo–Soyuz mission.^[16]

The first multiple space docking took place when both Soyuz 26 and Soyuz 27 were docked to the Salyut 6 space station during January 1978.^{[citation needed]}

Salyut, Almaz and Skylab

In 1971, the Soviet Union developed and launched the world's first space station, Salyut 1.^[17] 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.

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.^[17]

The first space station was Salyut 1, which was launched by the Soviet Union on April 19, 1971. The early 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.^[18]

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.^[19] 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 used. 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.^[18]

Mir

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.^[20]

International Space Station

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.^[21]

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.^[22] 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.^[23] 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.^[24]

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.^[25]

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, Hab One, is expected to be launched at the end of 2026^[26] 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 would later detach into the Axiom Station in a manner similar to Russia's proposed OPSEK.^[27]

Tiangong program

China's first space laboratory, Tiangong-1 was launched in September 2011.^[28] 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.^{[citation needed]}

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.^[29][30]

A second space laboratory Tiangong-2 was launched in September 2016, while a plan for Tiangong-3 was merged with Tiangong-2.^[31] The station made a controlled reentry on 19 July 2019 and burned up over the South Pacific Ocean.^[32]

The Tiangong Space Station (Chinese: 天宫; pinyin: Tiāngōng; lit. 'Heavenly Palace'), the first module of which was launched on 29 April 2021,^[33] 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.^[34][35]

Planned projects

More information Name, Entity ...

Name	Entity	Program	Crew size	Launch date	Remarks
Lunar Gateway	NASA ESA CSA JAXA	Artemis	4	2025[36]	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.
Axiom Station	Axiom Space	International Space Station programme	TBD	Late 2026[37]	Eventually will detach from the ISS in the early 2030s and form a private, free flying space station for commercial tourism and science activities.
Russian Orbital Service Station	Roscosmos	Russia's next generation space station.	TBD	2027[38]	With Russia leaving the ISS programme sometime after 2024, Roscosmos announced this new space station in April 2021 as the replacement for that program.
Starlab	NanoRacks Voyager Space Lockheed Martin Airbus	Private	4	2028[39]	"Commercial platform supporting a business designed to enable science, research, and manufacturing for customers around the world."
StarMax	Gravitics	Private	TBD	2026[40]	"The StarMax module provides up to 400 cubic meters of usable habitable volume - nearly half the volume of the International Space Station in one module."
Orbital Reef	Blue Origin Sierra Space	Private	10	second half 2020s[41]	"Commercial station in LEO for research, industrial, international, and commercial customers."
Bharatiya Antariksha Station[42]	ISRO	Indian Human Spaceflight Programme	3	~2035[43][44][45][46][47]	ISRO chairman K. Sivan announced in 2019 that India will not join the International Space Station, but will instead build a 20 ton space station of its own.[48] It is intended to be built 5–7 years after the conclusion of the Gaganyaan program.[49]
Lunar Orbital Station[50]	Roscosmos		TBD	after 2030[51]
Haven-1	Vast	Private	4	2025[52]	"Scheduled to be the world's first commercial space station, Haven-1 and subsequent human spaceflight missions will accelerate access to space exploration"[53]
LIFE Pathfinder	Sierra Space	Private	TBD	2026	"Before offering LIFE for Orbital Reef, though, the company is proposing to launch a standalone “pathfinder” version of LIFE as soon as the end of 2026".[54]

Close

Cancelled projects

More information Name, Entity ...

Name	Entity	Crew	Cancellation	Remarks
Manned Orbiting Laboratory 1–7	USAF	2[55]	1969	Boilerplate mission launched successfully, wider project cancelled due to excessive costs[56]
Skylab B	NASA	3[57]	1976	Constructed, but launch cancelled due to lack of funding.[58] Now a museum piece.
OPS-4	USSR	3[59]	1979	Constructed, but Almaz program cancelled in favour of uncrewed recon satellites.
Freedom	NASA	14–16[60]	1993	Merged to form the basis of the International Space Station.
Mir-2	USSR Roscosmos	2[61]
Columbus MTFF	ESA	3
Galaxy	Bigelow Aerospace	Robotic[62]	2007	Canceled due to rising costs and ability to ground test key Galaxy subsystems[63]
Sundancer		3	2011	Was under construction, but cancelled in favour of developing B330.
Almaz commercial	Excalibur Almaz	4+	2016	Soviet hardware was acquired, but never launched due to lack of funds.
Tiangong-3	CNSA	3	2017	The goals for Tiangong-2 and 3 were merged, and were completed by a single station rather than two separate stations.
OPSEK	Roscosmos	2+	2017	Some modules such as Nauka were launched and attached to the ISS- but proposals to split these off as a separate station were cancelled, and they instead remain part of the ISS.
B330	Bigelow Aerospace	3	2020	Test articles were constructed but not flight ready hardware; cancelled due to the COVID-19 pandemic.

Close

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

Most of these stations were canceled due to financial difficulties, or merged into other projects.

Orbit and purpose

Materials

Space stations are 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.^[66]

The International Space Station has a single inflatable module, the Bigelow Expandable Activity Module, which was installed in April 2016 after being delivered to the ISS on the SpaceX CRS-8 resupply mission.^[67][68] This module, based on NASA research in the 1990s, weighed 1,400 kilograms (3,100 lb) and was transported while compressed before being attached to the ISS by the space station arm and inflated to provide a 16 cubic metres (21 cu yd) volume. Whilst it was initially designed for a 2 year lifetime it was still attached and being used for storage in August 2022.^[69][70]

Construction

• Salyut 1 - first space station, launched in 1971
• Skylab - launched in a single launch in May 1973
• Mir - first modular space station assembled in orbit
• International Space Station - modular space station assembled in orbit
• Tiangong space station - Chinese space station

Habitability

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.^[71]

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.^[72]

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.^[73]

Power

Like uncrewed spacecraft close to the Sun, space stations in the inner Solar System generally rely on solar panels to obtain power.^[74]

Life support

Space station air and water is brought up in spacecraft from Earth before being recycled. Supplemental oxygen can be supplied by a solid fuel oxygen generator.^[75]

Communications

Resupply and crew vehicles

Many spacecraft are used to dock with the space stations. Soyuz flight T-15 in March to July 1986 was the first and as of 2016, only spacecraft to visit two different space stations, Mir and Salyut 7.^[77]

Docking and berthing

Maintenance

Research

Research conducted on the Mir included the first long term space based ESA research project EUROMIR 95 which lasted 179 days and included 35 scientific experiments.^[116]

During the first 20 years of operation of the International Space Station, there were around 3,000 scientific experiments in the areas of biology and biotech, technology development, educational activities, human research, physical science, and Earth and space science.^[117][118]

Space tourism

On the International Space Station, guests sometimes pay $50 million to spend the week living as an astronaut. Later, space tourism is slated to expand once launch costs are lowered sufficiently. By the end of the 2020s, space hotels may become relatively common.^{[citation needed]}

Technology spinoffs

International cooperation and economy

Cultural impact

Space settlement