Space station

• 1. Introduction

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  Space stations exist to keep human beings alive in orbit for weeks, months, or longer - a feat that requires solving problems no terrestrial architect has ever faced. On the 30th of May 2023, seventeen people were living in space at the same time: eleven aboard the International Space Station and six aboard China's Tiangong. That number had never been reached before. It is the latest peak in a story that stretches back to a science fiction story published in 1868 and runs through Cold War military secrets, a catastrophic early mission that killed its entire crew, and a gradual shift from single-piece stations to the vast modular structures that circle the planet today. What does it actually take to keep a human being alive in orbit? How did the idea of a space station travel from a magazine story to a functioning outpost? And what happens when two rival superpowers, each building their own station, both decide that modular design is the future?

• 2. From Fiction to Blueprint

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  Edward Everett Hale wrote the first description of anything resembling a space station in 1868, in a story called "The Brick Moon." Decades passed before anyone tried to put scientific rigor behind the idea. Konstantin Tsiolkovsky and Hermann Oberth each took that step in the early twentieth century, roughly two decades apart.

  The next landmark came in 1929, when Herman Potocnik published The Problem of Space Travel - the first work to propose a rotating wheel station that would use its own spin to generate artificial gravity. That same wheel concept resurfaced in 1951 when Wernher von Braun sketched a version of it in Collier's Weekly, crediting Potocnik by name. Despite the attention, no rotating station was ever built in the twentieth century.

  During the Second World War, German planners briefly imagined an orbital weapon called the "sun gun," positioned 8,200 kilometres above the Earth. No further research followed. The concept illustrated how thoroughly military thinking had begun to attach itself to the idea of orbital platforms, a thread that would run through the first actual stations built decades later.

• 3. Learning to Dock

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  Before any station could be inhabited, spacecraft had to learn to find each other in orbit. The first step was rendezvous: Gemini 6 and Gemini 7 pulled alongside each other in 1965 without physically connecting. A year later, in 1966, Neil Armstrong flew Gemini 8 and completed the first actual space docking in history.

  Automation arrived in 1967 when Kosmos 186 and Kosmos 188 became the first spacecraft to dock with no human hand on the controls. Then in January 1969, Soyuz 4 and Soyuz 5 carried out the first docked crew transfer - though the cosmonauts moved between vehicles by spacewalking outside, not by walking through an internal passage. That internal transfer, where astronauts moved directly through a connecting tunnel, waited until March 1969 when Apollo 9 demonstrated it for the first time.

  Earlier, the Apollo program had considered an entirely different goal. Its early planning included a crewed lunar orbital flight and a separate orbital laboratory called Project Olympus as possible alternatives to the lunar landing. When the Kennedy administration committed to landing on the Moon, both alternatives were set aside. The Apollo command and service module eventually performed docking maneuvers in the lunar environment that served station-like purposes, even though Project Olympus itself was never built.

• 4. The First Stations

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  Salyut 1 lifted off on the 19th of April 1971, making the Soviet Union the first nation to place a space station in orbit. Its first crew flew aboard Soyuz 11 and the mission ended in tragedy: the entire crew died. The station itself lasted only as long as its original supplies, a limitation built into the earliest designs.

  Those early stations were monolithic: a single structure launched in one piece, carrying all its equipment and consumables. Once the supplies ran out, the crew left and the station was abandoned. The military stations among the Soviet fleet - Salyut 2, Salyut 3, and Salyut 5 - operated under the Almaz program, a name that was not publicly associated with them at the time. The last of these, Salyut 5, orbited between 1976 and 1977.

  The civilian stations Salyut 6 and Salyut 7 introduced a second docking port, which changed everything. A Soyuz ferry could remain docked for up to 90 days before it needed to be replaced by a fresh vehicle. The second port also allowed Progress cargo ships to bring fresh supplies, making longer missions possible. Salyut 7 pushed the concept further still when it hard-docked with a TKS tug shortly before the station was abandoned, testing the idea that separate modules could be permanently joined in orbit. The American Skylab, which operated from 1973 to 1979, also had two docking ports but the second was never used.

• 5. Mir and the Modular Turn

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  Mir broke from every previous station design by launching a core unit first and adding modules later, each module built for a specific purpose. That approach removed the need for a single enormously powerful rocket to lift everything at once, and it allowed the station's role to evolve over time.

  Valeri Polyakov lived aboard Mir from 1994 to 1995, setting a duration record for a single spaceflight of 437.75 days that still stands. Four cosmonauts in total completed single missions of over a year, all of them on Mir. The station also hosted the first long-term ESA research project to be conducted from space: EUROMIR 95, which ran for 179 days and included 35 scientific experiments.

  Mir was supported at different points by multiple spacecraft: Soyuz and Progress vehicles from Roscosmos served throughout its operational life, and the Space Shuttle docked with it between 1995 and 1998. The station remained in orbit from 1986 until 2001, the year a final Progress vehicle was used specifically to guide it out of orbit. Soyuz flight T-15, which flew from March to July 1986, achieved something that has happened only once: it visited two different space stations in a single mission, stopping at both Mir and Salyut 7.

• 6. The ISS and Tiangong

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  Zarya, the first module of the International Space Station, launched in 1998. Expedition 1 arrived in October 2000 and humans have been aboard continuously ever since. During the station's first twenty years of operation, roughly 3,000 scientific experiments were conducted across biology and biotechnology, technology development, educational activities, human research, physical science, and Earth and space science.

  The station's Russian and American sections were built using fundamentally different philosophies. Russian modules launched on Proton rockets, flew to orbit independently, and docked themselves without human assistance; electrical, data, gas, and propellant connections were all made automatically. The US modules arrived on the Space Shuttle and were attached by crew members working in spacesuits during EVAs. Those US modules are integrated into a single structural block that cannot be disassembled and would need to be deorbited as one mass. In 2009, RKK Energia was exploring whether some Russian modules might eventually be removed and reused on a future station called OPSEK; by September 2017, the head of Roscosmos confirmed those plans had been dropped.

  China's Tiangong Space Station completed its core module on the 29th of April 2021 and added two laboratory modules in 2022, raising its crew capacity to six. The station orbits at 340 to 450 kilometres above Earth at an inclination of 42 to 43 degrees. It was declared complete on the 5th of November 2022 and has been occupied since the Shenzhou 14 mission in June of that year. On ISS, space tourism has become a small revenue stream; guests have paid around $50 million to spend a week living as an astronaut aboard the station.

• 7. Living in Orbit

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  The materials a space station is built from must endure radiation, micrometeoroid impacts, extreme temperature swings, and sustained internal pressure for years at a time. Stainless steel, titanium, and high-quality aluminum alloys form the primary structure, with layers of insulation and Kevlar added as ballistic shielding.

  Inside, the health challenges facing long-term residents include muscle atrophy, bone deterioration, balance disorders, eyesight disorders, and an elevated cancer risk from ionizing radiation. Air and water are brought up from Earth and then recycled aboard the station; supplemental oxygen can also be generated using solid fuel oxygen generators. Molds that grow inside stations can produce acids capable of corroding metal, glass, and rubber - a biological threat that is difficult to monitor because rapid methods for assessing which microbial cells are actually alive, sorted by species, remain elusive.

  One novel structural approach arrived on the ISS in April 2016: the Bigelow Expandable Activity Module, delivered by the SpaceX CRS-8 resupply mission. The module weighs 1,400 kilograms, was compressed for transport, and once inflated provided 16 cubic metres of volume. It was built on NASA research from the 1990s and was originally designed to last two years; as of August 2022 it was still attached and serving as storage. The next planned addition to the ISS is the commercial Axiom Station, which received NASA approval in January 2020 and is expected to begin with a module no earlier than 2027.