The International Space Station (ISS) is a modular research laboratory in low Earth orbit and the largest structure humans have assembled in space. Five agencies operate it together: NASA, Russia's Roscosmos, the European Space Agency, Japan's JAXA, and the Canadian Space Agency, on behalf of 15 partner nations.[1]
Assembly began in 1998, and the station has been staffed without interruption since November 2, 2000, a streak that passed 25 years in November 2025. More than 280 people have visited, and its laboratories have hosted thousands of experiments in biology, physics, materials science, Earth observation, and human physiology.[1] The partners plan to retire the station around 2030, when a SpaceX vehicle derived from Dragon will steer it into the atmosphere over a remote stretch of ocean.[4][5]
Assembly and partnership
The first element, the Russian-built and US-funded Zarya module, launched on a Proton rocket on November 20, 1998; the shuttle Endeavour attached the American Unity node two weeks later. The Zvezda service module arrived in July 2000 and made the outpost habitable, and Expedition 1 (William Shepherd, Yuri Gidzenko, and Sergei Krikalev) docked on November 2, 2000.[1]
More than 40 assembly flights followed, most of them Space Shuttle missions carrying pieces that could fly no other way: the Destiny laboratory in 2001, the main truss and solar arrays through the 2000s, Europe's Columbus and Japan's Kibo laboratories in 2008. Russia added the Nauka science module as late as 2021.[1]
Structure and orbit
The completed station measures 109 meters across its main truss and has a mass of roughly 420 tonnes, with pressurized volume comparable to a large airliner cabin.[1] Eight solar array wings, augmented since 2021 by roll-out arrays laid over the aging originals, supply electrical power.[1]
The ISS circles Earth about every 90 minutes at roughly 28,000 kilometers per hour, completing 16 orbits a day at an average altitude near 400 kilometers. Its 51.6 degree inclination, chosen to match Russian launch sites, carries it over most of the world's population, and it is regularly visible to the naked eye at dawn and dusk.[1]
Research
The station's purpose is sustained research in microgravity. Long-running results include protein crystal growth for drug development, combustion and fluid physics that behave differently without buoyancy, and the Cold Atom Lab, which produces ultracold quantum gases in orbit.[1] NASA's Twins Study compared astronaut Scott Kelly, who spent 340 days aboard in 2015-2016, with his Earthbound identical twin Mark to measure spaceflight's effects on the human body. Life support has advanced alongside the science: the US water recovery system now recycles about 98 percent of the water crews use, a requirement for future deep space missions.[1] More than 270 spacewalks have supported assembly and maintenance.[1]
Crew and cargo transportation
Crews originally rotated on the Space Shuttle and Russia's Soyuz, which became the only lifeline after the shuttle retired in 2011. Under NASA's Commercial Crew Program, SpaceX's Dragon began operational rotations in 2020 and had flown twelve of them by February 2026. Boeing's Starliner has yet to enter service; after its 2024 crewed test flight returned without its crew because of thruster failures, NASA rescheduled the vehicle's next flight as an uncrewed cargo mission.[1]
Supplies arrive on SpaceX cargo Dragons, Northrop Grumman's Cygnus, Russia's Progress, and Japan's HTV-X, which made its first delivery in October 2025.[1]
Recent events
On January 15, 2026, the Crew-11 mission returned to Earth about six weeks early after a crew member developed a medical issue that could not be treated in orbit, the first medical-evacuation return in NASA's history. The station operated with a reduced three-person crew for a month afterward.[3] Staffing returned to normal when Crew-12 launched on a Falcon 9 on February 13, 2026 and docked the next day.[2][3]
As of July 2026 the station hosts the seven members of Expedition 74:[2]
| Crew member | Agency | Arrived aboard |
|---|---|---|
| Sergey Kud-Sverchkov (commander) | Roscosmos | Soyuz MS-28 |
| Sergei Mikaev | Roscosmos | Soyuz MS-28 |
| Christopher Williams | NASA | Soyuz MS-28 |
| Jessica Meir | NASA | SpaceX Crew-12 |
| Jack Hathaway | NASA | SpaceX Crew-12 |
| Sophie Adenot | ESA | SpaceX Crew-12 |
| Andrey Fedyaev | Roscosmos | SpaceX Crew-12 |
Retirement and deorbit plan
The Western partners have committed to operate the station through 2030, and Russia through at least 2028.[5] In June 2024 NASA awarded SpaceX a contract worth up to 843 million dollars to build the US Deorbit Vehicle (USDV), an enlarged Dragon derivative with 46 Draco thrusters.[4] Under the current plan the USDV launches around 2029, docks with the station, and after a period of natural orbital decay performs a final burn in late 2030 or early 2031 to bring the complex down over an unpopulated ocean area.[5]
The schedule is not settled politics. A draft measure attached to the NASA Authorization Act of 2026 in the US Senate would direct the agency to keep the station flying through 2032, two years longer than planned, reflecting concern that no replacement will be ready in time.[6]
Commercial successors
NASA's Commercial Low Earth Orbit Destinations program funds private stations intended to take over after the ISS, with a stated goal of keeping at least one destination operating before the ISS is deorbited; a second phase of funded agreements was planned for 2026.[7] Axiom Space intends to attach its first modules to the ISS and later detach them as a free-flying station, while Starlab (a Voyager Technologies and Airbus venture) and Blue Origin's Orbital Reef, developed with Sierra Space, remain in design and early production stages.[7]
The nearest-term entrant is outside the NASA program: Vast's privately funded Haven-1, a single-module station that began final integration in January 2026 and is slated to launch on a Falcon 9 in the first quarter of 2027. If it flies on schedule, it would become the first commercial space station.[8]
References
- International Space Station - Wikipedia.
- NASA's SpaceX Crew-12 Launches to International Space Station - NASA.
- SpaceX, NASA mission arrives at ISS, relieving bare-bones astronaut crew - CNN.
- NASA Selects International Space Station US Deorbit Vehicle - NASA.
- FAQs: The International Space Station Transition Plan - NASA.
- NASA must delay deorbiting the ISS, U.S. lawmakers say - Scientific American.
- Commercial Space Stations - NASA.
- Haven-1 - Wikipedia.
