The International Space Station (ISS) is the largest structure ever assembled in space, orbiting Earth at an altitude of approximately 420 kilometers. Since November 2, 2000, when Expedition 1 crew members Bill Shepherd, Yuri Gidzenko, and Sergei Krikalev arrived aboard a Soyuz spacecraft, the station has been continuously inhabited.
Construction and Design
Assembly of the ISS began on November 20, 1998, with the launch of the Russian Zarya module. The U.S. Unity node followed in December 1998. Over the next thirteen years, more than 40 assembly flights delivered pressurized modules, solar arrays, and structural trusses. The station’s pressurized volume is approximately 916 cubic meters, with a mass of roughly 420,000 kilograms.
The ISS is a joint project of five space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada). Fifteen nations contribute to station operations.
Scientific Operations
The ISS has hosted thousands of scientific experiments across disciplines including biology, materials science, fluid physics, Earth observation, and human physiology. Research conducted aboard the station has produced findings published in peer-reviewed journals covering topics from protein crystal growth to the effects of microgravity on bone density and muscle atrophy.
Key laboratory modules include the U.S. Destiny Laboratory, the European Columbus module, the Japanese Kibo complex, and multiple Russian research segments.
Crew and Logistics
As of early 2026, the ISS has been visited by more than 270 individuals from 21 countries across approximately 70 expedition crews. Crew rotation is conducted via Russian Soyuz and SpaceX Crew Dragon spacecraft. Cargo resupply is provided by SpaceX Dragon, Northrop Grumman Cygnus, and Russian Progress vehicles.
Standard crew complement is six to seven astronauts and cosmonauts, though the station has accommodated up to thirteen during crew handover periods.
Future and Transition
NASA has announced plans to operate the ISS through 2030, with a controlled deorbit planned thereafter. The agency is supporting development of commercial successors through the Commercial Low Earth Orbit Destinations program, with contracts awarded to Axiom Space, Blue Origin, Nanoracks/Voyager Space, and Northrop Grumman for private station development.