Overview
The International Space Station is a modular structure assembled in orbit over more than a decade, from the launch of its first component in 1998 to the final major module arrival in 2021. Built by five space agencies — NASA, Roscosmos, ESA, JAXA and CSA — the ISS consists of 16 pressurised modules providing approximately 916 m³ of habitable volume, an integrated truss structure spanning 109 metres, and extensive external platforms for experiments and equipment.
US Orbital Segment (USOS)
The US Orbital Segment includes modules contributed by NASA, ESA, JAXA and CSA. These form the primary laboratory and habitation areas of the station.
| Module | Agency | Launch | Role |
|---|---|---|---|
| Unity (Node 1) | NASA | Dec 1998 | First US element; six-port connecting node linking the Russian and American segments |
| Destiny | NASA | Feb 2001 | Primary US research laboratory — microgravity science, life sciences and materials experiments |
| Quest | NASA | Jul 2001 | Joint airlock — enables EVAs (spacewalks) using both US EMU and Russian Orlan suits |
| Harmony (Node 2) | NASA / ESA-built | Oct 2007 | Utility hub connecting Columbus, Kibo and crew transfer vehicles; provides power and data |
| Columbus | ESA | Feb 2008 | European research laboratory — fluid physics, materials science, biology and external experiments via the EPF |
| Kibō (JEM) | JAXA | Mar–Jul 2008 | Japan's laboratory complex — the largest single ISS module, including pressurised lab, logistics module, exposed facility and robotic arm |
| Tranquility (Node 3) | NASA / ESA-built | Feb 2010 | Life support and crew exercise; hosts the Cupola and ARED exercise machine |
| Cupola | ESA | Feb 2010 | Seven-window observation dome — used for Earth observation, robotics operations and photography |
| Leonardo (PMM) | NASA / ASI | Feb 2011 | Permanent multi-purpose module — storage for supplies, equipment and experiments |
| Bigelow BEAM | NASA / Bigelow | Apr 2016 | Expandable technology demonstrator — inflatable habitat module, now used for storage |
| IDA-2 & IDA-3 | NASA | 2016 / 2019 | International Docking Adapters — NDS-standard ports for Crew Dragon and Starliner |
| NanoRacks Bishop | NanoRacks | Dec 2020 | Commercial airlock — deploys CubeSats and transfers experiments to/from the vacuum of space |
Russian Orbital Segment (ROS)
The Russian segment provides critical propulsion, life support and docking capabilities. It includes the station's oldest module and the most recently launched pressurised element.
| Module | Agency | Launch | Role |
|---|---|---|---|
| Zarya (FGB) | Roscosmos / NASA-funded | Nov 1998 | First ISS component launched — provided initial propulsion, power and attitude control; now primarily used for storage |
| Zvezda (SM) | Roscosmos | Jul 2000 | Service module — crew quarters, life support, propulsion and orbital reboost engines; the structural and functional centre of the Russian segment |
| Pirs (DC-1) | Roscosmos | Sep 2001 | Docking compartment and airlock for Russian EVAs and Soyuz/Progress vehicles (undocked and deorbited Jul 2021 to make room for Nauka) |
| Poisk (MRM-2) | Roscosmos | Nov 2009 | Mini research module — docking port for Soyuz/Progress and airlock for Russian EVAs |
| Rassvet (MRM-1) | Roscosmos | May 2010 | Docking and cargo storage module — attached to Zarya's nadir port |
| Nauka (MLM) | Roscosmos | Jul 2021 | Multipurpose laboratory module — the largest Russian ISS module, with European Robotic Arm (ERA), additional crew quarters, science facilities and an airlock |
| Prichal | Roscosmos | Nov 2021 | Node module — six-port docking hub attached to Nauka, expands docking capacity for visiting vehicles |
Integrated Truss Structure
The ISS truss is a 109-metre backbone of aluminium segments that supports the station's four pairs of solar arrays, thermal radiators, batteries and external experiment platforms. The truss was assembled across 11 Space Shuttle flights between 2000 and 2009. Each pair of solar arrays spans 73 metres and generates up to 120 kW of electrical power — making the ISS visible from Earth as a bright, slow-moving point of light.
Assembly Timeline
Construction of the ISS required more than 40 assembly flights — 37 Space Shuttle missions and numerous Russian Proton and Soyuz launches. The first element (Zarya) launched on 20 November 1998 aboard a Russian Proton-K rocket. The station was declared "assembly complete" in 2011, though new elements have continued to arrive, most recently Nauka (2021) and Prichal (2021). The station is expected to operate until at least 2030 before a controlled deorbit.
Current Configuration
As of 2026, the ISS has a total mass of approximately 420,000 kg, orbits at roughly 410 km altitude, and supports a permanent crew of 6–7 astronauts across NASA, Roscosmos, ESA, JAXA and CSA rotations. The station completes one orbit every ~92 minutes at a speed of 27,600 km/h. Visiting vehicles currently include SpaceX Crew Dragon, SpaceX Cargo Dragon, Northrop Grumman Cygnus, Roscosmos Progress and Soyuz. You can follow its position in real time on our live ISS tracker.