International Space Station
 Obverse view in November 2021 | |
 International Space Station program emblem with flags of the original signatory states[1] | |
| Station statistics | |
|---|---|
| COSPAR ID | 1998-067A |
| SATCAT no. | 25544 |
| Call sign | Alpha, Station |
| Crew |
|
| Launch | 20 November 1998[b] |
| Launch pad | |
| Mass | 450,000 kg (990,000 lb)[4] |
| Length | 109 m (358 ft) (overall), 94 m (310 ft) (truss)[5] |
| Width | 73 m (239 ft) (solar array)[5] |
| Pressurised volume | 1,005.0 m3 (35,491 cu ft)[5] |
| Atmospheric pressure | 1 atm (101.3 kPa; 14.7 psi) 79% nitrogen, 21% oxygen |
| Perigee altitude | 413 km (256.6 mi) AMSL[6] |
| Apogee altitude | 422 km (262.2 mi) AMSL[6] |
| Orbital inclination | 51.64°[6] |
| Orbital speed | 7.67 km/s; 27,600 km/h; 17,100 mph[7] |
| Orbital period | 92.9 minutes[8] |
| Orbits per day | 15.5[6] |
| Orbit epoch | 16 August 16:19:30[9] |
| Days in orbit | 27 years, 8 months, 6 days as of 26 July 2026 |
| Days occupied | 25 years, 8 months, 24 days as of 26 July 2026 |
| No. of orbits | 157,366 as of 29 June 2026[update][9] |
| Orbital decay | 2 km/month (1.2 mi/month) |
| Statistics as of 22 December 2022 (unless noted otherwise) References:[5][6][10][11][12] | |
| Configuration | |
 | |
The International Space Station (ISS)[c] is a space station in low Earth orbit (LEO). It is the product of the International Space Station program and is operated by five partner space agencies: NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada).[13] It is the first space station built, maintained and crewed through international cooperation and the largest human spacecraft ever constructed.[14][15] It is an orbital research station, where scientific experiments in microgravity are conducted and the space environment is studied.[15] Since 2 November 2000, it has hosted the longest continuous presence of humans in space.[16] Alongside Tiangong, it is one of the only two currently operational space stations.[17]
The station orbits between 51.64° north and south, at about 400 kilometres (250 miles)[18] above Earth, below the Van Allen radiation belts and most space debris.[19] Its orbit takes it at 7.67 km/s (27,600 km/h; 17,200 mph) roughly every 93 minutes around Earth, 15.5 times a day.[20] Measuring 109 m (358 ft) (with solar arrays) by 73 m (239 ft),[21] it is as large as a full-sized football or soccer field,[22] and has a pressurised internal volume of 1,005 m3 (35,491 ft3), comparable to a Boeing 747 airliner.[21]
The station is a modular space station divided into two main sections: the Russian Orbital Segment (ROS), developed by Roscosmos, and the US Orbital Segment (USOS), built by NASA, ESA, JAXA, and CSA. The Integrated Truss Structure connects the station's vast system of solar panels and radiators to its 16 major pressurized modules. These modules support scientific research, crew habitation, storage, spacecraft control, and airlock operations. The ISS has eight docking and berthing ports for visiting spacecraft. In total, the station consists of 43 different modules and elements.[23] Crews visit via the Soyuz and Crew Dragon spacecraft, and previously the Space Shuttle.[d] Cargo supply craft include Progress, Cargo Dragon, Cygnus, Automated Transfer Vehicle, and HTV-X.
The ISS is the political product of the development of international cooperation in space throughout the space age. The station combines two previously planned crewed Earth-orbiting stations: the United States' Space Station Freedom and the Soviet Union's Mir-2. The first ISS module was launched in 1998, with major components delivered by Proton, Soyuz and Space Shuttle launch vehicles. Long-term occupancy began with the arrival of the Expedition 1 crew on 2 November 2000. Since then, the ISS has remained continuously inhabited for 25 years and 266 days, the longest continuous human presence in space. As of August 2025[update], 290 individuals from 26 countries had visited the station.[24]
Future plans for the ISS include the addition of at least one module, the Payload Power Thermal Module by Axiom Space, forming the commercial segment of the station. The station is expected to remain operational until the end of 2030, by which parts of it are to be used for Axiom Station and the Russian Orbital Service Station. After this the ISS is planned to be de-orbited using the US Deorbit Vehicle,[25] but critique of this plan and the proposal of parking the station at a more stable higher orbit has gathered congressional support as of 2026[update].
Conception
Early into the space age and ensuing space race the US and USSR began to find opportunities for potential collaborations in outer space. This culminated in the 1975 Apollo–Soyuz Test Project, the first docking of spacecraft from two different spacefaring nations. The ASTP was considered a success, and further joint missions were also contemplated.
One such concept was International Skylab, which proposed launching the backup Skylab B space station for a mission that would see multiple visits by both Apollo and Soyuz crew vehicles.[26] More ambitious was the Skylab-Salyut Space Laboratory, which proposed docking the Skylab B to a Soviet Salyut space station. Falling budgets and rising Cold War tensions in the late 1970s saw these concepts fall by the wayside, along with another plan to have the Space Shuttle dock with a Salyut space station.[27]
In the early 1980s, NASA planned to launch a modular space station called Freedom as a counterpart to the Salyut and Mir space stations. In 1984 the European Space Agency (ESA) was invited to participate in Space Station Freedom, and the ESA approved the Columbus laboratory by 1987.[28] The Japanese Experiment Module (JEM), or Kibō, was announced in 1985, as part of the Freedom space station in response to a NASA request in 1982.
In early 1985, science ministers from the ESA countries approved the Columbus program, the most ambitious effort in space undertaken by that organization at the time. The plan spearheaded by Germany and Italy included a module which would be attached to Freedom, and with the capability to evolve into a full-fledged European orbital outpost before the end of the century.[29]
Increasing costs threw these plans into doubt in the early 1990s. Congress was unwilling to provide enough money to build and operate Freedom, and demanded NASA increase international participation to defray the rising costs or they would cancel the entire project outright.[30]
Simultaneously, the USSR was conducting planning for the Mir-2 space station, and had begun constructing modules for the new station by the mid-1980s. However the collapse of the Soviet Union required these plans to be greatly downscaled, and soon Mir-2 was in danger of never being launched at all.[31] With both space station projects in jeopardy, American and Russian officials met and proposed they be combined.[32]
In September 1993, American Vice-President Al Gore and Russian Prime Minister Viktor Chernomyrdin announced plans for a new space station, which eventually became the International Space Station.[33] They also agreed, in preparation for this new project, that the United States would be involved in the Mir program, including American Shuttles docking, in the Shuttle–Mir program.[34]
Purpose
The ISS was originally intended to be a laboratory, observatory, and factory while providing transportation, maintenance, and a low Earth orbit staging base for possible future missions to the Moon, Mars, and asteroids. However, not all of the uses envisioned in the initial memorandum of understanding between NASA and Roscosmos have been realised.[35] In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic,[36] and educational purposes.[37]
Scientific research
The ISS provides a platform to conduct scientific research, with power, data, cooling, and crew available to support experiments. Small uncrewed spacecraft can also provide platforms for experiments, especially those involving zero gravity and exposure to space, but space stations offer a long-term environment where studies can be performed potentially for decades, with ready access by human researchers.[38][39]
The ISS simplifies individual experiments by allowing groups of experiments to share the same launches and crew time. Research is conducted in a wide variety of fields, including astrobiology, astronomy, physical sciences, materials science, space weather, meteorology, and human research including space medicine and the life sciences.[40][41][42][43] Scientists on Earth have timely access to the data and can suggest experimental modifications to the crew. If follow-on experiments are necessary, the routinely scheduled launches of resupply craft allows new hardware to be launched with relative ease.[39] Crews fly expeditions of several months' duration, providing approximately 160 man-hours per week of labour with a crew of six. However, a considerable amount of crew time is taken up by station maintenance.[44]
A notable ISS experiment is the Alpha Magnetic Spectrometer (AMS), which is intended to detect dark matter and answer other fundamental questions about the universe. According to NASA, the AMS is as important as the Hubble Space Telescope. It is docked on the station, and could not have been easily accommodated on a free flying satellite platform because of its power and bandwidth needs.[45][46] On 3 April 2013, scientists reported that hints of dark matter may have been detected by the AMS.[47][48][49][50][51][52] According to these scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays".[53]
The space environment is hostile to life. Unprotected presence in space results in exposure to intense radiation (consisting primarily of protons and other subatomic charged particles from the solar wind, in addition to cosmic rays), vacuum, extreme temperatures, and microgravity.[54] Some simple forms of life called extremophiles,[55] as well as small invertebrates called tardigrades,[56] can survive in this environment in an extremely dry state through desiccation.
Medical research improves knowledge about the effects of long-term space exposure on the human body, including muscle atrophy, bone loss, and fluid shift. This data will be used to determine whether long-lasting human spaceflight and space colonisation is feasible. In 2006, data on bone loss and muscular atrophy suggested that there would be a significant risk of fractures and movement problems if astronauts landed on a planet after a lengthy interplanetary cruise, such as the six-month interval required to travel to Mars.[57][58][needs update]
Medical studies are conducted aboard the ISS on behalf of the National Space Biomedical Research Institute (NSBRI). Prominent among these is the Advanced Diagnostic Ultrasound in Microgravity study in which astronauts perform ultrasound scans under the guidance of remote experts. The study considers the diagnosis and treatment of medical conditions in space. There is usually no physician on board the ISS and diagnosis of medical conditions is a challenge. It is anticipated that remotely guided ultrasound scans will have application on Earth in emergency and rural care situations where in-person access to a trained physician is difficult.[59][60][61]
In August 2020, scientists reported that bacteria from Earth, particularly Deinococcus radiodurans bacteria, which is highly resistant to environmental hazards, were found to survive for three years in outer space, based on studies conducted on the International Space Station. These findings supported the notion of panspermia, the hypothesis that life exists throughout the Universe, distributed in various ways, including space dust, meteoroids, asteroids, comets, planetoids or contaminated spacecraft.[62][63]
Remote sensing of the Earth, astronomy, and deep space research on the ISS have significantly increased during the 2010s after the completion of the US Orbital Segment in 2011. Throughout the more than 20 years of the ISS program, researchers aboard the ISS and on the ground have examined aerosols, ozone, lightning, and oxides in Earth's atmosphere, as well as the Sun, cosmic rays, cosmic dust, antimatter, and dark matter in the universe. Examples of Earth-viewing remote sensing experiments that have flown on the ISS are the Orbiting Carbon Observatory 3, ISS-RapidScat, ECOSTRESS, the Global Ecosystem Dynamics Investigation, and the Cloud Aerosol Transport System. ISS-based astronomy telescopes and experiments include SOLAR, the Neutron Star Interior Composition Explorer, the Calorimetric Electron Telescope, the Monitor of All-sky X-ray Image (MAXI), and the Alpha Magnetic Spectrometer.[40][64]
Microgravity environment
Researchers are investigating the effect of the station's near-weightless environment on the evolution, development, growth and internal processes of plants and animals. In response to some of the data, NASA wants to investigate microgravity's effects on the growth of three-dimensional, human-like tissues and the unusual protein crystals that can be formed in space.[40]
Investigating the physics of fluids in microgravity will provide better models of the behaviour of fluids. Because fluids can be almost completely combined in microgravity, physicists investigate fluids that do not mix well on Earth. Examining reactions that are slowed by low gravity and low temperatures will improve our understanding of superconductivity.[40]
The study of materials science is an important ISS research activity, with the objective of reaping economic benefits through the improvement of techniques used on Earth.[65] Other areas of interest include the effect of low gravity on combustion, through the study of the efficiency of burning and control of emissions and pollutants. These findings may improve knowledge about energy production and lead to economic and environmental benefits.[40]
Exploration
The ISS provides a location in the relative safety of low Earth orbit to test spacecraft systems that will be required for long-duration missions to the Moon and Mars. This provides experience in operations, maintenance, and repair and replacement activities on-orbit. This will help develop essential skills in operating spacecraft farther from Earth, reduce mission risks, and advance the capabilities of interplanetary spacecraft.[66] Referring to the MARS-500 experiment, a crew isolation experiment conducted on Earth, ESA states, "Whereas the ISS is essential for answering questions concerning the possible impact of weightlessness, radiation and other space-specific factors, aspects such as the effect of long-term isolation and confinement can be more appropriately addressed via ground-based simulations".[67] Sergey Krasnov, the head of human space flight programs for Russia's space agency, Roscosmos, in 2011 suggested a "shorter version" of MARS-500 may be carried out on the ISS.[68]
In 2009, noting the value of the partnership framework itself, Sergey Krasnov wrote, "When compared with partners acting separately, partners developing complementary abilities and resources could give us much more assurance of the success and safety of space exploration. The ISS is helping further advance near-Earth space exploration and realisation of prospective programs of research and exploration of the Solar system, including the Moon and Mars."[69] A crewed mission to Mars may be a multinational effort involving space agencies and countries outside the current ISS partnership. In 2010, ESA Director-General Jean-Jacques Dordain stated his agency was ready to propose to the other four partners that China, India, and South Korea be invited to join the ISS partnership.[70] NASA chief Charles Bolden stated in February 2011, "Any mission to Mars is likely to be a global effort."[71] Currently, US federal legislation prevents NASA co-operation with China on space projects without approval by the FBI and Congress.[72]
Education and cultural outreach
The ISS crew provides opportunities for students on Earth by running student-developed experiments, making educational demonstrations, allowing for student participation in classroom versions of ISS experiments, and directly engaging students using radio, and email.[73][74] ESA offers a wide range of free teaching materials that can be downloaded for use in classrooms.[75] In one lesson, students can navigate a 3D model of the interior and exterior of the ISS, and face spontaneous challenges to solve in real time.[76]
The Japanese Aerospace Exploration Agency (JAXA) aims to inspire children to "pursue craftsmanship" and to heighten their "awareness of the importance of life and their responsibilities in society".[77] Through a series of education guides, students develop a deeper understanding of the past and near-term future of crewed space flight, as well as that of Earth and life.[78][79] In the JAXA "Seeds in Space" experiments, the mutation effects of spaceflight on plant seeds aboard the ISS are explored by growing sunflower seeds that have flown on the ISS for about nine months. In the first phase of Kibō utilisation from 2008 to mid-2010, researchers from more than a dozen Japanese universities conducted experiments in diverse fields.[80]
Cultural activities are another major objective of the ISS program. Tetsuo Tanaka, the director of JAXA's Space Environment and Utilization Center, has said: "There is something about space that touches even people who are not interested in science."[81]
Amateur Radio on the ISS (ARISS) is a volunteer program that encourages students worldwide to pursue careers in science, technology, engineering, and mathematics, through amateur radio communications opportunities with the ISS crew. ARISS is an international working group, consisting of delegations from nine countries including several in Europe, as well as Japan, Russia, Canada, and the United States. In areas where radio equipment cannot be used, speakerphones connect students to ground stations which then connect the calls to the space station.[82] Other licensed operators are able to contact the station freely via various methods, including NFM , APRS and SSTV (Only during events, and downlink only)[83]
First Orbit is a 2011 feature-length documentary film about Vostok 1, the first crewed space flight around the Earth. By matching the orbit of the ISS to that of Vostok 1 as closely as possible, in terms of ground path and time of day, documentary filmmaker Christopher Riley and ESA astronaut Paolo Nespoli were able to film the view that Yuri Gagarin saw on his pioneering orbital space flight. This new footage was cut together with the original Vostok 1 mission audio recordings sourced from the Russian State Archive. Nespoli is credited as the director of photography for this documentary film, as he recorded the majority of the footage himself during Expedition 26/27.[84] The film was streamed in a global YouTube premiere in 2011 under a free licence through the website firstorbit.org.[85]
In May 2013, commander Chris Hadfield shot a music video of David Bowie's "Space Oddity" on board the station, which was released on YouTube.[86][87] It was the first music video filmed in space.[88]
In November 2017, while participating in Expedition 52/53 on the ISS, Paolo Nespoli made two recordings of his spoken voice (one in English and the other in his native Italian), for use on Wikipedia articles. These were the first content made in space specifically for Wikipedia.[89][90]
In November 2021, a virtual reality exhibit called The Infinite featuring life aboard the ISS was announced.[91]
International co-operation
Involving five space programs and fifteen countries,[92] the International Space Station is the most politically and legally complex space exploration program in history.[92] The 1998 Space Station Intergovernmental Agreement sets forth the primary framework for international cooperation among the parties. A series of subsequent agreements govern other aspects of the station, ranging from jurisdictional issues to a code of conduct among visiting astronauts.[93]
Brazil was also invited to participate in the program, the only developing country to receive such an invitation. Under the agreement framework, Brazil was to provide six pieces of hardware, and in exchange, would receive ISS utilization rights. However, Brazil was unable to deliver any of the elements due to a lack of funding and political priority within the country. Brazil officially dropped out of the ISS program in 2007.[94][95]
Following the 2022 Russian invasion of Ukraine, continued cooperation between Russia and other countries on the International Space Station has been put into question. Roscosmos Director General Dmitry Rogozin insinuated that Russian withdrawal could cause the International Space Station to de-orbit due to lack of reboost capabilities, writing in a series of tweets, "If you block cooperation with us, who will save the ISS from an unguided de-orbit to impact on the territory of the US or Europe? There's also the chance of impact of the 500-ton construction in India or China. Do you want to threaten them with such a prospect? The ISS doesn't fly over Russia, so all the risk is yours. Are you ready for it?"[96] (This latter claim is untrue: the ISS flies over all parts of the Earth between 51.6 degrees latitude north and south, approximately the latitude of Saratov.) Rogozin later tweeted that normal relations between ISS partners could only be restored once sanctions have been lifted, and indicated that Roscosmos would submit proposals to the Russian government on ending cooperation.[97] NASA stated that, if necessary, US corporation Northrop Grumman has offered a reboost capability that would keep the ISS in orbit.[98]
On 26 July 2022, Yury Borisov, Rogozin's successor as head of Roscosmos, submitted to Russian President Vladimir Putin plans for withdrawal from the program after 2024.[99] However, Robyn Gatens, the NASA official in charge of the space station, responded that NASA had not received any formal notices from Roscosmos concerning withdrawal plans.[100]
Participating countries
Construction
Manufacturing
The International Space Station is a product of global collaboration, with its components manufactured across the world.
The modules of the Russian Orbital Segment, including Zarya and Zvezda, were produced at the Khrunichev State Research and Production Space Center in Moscow. Zvezda was initially manufactured in 1985 as a component for the Mir-2 space station, which was never launched.[101][102]
Much of the US Orbital Segment, including the Destiny and Unity modules, the Integrated Truss Structure, and solar arrays, were built at NASA's Marshall Space Flight Center in Huntsville, Alabama and Michoud Assembly Facility in New Orleans.[101] These components underwent final assembly and processing for launch at the Operations and Checkout Building and the Space Station Processing Facility (SSPF) at the Kennedy Space Center in Florida.[103]
The US Orbital Segment also hosts the Columbus module contributed by the European Space Agency and built in Germany, the Kibō module contributed by Japan and built at the Tsukuba Space Center and the Institute of Space and Astronautical Science, along with the Canadarm2 and Dextre, a joint Canadian-U.S. endeavor. All of these components were shipped to the SSPF for launch processing.[101][104]
Assembly
The assembly of the International Space Station, a major endeavour in space architecture, began in November 1998.[10]
Modules in the Russian segment launched and docked autonomously, with the exception of Rassvet. Other modules and components were delivered by the Space Shuttle, which then had to be installed by astronauts either remotely using robotic arms or during spacewalks, more formally known as extra-vehicular activities (EVAs). By 5 June 2011 astronauts had made over 159 EVAs to add components to the station, totaling more than 1,000 hours in space.[105][106]
The beginning of the core of the ISS's tenure in orbit was the launch of the Russian-built Zarya module atop a Proton rocket on 20 November 1998. Zarya provided propulsion, attitude control, communications, and electrical power. Two weeks later on 4 December 1998, the American-made Unity was ferried aboard Space Shuttle Endeavour on STS-88 and joined with Zarya. Unity provided the connection between the Russian and US segments of the station and would provide ports to connect future modules and visiting spacecraft.
While the connection of two modules built on different continents by nations that were once bitter rivals was a significant milestone, these two initial modules lacked life-support systems and the ISS remained unmanned for the next two years. At the time, the Russian station Mir was still inhabited.
The turning point arrived in July 2000 with the launch of the Zvezda module. Equipped with living quarters and life-support systems, Zvezda enabled continuous human presence aboard the station. The first crew, Expedition 1, arrived that November aboard Soyuz TM-31.[107][108]
The ISS grew steadily over the following years, with modules delivered by both Russian rockets and the Space Shuttle.
Expedition 1 arrived midway between the Space Shuttle flights of missions STS-92 and STS-97. These two flights each added segments of the station's Integrated Truss Structure, which provided the station with Ku band communications, additional attitude control needed for the additional mass of the USOS, and additional solar arrays.[109] Over the next two years, the station continued to expand. A Soyuz-U rocket delivered the Pirs docking compartment. The Space Shuttles Discovery, Atlantis, and Endeavour delivered the American Destiny laboratory and Quest airlock, in addition to the station's main robot arm, the Canadarm2, and several more segments of the Integrated Truss Structure.
Tragedy struck in 2003 with the loss of the Space Shuttle Columbia, which grounded the rest of the Shuttle fleet, halting construction of the ISS.
Assembly resumed in 2006 with the arrival of STS-115 with Atlantis, which delivered the station's second set of solar arrays. Several more truss segments and a third set of arrays were delivered on STS-116, STS-117, and STS-118. As a result of the major expansion of the station's power-generating capabilities, more modules could be accommodated, and the US Harmony module and Columbus European laboratory were added. These were soon followed by the first two components of the Japanese Kibō laboratory. In March 2009, STS-119 completed the Integrated Truss Structure with the installation of the fourth and final set of solar arrays. The final section of Kibō was delivered in July 2009 on STS-127, followed by the Russian Poisk module. The US Tranquility module was delivered in February 2010 during STS-130, alongside the Cupola, followed by the penultimate Russian module, Rassvet, in May 2010. Rassvet was delivered by Space Shuttle Atlantis on STS-132 in exchange for the Russian Proton delivery of the US-funded Zarya module in 1998.[110] The last pressurised module of the USOS, Leonardo, was brought to the station in February 2011 on the final flight of Discovery, STS-133.[111]
Russia's new primary research module Nauka docked in July 2021,[112] along with the European Robotic Arm which can relocate itself to different parts of the Russian modules of the station.[113] Russia's latest addition, the Prichal module, docked in November 2021.[114]
As of June 2025, nasa.gov states that there are 43 different modules and elements installed on the ISS.[115]
Structure
The ISS functions as a modular space station, enabling the addition or removal of modules from its structure for increased adaptability.
Blueprint of the ISS (as of 2018)
Rendering of the ISS (as of 2023)
Below is a diagram of major station components. The Unity node joins directly to the Destiny laboratory; for clarity, they are shown apart. Similar cases are also seen in other parts of the structure.
Key to box background colors:
- Pressurised component, accessible by the crew without using spacesuits
- Docking/berthing port, pressurized when a visiting spacecraft is present
- Airlock, to move people or material between pressurized and unpressurized environment
- Unpressurised station superstructure
- Unpressurised component
- Temporarily defunct or non-commissioned component
- Former, no longer installed component
- Future, not yet installed component
Pressurised modules
Zarya
Zarya (Russian: Заря, lit. 'Sunrise'[h]), also known as the Functional Cargo Block (Russian: Функционально-грузовой блок), was the inaugural component of the ISS. Launched in 1998, it initially served as the ISS's power source, storage, propulsion, and guidance system. As the station has grown, Zarya's role has transitioned primarily to storage, both internally and in its external fuel tanks.[117]
A descendant of the TKS spacecraft used in the Salyut program, Zarya was built in Russia but is owned by the United States. Its name symbolizes the beginning of a new era of international space cooperation.[118]
Unity
Unity, also known as Node 1, is the inaugural U.S.-built component of the ISS.[119][120] Serving as the connection between the Russian and U.S. segments, this cylindrical module features six Common Berthing Mechanism locations (forward, aft, port, starboard, zenith, and nadir) for attaching additional modules. Measuring 4.57 metres (15.0 ft) in diameter and 5.47 metres (17.9 ft) in length, Unity was constructed of steel by Boeing for NASA at the Marshall Space Flight Center in Huntsville, Alabama. It was the first of three connecting nodes – Unity, Harmony, and Tranquility – that forms the structural backbone of the U.S. segment of the ISS.[121]
Zvezda
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Zvezda (Russian: Звезда, lit. 'star') launched in July 2000, is the core of the Russian Orbital Segment of the ISS. Initially providing essential living quarters and life-support systems, it enabled the first continuous human presence aboard the station. While additional modules have expanded the ISS's capabilities, Zvezda remains the command and control center for the Russian segment and it is where crews gather during emergencies.[122][123][124]
A descendant of the Salyut program's DOS spacecraft, Zvezda was built by RKK Energia and launched atop a Proton rocket.[125]
Destiny
The Destiny laboratory is the primary research facility for U.S. experiments on the ISS. NASA's first permanent orbital research station since Skylab, the module was built by Boeing and launched aboard Space Shuttle Atlantis during STS-98. Attached to Unity over a period of five days in February 2001, Destiny has been a hub for scientific research ever since.[126][127][128]
Within Destiny, astronauts conduct experiments in fields such as medicine, engineering, biotechnology, physics, materials science, and Earth science. Researchers worldwide benefit from these studies. The module also houses life-support systems, including the Oxygen Generating System.[129]
Quest Joint Airlock
The Quest Joint Airlock enables extravehicular activities (EVAs) using either the U.S. Extravehicular Mobility Unit (EMU) or the Russian Orlan space suit.[130]
Before its installation, conducting EVAs from the ISS was challenging due to a variety of system and design differences. Only the Orlan suit could be used from the Transfer Chamber on the Zvezda module (which was not a purpose-built airlock) and the EMU could only be used from the airlock on a visiting Space Shuttle, which could not accommodate the Orlan.[131]
Launched aboard Space Shuttle Atlantis during STS-104 in July 2001 and attached to the Unity module, Quest is a 6.1-metre-long (20 ft), 4.0-metre-wide (13 ft) structure built by Boeing.[132] It houses the crew airlock for astronaut egress, an equipment airlock for suit storage, and has facilities to accommodate astronauts during their overnight pre-breathe procedures to prevent decompression sickness.[131]
The crew airlock, derived from the Space Shuttle, features essential equipment like lighting, handrails, and an Umbilical Interface Assembly (UIA) that provides life-support and communication systems for up to two spacesuits simultaneously. These can be either two EMUs, two Orlan suits, or one of each design.
Poisk
Poisk (Russian: По́иск, lit. 'Search'), also known as the Mini-Research Module 2 (Russian: Малый исследовательский модуль 2), serves as both a secondary airlock on the Russian segment of the ISS and supports docking for Soyuz and Progress spacecraft, facilitates propellant transfers from the latter.[133] Launched on 10 November 2009 attached to a modified Progress spacecraft, called Progress M-MIM2.[134][135]
Poisk provides facilities to maintain Orlan spacesuits and is equipped with two inward-opening hatches, a design change from Mir, which encountered a dangerous situation caused by an outward-opening hatch that opened too quickly because of a small amount of air pressure remaining in the airlock.[136] Since the departure of Pirs in 2021, it's become the sole airlock on the Russian segment.
Harmony
Harmony, or Node 2, is the central connecting hub of the US segment of the ISS, linking the U.S., European, and Japanese laboratory modules. It's also been called the "utility hub" of the ISS as it provides essential power, data, and life-support systems. The module also houses sleeping quarters for four crew members.[137]
Launched on 23 October 2007 aboard Space Shuttle Discovery on STS-120,[138][139] Harmony was initially attached to the Unity[140][141] before being relocated to its permanent position at the front of the Destiny laboratory on 14 November 2007.[142] This expansion added significant living space to the ISS, marking a key milestone in the construction of the U.S. segment.
Tranquility
Tranquility, also known as Node 3, is a module of the ISS. It contains environmental control systems, life-support systems, a toilet, exercise equipment, and an observation cupola.
The European Space Agency and the Italian Space Agency had Tranquility manufactured by Thales Alenia Space. A ceremony on 20 November 2009 transferred ownership of the module to NASA.[143] On 8 February 2010, NASA launched the module on the Space Shuttle's STS-130 mission.
Columbus
Columbus is a science laboratory that is part of the ISS and is the largest single contribution to the station made by the European Space Agency.
Like the Harmony and Tranquility modules, the Columbus laboratory was constructed in Turin, Italy by Thales Alenia Space. The functional equipment and software of the lab was designed by EADS in Bremen, Germany. It was also integrated in Bremen before being flown to the Kennedy Space Center in Florida in an Airbus Beluga jet. It was launched aboard Space Shuttle Atlantis on 7 February 2008, on flight STS-122. It is designed for ten years of operation. The module is control