International Space Station – Wikipedia

Space station in low Earth orbit

ISS Agreements

ISS Logo

The International Space Station (ISS) is a modular space station (habitable artificial satellite) in low Earth orbit. The ISS programme is a multi-national collaborative project between five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada).[6][7] The ownership and use of the space station is established by intergovernmental treaties and agreements.[8]

The ISS serves as a microgravity and space environment research laboratory in which scientific experiments are conducted in astrobiology, astronomy, meteorology, physics, and other fields.[9][10][11] The station is suited for testing the spacecraft systems and equipment required for possible future long-duration missions to the Moon and Mars.[12] It is the largest artificial object in space and the largest satellite in low Earth orbit, regularly visible to the naked eye from Earth's surface.[13][14] It maintains an orbit with an average altitude of 400 kilometres (250mi) by means of reboost manoeuvres using the engines of the Zvezda Service Module or visiting spacecraft.[15] The ISS circles the Earth in roughly 92minutes, completing 15.5orbits per day.[16]

The station is divided into two sections: the Russian Orbital Segment (ROS), operated by Russia; and the United States Orbital Segment (USOS), which is shared by many nations. Roscosmos has endorsed the continued operation of ISS through 2024,[17] but had previously proposed using elements of the Russian segment to construct a new Russian space station called OPSEK.[18] As of December2018[update], the station is expected to operate until 2030.[19]

The first ISS component was launched in 1998, with the first long-term residents arriving on 2November 2000.[20] Since then, the station has been continuously occupied for 19years and 188days.[21] This is the longest continuous human presence in low Earth orbit, having surpassed the previous record of 9years and 357days held by the Mir space station. The latest major pressurised module was fitted in 2011, with an experimental inflatable space habitat added in 2016. Development and assembly of the station continues, with several major new Russian elements scheduled for launch starting in 2020. The ISS consists of pressurised habitation modules, structural trusses, photovoltaic solar arrays, radiators, docking ports, experiment bays and robotic arms. Major ISS modules have been launched by Russian Proton and Soyuz rockets and US Space Shuttles.[22]

The ISS is the ninth space station to be inhabited by crews, following the Soviet and later Russian Salyut, Almaz, and Mir stations as well as Skylab from the US. The station is serviced by a variety of visiting spacecraft: the Russian Soyuz and Progress, the US Dragon and Cygnus, the Japanese H-II Transfer Vehicle,[6] and formerly the European Automated Transfer Vehicle. The Dragon spacecraft allows the return of pressurised cargo to Earth (downmass), which is used for example to repatriate scientific experiments for further analysis. The Soyuz return capsule has minimal downmass capability next to the astronauts.

The ISS has been visited by astronauts, cosmonauts and space tourists from 19 different nations. As of September 2019[update], 239people from 19countries had visited the space station, many of them multiple times. The United States sent 151people, Russia sent 47, nine were Japanese, eight Canadian, five Italian, four French, three German, and one each from Belgium, Brazil, Denmark, Kazakhstan, Malaysia, the Netherlands, South Africa, South Korea, Spain, Sweden, the United Arab Emirates, and the United Kingdom.[23]

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 come to fruition.[24] In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic,[25] and educational purposes.[26]

Fisheye view of several labs

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, combined with ready access by human researchers.[27][28]

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.[9][10][11][29][30] 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.[28] Crews fly expeditions of several months' duration, providing approximately 160 person-hours per week of labour with a crew of six. However, a considerable amount of crew time is taken up by station maintenance.[9][31]

Perhaps the most notable ISS experiment is the Alpha Magnetic Spectrometer (AMS), which is intended to detect dark matter and answer other fundamental questions about our universe and is as important as the Hubble Space Telescope according to NASA. Currently docked on station, it could not have been easily accommodated on a free flying satellite platform because of its power and bandwidth needs.[32][33] On 3 April 2013, scientists reported that hints of dark matter may have been detected by the AMS.[34][35][36][37][38][39] According to the scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays".

The space environment is hostile to life. Unprotected presence in space is characterised by an intense radiation field (consisting primarily of protons and other subatomic charged particles from the solar wind, in addition to cosmic rays), high vacuum, extreme temperatures, and microgravity.[40] Some simple forms of life called extremophiles,[41] as well as small invertebrates called tardigrades[42] 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 high duration human spaceflight and space colonisation are feasible. As of 2006[update], data on bone loss and muscular atrophy suggest 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.[43][44]

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. Usually, there is 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 access to a trained physician is difficult.[45][46][47]

Gravity at the altitude of the ISS is approximately 90% as strong as at Earth's surface, but objects in orbit are in a continuous state of freefall, resulting in an apparent state of weightlessness.[48] This perceived weightlessness is disturbed by five separate effects:[49]

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 this 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.[10]

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. In addition, examining reactions that are slowed by low gravity and low temperatures will improve our understanding of superconductivity.[10]

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 the ground.[50] Other areas of interest include the effect of the low gravity environment on combustion, through the study of the efficiency of burning and control of emissions and pollutants. These findings may improve current knowledge about energy production, and lead to economic and environmental benefits. Future plans are for the researchers aboard the ISS to examine aerosols, ozone, water vapour, and oxides in Earth's atmosphere, as well as cosmic rays, cosmic dust, antimatter, and dark matter in the Universe.[10]

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 as well as repair and replacement activities on-orbit, which will be essential skills in operating spacecraft farther from Earth, mission risks can be reduced and the capabilities of interplanetary spacecraft advanced.[12] Referring to the MARS-500 experiment, ESA states that "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".[51] Sergey Krasnov, the head of human space flight programmes for Russia's space agency, Roscosmos, in 2011 suggested a "shorter version" of MARS-500 may be carried out on the ISS.[52]

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 programmes of research and exploration of the Solar system, including the Moon and Mars."[53] 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.[54] NASA chief Charlie Bolden stated in February 2011, "Any mission to Mars is likely to be a global effort".[55] Currently, US federal legislation prevents NASA co-operation with China on space projects.[56]

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, videolink and email.[6][57] ESA offers a wide range of free teaching materials that can be downloaded for use in classrooms.[58] In one lesson, students can navigate a 3-D model of the interior and exterior of the ISS, and face spontaneous challenges to solve in real time.[59]

JAXA aims to inspire children to "pursue craftsmanship" and to heighten their "awareness of the importance of life and their responsibilities in society".[60] Through a series of education guides, a deeper understanding of the past and near-term future of crewed space flight, as well as that of Earth and life, will be learned.[61][62] In the JAXA Seeds in Space experiments, the mutation effects of spaceflight on plant seeds aboard the ISS is explored. Students grow sunflower seeds which flew on the ISS for about nine months. In the first phase of Kib utilisation from 2008 to mid-2010, researchers from more than a dozen Japanese universities conducted experiments in diverse fields.[63]

Cultural activities are another major objective. Tetsuo Tanaka, director of JAXA's Space Environment and Utilization Center, says "There is something about space that touches even people who are not interested in science."[64]

Amateur Radio on the ISS (ARISS) is a volunteer programme which 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 countries 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 station.[65]

First Orbit is a feature-length documentary film about Vostok 1, the first crewed space flight around the Earth. By matching the orbit of the International Space Station 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, during Expedition 26/27, filmed the majority of the footage for this documentary film, and as a result is credited as its director of photography.[66] The film was streamed through the website firstorbit.org in a global YouTube premiere in 2011, under a free licence.[67]

In May 2013, commander Chris Hadfield shot a music video of David Bowie's "Space Oddity" on board the station; the film was released on YouTube.[68] It was the first music video ever to be filmed in space.[69]

In November 2017, while participating in Expedition 52/53 on the ISS, Paolo Nespoli made two recordings (one in English the other in his native Italian) of his spoken voice, for use on Wikipedia articles. These were the first content made specifically for Wikipedia, in space.[70][71]

Since the International Space Station is a multi-national collaborative project, the components for in-orbit assembly were manufactured in various countries around the world. Beginning in the mid 1990s, the U.S. components Destiny, Unity, the Integrated Truss Structure, and the solar arrays were fabricated at the Marshall Space Flight Center and the Michoud Assembly Facility. These modules were delivered to the Operations and Checkout Building and the Space Station Processing Facility for final assembly and processing for launch.[72]

The Russian modules, including Zarya and Zvezda, were manufactured at the Khrunichev State Research and Production Space Center in Moscow. Zvezda was initially manufactured in 1985 as a component for Mir-2, but was never launched and instead became the ISS Service Module.[73]

The European Space Agency Columbus module was manufactured at the EADS Astrium Space Transportation facilities in Bremen, Germany, along with many other contractors throughout Europe[74]. The other ESA-built modules - Harmony, Tranquility, the Leonardo MPLM, and the Cupola - were initially manufactured at the Thales Alenia Space factory located at the Cannes Mandelieu Space Center. The structural steel hulls of the modules were transported by aircraft to the Kennedy Space Center SSPF for launch processing.[75]

The Japanese Experiment Module Kib, was fabricated in various technology manufacturing facilities in Japan, at the NASDA (now JAXA) Tsukuba Space Center, and the Institute of Space and Astronautical Science. The Kibo module was transported by ship and flown by aircraft to the KSC Space Station Processing Facility.[76]

The Mobile Servicing System, consisting of the Canadarm2 and the Dextre grapple fixture, was manufactured at various factories in Canada (such as the David Florida Laboratory) and the United States, under contract by the Canadian Space Agency. The mobile base system, a connecting framework for Canadarm2 mounted on rails, was built by Northrop Grumman.

The assembly of the International Space Station, a major endeavour in space architecture, began in November 1998.[3] Russian modules launched and docked robotically, with the exception of Rassvet. All other modules were delivered by the Space Shuttle, which required installation by ISS and shuttle crewmembers using the Canadarm2 (SSRMS) and extra-vehicular activities (EVAs); as of 5June2011[update], they had added 159 components during more than 1,000 hours of EVA (see List of ISS spacewalks). 127 of these spacewalks originated from the station, and the remaining 32 were launched from the airlocks of docked Space Shuttles.[77] The beta angle of the station had to be considered at all times during construction.[78]

The first module of the ISS, Zarya, was launched on 20 November 1998 on an autonomous Russian Proton rocket. It provided propulsion, attitude control, communications, electrical power, but lacked long-term life support functions. Two weeks later, a passive NASA module Unity was launched aboard Space Shuttle flight STS-88 and attached to Zarya by astronauts during EVAs. This module has two Pressurised Mating Adapters (PMAs), one connects permanently to Zarya, the other allowed the Space Shuttle to dock to the space station. At that time, the Russian station Mir was still inhabited, and the ISS remained uncrewed for two years. On 12 July 2000, Zvezda was launched into orbit. Preprogrammed commands on board deployed its solar arrays and communications antenna. It then became the passive target for a rendezvous with Zarya and Unity: it maintained a station-keeping orbit while the Zarya-Unity vehicle performed the rendezvous and docking via ground control and the Russian automated rendezvous and docking system. Zarya's computer transferred control of the station to Zvezda's computer soon after docking. Zvezda added sleeping quarters, a toilet, kitchen, CO2 scrubbers, dehumidifier, oxygen generators, exercise equipment, plus data, voice and television communications with mission control. This enabled permanent habitation of the station.[79][80]

The first resident crew, Expedition 1, arrived in November 2000 on Soyuz TM-31. At the end of the first day on the station, astronaut Bill Shepherd requested the use of the radio call sign "Alpha", which he and cosmonaut Krikalev preferred to the more cumbersome "International Space Station".[81] The name "Alpha" had previously been used for the station in the early 1990s,[82] and its use was authorised for the whole of Expedition 1.[83] Shepherd had been advocating the use of a new name to project managers for some time. Referencing a naval tradition in a pre-launch news conference he had said: "For thousands of years, humans have been going to sea in ships. People have designed and built these vessels, launched them with a good feeling that a name will bring good fortune to the crew and success to their voyage."[84] Yuri Semenov, the President of Russian Space Corporation Energia at the time, disapproved of the name "Alpha" as he felt that Mir was the first modular space station, so the names "Beta" or "Mir2" for the ISS would have been more fitting.[83][85][86]

Expedition 1 arrived midway between the flights of STS-92 and STS-97. These two Space Shuttle flights each added segments of the station's Integrated Truss Structure, which provided the station with Ku-band communication for US television, additional attitude support needed for the additional mass of the USOS, and substantial solar arrays supplementing the station's four existing solar arrays.[87]

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 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.

The expansion schedule was interrupted by the Space Shuttle Columbia disaster in 2003 and a resulting hiatus in flights. The Space Shuttle was grounded until 2005 with STS-114 flown by Discovery.[88]

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 pressurised modules could be accommodated, and the Harmony node and Columbus European laboratory were added. These were soon followed by the first two components of Kib. 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 Kib was delivered in July 2009 on STS-127, followed by the Russian Poisk module. The third node, Tranquility, was delivered in February 2010 during STS-130 by the Space Shuttle Endeavour, alongside the Cupola, followed in May 2010 by the penultimate Russian module, Rassvet. 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.[89] The last pressurised module of the USOS, Leonardo, was brought to the station in February 2011 on the final flight of Discovery, STS-133.[90] The Alpha Magnetic Spectrometer was delivered by Endeavour on STS-134 the same year.[91]

As of June2011[update], the station consisted of 15 pressurised modules and the Integrated Truss Structure. Five modules are still to be launched, including the Nauka with the European Robotic Arm, the Prichal module, and two power modules called NEM-1 and NEM-2.[92] As of March2019[update], Russia's future primary research module Nauka is set to launch in the summer of 2020, along with the European Robotic Arm which will be able to relocate itself to different parts of the Russian modules of the station.[93]

The gross mass of the station changes over time. The total launch mass of the modules on orbit is about 417,289kg (919,965lb) (as of 3September2011[update]).[94] The mass of experiments, spare parts, personal effects, crew, foodstuff, clothing, propellants, water supplies, gas supplies, docked spacecraft, and other items add to the total mass of the station. Hydrogen gas is constantly vented overboard by the oxygen generators.

Technical blueprint of components

The ISS is a third generation[95] modular space station.[96] Modular stations can allow modules to be added to or removed from the existing structure, allowing greater flexibility.

Below is a diagram of major station components. The blue areas are pressurised sections accessible by the crew without using spacesuits. The station's unpressurised superstructure is indicated in red. Other unpressurised components are yellow. The Unity node joins directly to the Destiny laboratory. For clarity, they are shown apart.

Zarya (Russian: , lit.'Dawn'), also known as the Functional Cargo Block or FGB (from the Russian: "- ", lit.'Funktsionalno-gruzovoy blok' or ), is the first module of the ISS to be launched.[97] The FGB provided electrical power, storage, propulsion, and guidance to the ISS during the initial stage of assembly. With the launch and assembly in orbit of other modules with more specialised functionality, Zarya is now[when?] primarily used for storage, both inside the pressurised section and in the externally mounted fuel tanks. The Zarya is a descendant of the TKS spacecraft designed for the Russian Salyut program. The name Zarya, which means sunrise,[97] was given to the FGB because it signified the dawn of a new era of international cooperation in space. Although it was built by a Russian company, it is owned by the United States.[98]

Zarya was built from December 1994 to January 1998 at the Khrunichev State Research and Production Space Center (KhSC) in Moscow.[97]

Zarya was launched on 20November 1998 on a Russian Proton rocket from Baikonur Cosmodrome Site 81 in Kazakhstan to a 400 kilometres (250mi) high orbit with a designed lifetime of at least 15 years. After Zarya reached orbit, STS-88 launched on 4 December 1998 to attach the Unity module.

The Unity connecting module, also known as Node 1, is the first US-built component of the ISS. It connects the Russian and US segments of the station, and is where crew eat meals together.

The module is cylindrical in shape, with six berthing locations (forward, aft, port, starboard, zenith, and nadir) facilitating connections to other modules. Unity measures 4.57 metres (15.0ft) in diameter, is 5.47 metres (17.9ft) long, made of steel, and was built for NASA by Boeing in a manufacturing facility at the Marshall Space Flight Center in Huntsville, Alabama. Unity is the first of the three connecting modules; the other two are Harmony and Tranquility.

Unity was carried into orbit as the primary cargo of the Space Shuttle Endeavour on STS-88, the first Space Shuttle mission dedicated to assembly of the station. On 6 December 1998, the STS-88 crew mated the aft berthing port of Unity with the forward hatch of the already orbiting Zarya module. This was the first connection made between two station modules.

Zvezda (Russian: , meaning "star"), Salyut DOS-8, also known as the Zvezda Service Module, is a module of the ISS. It was the third module launched to the station, and provides all of the station's life support systems, some of which are supplemented in the USOS, as well as living quarters for two crew members. It is the structural and functional center of the Russian Orbital Segment, which is the Russian part of the ISS. Crew assemble here to deal with emergencies on the station.[99][100][101]

The basic structural frame of Zvezda, known as "DOS-8", was initially built in the mid-1980s to be the core of the Mir-2 space station. This means that Zvezda is similar in layout to the core module (DOS-7) of the Mir space station. It was in fact labeled as Mir-2 for quite some time in the factory. Its design lineage thus extends back to the original Salyut stations. The space frame was completed in February 1985 and major internal equipment was installed by October 1986.

The rocket used for launch to the ISS carried advertising; it was emblazoned with the logo of Pizza Hut restaurants,[102][103][104] for which they are reported to have paid more than US$1 million.[105] The money helped support Khrunichev State Research and Production Space Center and the Russian advertising agencies that orchestrated the event.[106]

On 26 July 2000, Zvezda became the third component of the ISS when it docked at the aft port of Zarya. (U.S. Unity module had already been attached to the Zarya.) Later in July, the computers aboard Zarya handed over ISS commanding functions to computers on Zvezda.[107]

The Destiny module, also known as the U.S. Lab, is the primary operating facility for U.S. research payloads aboard the International Space Station (ISS).[108][109] It was berthed to the Unity module and activated over a period of five days in February 2001.[110] Destiny is NASA's first permanent operating orbital research station since Skylab was vacated in February 1974.

The Boeing Company began construction of the 14.5-tonne (32,000lb) research laboratory in 1995 at the Michoud Assembly Facility and then the Marshall Space Flight Center in Huntsville, Alabama.[108] Destiny was shipped to the Kennedy Space Center in Florida in 1998, and was turned over to NASA for pre-launch preparations in August 2000. It launched on 7February 2001 aboard the Space Shuttle Atlantis on STS-98.[110]

The Quest Joint Airlock, previously known as the Joint Airlock Module, is the primary airlock for the ISS. Quest was designed to host spacewalks with both Extravehicular Mobility Unit (EMU) spacesuits and Orlan space suits. The airlock was launched on STS-104 on 14July 2001. Before Quest was attached, Russian spacewalks using Orlan suits could only be done from the Zvezda service module, and American spacewalks using EMUs were only possible when a Space Shuttle was docked. The arrival of Pirs docking compartment on 16September 2001 provided another airlock from which Orlan spacewalks can be conducted.[citation needed]

The Pirs module attached to the ISS.

Poisk after arriving at the ISS on 12 November 2009.

Pirs (Russian: , lit.'pier') and Poisk (Russian: , lit.'search') are Russian airlock modules, each having two identical hatches. An outward-opening hatch on the Mir space station failed after it swung open too fast after unlatching, because of a small amount of air pressure remaining in the airlock.[111] All EVA hatches on the ISS open inwards and are pressure-sealing. Pirs was used to store, service, and refurbish Russian Orlan suits and provided contingency entry for crew using the slightly bulkier American suits. The outermost docking ports on both airlocks allow docking of Soyuz and Progress spacecraft, and the automatic transfer of propellants to and from storage on the ROS.[112]

Pirs was launched on 14September 2001, as ISS Assembly Mission 4R, on a Russian Soyuz-U rocket, using a modified Progress spacecraft, Progress M-SO1, as an upper stage. Poisk was launched on 10November 2009[113][114] attached to a modified Progress spacecraft, called Progress M-MIM2, on a Soyuz-U rocket from Launch Pad 1 at the Baikonur Cosmodrome in Kazakhstan.

Harmony, also known as Node 2, is the "utility hub" of the ISS. It connects the laboratory modules of the United States, Europe and Japan, as well as providing electrical power and electronic data. Sleeping cabins for four of the six crew are housed here.[115]

Harmony was successfully launched into space aboard Space Shuttle flight STS-120 on 23October 2007.[116][117] After temporarily being attached to the port side of the Unity node,[118] it was moved to its permanent location on the forward end of the Destiny laboratory on 14November 2007.[119] Harmony added 2,666 cubic feet (75.5m3) to the station's living volume, an increase of almost 20 percent, from 15,000cuft (420m3) to 17,666cuft (500.2m3). Its successful installation meant that from NASA's perspective, the station was "U.S. Core Complete".

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.

ESA and the Italian Space Agency had Tranquility built by Thales Alenia Space. A ceremony on 20November 2009 transferred ownership of the module to NASA.[120] On 8February 2010, NASA launched the module on the Space Shuttle's STS-130 mission.

Columbus is a science laboratory that is part of the ISS and is the largest single contribution to the ISS made by the European Space Agency (ESA).

The Columbus laboratory was flown to the Kennedy Space Center (KSC) in Florida in an Airbus Beluga. It was launched aboard Space Shuttle Atlantis on 7February 2008 on flight STS-122. It is designed for ten years of operation. The module is controlled by the Columbus Control Centre, located at the German Space Operations Centre, part of the German Aerospace Center in Oberpfaffenhofen near Munich, Germany.

The European Space Agency has spent 1.4billion (about US$2 billion) on building Columbus, including the experiments that will orbit in Columbus and the ground control infrastructure necessary to operate the experiments.[121]

The Japanese Experiment Module (JEM), nicknamed Kibo (, Kib, Hope), is a Japanese science module for the ISS developed by JAXA. It is the largest single ISS module, and is attached to the Harmony module. The first two pieces of the module were launched on Space Shuttle missions STS-123 and STS-124. The third and final components were launched on STS-127.[122]

Experiment Logistics Module

Experiment Logistics Module

Remote Manipulator System

The Cupola is an ESA-built observatory module of the ISS. Its name derives from the Italian word cupola, which means "dome". Its seven windows are used to conduct experiments, dockings and observations of Earth. It was launched aboard Space Shuttle mission STS-130 on 8February 2010 and attached to the Tranquility (Node 3) module. With the Cupola attached, ISS assembly reached 85 percent completion. The Cupola's central window has a diameter of 80cm (31in).[123]

Rassvet (Russian: ; lit. "dawn"), also known as the Mini-Research Module 1 (MRM-1) (Russian: , 1) and formerly known as the Docking Cargo Module (DCM), is a component of the ISS. The module's design is similar to the Mir Docking Module launched on STS-74 in 1995. Rassvet is primarily used for cargo storage and as a docking port for visiting spacecraft. It was flown to the ISS aboard Space Shuttle Atlantis on the STS-132 mission on 14May 2010,[124] and was connected to the ISS on 18 May.[125] The hatch connecting Rassvet with the ISS was first opened on 20 May.[126] On 28June 2010, the Soyuz TMA-19 spacecraft performed the first docking with the module.[127]

The Leonardo Permanent Multipurpose Module (PMM) is a module of the ISS. It was flown into space aboard the Space Shuttle on STS-133 on 24February 2011 and installed on 1March. Leonardo is primarily used for storage of spares, supplies and waste on the ISS, which was until then stored in many different places within the space station. The Leonardo PMM was a Multi-Purpose Logistics Module (MPLM) before 2011, but was modified into its current configuration. It was formerly one of three MPLM used for bringing cargo to and from the ISS with the Space Shuttle. The module was named for Italian polymath Leonardo da Vinci.

The Bigelow Expandable Activity Module (BEAM) is an experimental expandable space station module developed by Bigelow Aerospace, under contract to NASA, for testing as a temporary module on the ISS from 2016 to at least 2020. It arrived at the ISS on 10April 2016,[128] was berthed to the station on 16April, and was expanded and pressurised on 28May 2016.

The International Docking Adapter (IDA) is a spacecraft docking system adapter developed to convert APAS-95 to the NASA Docking System (NDS)/International Docking System Standard (IDSS). An IDA is placed on each of the ISS' two open Pressurised Mating Adapters (PMAs), both of which are connected to the Harmony module.

IDA-1 was lost during the launch failure of SpaceX CRS-7 on 28June 2015.[129][130][131]

IDA-2 was launched on SpaceX CRS-9 on 18July 2016.[132] It was attached and connected to PMA-2 during a spacewalk on 19August 2016.[133] First docking was achieved with the arrival of Crew Dragon Demo-1 on 3March 2019.[134]

IDA-3 was launched on the SpaceX CRS-18 mission in July 2019.[135] IDA-3 is constructed mostly from spare parts to speed construction.[136] It was attached and connected to PMA-3 during a spacewalk on 21August 2019.[137]

The ISS has a large number of external components that do not require pressurisation. The largest of these is the Integrated Truss Structure (ITS), to which the station's main solar arrays and thermal radiators are mounted.[138] The ITS consists of ten separate segments forming a structure 108.5 m (356 ft) long.[3]

The station was intended to have several smaller external components, such as six robotic arms, three External Stowage Platforms (ESPs) and four ExPRESS Logistics Carriers (ELCs).[139][140] While these platforms allow experiments (including MISSE, the STP-H3 and the Robotic Refueling Mission) to be deployed and conducted in the vacuum of space by providing electricity and processing experimental data locally, their primary function is to store spare Orbital Replacement Units (ORUs). ORUs are parts that can be replaced when they fail or pass their design life, including pumps, storage tanks, antennas, and battery units. Such units are replaced either by astronauts during EVA or by robotic arms.[141] Several shuttle missions were dedicated to the delivery of ORUs, including STS-129,[142] STS-133[143] and STS-134.[144] As of January2011[update], only one other mode of transportation of ORUs had been utilisedthe Japanese cargo vessel HTV-2which delivered an FHRC and CTC-2 via its Exposed Pallet (EP).[145][needs update]

There are also smaller exposure facilities mounted directly to laboratory modules; the Kib Exposed Facility serves as an external "porch" for the Kib complex,[146] and a facility on the European Columbus laboratory provides power and data connections for experiments such as the European Technology Exposure Facility[147][148] and the Atomic Clock Ensemble in Space.[149] A remote sensing instrument, SAGE III-ISS, was delivered to the station in February 2017 aboard CRS-10,[150] and the NICER experiment was delivered aboard CRS-11 in June 2017.[151] The largest scientific payload externally mounted to the ISS is the Alpha Magnetic Spectrometer (AMS), a particle physics experiment launched on STS-134 in May 2011, and mounted externally on the ITS. The AMS measures cosmic rays to look for evidence of dark matter and antimatter.[152][153]

The commercial Columbus External Payload Facility#Bartolomeo External Payload Hosting Platform, manufactured by Airbus, was launched on 6 March 2020 aboard CRS-20 and be attached to the European Columbus module. It will provide a further 12 external payload slots, supplementing the eight on the ExPRESS Logistics Carriers, ten on Kib, and four on Columbus. The system is designed to be robotically serviced and will require no astronaut intervention. It is named after Christopher Columbus's younger brother.[154][155][156]

The Integrated Truss Structure serves as a base for the station's primary remote manipulator system, called the Mobile Servicing System (MSS), which is composed of three main components. Canadarm2, the largest robotic arm on the ISS, has a mass of 1,800 kilograms (4,000lb) and is used to dock and manipulate spacecraft and modules on the USOS, hold crew members and equipment in place during EVAs and move Dextre around to perform tasks.[157] Dextre is a 1,560kg (3,440lb) robotic manipulator with two arms, a rotating torso and has power tools, lights and video for replacing orbital replacement units (ORUs) and performing other tasks requiring fine control.[158] The Mobile Base System (MBS) is a platform which rides on rails along the length of the station's main truss. It serves as a mobile base for Canadarm2 and Dextre, allowing the robotic arms to reach all parts of the USOS.[159] To gain access to the Russian Segment a grapple fixture was added to Zarya on STS-134, so that Canadarm2 can inchworm itself onto the ROS.[160] Also installed during STS-134 was the 15m (50ft) Orbiter Boom Sensor System (OBSS), which had been used to inspect heat shield tiles on Space Shuttle missions and can be used on station to increase the reach of the MSS.[160] Staff on Earth or the station can operate the MSS components via remote control, performing work outside the station without space walks.

Japan's Remote Manipulator System, which services the Kib Exposed Facility,[161] was launched on STS-124 and is attached to the Kib Pressurised Module.[162] The arm is similar to the Space Shuttle arm as it is permanently attached at one end and has a latching end effector for standard grapple fixtures at the other.

The European Robotic Arm, which will service the Russian Orbital Segment, will be launched alongside the Multipurpose Laboratory Module in 2020.[163] The ROS does not require spacecraft or modules to be manipulated, as all spacecraft and modules dock automatically and may be discarded the same way. Crew use the two Strela (Russian: ; lit. Arrow) cargo cranes during EVAs for moving crew and equipment around the ROS. Each Strela crane has a mass of 45kg (99lb).

Nauka (Russian: ; lit. Science), also known as the Multipurpose Laboratory Module (MLM), (Russian: , or ), is a component of the ISS which has not yet been launched into space. The MLM is funded by the Roscosmos State Corporation. In the original ISS plans, Nauka was to use the location of the Docking and Stowage Module. Later, the DSM was replaced by the Rassvet module and it was moved to Zarya's nadir port. Planners anticipate Nauka will dock at Zvezda's nadir port, replacing Pirs.[164]

The launch of Nauka, initially planned for 2007, has been repeatedly delayed for various reasons. As of April2020[update], the launch to the ISS is assigned to no earlier than November 2020.[165] After this date, the warranties of some of Nauka's systems will expire.

Prichal, also known as Uzlovoy Module or UM (Russian: "", Nodal Module Berth),[166] is a 4-tonne (8,800lb)[167] ball-shaped module that will allow docking of two scientific and power modules during the final stage of the station assembly, and provide the Russian segment additional docking ports to receive Soyuz MS and Progress MS spacecraft. UM is due to be launched in 2022.[168] It will be integrated with a special version of the Progress cargo ship and launched by a standard Soyuz rocket, docking to the nadir port of the Nauka module. One port is equipped with an active hybrid docking port, which enables docking with the MLM module. The remaining five ports are passive hybrids, enabling docking of Soyuz and Progress vehicles, as well as heavier modules and future spacecraft with modified docking systems. The node module was intended to serve as the only permanent element of the cancelled OPSEK.[169][170]

Science Power Module 1 (SPM-1, also known as NEM-1) and Science Power Module 2 (SPM-2, also known as NEM-2) are modules planned to arrive at the ISS not earlier than 2023.[165][168][171] It is going to dock to the Prichal module, which is planned to be attached to the Nauka module.[citation needed] If Nauka is cancelled, then the Prichal, SPM-1, and SPM-2 would dock at the zenith port of Zvezda. SPM-1 and SPM-2 would also be required components for the OPSEK space station.[172]

The NanoRacks Bishop Airlock Module is a commercially-funded airlock module intended to be launched to the ISS on SpaceX CRS-21 in August 2020.[173][174] The module is being built by NanoRacks, Thales Alenia Space, and Boeing.[175] It will be used to deploy CubeSats, small satellites, and other external payloads for NASA, CASIS, and other commercial and governmental customers.[176]

In January 2020, NASA awarded Axiom Space a contract to build a commercial module for the space station with it launching in 2024. The contract is under the NextSTEP2 program. NASA said it will begin negotiations with Axiom on a firm-fixed-price contract to build and deliver the module, which will attach to the forward port on space station's Harmony module, or Node 2. Although NASA has only commissioned one module, Axiom plans to build an entire segment which would consists of five modules. These modules would include a node module, an orbital research and manufacturing facility, a crew habitat, and a "large-windowed Earth observatory". The Axiom segment would greatly increase the capabilities and value of the station and allow for larger crews and private spaceflight by other organisations. Axiom plans to turn its segment into its own space station once the ISS is decommissioned and would let it act as a successor to the station.[177][178][179]

Several modules planned for the station were cancelled over the course of the ISS program. Reasons include budgetary constraints, the modules becoming unnecessary, and station redesigns after the 2003 Columbia disaster. The US Centrifuge Accommodations Module would have hosted science experiments in varying levels of artificial gravity.[180] The US Habitation Module would have served as the station's living quarters. Instead, the sleep stations are now spread throughout the station.[181] The US Interim Control Module and ISS Propulsion Module would have replaced the functions of Zvezda in case of a launch failure.[182] Two Russian Research Modules were planned for scientific research.[183] They would have docked to a Russian Universal Docking Module.[184] The Russian Science Power Platform would have supplied power to the Russian Orbital Segment independent of the ITS solar arrays.

The critical systems are the atmosphere control system, the water supply system, the food supply facilities, the sanitation and hygiene equipment, and fire detection and suppression equipment. The Russian Orbital Segment's life support systems are contained in the Zvezda service module. Some of these systems are supplemented by equipment in the USOS. The MLM Nauka laboratory has a complete set of life support systems.

The atmosphere on board the ISS is similar to the Earth's.[185] Normal air pressure on the ISS is 101.3kPa (14.69psi);[186] the same as at sea level on Earth. An Earth-like atmosphere offers benefits for crew comfort, and is much safer than a pure oxygen atmosphere, because of the increased risk of a fire such as that responsible for the deaths of the Apollo 1 crew.[187] Earth-like atmospheric conditions have been maintained on all Russian and Soviet spacecraft.[188]

The Elektron system aboard Zvezda and a similar system in Destiny generate oxygen aboard the station.[189] The crew has a backup option in the form of bottled oxygen and Solid Fuel Oxygen Generation (SFOG) canisters, a chemical oxygen generator system.[190] Carbon dioxide is removed from the air by the Vozdukh system in Zvezda. Other by-products of human metabolism, such as methane from the intestines and ammonia from sweat, are removed by activated charcoal filters.[190]

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