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55-456: Orbital Reef is an under development low Earth orbit (LEO) space station being designed by Blue Origin and Sierra Nevada Corporation 's Sierra Space for commercial space activities and space tourism uses. Blue Origin has referred to it as a "mixed-use business park". The companies released preliminary concepts for the station on 25 October 2021. The station is being designed to support 10 persons in 830 m of volume. As of March 2022,

110-442: A crew capsule to service its proposed space station Orbital Reef in low-Earth orbit as a part of commercial ventures proposed by ISRO before the launch of the planned Indian Space Station . By October 2023, NASA reported they had paid out only US$ 24 million of the $ 130 million contract for completion of specific milestones. Also in early October, issues between Sierra Space and Blue Origin became public, and CNBC reported that

165-567: A domino effect known as Kessler syndrome . NASA's Orbital Debris Program tracks over 25,000 objects larger than 10 cm diameter in LEO, while the estimated number between 1 and 10 cm is 500,000, and the number of particles bigger than 1 mm exceeds 100 million. The particles travel at speeds up to 7.8 km/s (28,000 km/h; 17,500 mph), so even a small impact can severely damage a spacecraft. [REDACTED]  This article incorporates public domain material from websites or documents of

220-702: A longer lifetime at the cost of requiring regular support launches. The ISS is divided into two main sections, the Russian Orbital Segment (ROS) and the US Orbital Segment (USOS). The first module of the ISS, Zarya , was launched in 1998. The Russian Orbital Segment's "second-generation" modules were able to launch on Proton , fly to the correct orbit, and dock themselves without human intervention. Connections are automatically made for power, data, gases, and propellants. The Russian autonomous approach allows

275-534: A satellite into a LEO, and a satellite there needs less powerful amplifiers for successful transmission, LEO is used for many communication applications, such as the Iridium phone system . Some communication satellites use much higher geostationary orbits and move at the same angular velocity as the Earth as to appear stationary above one location on the planet. Unlike geosynchronous satellites , satellites in low orbit have

330-458: A second crew to visit, bringing a new spacecraft with them; the Soyuz ferry could spend 90 days in space, at which point it needed to be replaced by a fresh Soyuz spacecraft. This allowed for a crew to man the station continually. The American Skylab (1973–1979) was also equipped with two docking ports, like second-generation stations, but the extra port was never used. The presence of a second port on

385-441: A small field of view and can only observe and communicate with a fraction of the Earth at a given time. This means that a large network (or constellation ) of satellites is required to provide continuous coverage. Satellites at lower altitudes of orbit are in the atmosphere and suffer from rapid orbital decay , requiring either periodic re-boosting to maintain stable orbits, or the launching of replacements for those that re-enter

440-564: A space station occurred in Edward Everett Hale 's 1868 " The Brick Moon ". The first to give serious, scientifically grounded consideration to space stations were Konstantin Tsiolkovsky and Hermann Oberth about two decades apart in the early 20th century. In 1929, Herman Potočnik 's The Problem of Space Travel was published, the first to envision a "rotating wheel" space station to create artificial gravity . Conceptualized during

495-433: A subset of LEO. These orbits, with low orbital inclination , allow rapid revisit times over low-latitude locations on Earth. Prograde equatorial LEOs also have lower delta-v launch requirements because they take advantage of the Earth's rotation. Other useful LEO orbits including polar orbits and Sun-synchronous orbits have a higher inclinations to the equator and provide coverage for higher latitudes on Earth. Some of

550-579: A variety of challenges to human habitability, including short-term problems such as the limited supplies of air, water, and food and the need to manage waste heat , and long-term ones such as weightlessness and relatively high levels of ionizing radiation . These conditions can create long-term health problems for space-station inhabitants, including muscle atrophy , bone deterioration , balance disorders , eyesight disorders , and elevated risk of cancer . Future space habitats may attempt to address these issues, and could be designed for occupation beyond

605-477: A year, all aboard Mir . Many spacecraft are used to dock with the space stations. Soyuz flight T-15 in March to July 1986 was the first and as of 2016, only spacecraft to visit two different space stations, Mir and Salyut 7 . The International Space Station has been supported by many different spacecraft. The Tiangong space station is supported by the following spacecraft: The Tiangong program relied on

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660-562: Is a complex vehicle that must incorporate many interrelated subsystems, including structure, electrical power, thermal control, attitude determination and control , orbital navigation and propulsion, automation and robotics, computing and communications, environmental and life support, crew facilities, and crew and cargo transportation. Stations must serve a useful role, which drives the capabilities required. Space stations are made from durable materials that have to weather space radiation , internal pressure, micrometeoroids , thermal effects of

715-535: Is not designed for disassembly and must be deorbited as one mass. The Axiom Orbital Segment is a planned commercial segment to be added to the ISS starting in the mid-2020s. Axiom Space gained NASA approval for the venture in January 2020. Up to three Axiom modules will attach to the International Space Station. The first module, Hab One, is expected to be launched at the end of 2026 and will be docked to

770-496: Is only slightly less than on the Earth's surface. This is because the distance to LEO from the Earth's surface is much less than the Earth's radius. However, an object in orbit is in a permanent free fall around Earth, because in orbit the gravitational force and the centrifugal force balance each other out. As a result, spacecraft in orbit continue to stay in orbit, and people inside or outside such craft continuously experience weightlessness . Objects in LEO orbit Earth between

825-461: Is used for the area of space below an altitude of 2,000 km (1,200 mi) (about one-third of Earth's radius). Objects in orbits that pass through this zone, even if they have an apogee further out or are sub-orbital , are carefully tracked since they present a collision risk to the many LEO satellites. No human spaceflights other than the lunar missions of the Apollo program (1968-1972) and

880-502: The Gemini program paved the way and achieved the first space rendezvous (undocked) with Gemini 6 and Gemini 7 in 1965. Subsequently in 1966 Neil Armstrong performed on Gemini 8 the first ever space docking, while in 1967 Kosmos 186 and Kosmos 188 were the first spacecrafts that docked automatically. In January 1969, Soyuz 4 and Soyuz 5 performed the first docked, but not internal, crew transfer, and in March, Apollo 9 performed

935-610: The National Aeronautics and Space Administration . Space station A space station (or orbital station ) is a spacecraft which remains in orbit and hosts humans for extended periods of time. It therefore is an artificial satellite featuring habitation facilities . The purpose of maintaining a space station varies depending on the program. Most often space stations have been research stations , but they have also served military or commercial uses , such as hosting space tourists . Space stations have been hosting

990-668: The Salyut successor Mir . Uninterrupted occupation of stations has been achieved since the operational transition from the Mir to the ISS , with its first occupation in 2000. The ISS has hosted the highest number of people in orbit at the same time, reaching 13 for the first time during the eleven day docking of STS-127 in 2009. The duration record for a single spaceflight is 437.75 days, set by Valeri Polyakov aboard Mir from 1994 to 1995. As of 2021 , four cosmonauts have completed single missions of over

1045-552: The Second World War , the " sun gun " was a theoretical orbital weapon orbiting Earth at a height of 8,200 kilometres (5,100 mi). No further research was ever conducted. In 1951, Wernher von Braun published a concept for a rotating wheel space station in Collier's Weekly , referencing Potočnik's idea. However, development of a rotating station was never begun in the 20th century. The first human flew to space and concluded

1100-429: The oblateness of Earth's spheroid figure and local topography . While definitions based on altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law , this corresponds to a semi-major axis of 8,413 km (5,228 mi). For circular orbits, this in turn corresponds to an altitude of 2,042 km (1,269 mi) above

1155-415: The 2024 Polaris Dawn have taken place beyond LEO. All space stations to date have operated geocentric within LEO. A wide variety of sources define LEO in terms of altitude . The altitude of an object in an elliptic orbit can vary significantly along the orbit. Even for circular orbits , the altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits ) due to

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1210-461: The ISS and China 's Tiangong Space Station (TSS), which have been occupied since October 2000 with Expedition 1 and since June 2022 with Shenzhou 14 . The highest number of people at the same time on one space station has been 13, first achieved with the eleven day docking to the ISS of the 127th Space Shuttle mission in 2009. The record for most people on all space stations at the same time has been 17, first on May 30, 2023, with 11 people on

1265-467: The ISS and 6 on the TSS. Space stations are most often modular , featuring docking ports , through which they are built and maintained, allowing the joining or movement of modules and the docking of other spacecrafts for the exchange of people, supplies and tools. While space stations generally do not leave their orbit, they do feature thrusters for station keeping . The first mention of anything resembling

1320-577: The ISS on the SpaceX CRS-8 resupply mission. This module, based on NASA research in the 1990s, weighs 1,400 kilograms (3,100 lb) and was transported while compressed before being attached to the ISS by the space station arm and inflated to provide a 16 cubic metres (21 cu yd) volume. Whilst it was initially designed for a 2   year lifetime it was still attached and being used for storage in August 2022. The space station environment presents

1375-437: The ISS, orbiting today. Each crew member stays aboard the station for weeks or months but rarely more than a year. Early stations were monolithic designs that were constructed and launched in one piece, generally containing all their supplies and experimental equipment. A crew would then be launched to join the station and perform research. After the supplies had been consumed, the station was abandoned. The first space station

1430-498: The LEO region but are not in a LEO orbit because they re-enter the atmosphere . The distinction between LEO orbits and the LEO region is especially important for analysis of possible collisions between objects which may not themselves be in LEO but could collide with satellites or debris in LEO orbits. The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s (4.8 mi/s), which translates to 28,000 km/h (17,000 mph). However, this depends on

1485-509: The Orbital Reef website had not been updated in over a year, and that no hiring for the project is currently being done, as both companies have other larger space projects that are higher priorities for them. CNBC also reported that the two partners on the project may go their separate ways. However, after talks between the companies, both companies tweeted on their Twitter accounts on 10 October that they were continuing to work with each other on

1540-813: The South Pacific Ocean. The Tiangong Space Station ( Chinese : 天宫 ; pinyin : Tiāngōng ; lit. 'Heavenly Palace'), the first module of which was launched on 29 April 2021, is in low Earth orbit, 340 to 450 kilometres above the Earth at an orbital inclination of 42° to 43°. Its planned construction via 11 total launches across 2021–2022 was intended to extend the core module with two laboratory modules, capable of hosting up to six crew. These space stations have been announced by their host entity and are currently in planning, development or production. The launch date listed here may change as more information becomes available. (~23,548 cu ft) (~15892 cu ft) While originally Lockheed Martin

1595-575: The assembly of space stations prior to the launch of crew. The Russian "second-generation" modules are able to be reconfigured to suit changing needs. As of 2009, RKK Energia was considering the removal and reuse of some modules of the ROS on the Orbital Piloted Assembly and Experiment Complex after the end of mission is reached for the ISS. However, in September 2017, the head of Roscosmos said that

1650-433: The atmosphere. The effects of adding such quantities of vaporized metals to Earth's stratosphere are potentially of concern but currently unknown. The LEO environment is becoming congested with space debris because of the frequency of object launches. This has caused growing concern in recent years, since collisions at orbital velocities can be dangerous or deadly. Collisions can produce additional space debris, creating

1705-741: The contract deliverables for Phase 1. In March 2024, NASA reported that Blue Origin had passed 4 test milestones relating to Orbital Reef. More critical testing was reported to occur in Summer 2024 with successful burst tests of Sierra Space's LIFE modules. Orbital Reef’s design is reported to be modular in nature, to provide the greatest amount of customization and compatibility. It will reportedly be designed to accept docking from almost every in operation spacecraft like SpaceX Dragon 2 , Soyuz (spacecraft) , Dream Chaser , and Boeing Starliner The initial modules will be the: LIFE , Node, Core, and Research Modules. Low Earth orbit The term LEO region

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1760-550: The crewed Shenzhou 10 in 2013. According to the China Manned Space Engineering Office , Tiangong-1 reentered over the South Pacific Ocean , northwest of Tahiti , on 2 April 2018 at 00:15 UTC. A second space laboratory Tiangong-2 was launched in September 2016, while a plan for Tiangong-3 was merged with Tiangong-2. The station made a controlled reentry on 19 July 2019 and burned up over

1815-455: The denser part of the atmosphere and below the inner Van Allen radiation belt . They encounter atmospheric drag from gases in the thermosphere (approximately 80–600 km above the surface) or exosphere (approximately 600 km or 400 mi and higher), depending on orbit height. Satellites in orbits that reach altitudes below 300 km (190 mi) decay quickly due to atmospheric drag. Equatorial low Earth orbits ( ELEO ) are

1870-522: The design and the program requirements. The 2021 contract with Blue was just the first phase of two by which NASA is aiming to maintain an uninterrupted U.S. presence in low-Earth orbit by transitioning from the International Space Station to other platforms. In June 2023, ISRO chairman S Somanath told the Times of India that Blue Origin is “very keen” on considering using an Indian rocket as

1925-496: The differential viability of the microbial cells, as a function of phylogenetic lineage, remain elusive. Like uncrewed spacecraft close to the Sun, space stations in the inner Solar System generally rely on solar panels to obtain power. Space station air and water is brought up in spacecraft from Earth before being recycled. Supplemental oxygen can be supplied by a solid fuel oxygen generator . The last military-use space station

1980-403: The exact altitude of the orbit. Calculated for a circular orbit of 200 km (120 mi) the orbital velocity is 7.79 km/s (4.84 mi/s), but for a higher 1,500 km (930 mi) orbit the velocity is reduced to 7.12 km/s (4.42 mi/s). The launch vehicle's delta-v needed to achieve low Earth orbit starts around 9.4 km/s (5.8 mi/s). The pull of gravity in LEO

2035-471: The first ever internal transfer of astronauts between two docked spaceships. In 1971, the Soviet Union developed and launched the world's first space station, Salyut 1 . The Almaz and Salyut series were eventually joined by Skylab , Mir , and Tiangong-1 and Tiangong-2 . The hardware developed during the initial Soviet efforts remains in use, with evolved variants comprising a considerable part of

2090-647: The first generation of Starlink satellites used polar orbits which provide coverage everywhere on Earth. Later Starlink constellations orbit at a lower inclination and provide more coverage for populated areas. Higher orbits include medium Earth orbit (MEO), sometimes called intermediate circular orbit (ICO), and further above, geostationary orbit (GEO). Orbits higher than low orbit can lead to early failure of electronic components due to intense radiation and charge accumulation. In 2017, " very low Earth orbits " ( VLEO ) began to be seen in regulatory filings. These orbits, below about 450 km (280 mi), require

2145-521: The first orbit on April 12, 1961, with Vostok 1 . The Apollo program had in its early planning instead of a lunar landing a crewed lunar orbital flight and an orbital laboratory station in orbit of Earth, at times called Project Olympus , as two different possible program goals, until the Kennedy administration sped ahead and made the Apollo program focus on what was originally planned to come after it,

2200-450: The following spacecraft. The Mir space station was in orbit from 1986 to 2001 and was supported and visited by the following spacecraft: Research conducted on the Mir included the first long term space based ESA research project EUROMIR   95 which lasted 179   days and included 35 scientific experiments. During the first 20 years of operation of the International Space Station, there were around 3,000 scientific experiments in

2255-775: The forward port of Harmony , requiring relocation of the PMA-2 . Axiom Space plans to attach up to two additional modules to its first core module, and send private astronauts to inhabit the modules. The modules would later detach into the Axiom Station in a manner similar to Russia's proposed OPSEK. China's first space laboratory, Tiangong-1 was launched in September 2011. The uncrewed Shenzhou 8 then successfully performed an automatic rendezvous and docking in November 2011. The crewed Shenzhou 9 then docked with Tiangong-1 in June 2012, followed by

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2310-401: The lunar landing. The Project Olympus space station, or orbiting laboratory of the Apollo program, was proposed as an in-space unfolded structure with the Apollo command and service module docking. While never realized, the Apollo command and service module would perform docking maneuvers and eventually become a lunar orbiting module which was used for station-like purposes. But before that

2365-455: The mean radius of Earth, which is consistent with some of the upper altitude limits in some LEO definitions. The LEO region is defined by some sources as a region in space that LEO orbits occupy. Some highly elliptical orbits may pass through the LEO region near their lowest altitude (or perigee ) but are not in a LEO orbit because their highest altitude (or apogee ) exceeds 2,000 km (1,243 mi). Sub-orbital objects can also reach

2420-403: The new stations allowed Progress supply vehicles to be docked to the station, meaning that fresh supplies could be brought to aid long-duration missions. This concept was expanded on Salyut 7, which "hard docked" with a TKS tug shortly before it was abandoned; this served as a proof of concept for the use of modular space stations. The later Salyuts may reasonably be seen as a transition between

2475-509: The only continuous presence of humans in space . The first space station was Salyut 1 (1971), hosting the first crew, of the ill-fated Soyuz 11 . Consecutively space stations have been operated since Skylab (1973) and occupied since 1987 with the Salyut successor Mir . Uninterrupted occupation has been sustained since the operational transition from the Mir to the International Space Station (ISS), with its first occupation in 2000. Currently there are two fully operational space stations –

2530-417: The station was projected to be operational by 2027. Blue Origin and Sierra Space partnered with several other companies and institutions to submit the 2021 proposal: On 2 December 2021, NASA announced it had selected Blue Origin as one of three companies to develop concept designs of space stations and other commercial destinations in space. Blue Origin was awarded $ 130 million. The contract with Blue

2585-533: The sun and cold temperatures for long periods of time. They are typically made from stainless steel , titanium and high-quality aluminum alloys , with layers of insulation such as Kevlar as a ballistics shield protection. The International Space Station (ISS) has a single inflatable module, the Bigelow Expandable Activity Module , which was installed in April   2016 after being delivered to

2640-576: The technical feasibility of separating the station to form OPSEK had been studied, and there were now no plans to separate the Russian segment from the ISS. In contrast, the main US modules launched on the Space Shuttle and were attached to the ISS by crews during EVAs . Connections for electrical power, data, propulsion, and cooling fluids are also made at this time, resulting in an integrated block of modules that

2695-515: The two groups. Unlike previous stations, the Soviet space station Mir had a modular design ; a core unit was launched, and additional modules, generally with a specific role, were later added. This method allows for greater flexibility in operation, as well as removing the need for a single immensely powerful launch vehicle . Modular stations are also designed from the outset to have their supplies provided by logistical support craft, which allows for

2750-412: The use of novel technologies for orbit raising because they operate in orbits that would ordinarily decay too soon to be economically useful. A low Earth orbit requires the lowest amount of energy for satellite placement. It provides high bandwidth and low communication latency . Satellites and space stations in LEO are more accessible for crew and servicing. Since it requires less energy to place

2805-606: The weeks or months that current missions typically last. Possible solutions include the creation of artificial gravity by a rotating structure , the inclusion of radiation shielding , and the development of on-site agricultural ecosystems. Some designs might even accommodate large numbers of people, becoming essentially "cities in space" where people would reside semi-permanently. Molds that develop aboard space stations can produce acids that degrade metal, glass, and rubber. Despite an expanding array of molecular approaches for detecting microorganisms, rapid and robust means of assessing

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2860-402: Was Salyut 1 , which was launched by the Soviet Union on April 19, 1971. The early Soviet stations were all designated "Salyut", but among these, there were two distinct types: civilian and military. The military stations, Salyut 2 , Salyut 3 , and Salyut 5 , were also known as Almaz stations. The civilian stations Salyut 6 and Salyut 7 were built with two docking ports, which allowed

2915-624: Was included in the project, as of 2024, it appears their primary role has been filled by Airbus , to provide the main habitat for the station. As of 2024, they are no longer listed as a partner on Starlab's website. (14,126 cu ft) (29,000 cu ft) Two types of space stations have been flown: monolithic and modular. Monolithic stations consist of a single vehicle and are launched by one rocket. Modular stations consist of two or more separate vehicles that are launched independently and docked on orbit. Modular stations are currently preferred due to lower costs and greater flexibility. A space station

2970-410: Was one of three funded Space Act Agreements (SAA) that NASA issued for the first phase of its Commercial LEO Destinations program (CLD). Space Act Agreements provide limited funding for specific milestones to be achieved by the companies, and are distinct from more widely used Federal Acquisition Regulation FAR contracts used in most legacy NASA space programs, where NASA owns responsibility for both

3025-695: Was the Soviet Salyut 5 , which was launched under the Almaz program and orbited between 1976 and 1977. Space stations have harboured so far the only long-duration direct human presence in space. After the first station, Salyut 1 (1971), and its tragic Soyuz 11 crew, space stations have been operated consecutively since Skylab (1973–1974), having allowed a progression of long-duration direct human presence in space. Long-duration resident crews have been joined by visiting crews since 1977 ( Salyut 6 ), and stations have been occupied by consecutive crews since 1987 with

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