The US Orbital Segment (USOS) is the name given to the components of the
International Space Station
The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...
(ISS) constructed and operated by the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
National Aeronautics and Space Administration
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the United States's civil space program, aeronautics research and space research. Established in 1958, it su ...
(NASA),
European Space Agency
The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...
(ESA),
Canadian Space Agency
The Canadian Space Agency (CSA; ) is the national space agency of Canada, established in 1990 by the ''Canadian Space Agency Act''.
The President of the Canadian Space Agency, president is Lisa Campbell (civil servant), Lisa Campbell, who took ...
(CSA) and
Japan Aerospace Exploration Agency
The is the Japanese national Aeronautics, air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satell ...
(JAXA). The segment consists of eleven pressurized components and various external elements, almost all of which were delivered by the
Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
.
The segment is monitored and controlled from various mission control centers around the world including
Johnson Space Center
The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight in Houston, Texas (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight controller, flight control are conducted. ...
in
Houston
Houston ( ) is the List of cities in Texas by population, most populous city in the U.S. state of Texas and in the Southern United States. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, it is the county seat, seat of ...
, Texas,
Columbus Control Centre in
Oberpfaffenhofen, Germany and
Tsukuba Space Center
The Tsukuba Space Center (TKSC) also known by its radio Call sign, callsign Tsukuba, is the operations facility and headquarters for the Japan Aerospace Exploration Agency (JAXA) located in Tsukuba Science City in Ibaraki Prefecture. The facil ...
in
Tsukuba, Japan. However, it depends on the
Russian Orbital Segment
The Russian Orbital Segment (ROS) is the name given to the components of the International Space Station (ISS) constructed in Russia and operated by the Russian Roscosmos. The ROS handles Guidance, Navigation, and Control for the entire Station ...
for essential flight control,
orbital station-keeping and life support systems.
Modules

The US Orbital Segment consists of 10 pressurized modules. Of these, seven are habitable, and three are connecting nodes with large ports. The ports are used to connect the modules together or provide berths and docks for spacecraft.
Nodes
Each of the nodes has ports called
Common Berthing Mechanism
The Common Mechanism (CBM) connects habitable elements in the US Orbital Segment (USOS) of the International Space Station (ISS). The CBM has two distinct sides that, once mated, form a cylindrical wiktionary:vestibule, vestibule between modules ...
s (CBM). All three nodes have 4 ports around their exterior, and 1 port on each end, 6 ports in total. In addition to the 18 ports on the nodes there are additional ports on the modules, most of these are used for mating modules together, while unused CBM ports can berth one of the re-supply spacecraft MPLM, HTV, Dragon Cargo or Cygnus. There are two
PMA adapters that change CBM ports to
docking ports, the type used by Soyuz, Progress, Automated Transfer Vehicle, and the former Space Shuttle.
''Unity''
The first component of the USOS pressurized segment is the
''Unity''. On the aft end of ''Unity'' is the
Pressurized Mating Adapter (PMA) 1. The PMA-1 connects ''Unity'' with the
Russian segment. Unity is also connected to the ''Quest'' airlock on the starboard side, ''Tranquility'' on the port side, and the Z1 truss on the
zenith
The zenith (, ) is the imaginary point on the celestial sphere directly "above" a particular location. "Above" means in the vertical direction (Vertical and horizontal, plumb line) opposite to the gravity direction at that location (nadir). The z ...
. The ''Destiny'' lab connects to the forward end, leading to the rest of the USOS. ''Unity'' is also used by the crews on board the ISS to eat meals and share some downtime together. The ''Unity'' node was delivered to the station by
STS-88
STS-88 was the first Space Shuttle mission to the International Space Station (ISS). It was flown by Space Shuttle Space Shuttle Endeavour, ''Endeavour'', and took the first American module, the Unity (ISS module), ''Unity'' node, to the station ...
on December 6, 1998.
''Harmony''
The
''Harmony'' is the central connecting node of the USOS. ''Harmony'' connects to the ''Destiny'' lab aft end, ''Kibo'' lab to the port side, and ''Columbus'' lab to the starboard side. The ''Harmony'' node's nadir and zenith ports also serves as the berthing port for
H-II Transfer Vehicle (HTV),
Dragon
A dragon is a Magic (supernatural), magical legendary creature that appears in the folklore of multiple cultures worldwide. Beliefs about dragons vary considerably through regions, but European dragon, dragons in Western cultures since the Hi ...
and
Cygnus resupply vehicles. On the forward end of ''Harmony'' is PMA-2, which was used by visiting
Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
s as a mating adapter and by future crewed missions to the ISS. On July 18, 2016, aboard SpaceX CRS-9, NASA launched the International Docking Adapter-2, to convert the Shuttle
APAS-95 docking adapter to the
NASA Docking System
The NASA Docking System is NASA's implementation of the International Docking System Standard (IDSS), an international spacecraft docking standard promulgated by the International Space Station Multilateral Coordination Board. NDS is a Docking an ...
, to be used with
SpaceX Dragon 2
Dragon 2 is a class of partially reusable spacecraft developed, manufactured, and operated by the American space company SpaceX for flights to the International Space Station (ISS) and private spaceflight missions. The spacecraft, which consi ...
and
Boeing Starliner
The Boeing Starliner (or CST-100) is a spacecraft designed to transport crew to and from the International Space Station (ISS) and other low-Earth-orbit destinations. Developed by Boeing under NASA's Commercial Crew Program (CCP), it consists o ...
. ''Harmony'' was delivered by the
STS-120
STS-120 was a Space Shuttle mission to the International Space Station (ISS) that launched on October 23, 2007, from the Kennedy Space Center, Florida. The mission is also referred to as ISS-10A by the ISS program. STS-120 delivered the ''Harmony ...
mission on October 23, 2007.
''Tranquility''
The
''Tranquility node'' houses the USOS life support systems.
''Tranquility'' also hosts the seven windowed
''Cupola'' module and the ''Leonardo'' module on its forward port. The forward facing port of ''Tranquility'' is blocked by the station's truss structure, while the aft facing port is free for use. While the nadir port is used by the ''Cupola'', the zenith port is used by some exercise equipment inside the node. The starboard port is connected to node 1, and the port side is occupied by the PMA 3, previously a backup for the Shuttle docking, which will receive
International Docking Adapter-3 during CRS-18, to allow connection with the Crew Dragon and Boeing Starliner. The ''Tranquility'' module was delivered by
STS-130 in February 2010, together with the ''Cupola''.
Laboratories
''Destiny''
The
''Destiny laboratory'' is the American-built laboratory module. It is used for medical, engineering, biotechnological, physics, materials science and Earth science research. ''Destiny'' also houses a back-up robotic work station, and was the first of the USOS laboratories to be delivered. It was delivered by
STS-98 on February 7, 2001.
The ''Destiny'' lab is managed by mission control centers in
Houston, Texas
Houston ( ) is the List of cities in Texas by population, most populous city in the U.S. state of Texas and in the Southern United States. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, it is the county seat, seat of ...
and
Huntsville, Alabama
Huntsville is the List of municipalities in Alabama, most populous city in the U.S. state of Alabama. The population of the city is estimated to be 241,114 in 2024, making it the List of United States cities by population, 100th-most populous ...
.
''Columbus''
''Columbus'' is a laboratory module built by the
European Space Agency
The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...
.
It is host to scientific research in fluids, biology, medicine, materials and Earth sciences. ''Columbus'' also has four external payload locations, used to expose experiments to the vacuum of space. The ''Columbus'' module was delivered to the ISS by
STS-122 on February 7, 2008.
The
Columbus Control Center, located in
Germany
Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
, is responsible for the control of the ''Columbus'' module.
''Kibo''

The
''Kibo'' laboratory is the Japanese component of the USOS.
''Kibo'' has four main parts: the ''Kibo'' lab itself, a pressurized cargo container, an exposed science platform and two robotic arms. The module is unique in that it has a small airlock, which can be used to pass payloads to the robotic arms or astronauts outside the station. The robotic arms are controlled from a work station inside the lab. The lab is used for research in medicine, engineering, biotechnology, physics, materials science and Earth science. The logistics container was the first part of ''Kibo'' to arrive. It was delivered by
STS-123 in March 2008.
The ''Kibo'' lab itself was delivered to the ISS by the
STS-124 mission in May 2008.
The exposed facility was brought to the ISS by the
STS-127 mission in July 2009.
The JEM Mission Control Room in
Tsukuba, Japan is responsible for control of all elements of the ''Kibo'' laboratory.
Other modules
''Quest''

The
''Quest'' Joint Airlock is used to host spacewalks from the USOS segment of the ISS. It consists of two main parts: the equipment lock and the crew lock. The equipment lock is where the
Extravehicular Mobility Unit
The Extravehicular Mobility Unit (EMU) is an independent spacesuit that provides environmental protection, mobility, life support, and communications for astronauts performing extravehicular activity (EVA) in Geocentric orbit, Earth orbit. Introd ...
s are stored and preparations for spacewalks are carried out. The crew lock is depressurized during spacewalks. The ''Quest'' airlock was delivered and installed by the
STS-104 crew in July 2001.
''Leonardo''
The ''Leonardo'' module, also known as the
Permanent Multipurpose Module (PMM), is a module used for stowage space on the ISS. ''Leonardo'' is attached to the forward-facing side of the ''Tranquility'' node. The PMM was delivered to the ISS by the
STS-133 mission in early 2011. Originally the
Multi-Purpose Logistics Module
A Multi-Purpose Logistics Module (MPLM) is a large pressurized container that was used on Space Shuttle missions to transfer cargo to and from the International Space Station (ISS). Two MPLMs made a dozen trips in the Shuttle cargo bay and initi ...
(MPLM) ''Leonardo'', it was converted to stay on orbit for an extended period of time prior to being installed on the ISS.
''Cupola''
The
''Cupola'' is a seven-windowed module attached to the ''Tranquillity'' module. It is used for Earth observation and houses some gym equipment. All of the seven windows have covers that are closed when the windows aren't used, to protect the station from space debris impact. The ''Cupola'' was delivered together with the ''Tranquility'' node by
STS-130 in February 2010.
Bigelow Expandable Activity Module
Pressurized Mating Adapter
The
Pressurized Mating Adapters (PMA) serve as docking ports on the USOS portion of the ISS. It converts the standard
Common Berthing Mechanism
The Common Mechanism (CBM) connects habitable elements in the US Orbital Segment (USOS) of the International Space Station (ISS). The CBM has two distinct sides that, once mated, form a cylindrical wiktionary:vestibule, vestibule between modules ...
to
APAS-95, the docking system that was used by the
Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
and the
Russian Orbital Segment
The Russian Orbital Segment (ROS) is the name given to the components of the International Space Station (ISS) constructed in Russia and operated by the Russian Roscosmos. The ROS handles Guidance, Navigation, and Control for the entire Station ...
. Currently PMA-1 is used to connect the ''Unity'' node with the
''Zarya'' module on the ISS. Pressurized Mating Adapter-2 is located on the forward end of ''Harmony'', while PMA-3 is located in the zenith port of the same node. PMA-2 was the main Shuttle docking port, with PMA-3 being its backup, used only a few times.
With the new Crew Commercial Program and the retirement of the Shuttle fleet, NASA built the
International Docking Adapter, to convert PMA-2 and PMA-3 to the
NASA Docking System
The NASA Docking System is NASA's implementation of the International Docking System Standard (IDSS), an international spacecraft docking standard promulgated by the International Space Station Multilateral Coordination Board. NDS is a Docking an ...
. IDA-1 was supposed to dock with PMA-2, but was lost in the
SpaceX CRS-7 launch failure. Thus IDA-2, which was brought by
SpaceX CRS-9 and was supposed to dock to PMA-3, was shifted to PMA-2. IDA-3, the replacement for the lost IDA-1, was launched in July 2019 on
SpaceX CRS-18 and was berthed to PMA-3.
PMA-1 and PMA-2 were delivered with the ''Unity'' node on STS-88 in December 1998.
The third PMA was delivered by
STS-92 on October 11, 2000.
External elements
Integrated Truss Structure
The
Integrated Truss Structure
The Integrated Truss Structure (ITS) of the International Space Station (ISS) consists of a linear arranged sequence of connected trusses on which various unpressurized components are mounted such as logistics carriers, radiators, ISS Solar Arra ...
(ITS) houses vital equipment on the exterior of the ISS.
Each segment of truss is given a designation of P or S, indicating whether the segment is on the port or starboard side, and a number which indicates its position on its respective side. The truss system itself consists of 12 total segments—four on each side, and one central segment—which are connected to the ISS by attachment points on the ''Destiny'' module.
The thirteenth piece, known as the Zenith-1 (Z1) truss segment, is attached to the ''Unity'' module, and was originally used to hold the P6
solar arrays to provide power to the USOS. The Z1 segment now houses the
Ku-band antennas and serves as a routing point for power and data cables on the exterior of the ISS. The Integrated Truss Structure is made from
stainless steel
Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromi ...
,
titanium
Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
and
aluminum
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
. It spans approximately 110 meters long and houses four sets of solar arrays. Each set of solar arrays contains four arrays for a total of 16 solar arrays. Each of the four sets of arrays also has an associated cooling system and radiator for cooling the power supply equipment. The Integrated Truss Structure also houses the main cooling system for the ISS, which consists of two pumps, two radiator arrays, and two ammonia and two nitrogen tank assemblies. There are also several payload attachment points located on the Integrated Truss Structure. These points host the
External Stowage Platform
External stowage platforms (ESPs) are key components of the International Space Station (ISS). Each platform is made from steel and serves as an external pallet that can hold spare parts, also known as orbital replacement units (ORUs), for the spa ...
s, External Logistics Carriers,
Alpha Magnetic Spectrometer and the Mobile Base System for the
Canadarm2. The Z1 truss was delivered by the
STS-92 mission in October 2000.
The P6 segment was installed on
STS-97 in December 2000.
The S0 truss was delivered to the ISS on
STS-110
STS-110 was a Space Shuttle mission to the International Space Station (ISS) on 8–19 April 2002 flown by Space Shuttle ''Atlantis''. The main purpose was to install the S0 Truss segment, which forms the backbone of the truss structure on the ...
,
with the S1 segment following on
STS-112
STS-112 (ISS assembly sequence, ISS assembly flight 9A) was an 11-day Space Shuttle mission to the International Space Station (ISS) flown by . Space Shuttle ''Atlantis'' was launched on 7 October 2002 at 19:45 UTC from the Kennedy Space Center's ...
.
The P1 segment of the truss was brought to the ISS by
STS-113
STS-113 was a Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle ''Space Shuttle Endeavour, Endeavour''. During the 14-day mission in late 2002, ''Endeavour'' and its crew extended the ISS backbone with the Int ...
,
followed by the P3/P4 segment on
STS-115,
and the P5 segment on
STS-116
STS-116 (also known as ISS-12A) was a Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle Discovery, Space Shuttle '' Discovery''. ''Discovery'' lifted off on December 9, 2006 for her 33rd flight at 20:47:35 Easte ...
.
The S3/S4 truss segment was delivered by
STS-117
STS-117 (ISS assembly sequence, ISS assembly flight 13A) was a Space Shuttle mission flown by Space Shuttle Atlantis, Space Shuttle ''Atlantis'', launched from Kennedy Space Center Launch Complex 39, pad 39A of the Kennedy Space Center on June ...
,
followed by the S5 segment
STS-118
STS-118 was a Space Shuttle mission to the International Space Station (ISS) flown by the orbiter ''Space Shuttle Endeavour, Endeavour''. STS-118 lifted off on August 8, 2007, from Kennedy Space Center Launch Complex 39, launch pad 39A at Kennedy ...
.
The last component of the truss segment, the S6 segment, was delivered by
STS-119.
External Stowage Platform
The
External Stowage Platform
External stowage platforms (ESPs) are key components of the International Space Station (ISS). Each platform is made from steel and serves as an external pallet that can hold spare parts, also known as orbital replacement units (ORUs), for the spa ...
s (ESP), are a series of platforms that are used to store
Orbital Replacement Units (ORU) on the ISS. The ESP's provide power to the ORU's but do not allow command and data handling. External Stowage Platform 1 is located on the port side of the ''Destiny'' lab and was delivered on the
STS-102 mission in March 2001.
ESP-2 is located on the port side of the ''Quest'' airlock, and was brought to the ISS by the
STS-114 crew in 2005.
ESP-3 is located on the Starboard 3 (S3) truss segment and was delivered to the ISS on the
STS-118
STS-118 was a Space Shuttle mission to the International Space Station (ISS) flown by the orbiter ''Space Shuttle Endeavour, Endeavour''. STS-118 lifted off on August 8, 2007, from Kennedy Space Center Launch Complex 39, launch pad 39A at Kennedy ...
mission in August 2007.
ExPRESS logistics carrier

The
ExPRESS logistics carriers (ELCs) are similar to the External Stowage Platform, but designed to carry more cargo. Unlike the ESPs, the ELCs allow for command and data handling. They utilize a steel grid structure where external mounted containers, payloads and gyroscopes are mounted; and science experiments can be fitted. Some ELC components have been built by the
Brazilian Space Agency. ExPRESS Logistics Carriers 1, located on the lower P3 truss, and ELC 2, located on the upper S3 truss, were delivered by the
STS-129 mission in November 2009.
ELC-3 was brought to the ISS by the
STS-134
STS-134 (ISS assembly sequence, ISS assembly flight ULF6) was the penultimate mission of NASA's Space Shuttle program and the 25th and last spaceflight of . This flight delivered the Alpha Magnetic Spectrometer and an ExPRESS Logistics Carrier ...
crew, is located on the upper P3 truss.
ELC-4 was delivered and installed on the lower S3 truss segment, during the
STS-133 mission.
Alpha Magnetic Spectrometer 2
The
Alpha Magnetic Spectrometer (AMS) is a particle physics experiment that is mounted on the S3 truss segment. The AMS is designed to search for
dark matter
In astronomy, dark matter is an invisible and hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravity, gravitational effects that cannot be explained by general relat ...
and
anti-matter. Five hundred scientists from 56 different institutions and 16 countries participated in the development and construction of the AMS. The Alpha Magnetic Spectrometer was delivered by the STS-134 crew.
Mobile Servicing System
The components of the MSS were supplied by the
Canadian Space Agency
The Canadian Space Agency (CSA; ) is the national space agency of Canada, established in 1990 by the ''Canadian Space Agency Act''.
The President of the Canadian Space Agency, president is Lisa Campbell (civil servant), Lisa Campbell, who took ...
in conjunction with
MDA Space Missions. The Mobile Transporter that carries the Mobile Base System was designed and built by Northrop Grumman under contract with NASA.
Canadarm2
The main component of the mobile servicing system is the
Canadarm2, also known as the Space Station Remote Manipulator System (SSRMS). The arm is capable of moving large, heavy payloads that cannot be handled by astronauts during a spacewalk. The arm has a payload capacity of , and 7 degrees of freedom.
Canadarm2 is also capable of changing where it is stationed and what end is used. There are
grapple fixtures for the Candarm2 on the ''Destiny'' lab, ''Harmony'' node, ''Unity'' node and the Mobile Base System. A grapple fixture is installed on the
''Zarya'' module, but does not have data cables connected. Once these cables are connected, the Canadarm2 will be able to position itself on the exterior of ''Zarya'' and will be able to support
Extra-vehicular Activity (EVA) in the vicinity the Russian Orbital Segment (ROS). The Canadarm2 was assembled and installed by the
STS-100 crew in early 2001.
Special Purpose Dextrous Manipulator
The
Special Purpose Dexterous Manipulator (SPDM), also known as Dextre, is a two armed robot that can be attached to the ISS, the Mobile Base System or Canadarm2. Dextre is capable of performing tasks that would otherwise require an astronaut to perform. These tasks include switching
orbital replacement units or moving ORUs from their stowage locations to where they are to be installed. Using Dextre can reduce preparatory time needed to perform certain tasks and afford astronauts the ability to invest more time in the completion of other tasks. Dextre's primary grapple fixture is located on the ''Destiny'' lab, but can also be mounted on any powered grapple fixture on the ISS. It has a payload capacity of , and 15 degrees of freedom.
Dextre was delivered to the ISS by
STS-123.
Mobile Base System
The
Mobile Base System (MBS) is a rail car-like device installed on the Integrated Truss Structure of the ISS. It weighs , and has a payload capacity of .
The MBS can move from the Starboard 3 (S3) to the Port 3 (P3) truss segments and has a top speed of . The MBS has four
PDGFs which can be used as mounts for the
Canadarm2 and
Dextre, as well as a Payload/Orbital Replacement Unit Accommodations (POA), to hold payloads and
Orbital Replacement Units (ORUs). The MBS also has a common attach system, to grapple a special capture bar on payloads. It also has its own main computer and video distribution units, and remote power control modules.
The MBS was delivered on
STS-111 in June 2002.
Enhanced ISS Boom Assembly
The
Enhanced ISS Boom Assembly is used to extend the reach of Canadarm2 and provides detailed inspection capability. There are lasers and cameras at the end of the boom able to record at a resolution of a few millimeters. The boom is also fitted with handrails, so that it can assist spacewalkers during EVAs as was done on STS-120 to repair the solar arrays.
Proposed modules
Axiom PPTM
On January 27, 2020, NASA announced that it had given permission to
Axiom Space to launch up to three modules to attach to the International Space Station. , Axiom Space expects to launch one module to the ISS, where it will dock at one of two ports currently used by cargo spacecraft. This module, the Payload Power Thermal Module (PPTM), will include power and thermal systems as well as multiple racks for research payloads.
PPTM is expected to be launched no earlier than 2027 and remain at the ISS until the launch of Axiom's Habitat One (Hab-1) module no earlier than 2028, after which it will undock from the ISS to join with Hab-1.
Cancelled modules
There are various proposed modules to extend the US Orbital Segment.
Habitation Extension Modules
The Habitation Extension Modules (HEM) refer to proposed
British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies.
* British national identity, the characteristics of British people and culture ...
-built modules designed to connect to ''
Tranquility
Tranquillity (also spelled tranquility) is the quality or state of being tranquil; that is, calm, serene, and worry-free. The word tranquillity appears in numerous texts ranging from the religious writings of Buddhism—where the term refers to ...
'' module of the
International Space Station
The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...
. They were conceived by a consortium of engineers and scientists led by
Mark Hempsell, aeronautical engineer at the
University of Bristol
The University of Bristol is a public university, public research university in Bristol, England. It received its royal charter in 1909, although it can trace its roots to a Merchant Venturers' school founded in 1595 and University College, Br ...
. The proposal has no formal support of the British government, . If funded, the modules were intended to be launched sometime in 2011.
Node 4

Node 4, also known as the Docking Hub System (DHS), was a proposed module that would have been built using the Node Structural Test Article (STA) and docked to the forward port of the
Harmony module
''Harmony'', also known as ''Node 2'', is the "utility hub" of the International Space Station. It connects the laboratory modules of the United States, Europe and Japan, as well as providing electrical power and electronic data. Sleeping cabi ...
. The Structural Test Article was built to facilitate testing of ISS hardware and was intended to become Node 1. However, during construction, structural design flaws were discovered. The under-construction Node 2 was renamed Node 1 and the STA (ex-Node 1) was put into storage at the Kennedy Space Center (KSC).
In 2011,
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
was considering a 40-month design and development effort for Node 4 that would result in its launch in late 2013.
Since the
Space Shuttle program
The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its ...
was retired, had a decision to build and launch Node 4 been taken, it would have been launched by an
Atlas V
Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to ...
or
Delta IV Heavy launch vehicle.
Centrifuge demonstration
In order to assess and characterize influences and effects of the centrifuge relative to human reactions, mechanical dynamic responses and influences, the demonstration of Nautilus-X centrifuge would be tested on the ISS.
If produced, this centrifuge would have been the first in-space demonstration of sufficient scale for
artificial partial-G effects.
The demonstrator would be sent using a single
Delta IV Heavy or
Atlas V
Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to ...
launch vehicle. The full cost of such a demonstrator would be between US$83 million and US$143 million.
XBASE
In August 2016,
Bigelow Aerospace negotiated an agreement with NASA to develop a full-sized ground prototype Deep Space Habitation based on the B330 under the second phase of
Next Space Technologies for Exploration Partnerships. The module is called the Expandable Bigelow Advanced Station Enhancement (XBASE), as Bigelow hopes to test the module by attaching it to the International Space Station.
Operation
Operational control of the US Orbital Segment of the ISS is accomplished by NASA and the ESA, the agency that manages the civilian portion of the
US government
The Federal Government of the United States of America (U.S. federal government or U.S. government) is the national government of the United States.
The U.S. federal government is composed of three distinct branches: legislative, execut ...
space program.
In the early years of the ISS operation beginning in 2000,
a lot of the work in the US Orbital Segment was performed by NASA astronauts—although some NASA-trained astronauts were employees of non-US government space agencies—and all cargo and crew transport to the space station was handled by NASA-owned spacecraft, specifically, by the
Space Shuttle
The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
. Beginning in the late 2000s, NASA began to contract for commercial services to
transport cargo to the space station
["NASA Awards Space Station Commercial Resupply Services Contracts"]
. NASA, 23 December 2008. with services beginning in 2012.
By 2020, operational commercial flights were handling ISS USOS
crew transport as well.
In 2010, NASA began to open up a limited amount of its space and astronaut time on the US Orbital Segment to commercial use. In 2005, the US Congress authorized that one of the several
U.S. National Laboratories should exist on board the ISS, and commercial research could be done there. The
Center for the Advancement of Science in Space (CASIS) was set up to operate the lab. In September 2009,
Nanoracks signed the
first contract with NASA to utilize the on-orbit lab space, and had their first laboratory on the Space Station in April 2010.
Other companies followed, however the commercial space and commercial experiments on the ISS have always been limited, with most orbital segment space and experiments reserved for direct use by NASA, the ESA and JAXA.
Prices to be paid by commercial companies utilizing the ISS National Lab on USOS were heavily subsidized from 2010 until early 2021. Beginning in March 2021, the subsidy was removed, and prices raised by NASA to approximate "full reimbursement for the value of NASA resources."
NASA published a "Commercial and Marketing Pricing Policy" beginning in 2019.
The historical prices and ~2021 prices on offer for services in the USOS are:
See also
*
NASA X-38, canceled crew return vehicle
*
NASA HL-20/
Dream Chaser proposed crew return vehicle
*
Russian Orbital Segment
The Russian Orbital Segment (ROS) is the name given to the components of the International Space Station (ISS) constructed in Russia and operated by the Russian Roscosmos. The ROS handles Guidance, Navigation, and Control for the entire Station ...
References
External links
Orbital Sciences spaceplane concept
{{Japanese space program
Components of the International Space Station