Assembly of the International Space Station

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Animation of the assembly of the International Space Station

The process of assembling the International Space Station (ISS) has been under way since the 1990s. Zarya, the first ISS module, was launched by a Proton rocket on 20 November 1998. The STS-88 Space Shuttle mission followed two weeks after Zarya was launched, bringing Unity, the first of three node modules, and connecting it to Zarya. This bare 2-module core of the ISS remained uncrewed for the next one and a half years, until in July 2000 the Russian module Zvezda was launched by a Proton rocket, allowing a maximum crew of two astronauts or cosmonauts to be on the ISS permanently.

The ISS has a pressurized volume of approximately 1,000 cubic metres (35,000 cu ft), a mass of approximately 420,000 kilograms (930,000 lb), approximately 100 kilowatts of power output, a truss 108.4 metres (356 ft) long, modules 74 metres (243 ft) long, and a crew of seven.[1] Building the complete station required more than 40 assembly flights. As of 2020, 36 Space Shuttle flights delivered ISS elements. Other assembly flights consisted of modules lifted by the Falcon 9, Russian Proton rocket or, in the case of Pirs and Poisk, the Soyuz-U rocket.

Some of the larger modules include:


International Space Station mockup at Johnson Space Center in Houston, Texas.

The space station is located in orbit around the Earth at an altitude of approximately 410 km (250 mi), a type of orbit usually termed low Earth orbit (the actual height varies over time by several kilometers due to atmospheric drag and reboosts). It orbits Earth in a period of about 90 minutes; by August 2007 it had completed more than 50,000 orbits since launch of Zarya on 20 November 1998.

A total of 14 main pressurized modules were scheduled to be part of the ISS by its completion date in 2010.[2] A number of smaller pressurized sections will be adjunct to them (Soyuz spacecraft (permanently 2 as lifeboats – 6 months rotations), Progress transporters (2 or more), the Quest and Pirs airlocks, as well as periodically the H-II Transfer Vehicle).

The US Orbital Segment was completed in 2011 after the installation of the Alpha Magnetic Spectrometer during the STS-134 mission. The Russian Orbital Segment assembly has been on an indefinite hiatus since the installation of the Rassvet module in 2010 during the STS-132 mission. The Rassvet module on the ISS right now was originally supposed to be the on-ground dynamic testing mock-up of the now-cancelled Science Power Platform. There is no dedicated science laboratory module on the Russian Orbital Segment as of 2020. The Nauka science laboratory module was originally supposed to be delivered to the ISS in 2007 but cost overruns and quality control problems have delayed it for over a decade. The current plan is for Nauka to be delivered in mid-2021 followed by the nodal module Prichal to be delivered in the third quarter of 2021. Nauka will have new crew quarters, life support equipment that can produce oxygen and water, and a new galley. There are plans to add 2 or 3 more modules that would attach to Prichal during the mid-2020s. Adding more Russian modules in 2021-25 will help the Zvezda module greatly because Zvezda's originally installed central command computers no longer work (three ThinkPad laptops are now the Zvezda's central command computers) and its Elektron oxygen generators are not replaceable and are way past their expiration date. In Russian modules all the hardware is launched with the equipment permanently installed. It is impossible to replace hardware like in the US Orbital Segment with its very wide 51 inch (105 cm) hatch openings between modules. This potential problem with the Zvezda was made apparent when in October 2020 the toilet, oven, and Elektron all malfunctioned at the same time and the cosmonauts onboard had to make emergency repairs.[3]

The ISS, when completed, will consist of a set of communicating pressurized modules connected to a truss, on which four large pairs of photovoltaic modules (solar panels) are attached. The pressurized modules and the truss are perpendicular: the truss spanning from starboard to port and the habitable zone extending on the aft-forward axis. Although during the construction the station attitude may vary, when all four photovoltaic modules are in their definitive position the aft-forward axis will be parallel to the velocity vector.[4]

In addition to the assembly and utilization flights, approximately 30 Progress spacecraft flights are required to provide logistics until 2010. Experimental equipment, fuel and consumables are and will be delivered by all vehicles visiting the ISS: the SpaceX Dragon, the Russian Progress, the European ATV and the Japanese HTV, and space station downmass will be carried back to Earth facilities on the Dragon.[5]

Columbia disaster and changes in construction plans[edit]

Columbia lifting off on its final mission.

Disaster and consequences[edit]

10 March 2001 – The Leonardo Multi-Purpose Logistics Module rests in Space Shuttle Discovery's payload bay during STS-102.

After the Space Shuttle Columbia disaster on 1 February 2003, there was some uncertainty over the future of the ISS. The subsequent two and a half-year suspension of the U.S. Space Shuttle program, followed by problems with resuming flight operations in 2005, were major obstacles.[citation needed]

The Space Shuttle program resumed flight on 26 July 2005, with the STS-114 mission of Discovery. This mission to the ISS was intended both to test new safety measures implemented since the Columbia disaster and deliver supplies to the station. Although the mission succeeded safely, it was not without risk; foam was shed by the external tank, leading NASA to announce future missions would be grounded until this issue was resolved.[citation needed]

Between the Columbia disaster and the resumption of Shuttle launches, crew exchanges were carried out solely using the Russian Soyuz spacecraft. Starting with Expedition 7, two-astronaut caretaker crews were launched in contrast to the previously launched crews of three. Because the ISS had not been visited by a shuttle for an extended period, a larger than planned amount of waste accumulated, temporarily hindering station operations in 2004. However Progress transports and the STS-114 shuttle flight took care of this problem.[citation needed]

Changes in construction plans[edit]

Construction of the International Space Station over New Zealand.

Many changes were made to the originally planned ISS, even before the Columbia disaster. Modules and other structures were cancelled or replaced, and the number of Shuttle flights to the ISS was reduced from previously planned numbers. However, more than 80% of the hardware intended to be part of the ISS in the late 1990s was orbited and is now part of the ISS's configuration.[citation needed]

During the shuttle stand-down, construction of the ISS was halted and the science conducted aboard was limited due to the crew size of two, adding to earlier delays due to Shuttle problems and the Russian space agency's budget constraints.[citation needed]

In March 2006, a meeting of the heads of the five participating space agencies accepted the new ISS construction schedule that planned to complete the ISS by 2010.[6]

As of May 2009, a crew of six has been established following 12 Shuttle construction flights after the second "Return to Flight" mission STS-121. Requirements for stepping up the crew size included enhanced environmental support on the ISS, a second Soyuz permanently docked on the station to function as a second 'lifeboat', more frequent Progress flights to provide double the amount of consumables, more fuel for orbit raising maneuvers, and a sufficient supply line of experimental equipment.[citation needed] As of November 2020, the crew capacity has increased to seven due to the launch of Crew Dragon by SpaceX, which can carry 4 astronauts to the ISS.

Later additions included the Bigelow Expandable Activity Module (BEAM) in 2016, and numerous Russian components are planned as part of the in-orbit construction of OPSEK.[citation needed]

Assembly sequence[edit]

ISS elements

The ISS is made up of 16 pressurized modules: four Russian modules (Pirs, Zvezda, Poisk and Rassvet), nine US modules (Zarya,[7] BEAM,[8] Leonardo, Harmony, Quest, Tranquility, Unity, Cupola, and Destiny), two Japanese modules (the JEM-ELM-PS and JEM-PM) and one European module (Columbus).

At least three more Russian pressurized modules are scheduled to be added to the station.[9] Nauka will become the primary laboratory module on the Russian segment,[10] Prichal is a spherical docking node featuring six docking ports, and the third new Russian module is the Science-Power Module-1 – also known as SPM-1 or NEM-1.

Although not permanently docked with the ISS, Multi-Purpose Logistics Modules (MPLMs) formed part of the ISS during some Shuttle missions. An MPLM was attached to Harmony (initially to Unity) and was used for resupply and logistics flights.[citation needed]

Spacecraft attached to the ISS also extend the pressurized volume. At least one Soyuz spacecraft is always docked as a 'lifeboat' and is replaced every six months by a new Soyuz as part of crew rotation. Table below shows the sequence in which these components were added to the ISS.[11]

Element Assembly
Length Diameter Mass Isolated View Station View
Zarya (FGB) 1A/R 1998-11-20 Proton-K 12.56 m (41.2 ft) 4.1 m (13 ft) 24,968 kg (55,045 lb) Zarya from STS-88.jpg Zarya from STS-88.jpg
Unity (Node 1) 2A 1998-12-04 Space Shuttle Endeavour (STS-88) 5.5 m (18 ft) 4.3 m (14 ft) 11,895 kg (26,224 lb) ISS Unity module.jpg Sts088-703-019e.jpg
PMA-1 1.86 m (6 ft 1 in) 1.9 m (6 ft 3 in) 1,589 kg (3,503 lb) PMA-3 arrives in SSPF.jpg
PMA-2 1.86 m (6 ft 1 in) 1.9 m (6 ft 3 in) 1,376 kg (3,034 lb) PMA-3 arrives in SSPF.jpg
Zvezda (Service Module) 1R 2000-07-12 Proton-K 13.1 m (43 ft) 4.2 m (14 ft) 24,604 kg (54,243 lb) View of the bottom of Zvezda.jpg Unity-Zarya-Zvezda STS-106.jpg
Z1 Truss 3A 2000-10-11 Space Shuttle Discovery (STS-92) ISS Unity and Z1 truss structure from STS-92.jpg S97e5009.jpg
PMA-3 1.86 m (6 ft 1 in) 1.9 m (6 ft 3 in) 1,183 kg (2,608 lb) PMA-3 arrives in SSPF.jpg
P6 Truss & Solar Arrays 4A 2000-11-30 Space Shuttle Endeavour (STS-97) STS-97 ISS.jpg STS-97 ISS.jpg
Destiny (US Laboratory) 5A 2001-02-07 Space Shuttle Atlantis (STS-98) 9.2 m (30 ft) 4.3 m (14 ft) 14,515 kg (32,000 lb) ISS Destiny Lab.jpg Sts098-312-0020.jpg
ESP-1 5A.1 2001-03-08 Space Shuttle Discovery (STS-102) STS-102 External Storage Platform 1 crop.jpg S102e5350.jpg
Canadarm2 (SSRMS) 6A 2001-04-19 Space Shuttle Endeavour (STS-100) STS-114 Steve Robinson on Canadarm2.jpg S100e5958 cropped.jpg
Quest (Joint Airlock) 7A 2001-07-12 Space Shuttle Atlantis (STS-104) 5.5 m (18 ft) 4.0 m (13.1 ft) 9,923 kg (21,876 lb) ISS Quest airlock.jpg ISS on 20 August 2001.jpg
Pirs (Docking Compartment) 4R 2001-09-14 Soyuz-U
(Progress M-SO1)
4.9 m (16 ft) 2.55 m (8.4 ft) 3,838 kg (8,461 lb) Pirs docking module taken by STS-108.jpg S108e5628.jpg
S0 Truss[12] 8A 2002-04-08 Space Shuttle Atlantis (STS-110) S0 Truss lifted from Shuttles cargo bay.jpg International Space Station.jpg
Mobile Base System UF2 2002-06-05 Space Shuttle Endeavour (STS-111) STS-111 Installation of Mobile Base System.jpg Sts111-711-005.jpg
S1 Truss 9A 2002-10-07 Space Shuttle Atlantis (STS-112) ISS S1 Truss.jpg S112e05823.jpg
P1 Truss 11A 2002-11-23 Space Shuttle Endeavour (STS-113) ISS Truss structure.jpg ISS Mission STS-113.jpg
ESP-2 LF1 2005-07-26 Space Shuttle Discovery (STS-114) STS-114 External Storage Platform 2 crop.jpg ISS Aug2005.jpg
P3/P4 Truss & Solar Arrays[13] 12A 2006-09-09 Space Shuttle Atlantis (STS-115) STS-115 EVA 2 on Day 5.jpg STS-115 ISS after undocking.jpg
P5 Truss[14] 12A.1 2006-12-09 Space Shuttle Discovery (STS-116) STS-116 - ISS P5 Truss awaits installation (NASA ISS014-E-09479).jpg ISS after STS-116 in December 2006.jpg
S3/S4 Truss & Solar Arrays 13A 2007-06-08 Space Shuttle Atlantis (STS-117) S3-S4 Truss Installed 2.jpg ISS after STS-117 in June 2007.jpg
S5 Truss 13A.1 2007-08-08 Space Shuttle Endeavour (STS-118) STS-116 - P5 Truss hand-off to ISS (NASA S116-E-05765).jpg ISS after STS-118 in August 2007.jpg
ESP-3 STS-118 ESP-3 on RMS.jpg
Harmony (Node 2) 10A 2007-10-23 Space Shuttle Discovery (STS-120) Harmony Relocation.jpg ISS after STS-120 in November 2007.jpg
Relocation of
P6 Truss
S6 Truss Transfer (STS-119).jpg
Columbus (European Laboratory)[15] 1E 2008-02-07 Space Shuttle Atlantis (STS-122) Columbus module - cropped.jpg STS-122 ISS Flyaround.jpg
Dextre (SPDM) 1J/A 2008-03-11 Space Shuttle Endeavour (STS-123) S123 Dextre01.jpg STS-123 ISS Flyaround cropped.jpg
Experiment Logistics Module (ELM) Kibo ELM-PS on ISS.jpg
JEM Pressurized Module (JEM-PM)[16][17] 1J 2008-05-31 Space Shuttle Discovery (STS-124) STS-124 Kibo.jpg ISS after STS-124 06 2008.jpg
JEM Remote Manipulator System (JEMRMS)
S6 Truss & Solar Arrays 15A 2009-03-15 Space Shuttle Discovery (STS-119) S6 Truss Transfer (STS-119).jpg ISS March 2009.jpg
Kibo Exposed Facility (JEM-EF) 2J/A 2009-07-15 Space Shuttle Endeavour (STS-127) STS-127 JEM-EF.jpg ISS & Endeavour Shadow STS-127 2.jpg
Poisk (MRM-2)[18][19] 5R 2009-11-10 Soyuz-U
(Progress M-MIM2)
Poisk.Jpeg STS-129 Atlantis approaches below the ISS.jpg
ELC-1 ULF3 2009-11-16 Space Shuttle Atlantis (STS-129) ELC2 STS 129.JPG ISS ULF3 STS-129.jpg
Tranquility (Node 3) 20A 2010-02-08 Space Shuttle Endeavour (STS-130) Tranquility-node3.JPG ISSpoststs130.jpg
Cupola Exterior of Cupola - Exp28.jpg
Rassvet (MRM-1)[20] ULF4 2010-05-14 Space Shuttle Atlantis (STS-132) STS-132 ISS-23 Rassvet Pirs and Progress M-05M.jpg International Space Station after undocking of STS-132.jpg
Leonardo (PMM) ULF5 2011-02-24 Space Shuttle Discovery (STS-133) STS-133 ISS-26 Permanent Multipurpose Module.jpg STS-133 International Space Station after undocking.jpg
AMS-02 ULF6 2011-05-16 Space Shuttle Endeavour (STS-134) Alpha Magnetic Spectrometer - 02.jpg STS-134 International Space Station after undocking.jpg
OBSS STS-120 OBSS repair.jpg
HRSGF CRS SpX-2 2013-3-13 Falcon 9 (SpaceX CRS-2)
BEAM[21] CRS SpX-8 2016-04-08 Falcon 9 (SpaceX CRS-8) Beam-instalation-space-station.jpg ISS-56 International Space Station fly-around (04).jpg
IDA-2[22][23] CRS SpX-9 2016-07-18 Falcon 9 (SpaceX CRS-9) IDA-2 upright.jpg
IDA-3[24] CRS SpX-18 2019-07-25 Falcon 9 (SpaceX CRS-18)
Bartolomeo [25] CRS SpX-20 2020-03-06 Falcon 9 (SpaceX CRS-20).
Nanoracks Bishop Airlock CRS SpX-21 2020-12-06 Falcon 9 (SpaceX CRS-21) Nanoracks airlock in SSPF.jpg

Future elements[edit]

  • In January of 2021, NASA announced plans to upgrade the station's solar arrays by installing new arrays on top of six of the station's eight existing arrays.[26]
  • Axiom Space plans on launching several modules to connect where PMA-2 is currently at as part of the commercial Axiom Station project. At the end of the ISS's life, Axiom Station could be detached from the ISS and continue in orbit as a commercial low orbit platform.[27]
  • Science and Power Module, (NEM). Future Russian component of the ISS. It will provide Russian segment with additional living quarters, laboratory facilities and solar arrays as well as a new flight control system.[28] It successfully underwent pressure tests in November 2018 and was planned to be delivered to orbit in 2021[29]

Cancelled modules[edit]

Diagram of the planned ISS circa 1999

Unused modules[edit]

The following modules were built, but have not been used in future plans for the ISS as of January 2021.

  • American Node 4 – Also known as the Docking Hub System (DHS),[31] would allow the station to have more docking ports for visiting vehicles and would allow inflatable habitats and technology demonstrations to be tested as part of the station.[32]


The ISS is credited as the most expensive item ever built, costing around $150 billion (USD),[33] making it more expensive than Skylab (costing US$2.2 billion) [34] and Mir (US$4.2 billion).[35]

See also[edit]


  1. ^ . Retrieved 27 November 2020
  2. ^ "Consolidated Launch Manifest". NASA. Archived from the original on 7 July 2006. Retrieved 15 July 2006.
  3. ^ . Retrieved 15 December 2020
  4. ^ "What are the ISS attitudes?" (Flash). NASA. Archived from the original on 2 September 2006. Retrieved 11 September 2006.
  5. ^ Black, Charles (24 December 2012). "When Dragon made commercial spaceflight a reality". SEN. Retrieved 26 December 2012. [Dragon's] ability to return goods is currently unique because all the other regular supply ships – Europe's Automated Transfer Vehicle (ATV), Japan's HTV (or "Kounotori") and Russia's Progress – all burn up during controlled re-entry.
  6. ^ Coppinger, Rob (3 March 2006). "NASA commits to Shuttle missions to International Space Station". FlightGlobal. Retrieved 16 September 2006.
  7. ^ . Retrieved 3 March 2019.
  8. ^ . Retrieved 27 November 2017.
  9. ^ "Russia pressing forward on ISS expansion". nasaspaceflight. July 2019. Retrieved 28 August 2020.
  10. ^ "Russia's Nauka ISS module arrives at Baikonur for final launch preparations". nasaspaceflight. August 2020. Retrieved 28 August 2020.
  11. ^ "Reference Guide to the International Space Station" (PDF). NASA. September 2015. Retrieved 8 June 2019.
  12. ^ "Space Station Assembly: Integrated Truss Structure". NASA. Archived from the original on 7 December 2007. Retrieved 2 December 2007.
  13. ^ "P3 and P4 to expand station capabilities, providing a third and fourth solar array" (PDF). Boeing. July 2006. Retrieved 2 December 2007.
  14. ^ "STS-118 MISSION OVERVIEW: BUILD THE STATION…BUILD THE FUTURE" (PDF). NASA PAO. July 2007. Archived (PDF) from the original on 1 December 2007. Retrieved 2 December 2007.
  15. ^ "Columbus laboratory". ESA. 10 January 2009. Archived from the original on 30 March 2009. Retrieved 6 March 2009.
  16. ^ "About Kibo". JAXA. 25 September 2008. Archived from the original on 10 March 2009. Retrieved 6 March 2009.
  17. ^ "Kibo Japanese Experiment Module". NASA. 23 November 2007. Archived from the original on 23 October 2008. Retrieved 22 November 2008.
  18. ^ Zak, Anatoly. "Docking Compartment-1 and 2". Archived from the original on 10 February 2009. Retrieved 26 March 2009.
  19. ^ Bergin, Chris (9 November 2009). "Russian module launches via Soyuz for Thursday ISS docking". Archived from the original on 13 November 2009. Retrieved 10 November 2009.
  20. ^ "NASA Extends Contract With Russia's Federal Space Agency" (Press release). NASA. 9 April 2007. Archived from the original on 23 June 2007. Retrieved 15 June 2007.
  21. ^ "NASA to Test Bigelow Expandable Module on Space Station". NASA. 16 January 2013. Retrieved 16 January 2013.
  22. ^ Jason Rhian (18 July 2016). "SpaceX Conducts Second Ground Landing After Launch Of CRS-9 Dragon To ISS". Spaceflight Insider.
  23. ^ Harwood, William (19 August 2016). "Spacewalkers attach docking adapter to space station for commercial vehicles". Spaceflight. Retrieved 20 August 2016.
  24. ^
  25. ^ "Successful launch for Airbus' Bartolomeo". Airbus (Press release). 9 March 2020. Retrieved 4 January 2021.
  26. ^ NASA to upgrade space station solar arrays
  27. ^
  28. ^ "Science and Power Module, NEM".
  29. ^ "Scientific power module for ISS has been successfully tested for strength (In Russian)". 3DNews.
  30. ^ Nautilus-X-Holderman_1-26-11
  31. ^ ISS Managers review long-term configuration of International Space Station |
  32. ^ Test article could facilitate space station applications – 31 August 2010
  33. ^ "Is The International Space Station The Most Expensive Single Item Ever Built?". Science 2.0. 27 August 2014. Retrieved 3 May 2018.
  34. ^ "The Space Review: Costs of US piloted programs". Retrieved 3 May 2018.
  35. ^ Tyler, Patrick E. (24 March 2001). "Russians Find Pride, and Regret, in Mir's Splashdown". The New York Times. ISSN 0362-4331. Retrieved 3 May 2018.

External links[edit]

Media articles