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The International Space Station as seen from the approaching Space Shuttle Endeavour on STS-126. | ||
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ISS Insignia | ||
Station statistics | ||
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NSSDC ID: | 1998-067A | |
Call sign: | Alpha (only by NASA) | |
Crew: | 3 | |
Launch: | 1998–2011 | |
Launch pad: | KSC LC-39, Baikonur LC-1/5 & 81/23 |
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Mass: | 300,214 kg (661,857 lb) (June 18, 2008) |
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Length: | 58.2 m (191 ft) along truss (February 22, 2007) |
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Width: | 44.5 m (146 ft) from Destiny to Zvezda 73.15 m (240 ft) span of solar arrays (February 22, 2007) |
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Height: | 27.4 m (90 ft) (February 22, 2007) |
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Living volume: | 358 m³ (12,626 ft³) (June 18, 2008) |
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Atmospheric pressure: | 1013 hPa (29.91 inHg) | |
Perigee: | 350 km altitude (189 nmi) (February 22, 2008) |
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Apogee: | 354 km altitude (191 nmi) (October 22, 2008) |
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Orbit inclination: | 51.6419 degrees (October 22, 2008) |
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Typical orbit altitude: | 340.5 km (183.86 nmi) | |
Average speed: | 27,743.8 km/h (17,239.2 mph, 7706.6 m/s) |
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Orbital period: | 91.34 minutes | |
Orbits per day: | 15.72397664 (October 22, 2008) |
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Days in orbit: | 3994 (October 27, 2009) | |
Days occupied: | 3283 (October 27, 2009) | |
Number of orbits: | c.63034 (October 27, 2009) | |
Distance travelled: | c.2,000,000,000 km (1,100,000,000 nmi) |
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Statistics as of November 20, 2007 (unless noted otherwise). | ||
References: [1][2][3] | ||
Configuration | ||
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Station elements as of June 2008[update]. | ||
International Space Station |
The International Space Station (ISS) is a research facility currently being assembled in outer space, the on-orbit construction of which began in 1998. The space station is in a Low Earth Orbit and can be seen from Earth with the naked eye; it orbits at an altitude of approximately 350 km (190 mi) above the surface of the Earth,[4][5][6] and travels at an average speed of 27,700 kilometres (17,210 mi) per hour, completing 15.7 orbits per day.[4]
The space station is a joint project among the space agencies of the United States (NASA), Russia (RKA), Japan (JAXA), Canada (CSA) and eleven European countries (ESA).[7] The Brazilian Space Agency (AEB, Brazil) participates through a separate contract with NASA. The Italian Space Agency similarly has separate contracts for various activities not done in the framework of ESA's ISS works (where Italy also fully participates). China has reportedly expressed interest in the project,[8] especially if it was able to work with the RKA,[9] though it is not currently involved.[8]
The ISS is a continuation of several other previously planned space stations; Russia's Mir 2, the US Space Station Freedom, the European Columbus laboratory and the Japanese Kibō laboratory. The projected completion date is 2011, with the station remaining in operation at least until 2016. As of 2008[update], the ISS is larger than any previous space station.
The ISS has been continuously staffed since the first resident crew, Expedition 1, entered the station on November 2, 2000, thereby providing a permanent human presence in space. The crew of Expedition 18 are currently aboard. At present the station has a capacity for a crew of three, however, in order to fulfill an active research program, beginning with Expedition 20, it will be staffed by a resident crew of six.[10][11] Early crew members all came from the Russian and American space programs, until German ESA astronaut Thomas Reiter joined the Expedition 13 crew in July 2006, becoming the first crew member from another space agency. The station has been visited by astronauts from 16 different nations, and was the destination of the first five space tourists.
The station is serviced primarily by the US Space Shuttle and the Russian manned Soyuz spacecraft and unmanned Progress spacecraft. On March 9, 2008, the European Space Agency (ESA) launched an Ariane 5 with the first Automated Transfer Vehicle, Jules Verne, an unmanned spacecraft which carried over 8,000 kilograms of cargo to the ISS. Several other servicing vehicles are also in various stages of planning.
Contents |
With origins in the Cold War, the International Space Station represents a union of several different space station projects from various different nations. During the early 1980s, NASA planned to launch a modular space station, called Freedom, as a counterpart to the Soviet Salyut and Mir space stations, while the Soviets were planning a replacement for Mir, due to be constructed during the 1990s, called Mir-2.[12]
Due to budgetary and design constraints, Freedom never progressed past mockups and minor component tests, and, with the fall of the Soviet Union, ending the Cold War and Space Race, it was nearly cancelled by the US House of Representatives. The post-Soviet economic chaos in Russia also led to the postponement and eventual cancellation of Mir-2, with only the base block of that station, DOS-8, having been constructed.[12]
The similar difficulties faced by the US, Russia and other nations with plans for space stations prompted US administration officials to start negotiations with international partners in Europe, Russia, Japan and Canada in the early 1990s in order to build a truly international space station. In June 1992, American president George H. W. Bush and Russian president Boris Yeltsin agreed to join hands in space exploration by signing the "Agreement between the United States of America and the Russian Federation Concerning Cooperation in the Exploration and Use of Outer Space for Peaceful Purposes". The agreement called for the setting up a short, joint space program, during which one US astronaut would board the Russian space station Mir and two Russian cosmonauts would board a Space Shuttle. In September 1993, however, American Vice-president Al Gore and Russian prime minister Viktor Chernomyrdin announced plans for a new space station, later to be called the International Space Station.[13] They also agreed that, in preparation for this new project, America would be largely involved in the Mir program in the years ahead, as part of an agreement that later became the Shuttle-Mir Program.[14]
It was planned to combine the proposed space stations of all participating space agencies; Freedom, Mir-2 (with DOS-8 later becoming Zvezda), ESA's Columbus, and the Japanese Kibō laboratory. The first module, Zarya, was launched in 1998, and construction was expected to be complete by 2003.
The assembly of the International Space Station is a major aerospace engineering endeavour. When assembly is complete the ISS will have a pressurised volume of approximately 1,000 m³ (35,300 cubic feet). Assembly began in November 1998, and as of July 2008[update] the station is approximately 85% complete.
The first segment of the ISS, the Zarya FGB, was launched into orbit 20 November 1998 on a Russian Proton rocket, and was followed two weeks later by the first of three 'node' modules, Unity, launched aboard STS-88. This bare 2-module core of the ISS remained unmanned for the next one and a half years, until in July 2000 the Russian module Zvezda was added, allowing a maximum crew of three astronauts or cosmonauts to be on the ISS permanently - the first resident crew, Expedition 1, was sent that November. The year 2000 also saw the arrival of two segments of the station's Integrated Truss Structure, the Z1 and P6 truss, together providing the embryonic station with communications, guidance, electrical grounding (on Z1) and power via a pair of solar array wings (on P6).
Over the next two years the station continued to expand, with a Soyuz rocket delivering the Pirs docking compartment and Space Shuttles Discovery, Atlantis and Endeavour between them carrying the Destiny laboratory and Quest airlock to orbit, in addition to the station's robot arm, Canadarm2, and several more segments of the truss structure.
The ambitious expansion schedule was brought to an abrupt halt, however, following the destruction of the Space Shuttle Columbia on STS-107. The resulting hiatus in the Space Shuttle program led to a halt in station assembly until the launch of Discovery on STS-114 in 2005.
The official Return to Assembly was marked by the delivery by Atlantis, flying STS-115, of the station's second set of solar arrays, which were followed by several more truss segments and a third set of arrays on STS-116, STS-117 and STS-118. This major expansion of the station's power generating abilities meant that more pressurised modules could be accommodated, and as a result the Harmony node and Columbus European laboratory were added, followed shortly by the first two components of Kibō, the Japanese Experiment Module.
As of July 2008[update], the station consists of ten pressurised modules, and all but one of the components of the Integrated Truss Structure. Awaiting launch are the station's final set of solar arrays (set for delivery on STS-119), the final section of Kibō, the American Node 3, and the European Robotic Arm, in addition to several Russian modules. Also awaiting launch is the Alpha Magnetic Spectrometer, recently manifested on what is currently the final Space Shuttle flight, STS-134. Assembly is expected to be completed by 2011, by which point the station will have a mass in excess of 400 tonnes (440 short tons).[1][15]
The ISS is currently under construction, and will eventually consist of fourteen pressurised modules with a combined volume of around 1,000 m³. These modules include laboratories, docking compartments, airlocks, nodes and living quarters, nine of which are already in orbit, with the remaining five awaiting launch. Each module is launched either by Space Shuttle, Proton rocket or Soyuz rocket, and is listed below along with its purpose, launch date and mass.
Module | Assembly mission | Launch date | Launch vehicle | Nation | Mass | Isolated View | Station View |
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Zarya | 1A/R | November 20, 1998 | Proton-K | Russia (Builder) US (Financier) |
19,323 kg (42,600 lb) | ![]() |
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Provided electrical power, storage, propulsion, and guidance during initial assembly, now serves as a storage module (both inside the pressurised section and in the externally mounted fuel tanks). | |||||||
Unity (Node 1) | 2A | December 4, 1998 | Space Shuttle Endeavour, STS-88 | US | 11,612 kg (25,600 lb) | ![]() |
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First node module, connecting the American section of the station to the Russian section (via PMA-1). Provides berthing locations for the Z1 truss, Quest airlock, Destiny laboratory and Node 3. | |||||||
Zvezda (Service Module) | 1R | July 12, 2000 | Proton-K | Russia | 19,051 kg (42,000 lb) | ![]() |
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Station service module, providing main living quarters for resident crews, environmental systems and attitude and orbit control, in addition to docking locations for Soyuz spacecraft, Progress spacecraft and the Automated Transfer Vehicle. The addition of the module rendered the ISS permanently habitable for the first time. | |||||||
Destiny (US Laboratory) | 5A | February 7, 2001 | Space Shuttle Atlantis, STS-98 | US | 14,515 kg (32,000 lb) | ![]() |
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Primary research facility for US payloads aboard the ISS, Destiny provides the station with generic laboratory capabilities, with capacity for 24 International Standard Payload Racks. The laboratory also provides various environmental systems and living quarters to the station, and is the module to which most of the Integrated Truss Structure is affixed. | |||||||
Quest (Joint Airlock) | 7A | July 12, 2001 | Space Shuttle Atlantis, STS-104 | US | 6,064 kg (13,370 lb) | ![]() |
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Primary airlock for the ISS, hosting spacewalks with both US EMU and Russian Orlan spacesuits. Quest consists of two segments, the equipment lock that stores spacesuits and equipment, and the crew lock from which astronauts can exit into space. | |||||||
Pirs (Docking Compartment) | 4R | September 14, 2001 | Soyuz-U | Russia | 3,580 kg (7,900 lb) | ![]() |
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Provides the ISS with additional docking ports for Soyuz and Progress spacecraft, and allows egress and ingress for spacewalks by cosmonauts using Russian Orlan spacesuits, in addition to providing storage space for these spacesuits. | |||||||
Harmony (Node 2) | 10A | October 23, 2007 | Space Shuttle Discovery, STS-120 | Europe (Builder) US (Financier) |
14,288 kg (31,500 lb) | ![]() |
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The second of the station's node modules, Harmony is the utility hub of the ISS. The module contains four racks that provide electrical power, bus electronic data, and acts as a central connecting point for several other components via its six Common Berthing Mechanisms (CBMs). The European Columbus and Japanese Kibō laboratories are permanently berthed to the module, and US Space Shuttle Orbiters dock to the ISS via PMA-2, attached to Harmony's front port. In addition, the module serves as a berthing port for the Multi-Purpose Logistics Modules during logistics flights. | |||||||
Columbus (European Laboratory) | 1E | February 7, 2008[16] | Space Shuttle Atlantis, STS-122 | Europe | 12,800 kg (28,000 lb) | ![]() |
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Primary research facility for European payloads aboard the ISS, providing ten International Standard Payload Racks and mounting locations for external experiments, including the European Technology Exposure Facility, Solar Monitoring Observatory,Materials International Space Station Experiment and Atomic Clock Ensemble in Space. | |||||||
Experiment Logistics Module (JEM-ELM) | 1J/A | March 11, 2008 | Space Shuttle Endeavour, STS-123 | Japan | 8,386 kg (18,490 lb)[17] | ![]() |
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Part of the Kibō Japanese Experiment Module laboratory, the ELM provides storage and transportation facilities to the laboratory, with a pressurised section to serve internal payloads and an unpressurised section to serve external payloads. | |||||||
Japanese Pressurised Module (JEM-PM) | 1J | May 31, 2008 | Space Shuttle Discovery, STS-124 | Japan | 14,800 kg (33,000 lb)[18] | ![]() |
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Part of the Kibō Japanese Experiment Module laboratory, the PM is the core module of Kibō to which the ELM and Exposed Facility are berthed. The laboratory is the largest single ISS module, and contains a total of 23 racks, including 10 experiment racks.[19] | |||||||
Scheduled to be launched | |||||||
Module | Assembly mission | Launch date | Launch vehicle | Nation | Mass | Isolated View | Station View |
Mini-Research Module 2 | 5R | c. August 2009 | Soyuz-FG | Russia | |||
Not yet launched. The newest Russian component of the ISS, MRM2 will likely be used for docking and cargo storage aboard the station. | |||||||
Node 3 | 20A | c. December 2009 | Space Shuttle Endeavour, STS-130 | Europe (Builder) US (Financier) |
14,311 kg (31,550 lb) | ||
Not yet launched. The last of the station's US nodes, Node 3 will contain an advanced life support system to recycle waste water for crew use and generate oxygen for the crew to breathe. The node also provides four berthing locations for more attached pressurised modules or crew transportation vehicles, in addition to the permanent berthing location for the station's Cupola. | |||||||
Cupola | 20A | c. December 2009 | Space Shuttle Endeavour, STS-130 | Europe (Builder) US (Financier) |
1,800 kg (4,000 lb) | ![]() |
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Not yet launched. The Cupola is an observatory module that will provide ISS crew members with a direct view of robotic operations and docked spacecraft, as well as an observation point for watching the Earth. The module will come equipped with robotic workstations for operating the SSRMS and shutters to prevent its windows from being damaged by micrometeorites. | |||||||
Mini-Research Module 1 | ULF4 | c. April 2010 | Space Shuttle Discovery, STS-132 | Russia | 4,700 kg (10,000 lb) | ||
Not yet launched. MRM1 will be used for docking and cargo storage aboard the station. | |||||||
Multipurpose Laboratory Module | 3R | c. December 2011[15] | Proton-M | Russia | 21,300 kg (47,000 lb) | ![]() |
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Not yet launched. The MLM will be Russia's primary research module as part of the ISS, and will be used for experiments, docking and cargo logistics. It will also serve as a crew work and rest area, and will also be equipped with a backup attitude control system that can be used to control the station's attitude. |
The source of electrical power for the ISS is the Sun: light is converted into electricity through the use of solar arrays. Before assembly flight 4A (Space Suttle mission STS-97, November 30, 2000) the only power source was the Russian solar panels attached to the Zarya and Zvezda modules: the Russian segment of the station uses 28 volts DC (as does the Space Shuttle). In the remainder of the station, electricity is provided by the solar arrays attached to the truss at a voltage ranging from 130 to 180 volts DC. The power is then stabilized and distributed at 160 volts DC, before finally being converted to the user-required 124 volts DC - this high-voltage distribution line allows for smaller power lines, reducing weight. Power can be shared between the two segments of the station using converters, and this feature is essential since the cancellation of the Russian Science Power Platform, as the Russian segment will depend on the US built solar arrays for power.[20]
The solar array normally tracks the Sun to maximize the amount of solar power. The array is about 375 m² (450 yd²) in area and 58 metres (190 ft) long. In the fully-complete configuration, the solar arrays track the sun in each orbit by rotating the alpha gimbal; while the beta gimbal adjusts for the angle of the sun from the orbital plane. (Until the main truss structure arrived, the arrays were in a temporary position perpendicular to the final orientation, and in this configuration, as shown in the image to the right, the beta gimbal was used for the main solar tracking.) Another tracking option, Night Glider mode, can be used to reduce the effects of drag produced by the tenuous upper atmosphere through which the station flies by orienting the solar arrays edgewise to the velocity vector.
The attitude (orientation) of the station is maintained by either of two mechanisms. Normally, a system using several control moment gyroscopes (CMGs) keeps the station oriented, with Destiny forward of Unity, the P truss on the port side and Pirs on the earth-facing (nadir) side. When the CMG system becomes saturated (a situation whereby a CMG exceeds its operational range or cannot track a series of rapid movements, and stops working) it can lose its ability to control station attitude. In this event, the Russian attitude control system is designed to take over automatically, using thrusters to maintain station attitude and allowing the CMG system to desaturate, a situation which has occurred once, during Expedition 10.[21] When a Space Shuttle is docked to the station, it can also be used to maintain station attitude. This procedure was used during STS-117 as the S3/S4 truss was being installed.
The ISS is maintained at an orbit from a minimum altitude limit of 278 km (173 mi) to a maximum limit of 460 km (286 mi). The normal maximum limit is 425 km (264 mi) to allow Soyuz rendezvous missions. Because ISS is constantly losing altitude due to slight atmospheric drag and gravity gradient effects, it needs to be boosted to a higher altitude several times each year.[22] These effects vary from day-to-day, however, due to changes in the density of the outer atmosphere due to solar activity.[23] The boosting can be performed by two boosters on the Zvezda module, a docked Space Shuttle, a Progress resupply vessel or by ESA's ATV and takes approximately two orbits (three hours) in which it is boosted several kilometers higher.[22]
At the station's orbital altitude, the gravity from the Earth is 88% of that at sea level. The state of weightlessness is due to the constant free fall of the ISS, which according to the equivalence principle, is indiscernible from being in a state of zero gravity. The environment on the station is often described instead as microgravity, due to four effects:
The ISS Environmental Control and Life Support System (ECLSS) provides or controls elements such as atmospheric pressure, fire detection and suppression, oxygen levels and water supply. The highest priority for the ECLSS is the ISS atmosphere, but the system also collects, processes, and stores waste and water produced and used by the crew. For example, the system recycles fluid from the sink, shower, urine, and condensation. The Elektron system aboard Zvezda and a similar oxygen generation system in Destiny generate oxygen aboard the station.[25] If required, the crew has a backup option in the form of bottled oxygen and Solid Fuel Oxygen Generation (SFOG) canisters.[26] Carbon dioxide is removed from the air by the Vozdukh system in Zvezda, whilst other waste gases and byproducts of human metabolism are removed by activated charcoal filters.[26]
The atmosphere on board the ISS is maintained to have a composition similar to that of the Earth's atmosphere.[27] Normal air pressure on the ISS is 101.3 kPa (14.7 psi),[28] the same as at sea level on Earth.
Due to the size of the International Space Station, about that of an American football field, and particularly due to the large reflective area offered by its solar panels, ground based observation of the station is possible with the naked eye if one is within 63 degrees latitude. In many cases the station is one of the brightest naked-eye objects in the sky, though it is only visible for brief periods of time. This is because the station is in low earth orbit, and the sun angle and observer locations need to coincide.[29]
NASA provides data on forthcoming opportunities for viewing the ISS (and other objects) on the Station Sightings web page, as do the European Space Agency and the independent site Heavens-Above.[29][30]
All permanent station crews are named "Expedition n", where n is sequentially increased after each expedition. Expeditions have an average duration of half a year and are often considered synonymous with "Increments." However, "Increments" are distinguished from Expeditions as the program planning period for activities that are to occur during a particular Expedition's residence on ISS. The start of both an Expedition and an Increment is defined by the departure of the previous Expedition crew on a Soyuz spacecraft. The definition of the Increment is in flux in preparation for 6-person crews that will be broken up into 3-person crews which overlap in their 6-month missions on ISS.
The International Space Station is the most-visited spacecraft in the history of space flight. As of April 11, 2008[update], it has had 213 (non-distinct) visitors. Mir had 137 (non-distinct) visitors.[12] The number of distinct visitors of the ISS is 167.[31] The current expedition to ISS is Expedition 18.[32]
The ISS uses Coordinated Universal Time (UTC, sometimes informally called GMT) to regulate its onboard day. The windows are covered at "night" to give the impression of darkness since it experiences 16 sunrises and sunsets a day. During visiting Space Shuttle missions, the ISS crew will mostly follow the shuttle's Mission Elapsed Time (MET), which is a flexible timezone based solely on the launchtime of the mission.[33][34] Because the sleeping periods between the UTC timezone and the MET usually differ, the ISS crew often has to adjust their sleeping pattern before the Space Shuttle arrives and after it leaves to shift from one timezone to the other, a practise known as sleepshifting.
A typical day for the crew would begin with a wake-up at 06:00, followed by 'post-sleep' activities and a morning inspection of the station. The crew then breakfasts and takes part in a daily planning conference with Mission Control on the ground, before starting work at around 08:10. The first scheduled exercise of the day follows, after which the crew continues work until 13:05. Following a one-hour lunch break, the afternoon consists of more exercise and work, before the crew carries out its 'presleep' activities, beginning at 19:30, including dinner and a crew conference. The scheduled sleep period begins at 21:30, at which point the daily schedule is complete. In general, the crew works 10 hours per day on a weekday, and 5 hours on Saturdays, with the rest of the time being their own, for relaxation, games or work catch-up.[35]
One of the main goals of the ISS is to provide a place to conduct experiments that require one or more of the unusual conditions present on the station. The main fields of research include biology (including biomedical research and biotechnology), physics (including fluid physics, materials science, and quantum physics), astronomy (including cosmology), and meteorology.[36][37] The 2005 NASA Authorization Act designated the U.S segment of the International Space Station as a national laboratory with a goal to increase the utilisation of the ISS by other Federal entities and the private sector. As of 2007[update], little experimentation other than the study of the long-term effects of microgravity on humans has taken place. With four new research modules set to arrive at the ISS by 2011, however, more specialized research is expected to begin.
The Destiny laboratory is the main research facility currently aboard the ISS. Produced by NASA and launched in February 2001, it is a research facility for general experiments, providing space for 24 International Standard Payload Racks, some of which are used for environmental systems and living equipment. Destiny also features a 20 inch, optically perfect window, the largest such window ever produced for use in space.[38][39]
The Columbus module is another research facility, designed and built by the European Space Agency. Launched in February 2008, it provides a generic laboratory as well as facilities specifically designed for biology, biomedical research and fluid physics. The laboratory also provides external mounting locations for experiments such as the European Technology Exposure Facility, Solar Monitoring Observatory,Materials International Space Station Experiment and Atomic Clock Ensemble in Space. A number of expansions are planned to study quantum physics and cosmology.
The Japanese Experiment Module, also known as Kibō, was put in service during STS-124 on June 3, 2008. It was developed by JAXA to function as an observatory and to gather astronomical data. The module also provides an external platform, the Exposed Facility, that allows payloads to be directly exposed to the harsh space environment, and which is serviced by the module's own robotic arm, the JEM-RMS.
The station is also planned to carry a particle physics experiment, called the Alpha Magnetic Spectrometer (AMS), which will be launched on STS-134 and mounted externally on the Integrated Truss Structure. The AMS will search for various types of unusual matter by measuring cosmic rays, and its experiments will help researchers study the formation of the universe and search for evidence of dark matter and antimatter.
The ExPRESS Logistics Carriers, developed by NASA, are set to be launched for the ISS beginning with STS-129, which is expected to take place no earlier than September 11, 2009.[40] They will allow experiments to be deployed and conducted in the vacuum of space and will provide the necessary electricity and computing to locally process data from experiments. Finally, the Multipurpose Laboratory Module, created by the RKA, is expected to launch for the ISS in December 2011, and will be the primary Russian laboratory on the station.[15] It will supply the proper resources for general microgravity experiments.[41]
Several planned research modules have been cancelled, including the Centrifuge Accommodations Module (used to produce varying levels of artificial gravity) and two Russian Research Modules (used for general experimentation).
There are a number of plans to study biology on the ISS. One goal is to improve understanding of the effect of long-term space exposure on the human body. Subjects such as muscle atrophy, bone loss, and fluid shifts are studied with the intention to use this data so space colonization and lengthy space travel can become feasible (at present levels of bone loss and muscular atrophy, there would be a significant risk of fractures and movement problems if astronauts landed on an extraterrestrial planet following a lengthy space cruise[42]). The effect of near-weightlessness on evolution, development and growth, and the internal processes of plants and animals are also studied. In response to recent data suggesting that microgravity enables the growth of three-dimensional human body-like tissues and that unusual protein crystals can be formed in space, NASA has indicated a desire to investigate these phenomena.[36]
Prominent physics problems are also studied - the physics of fluids in microgravity are not completely understood, and researchers would like to be able to accurately model fluids in the future. Additionally, since fluids in space can be combined nearly completely regardless of their relative weights, there is some interest in investigating the combination of fluids that would not mix well on Earth. By examining reactions that are slowed down by low gravity and temperatures, scientists also hope to gain new insight concerning states of matter (specifically in regards to superconductivity).[36]
Additionally, researchers hope to examine combustion in the presence of less gravity than on Earth. Any findings involving the efficiency of the burning or the creation of byproducts could improve the process of energy production, which would be of economic and environmental interest. Scientists plan to use the ISS to examine aerosols, ozone, water vapor, and oxides in Earth's atmosphere as well as cosmic rays, cosmic dust, antimatter, and dark matter in the Universe.[36]
The long-term goals of this research are to develop the technology necessary for human-based space and planetary exploration and colonization (including life support systems, safety precautions, environmental monitoring in space), new ways to treat diseases, more efficient methods of producing materials, more accurate measurements than would be possible to achieve on Earth, and a more complete understanding of the Universe.[36][37]
As of November 28, 2008[update]:
As a multinational collaborative project, the legal and financial aspects of the ISS are detailed and complex — governing ownership of modules, crewing and utilisation of the station, and responsibilities for station resupply.
The main legal document establishing obligations and rights between the ISS partners is the Space Station Intergovernmental Agreement (IGA), an international treaty signed on January 28, 1998, by fifteen governments involved in the Space Station project. This set the stage for a second layer of agreements, called Memoranda of Understanding (MOU), between NASA and Roskosmos, ESA, CSA and JAXA. These MOUs are then further split, for instance into contractual obligations between nations and trading of partners rights and obligations. Use of the Russian Orbital segment is also negotiated at this level, whereas the other sections of the station have been agreed to be assigned as follows:
The most cited figure of an estimate of overall costs of the ISS ranges from 35 billion to 100 billion USD.[45] ESA, the only agency actually stating potential overall costs, estimates €100 billion for the entire station over at least a ten year period.[46] Giving a precise cost estimate for the ISS is not straightforward, as it is difficult to determine which costs should actually be contributed to the ISS program, or how the Russian contribution should be measured.
NASA Administrator Michael D. Griffin says the International Space Station has a role to play as NASA moves forward with a new focus for the manned space program, which is to go out beyond Earth orbit for purposes of human exploration and scientific discovery. "The International Space Station is now a stepping stone on the way, rather than being the end of the line." stated Griffin.[47] Griffin has said that station crews will not only continue to learn how to live and work in space, but also will learn how to build hardware that can survive and function for the years required to make the round-trip voyage from Earth to Mars.[47]
Despite this view, however, in an internal e-mail leaked to the press on August 18, 2008, from Griffin to NASA managers,[48][49][50] Griffin apparently communicated his belief that the current US administration had made no viable plan for US crews to participate in the ISS beyond 2011, and that the Office of Management and Budget (OMB) and Office of Science and Technology Policy (OSTP) were actually seeking its demise.[49] The email appeared to suggest that Griffin believed the only reasonable solution was to extend the operation of the Space Shuttle beyond 2010, but noted that Executive Policy (i.e., the White House) was firm that there will be no extension of the Space Shuttle retirement date, and thus no US capability to launch crews into orbit until the Ares I/Orion system becomes operational in 2014, at the earliest.[49] He did not see purchase of Russian launches for NASA crews as politically viable following the 2008 South Ossetia war, and hoped the incoming US administration would resolve the issue in 2009 by extending Space Shuttle operations beyond 2010.
On September 7, 2008, NASA released a statement regarding the leaked email, in which Griffin said:
"The leaked internal email fails to provide the contextual framework for my remarks, and my support for the administration's policies. Administration policy is to retire the Space Shuttle in 2010 and purchase crew transport from Russia until Ares and Orion are available. The administration continues to support our request for an INKSNA exemption. Administration policy continues to be that we will take no action to preclude continued operation of the International Space Station past 2016. I strongly support these administration policies, as do OSTP and OMB."
—Michael D. Griffin, [51]
On October 15, 2008, President Bush signed the NASA Authorization Act of 2008, giving NASA funding for one additional mission to "deliver science experiments to the station".[52][53][54][55] The Act allows for an additional space shuttle flight, STS-134, to the ISS to install the Alpha Magnetic Spectrometer, which was previously cancelled.[56]
As president-elect, Barack Obama has supported the continued operation of the station, and supported the NASA Authorization act of 2008.[56] Obama's plan for space exploration includes finishing the station, and completion of the Orion spacecraft program.[57]
As of 2008[update] there have been six space tourists to the ISS, each paying around US $25 million; the tourists, or Spaceflight participants, were launched and returned via Russian crew rotation missions on Soyuz spacecraft. In addition, the ISS was the location for the first 'space wedding', during which Russian cosmonaut Yuri Malenchenko, flying Expedition 7, married Ekaterina Dmitrieva, who was in Texas at the time.
Golf Shot Around The World was an event in which, on an EVA during Expedition 14, a special golf ball, equipped with a tracking device, was hit from the station and sent into its own low Earth orbit for a fee paid by a Canadian golf equipment manufacturer to the Russian Space Agency.[58]
Japanese scientists and origami masters propose to launch a flotilla of paper planes from the ISS in early 2009.[59] Around 30 planes will make the descent, each gliding downward over what is expected to be the course of several months. If one of the planes survives to Earth, it will have made the longest flight ever by a paper plane, traversing some 400 km (250 mi), and will have demonstrated the feasibility of slow-speed, low-friction atmospheric reentry. A prototype of the origami aeroplane passed a durability test in a wind tunnel in March 2008, and Japan's space agency adopted it for feasibility studies.[60]
The Space Shuttle Columbia disaster on February 1, 2003, resulted in a two-and-a-half-year suspension of the US Space Shuttle program. Another one-year suspension following STS-114 due to continued foam shedding on the external tank resulted in some uncertainty about the future of the International Space Station. All crew exchanges between February 2003 and July 2006 were carried out solely using the Russian Soyuz spacecraft (STS-114 in July 2005 was a logistics-only visit). 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 Space Shuttle for over three years, a larger than planned amount of waste had accumulated, temporarily hindering station operations in 2004, but automated Progress transports and the STS-114 mission were able to eliminate this waste build-up.
On September 18, 2006, the Expedition 13 crew activated a smoke alarm in the Russian segment of the International Space Station when fumes from one of the three oxygen generators triggered momentary fear about a possible fire. The crew initially reported smoke in the cabin, as well as a smell. The alarm was later found to be caused by a leak of potassium hydroxide from an oxygen vent, and the associated equipment was turned off, with officials saying that there was no fire and the crew was not in any danger.
The station's ventilation system was shut down to prevent the spread of smoke or contaminants through the rest of the complex. A charcoal air filter was put in place to help scrub the atmosphere of any lingering potassium hydroxide fumes. The space station's program manager said the crew never donned gas masks, but as a precaution put on surgical gloves and masks to prevent contact with any contaminants.[61]
On November 2, 2006, the payload brought by the Russian Progress M-58 allowed the crew to repair the Elektron using spare parts.[62]
On June 14, 2007, during Expedition 15 and flight day 7 of STS-117's visit to ISS, a computer malfunction on the Russian segments at 06:30 UTC left the station without thrusters, oxygen generation, carbon dioxide scrubber, and other environmental control systems, causing the temperature on the station to rise. A successful restart of the computers resulted in a false fire alarm that woke the crew at 11:43 UTC.[63][64]
By June 15, the primary Russian computers were back online, and communicating with the US side of the station by bypassing a circuit, but secondary systems remained offline.[65] NASA reported that without the computer that controls the oxygen levels, the station had 56 days of oxygen available.[66]
By the afternoon of June 16, ISS Program Manager Michael Suffredini confirmed that all six computers governing command and navigation systems for Russian segments of the station, including two thought to have failed, were back online, and would be tested over several days. The cooling system was the first system brought back online. Troubleshooting of the failure by the ISS crew found that the root cause was condensation inside the electrical connectors, leading to a short-circuit that triggered the "power off" command line leading to all three of the redundant processing units.[67] This was initially a concern, because the European Space Agency uses the same computer systems, supplied by EADS Astrium Space Transportation, for the Columbus laboratory module and the Automated Transfer Vehicle.[68] Once the root cause was understood, plans were implemented to avoid the problem in the future.
On October 30, 2007, during Expedition 16 and flight day 7 of STS-120's visit to ISS, following the reposition of the P6 truss segment, ISS and Space Shuttle Discovery crew members began the deployment of the two solar arrays on the truss. The first array deployed without incident, and the second array deployed about 80% before astronauts noticed a 76-centimetre (2.5 ft) tear. The arrays had been deployed in earlier phases of the space station's construction, and the retraction necessary to move the truss to its final position had gone less smoothly than planned.[69]
A second, smaller tear was noticed upon further inspection, and the mission's spacewalks were completely replanned in mere days to devise a repair — normally such spacewalks take several months to plan and are settled upon well in advance. On November 3, spacewalker Scott Parazynski assisted by Douglas Wheelock fixed the torn panels using makeshift "cufflinks" and riding on the end of the Space Shuttle's OBSS inspection arm; the first ever spacewalker to do so. The spacewalk was regarded as significantly more dangerous than most due to the possibility of shock from the electricity generating solar arrays, the unprecedented usage of the OBSS, and the lack of spacewalk planning and training for the impromptu procedure. Parazynski was, however, able to repair the damage as planned and the repaired array was fully deployed.[70]
During STS-120, a problem was detected in the starboard Solar Alpha Rotary Joint (SARJ). This joint, together with a similar device on the port side of the station's truss structure, rotates the large solar arrays to keep them facing the Sun. Excessive vibration and high current spikes in the array drive motor were noted, resulting in a decision to substantially curtail motion of the starboard SARJ until the cause was understood. Inspections during EVAs on STS-120 and STS-123 showed extensive contamination from metallic shavings and debris in the large drive gear, and confirmed damage to the large metallic race ring at the heart of the joint.[71] To prevent further damage, the joint was locked in place, the station having sufficient operating power to carry out its near-term science program with only modest impacts on operations.
On September 25, 2008, NASA announced significant progress in diagnosing the source of the starboard SARJ problem, and a programme to repair it on orbit, which began with the flight of the Space Shuttle Endeavour on STS-126, the most recent mission to the ISS. The crew carried out servicing of both the starboard and port SARJs, lubricating both joints and replacing 11 of 12 Trundle Bearings on the starboard SARJ.[72][73] It was hoped that this servicing would provide a temporary solution to the problem, with the long-term solution being a 10-EVA plan called 'SARJ-XL', which calls for the installation of structural supports between the two segments of the SARJ, and a new race ring to then be inserted between them, to completely replace the failed joint.[74] However, following the cleaning and lubrication of the joint, the results that have been noted so far have been extremely encouraging, to the point that it is now believed that the joint could be simply be maintained by occasional servicing EVAs by resident station crews. Nevertheless, the data from the SARJ will require several weeks to fully analyse before a final decision as to the future of the joint is made.[75]
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