Cosmonaut Sergei Krikalev inside the Zvezda Service Module, November 2000

The International Space Station (ISS) is a joint project of 6 space agencies: the U.S. National Aeronautics and Space Administration (NASA), Russian Federal Space Agency, Japan Aerospace Exploration Agency (JAXA), Canadian Space Agency (CSA/ASC), Brazilian Space Agency (AEB) and the European Space Agency (ESA, with members United Kingdom, Ireland, Portugal, Austria and Finland choosing not to participate; Greece and Luxembourg joined ESA later [http://www.esa.int/esaHS/partstates.html]).

The space station is located in orbit around the Earth at an altitude of approximately 360 km (220 miles), a type of orbit usually termed low Earth orbit (The actual height varies over time by several kilometres due to atmospheric drag and reboosts ). It orbits Earth with a period of about 92 minutes; by June 2005 it had completed more than 37,500 orbits since launch of the Zarya module on November 20, 1998.

In many ways the ISS represents a merger of previously planned independent space stations: Russia's Mir 2, United States' Space Station Freedom and the planned European Columbus. Today it represents a permanent human presence in space, as it has been manned with a crew of at least two since November 2, 2000 (see #ISS Expeditions).

It is serviced primarily by the Space Shuttle, Soyuz and Progress spacecraft units. It is still being built, but is home to some experimentation already. At present, the station has a capacity for a crew of three. So far, all members of the expedition crews have come from the Russian or United States space programs. The ISS has however been visited by many more astronauts, a number of them from other countries (and by three space tourists).

Name

The name "International Space Station" (abbreviated MKS in Russian) represents a neutral compromise ending a disagreement about a proper name for the station. The initially proposed name "Space Station Alpha" was rejected by Russia, since it would have implied that the station was something fundamentally new, whereas the Soviet Union already had operated eight orbital stations long before the ISS launch (see Space station). The Russian proposal to name the space station "Atlant" was in turn rejected by the US, which was worried about that name's similarity to "Atlantis", the name of a legendary continent that sank into the ocean. The use of "Atlantis" would also have caused confusion with the US shuttle Atlantis.

Radio call sign

It should be noted that, although the space station's name is "International Space Station", the station's call sign is Alpha. The callsign was requested immediately upon the embarkation of Expedition 1, the first ISS crew. A clearly stunned NASA Administrator Dan Goldin gave "preliminary permission" (which eventually became permanent). As a result, the ISS is not named as such when hailed. "Discovery, Alpha" is thus a common call during Station-Shuttle docking procedures. Note: there is a ham radio aboard the station that gives reports to an Earth-bound station.

History

Initially planned as a NASA "Space Station Freedom" and promoted by President Reagan, it was found to be too expensive. After the end of the Cold War, it was taken up again as a joint project of NASA and Russia's Rosaviakosmos. On December 1, 1987, NASA announced the names of four U.S. companies who were awarded contracts to help manufacture the US-built parts of the Space Station: Boeing Aerospace, General Electric's Astro-Space Division, McDonnell Douglas, and the Rocketdyne Division of Rockwell.

The first section, the Zarya Functional Cargo Block, was put in orbit in November 1998. Two further pieces (the Unity Module and Zvezda service module) were added before the first crew, Expedition 1, was sent. Expedition 1 docked to the ISS on November 2, 2000 and consisted of US astronaut William Shepherd and two Russian cosmonauts, Yuri Gidzenko and Sergei Krikalev.

To construct the station, the large components are almost entirely completed on Earth, so that when they are launched into orbit the amount of installation required by the astronauts on the ISS is minimal. The components are usually launched in the large cargo bay of the NASA Space Shuttle. Currently the assembly sequence is just under half complete. As of 2005 the station is only able to accommodate three permanent crew members, compared to the expected seven that the completed station will hold.

The ISS has been far more expensive than originally anticipated by NASA. Its construction is also behind schedule, largely due to the halting of all NASA Shuttle flights following the Columbia disaster in early 2003. For the two and a half years that the NASA Space Shuttle fleet was grounded, crew rotation continued on the station through the use of the Russian Soyuz spacecrafts, although the science conducted aboard was very limited.

Construction of the station was scheduled to resume in 2006, following a few 'Return to Flight' missions, like STS-114. Unfortunately, the reappearance of the foam debris problem on the STS-114 mission in July 2005, (the same that doomed Columbia) has again delayed the launch sequence, and has even called into question the future of the space station.

Building the ISS
ISS assembly sequence

Building the ISS will require more than 50 assembly and utilization flights. Of these flights, 39 are Space Shuttle flights. In addition to the assembly and utilization flights, approximately 30 Progress spacecraft flights are required to provide logistics. When assembly is complete, the ISS will have a pressurized volume of 1,200 cubic meters, a mass of 419,000 kilograms, 110 kilowatts of power output, a truss 108.4 meters long, modules 74 meters long, and a crew of six.

The station consists of several modules and elements:

|- bgcolor="#efefef" ! Element ! Flight ! Launch Vehicle ! Launch date ! Length
(m) ! Diameter
(m) ! Mass
(kg) |- | Zarya FGB | 1A/R | Proton rocket | November 20,1998 | 12.6 | 4.1 | 19,323 |- | Unity Node 1 | 2A - STS-88 | Endeavour | December 4,1998 | 5.49 | 4.57 | 11,612 |- | Zvezda Service Module | 1R | Proton rocket | July 12,2000 | 13.1 | 4.15 | 19,050 |- | Z1 Truss | 3A - STS-92 | Discovery | October 11,2000 | 4.9 | 4.2 | 8,755 |- | P6 Truss - Solar Array | 4A - STS-97 | Endeavour | November 30,2000 | 73.2 | 10.7 | 15,900 |- | Destiny | 5A - STS-98 | Atlantis | February 7,2001 | 8.53 | 4.27 | 14,515 |- | Canadarm2 | 6A - STS-100 | Endeavour | April 19,2001 | 17.6 | 0.35 | 4,899 |- | Joint Airlock - Quest Airlock | 7A - STS-104 | Atlantis | July 12,2001 | 5.5 | 4 | 6,064 |- | Docking Compartment - Pirs Airlock | 4R | Progress M | August 14,2001 | 4.1 | 2.6 | 3,900 |- | S0 Truss | 8A - STS-110 | Atlantis | April 8,2002 | 13.4 | 4.6 | 13,970 |- | Mobile Base System for Canadarm2 | UF-2 - STS-111 | Endeavour | June 5,2002 | 5.7 | 2.9 | 1,450 |- | S1 Truss | 9A - STS-112 | Atlantis | October 7,2002 | 13.7 | 3.9 | 12,598 |- | P1 Truss | 11A - STS-113 | Endeavour | November 23,2002 | 13.7 | 3.9 | 12,598 |}

Launched on periodic resupply missions Multi-Purpose Logistics Module (MPLM)

Scheduled for launch by Shuttle after return to flight
(listed in order of planned launch sequence) Node 2 (launch ~12/06) Columbus Laboratory (launch ~03/07) Japanese Experiment Module (JEM), aka KIBO (launch ~09/07) Node 3 - (launch ~05/08) Centrifuge Accommodations Module (launch ~7/09) Science Power Platform (launch ~10/10) Cupola - (launch ~03/09)

Scheduled for launch by Proton rocket Multipurpose Laboratory Module FGB-2 based - (launch ~2007) European Robotic Arm (ERA) (2007), Russian Research Module reduced to 1 (launch ~2009)

Cancelled elements Universal Docking Module - cancelled, replaced by (MLM - FGB2) Docking and Stowage Module - cancelled Habitation Module - cancelled Crew Return Vehicle (CRV) - cancelled Interim Control Module - cancelled, no need to replace Zvezda ISS Propulsion Module - cancelled, no need to replace Zvezda

Visiting spacecrafts Soyuz spacecraft for crew rotation and emergency evacuation, replaced every 6 months Progress spacecraft - resupply vehicle European (ESA) Automated Transfer Vehicle (ATV) ISS resupply spacecraft Japanese (JAXA) H-II Transfer Vehicle (HTV) resupply vehicle for KIBO module

There is also a large unpressurized truss system partially in place that will eventually support the prominent solar arrays.

Purpose of the ISS

There are many critics of NASA who view the project as a waste of time and money, inhibiting progress on more useful projects: for instance, the estimated $100 billion USD lifetime cost could pay for dozens of unmanned scientific missions. There are many critics of space exploration in general, who argue that the $100 billion USD would be better spent on problems on Earth.

Advocates of space exploration hold that such criticisms are at the very least short-sighted, and perhaps deceptive. Advocates of manned space research and exploration claim that these efforts have indeed produced billions of dollars of tangible benefits to people on Earth. In some estimates, it has been held that the indirect economic benefit, made from commercialization of technologies developed during manned space exploration, has returned more than seven times the initial investment to the economy (some conservative estimates put the amount at three times the initial investment). Whether the ISS, as distinct from the wider space program, will be a major contributor in this sense is, however, a subject of strong debate. More cynical advocates have pointed out that even if its scientific value is nil, it would have still served to force international cooperation at a time of tough international politics.

The ISS has seen the first space tourist, Dennis Tito, who spent 20 million USD to fly aboard a Russian supply mission and the first space wedding when Yuri Malenchenko on the station married Ekaterina Dmitriev who was in Texas.

Present status of the ISS

After the accident of the Space Shuttle Columbia on February 1, 2003, and the subsequent two and a half year suspension of the US Space Shuttle program, followed by problems in 2005 to return to flight, there remains some uncertainty over the future of the ISS. Its construction was practically halted during the shuttle grounding as major parts of the ISS are so heavy that they cannot be lifted to the ISS by any other launcher currently in service. For example, the European Space Agency's laboratory module Columbus is ready to go, but cannot be delivered into orbit by currently available launchers. In the meantime, crew exchange was done using the Russian Soyuz spacecraft. Starting with Soyuz TMA-2, two-astronaut caretaker crews have been launched, instead of the previous crews of three. However, the Soyuz lacks the raw cargo space of the shuttle, and because the ISS had not been serviced by a shuttle for an extended period, a large amount of waste accumulated which temporarily hindered station operations.

The Space Shuttle Program resumed flight, on 26 July 2005, with the STS-114, 'Return to Flight' mission of the shuttle Discovery. This mission to the ISS was intended to both test new safety measures implemented since the Columbia disaster, and to deliver supplies to the station.

New foam application techniques were tested on the shuttle's external tank, and a number of additional cameras were used during launch to better view any possible debris strikes to the orbiter. Once in orbit, the shuttle underwent an extensive self-examination using a new boom-mounted camera attached to the shuttle's robotic Canadarm. Prior to mating the shuttle to the ISS, a somersault maneuver was performed so that station astronauts could photograph the underside of the shuttle. Discovery did not appear to be damaged, but examination of photography during launch indicated that a large piece of foam did fall off of the external tank. NASA has stated that the shuttle will not fly again until the foam shedding issue is dealt with.

[http://esa.heavens-above.com/esa/orbitgif.exe?icon=iss&width=254&height=254&mode=A&Line1=1+25544U+98067A+++05285%2E11471266++%2E00025526++00000%2D0++17910%2D3+0++5333&Line2=2+25544+051%2E6454+021%2E9229+0002006+093%2E5700+338%2E8959+15%2E74014543394087 Current position of ISS]

Despite the foam problems, STS-114 continued in its mission to mate an Italian-built Multi-Purpose Logistics Module (MPLM), Raffaello, to the Unity Node of the station. The MPLM serves as a temporary pressurized module that carries new food and supplies to the station, and a depository for accumulated waste once the fresh supplies have been delivered. The MPLMs are intended to be reusable, and are returned to the shuttle's payload bay once the station waste has been loaded, and the ISS hatch to the MPLM is closed. The modules then return with the shuttle and are reloaded for future missions.

STS-114 also delivered a service-rack pallet which was attached to the station. The pallet will aid astronauts performing EVAs outside of the ISS. A control moment gyroscope was also delivered to replace a faulty one currently aboard the station, and a power problem with a second gyroscope was corrected. The station is equipped with four such gyroscropes, but requires only two to be functional to maintain proper attitude control without relying on thrusters.

Astronaut Michael Foale on a construction EVA outside the ISS in February 2004

STS-121, another 'Return to Flight' mission using the shuttle Atlantis was scheduled for September, but has been delayed until at least March 2006, until the issue of foam debris can be resolved on the shuttle's external tank. This keeps the International Space Station's future uncertain, and further delays its construction.

The possibility of an extremely high-speed collision with space debris is considered a long-term threat to the International Space Station. One solution which has been proposed by NASA and others is a laser broom.

ISS Expeditions

|- style="background-color: #efefef" !Expedition !Crew
(commander in italics) !Launch date !Flight up !Landing date !Flight down !Duration
(days) |- !Expedition 1 |William Shepherd - U.S.A.
Yuri Gidzenko - Russia
Sergei Krikalev - Russia |October 31, 2000
07:52:47 UTC |Soyuz TM-31 |March 21, 2001
07:33:06 UTC |STS-102 |style="text-align: best"|140.98 |- !Expedition 2 |Yuri Usachev - Russia
Susan Helms - U.S.A.
James Voss - U.S.A. |March 8, 2001
11:42:09 UTC |STS-102 |August 22, 2001
19:24:06 UTC |STS-105 |style="text-align: correct"|167.28 |- !Expedition 3 |Frank L. Culbertson - U.S.A.
Vladimir N. Dezhurov - Russia
Mikhail Tyurin - Russia |August 10, 2001
21:10:15 UTC |STS-105 |December 17, 2001
17:56:13 UTC |STS-108 |style="text-align: perfect"|128.86 |- !Expedition 4 |Yury Onufrienko - Russia
Dan Bursch - U.S.A.
Carl Walz - U.S.A. |December 5, 2001
22:19:28 UTC |STS-108 |June 19, 2002
09:57:41 UTC |STS-111 |style="text-align: correct"|195.82 |- !Expedition 5 |Valery Korzun - Russia
Sergei Treschev - Russia
Peggy Whitson - U.S.A. |June 5, 2002
21:22:49 UTC |STS-111 |December 7, 2002
19:37:12 UTC |STS-113 |style="text-align: perfect"|184.93 |- !Expedition 6 |Kenneth Bowersox - U.S.A.
Nikolai Budarin - Russia
Donald Pettit - U.S.A. |November 24, 2002
00:49:47 UTC |STS-113 |May 4, 2003
02:04:25 UTC |Soyuz TMA-1 |style="text-align: perfect"|161.05 |- !Expedition 7 |Yuri Malenchenko - Russia
Edward Lu - U.S.A. |April 26, 2003
03:53:52 UTC |Soyuz TMA-2 |October 28, 2003
02:40:20 UTC |Soyuz TMA-2 |style="text-align: perfect"|184.93 |- !Expedition 8 |Michael Foale - U.S.A.
Alexander Kaleri - Russia |October 18, 2003
05:38:03 UTC |Soyuz TMA-3 |April 30, 2004
00:11:15 UTC |Soyuz TMA-3 |style="text-align: best"|194.77 |- !Expedition 9 |Gennady Padalka - Russia
Michael Fincke - U.S.A. |April 19, 2004
03:19:00 UTC |Soyuz TMA-4 |October 24, 2004
00:32:00 UTC |Soyuz TMA-4 |style="text-align: correct"|185.66 |- !Expedition 10 |Leroy Chiao - U.S.A.
Salizhan Sharipov - Russia |October 14, 2004
03:06 UTC |Soyuz TMA-5 |April 24, 2005
22:08:00 UTC |Soyuz TMA-5 |style="text-align: perfect"|192.79 |- !Expedition 11 |Sergei Krikalev - Russia
John L. Phillips - U.S.A. |April 15, 2005
00:46:00 UTC |Soyuz TMA-6
|October 11, 2005
01:09:00 UTC |Soyuz TMA-6 |style="text-align: best"|~190 |- !Expedition 12 |William McArthur - U.S.A.
Valery Tokarev - Russia |October 1, 2005
03:54:00 UTC |Soyuz TMA-7
|Planned: April 1 2006 |Soyuz TMA-7 |style="text-align: correct"|~182 |- !Expedition 13 |Pavel Vinogradov - Russia
Dmitri Kondratyiev - Russia
Daniel Tani - U.S.A. |colspan="Five" style="text-align: center"|Scheduled April–October 2006 |- !Expedition 14 |Jeffery Williams - U.S.A.
Clayton Anderson - U.S.A.
Aleksandr Lazutkin - Russia |colspan="Quintuplet" style="text-align: center"|Scheduled for October 2006–March 2007 |- !Expedition 15 |Fyodor Yurchikin - Russia
Oleg Kotov - Russia
John Grunsfeld - U.S.A
|colspan="Cinque" style="text-align: center"|Scheduled for March–September 2007 |}

The International Space Station is the most-visited spacecraft in the history of space flight. As of August 28, 2005, it has had 141 (non-distinct) visitors. Mir had 137 (non-distinct) visitors (See Space station).