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How the International Space Station Works

Parts and Assembly of the ISS
The Japanese Kibo complex of the ISS and the space shuttle Atlantis docked to the station
The Japanese Kibo complex of the ISS and the space shuttle Atlantis docked to the station
Image courtesy of NASA

Building the International Space Station (ISS) is much like building a toy using a child's LEGO or K'nex building block set. There are more than 100 parts to the ISS and all of those parts are linked together. The parts can be categorized as follows:

  • Pressurized modules -- such as the Zarya, Zveda, Destiny, Columbus and Harmony -- provide breathable, warm environments for living quarters, equipment rooms and laboratories where the crews live and work.
  • Nodes link modules together and allow branching of the ISS structure.
  • Docking ports allow various space vehicles to attach to the ISS.
  • A long, linear truss lies above the pressurized modules, forming a girder framework where the solar panels and radiators attach. A mobile, robotic, servicing arm moves along the truss to haul cargo and experiment packages.
  • External Research Accommodations provide multiple mounting locations along the outside of the ISS for experiments that rely on full exposure to the space environment.
  • Spacecraft -- such as the Soyuz spacecraft and Progress supply ship -- dock with the ISS to transport astronauts and supplies to and from Earth.

Assembly of the ISS began in November of 1998 when a Russian proton rocket placed the first module, the Functional Cargo Block (Zarya), in orbit. A three-member crew, the ISS's first, was launched from Russia on October 31, 2000. The crew spent almost five months aboard the ISS, activating systems and conducting experiments. Since then, many spacecraft have delivered parts of the ISS into orbit and its assembly has progressed. During this time, the ISS has been manned continuously with 26 crews of astronauts (as of this writing). The astronauts have spent a cumulative total of 4,423 days in outer space. The current crew, Expedition 26, will spend 5 months in space and return to Earth in May 2011, and then Expedition 27 will begin.

With a scheduled completion date set for December 2011, there are seven remaining scheduled flights in 2011 to complete its construction. There will be three flights by Russian and European rockets to deliver supplies, two space shuttle flights and one Russian proton rocket will deliver large pieces of modules or equipment and the shuttle flight in April will change crews.

When completed, the ISS will be 243 ft (74m) long and 361 ft (110 m) wide. It will have a mass of 925,000 lbs (420 metric tons) and a pressurized volume of 33,023 ft3 (935 m3); the pressurized volume will be about the cabin size of a 747 jet. It will be in orbit at 217 to 285 miles (362 to 476 km), inclined 51.6 degrees relative to the equator [source: ISS Facts and Figures and NASA ISS Reference guide].

Those are some pretty impressive specs -- but perhaps even more impressive is how the ISS maintains a livable environment.

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