International Space Station
History And Structure
The ISS was originally proposed by U.S. President Ronald Reagan in 1984, and was slated to cost $8 billion. Thirty-six U.S. shuttle flights plus nine Russian rocket launches will be required for ISS construction. Today there are 15 major partners in the ISS effort, including the United States, Russia, Japan, Canada, and 11 of the member states of the European Space Agency. The United States, through its National Aeronautics and Space Administration (NASA), is the largest single contributor, bearing approximately $25 billion of the total $50–100 billion cost of building, launching, and operating ISS for at least a decade.
Assembly of the ISS commenced in 1998 with launch of the Russian control module Zarya on a proton rocket from Kazahkstan. The U.S. module Unity Node, a connecting segment, was carried into space on the shuttle Endeavor later in 1998. This unit is primarily a docking hub to which other sections join. In 2000, another Proton rocket lofted the Russian service module Zvezda, the main Russian contribution to the ISS. Zvezda provided living quarters and life support during the early phases of the ISS's growth; it also provides steering rockets to control the ISS's attitude (orientation in space) and to reboost it to higher altitudes as its orbit decays due to friction with high-altitude traces of the earth's atmosphere.
The ISS is powered by photovoltaic electricity. The first of its four large solar arrays (112 by 39 ft [34.2 by 11.9 m]) was added in 2000. When completed, the ISS will receive about 260 kilowatts of power (peak) from an acre of sun-tracking solar panels. An energy-storage sub-system consisting of six large nickel-hydrogen (Ni-H2) batteries supplies electrical power to the ISS during its passage through the earth's shadow, which lasts about 45 out of every 90 minutes.
In 2001, the U.S. laboratory module Destiny, the largest and most elaborate of the ISS's components, was added using the robot arm of the space shuttle Atlantis. The U.S. lab module contains 13 equipment racks, on which various scientific experiments will be mounted, and a 20-in (0.5-m) window set in the Earthside wall.
Smaller components were added piecemeal in 2002 by several shuttle flights, and in 2001–2002 several Russian flights ferried passengers and supplies. The ISS's final configuration will contain a European laboratory module, a Japanese laboratory module, three Russian laboratory modules, a Canadian robot arm to assist in assembly and maintenance, exterior racks for experiments requiring direct exposure to space, and an emergency Crew Return Vehicle on standby. The shuttle has been continuously inhabited since November 2, 2000, and presently houses a full crew of seven.