The International Space Station (ISS) is the most complex international aerospace project in history. Sixteen countries contribute to this massive structure that measures 360 ft (110m) wide and 289 ft (88 m) long. At Earth's surface gravity, the ISS would weigh 503 tons (456,620 kg). Constructed from specialized component modules, the ISS is designed to allow humans to live in space for long durations of time and provide a laboratory for both scientific and engineering experiments. The modular design allows sections to be completed and tested on Earth before being booted into orbit. In addition, the modular design provides a level of security to ISS personnel. Damage from a failure or rupture of a component module can be isolated and the crew evacuated to safe modules. Modular designs are also economical because they allow rapid adaptation to the station to specific uses without having to subject the station to extensive retrofitting. In a engineering sense, the modular design allows maximum safety, design flexibility, and use adaptation at the lowest cost.
Long-range plans include use of the ISS as a spaceport where spacecraft can dock to transfer people, cargo, and fuel without having to re-enter Earth's atmosphere. Use of the ISS as a spaceport would thus, facilitate the construction of a fleet of true space vehicles—craft designed to operate exclusively outside Earth's atmosphere. Such craft would not need to be constructed to withstand the dynamic pressures of reentry, nor would their engine systems need to be designed to provide thrust capable of propelling the craft to high escape velocities.
Although the United States and Russia shoulder the bulk of the technological burden of ISS design and orbital placement, other nations, including Canada, Japan, the 11 nations of the European Space Agency (ESA) and Brazil significantly contribute to ISS development.
The United States is responsible for constructing and operating major ISS elements and systems. The U.S. systems include thermal control, life support, guidance, navigation and control, data handling, power systems, communications and tracking, ground operations facilities, and launch-site processing facilities. Canada is providing a 55-foot-long (16.8 m) robotic arm to be used for the station's assembly and maintenance. The European Space Agency is contributing a pressurized laboratory to be launched on the Space Shuttle, and logistics transport vehicles to be launched on an ESA Ariane 5 launch vehicle. Japan is providing a laboratory to be used for experiments and logistics transport vehicles. Russia is contributing two research modules, the Service Module, which includes early living quarters with life support and habitation systems, a science power platform that can supply 20 kilo-watts of electrical power, logistics transport vehicles, and Soyuz spacecraft for crew drop off and pick up. Through agreement with the United States, Italy, and Brazil are also providing ISS components and laboratory research facilities.
Approved by President Ronald Reagan in 1984, ISS (then designated Space Station Freedom) development was put on hold by the turmoil and collapse of the Soviet Union in the late 1980s and the subsequent emergence of a revitalized Russian Space Agency in 1993. Broadened in scope to include a true international collaboration, in November of 1998, Russia launched the first part of the developing space station. More than four times as large as the Russian Mir space station, ISS assembly will continue until at least 2004.
ISS orbits at an altitude of 250 statute miles with an inclination of 51.6 degrees. This orbit allows maximum accessibility to the station for docking, crew rotation, and supply delivery. The orbit also allows for excellent observation of Earth. Orbital dynamics allow observation of up to 85% of Earth's surface and overflight of approximately 95% of Earth's heavily populated areas. Accordingly, the ISS is an ideal platform for the study of dynamic Earth geophysical processes and the long term study of the effects human civilization has upon both the physical and ecological landscape.
In addition to astronomical and Earth science research groups, the ISS will support medical and industrial research (e.g., the formation of certain alloys and crystals in low gravity environments).
