Integrated Truss Structure
International Space Station assembly took a dramatic turn in late 1999 as a pre-integrated truss segment began sprouting from the top of U.S. Node 1 Unity
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Space Shuttle Discovery delivered truss segment "Z1" in October, 1999, signaling the beginning of work on the major elements that will make the Station more than a unique vision with a good start.
The first U.S. solar arrays were temporarily attached to Z1 a month later. They provide power for the initial work on assembly of the Integrated truss Structure -- the backbone of the ISS.
When it is completed, the truss will be the length of a football field, with its axis perpendicular to the Station's main axis. Its simple, girder-like appearance will mask its multiple ISS roles. With the launch of the P4 element, NASA will deploy a new External Wireless Instrumentation System (EWIS) (PDF) for the first time. The system consists of accelerometers placed around the outboard integrated truss structure to monitor the health of this complex truss structure.
Labs, living quarters, payloads and systems equipment will be directly or indirectly connected to it. U.S. solar arrays supplying 105 kW of ISS power -- enough to light a town -- will be attached to it.
Wires and cables will snake through the truss to carry energy and information to the Station's farthest reaches. Canada's Mobile Servicing System will move its 55-ft. robotic arm and hand along tracks attached to the truss. It also will house batteries, radiators, antennas and gyros.
Eight Space Shuttle missions will be required to deliver and assemble the Structure's ten pre-integrated truss segments. Assembly of the International Space Station resumes with delivery of the the Boeing built Port 3/Port 4 truss (PDF) on STS-115 mission in August 2006.