After months of testing, engineers at NASA's Marshall Space Flight Center and Boeing in Huntsville, Ala., say the first "backbone" segment of the International Space Station is flight-ready. On October 5, the starboard-side "S1" truss leaves Marshall on the next leg of its long journey into space history.

The spine-like truss will be carried aboard NASA's Super Guppy aircraft from Redstone Army Airfield to Kennedy Space Center, Fla. Primarily constructed of aluminum, the S1 truss is 45 feet long, 15 feet wide and 6 feet tall.

When fully outfitted, it will weigh 31,137 pounds. Manufactured by the Boeing Co. in Huntington Beach, Calif., the truss has been at Marshall since February 1999 for installation of critical flight hardware and structural and dynamic testing.

In October 2000, the Space Shuttle will carry the S1 truss to orbit for deployment and installation on the Space Station.

Once assembled in orbit, the complete truss will stretch the length of a football field, providing the foundation for the Station's solar power array, subsystem hardware and external experiment positions.

The International Space Station is a cooperative endeavor by the United States and 15 other nations — the largest multinational space construction effort in history. Orbital assembly is expected to be complete in 2004.

The Marshall Center is one of the primary NASA centers for Space Station construction and flight-testing. Boeing built the Unity node — the first U.S. component carried to orbit — at Marshall, as well as the Destiny laboratory module, scheduled for transport to space in April 2000.

Marshall is also developing the Space Station's Environmental Control and Life Support System — critical to the on-board recycling of air and water supplies — and is overseeing construction of experiment racks and various flight systems. Marshall is responsible for environmental, structural and dynamic testing of various Space Station components.