Apr. 30, 1999 NASA and Lockheed Martin Michoud Space Systems, of New Orleans, La., have completed negotiations on a contract worth $625.6 million for the final purchase of materials needed to build 60 new Space Shuttle external fuel tanks.
"Together, with two earlier purchases of materials and equipment, we now have everything we need to build our sixth production order of external tanks for the Space Shuttle Program," said Parker Counts, manager of the External Tank Project Office at NASA's Marshall Space Flight Center in Huntsville, Ala.
This sixth purchase of tanks will be the first comprised totally of Super Lightweight Tanks. This newest version of the tank is the same size as the previous Lightweight Tank design, but weighs approximately 7,500 pounds less. Its liquid hydrogen tank and the liquid oxygen tank are made of a new aluminum lithium alloy, a lighter - but 30 percent stronger - material than the previous aerospace aluminum alloy used for the Lightweight Tank.
The lighter tank allows the Shuttle to deliver various elements of the International Space Station - such as the Unity module launched last December - into the proper orbit.
NASA has purchased a total of 119 external tanks. To date, 93 have been flown. The last of the fifth production order is scheduled to be delivered in August 2001.
Production of the new order of tanks will start in 2000 at NASA's Michoud Assembly Facility in New Orleans, with the first one scheduled for delivery to the agency's Kennedy Space Center, Fla., in 2002.
"It takes about 20 to 22 months to build a tank once the purchased materials are received at the factory," Counts said. "The first tank of this new order will fly probably in 2002. This buy should carry the Shuttle program well into the next century."
"The Super Lightweight Tank has been a challenging tank to produce," Counts said. "But, as we expected, the initial cost to produce it has come down as our government/industry team gains experience and makes improvements to our manufacturing equipment and processes."
Measuring 154 feet tall and 27.5 feet in diameter, the external tank is the largest single element of the Space Shuttle. During launch, the tank also acts as the structural backbone for the Shuttle orbiter and solid rocket boosters attached to it.
The external tank holds the liquid hydrogen fuel and liquid oxygen oxidizer for the Shuttle's three main engines. The tank is the only part of the Shuttle not reused. After its 526,000 gallons of propellants are consumed during the first eight and one-half minutes of flight, it is jettisoned from the orbiter and breaks up in the upper atmosphere, its pieces falling into remote ocean waters.
The Super Lightweight Tank made its first flight in June 1998 on the STS-91 mission.
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