NASA has extended to September 2008 its six-year, $1.15 billion contract with Lockheed Martin Space Systems, New Orleans, to provide 35 Super Lightweight External Tanks for the Space Shuttle Program.

External tank arrives at Kennedy Space Center for launch. Photo: NASA

Under the modified contract, the 35 tanks will be produced at a rate of not less than six per year, versus the eight per year agreed upon in the original contract issued in October 2000. The modification adds $341 million to the contract.

The contract includes the manufacture, assembly, test and delivery of the Super Lightweight Tanks and the operations and maintenance of NASA's Michoud Assembly Facility in New Orleans. The contract also includes activities at NASA's Marshall Space Flight Center, Huntsville, Ala., and Kennedy Space Center, Fla. This is the sixth contract for production of tanks and the first to be comprised totally of Super Lightweight Tanks.

This latest version of the tank, which flew for the first time in June 1998, is the same size as the tank it replaces, but is about 7,500 pounds (3,401.9 kilograms) lighter. Since the tank goes almost to orbit, every pound of weight saved is equivalent to a pound of increased payload. The weight reduction allows the Space Shuttle to carry more payload.

The Super Lightweight Tank features major changes in materials and design. Its liquid hydrogen tank and the liquid oxygen tank are constructed of a new aluminum lithium, a lighter, stronger material than the metal alloy used to manufacture previous External Tanks.

The External Tank, which holds the liquid hydrogen fuel and liquid oxygen for the Shuttle's three main engines, is the largest single component of the Space Shuttle and the only part of the Shuttle that is not reused. Standing 154 feet tall (approximately 50 meters), the gigantic rust-colored tank is taller than a 15-story building and as wide as a silo, with a diameter of about 27.5 feet (approximately 8 meters).

During launch, the tank also acts as the structural backbone for the Shuttle orbiter and Solid Rocket Boosters attached to it. The first tank of the sixth production is scheduled for delivery to the Kennedy Space Center this year. Marshall is NASA's key leader for development of space transportation and propulsion systems.