Redesign of the shuttle with reliability in mind after the Challenger disaster reduced maximum payload to low earth orbit from 27,850 kg to 24,400 kg. When the decision was made to move the International Space Station to a high-inclination 51.6 degree orbit, net payload to the more challenging orbit dropped to unacceptable limits. The situation was improved by introduction of the Super Lightweight External Tank, which used 2195 Aluminium-Lithium alloy as the main structural material in place of the 2219 aluminium alloy of the original design. This saved 3,500 kg in empty mass, increasing shuttle payload by the same amount. The tank was first used on STS-91 in June 1998.

LEO Payload: 27,500 kg. to: 204 km Orbit. at: 28.5 degrees. Payload: 16,050 kg. to a: space station orbit, 407 km, 51.6 deg inclination trajectory. Liftoff Thrust: 2,875,000 kgf. Total Mass: 2,040,000 kg. Core Diameter: 8.7 m. Total Length: 56.0 m.

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• 44 - Jenkins, Dennis R,, Space Shuttle: The History of Developing the National Space Transportation System, Motorbooks International, ISBN 0-9633974-4-3, 1996.
• 455 - Isakowitz, Steven J,, International Reference to Space Launch Systems Third Edition, AIAA, Washington DC, 2000.