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STS 91



STS 91 was an American Shuttle spacecraft launched from Cape Canaveral. The main mission was to dock with and deliver goods to the Mir space station. It also carried the 3.5 ton international Alpha Magnetic Spectrometer to measure very high energy cosmic rays, and some resources for microgravity experiments. It docked with Mir on June 4 at 20:58 UT, undocked on June 8 at 16:02 UT and returned to Earth on June 12 at 18:00 UT.

This mission was the first to use of the super lightweight external tank (SLWT) which is the same size (154ft long and 27ft in diameter) as the external tank used on previous launches but 7,500 lbs lighter. The tank is made of an aluminum lithium alloy and the tank's structural design also has been improved making it 30% stronger and 5% less dense. The walls of the redesigned hydrogen tank are machined in an orthogonal waffle-like pattern, providing more strength and stability than the previous design. These improvements will provide additional payload capacity to the International Space Station.

Alternate Names

  • 25356
  • STS91

Facts in Brief

Launch Date: 1998-06-02
Launch Vehicle: Shuttle
Launch Site: Cape Canaveral, United States

Funding Agency

  • NASA-Office of Space Flight (United States)


  • Human Crew
  • Microgravity

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office

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