NASA's second redesigned Space Shuttle External Tank, designated for use on Atlantis' Return to Flight mission STS-121, is now in place at NASA's Kennedy Space Center, Florida.

The barge carrying the STS-121 tank arrives at the Cape. Credit: NASA

Following a 900-mile journey at sea from the Michoud Assembly Facility in New Orleans by NASA's Solid Rocket Booster Retrieval Ship Freedom Star, the External Tank was off-loaded from the barge and transported to the Vehicle Assembly Building.

In response to the Columbia Accident Investigation Board's recommendation, the new tank incorporates several safety improvements, including an improved bipod fitting that connects the tank to the orbiter. In addition, NASA's second redesigned tank has been outfitted with temperature sensors and accelerometers, used to measure vibration. These sensors will gather information about how the tank performs during flight.

In the VAB, the tank will be raised this week from a horizontal to a vertical position, then lifted high into a storage cell, or "checkout cell," where it undergoes inspections of the mechanical, electrical and thermal protection systems. New processing activities resulting from redesign of the tank include inspection of the bipod heater and External Tank separation camera.

When tank preparations are complete, it will be attached to Atlantis' Solid Rocket Boosters, on the Mobile Launch Platform.

STS-121 is NASA's second Return to Flight mission, carrying a seven-member crew to the International Space Station during a launch planning window of July 12 through July 31.