Fuel Tank Rework Affects Future Flights

Delays in production to the last several, redesigned external fuel tanks slated to fly in the space shuttle program have forced NASA to move off a mission to service the Hubble Space Telescope.

According to The Associated Press, NASA will delay the mission, originally slated for late August 2008, by at least one month. Atlantis and a crew of seven will take flight at the end of September at the earliest, said Shuttle program manager John Shannon.

"It's a small price to pay to tell you the truth, four to five weeks, for all the improvements that we're getting on this tank," he said.

As ANN reported in March, the upcoming STS-124 mission onboard Discovery, scheduled to lift off later this month, will be the first launch to utilize an "in-line" external tank, which sports built-in modifications intended to reduce the risks of catastrophic damage to the orbiter from chunks of insulating foam.

Previous tanks used since Discovery's first Return to Flight mission in July 2005, following the 2003 loss of Columbia, featured a number of modifications intended to reduce foam shedding... but STS-124 will be the first to use an external tank designed from the ground-up to incorporate such changes. The new design includes a new protuberance air load (PAL) ramp design, and titanium O2 line support brackets... both measures intended to resist ice formation.

Tanks slated for subsequent missions have suffered from slowdowns in manufacturing, however, as workers address new tank construction processes, and other issues related to shuttle modifications. NASA will likely receive the external tank for the Hubble mission, STS-125, in time to make the August 28 launch date... but due to the unique nature of the Hubble servicing mission, the space agency has also called for the shuttle Endeavour to be launch-ready as well, should Atlantis suffer damage that would prevent the orbiter from reentering the atmosphere.

The tank slated for that emergency mission -- designated STS-400 -- won't be available in time for the August launch date, hence the delay.

STS-125 will be the first shuttle mission not to dock at the ISS since the Columbia disaster, and is slated to be the last such flight before the shuttle fleet is retired in September 2010. The Hubble is in a much higher orbit than the ISS, and the shuttle does not carry enough fuel to move to a different orbit to dock with the station and "lifeboat" the crew.

FMI: www.nasa.gov