Current Modifications Proving Sturdy

Saying the current design of the space shuttle's external fuel tank "has proven to be more robust" than first thought, managers at NASA have decided to put off redesigning the problematic component until 2008.

NASA already revised several components of the external tank in the wake of the February 2003 loss of the shuttle Columbia. That accident was caused by insulating foam that broke off the tank, and damaged the shuttle's ceramic-tile heat shield.

More changes have been made to each tank that has flown on shuttle launches since July 2005, building on the lessons learned from the mission before it -- most notably, the removal of an aerodynamic load ramp that was the source of significant foam breakage. Engineers also refined the process of applying to the tank, to prevent the situation that doomed Columbia.

It seems to have worked. NASA says that in each of the three shuttle flights that followed Columbia, foam breakage has been lessened greatly -- and any pieces that have broken off did so late enough in the launch to not pose a significant threat.

Engineers have been working on a more thorough redesign of the tank, however, incorporating changes to the attachment points that mate the tank with the orbiter.

NASA spokesman Kyle Herring said the new tank will use titanium mounting brackets, for example, instead of the current aluminum units. Titanium handles extremes in temperature far better than the current steel assemblies... and thus will require less foam to be applied. The new tank was originally to go online sometime in 2007.

"It just gives you some added confidence and less risk," Herring said of the new design.

But the current tank has proven to be surprisingly sturdy... so NASA plans to have the redesign ready in early 2008, in time for a planned shuttle mission to the Hubble Space Telescope. That mission will require the shuttle to travel to a higher orbit than the current roster of missions to the International Space Station... and, thus, will need more fuel.

FMI: www.nasa.gov