Agency Also Dropping Some Tile Replacement Methods

A troublesome "ramp" of insulating foam will likely be left off the external fuel tank on future shuttle missions. The ramp was one of five areas where foam unexpectedly broke off during the launch of Discovery last July, causing some tense moments for the agency during the first flight since the Columbia disaster.

As was reported in Aero-News, NASA isolated cracks in the protuberance airload -- or PAL -- ramp as the likely culprit of foam breakage on Discovery back in October, although at the time the agency was unsure whether or not the removal of the ramp would expose the hardware it protected to dangerous aerodynamic forces. However, according to NASA's Director of Space Operations William H. Gerstenmaier, the lesser risk is to leave the ramp off.

"The best thing to do is to just take it off," said Gerstenmaier to The New York Times.

To save money, NASA is also dropping its research into methods of repairing the shuttles' thermal tiles in flight. The methods duplicate other approaches that accomplish the same goals, according to Gerstenmaier.

As far as the PAL ramp, Gerstenmaier said in the time since the shuttle was originally designed in the 1970s, the pressurized fuel lines, cable box and other fixtures protected by the ramp have been strengthened. While the agency plans on continued testing, wind-tunnel testing and computer models conducted thus far support the hypothesis the PAL ramp is no longer needed.

The other four areas of the redesigned tank that experienced foam breakage during Discovery's launch have been linked to causes other than cracks, and have been addressed by other solutions, said Gerstenmaier.

Contrary to previous reports, the NASA director told the Times any modifications necessary to the fuel tank could be made in time for the scheduled May 2006 launch of the second Return to Flight mission, which will also be flown by Discovery.

Earlier NASA reports had indicated removal of the PAL ramp would delay the mission until the end of 2006 -- although Gerstenmaier stressed a Spring '06 mission is not needed to meet NASA's goal of completing 19 shuttle missions before the expected end of the shuttle program in 2010.

"We don't need to have a flight this spring to make the 19 flights," Mr. Gerstenmaier said.

Sister ships Atlantis and Endeavour are being prepped for later missions of their own, although launch dates will not be determined until Discovery's flight is confirmed. Under NASA's plan, 18 missions will be flown to complete the ISS and one mission will be mounted to repair the venerable Hubble Space Telescope.

FMI: www.nasa.gov