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
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.