Delays in producing space shuttle fuel tanks, which were substantially redesigned after the 2003 Columbia disaster, will postpone NASA's final servicing mission to the Hubble Space Telescope by a month or longer, space agency officials said on Thursday.
Originally due to launch on 28 August, the space shuttle flight to the telescope will be postponed four to five weeks, shuttle programme manager John Shannon said.
To fly to Hubble, NASA decided it needed a second shuttle ready to launch in case the ship carrying the crew became too damaged to return home.
Other missions don't require a backup shuttle because stranded astronauts can take shelter in the International Space Station. The orbital outpost will be too far away for the Hubble crew to reach, however.
Needing two tanks ready for launch strained the manufacturing process, Shannon said, adding that it took time for the agency's contractors to learn new assembly procedures following the 2003 Columbia accident.
A piece of insulation foam that fell off Columbia's fuel tank during launch hit a heat panel on its wing, damaging it and allowing superheated gases to flow inside the structure during atmospheric re-entry.
NASA redesigned the tank to minimise foam shedding, added in-flight inspections, developed repair kits and set up the space station as a safe haven for shuttle crewmembers.
Shannon said a lot of care had gone into the preparation of fuel tanks since, and it was not a job NASA wanted its contractors to rush.
"I think it's a small price to pay for all the improvement that we're getting on this tank," he added. "It's a much, much better tank than we were flying pre-Columbia. It just took a little extra time."
NASA plans to fly 11 shuttle missions before the fleet is permanently retired in 2010.
All but the Hubble repair mission are devoted to completing the $100 billion space station. The agency's next flight, scheduled for 31 May, will deliver the main part of Japan's huge Kibo space laboratory to the station.
The tank delays will also force NASA to delay a sixth mission the agency had hoped to fly in 2008 to early 2009.
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