Holes in foam insulation are the latest setback to aging orbiter's final mission.
NASA engineers on Wednesday detected cracks in the foam insulation that lines space shuttle Discovery's fuel tanks—a development that places the problem-plagued craft's latest and last launch schedule in doubt.
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Space Shuttle Discovery
The space agency said it believes the cracks occurred during draining operations that followed a decision to scrub a launch scheduled for Nov. 5.
NASA scrubbed the liftoff after a leak in Discovery's hydrogen system was detected. Friday's cancellation was the third time in less than a week that Discovery's final mission was aborted due to mechanical or weather problems.
NASA has said it now hopes to send Discovery to the International Space Station for the final time on Nov. 30.
Discovery is the oldest shuttle in NASA's fleet. It entered service in 1984, and is one of three remaining shuttles of the six originally built. Atlantis and Endeavour also remain operational, while Challenger and Columbia were lost in accidents that claimed the lives of their crewmembers.
The first shuttle, Enterprise, was a test vehicle that was retired shortly after its initial series of suborbital flights in 1977.
The shuttle program is expected to end in February when Endeavour takes to the skies for the final time. President Obama earlier this year ordered NASA to turn over low-orbit flights to private contractors and focus more on deep space missions and research.
Critics of the plan claim it will cost jobs along Florida's Spacecoast and in other states that support the shuttle program. They also say it could leave the U.S. lagging behind Russia and China in the space race.
Discovery will carry a six-member, all-U.S. crew on its final voyage, officially known as STS-133. The team is led by Commander Steve Lindsey, 50, of Temple City, Calif., and pilot Eric Boe, 45, of Atlanta. Also on board will be mission specialists Alvin Drew, 47, of Washington, D.C., Tim Kopra, 47, of Austin, Texas, Michael Barratt, 51, of Camas, Wash., and Nicole Stott, 47, of Clearwater, Fla.
Upon achieving orbit, Discovery will execute a series of positioning maneuvers prior to docking with the ISS, where the crew will drop off various parts and supplies.
Mission specialists Drew and Kopra will undertake a pair of six-hour spacewalks during the mission. Stott, meanwhile, plans to broadcast regular mission updates through her Twitter account, @Astro_Nicole. NASA, through its Web site, is also giving the public the chance to help select the songs that will serve as wakeup calls for the Discovery crew during their mission.