Thisstory was updated at 4:56 p.m. ET.
NASAis now aiming for a Dec. 3 launch for the space shuttle Discovery's finalvoyage, after a month of delays, malfunctions and subsequent repairs.
Ifall goes well, Discoveryshould be ready to launch on Dec. 3 at 2:52 a.m. EST (0752 GMT), NASA officialssaid in an update. A series of safety reviews is still ahead before the shuttleis completely cleared for flight, they added.
Discoveryhas been stuck on Earth since Nov. 5, when a potentially dangerous hydrogen gasleak on the shuttle's external tank forced NASA to stand down for repairs. Foul weather and other glitches thwarted several earlier launch attemptsthat week.
Sincethen, NASA engineers have replaced a misaligned seal to plug the hydrogen leakand are now working to reinforce metal ribs on the external tank where crackswere discovered while the leak repairs were being performed.
Thecracks are on two of 108 metal ribs around the upper middle portion of the tankthat provide structural support. There are two cracks on each of the ribs. NASAshuttle technicians are installing double-wide ribs ? called doublers ? toreinforce the cracked areas. [INFOGRAPHIC:NASA's Space Shuttle ? From Top to Bottom]
Anothercrack, this one in the exterior foam insulation on Discovery's fuel tank, willalso be repaired.
Whilethe fuel tank rib repairs are under way, NASA shuttle program managers plan toreview their rationale for flying Discovery with the repairs. If during thatmeeting, slated for Nov. 24, shuttle officials agree that Discovery is ready tofly, the space agency will hold a final review on Nov. 29 to clear the shuttlefor liftoff, NASA officials said.
NASA'supcoming STS-133 shuttle mission will be the finalflight of shuttle Discovery before it is retired along with the rest of theU.S. orbiter fleet in 2011.
The11-day mission will send a crew of six astronauts to the International SpaceStation to deliver a storage room for the orbiting lab, as well as a humanoidrobot built designed to help astronauts with work in space. Two spacewalks areplanned.
NASA'supcoming window to launch Discovery opens on Nov. 30 and will close around Dec.6 to avoid heating concerns caused by unfavorable sun angles at the spacestation after that, agency officials have said. NASA's shuttle Endeavour isscheduled to fly to the station during the next available window, which opensin late February.
NASAis retiringthe space shuttle fleet to make way for a new plan aimed at sendingastronauts to visit an asteroid by 2025. After Discovery's flight, NASA has onlyone more mission ? Endeavour's ? scheduled before the fleet is retired.
Theagency hopes to gain final funding approval for a third shuttle mission, whichwould fly no earlier than June 2011. Congress and President Obama haveauthorized that extra shuttle mission, but the measure must still pass anappropriations review.
Oncethe shuttle fleet is retired, the space agency plans to rely on Russian,European and Japanese spacecraft to ferry crews and cargo to the space stationuntil American commercial spacecraft are available to do the job.
- Gallery: Building Space Shuttle Discovery
- Video ? Space Shuttle Discovery: A Retrospective, Part 2, Part 3
- Space Shuttle Discovery's Retirement Plan in Limbo
