NASA Now Aiming for Dec. 3 Launch of Space Shuttle Discovery

This story was updated at 4:56 p.m. ET.

NASA is now aiming for a Dec. 3 launch for the space shuttle Discovery's final voyage, after a month of delays, malfunctions and subsequent repairs.

If all goes well, Discovery should be ready to launch on Dec. 3 at 2:52 a.m. EST (0752 GMT), NASA officials said in an update. A series of safety reviews is still ahead before the shuttle is completely cleared for flight, they added.

Discovery has been stuck on Earth since Nov. 5, when a potentially dangerous hydrogen gas leak on the shuttle's external tank forced NASA to stand down for repairs.  Foul weather and other glitches thwarted several earlier launch attempts that week.

Since then, NASA engineers have replaced a misaligned seal to plug the hydrogen leak and are now working to reinforce metal ribs on the external tank where cracks were discovered while the leak repairs were being performed.

The cracks are on two of 108 metal ribs around the upper middle portion of the tank that provide structural support. There are two cracks on each of the ribs. NASA shuttle technicians are installing double-wide ribs ? called doublers ? to reinforce the cracked areas. [INFOGRAPHIC: NASA's Space Shuttle ? From Top to Bottom]

Another crack, this one in the exterior foam insulation on Discovery's fuel tank, will also be repaired.

While the fuel tank rib repairs are under way, NASA shuttle program managers plan to review their rationale for flying Discovery with the repairs. If during that meeting, slated for Nov. 24, shuttle officials agree that Discovery is ready to fly, the space agency will hold a final review on Nov. 29 to clear the shuttle for liftoff, NASA officials said.

NASA's upcoming STS-133 shuttle mission will be the final flight of shuttle Discovery before it is retired along with the rest of the U.S. orbiter fleet in 2011.

The 11-day mission will send a crew of six astronauts to the International Space Station to deliver a storage room for the orbiting lab, as well as a humanoid robot built designed to help astronauts with work in space. Two spacewalks are planned.

NASA's upcoming 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 space station after that, agency officials have said. NASA's shuttle Endeavour is scheduled to fly to the station during the next available window, which opens in late February.

NASA is retiring the space shuttle fleet to make way for a new plan aimed at sending astronauts to visit an asteroid by 2025. After Discovery's flight, NASA has only one more mission ? Endeavour's ? scheduled before the fleet is retired.

The agency hopes to gain final funding approval for a third shuttle mission, which would fly no earlier than June 2011. Congress and President Obama have authorized that extra shuttle mission, but the measure must still pass an appropriations review.

Once the shuttle fleet is retired, the space agency plans to rely on Russian, European and Japanese spacecraft to ferry crews and cargo to the space station until 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