The final launch of the space shuttle Discovery has been delayed until at least December 3 so that repairs can be carried out on a hydrogen leak, the US space agency said Thursday.
NASA said it would review the required analysis and repairs over the next five days and hoped to hold a decisive meeting on the launch on Monday, November 29.
"The Kennedy Space Center 'Call-to-Stations' to begin the launch countdown will be no earlier than Nov. 30, supporting a first launch attempt no earlier than Dec. 3," it said in a statement.
Inspectors this week found a fourth crack in support beams on the external fuel tanks of the space shuttle.
The latest crack was found when technicians removed foam while inspecting the support beams, which are called stringers, in the aftermath of the hydrogen leak, the space agency said.
Two nine-inch (21-centimeter) cracks were found in an adjacent support beam last Friday, and a three-inch (7.5 centimeter) fissure was uncovered over the weekend.
To get in a flight to the International Space Station this year, Discovery must blast off before December 6. Otherwise it will have to wait until February, the same month that the last-ever shuttle launch is scheduled before the fleet is mothballed for good.
Discovery's 11-day mission with its all-American crew of six is to deliver a pressurized logistics module called Leonardo to the ISS, which will be permanently attached to the space station to provide more storage space.
The shuttle will also bring Robonaut 2, the first human-like robot in space and a permanent addition to the orbiting space station, as well as spare parts.
Two space walks, for maintenance work and component installation, are scheduled.
The Discovery has launched into space 38 times, and NASA aims to retire the shuttle after its final and 39th voyage.
The launch aims to be the fourth and final shuttle flight of the year, and the last scheduled for Discovery, the oldest in the three-shuttle fleet that is being retired next year.
But the mission has been marred by a series of delays brought on by bad weather and equipment problems.
The three US shuttles -- the other two are Atlantis and Endeavour -- are due to be sent off to become museum pieces after a final shuttle mission to the space station in late February.
That means Russian Soyuz spacecraft, a modernized version of which recently dropped off three fresh crew members to the ISS, doubling the crew to six, will for several years be the only vehicle for transporting humans into space.
However, NASA's recently approved 2011 budget has left the door open to an additional shuttle flight in June.
Explore further: Leaks delay final launch of space shuttle Discovery