| || || || || || |
Fixing Discovery's fuel tank
The repair work on Discovery's tank, which is being conducted in the cavernous Vehicle Assembly Building, is expected to take about a week, NASA officials said.
Additional scans will be performed using a backscatter device, which bounces radiation off the tank and allows engineers to see beneath the layer of foam insulation. Technicians at various NASA centers will analyze the resulting data.
The beams are located at the "intertank" region of Discovery's 15-story-tall external tank. That region serves as a structural bridge between the tank's liquid hydrogen and liquid oxygen propellant sections, and is the upper connection point for the shuttle's twin solid rocket boosters. [Infographic: NASA's Space Shuttles: Top to Bottom]
Working on the cracks
Meanwhile, repairs to four small cracks on the tops of three of the tank's metal ribs, which had been detected Dec. 29, were expected to be completed this week. Repairs began Monday (Jan. 3) for these fractures, located on the back side of the tank's midsection, opposite from Discovery.
The repairs are similar to those made to other cracks that were found on the tank's support beams following Discovery's scrubbed launch attempt Nov. 5.
Discovery's STS-133 mission has been delayed since then as engineers work to understand how and why the cracks developed. Discovery is now slated to launch on its final mission to the International Space Station no earlier than Feb. 3, with the launch window extending through Feb. 10.
On Discovery's 39th and final flight, the shuttle will deliver critical supplies, a storage room and a humanoid robot to the space station.
NASA is retiring its space shuttle fleet this year to make way for a new space exploration plan aimed at sending astronauts to an asteroid by 2025 and, in a later expedition, to Mars.
The shuttle Endeavour is set to fly its final mission, also to the space station, in April. NASA has gotten permission to fly a third mission to the station in 2011, around June using the shuttle Atlantis, before retiring the fleet for good.