Wednesday, November 24, 2010
NASA has pushed back the target launch date of space shuttle Discovery by two weeks due to the need for more tests on the cracked section of her external fuel tank.
Four cracks were discovered on the inter tank region where the top section of the rocket boosters attach following a launch scrub on November 5.
Once the launch team drained the super cold fuels from the two tanks located inside the external tank, one crack was found followed by three more over the next day.
The inner tank region has a total of eight panels around the diameter, including and two 2-inch thick aluminum panels at the section where the forward SRB's attach.
Cracks located on two 21-foot long aluminum brackets known as stringers are being repaired.
NASA wants to learn if there are more stress cracks around the diameter of the tank.
Discovery's rust colored fuel tank is loaded with 535,000 gallons of super cold liquid hydrogen and liquid oxygen on launch day. The fuels mix to power the orbiter's three main engines during the first eight minutes of launch.
Launch is now targeted for no earlier than December 17 at 8:51 pm EST, however due to the need for extensive tests over the coming week, a more firm launch time could move the space mission to early January or February.
NASA states that Dec. 17 is a target only date and the team is not pressured by delays now or in the future.
Technicians at the Kennedy Space Center will take Thanksgiving and Friday off before picking up testing again on Saturday. X-ray tests of several regions of the ribbed portion of the tank will be performed.
Technicians "using two forms of imagers are examining the stringers that make up the ribbed intertank section", NASA's Steven Siceloff stated recently at Kennedy.
"There are 108 of the 21-foot-long metal stringers that connect the cone-shaped liquid oxygen tank on top with the oblong liquid hydrogen tank on the bottom," Siceloff added.
The technicians need to use scanners to visually see down through the insulation covering the aluminum structure of the tank for further evidence of more cracks.
Siceloff went on to say that "the scans are reviewed by officials at NASA's Marshall Space Flight Center in Alabama where the tank was designed, and at NASA's Michoud Assembly Facility outside New Orleans where the tank was built."
The next mission management team meeting is planned for December 3 in the hopes of learning where the space agency is in making necessary repairs and learning from the tests performed.
NASA managers state that there are several unknowns related to the tank's stress cracks.