NASA managers made the decision on Monday afternoon that space shuttle Discovery will be rolled back from the launchpad for inspections and/or repairs. There’s no word from NASA yet on the reason for the decision, but presumably it has to do with the cracks on the “stringers,” or structural ribs of the shuttle’s external tank. A tanking test was scheduled for today (Monday), but cold weather has delayed the test to no earlier than Dec. 17. According to reports on Twitter, the rollback will be done about five days after the tanking test.
The reason for the tanking test delay is that the sensors used to test the external tank won’t bond to the sides of the tank if temperatures are too low, and the current frigid conditions aren’t even close to being warm enough.
Additional word is that the shuttle is hoped to be returned to the launchpad by the middle of January in order to be ready for an anticipated launch in February. But that all depends on the nature of the work NASA engineers determine needs to be done. Since production of external tanks is now finished at the assembly facility in Louisiana, it would take at least two years — and probably more — for a new tank to be built.
More details have now emerged on the reasons for sending Discovery back to the Vehicle Assembly Building:
There, the engineers have better tools and better access to put the external tank through additional image scans. Once in the VAB, technicians would collect X-ray data on stringers on the back side of the external tank midsection, called the intertank, which is not accessible at the launch pad.
Additionally, the test instrumentation and foam insulation on those areas of the intertank would be removed and the area would be prepped again for launch.