NASA managers announced Friday a further delay for Discovery’s final launch on mission STS-133, pending results of tanking tests to be conducted in an attempt to understand how exactly two 21′ vertical stringers on Discovery’s external fuel tank could have cracked during offloading of cryogenic fuel November 5th.
The new launch target date is now scheduled for no earlier than February 3rd, 2011 at 1:34 am EST.
Mission managers had hoped to attempt a launch during a window between December 17th and December 20th, but data and analysis collected thus far does not support a flight rationale for STS-133 at this time. Technicians want to understand why exactly the cracks occured, and in order to do that tests need to be conducted and further data collected.
“We are going to attempt to replicate what the leading cause of the failure was. Analysis is not enough, we need to do actual tests to understand how exactly the assembly stresses line up to cause the cracks that occured on the tank,” explained Bill Gerstenmaier, associate administrator for Space Operations.
No further cracks have been discovered on Discovery’s exernal fuel tank.
A fueling test will be conducted later this month at the launch pad to examine the external tank during cryogenic loading. The test will be heavily instrumented and involve removing foam, installing sensors, and then putting new foam on to simulate flight conditions.
Tests will also be conducted at NASA’s Michoud Assembly Facility in New Orleans, where the tanks are manufactured and assembled.
“Specific requirements for testing will be defined by next week, and we are looking for tests to be conducted in the late december time frame,” explained Space Shuttle Program manager John Shannon. “This is a solvable problem, and the testing plan layed out will identify the root cause of the cracks.”
Mission managers currently have no plans to roll Discovery back to the Vehicle Assembly Building, as there is no data driving a reason to do so.
As it stands right now, plans are for Discovery to launch on her final mission STS-133 in early February, which would be a night launch in the early morning hours. Endeavour’s final mission on STS-134, currently the official final launch on the manifest for the space shuttle program, would fly in early April, again in the early morning hours. A launch for Atlantis on STS-135, if approved to fly, would still be on track for a launch in the summer of 2011.