Structural Crack Found on Shuttle Tank

The chances of space shuttle Discovery launching on the STS-133 mission in 2010 could be in jeopardy. Cracked foam on the shuttle’s external tank was removed early Wednesday morning and underneath engineers found a structural crack on the tank itself. The serpentine crack is about 22 cm (9 inches) long and is located on a structural rib or “stringer.” Cracks like this have appeared on other tanks and were fixed at the production facility in New Orleans. But this type of repair has never been attempted at the launch pad.

Engineers are also working to pin down the cause of a hydrogen gas leak, which forced NASA to call off the launch last week. The next launch window opens November 30 and closes December 6. But with the hydrogen leak work still ongoing, and given the uncertainties of the crack, it seems unlikely Discovery could be ready to go within that time frame.

The website NASASpacefight.com said similar repairs have been done by “removing the cracked aluminum and replacing it with a “doubler,” which is a twice-as-thick stringer section before replacing the foam insulation.” But again, this has only been done at the production facility.

Former shuttle launch director Wayne Hale posted a comment on NASA Spaceflight.com, saying the crack was troubling. “Not only does this most likely have to be repaired – and that could be difficult,” Hale wrote, “ but understanding the root cause of the problem and developing flight rationale are going to be very difficult. I am thinking that a launch this calendar year is in jeopardy. Good luck to the team, if anybody can solve it the folks at MAF, MSFC, and the other centers can do it. I hope I am being overly pessimistic and this turns out to be simple; but right now it doesn’t look like it.”

Discovery’s mission to the International Space Station will bring a new storage module and the first humanoid robot, Robonaut 2, or R2 to the station

Source: NASASpaceflight.com