Space Shuttle Endeavour - Repairs Underway, but Cause Unknown

The Space Shuttle Endeavour was to have blasted off last Saturday, but the launch was scrubbed due to a hydrogen leak.

The leak, in a line releasing excess gas pressure from the liquid hydrogen tank, was almost identical to one that delayed the launching of the shuttle Discovery three months ago. After replacement of the seals, the Discovery took off without a problem four days later.

“The repair is going well,” said a shuttle test director, Steven J Payne at a news conference.

Engineers found some small gaps in the seals that the hydrogen probably leaked through, but they do not understand the underlying cause of the problem.

Personally, I would not characterize not understanding the underlying cause of the probem as "going well." But that's just me.