As I recall the original engineering estimate was a 2% catastrophic failure rate - i.e. loss of orbiter - on the Shuttle [1]. Columbia was STS 107. The estimate was spot on. You have to respect the level of engineering involved here.

[1] http://www.amazon.com/Development-Shuttle-1972-1981-History-...

> The Space Shuttle was based on engineering studies that

> somehow didn't anticipate that the whole spaceship would blow

> up if launched on a cold day[1] nor anticipate that the

> shuttle could break up on reentry if it was nicked by a piece

> of its own booster rocket while being launched.[2]

However it is worth noting that the engineers correctly predicted about a 2% catastrophic failure rate - that is loss of orbiter. Sure enough we lost two shuttles by mission 107. You can find the prediction in one of the two volume histories of the Space Shuttle project [1], [2].

Incidentally I think the books should be required reading for all engineers to understand how truly ambitious national projects such as the Shuttle are done. That includes the political, economic, and of course engineering issues involved.

[1] http://www.amazon.com/Shuttle-Decision-1965-1972-History-Vol...

[2] http://www.amazon.com/Development-Shuttle-1972-1981-History-...