In many fields, the expectations game works. If critics aren't expecting a great movie, they can't be disappointed. In debates, politicians are often judged not against one another, but against expectations of themselves. Even blog entries can set the bar low in a self-deprecating opening line.

But this game doesn't work for space travel. Why has NASA been going around telling everybody about a faulty sensor in the fuel tank? And why do they seem OK to launch without it? I have no idea what a sensor is or does, but I wouldn't feel comfortable blasting off into space when anything isn't functioning.

These quotes from Discovery vehicle manager Scott Thurston don't inspire confidence (from CNN):

"That's like trying to predict lightning -- you know it's going to strike, you just don't know where."

Some of the work the engineers have done -- including redoing the grounding -- "should help with the issue, if that was the issue."

"We're two-failure tolerant."

I don't think another shuttle crash would somehow seem more acceptable because expectations were managed.