Shuttle Delayed To Extinction?

I highly recommend this piece on the shuttle flight delay. It goes much more in depth into the causes behind the Columbia disaster. A perplexing issue for me has always been that every article I've read fails to explain why NASA Engineers are looking so vigorously at potential damage from falling ice when NASA was so sure that the culprit was falling foam. That is until now:

As for why engineers just now realized ice formation around the feedline bellows posed a serious threat, Hale said "we concentrated on the foam because that was the cause of the (Columbia) accident."

"But we knew we had to do an exhaustive search through everything that could be a potential problem," he said. "After a great deal of testing and analysis, we've been able to take some 175 potential debris sources off our worry list. We believe we've mitigated those. And we have the engineering evidence to prove they're not a concern.

"We knew we had three or four more items to work on and we also knew there was this ice that forms in certain places on the external tank, which we thought was probably not a major concern but we needed to ensure that. So what you've seen here is the diligence and rigor of going through every piece of the process to ensure that we've eliminated at least to the best of our ability the hazard from ascent debris.

"We've come to the conclusion we really need to do something about this ice. We have several options to deal with it and it's going to take us just a few more weeks to deal with that problem. We certainly cannot fly until we've convinced ourselves that it's safe to fly."

The Basic reason: just due diligence.

I still think that's a pretty loose argument. If they believe the threat was really not a major concern than why would they be going to such lenghts to eliminitate it from existence? Also why the flight delays? Why all the testing? Why identify 175 potential other causes?

The piece does mention External Fuel Tank sensors malfunctioning as being an area of major concern. But this is the first time I've ever heard them being mentioned. Is it possible that this the real reason why the return to flight is being delayed? It may be that NASA is only using the excuse of falling ice when in reality it's something much more serious.

I love the spin on this whole thing though. We are lead to believe that this is all just due diligence from NASA. It's as if NASA's culture has changed over night to meet the CAIB recommendations.

Somehow I doubt it.

Also it says in the piece that tile damage seemed to favour the right of the shuttle body. I've been wondering why that is...