I think that without a major overhaul, the shuttle will never be completely free from this kind of threat. No matter how they modify the tank design, they're still be a danger... and probably one greater than NASA, or to a greater extent, the american people consider acceptable. They'll pretty much need a complete redesign of either the tank, or the shuttle's tile protection system. Considering that they've flown for 20 years without encountering any manifestation of this problem serious enough to bring down an orbiter, its reasonable to assume that they could fly the next 5 years without it happenning again. If I were an astronaught, it's a risk I'd be willing to take. My point is this: sure, I think all they've done for the shuttle in their return to flight opperations have proably significantly reduced further threat from this kind of thing, but as I said further up, the threat will never be reduced enough to the satisfaction of those in change of this thing, and I don't think that delaying the launch for 2 months will reduce it any further. If the lingering threat is considered too great to resume launches, then they should scrap the whole fleet becuse they'll never be satisfied with the threat level.
