Today, NASA is thinking it probably wasn’t a problem with the insulating tiles on Columbia—or at least, not one that was caused by the main tank debris that hit the shuttle on liftoff.
Nevertheless, the most disturbing thing to me about the whole affair is learning that, even if they knew there was a serious problem with the tiles, there would be nothing they could do. In such a case, I suppose there’s always the chance of a rescue mission by one of the other shuttles or by a Russian craft. But you can also think of dozens of reasons why such a thing wouldn’t be able to happen in time. So NASA says they didn’t even do an EVA to check the tiles, presumably on the assumption that it would be better not to know. It’s hard to argue with that, assuming that they really couldn’t do anything about it.
I don’t guess I’m really surprised by this. Working in vacuum and microgravity is difficult, and putting those tiles on is notoriously tricky under the best circumstances. I know they use a special adhesive, and who knows whether that would adhere or dry properly in vacuum, or in the cold? And maybe they have to be applied under high pressure. But even though I’m not surprised, it’s very troubling to think about that situation: there’s something badly wrong, and it seems trivial (missing tiles!), but the crew will die, and there’s nothing they or anyone else can do.
It points to the next big challenges of spaceflight. Somehow we have to have a cheaper, simpler way out of the gravity well, so that we can have ships that are simple enough to be repaired in space. And we need to work on technologies that make it easier to work in microgravity and vacuum: lighter, less constricting and more flexible spacesuits, as well as thrusters or other tools that make it easier to get around, and ways to gain leverage in the absence of weight and friction.
(Oh, and I’ll second what Rael said.)