As expected, a lot of people are second-guessing NASA over not paying more attention to possible damage done to the left-wing of Columbia during launch and ascent. First, it’s not even certain that the insulation coming off the external tank and hitting the shuttle caused the disaster. But the question is what could they have done if they had found damage.
The orbiter wasn’t carrying its robotic arm and they didn’t have the rocket-backpacks on board, so getting someone out underneath the ship to repair it wasn’t likely. If the NASA engineers couldn’t come up with something to fix the ship, if they’d known about the problem early in the flight, they might have been able to send up a rescue shuttle. Atlantis was scheduled to launch on a flight on March 1 to the Space Station carrying a replacement crew. With a few modifications to the mission plan they could have launched early and they might have been able to either bring up a repair solution or, in the worst case, bring the Columbia crew back with them and leave Columbia to burn up alone in the atmosphere.
Of course, in the end what-ifs are only useful for those who run things so that they can make better decisions next time. For the rest of us, I guess it doesn’t serve much purpose.