A large part of the CAIB's asking will have been based upon the question of, "could NASA have done more to avoid the fatalities, after the issue had arisen?". I

A large part of the CAIB's asking will have been based upon the question of, "could NASA have done more to avoid the fatalities, after the issue had arisen?". If the conclusion of the hypothetical scenario was they could not have launched another craft in time, then it is obvious that, even had NASA known the extent of the damage of Columbia, they would have had no means to bring the crew back safely (though, of course, an Atlantis-based rescue mission wouldn't, per-se, be any safer, because Atlantis could easily fall foul of the same issue Columbia had).