According to NASA's website the next space shuttle scheduled to go up is Atlantis with commander Eileen Collins in command. Is NASA going to wait until they have a definite answer for the loss of Columbia or would they still be willing to launch another shuttle whilst the investigation is ongoing? The investigation could take many months or even years and the ISS can't go that long without the shuttle. One of the main reasons why shuttles didn't fly for almost 3 years after Challenger was the investigation took a while and also the boosters had to be redesigned. If the investigation into STS-107 proves the tiles are at fault then remodification will again be necessary before shuttles can fly again.