briefly into a cloud, you could almost hear a quarter of a million gasps, until it reappeared in the bright blue sky. then discovery passed the 73-second mark, the moment challenger exploded. discovery, go with throttle up. throttle go. reporter: the redesigned booster rockets had worked and the spent casings split off from the shuttle to drift to the sea for recovery. nasa was elated. even though they had launched more than an hour and a half late. and so be it, but i guarantee you, it was a keeper. the nasa managers indicated that despite their elation, they will never compromise their standards. speaking as a member of the mission management team, if you ve lived through 51-l, you ll never take it for granted. reporter: that is the real lesson of challenger. no matter how easy they make it look in the future, no one can take space travel for granted. not nasa nor any of the rest of us. peter?