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If all this engineering, duplication and training fails, the U.S. Navy maintains a rescue sub perpetually on alert in San Diego. Built in the wake of the Thresher's loss, it is designed to reach trapped submariners anywhere in the world within three days. It could have come--had the Russians asked--to the Kursk's aid last week. Should American submariners find their vessel sinking, they have been trained to pull emergency stores of food and oxygen into whatever living space remains. They know that the rescue sub's goal is to hook up with a downed submarine within 72 hours of an accident. So on any stricken U.S. submarine, the survivors' goal is simple: Stay alive for one week, giving rescuers more than enough time to bring them to the surface.
--By Mark Thompson. With reporting by Douglas Waller/Washington