UNDERWATER rescue capsules fighting to reach 118 seamen trapped on a Russian nuclear submarine have failed again as new evidence suggested a massive explosion shattered large areas of the vessel. Navy officials said there were no signs of life, but some of the crew could still be alive. Rescue capsules trying to link up with the submarine for the past three days have again been driven back by racing currents and swirling sand in the inky darkness on the sea bottom. Prime Minister Mikhail Kasyanov said the situation was “close to catastrophic,” according to Russian news reports. British and Norwegian rescue teams heading for the scene by ship are not expected to arrive until Saturday, raising fears they would be too late.