The Discovery crew is poised to carry out an unprecedented repair on the space shuttle today.Astronaut Stephen Robinson will go beneath the craft to repair damage sustained during the launch. The crew admitted they had misgivings about the job but said the more they learned about the plan, the more comfortable they felt. It involves removing two pieces of ceramic-coated cloth dangling from the ship’s delicate heat shield which protects the shuttle from burning up on re-entry. “It’s simply to get a hold and pull it out and we expect that it will be that simple,” a NASA official said. President George W Bush spoke to the shuttle crew yesterday in an attempt to boost morale. “I know you have very important work to do ahead and we look forward to seeing the successful completion of this mission,” he said. The concern is that the protruding material may interfere with the smooth flow of air over the heat shield as the shuttle returns to Earth. That could lead to a build up of temperature and a repeat of the Columbia tragedy in which all seven astronauts lost their lives.