WASHINGTON - NASA workers inspecting space shuttle Atlantis this week discovered that a tiny piece of space debris had punched a harmless hole in a radiator panel during the shuttle's flight last month. Atlantis' six astronauts were never in danger, NASA spokesman Kyle Herring said Friday. The damage was not to any part of Atlantis' important heat shield, which protects the shuttle from superheated gases during re-entry to Earth's atmosphere. The shuttle's huge radiator system, attached to the payload bay doors, is crucial to cooling the spacecraft while it's orbiting Earth. When the shuttle opens its cargo bay doors once...