CAPE CANAVERAL, Fla. — Apollo 13′s astronauts never gave a thought to their mission number as they blasted off for the moon 50 years ago. Even when their oxygen tank ruptured two days later — on April 13. Jim Lovell and Fred Haise insist they’re not superstitious. They even use 13 in their email addresses. As mission commander Lovell sees it, he’s incredibly lucky.