CAPE CANAVERAL, Fla. (Reuters) - NASA (news - web sites) is considering whether it can return its space shuttles to flight without making two safety improvements that have so far proved to be high hurdles for agency engineers, top officials said on Friday. After the space shuttle Columbia disintegrated over Texas last year and killed the seven astronauts aboard, the Columbia Accident Investigation Board drafted a lengthy list of ambitious reforms. Among other proposals, the board recommended NASA come up with a way to repair damage to the leading edge of a shuttle's wing, such as the kind that doomed...