Marshall Space Flight Center will play a key role in NASA’s plan to develop and build nuclear-powered spacecraft, NASA Administrator Sean O’Keefe said during a visit to Huntsville Friday. Dubbed Project Prometheus – after the Greek god who gave humans fire – the space agency plans to develop nuclear-power technologies that will advance exploration of space. O’Keefe, in a speech to Marshall employees, said nuclear power will extend man’s reach beyond where chemical rockets and solar arrays can take spacecraft today. “There is a need . . . to concentrate on how to do things in the future that we can’t do today,” O’Keefe said.