While NASA and White House policy-makers have been kicking around space destinations and science goals, engineers at the agency’s Marshall Space Flight Center in Huntsville have been working on making rocket fuel from space rocks, using a planet’s atmosphere to slow a spaceship and developing better engines to cut trip times. “The technology for space is there; it’s been worked on for years,” said Charles Vick, an aerospace expert formerly with the U.S. Space & Rocket Center in Huntsville and now a senior fellow at GlobalSecurity.org, a nonprofit in Washington, D.C.