Future astronauts must travel light and fast if they are to explore the moon and Mars, NASA visionaries predicted Tuesday. That could mean human explorers will board nuclear-powered rockets for their deep- space destinations and, when they arrive, unpack an inflatable habitation module that’s equipped with machinery to recycle air and water. “These are difficult missions, but they are things we can do if we make the right investments,” said NASA’s Gary Martin, who was recently named the agency’s first space architect. “You have to start investing in the technologies.”