For the first time since 1972, the United States is planning to fly to the moon, but instead of a quick, Apollo-like visit, astronauts intend to build a permanent base and live there while they prepare what may be the most ambitious undertaking in history — putting human beings on Mars. NASA’s moon planners are closely following the spaceship initiative and, within six months, will outline what they need from the new vehicle to enable astronauts to explore the lunar surface.