Two weeks ago, high above eastern Asia, a Chinese missile unerringly hunted down and struck its target. The precision was impressive--and frightening in its strategic cunning.

IT HAS ALREADY BECOME conventional wisdom that President Bush's proposed mission to send a man to Mars will cost a trillion dollars--even many trillions of dollars. At that cost, it's no wonder public support for the White House space vision is wavering. But is that number credible? Where does it…