Their visions range in scope from grand--Buzz Aldrin's wide-body orbital space-liner--to grander--extracting platinum from asteroids or the Moon to serve as a catalyst in terrestrial fuel cells--to grander still--Mars Society chief Robert Zubrin's plan to send astronauts to Mars without the fuel to get back, because a robotic craft, sent earlier, would have produced the fuel in situ. Their motives comprise both the high-minded (the Planetary Society's efforts, through its SETI program, to send interstellar messages conveying human altruism) and the chiefly mercantile, like Team Encounter's DNA-launch scheme. They are steel-tacks business guys who project that once the highway gets humming up there in low Earth orbit, it's going to need mechanics, and it's going to need hoteliers, and it's going to need gas-station attendants. They are the engineers chasing the X Prize by building suborbital rocket ships that look like Frisbees or cigars, that will launch from beneath the surface of the ocean or from the world's largest helium balloon, that will come down under parachutes or land on conventional runways. They are doing this work to save the species, or to get rich, or to force regulators to define their terms, or just because it's a kick (or some combination thereof). They are the kind of people you want to sit next to at a dinner party: folks like Brian "Rocket Guy" Walker, who is building a personal, hydrogen-peroxide-powered rocket that looks like a 37-foot-tall lawn dart, funded mostly by sales of kids' toys he has invented. Or William Stone, a robotics engineer who is working on a way to return from space cheaply with equipment that weighs only a few hundred pounds.