It's simple economics: Sure, Virgin Galactic could be up and running in the coming years, and they might even turn a profit. But the number of passengers willing to pay for a suborbital flight—a quick taste of space that Kathy Sullivan bluntly calls a "lark"—is probably not large enough to support growth in the space tourism industry, Aldrin and Sullivan agreed. As Aldrin put it, "We know nothing about this market." And without growth, spacecraft remain incredibly expensive to build, spaceflight doesn't get cheaper, and large, publicly owned companies—the ones with the real money—are unlikely to get involved. (An interesting little tangent on the economics of scale in the aerospace industry: According to a chart presented by Aldrin, the Air Force's controversial F-22 Raptor is only a little less expensive per pound than Space Shuttle Endeavor).