Long before the Columbia
disaster, NASA began worrying about its dependence on a fleet of aging, expensive, and fragile space shuttles. In May 2001, the agency consolidated its plans into a program to develop a next-generation shuttle by 2020. That timetable now looks absurdly sluggish, so NASA is focusing on what was, until a few months ago, a secondary part of its manned space strategy: the multibillion-dollar Orbital Space Plane. "It will be a lifeboat for the International Space Station and a transport system that supports a four-man crew on the station," says Dennis Smith of the Marshall Space Flight Center, the program manager for the project.