The idea of human spaceflight beyond Earth's orbit has captivated many Americans for more than half a century. As U.S. space policy has evolved, new opportunities have emerged, and new challenges have arisen. For the past several years, the priorities of NASA have been governed by the Vision for Space Exploration. It directed NASA to focus its efforts on returning humans to the Moon by 2020 and some day sending them to Mars and "worlds beyond." The resulting efforts are now approaching major milestones, such as the end of the space shuttle program, the design review decisions for the new spacecraft intended to replace the shuttle, and decisions about whether to extend the operation of the International Space Station. This book analyses the issues of NASA's future pursuits and interactions with other federal agencies and the growing role of the space industry.