The United States’ leadership in space is a natural result of its high standing among the world’s democracies and its vast wealth, which enables it to spend more than US$35 billion annually on civil and national security space activity, far surpassing all other nations. NASA’s manned space shuttle, representing tens of billions of dollars of investment, embodied US leadership in space. It was the foundation on which the International Space Station, the largest and most complex undertaking in space, was built.