Current U.S. policy, including the National Security Strategy and the National Space Policy, declares that access to space has become a vital national interest of the United States. This study examines the justification for this assertion. By examining the definition of vital national interest and U.S. national security policy, this study developed three criteria by which to judge the importance of space-based systems to U.S. national security. These criteria were used to evaluate the contribution of space-based systems to U.S. economic vitality, conventional military capabilities, and physical survival. A numerical model related these criteria, addressing their relative importances by applying different numerical weights to each. This research indicates that the assertion that access to space is a vital national interest of the United States is indeed justified. Denying access to the services provided by space-based systems would have a very negative effect on U.S. economic vitality, conventional military capabilities, and physical survival. The United States should commit as a nation to maintaining leadership in the global space industry and insuring continuity of service from space-based systems in spite of environmental catastrophe or deliberate interference. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. As a reproduction of a historical artifact, this work may contain missing or blurred pages, poor pictures, errant marks, etc. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.