This paper (which was presented at a meeting of the Deutsche Gesellschaft für Ortung und Navigation held in Berlin in April 1963) describes the navigational techniques of manned space flight as they are at present conceived by the National Aeronautics and Space Administration in the United States. Although the paper is written in a more or less popular form, it should be of wide interest to navigators in showing the lines along which thought on this subject is developing, in one country at least.