The seven years since the original edition () was published have seen the dawn of the atomic age, which has added tremendous spurt to man's millennium-old dream of travel into the universe. The present edition has been brought up to date--the two-stage rocket, for example, described as a possibility in 1944, is now reality. Other new material includes a chapter on two proposals that may be realized within the next few years--the launching of an orbital rocket, and a trip and subsequent base setup on the Moon.