Notes: • On the title page Clarke is described as ''B.Sc., F.R.A.S. / Chairman, British Interplanetary Society'' • Preface by the author [xi-xiii] signed ''London. May 1951.'' • Illustrated with frontispiece in colour and 14 plates (3 in colour). Most of them (I-V, IX, XI-XII, and the frontispiece) are drawings by Leslie Carr and/or R. A. Smith. • 18 figures in the text. Enlarged versions of the first and the last figure reprinted on the front and back endpapers, respectively. • Includes index. • Separated into the same 18 chapters as the Revised Edition (1959). • Illustration on the cover identical with Plate XIII by Leslie Carr.