HOHMANN, Walter.

München und Berlin, Druck und Verlag R. Oldenbourg, 1925. 8vo. (8),+ 88 pp. Illustrated. Sewn as issued, uncut and unopened in well-preserved publisher’s wrappers. Stamp of Deutschen Raketen- und Raumfahrtmuseum, Stuttgart, on first blank leaf. In a later cloth box. Alicke, The Moon in Science & Fiction 181 & 182: ”An incunabulum of space flight”. Ley, Rockets, Missiles, and Space Travel (1959), p. 506: ”One of the classical works of space travel.” First edition, second issue. First issued in blue illustrated wrappers, the book failed to sell in significant numbers, perhaps partly due to its highly theoretical content and the fact that rockets large enough to carry objects into space was still an abstraction in the mid 1920s. The rest of the edition was later reissued with the plain printed wrappers present on this copy. A total of 1500 copies were printed and both issues are now rare.Walter Hohmann (1880-1945) was born in Hardheim, Germany, and lived in South Africa for part of his youth, during which time he developed an interest for astronomy as he studied the southern constellations together with his father. He graduated from the Technical University of Munich in 1904 and received his Ph.D. from the RTWH Achen University in 1920. Hohmann spent his career working as an engineer and a city planner in Vienna, Hanover and Breslau (Wroclaw), before settling in Essen. In his spare time he revived his interest in astronomy and began to give serious thought to the problem of interplanetary flight. A key element, he discovered, was fuel-efficiency, which eventually led him to calculate and present, in the present work, what is now known as the ”Hohmann transfer orbit”, an orbital manouver using only two engine impulses to move a spacecraft between two coplanar orbits. The publication led to his involvement in the Verein für Raumschiffahrt, a German society of amateurs propagating rocket development and space flight. However, the increased focus on the use of rockets as weapons during the Nazi era led to Hohmann’s disinvolvement from rocketry, as he only wanted to contribute to its peaceful uses.Perhaps a good measure of the importance of ”Die Erreichbarkeit der Himmelskörper” is that an English translation entitled ”The attainability of heavenly bodies” was published by NASA in 1960. For many years the ”Hohmann transfer orbit” was believed to be the most fuel-efficient way to - for example - move a satellite from a lower to a higher orbit, until a more complicated but even more efficient approach, called the ”bielliptic transfer”, was developed. Hohmann also took an interest in many other aspects of spaceflight and proposed, among other things, a separate landing module for a spacecraft travelling to the moon. The latter idea was, as we know today, followed through by the American Apollo project in the 1960s.