Hermann Julius Oberth, Austro-Hungarian lecturer, 1930.

HUNGARY - SEPTEMBER 12: Hermann Julius Oberth (1894-1989) was regarded, with Robert Goddard (1882-1945), as one of the fathers of modern astronautics. He simulated weightlessness and designed a long-range liquid-propelled rocket. He published 'The Rocket into Interplanetary Space' and later wrote 'The Road to Space Travel'. In 1941 he was assistant to the German rocket engineer Wernher von Braun (1912-1977) and worked with the Italian Navy developing solid-propellant and anti-aircraft rockets and advanced rocket research for the US army. (Photo by SSPL/Getty Images)