1894–1989, Austro-German astronautical pioneer, b. Hermannstadt, Austria-Hungary (now Sibiu, Romania). Beginning his studies in astronautics before World War I, he first proposed a liquid-propellant rocket in 1917 and in 1923 published his unsuccessful Ph.D. dissertation, The Rocket into Interplanetary Space, which discussed many aspects of rocket travel. He expanded this small pamphlet into a larger work, The Road to Space Travel (1929), which won wide recognition. During World War II he worked with Wernher von Braun in the German rocket program at Peenemünde; he again worked with von Braun in the United States after the war.