In 1930, von Braun attended the Technische Hochschule Berlin, where he joined the "Spaceflight Society" ("Verein für Raumschiffahrt" or "VfR") and assisted Willy Ley in his liquid-fueled rocket motor tests in conjunction with Hermann Oberth. In spring 1932, he graduated with a diploma in mechanical engineering. His early exposure to rocketry convinced him that the exploration of space would require far more than applications of the current engineering technology. Wanting to learn more about physics, chemistry, and astronomy, von Braun entered the Friedrich-Wilhelm University of Berlin for doctoral studies and graduated with a doctorate in physics in 1934. He also studied at ETH Zürich for a term from June to October 1931. Although he worked mainly on military rockets in his later years there, space travel remained his primary interest.