If there is a small rocket on top of a big one, and if the big one is jettisoned and the small one is ignited, then their speeds are added.

Indeed Von Braun said of him:
In 1938 the Oberth family left Sibiu Romania for good to first settle in Austria then in Nazi Germany then in the United States and finally back to a free Germany. In 1922 Oberth's proposed doctoral dissertation on rocket science was rejected as "utopian". Oberth returned to the United States to view the launch of 61A the space shuttle Challenger launched October 30 1985.

Hermann Julius Oberth (25 June 1894 – 28 December 1989) was an Austro-Hungarian-born German physicist and engineer.