Simplify the following text for a Grade 7 native English-speaking person.
Original: Wernher Magnus Maximilian Freiherr von Braun ( March 23 , 1912 -- June 16 , 1977 ) was a German-American rocket scientist , engineer , space architect , and one of the leading figures in the development of rocket technology in Germany and the United States during and after World War II .
Simplified: Dr. Wernher Magnus Maximilian Freiherr von Braun ( 23 March 1912 -- 16 June 1977 ) was a German engineer and scientist . He worked as a rocket designer between the 1930s and 1970s .