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The Heinkel He 176 was the world 's first aircraft to be propelled solely by a liquid-propellant rocket engine , making its first powered flight on 20 June 1939 with Erich Warsitz at the controls .
 Heinkel He 176, Erich Warsitz
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Heinkel He 176, Erich Warsitz