Complex sentence: Their first real rocket, powered by black powder, was named Auk 1; the Great Auk is a flightless sea bird that became extinct in the mid- 19th century.
Split into simpler sentences: Their first real rocket, powered by black powder, was named Auk 1. This an allusion to the Great Auk, which is a flightless sea bird that became extinct in the mid- 19th century.