Information on the contribution of one of the following to the development of space exploration: Tsiolkovsky.

Konstantin Eduardovitch Tsiolkovsky 1857-1935 Konstantin Tsiolkovsky was a true visionary and pioneer of astronautics. He theorized many aspects of human space travel and rocket propulsion decades before others, and played an important role in the development of the Soviet and Russian space programs. He was born on September 17,1857, in the village of Ijevskoe, Ryasan Province, Russia, the son of a Polish forester who had emigrated to Russia. He was not from a rich family, but …

…called this a principle of the sky train. The train gets a boost from cars full of coal (fuel), and as the cars deplete their fuel they are discarded. As the cars are discarded the weight which the train pulls decreases and its speed increases. Similarly, Tsiolkovsky argued, by discarding the used rocket stages after their fuel is spent, the spacecraft accelerates and does not need to waste is power bringing useless weight into space.