Konstantin Eduardovich Tsiolkovsky
He was born in Ijevskoe, Russia. As a child he was sickly and hard of hearing, and was not accepted at elementary schools, so was home schooled until 16.
Tsiolkovsky theorized many aspects of space travel and rocket propulsion. He is considered the father of human space flight and the first man to conceive the space elevator. His most famous work was "The Exploration of Cosmic Space by Means of Reaction Motors", which published in 1903 was arguably the first academic treatise on rocketry. Unfortunately his ideas never made it out of Russia, and the field lagged until German and other scientists independently made the same calculations decades later.
Tsiolkovsky also delved into theories of heavier than air flying machines, independently working through many of the same calculations that the Wright brothers were doing at the same time. However, he never built any practical models, and his interest shifted to more ambitious topics.
F. A. Cander became enthusiastic about Tsiolkovsky's work and in 1924 he established first Cosmonautics Society in Soviet Union and later he made and successfully researched rockets with liquid fuel of type OR-1 (1930) and OR-2 (1933). On August 23 1924 Tsiolkovsky was elected as a first professor of the Military-Air Academy N. E. Zhukovsky.
In 1929 Tsiolkovsky proposed the construction of step rockets.
The basic equation for the rocket movement is named after him:
He was also an adherent of philosopher Nikolai Fyodorov, and believed that colonizing space would lead to the perfection of the human race, with immortality and a carefree existence.
Tsiolkovsky died in Kaluga, Soviet Union (today Russia), where there is a museum of astronautics, named after him.