By the end of the 19th century, soldiers, sailors, and practical and not-so practical inventors, had developed a stake in rocketry. Skillful theorists, like Konstantian Tsiolkovsky in Russia, were examining the fundamental scientific theories behind rocketry. They were begirning to consider the possibility of space travel

By the end of the 19th Century, a Russian theorist, Konstantian Tsiolkovsky, was examining the fundamental scientific theories behind rocketry. He made some pioneering studies in liquid chemical rocket concepts and recommended liquid oxygen and liquid hydrogen as the optimum propellants. In the 1920's, Tsiolkovsky analyzed and mathematically formulated the technique for staged vehicles to reach escape velocities from Earth.