1957-10-07 USSR Tsiolkovsky (1857-1935)

A First Day Cover commemorating the 100th anniversary of Konstantin Tsiolkovsky's birth, Russian rocket theorist and pioneer of astronautics, postmarked in Khimki with a hand cancel on October 7, 1957, three days after the launch of Sputnik 1.

Konstantin Tsiolkovsky was born on September 17, 1857 (September 5 Old Style) and died in 1935. He is widely regarded as one of the founding theorists of modern astronautics. Although he never built or launched a rocket, Tsiolkovsky developed mathematical theories that laid the foundation for many later advances in spaceflight. His most famous contribution was the rocket equation, which relates a rocket’s velocity change to its exhaust velocity and the ratio of its initial to final mass.

Tsiolkovsky also proposed several concepts that later became fundamental to space exploration, including liquid-fueled rockets, multistage rockets, liquid hydrogen and oxygen propellants, pressurized spacecraft, orbital space stations, and the use of space stations as bases for further exploration. His 1903 work, The Exploration of Cosmic Space by Means of Reaction Devices, was particularly influential in establishing the theoretical foundations of modern rocketry.