He was born in Izhevskoye (now in Spassky District, Ryazan Oblast), in the Russian Empire, to a middle-class family. His father, Edward Tsiolkovsky (in Polish: Ciołkowski), was Polish; his mother, Maria Yumasheva, was an educated Russian woman. His father was a Polish patriot deported to Russia as a result of his revolutionary political activities. At the age of 10, Konstantin caught a serious illness and became hard of hearing. He was not accepted at elementary schools because of his hearing problem, so he was self-taught.
Tsiolkovsky theorized many aspects of space travel and rocket propulsion. He is considered the father of human spaceflight and the first man to conceive the space elevator, becoming inspired in 1895 by the newly-constructed Eiffel Tower in Paris.
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.
Nearly deaf, he worked as a high school mathematics teacher until retiring in 1920. Only from the mid 1920s onwards was the importance of his work acknowledged by others, and Tsiolkovsky was honoured for it. He died on 19 September 1935 in Kaluga and was buried in state.
In the late 19th and early 20th century, Tsiolkovsky 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. Because Tsiolkovsky's ideas were little known outside Imperial Russia, the field lagged until German and other scientists independently made the same calculations decades later.
In 1923, German physicist Hermann Oberth published his thesis By Rocket into Planetary Space, which triggered wide-scale interest and scientific research on the topic of space flight. It also reminded Friedrich Zander about once having read an article on the subject. After contacting the author, he became active in promoting and further developing Tsiolkovsky's work. In 1924 Zander established the first astronautics society in the Soviet Union, the Society for Studies of Interplanetary Travel, and later researched and built liquid-fuelled rockets named OR-1 (1930) and OR-2 (1933).
In 1924, a writer for the Russian newspaper Izvestiia reported on A Method of Reaching Extreme Altitudes, a groundbreaking work on the rocketry experiments being done by Robert Goddard, which had been published in 1919 but was not noticed in the Soviet Union until Hermann Oberth referenced it in his later work. When news of the article reached Tsiolkovsky, he decided to republish his early works along with a flurry of new articles about space.
Only late in his lifetime was Tsiolkovsky honoured for his pioneering work. On 23 August 1924 he was elected as a first professor of the Military Aerial Academy named after N. E. Zhukovsky (Военно-воздушная академия им. Н. Е. Жуковского).
His most important work, published in 1903, was The Exploration of Cosmic Space by Means of Reaction Devices (Исследование мировых пространств реактивными приборами), arguably the first academic treatise on rocketry. Tsiolkovsky calculated that the horizontal speed required for a minimal orbit around the Earth is 8,000 m/s (5 miles per second) and that this could be achieved by means of a multistage rocket fueled by liquid oxygen and liquid hydrogen.
During his lifetime he published over 500 works on space travel and related subjects, including science fiction novels. Among his works are designs for rockets with steering thrusters, multi-stage boosters, space stations, airlocks for exiting a spaceship into the vacuum of space, and closed cycle biological systems to provide food and oxygen for space colonies.
Tsiolkovsky had been developing the idea of the air cushion since 1921, publishing fundamental paper on it in 1927, entitled "Air Resistance and the Express Train" (Сопротивление воздуха и скорый поезд). In 1929 Tsiolkovsky proposed the construction of multistage rockets in his book Space Rocket Trains (Космические ракетные поезда).
Tsiolkovsky's work influenced later rocketeers throughout Europe, like Wernher von Braun, and was also studied by the Americans in the 1950s and 1960s as they sought to understand the Soviet Union's successes in space flight.