To further his education, young Tsiolkovskiy went to Moscow to pursue studies in chemistry, mathematics, astronomy, and mechanics. His father brought him home after only three years, however, after learning that he was going hungry and overworking himself. Upon returning home he became a tutor in mathematics and physics and in the process, completed his education. In 1878 he passed the required examinations and received a diploma to pursue work as a “people's school teacher,” a teacher in essentially the Russian equivalent of an American high school or a German gymnasium. He obtained a teaching position in arithmetic and geometry at the district school in Borosck, Kaluga Province, about 60 miles (100 kilometers) north of Moscow. He would remain in the Kaluga area for the rest of his career.

Tsiolkovskiy demonstrated genius in scientific matters. In 1881, for instance, he broke new ground with an article on the fundamentals of the kinetic theory of gases. His second publication, The Mechanics of a Living Organism, earned him election into the Society of Physics and Chemistry in St. Petersburg. Other publications, The Problem of Flying by Means of Wings (1890-1891) and Elementary Studies of the Airship and Its Structure (1898), showed Tsiolkovskiy's growing fascination with flight. To demonstrate his work on airships, he built a wind tunnel, the first in Russia, that allowed testing of the aerodynamic characteristics of different aircraft designs. Using his wind tunnel, he studied the effects of friction and surface area on the velocity of air over a streamlined shape. For his work, the Academy of Sciences awarded him funds that he used to build a larger wind tunnel.

Tsiolkovsky published a report in 1903 that suggested the use of liquid propellants for rockets in order to achieve greater range. Tsiolkovsky stated that the speed and range of a rocket were limited by the exhaust velocity of escaping gases.

 Gradually Tsiolkovskiy turned more of his attention to spaceflight and began to write about space. His book Gryozy o zemie i nebe (Dreams of Earth and Sky) was published in 1895, and the next year he published an article about communicating with creatures from other planets. In 1898, he submitted an article for publication to the Russian journal, Nauchnoye Obozreniye (Science Review) titled “Investigating Space With Rocket Devices,” that presented years of calculations and laid out many of the principles of modern spaceflight, which opened the door to future writings on the subject. Tsiolkovskiy described in depth the use of rockets for launching orbital space ships. This article finally was published in 1903.

Tsiolkovskiy experienced several setbacks and tragedies in the first two decades of the new century. In 1902 his son committed suicide, and in 1908 his house was flooded, with many of his scientific materials destroyed. Further, his aerodynamic experiments went unrecognized by the Academy of Sciences.

He persevered, however, and soon carried out a series of increasingly sophisticated studies on the technical aspects of spaceflight. In the 1920s and 1930s, Tsiolkovskiy proved especially productive, publishing ten major works clarifying the nature of bodies in orbit, developing scientific principles behind reaction vehicles, designing orbital space stations, and promoting interplanetary travel. He also expanded the scope of studies on many principles commonly used in rockets today: specific impulse to gauge engine performance, multistage boosters, fuel mixtures such as liquid hydrogen and liquid oxygen, the problems and possibilities inherent in microgravity, the promise of solar power, and spacesuits for extravehicular activity. Significantly, he never had the resources—perhaps not even the inclination—to experiment with rockets himself.

After the Bolshevik revolution of 1917 and the creation of the Soviet Union, Tsiolkovskiy was formally recognized for his accomplishments in the theory of spaceflight. Among other honours, in 1921 he received a lifetime pension from the state that allowed him to retire from teaching at the age of 64. Thereafter he devoted his full attention to developing his spaceflight theories. He died at his home in Kaluga on September 19, 1935. His theoretical work greatly influenced later rocketeers, both in his native land and throughout Europe.