Sergei Alekseevich Chaplygin was born in the town of Ranenburg, Ryazan Province, on March 24 (April 5 in a new style) in 1869 in the family of clerk Alexei Timofeyevich and his wife Anna Petrovna. Even in childhood, the boy lost his father who died of cholera. Mother married a second time and went with the child to a new husband, tradesman Davydov, to Voronezh.

In 1877, Sergey entered the Voronezh men's gymnasium, where he quickly discovered his exceptional talents in almost all fields of knowledge, from ancient languages ​​to mathematics, to which the boy showed particular interest. At the age of fourteen, Chaplygin first tried himself as a teacher, becoming a tutor for landlord children.

After a brilliant graduation from the gymnasium in 1886, Sergey Alekseevich entered the Physics and Mathematics Faculty of Moscow University. At that time, a brilliant scientist, the “father of Russian aviation,” Nikolai Zhukovsky, worked at the university. By his request, after the graduation Chaplygin in 1890 was left at the university to prepare for professorship. Then Sergey Alekseevich became interested in mechanics. His first scientific papers were devoted to the problem of the motion of a solid body in a liquid. In them he raised some questions that had never been considered before. This led Chaplygin to the fundamental discoveries in the field of building general equations of mechanics, for which he was awarded in 1899 an honorary award - a large gold medal of the Academy of Sciences.

Since 1893, Chaplygin begins to teach professionally. As a private lecturer, he reads a course in applied mathematics at Moscow University, and at the same time, a physics course, at the Moscow Catherine Institute. From 1895 to 1901 he taught mathematics and theoretical mechanics at the Moscow Land Survey Institute, from 1896 to 1910 - mechanics at the Imperial Moscow Technical School. In 1901 - 1908, Sergei Alekseevich also taught at the Moscow Engineering School.

Chaplygin combined his teaching activities with administrative work. From 1905 to 1918 he was the director of the Moscow Higher Women's Courses, and from 1919 he was the rector of the 2nd Moscow State University, into which courses were converted. The case when the brave director began building buildings for courses on Malaya Tsaritsynskaya Street (now Malaya Pirogovskaya) became widely known, despite the fact that state money was not allocated in full. Sergey Alekseevich simply laid a plot of land relying on an educational institution.

University teaching Chaplygin left in 1911 for political reasons. It was then that the scandalous circulars of the Minister of Education, L.A. Kasso "On Supervision of Students in Educational Institutions", "On Temporary Non-admission of Public and Private Student Institutions" and a number of others. These documents prohibited student assemblies, destroyed university autonomy, and imposed police functions on university administration. In response, a group of 130 university lecturers, including such world-class stars as V.I. Vernadsky, D.M. Petrushevsky, V.P. Serbian, K.A. Timiryazev, P.N. Lebedev, resigned. S.A. Chaplygin was among them.

After the Revolution, Sergei Alekseevich focuses on scientific activities, which he combines with teaching. Since 1918, he has been working in the Commission for Special Artillery Experiments under the Main Artillery Directorate, as well as in the Scientific Experimental Institute of Communications. In 1918 - 1925, Sergey Alekseevich is a professor at the Moscow Forestry Institute.

However, the Central Aero-Hydrodynamic Institute (TsAGI) became the real life affair of Chaplygin, to the creation of which in 1918 he was attracted by the same N.E. Zhukovsky. In 1921, after the death of Zhukovsky, Sergey Alekseevich became the chairman of the board, and in 1928 - the director-chief of TsAGI. Since 1931, having left the post of director for health reasons and becoming the scientific director of the institute, Chaplygin has been working on the creation of the largest aerodynamic laboratories of TsAGI. In the same place, at TsAGI, he conducts a scientific-theoretical seminar, which brought up the whole colour of Soviet mechanical science. Among them is the future President of the USSR Academy of Sciences Mstislav Keldysh and the founder of the Novosibirsk Academgorodok Mikhail Lavrentyev.

It is difficult to overestimate the contribution of Sergei Alekseevich Chaplygin to the world of science.

In addition to the already mentioned works in the field of theoretical mechanics, Sergey Alekseevich worked in the theory of lubrication. In 1906, he published a joint with N.E. Zhukovsky work "On the friction of the lubricant layer between the spike and bearing," which was of great practical importance, causing a flurry of theoretical and experimental research in this area.

Last name Chaplygin known and mathematicians. In 1919, he proposed a method of approximate integration of differential equations and proved the inequality theorem, which was named after him. These studies are considered among the greatest achievements of mathematical thought.

In 1905 - 1907, Sergei Alekseevich wrote the university course “Mechanics of the system”, as well as the shortened course “Propaedeutic mechanics” - for technical universities and natural faculties of universities.

But as one of the pillars of world science, Chaplygin became famous, primarily because of the new branch of mechanics and gas dynamics he created. In his doctoral work “On Gas Jets”, which was defended at Moscow University in 1903, the scientist was well ahead of time — after all, in the age of low-speed aviation, which took the first steps, he proposed methods for studying gas jet movements at any speeds approaching the speed of sound. Only 30 years later, the knowledge gained by Chaplygin could be used in the aircraft industry!

But the tandem of Zhukovsky and Chaplygin also contributed to the development of modern aviation - they helped the designers in solving the problem of forces acting on the streamlined wing of the aircraft. Back in 1906, Nikolai Egorovich proved a theorem that contained the lift formula, but four years later the teacher and student independently supplemented the Zhukovsky theorem by formulating the Zhukovsky – Chaplygin postulate, which gave a complete solution to the problem of forces acting on the wing. This was a real breakthrough - it was precisely since then that the aircraft were no longer built "by eye", because the aircraft designers had precise tools for designing the wing. This not only affected the speed of the winged cars, but also their safety.

Later Sergey Alekseevich continued work in this area. In 1913, they presented the report "The Vortex Theory of Wing Lift", which gave new knowledge for designing wings, and in 1914 the fundamental work of the scientist "The Lattice Wing" was published, where the basis for calculations of screws, turbines and other blade machines was laid from home fans to modern aircraft turbines. Lattice wings are used in the construction of high-speed vessels, and in the creation of spacecraft.

In 1922, Chaplygin published another essay, “Toward a General Theory of a Monoplane's Wing,” thereby creating a theoretical basis for the further evolution of modern aviation to him. Already by the beginning of the 30s, domestic monoplanes will appear that will compete with world peers.

Sergey Alekseevich a lot and actively helped aircraft designers. He also worked with such an eminent creator of bombers and long-haul airliners, like Andrei Nikolaevich Tupolev, and with the designer of the famous U-2 fighter and “U-2 night bomber” Nikolai Nikolayevich Polikarpov.

For his numerous achievements in science, Sergei Alekseevich Chaplygin in December 1924 was elected a corresponding member of the Russian Academy of Sciences, and in January 1929, an academician of the USSR Academy of Sciences.

On February 1, 1941, by the Decree of the Presidium of the Supreme Soviet of the USSR, academician Chaplygin was awarded the title of Hero of Socialist Labor with the award of the Order of Lenin and the Gold Medal “Hammer and Sickle” in connection with the fiftieth anniversary of his scientific activity. Sergey Alekseevich became the first Hero of Socialist Labor from domestic scientists.

With the beginning of the World War II, TsAGI was evacuated to two rear cities - Kazan and Novosibirsk. Sergey Alekseevich leaves together with the formed branch №2 of the institute to the capital of Siberia. He has worked there for a whole year, having laid the foundations for the Siberian aviation science - after the war, the Siberian Aviation Research Institute named after Chaplygin, would be created on the basis of the TsAGI branch.

Sergey Alekseevich died on October 8, 1942 from cerebral haemorrhage. His last written words were: "As long as there is strength, we must fight ..., we must work."

His hometown Ranenburg (now part of the Lipetsk region), the streets in Moscow and the Moscow region Zhukovsky and Zheleznodorozhny, Novosibirsk, Tula, Krivoy Rog, Alma-Ata are named after Chaplygin. In Moscow and Novosibirsk (on the territory of SibNIA) the busts of the scientist are installed, and there is a monument on the territory of TsAGI.

The memorial museum-apartment of S.A. Chaplygin, and the grave of a scientist, also located on the territory of SibNIA in Novosibirsk, are monuments of federal significance.

In 1942, the Academy of Sciences of the USSR established the SA Award. Chaplygin "for the best original work on theoretical research in the field of mechanics." And one of the lunar craters bears the Chaplygin’s name.