The founder of cosmonautics Konstantin Eduardovich Tsiolkovsky.
Tsiolkovsky carried out extensive research and calculations related to the problems of the departure of an interplanetary rocket beyond the limits of gravity, its further movement in free space and the possibility of returning to Earth. He determined the optimal conditions for such flights in a variety of options and with different initial initial data.
Tsiolkovsky was the first to investigate trajectories and characteristics of various motion orbits, orbits of space rockets during takeoff from Earth, as well as from the surface of planets and asteroids.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.