who developed the theory of space flight. He published the first practical paper on astronautics in 1903, dealing with space travel by rockets using liquid propellants, such as liquid oxygen.

Tsiolkovsky was born in the Spassk district and had little formal education; he was deaf from the age of ten. He never actually constructed a rocket, but his theories and designs were fundamental in helping to establish the reality of space flight.

In 1883 Tsiolkovsky proved that it is feasible for a rocket-propelled craft to travel through the vacuum of space. He calculated that in order to achieve flight into space, speeds of 11.26 kps or 40 232 kph would be needed—the escape velocity for Earth. Known solid fuels were too heavy, so Tsiolkovsky worked out how to use liquid fuels. He also suggested the ‘piggyback’ or step principle, with one rocket on top of another. When the lower one was expended it could be jettisoned (reducing the weight), while the next one fired and took over.