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Loading contentThe founding relation of astronautics, derived by Konstantin Tsiolkovsky in 1903: the velocity change a rocket can achieve equals its exhaust velocity times the natural logarithm of the ratio of its starting mass to its empty mass. Because the mass ratio enters logarithmically, reaching high Δv demands either very high exhaust velocity or an impractically large fraction of propellant — the 'tyranny' that shapes every mission design.
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