Konstantin E. Tsiolkovskii, at 16, imagined a spaceship that harnessed centrifugal force; Tsiolkovskii, the father of cosmonautics, would also imagine multi-stage rockets, liquid fuel, orbiting stations, space suits, and ecologically independent colonies capable of intergalactic travel. Tsiolkovskii saw space travel as inevitable: “Earth is the cradle of civilization,” he wrote, “but one cannot remain in the cradle forever.”
