In the 1920s, visionaries in the United States, Germany, the Soviet Union, and elsewhere began developing liquid-fuel rockets with an eye toward space travel. Up to that point, the rocket had not changed much since its invention in China around the year 1000: a small artillery or fireworks device using gunpowder as a fuel.

Within a couple of decades, rockets and missiles had begun to alter the course of the 20th century. With the emergence of new liquid-fuel and solid-fuel rocket motors, jet engines, and complex guidance systems, nations built long-range weapons to threaten each other and weapons to defend against those threats. But rocketry also began to turn the dreams of its visionaries into reality, as nations used launch vehicles to send satellites, telescopes, robotic spacecraft, and human explorers and pioneers into space.