The principle has been known since Hero of Alexandria. His simple toy was a hollow sphere having four jets which could be filled with water and heated over a flame. When his aeolipile began to eject steam through its jets, it rotated about its axis. Nothing apparently came of this early practical demonstration of jet propulsion.
In 1275, Marco Polo brought back from China stories of rolled cylinders filled with a black substance. When attached to long sticks and ignited, the whole apparatus rose into the air spewing sound and a trail of foul smoke. These gunpowder rockets or “fire arrows” were said to cause bewilderment among men and panic among horses. During this same time period, the art of artillery was beginning in Europe while the Mongols brought rocketry with them in the penetrations of Eastern Europe. A century after Marco Polo’s accounts, gunpowder rockets were used in battle at Chiozza by the Paduans, and again a year later (1380) by the Venetians. Writings on gunpowder rocketry were numerous in Europe during the 16th and 17th centuries.