Rockets were originally invented not to send things into space, but to shoot enemies with. Their effectiveness in warfare was demonstrated for the first time by the Chinese in the 13th century, when they used them against the Mongol invaders and successfully kept them away for months. These early rockets, known as ‘fire arrows’, were similar to bottle rockets we use today in firework celebrations, only larger. A short tube was filled with gunpowder, closed at one end and attached to a long stick. When the powder was ignited, hot gases and smoke escaped out of the open end producing a thrust that carried the rocket across no man’s land and towards the enemy.