Steam cannon

A steam cannon is a cannon that launches a projectile using only heat and water, or using a ready supply of high-pressure steam from a boiler. The first steam cannon was designed by Archimedes during the Siege of Syracuse.^[1] Leonardo da Vinci was also known to have designed one (see the Architonnerre).

The early device would consist of a large metal tube, preferably copper due to its high thermal conductivity, which would be placed in a furnace. One end of the tube would be capped and the other loaded with a projectile. Once the tube reached a high enough temperature, a small amount of water would be injected in behind the projectile. In theory, da Vinci believed the water would rapidly expand into vapour, blasting the projectile out of the front of the barrel.