What Leonardo da Vinci concept used steam pressure to propel a cannonball?

Leonardo da Vinci’s steam-cannon concept used steam pressure to propel a cannonball.

The design is commonly called the Architonnerre, a name derived from Greek and Italian terms associated with force and artillery. Leonardo’s version placed a cannon barrel beside a heated chamber. Water entering the hot chamber would turn into steam, and the resulting pressure was intended to launch a projectile.

The concept belongs to Leonardo’s studies of military machines and thermal force. It was not a conventional gunpowder cannon, because its proposed propulsion came from expanding steam rather than an explosive charge. The mechanism would have been difficult to control safely with fifteenth-century materials.

No reliable evidence shows that Leonardo built and successfully fired this machine. The design is therefore best understood as an inventive experiment in applying steam pressure to artillery. It also predates the practical development of steam engines by several centuries.