You guys should do some research before you start slamming each other down.
It was Archimedes, not Aristotle, and he did design a steam powered cannon around 213 BC.
http://www.mlahanas.de/Greeks/war/CatapultTypes.htm
(Some good info about conventional catapults and ballistas on this site too.)
Whether it was actually used or not is unknown, but the device was built and tested in 1981 and seems to have worked. A man named Ioannis Sakas built a 1/5 scale model and shot a cement filled tennis ball 50 meters. The full size cannon would have shot a 20 kg stone about a kilometer.
Here's a photo of the reconstruction
https://www.cs.drexel.edu/~crorres/bbc_archive/steam_cannon_photo.jpg
Here's a copy of the newspaper article (in Greek)
https://www.cs.drexel.edu/~crorres/bbc_archive/steam_cannon_news.jpg
Stephen
(20 kilograms = about 45 pounds
1 Kilometer = about 1100 yards)