The “Really Bloody Big Cannons”, or “R.B.B.C.s”, were devices used by the Wellsians in 1897.
The “Really Bloody Big Cannons”, as the names implied, were a handful of huge cannons the Wellsians constructed in 1897 to aid in their hostile invasion of Earth. They were not weapons, but instead could be used to fire inhabitable bombshell-like pods from Mars to Earth with the Wellsians inside.
Behind the scenes
The R.B.B.C.s appear in the 2019 webcast The Wellsians.