The "Salvacoste" (Coastsaver)
About the middle in the 19th century, an officer of the Austrian Marine Artillery conceived the idea of employing a small boat carrying a large charge of explosives, powered by a steam or an air engine and remotely steered by cable to be used against enemy ships. Upon his death, before he had perfected his invention or made it public, the papers of this anonymous officer came into the possession of Capt. Giovanni Luppis.
He envisioned a floating device for destroying ships that would be unmanned and controlled from land, while the explosive charges would detonate at the moment of impact. His first prototype was one metre long, had glass wings, and was controlled via long ropes from the coast. It didn't succeed due to primitive implementation.
The second model was built with a clock mechanism as the engine for the propeller. The explosives were in the stern and were ignited through a pistol-like control, which in turn was activated through the bow, the sides or the mast. It had two rudders: one turned to the right, the other to the left, that were moved by ropes/wires from land. After numerous experiments, this design, marked '6 m', finally performed well enough. He nicknamed it 'Salvacoste', Italian for "Coastsaver".
In 1860, after Luppis had retired from the Navy, he managed to demonstrate the '6 m' design to the emperor Franz Joseph, and it was a success, but the naval commission refused to accept it without better propulsion and control systems.
Read more about this topic: Giovanni Luppis