Remains of Brennan Torpedo launch tracks

The Brennan torpeod was a torpedo patented by Irish born Australian inventor Louis Brennan in 1877. It was powered by two contra-rotating propellors that were spun by rapidly pulling out wires from drums wound inside the torpedo. Differential speed on the wires connected to the shore station allowed the torpedo to be guided to its target, up to 2,000 yards (1,800 m) away, at speeds of up to 27 knots (31 mph).

The Brennan torpedo is often claimed as the world's first guided missile, but guided torpedoes invented by John Ericsson, John Louis Lay, and Victor von Scheliha all predate it; however, Brennan's torpedo was much simpler in its concept and worked over an acceptable range at a satisfactory speed so it might be more accurate to call it "the world's first practical guided missile".