Louis Brennan – inventor of the guided missile

Louis Brennan - He loved puzzles and finding out how things worked. He invented the world's first guided missile. He also helped develop the helicopter and monorail. Image copyright Ireland Calling
Irish inventor Louis Brennan

Louis Brennan was a mechanical engineer and one of Ireland’s most prominent inventors.

More great Irish scientists

He worked on the development of the helicopter and monorail, but his biggest success was inventing the world’s first guided missile. This was a kind of torpedo that could be fired underwater and controlled remotely using a wire.Louis Brennan Image copyright Ireland Calling

Brennan loved how things worked

Brennan was born in 1852 in Castlebar, County Mayo, Ireland. He moved to Melbourne, Australia in 1861. As a child he loved puzzles and finding out how things worked. When he found out how his toys worked, he would think of alternative uses for them.

When he left school he became an engineer. He learnt his trade working for Alexander Kennedy Smith who was a renowned mechanical engineer and an officer in the Victoria Volunteer Artillery Regiment. He later became Mayor of Melbourne.

Idea for a steerable torpedo

In 1874, young Brennan first came up with the idea for a steerable torpedo. Surprisingly, it was a cotton reel that inspired his idea.

He realised that if you tug the cotton from underneath, the reel would move in the opposite direction. The faster the cotton was tugged, the faster the reel would move. He thought of things that needed to move fast and not return.


When he realised the sister outfit of his employer’s regiment was the Victoria Torpedo Corps, he put two and two together and developed his first guided torpedo.

He spent the next few years working on the invention after receiving a substantial government grant.

Brennan returned to Ireland

In 1877, he patented the Brennan torpedo. He went back to Ireland to test the concept in County Cork.

In 1880 he took his invention to the British War Office, which saw its potential for defending harbours and channels. They purchased the patent for £100,000 (about £7.5m in today’s money) and Brennan became superintendent of the Brennan Torpedo Factory.

The range of the missiles was limited by the length of the wire used to guide them but they were able to reach up to 3km. They contained explosives and the British navy used them to defend their harbours in Britain, Ireland, Hong Kong and Malta.

Other inventions for the British military


Brennan also worked as an inventor for the British military. He was interested in transport and created an innovative monorail system that was kept balanced using a gyroscope. He demonstrated his invention without any problems but it was never taken on due to fears that it could fail.

He suffered a similar disappointment when he spent seven years working for the air ministry trying to invent a workable helicopter only for the government to stop funding the project. He died in 1932, aged 79, after being hit by a car. His papers are archived in Gillingham library.

Men and officers on Brennan gyrocope car Image copyright Ireland Calling
Irish scientists

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