The Brennan torpedo was a torpedo patented by Irish-born Australian inventor Louis Brennan in 1877. It was propelled by two contra-rotating propellers 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 away, at speeds of up to .
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.
Description
thumb|left|Launching a Brennan torpedo
The Brennan torpedo was similar in appearance to more modern ones, apart from having a flattened oval cross-section instead of a circular one. It was designed to run at a consistent depth of , and was fitted with an indicator mast that just broke the surface of the water; at night the mast had a small light fitted which was only visible from the rear.
Two steel drums were mounted one behind the other inside the torpedo, each carrying several thousands yards of high-tensile steel wire. The drums were connected via a differential gear to twin contra-rotating propellers. If one drum was rotated faster than the other, then the rudder was activated. The other ends of the wires were connected to steam-powered winding engines, which were arranged so that speeds could be varied within fine limits, giving sensitive steering control for the torpedo.
The torpedo attained a speed of using a wire in diameter but later this was changed to to increase the speed to . The torpedo was fitted with elevators controlled by a depth-keeping mechanism, and the fore and aft rudders operated by the differential between the drums.
In operation, the torpedo's operator would be positioned on a high telescopic steel tower, which could be extended hydraulically. He was provided with a special pair of binoculars on which were mounted controls which could be used to electrically control the relative speeds of the twin winding engines. In this way he was able to follow the track of the torpedo and steer it with a great degree of accuracy. In tests carried out by the Admiralty the operator was able to hit a floating object at and was able to turn the torpedo through 180 degrees to hit a target from the off side.
History
Tomlinson states that in 1874 while watching a planing machine worked by a driving belt, Brennan stumbled on the paradox that it was possible to make a machine travel forward by pulling it backward.
Beanse expands Brennan’s observation of the driving belt powering the planing machine was taut and the non-driving side was slack. Brennan reasoned that if one dispensed with the non-driving side it would be possible to transfer energy to a vehicle and power it from a static power source. The concept was to place a drum of fine wire in the vehicle in place of the belt. The wire was attached to an engine to wind it in, rotating the drum that then propelled the vehicle away from its start point. He demonstrated this by means of a cotton reel, with a pencil thrust through the hole in the centre. By resting the ends of this pencil on two books and unwinding the cotton by pulling it from underneath he caused the reel to roll forward, the harder he pulled the faster the cotton unwound and the quicker the reel travelled in the opposite direction.
Brennan began making rough sketches of such a torpedo, and as the concept developed he sought the mathematical assistance of William Charles Kernot, a lecturer at Melbourne University.
We have now completed or in progress 7 installations viz. Thames (Cliffe), Medway (Garrison Pt), Portsmouth (Cliff End/Fort Albert), Plymouth (Pier Cellars/Cawsand Bay), Cork Harbour (Fort Camden), Malta (Tigné and Ricasoli). Further sites proposed as funds become available at Plymouth (Bovisand), Milford Haven, Clyde, Forth, Falmouth, Hong Kong, Singapore and St Lucia.
The first seven were completed but out of the other eight only the one at Hong Kong was completed. The plans for two installations at Dale Point and Great Castle Head, Milford Haven were drawn up but not carried out.