Date: 1876Inventor: Louis BrennanCost: £110,000 (£136m in today's money)
By the middle of the 19th Century naval warfare tactics had developed in such a way that there was a pressing need for shore-based counter-attacking weaponry. Harbour defence was becoming critical as the range and power of ships' guns increased. Although Louis Brennan had once thought his fish-shaped wire-guided missile to be suited for shipboard launching, eventually it would be the standard British port defence, operating in eight locations over the period 1890-1906.
Brennan's 'fish' torpedo may not have been the first guided missile – the Irish inventor's technology was pre-empted by John Ericsson, John Louis Lay and Victor von Scheliha – but it was without doubt the first practical system of its kind, due to its range (1,800m) and speed (27 knots). The missile was propelled by an arrangement of wires and winding gear that is said to have its origins in the moment when Brennan, idly toying with a reel of cotton, observed that if the thread was pulled sharply the reel would move away from, rather than toward, the operator. This, he decided could be the basis for a propulsion system that was required over limited range where no return journey was required.
The application that suited the technology was the explosive missile. Brennan quickly set about drafting the engineering drawings for his invention with the mathematical assistance of Melbourne University lecturer William Charles Kernot. Trials in Australia drew interest from the Admiralty and eventually the technology was brought to Britain for trial, where the Admiralty concluded that while the technology did not suit shipboard launching, there was a potential for shore-launched harbour defence.
The key components of the missile design are two interior steel drums each carrying several miles of high-tensile steel wire. These were connected through a differential gear to the twin in-line contra-rotating propellers. Differences in drum rotation speed operated as a rudder, while the twin wires from the drums passed out through the tail shaft. Small steel rings prevented the wires from separating as they were paid out.
Meanwhile, back on shore, the other ends of the wires were connected to twin winding engines, where the speed could be finely adjusted in order to provide sensitive steering control and so guide the missile to the target.
The officer in charge of guiding the missile stood on top of a 12m-high telescopic steel tower with a pair of binoculars and a keyboard that controlled the relative speeds of the two wires. With visual reference coming from a flag or light just above the surface (the torpedo maintained a depth of 12ft) the officer could achieve a high degree of accuracy. Reports from the Admiralty reveal that the operator successfully hit a floating fruit basket at 2,000 yards, while demonstrating the ability of the torpedo to turn through 180 degrees and so attack a ship from the off side.
One of the most outstanding features of the Brennan torpedo was the cost. Brennan had enlisted a business partner, JR Temperley, who managed to extort £110,000 out of the War Office, when Brennan would have happily settled for a third of this. Exactly how much this figure is in today's money is debatable, but conservatively it would be a minimum of £136m. At the time this caused a public outcry, especially as the previous weapon system procured by the government – the Whitehead torpedo – had come in at little more than a tenth of the cost.