Effective as it may have been, by 1906 the whole system was deemed to be obsolete and no longer cost-effective. Long-planned extensions to the existing stations were cancelled. What had happened in the meantime? First, it was hardly a rapid-reaction defence weapon, needing a head of steam to operate the winding drums in the launch station. Given the vast investment in the launch sites, the machinery could have been upgraded to run on internal combustion engines or electric motors. But there were more significant drawbacks.
Its large locations were impossible to conceal and would therefore have all been known to a potential enemy. On the other hand, this would still have a deterrent effect. When launched, the steering flag gave away its course and position to the target. But then knowing it was on the way was different from being able to avoid it, as the Brennan would unerringly follow the target’s evasive manoeuvres. The launch rails, overhead girder and trolleys (see Chapter 18) and the torpedo itself running down the rails could be bombarded by QF guns on an attacking ship. They offered a small target but were easily damaged.
But, finally, the few existing launch stations had involved a significant investment in masonry, armoured lookout positions and machinery, for what was essentially a comparatively small short-range weapon, especially compared to the price of a fixed torpedo tube installation for Whiteheads. And in the intervening years the Whitehead torpedo itself had developed out of all recognition.
THE HOWELL TORPEDO
The Brennan being tied to coastal defence by its use of heavy winches and launch girders, the most serious competitor to the early Whitehead at sea was the American Howell torpedo. A serving US Navy officer, Lieutenant Commander John Howell spent his spare time designing and perfecting a torpedo of his own, which used a completely different mode of propulsion.
Rather than using compressed air and a reciprocating engine to drive his torpedo, Howell settled on a large internal flywheel. This added one unavoidable complication — the need for an external power source to spin the flywheel up to speed. Howell used a steam turbine attached to the starboard side of the launch tube, working through clutches in the torpedo body, to spin the 131lb (60kg) steel flywheel up to launch speed. One slight drawback was that the turbine and flywheel, when at full speed, did produce a certain amount of noise, which might give away a torpedo boat on a stealthy approach — rather like the sound made by the submarine Nautilus in the 1954 movie 20,000 Leagues under the Sea.
There were compensations, however. When the flywheel had reached 10,000rpm, on pulling the firing lever, first the drive clutches were withdrawn, then the torpedo stop latch which held it in the tube was released and, finally, the propulsion charge of black powder was fired, launching the torpedo. The horizontal rudders and the propeller speed regulator were locked for the initial few metres, then the torpedo set off at its preset depth and aimed course.
Howell had discovered that the large flywheel acted like a gyroscope, tending to stabilise the course of his torpedo. If a contemporary Whitehead encountered a strong wave coming from one side, it would tend to be deflected from its aimed course. The Howell, on the other hand, would not be deflected but would be rolled by the wave, a roll which was relatively simple to correct by the swing of the vertical rudder pendulum. So strong was the gyroscopic effect that Howell patented it as representing a major improvement in torpedo control. (As noted earlier, when Whitehead later adopted the idea of the gyroscope, Howell sued him for copyright infringement.) And, of course, the flywheel drive left no wake to give warning of the torpedo’s course and allow the target to take avoiding action.
One idea that was common to both designers was Whitehead’s ‘Secret’, the pendulum to regulate for over-rapid compensation of the hydrostatic depth-keeping device. But the Howell had one more unique feature. To avoid the need for contra-rotating screws, he had used twin inward-turning propellers set horizontally. As the flywheel slowed down in the course of the torpedo’s run, the speed regulator automatically adjusted the pitch of both propellers, to ensure that the Howell maintained a steady speed. Both speed regulator and horizontal rudders were locked out of operation for the initial period of the run, to avoid upsetting the regulating devices on impact with the water.
The warhead nose contained the contact exploder and the safety mechanism. This consisted of a steel four-bladed screw-fan, normally held in the rearward position on the threaded body of the exploder by a shear pin of lead. When the torpedo entered the water, the shear pin broke under the impetus of the screw turning in the water flow, the screw-fan screwed itself forward until it reached a section with no further screw thread, when it was free to revolve without undue resistance to the water flow. The exploder body was now free to move backwards on striking the target, activating the primer and the main charge.
In the event of a miss with a war shot, soluble paper covers dissolved and let water enter two holes plugged by soap. When the soap dissolved in turn, water entered the dry primer and rendered it inert. The practice head, filled with seawater to the same weight as the warhead, had an identical screw-fan nose fixture, to duplicate the characteristics of the warhead. At the end of its run, a soluble cover would allow seawater to enter a pocket containing a cylinder of calcium phosphide. This would emit smoke enabling the position of the torpedo to be spotted for recovery. A depth register recorded the depths attained by the torpedo during its practice run.
From the above, it is clear that the Howell was a workable device with good accuracy. Unfortunately for Lt Cdr Howell, his naval duties did not permit him to fully devote his time to the perfection of his idea. He seems to have begun experimenting in 1870, with an initial model driven by a propeller at both ends. But it was not until thirteen years later, in 1883, during the competition organised at the behest of Congress by the US Navy in order to find a suitable design of torpedo, that his design was virtually finalised. Three years later, Lt Cdr Barber of the Bureau of Ordnance testified before the Senate committee on ordnance and warships to the effect that the Howell’s ‘principal advantages over the Whitehead are directive force, its size and its cost. Its remarkable power for maintaining the direction in which it is pointed, when acted upon by a deflecting force, makes it possible to launch it with accuracy from the broadside of a vessel in rapid motion.’