The US Navy called for this latest homing torpedo to resolve problems with the older Mark 50, which had been given high performance (at high unit cost), to pursue deep-diving rapid Soviet submarines during the Cold War period, and the Mark 46, which was unsuitable for use in the shallow water environment of the littoral actions the US Navy sees as one of its primary roles in future.
By combining the homing systems and hollow-charge warhead of the Mark 50 Barracuda with the Otto fuel II propulsion system from the older Mark 46, Raytheon produced the Mark 54 Mako, originally known as the lightweight homing torpedo (LHT), at a relatively low unit cost compared with small production run European rivals. It has a top speed of 40 knots, which is adequate to hunt the diesel-powered submarines the US Navy is likely to encounter in coastal waters. Nuclear boats are too large to hide there, and cannot bottom in shallow water like the diesel boats, because of fears of blocking vital cooling water inlets with seabed sediment. The Mark 54 shares with the latest Mark 48 ADCAP heavyweight a sophisticated software and hardware package built around a PowerPC 603e chip.
With this weapon Robert Fulton’s ideas of the mine and the torpedo came full circle. Fulton had envisaged his moored mines returning to the surface at preset intervals for routine maintenance. The Mark 60 ‘enCAPsulated TORpedo’ could be laid by plane, ship or submarine at depths down to 3000ft (910m) where it would lie in wait for the signature of a passing submarine. The aluminium casing would then open and deploy a standard Mark 46 homing torpedo which would begin hunting the target submarine.
Part II
Torpedo Launchers and Delivery Systems
CHAPTER 9
Spar Torpedo Boats, Drop Collars, Launch Troughs and Rails
SPAR TORPEDO BOATS
Spar torpedoes were first carried into action during the War of 1812, but they had to wait fifty years before scoring their first successes, during the American Civil War. They were fitted to Confederate semi-submersible torpedo boats known as ‘Davids’, intended to take on and defeat a new Goliath, and then to the submersible H L Hunley, as described in Part I.
A spar torpedo consisted of a bomb on a long pole or spar, carried by a small, fast, low-lying boat. Under the cover of night or fog the torpedo boat stealthily approached an enemy ship and detonated the bomb close to the vulnerable underwater hull. This sounded simple enough in theory, but experience had shown these missions to be suicidal under the best of circumstances. Once detected, the little torpedo boats were highly vulnerable, and even if the torpedo was deployed correctly, its charge was often too small to cause any significant damage. Spar torpedo boats were, in the eyes of one American observer, little more than ‘a waste of good men’.
Stung into retaliation by the Confederate successes, the Union decided to build a large spar torpedo boat. Originally called Stromboli, on 19 November 1864 she was renamed Spyten Dyvil after the district of that name in New York. Displacing 207 long tons, the vessel was constructed of wood with the deck and hull sides covered in iron armour. Her engines propelled her at a maximum speed of 5 knots, she carried a crew of twenty-three officers and men, and her sole armament was a retractable spar for placing torpedoes containing 60lbs of fine black powder.
The bow was fitted with a pair of iron clam-shell doors. Inside these doors was a sluice gate leading to a square iron tank which could be pumped dry by a centrifugal pump. At the rear of the tank was a spherical bearing carrying the torpedo-positioning shaft, which could be raised and lowered in order to correctly place the torpedo according to the chosen target.
The attack sequence was as follows. The manhole in the top of the iron tank was opened to allow loading of the torpedo head in its holder at the front end of the placing spar. The manhole would be closed. Then the bow flaps, followed by the sluice gate, were opened, allowing water to flood the tank. The spar would be run out beneath the target vessel, and raised or lowered to ensure that the torpedo head was placed beneath the target’s hull. The spar would be retracted, leaving the torpedo in place. Retracting the spar would activate the fuse, exploding the torpedo at the usual distance of 20ft. The bow flaps would be closed, the sluice gate shut, and the iron tank pumped dry, ready to reload a following torpedo.
This machinery appeared to work extremely well, and Spyten Dyvil used it to clear obstructions in the James River. She lasted up until 1880, when she was scrapped.
On 17 October 1870 David Dixon Porter became Chief of the Bureau of Navigation of the US Navy, and decided to move on from the ‘monitor’ era of the Civil War. Monitors, he felt, were poor sea boats, and despite their heavy armour they remained vulnerable to spar torpedoes attacking their unprotected underwater hulls. Impressed by the Confederate spar torpedo boats and the Union’s own Spyten Dyvil, Porter decided to continue to develop the spar torpedo boat concept in defiance of the ‘monitor’ supporters and the reluctance of Congress to fund new warships in the post-war period.
He wanted double-hull torpedo boats built of iron with watertight compartments to minimise damage, especially from the explosion of their own torpedo at relatively close range. The spar itself would copy the successful mechanism patented by William Wood and John L Lay for the Spyten Dyvil. Porter intended his torpedo boat to fight bows-on, so he included a 15in Dahlgren gun behind hatches in the bow. Ahead of the Dahlgren extended an enormous ram 24ft long, containing the steam operating gear for the spar and ending in a valve through which the spar and torpedo would pass, to project a further 30ft. Gatling guns were mounted on the bulwarks. The double hull could be flooded to lower the vessel when attacking, the deck structures were kept to a minimum, and the funnel was arranged to telescope to half its height, to increase the stealth capability of the boat.
To enable her to make use of her ram if the spar torpedo failed to deal a fatal blow, Alarm was propelled by a Fowler wheel, a kind of horizontal paddle wheel with pivoting blades, which offered the possibility for her to make extremely rapid turns, essential for a torpedo ram. The same Fowler wheel, however, proved to be her Achilles’ heel, reducing her top speed to a pitiful 9 knots, which completely negated her value as a ram ship. Despite efforts to improve on her speed, irrespective of the efficiency or otherwise of her torpedo equipment, as a ship she proved a failure. Used for experiments, she was laid up in 1874, and finally scrapped in 1898.