The Kaiten Type 4 followed on from the abandoned Type 2, and used the same basic hull design, engine and payload. Instead of hydrogen peroxide, its engine ran on pure oxygen. Engineers estimated that the oxygen consumption of this unit, in reaching 40 knots, would be extremely high, severely limiting its range, and in this they were proved correct. In the event, no Kaiten Type 4 was ever issued for combat use. In trials its maximum sea speed was only 25 knots. Interestingly, for training purposes, by removing several of the oxygen tanks room was found to accommodate up to four men.
Kaiten Type 4 Specifications:
Length: 16.5m (50.32ft)
Diameter: 1.35m (4.12ft)
Payload: 1800kg (3960lbs) HE
Total weight: 18.17 tonnes (17.87 long tons)
Speed/Range:
62,000m (67,828yds) at 20 knots
50,000m (41,572yds) at 30 knots
27,000m (29,538yds) at 40 knots
(Performance figures as per the original estimates)
Captured Type 4 Kaiten can be viewed in the Washington Naval Yard, at the Bowfin Museum in Honolulu, and in Gosport, England.
Since there was a surplus of Type 92 electric torpedoes, it was decided to convert them to Kaiten Type 10. The torpedo was divided into two halves, and a centre section with cockpit was welded on, with a streamlined fairing to cover the joins. Since the Type 10 was intended for use from land bases, only a top hatch was fitted.
The area of the control surfaces was increased, and these were under the direct control of the pilot. When the motor stopped, the Kaiten rose to the surface, and when restarted, the pilot controlled the immersion using the diving rudders. He was supplied with one periscope of the type used in the midget submarines, but it was fixed. Fewer than six Kaiten Type 10 were produced before the war ended, and none were used operationally.
Kaiten Type 10 Specifications:
Length: 9m (29.5ft)
Diameter: 53cm (20.64in)
Payload: 300kg (600 lbs) HE
Total weight: 3.05 tonnes (3 long tons)
Speed/Range:
35,000m (38,290yds) at 9 knots
A surviving example of the Type 10 Kaiten can be seen in the Yamato Museum in Kure.
Inspired by the SLC and Chariot, the armed forces of many countries have designed different types of ‘human torpedo’ since the Second World War, for covert missions. The popular growth of tourist scuba-diving has also led to their development for peaceful recreational use. The introduction of modern scuba diving gear has also greatly simplified the operators’ task, compared with wartime breathing apparatus.
CHAPTER 3
Der Küstenbrander, the inspiration for Whitehead, and others
In the 1860s there appeared an invention with the germ of a good idea, even though the initial form would prove completely unworkable. In around 1860, retired Fregattenkapitän Giovanni de Luppis of the Austrian navy was shown papers produced by an unnamed Austrian officer in the marine artillery, for an exploding boat which could be brought into contact with an enemy ship. De Luppis thought this would be a good idea, and spent several years developing it, eventually coming up with a prototype model of what he called his ‘Küstenbrander’.
‘Küstenbrander’ in English translates as ‘coastal fireship’. Fireships had been used in naval warfare for centuries. Their most notable exploit had been the scattering of the Spanish Armada off Calais in 1588, which led to the disintegration of the fleet and thwarted the invasion of England. In the days of wooden ships with tarred decks and vast spreads of canvas, the approach of a fireship loaded with combustible materials and gunpowder was viewed with dread. They were most profitably used in attacking a fleet at anchor or in harbour, for the vagaries of wind and waves worked against their employment on the high seas.
At about the same time as Luppis was constructing his first feasibility model, the name Küstenbrander was also used by the submarine pioneer Wilhelm Bauer for his third submersible project, offered to the Royal Prussian war and naval ministry at the end of 1864. For his third essay, Bauer proposed armament, but no torpedoes. His project was not taken up. Both Küstenbrander designs used the principle of the fireship but tried to employ them in the opposite sense, to defend a coastline against a hostile fleet.
Unlike Bauer, Luppis actually produced his Küstenbrander. The working model was built of wood, and powered by a clockwork motor. (Bauer had planned to power his version of the Küstenbrander with an ingenious closed-circuit engine, a kind of gas turbine using paraffin and oxygen generated from manganese dioxide.) The power plant of Luppis’s design is often criticised as the main limiting factor, but at that time powerful, wound spring-operated mechanisms were becoming commonplace in large clocks for ecclesiastical and public buildings. They were capable of reliably storing and releasing energy. They would suffice for the reduced scale demonstration model. What they would not be capable of was high-speed propulsion in the full-sized device.
The weapon aspect was workable enough, as far as it went: an explosive payload detonated by a percussion pistol coming into contact with the waterline of the target vessel. De Luppis appears to have completely ignored the fact that line-of-battle ships would henceforth be clad with thick plates of armour at the waterline. To arrange for the necessary contact to take place, de Luppis proposed to steer his boat from the shore by means of tiller ropes.
He offered his model to the navy officials in Vienna, who felt that he had the basis of a good idea, but that at that moment it was unworkable. They suggested he cooperate with an established marine engineer to develop it further. Since the foremost marine engineer in the Austrian empire at that time was Robert Whitehead, de Luppis visited him at Fiume and they set up a partnership to develop de Luppis’s brainchild.
Whitehead was bitten by the bug of this new idea, and spent considerable time trying to increase the power output and improve the complicated steering arrangements. But however hard he tried, he realised that he would never be able to overcome the two fatal drawbacks of the Küstenbrander. First, it ran on the surface at slow speed. It remained visible to its intended victim, whose crew could either fire at it, steer clear of it or, because of the Küstenbrander’s pathetic lack of power, simply fend it off as it came near. Second, it lacked a realistic radius of action, because of its source of motive power. Having explained this to de Luppis, Whitehead ended their partnership.
The following description makes use of the model in the Vienna Military Museum and a second model built for an exhibition in Rijeka in 2008. The Küstenbrander has a mast, for auxiliary sail power. On either side of the hull are fastened strange bolsters much like the fenders on tugboats. Probably they are cork-filled buoyancy aids to keep it afloat in the face of defensive gunfire. The propeller is not clearly visible in this photo, but from another old photo it appears to have had two broad blades. Behind the propeller is a fixed keel board, and hinged at the rear of this is a curious V-plan rudder in the form of two vertical boards joined at their front faces, worked by tiller cables on the transom connected to the shore. The arming mechanism is worked by a third tiller rope from the shore, passing along the top of the hull to the curious fitting behind the prow, which has a lever weighted by a ball to set the exploder by some devious means. The curved vertical arm has to be the exploder striker. To either side of amidships outrigger arms extend, braced to the bow by wires. Their only obvious purpose would be to try to ensure that if the little vessel struck its target at an angle, the outriggers would attempt to swing it round so the bow striker could come into contact. There is a large handle on the starboard side between the outrigger and the stern, which would have been used to wind the clockwork mechanism. The whole arrangement appears amateurish in the extreme, and one can only wonder at the patience of Whitehead, an experienced marine engineer, faced with this contraption.