Journal of the Royal Naval Scientific Service. Volume 27, Number 2 ...

Torpedo History: Kirby 95
hydrate, 20/ ethyl alcohol and 05 gram per
litre of potassium copper cyanatc, K_Cu(CN),:
this latter being added to assist ignition. The
fuel was Decalin (decahydronaphthalene).
Combustion was started by mixing the Helman,
fuel and hydrogen peroxide in the combustion
pot. Once fired, the flow of helman
was cut off and the fuel and peroxide burnt
continuously at a temperature of about 2,300°.
Because of the difficulty of storing Helman it
was arranged that the copper salt was added
to the catalyst just prior to mixing with the
peroxide. The Helman and fuel had to be
admitted to the combustion pot slightly before
the peroxide. If the peroxide arrived first it
decomposed explosively into water and oxygen
giving up about 660 calories per lb. which is
sufficient to convert the water to steam. A
complex system of cam-operated valves
ensured that the fluids were mixed in the
appropriate fashion. Table 13 below summarises
the characteristics of two German
peroxide weapons and compares them with the
standard wartime British Mk. 8 torpedo.
It should be noted that the British B-cycle
engine is far more efficient than all other
weapons with the exception of the STEIN-
WAL. The relatively low range of the Mk. 8
is due to the low weight of oxygen carried
compared with the torpedo weight. Such is
the advantage of a dense low pressure oxidant
such as hydrogen peroxide.
It will be noted from the table that the
Germans changed from radial reciprocating
engines to turbines during the war. The reason
was primarily to eliminate oil from the exhaust
and render the weapons completely
trackless. Many types of turbine were tested
and the finest was that fitted to the STEIN-
WAL. It was rated at 500 h.p. and had a
speed of 30,000 r.p.m. and was actually
machined from a solid steel disc by a machine
developed at the firm of Askania, Berlin.
Another revolutionary feature was a cardan
gear on the driving shaft which, with an internally
toothed flywheel ring, revolved in the
opposite direction thus preventing initial roll
on firing 13 '". The exhaust, such as it was,
bubbled out through a perforated ring around
the engine compartment. The bubbles quickly
dissolved. One claim for this type of exhaust
was a reduction of radiated noise from the
engine due to the bubble screen.
The long range of the Steinwal was developed
solely for the pattern running capability.
Complex patterns could be run through a con-
OF
COURSE
CONVOY
FIG. 39. German " LUT " pattern running.
voy giving little chance of avoidance because
of the numerous and devious course changes.
A special gyro, the LUT, was made to allow
the weapon to follow the programmed path.
Fig. 39 shows a typical LUT track.
The Germans experimented with peroxide
weapons using the jet idea and claim to have
achieved 1,310 yards range and 45 knots.
Table 14 summarises the experimental weapons
of the last war together with a few operational
types.
The popular impression that peroxide torpedoes
were the major objects of German wartime
research tends to over-shadow the fact
that a large proportion of scientists favoured
pure oxygen rather than hydrogen peroxide,
after the manner of the Japanese. Teams of
scientists travelled to Germany from Japan
by U-boat to advise the Germans. However,
by the end of 1943 the oxygen work was falling
behind the peroxide developments and the
former was cancelled. The oxygen work was
based on a closed cycle system whereby the
exhaust gases were fed back into the combustion
pot to act as diluent; any build-up of
pressure being released by exhaustion of the
steam and CO.., the soluable products of combustion.
Experiments on this system began in
1930 using a car engine and in 1937 the Junkers
Aircraft and Engine Company produced
the huge experimental M5 torpedo. Measuring
29-6 in. in diameter and over 36 ft. in length,
its engine developed some 600 b.h.p. but the
weapon was a failure. Every test model sank
on trials and the project was given up.
Tests at the end of the war on the surviving
Junkers engines showed that the M5 weapons
would have achieved 26,000 yards range at a
speed of 40 knots.