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

Torpedo History: Kirby 83
By 1918 this work, carried out by the Sperry
Gyroscope Company, had come to a halt. The
United States Navy were still maintaining an
interest however and a design study in 1918
gave rise to an 18 in. diameter weapon in 1919.
This work carried on slowly without much
official support until 1931 when it ceased
altogether.
The Germans, on the other hand, had successfully
produced an electric weapon by 1918
and samples were issued to the fleet but never
used because of the timely intervention of the
Armistice. This weapon was capable of 28
knots to a range of 2,000 yards but after the
Great War development continued in Sweden
and Germany. The first indications that the
Germans were using electric torpedoes came
right at the start of the war. The Royal Oak
was believed sunk at Scapa Flow by an
electric weapon in 1939 and an electric weapon
was recovered from the child evacuee ship
s.s. Volendam; the torpedo fortunately being
a " dud". The first complete sample was
obtained in the early days of 1941 from the
captured submarine V'.570.
The weapon and its motor are described in
detail elsewhere 1 -'" but, in view of the rather
novel nature of the weapon and its subsequent
importance in the development of the homing
torpedo a short description is justified here.
Known as the G7e, the weapon had a range
of 8,000 yards and a speed of about 29 knots.
The weapon had to be kept at 30°C for maximum
range. Firing when cold reduced the
range by about 1,400 yards. The batteries
were heated only when the submarine was
patrolling a target area. The batteries were
lead-acid types and 26 cells each of 18 plates
were used; the total battery weight being
about 1500 lbs. The cells in each of the two
batteries were connected in series. The motor
was an 8-pole series wound D.C. machine,
rated at 91 volts, 950 amps at 1,755 r.p.m. The
weight of the motor was about 250 lbs. This
same motor was used with only small modification
in all the German electric weapons.
In other details the weapon was similar to
its "thermal brother". The TNT/HND/A1
warhead weighed 660 lbs. and the depth gear
was conventional bellows and pendulum.
Three forms of weapon existed. The earliest
type, the T2, was in service at the start of the
war and had a range of 5,400 yards at 30
knots. The T3 and the T3a had the performance
of 8,000 yards quoted above.
Apart from the homing torpedoes, of which
we shall see more later, several special adaptations
of the G7e appeared 127 '.
The requirement for pattern running electric
weapons resulted in a redesign of the battery
such that 125 amp. hours was obtained
instead of the 93 amp. hours from the
13T210 battery fitted in the basic G7e. This
pattern running weapon achieved 8,200 yards
range and 30 knots. By reducing the battery
size a low power torpedo was produced as the
Tib which, when fitted to a T3, became the
" Marder ", a tandem weapon carrying a man
as guidance system. We shall return to this
and other man/torpedo combinations later.
The T3b, with its reduced performance of
4,400 yards and 185 knots was also fired from
midget submarines. Perhaps the most curious
of all the electric torpedoes developed during
the last war was the Dackel, known also as
the " slow-worm " or T3d. This had a speed
of nine knots and a range of over 35 miles !
This weapon was fired against ships in harbours
or other restricted areas. It was used
extensively against shipping in Seine Bay.
Basically a pattern runner, the torpedo was
fired into a bay and set to circle or zigzag for
the rest of its four hours of endurance. The
length of " slow-worm " was six feet more
than the G7e making it protrude from the
tubes on surface craft.
Moving on to a higher level of sophistication
we come to the controlled torpedo. Most
successful of these was the very aptly named
Spinne (= spider) which was fired from coastal
stations. A fine insulated wire was paid out
and guidance instructions were transmitted
down the wire to the weapon. By day the
torpedo could be instructed to surface briefly
and by night to flash a lamp in order that the
operator could track its path. Observation
posts were situated high on cliffs and up to
three weapons could be controlled by each
operator. Known also as T10, the weapon
had a range of 5,400 yards and a speed of 30
knots. These weapons were set up along the
French coast in 1944 but appear to have been
of dubious effectiveness. They did inspire the
British work on wire control of torpedoes,
however, which led to the present wire-guided
U.K. Mark 23.
The advantages of electric torpedoes were
(and still are to some extent),
(a) tracklessness, allowing submarine
attacks to be made with stealth,
(b) low cost of manufacture,