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

Torpedo History: Kir by 99
for a new 25-knot active /passive helicopterborne
weapon of 14 in. diameter. The project
was pursued and by 1957 a prototype passive
weapon was running using the basic Mk. 30
motor with a new homing system. The active
electronics were bench-tested and ready to be
fitted but in 1957 a Staff decision was made
to stop all air-dropped weapons and concentrate
on submarine and ship torpedoes. As a
result it was abandoned along with a 12 in.
weapon developed " unofficially" a year or
two earlier code-named NEGRESS.
Also abandoned at this time was the illstarred
PENTANE, one of the best engineered
weapons so far produced in Britain or America.
PENTANE was born in 1947, following the
collapse of the fabulous (literally!) Z-weapon
programme. The requirement was set down
for an active homing air-dropped weapon to
cope with submarines of potentially enormous
propulsion improvements likely to be found
in the 1950's and beyond. Work was initially
concentrated at Teddington and T.E.E.
engineers were moved from Greenock.
The weapon was designed to run at 30 knots
and be capable of catching high-speed submarines.
The carrying aircraft were the
Gannet, Sturgeon, Lancaster, Shackleton and
flying boats. It was not until 1954 that a final
design was selected on the basis of extensive
research carried out over the preceding six
years. By this time however the fixed wing
aircraft capable of carrying a 21 in. weapon
were being withdrawn from service and the
helicopter was being considered as the prime
torpedo delivery system. Instead of cancelling
the project and starting a new lightweight torpedo,
the work was allowed to drop from the
top priority that it had enjoyed up to then and
it continued until 1958 at which point it was
finally cancelled. The cancellation was not,
rather unexpectedly, due to lack of a suitable
carrier but due to an assessment of the
weapon's performance. This showed that the
search rate was too slow for the targets then
likely to be available* 42 '. Pentane died therefore
because it was too late in development,
not initially well matched to the future carriers
and not adequately matched in homing
performance to targets' capabilities.
Excluding these failings, the weapon itself
was well engineered, as Fig. 43 shows from
the tail unit alone, and as the first British
active torpedo it provided valuable experience
for future weapon considerations.
FIG. 43. Pentane tail.
The sad facts of the PENTANE affair were
(a) that the potentially very successful Mk.
30 mod 1 was cancelled because of Pentane's
top priority and U.S. Mk. 43
weapons were purchased instead,
(b) that other potentially worthwhile projects
were held back for the same reason,
and
(c) that £1,726,000 were spent on the project;
more than the total spent on the
only two successful projects by a factor
of two.
The initial doubts over the propulsion performance
of Pentane gave considerable
impetus to the development of silver/zinc
batteries and thermal propulsion systems which
have proved of great value in recent years.
With the cancellation of Pentane, the
Naval Staff decreed that Britain would in
future concentrate on ship and submarinelaunched
weapons. The 21 in. BIDDER (Mk.
20) had already entered service as a result of
a development programme extending from
1945 and wire-guidance work had also continued.
Initially, trials of wire-guidance were
carried out by paying captured German wire
(from their SPINNE weapon) out from Mk. 11
weapons. This work was carried out with the
help of Post Office engineers. The work was
pursued under the code-name MACKLE with
Vickers Armstrong playing a large part. In
1956, the contract with industry was terminated;
the result being a very complex guidance
system applied to Mk. 20 weapons. The system
was simplified and improved and renamed
GROG. This weapon was a lengthened version
of the Mk. 20 with a drum of guidance wire
carried in the extra length. A dispenser is