Home' Asia Pacific Defence Reporter : APDR October 2015 Contents Asia Pacific Defence Reporter OCT 2015 47
overcharge, overload or charging after deep
discharge with cobalt based high energy cells.
(NMC, NCA, LCO).
THE NEED FOR UNDERWATER
Mission scenarios for the Australian Future Submarine
in the north-west approaches, South China Sea and
the Indian Ocean point to durations of up to 70 days,
half of them continuously underwater.
A submarine’s indiscretion ratio is a measure of the
time spent detectable as a proportion of the overall
time on mission. Transits from or to home base on or
near the surface at snorkel depth might be less critical,
but as soon as an area of operations is entered,
remaining undetected becomes vitally important.
Apart from magnetic anomaly detection, the main
sub-surface submarine giveaways are periscope and
snorkel wakes plus the sound of battery charging
generators and their heated exhaust plume. Deeper
down it can be propeller noise, although this is often
disguised by other natural underwater sounds from
sea creatures or coming down from surface waves.
Submarine hunting techniques, apart from dipping
sonars from helicopters and the long sound detection
arrays towed behind surface vessels and other
submarines, are advancing with several sub-hunting
platforms likely to be networked together in the
future for greater detection sensitivity. Unmanned
underwater vehicles are also likely to be swarmed for
submarine detection and subsequent destruction.
LiB is the perfect supplement/complement for an air
independent propulsion (AIP) system. The AIP system
provides long endurance at low power. LiB adds
the flexibility to run at higher speeds. A combination
of LiBs and air independent propulsion techniques
like fuel cells seem to offer the greatest promise for
lengthy silent transits under water. Australia’s future
submarines may be required to travel silently and
deep down for as much as 4,000 nautical miles over
35 days, using their sensors to detect and measure
acoustic information from potential adversaries, as
well as allies, to aid submarine and surface vessel
recognition and discrimination between friends and
foes, should the area become hostile in the future.
GREATER UNDERWATER ENDURANCE
WITH LITHIUM BATTERIES
The energy required to propel a submarine is
proportional to the cube of its speed. In other words,
to propel a submarine underwater at 8 knots requires
eight times the energy to propel it at 4 knots.
As submarine detection technology becomes more
sensitive, the need for a submarine to change position
fairly rapidly when it suspects it has been detected is
evident. Current submarines carry large banks of lead
acid accumulators to provide both endurance and
short burst speed.
This is where the energy density available with LiBs
is seen to be very important in future submarines,
and one of the key LiB development goals is to be
able to retrofit them onto existing submarines. That is
provided fail-safe control systems can be developed
to monitor LiBs state of charge and state of health, so
that the time spent battery charging near the surface
at detectable snorkel depth is kept to a minimum, and
that the charge voltage and current supplied is at an
optimum level. Most importantly, over-charge or over-
discharge situations must not be allowed to develop
for banks of cells or even single ones.
Practical R&D LiB testing observed recently by
APDR at HDW (a TKMS company), Kiel revealed
significant progress is being made, but is not yet
thought to be at the stage for deployment in a new-build
submarine. With the effort going into development
by TKMS in Germany, DCNS in France, and the
Japanese, it is highly likely that by the time Australia’s
Future Submarine detailed design is concluded, LiBs
will be the source of stored electric power.
In fact, the Japanese may be in the lead with their
R&D as they have proposed fitting LiBs to future
Soryu submarines from about 2020, and dropping the
requirement for an air independent propulsion system
as an alternate to drive the submarine’s electric motor
At 4 knots underwater, LiBs can supply twice the
energy in the same space which would be occupied
by conventional batteries and that gives a big range
advantage at that speed. At double that speed
they can supply four times the energy in the same
conventional battery space that would be required to
drive the submarine at 8 knots.
LITHIUM ION BATTERY TECHNOLOGY
This wet cell battery uses lithium ions, rather than
metallic lithium, due to the inherent instability of this
metal despite it offering higher energy density. LiBs
are safe, provided certain precautions are taken when
" Mission scenarios for the Australian Future Submarine in
the north-west approaches, South China Sea and the Indian
Ocean point to durations of up to 70 days, half of them
continuously underwater "
Able Seaman Marine Technician Submarines Catilina Teamoke onboard HMAS Farncombe in the Electrical Equipment Space
and Main Generator Room. (CoA)
17/09/2015 5:21 pm
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