Home' Asia Pacific Defence Reporter : APDR May 2016 Contents typical patrol period of 60-70 days, it provides a lot of
tactical flexibility for the commanding officer.
The aim is not to imitate a nuclear submarine and
never snort: that is simply not practical with current
technology. It is necessary to use a combination of
battery and AIP to go for a period greater than the
battery alone would allow between snorts. For example
this could be to avoid detection when being hunted,
conducting an attack then exiting the scene, or passing
through a choke point.
The mere fact that the submarine has AIP, means
the ASW problem for the enemy is massive. They
simply do not know when it will need to snort again. In
Australia’s likely areas of operation this will create huge
uncertainty in locating the Future Submarine.
Any technology which increases dived endurance,
at the same time reducing the frequency and duration
of snorting at periscope depth for battery recharging
should be welcomed by submarine commanding
officers – though to date the interest shown by the
RAN in AIP has been underwhelming. Remaining
submerged undetected for longer periods improves
tactical mobility, the likelihood of completing the full
mission effectively, and surviving to return home safely.
STEALTH IS THE KEY
There is a definite strategic advantage that submarines
provide for their country. They tie up a disproportionate
amount of a potential or real adversary’s naval and
airborne assets searching for them, as well as having
a very good chance of destroying those sanctioned
Submarine operations have a definite cat-and-
mouse character. The longer a submarine can remain
undetected while moving covertly to its listening post,
or remain stationary there, the better its chances
of collecting useful intelligence. In a declared war
situation, where the submarine will be required to
attack other submarines or surface shipping, destroying
the target then escaping safely is critical.
But as technology to improve submarine underwater
endurance and speed has become available, so too
have methods of submarine detection evolved which
can pin-point them at greater depths and ranges. These
modern detectors now include long trailed sonar arrays
from surface ships or other submarines, deep water
sonobuoys dropped in a pattern from aircraft, and
sonar-equipped unmanned underwater vehicles (UUV).
When a submarine is at periscope depth, sucking in
air for its diesel generators to charge its batteries, it is
probably at its most vulnerable in terms of detection.
Smart radar and optronic systems can remove wave
clutter and identify the wake of anything projecting
above the surface from a submarine. Stealth is lost
and the whole mission becomes much tougher for the
Clearly the amount of snorkel mast wake is related
to relative speed through the water, and the required
duration of snorting is dependent on how far the main
batteries are run down. Since power required to propel
a submarine increases dramatically with its speed, this
correspondingly runs down its MSBs faster.
For example a conventional diesel-electric submarine
travelling at 8 knots on its batteries alone has an MSB
endurance of around 15 hours. When patrolling at 4
knots this endurance extends to around 60 hours, or
four times longer. This translates from snorting once
a day when averaging 8 knots, to only every third day
when patrolling at 4 knots.
Adding air independent propulsion (AIP) can
greatly increase a submarine’s underwater endurance.
Consequent lowered indiscretion ratio, i.e . the time
spent snorting to the total time spent on mission, is
highly desirable, although it comes at the cost of a
larger and more expensive submarine to accommodate
the AIP system.
MAIN STORAGE BATTERIES
A submarine’s electrical power requirements can be
divided clearly between two main uses. First is the
continuous ‘hotel services’ load which is present
at all times during a mission. This covers combat
and navigation systems, lighting, electronics, food
refrigeration, cooking, entertainment, air purification,
interior heating, etc.
Second, the submarine requires power to the
electric motor for propulsion – whether at periscope
depth or not. The choice of MSB or AIP for slow patrol
is a decision for the commanding officer. To achieve
higher speeds the MSB must be used. If the MSB is
down on charge and the CO wants high speed in the
near future, he can order the AIP to be used to bring
the MSB up to a higher charge state.
Before the selection of DCNS, all three CEP
contenders devoted a lot of research and testing effort
into LIBs which offer a range of advantages when
compared with lead acid batteries. These include a
higher charge rate for shorter snorting time; endurance
improvement; a higher discharge rate giving a speed
boost; closed cell system with no flammable gas
discharge; reduced weight and size; less battery
maintenance; more durable as tested in-service.
Because this is such a hot topic, APDR quizzed the
three CEP contenders on their positions vis-à-vis LIBs.
When APDR asked DCNS about their submarine
battery R&D they responded ‘DCNS is currently
working in partnership with SAFT, the world’s leading
designer and manufacturer of advanced technology
batteries for industry, to develop LIB technology.
‘Lithium-ion batteries is a promising technology, but
not yet proven nor secured in very specific environments
‘We expect that it will be available at some point in
the future for the SEA1000 program.’
In APDR’s opinion, DCNS is right to be cautious
about LIBs in submarines. Because the voltage
produced in each LIB cell is small, large numbers have
to be connected to provide a reasonable voltage for the
submarine’s electrical requirements. Then each string
of cells has to be connected in parallel to supply the
necessary current. The future submarine would need
over 100,000 cells in some 500 modules. In a fleet of
12 submarines, each with LIBs, this could amount to
1.2 million cells.
Over-charge or too much discharge, or exposure to
high temperatures can cause a catastrophic failure.
This then requires hardened blocks of cells within a
module to contain any explosion, hopefully avoided by
a sophisticated control and switching system.
TKMS Australia provided APDR with this statement.
‘There are three key aspects to a Li-ion battery. One
is the cell and its chemistry, the next the module
and string design of the battery (how the cells are
connected) and finally the battery management system.
Both the latter two are mature technologies in TKMS.
‘ . . . . . We have sought and found two companies
that provide Li-ion chemistries that do not suffer
from thermal runaway. The energy storage is slightly
reduced, but still far superior to a lead acid battery. We
The use of Lithium ion batteries (LIBs) offer the promise of reduced
indiscretion ratios because they can take higher charge rates and
thus reducing vulnerable snort time.
The aim is not to imitate a nuclear submarine and never snort: that
is simply not practical with current technology.
Asia Pacific Defence Reporter M AY 2 0 1 6 19
29/04/2016 6:49 PM
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