Home' Asia Pacific Defence Reporter : APDR October 2015 Contents 40 Asia Pacific Defence Reporter OCT 2015
Why the significance? The propulsion
chain accounts for up to 35% of a
submarine’s weight and more than 50%
of its space allocation. Its design is inherently linked
to the submarine’s hull size and shape, range and
endurance and top speed. Its design determines how
fuel energy is stored and then converted to electrical
energy and again to propulsive energy. Importantly, it
also determines the efficiency of those conversions.
Because equipment in the propulsion chain is large
and powerful its constitution also has an impact on a
submarine’s thermal, magnetic and acoustic signature.
Finally there are also very serious propulsion chain
reliability, maintainability, redundancy, ubiquity and
safety considerations to be included in the design mix.
This month’s APDR looks at the likely propulsion
chains of TKMS’ SEA 1000 concept design and
makes a limited comparison to the likely DCNS and
AN INTEGRATED AND UNIQUE
Before delving into the components of the
propulsion chain it is worth emphasising that they
are sub-systems within a carefully designed system.
They shouldn’t be considered in isolation and they
can’t be ‘mix and match’.
By way of example, the diesel-generator can only be
selected after the charging characteristics and profiles
of the proposed battery solution are decided. The
battery must only be selected after due consideration
of the operating characteristics of the proposed main
It also makes little sense to integrate an unreliable
diesel sub-system into the chain of an otherwise reliable
system, nor would a designer select an inefficient main
motor at the end of an otherwise efficient set of other
propulsion chain sub-systems.
The components must be designed or chosen to
match each other, and with regard to unique submarine
A SYSTEM WITHIN A SYSTEMS-OF-
It is also necessary to appreciate that the entire
propulsion chain is part of the system-of-systems that
is a submarine.
A greater top speed will result in a need to increase
propulsion equipment size and therefore, for a given
size of submarine, a need to decrease payload space.
Likewise, inserting an AIP plug into a submarine
will affect form and skin friction drag that could
either decrease or increase the propulsion energy
requirements for any given speed.
The propulsion chain design must be considered in
the context of the total submarine design.
If one discounts leaving harbour with a full battery and
returning with it fully discharged, the total (propulsion
and hotel) energy requirements of a submarine,
including any operational commander’s reserve, has to
be met by embarked fuels/reactants.
In the case of the TKMS’ SEA 1000 solution this will
mean the carriage of diesel fuel for the diesel-generators
along with methanol and liquid oxygen (‘LOX’) for the
Methanol-Reformer/Fuel Cell (‘FC’) AIP system. Diesel
will be stored in standard seawater compensated fuel
tanks. Whilst methanol can also be stored in tanks, it
needs to be separated from compensating seawater
and so a flexible rubber bladder arrangement will be
used. LOX will be stored in an internal cryogenic tank.
For DCNS, the fuelling system will be simplified by
the need to carry only two fuels; diesel for the diesel-
generators and the diesel-reformer/FC AIP system and
LOX for the diesel-reformer/FC AIP system.
The Japanese will not offer an AIP solution.
This simplifies the enhanced Soryu’s fuel storage
requirements to just diesel.
Before progressing, and with fuel in the reader’s
mind, it is worth introducing the critical importance
of propulsion chain efficiency. As energy conversion
takes place, from reactant to electric and electric to
propulsive, any efficiency advantage over another CEP
contender’s solution is important. Better efficiency
results in greater submarine endurance or a reduction
in fuel storage requirements for any given endurance.
The primary purpose of a diesel-generator is to convert
stored diesel fuel energy into electrical energy that
can be stored in the submarine’s main battery. Noting
the energy-density of diesel is significantly higher than
any AIP reactant, all CEP contenders will have diesel-
generators as part of their offering.
TKMS will likely include four MTU 12V4000U83
diesels each coupled to a Pillar NTB 60.40-12
generator in their concept design.
The 12V4000U83 is the submarine variant of MTU’s
Series 4000 diesel. It outputs 1300 kW at 1800 RPM
and can do so with up to eight metres of swell above
the exhaust outlet. This provides for a robust snorting
capability and stable power output under severe
sea conditions and will help ensure no unwanted
‘stop snorts’ occur. This is achieved with a special
REX PATRICK // SYDNEY
THE DRIVING FACTOR IN THE
SEA 1000 CHOICE
THE SUBMARINE PROPULSION CHAIN
A submarine’s propulsion chain is a fundamental consideration in the context of a submarine design. It consists of all components
used to power and propel the submarine. In a conventional submarine’s case the major subsystems include the fuel store,
diesel-generators, Air Independent Propulsion (‘AIP’), batteries and main propulsion motor.
17/09/2015 5:20 pm
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