Hello everyone, you are watching another episode of Military TV.
Swimming like a fish beneath the surface of the sea,
enclosed in a capsule, is something people attempted in ancient times and in the Middle Ages.
In 1492, the Italian Roberto Valturio made a sketch of a submarine that in its external shape
very closely resembles modern-day submersibles. Followed by the German inventor Wilhelm Bauer
staged a trial of his ‘incendiary diver’ in 1851. It was the first modern submarine and
was built according to the inventor’s plans at the Schweffel & Howaldt engineering works and
iron foundry in Kiel. Until then the engineers started making engines for submarines in 1959,
and they may now be found in service in all the world’s oceans. But then, the questions
are how a diesel submarine is propelled and how long can it stay submerged under water?
So, stay tuned and make sure to watch this video till the end!
Most diesel submarines are equipped with two or more diesel engines.
The diesel engines can power propellers or generators that recharge a large battery bank.
They can also be used in combination with one driving a propeller and a generator.
To use the diesel engines, the submarine may surface (or travel slightly below the surface
using a snorkel). Meanwhile, the sub can go underwater after the batteries are fully charged.
Unfortunately, the limitations of battery technology drastically limit how long a diesel
submarine may stay underwater. Therefore, this seems a significant advantage of employing nuclear
power as nuclear generators do not require oxygen and may stay under water for weeks at a time.
Anyway, let’s take a look at our previous question, how is a submarine propelled?
In a submarine with diesel-electric propulsion, a diesel engine drives a battery charging unit.
The submarine’s charging unit can only be operated when the vessel is on the surface or
in snorkelling mode because the engine needs air for fuel combustion. In snorkelling mode, the sub
is just a few meters below the surface and the air for combustion is drawn in through the snorkel,
from where it passes to the engine in the engine room. If the submarine is to remain undetected,
however, snorkel conditions can only be maintained for as short a period as possible. The exhaust is
discharged under pressure below the surface. For every meter of water above the exhaust outlet,
the engine has to generate an extra 100 mbar of exhaust pressure so that the water cannot
run into the engine. That is only possible with a special charge air system developed by MTU.
Moreover, the submarine with diesel power has diesel genset that serves as a battery
charger and charges the batteries with electric current. That electric current
powers the electric propulsion motor, which in turn drives the propeller.
In regard to the total duration a submarine can stay underwater,
submarines using diesel-electric propulsion generally have to surface every couple of
days to run the charging unit and recharge the batteries.
However, with a special fuel cell system, subs can remain underwater for longer. The current
record which is set by an HDW Class 212A submarine is 14 days. If a submarine is unable to surface,
standard regulations require that the crew must be able to survive for at least six days.
It can be said that the diesel-powered submarines
(which are no longer in use by the US Navy) could only stay submerged for a few days.
They couldn't use the air-breathing engines while completely submerged, so they had to
rely on battery power and electronic motors. They'd have to come to the surface and use the
snorkel mast for air to recharge the batteries and exchange fresh air for the diesel engines.
All this said, diesel boats are generally easier and cheaper to field.
On top of this, they also tend to run quieter than boats with a nuclear reactor,
and in an arena of warfare where noise equals death, they remain an attractive option. Lastly,
it can be predicted that the improvement in battery technology will likely be
one of the next technical advances in submarine technologies in the future.
That’s all for today, thanks for watching, see you next time!