Layout of a Modern Nuclear Submarine

Below is an example layout of a modern nuclear submarine. It is not specific to any particular class of vessel and the layout will change to some extent between boats but it contains all the major components that a modern attack submarine will (or could) be made up of.

By clicking on each section you can read more detail on the contents or purpose of that section. A glossary of the terms used is at the bottom of the page.

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Command and Control

Control Room : The nerve centre of the submarine where the Captain receives information from the command team and outstation controllers and in return gives the orders. The AIO and Fire Control stations are in the control room as well as direct access to the periscopes and control of the other masts.
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Manoeuvre Room : Control of the rudders, planes and ballast tanks to allow the submarine to manoeuvre. The actual 'driving' however is usually done from a station in the control room.
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Reactor Services : Control and care of the nuclear reactors is important and this is where its all carried out. Hey we're not like the old Warsaw Pact boats where the life expectancy was somewhat low due to lack of reactor shielding!
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Sonar Room : Where the inputs from the various sonars are received and analysed. This analysis may take the form of matching a sound to a similar one in a pre-recorded library (either automatically or manually) cutting out background clutter for a clearer picture and cutting the data from each track across to the AIO station.
This area can also include the main computer room which runs the AIO and Fire Control stations.
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Control Surfaces

Rudder & Controls : Rudders and planes (not shown) are used to steer the submarine and also to aid in the diving and surfacing process along with the flooding or emptying of ballast tanks. As well as being mounted at the rear planes may be mounted on the fin or, more commonly because of fragility problems with breaking through ice using the fin, at the front of the hull. These planes may or may not be retractable.
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Anchor : Like all seagoing vessels a submarine requires an anchor which is usually stored inside the nose and is released downwards through a dedicated hatch in the bottom of the hull
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Engineering

Air Cycling / Store : Air is scrubbed and recycled for the crew so no nuclear submarine needs to come to the surface for anything except food. Also air is pumped into the ballast tanks to empty them of water if the submarine wished to reduced depth or surface.
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Batteries : Batteries are used to store power for when the nuclear reactor is off-line and a shore supply for the internal electronic system is not available, for example when moving within harbour.
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Diesel Engines : An emergency system for if the nuclear powerplant is not capable of operation, or an auxiliary unit for when the powerplant has been powered down and a short distance (say manoeuvring in harbour) is required.
The diesel engines on a nuclear submarine are usually not capable of anything but the slowest speeds and should not be used for significant periods of time. However since the nuclear powerplant may take up to a day to reach full power it is useful for when the boat is alongside.
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Diesel Fuel : The reserve for the diesel engines.
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Engine Room : The engine room and main propshaft for the propellor or pump jet.
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Nuclear Reactor : The main source of power for propulsion and for all electrical requirements on board the reactor will have a lifespan of many years and be essentially a sealed unit without a major engineering effort.
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Pump Jet / Propeller : To propel the submarine through the water it will use either a propellor or, in some more modern designs, a pump jet.
The pump jet has the advantage of being generally quieter (though advanced propeller design can also aid in this area) and give less chance of cavitation at increased speeds. Note that there is a propeller in the design of a pump jet though, despite the change of name, at very high speeds cavitation is still a risk.
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Entry/Exit

Escape Hatch : A hatch into the submarine positioned for an escape for certain sections of the crew. This hatch may also be used for normal access if other hatches are inaccessible for some reason.
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Escape Pod : A more modern invention, some submarines are now equipped with small pods which can be used to evacuate some of the crew.
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Hatch : The normal way in and out of a submarine the hatch will have an airlock beneath it but this can be left open if the boat is in harbour.
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Living Areas

Messes : Eating and relaxation areas for the crew and officers. Often divided into the different ranks so that, for example on a British submarine, the officers will be eating in the Ward Room, and the other ranks divided between the Senior Rates and Junior Rates messes.
On British boats alcohol is available (though rarely if ever drunk while at sea) which makes visits to them, if they are permitted, very popular with the other navies.
For your information, the Ward Room will have spirits, the Junior Rates mess beers and the Senior Rates mess both ... get to be friends with a CPO (Chief Petty Officer) 'cos you're not allowed to buy your own alcohol (except by the barrel) and they can buy it for you really cheap :)
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Bunks : The ratings don't get cabins but instead have stacked bunks. In the past there was often a need to 'hotbunk' so that each bunk was used by crew-members who were on different shifts though this has mostly been eliminated nowadays. However some of the bunks are still positioned in rather awkward places such as between torpedo racks or just next to main corridors to use up the space as efficiently as possible.
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Cabins : Officers get cabins though even the captain's cabin is not that large due to the restrictions of space onboard a submarine. Each officer will have safes and/or communication equipment appropriate to their position and notice that it is not too far from the cabin area to the control room for those times when a middle of the night disturbance is required.
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Masts

Masts : There are various masts used onboard a submarine with the most famous of these of course being the periscope (actually there is usually more than one periscope; one used for setting up visual attack solutions the other for general and navigation purposes).
Other masts include small radars and various communications and electronic detection masts. The radar and communications masts are quite self explanatory (though the radar would probably not be used often due to the risk of giving away position with an active signal) and the electronic detection masts are used to find out not only if any plane or ship is using radar to scan for contacts but also to analyse those scanning signals and give another sensor input to aid in the detection and tracking of those planes and ships.
Note that modern detection radar carried by specialist aircraft can detect the protrusion of a periscope of large mast at huge distances so knowing when this is a risk is vitally important.
Just so you know, nowadays periscopes rarely stay up for long ... up, spin, down again ad then they watch the recording; a defence contractor quoted millions for a system to record the images but a clever Navy bod worked out how to connect up a video recorder from Dixons and save themselves a bit of money!
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Sonar

Bow Sonar : The main forward facing sonar array which will almost always be used in passive mode though capable of active ranging.
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Fin / Flank Sonar : Smaller specialist sonars mounted on the fin (for example, a high frequency, short-range active sonar to detect mines or underwater obstacles without giving away the boat's position to anyone who is not extremely near) and long flank sonars (not shown) along the sides on the submarine.
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Towed Array Sonar : A long, flexible, neutrally buoyant pipe with many low frequency passive sonars along its length.
The advantage of the towed array is that it can be streamed out a distance behind the submarine so it is not affected by the noise of its own engines and crew. It is tremendously sensitive with great powers of detection but does have a few disadvantages in that it is quite delicate (some submarines carry 2 incase one breaks) and because of its flexibility needs a few minutes after a change of direction to 'straighten out' again so it can start to give consistent readings.
Also, by virtue of some complicated low frequency physics (don't ask) each detection will be 'mirrored' left and right whichever side it is actually on - this 'reflection' can however ususlly be eliminated quite quickly by cross referencing it with the inputs of other sonars or changing course to see which track remains in the same lace and which moves.
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Storage

Food / Beer Storage : Storage area for provisions. Note that beer and other alcohol are only available on Royal Navy submarines.
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General Storage : Storage area for other possesions and kit.
Actually storage is everywhere is a submarine - not an inch is wasted, corridors are narrow and everywhere you look a vital piece of equipment has its place ( So if you're ever on board a submarine watch your head!)
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Weapons

Torpedo Room : Where the weapons are stored and can be loaded into the torpedo tubes. The room will also contain the manual controls for the opening and closing of the bow doors of the tubes and associated water/air valves. The weapons fit will probably be made up of wire-guided torpedoes, anti-ship missiles and, maybe, cruise missiles. Mines can also be carried to be 'layed' through the torpedo tubes.
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Launch Gear : The tubes and all the external bow doors and internal valves to select which tube will be flooded or fired. Often a single water or air 'ram' will be responsible for more than one tube so the valves must be switched between tubes while the ram recocks to fire another weapon off that ram.
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Glossary

Active Sonar : The traditional "World War 2 movie sonar" which produces a 'ping' of sound and then listens to its return to judge if any object has blocked its path.
This type (or mode) of sonar is very rarely used nowadays so as to not give away the submarine's position but there are specialist high-frequency sets which can only be 'heard' for a short disance which can be used to detect mines and other silent underwater obstacles.
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AIO - Action Information Organisation : This station receives inputs from the sonars, or directly by the operator, and contains the whole tactical picture around the submarine.
To aid it in this task sophisticated algorithms are used to perform Target Motion Analysis (TMA) on all the various tracks within 150 miles or more of the submarine. For an attack the information on a particular track is passed to the Fire Control station, usually over an electronic link.
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Cavitation : This is when an object (in the case of a submarine, the propeller) is moving so quickly through water that air bubbles start to form on the surfaces as the water is disturbed.
The problem is not one of performance but of increased noise created by the propeller while cavitating which is detectable at much greater ranges and much more easily than in normal operation. Since the submarine is essentially a stealth weapon this is usually avoided at all costs.
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Fin : The name given to the conning tower of the submarine which contains the masts.
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Fire Control : This station receives inputs on a particular track (or tracks in the case of multi-target capable systems), usually from AIO but sometimes directly from the operator, and then engages the track with the appropriate weapon system. A firing solution is then calculated for that weapon and, if ordered, the weapon powered up and fired.
After firing if the weapon id post-fire guidable (such as a wire guided torpedo) the Fire Control station is where it will be controlled from.
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Passive Sonar : Essentially a big, very sensitive, ear. This type of sonar will listen for other vessels and, when detecting them, provide a bearing to the vessel and additional information about the frequencies of its engines and propellors giving information on its type and speed.
This is how almost all sonar is used nowadays so as not to give away the submarine's position, though obviously it cannot detect aything silent like mines or rocks.
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TMA - Target Motion Analysis : A series of algorithms used to calculate the range and course of a track when the only information available is the bearing (from a sonar) and the noise of the track's engines (used to calculate speed when cross-referenced with known values for rotational speeds for each ship type's propellor).
To get the best solution it is often best to listen to the track for a while and then change course to get a different angle-off; this can be repeated as often as necessary but the longer it takes the more likely the track will change course or speed itself and mean that your solution must be recalculated.
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This page created by me

Hatch Escape Pod Air Cycling Escape Hatch Hatch / Air Lock General Storage Towed Array Sonar Manoeuvre Room Escape Pod Bow Sonar Launch Gear Food and Beer Store Anchor Torpedo Room Sonar Room Fin Sonar Fin Sonar Masts Control Room Bunks Cabins Messes Batteries Diesel Fuel Reactor Services Nuclear Reactor Diesel Engines Engine Room Pump Jet / Propeller Rudder and Controls Rudder and Controls