How do submarines float and dive?

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Sinking a Submarine (or any other vessel) is pretty easy - with enough water it'll sink straight to the bottom of the ocean real fast. The key is getting the number of surfaces to equal the number of dives.

Submarines use several systems along with fixed ballast to decrease buoyancy to submerge, or increase it to surface:

1. Main Ballast Tanks (MBT's)
2. Trim Ballast Tanks (Trim Tanks)
3. Trim/Dive Planes
4. Main Propulsion Systems

Like all vessels, submarines have fixed and variable ballast weight. Her fixed ballast, essentially just iron weights, allow the boat to remain on the surface in a positive buoyancy state, i.e., floating on the surface but mostly submerged. All pictures you see of surfaced submarines only show about a 1/4 of the actual hull above water. Variable ballast, consisting of Main and Trim Ballast tanks, as well as personnel and all supplies onboard, help the boat maintain submerged operations at fixed or variable depths as required.

A boat's fixed ballast weight is a known variable; it is the addition or removal of variable ballast that must be closely monitored. All supplies and personnel (including weapons load-out) are monitored and estimated weight is calculated so that when the MBT's are purged and filled, the crew already knows how much trim ballast water to bring in to achieve a state of Neutral Buoyancy, which is a submerged state in which the boat neither rises nor sinks. Achieving Neutral Buoyancy is also used by Scuba Divers for maintaining their own depth control.

Without knowing an estimate of pre-submergence ballast amount, too much variable ballast can sink her too far upon submerging. If you're wondering, the boat's crush depth or the bottom of the ocean is considered too far, whichever comes first.

The calculations must be continually updated during longer missions, as supplies are used and trash is put overboard via the trash tube, or exercise weapons are shot.

For anyone who is certified in SCUBA, the principles are essentially the same. A diver, using a combination of personal weight and added lead weights for fixed ballast, uses air inflated into, or deflated from, a buoyancy compensator (variable ballast) to adjust for neutral, positive, or negative buoyancy. The only difference is that divers initially make themselves negatively buoyant to get beneath the water.

Water temperature and salinity are also variables and affect variable ballast. For example, due to the cold freshwater ice of the Polar ice cap, water in the Arctic has a lower salinity level than the open ocean. Since colder temperatures affect density, and lower salinity causes less buoyancy, submerged operations under the ice must take this into account for ballasting purposes.

The Main Ballast Tanks are nothing more than large sections between the outer hull and inner hull. Submarines have 2 hulls, much like a thermos bottle; the outer Superstructure which is visible, and the inner Pressure hull, which houses the crew. The bottom of a tank has an open grate, where the top of the tank has a hydraulically activated valve. Think about a bottle without a bottom and a cork in it; if you put it in water and pull the cork the air is forced out by the water pressure - same principle. The pressure on the air inside the tank when surfaced is enormous - to dive the boat, the MBT valves are opened, and the sea pressure forces the air out of the tank through the open valve. Once the tanks are full of water, the valves are closed. As with all onboard systems, the MBT valves, which are physically located on the main deck of the Superstructure, can be opened or closed hydraulically or manually.

After submerging, the Chief of the Watch (the primary operator of the key diving and control systems for the boat) will bring in or pump out water from several Trim Ballast Tanks (used for ship leveling and minor ballast adjustments as the boat moves to specific depths) on the boat. Trimming the boat gets the boat to Neutral Buoyancy. The Chief of the Watch takes orders from the Diving Officer, who is in charge of keeping the boat at NB while submerged. The Diving Officer also gives orders to the Helmsman and Planesman (Helmsman steers, Planesman maintains depth) as necessary, and the Trim/Dive planes and ship propulsion help maintain the boat on depth until the Trim tanks can be adjusted to the new depth, if required.

From there the Dive Planes take over for moving deep or shallow. Older WW2 era submarines used Bow Dive Planes, which were located at the bow of the boat. When the Teardrop Hull shape used today was developed, the Dive Planes were moved to the Fairwater, which is the superstructure above the hull that houses the periscopes and other masts. It is often incorrectly called a Conning Tower, which is a holdover from the older Fleet type submarines of WWI and WWII. The boat was controlled (conned) by the CO from an area above the main control room where the helm and planesmen and other crew were during an attack. The correct term for submarines with dive planes on the Fairwater is Fairwater Planes. For planes on the bow, they are called Bow Dive Planes, or simply Bow Planes.

Fairwater Planes have their problems though. In rough water, if the boat is at Periscope Depth, and is inadvertently sucked to the surface by a large enough wave, the boat can lose its depth control ability very quickly. If in a tactical situation, it makes it even more dicey if non-discovery is imperative. For this reason. the new Seawolf and Virginia class boats have gone back to Bow Planes, which give the boat depth control whether the sail is out of the water or not. A boat with a broached sail and bow planes can dive much faster than one with Fairwater planes can, since the latter must rely on bringing on more trim ballast to submerge when the primary control surfaces are out of the water.

There are 2 primary methods of surfacing a boat - an "Emergency Blow", used in emergency situations to surface rapidly, and a "Low Pressure Blow".

During an EB, compressed air stored in tanks (outside the pressure hull in the MBT's) is released rapidly into the Main Ballast Tanks to expel water and thus create Positive Buoyancy. The other method is a Low Pressure Blow, using the boat's onboard Low Pressure Blower (essentially a large fan blower) to slowly blow air into the MBT's. This is only used near the surface at Periscope Depth, as it requires the Snorkel Mast to be raised. Utilizing the LPB saves vital compressed air, which is used for emergency systems and weapon ejection. A Low Pressure Blow is the most common method of surfacing a Submarine in a non-emergency situation. The backup Diesel Generator exhaust can also be used in place of the LPB if needed, though the ship's ventilation system must be rigged to pipe the exhaust to the ballast tanks.

If you've seen pictures or film of a boat's bow coming out of the water at a steep angle at high speed, that's the result of an emergency blow at deep depth. It takes about 90 seconds from Test Depth to broach the surface, with the engines pushing the boat at full or flank speed. It's a hell of ride, and one that we all looked forward to as we didn't get to do it often, just for drills or certifications. Once the boat broaches, it sinks back down to about PD, and the LPB is used to fully surface the boat.

It is important to also note that the boat's propulsion type (Diesel-Electric or Nuclear) plays a big role in keeping the boat on course and depth. Without functional propulsion, any major casualty is next to impossible to deal with. It is this fact that is believed to be at the heart of the USS Thresher's loss.

In those days, during any casualty, the procedure was to perform a Reactor Scram (inserting all Control Rods to slow reaction to minimum), or to shut down the reactor. This left her without vital propulsion power after a major hull valve ruptured and left her with a major flooding casualty to fight. Pressure at deeper depths compresses air, and any air dumped into the MBT's during an emergency blow will take time to expand as the boat heads for shallower water. However, without functional propulsion, if the boat is sinking already, it's fighting a losing battle. Without the aid of her main engines to push her to the surface, Thresher's sinking was inevitable.

The loss of the Thresher led to many changes in the Nuclear Submarine program in the U.S. (SUBSAFE QA program), and for other Allied Nations with similar capability. Since the institution of the SUBSAFE program, there has not been a similar accident in the U.S. submarine fleet.
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How far can submarines dive?

U.S. Submarines can dive 800-plus feet. (Official depth; however, can dive deeper. The US Navy itself acknowledges that most of it's attack submarines can operate down to at least 985 feet, and many to over 1400 feet.

How does a submarine float?

It floats and sink by changing its buoyancy. The primary method of controling buoyancy is the ballast tanks. The air is let out of them and is displaced by water. This gives the submarine negative buoyancy, which will get the submarine to submerge. By blowing or pumping air into those ballast tanks, ( Full Answer )

How deep does a submarine dive?

The deepest submarine is built to go 10000 meters under water. Thisis so they can go to the bottom of the ocean floor.

How does a submarine dive and surface?

Massive ballast tanks can be filled with water or air, changing the weight and buoyancy of a sub. Once dived a sub can use hydroplanes to angle it towards the surface and use propulsion to drive to the surface.

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How do submarines float and sink in water?

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What would a diving submarine do to halt its descent?

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How much submarine dive into deep water?

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How can submarines float and sink?

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Why is it that the submarine can dive to the water and the ship cant?

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Why do submarines float if they weigh more than water?

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How deep can submarine dive in to the water?

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How deep can U.S submarines dive?

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How do submarines and whales sink and float in water as needed?

Submarines and whales have ways to adjust their buoyancy . That's how they sink and float as needed. Each has a different method of adjusting buoyancy. The submarine controls buoyancy by adjusting ballast. Submarines have ballast tanks that can be filled with air or flooded down with water. When ( Full Answer )

How many feet can a submarine dive?

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Why does a submarine sink and float?

A submarine has two main mechanisms that allow it to sink and return to the surface. The submarine has dive tanks that can be filled with water to make the ship's weight the same as the water it displaces, or a little more. This causes the boat to sink. Air can be blown into those tanks to reduce ( Full Answer )

What was the dive speed of the U-571 submarine?

Like any submarine, there is no specific dive speed for the U-571, a German Type VIIC U-Boat, which was commissioned in 1941 and sunk in 1944. Dive speed is dependent on several variables, including, but not limited to: 1. Fixed ballast weight 2. Variable ballast weight 3. Ocean depth, the ( Full Answer )

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What makes submarines float underwater?

air pressure because if air is lighter than water and you are trying to get a tank full of water to sink you would need a whole lot of air so by compressing lots of air into the tank it makes the tank heavy so it sinks

Is the density of a submerged submarine about the same as the density of a floating submarine?

The average density of a submerged submarine is about that of the water that surrounds it. It is said to have neutral buoyancy. But the average density of a floating submarine is less than the density of water, otherwise it would not float. (It could be argued that the density of a submarine is ( Full Answer )

How does buoyancy and density help a submarine to dive and float?

A submarine has buoyancy tanks along its length. To dive or sink these are filled with water, which enters through valves, so the vessel becomes heavier. Its speed of descent can be controlled by the amount of water in the tanks and also by aerilons (small wings) which can be tilted to steepen the d ( Full Answer )

How do submarines float with heavy metal?

They have ballast tanks that can be filled with air for buoyancy. Answer: Floating or sinking in water is related to the density of the entire enclosed volume of the submarine. Obviously if the metal in a submarine were compressed into a ball it would sink as its density would exceed the density ( Full Answer )

How do submarines float and then sink?

The majority if a submarine is not the space where the crew lives, but large tanks called ballast tanks. When the submarine wants to sink, water is pumped into the ballasts and the submarines average density gets higher than that of the surrounding water so it sinks. When this happens the air is com ( Full Answer )

How submarines float on water?

The air trapped in the hull (this includes the buoyancy tanks) make it lighter than the water it displaces. The buoyancy tanks surround the main hull (where the people and machinery are), and can be flooded to allow the ship to sink. Refilling them with air (from compressed air tanks) allows it to ( Full Answer )

What was the name of the first submarine to dive to the bottom of the Mariana trench?

The Swiss-designed, Italian-built, United States Navy bathyscaphe Trieste reached the bottom at 1:06 p.m. on January 23, 1960, with U.S. Navy Lieutenant Don Walsh and Jacques Piccard on board. Only three descents have ever been achieved. The first was the manned descent by Trieste in 1960. This ( Full Answer )

Can you hear voices in a submarine while scuba diving?

It's just barely possible you could under the right conditions.You'd need to be quite close to the submarine, and they'd bedistorted and difficult to understand, the same way you can hearyour neighbors in an apartment building but not necessarily be ableto understand what they're saying. It doesn't ( Full Answer )

How submarines floats on water surface and submerge into water?

Air is trapped in the ballast tanks which surround the boat. This makes it positively bouyant (why it floats). To submerge the boat the air is vented out of the tanks via the main ballast tank vents which are at the highest point in the tank. As the air escapes seawater comes into the tank through t ( Full Answer )

Why do ships float while submarines sink?

Submarines are designed with enough ballast and control systems to allow them to submerge and surface as needed. Surface ships are designed only with enough ballast and control systems to keep them on the surface. While they can sink just as well as submarines can, their ability to re-surface witho ( Full Answer )

What is the command for dive on a submarine?

The Conn Officer will first order the boat to be Rigged for Dive. Upon getting a green board on the Ballast Control Panel (BCP) indicating all major hull openings are shut (red indicator means open), and reports from all stations that the boat is Rigged for Dive, he'll order the Diving Officer to di ( Full Answer )

Why does the submarine float and submerge in water?

Submarines must be able to float to load and offload crew and cargoand to have repairs and maintenance. They are designed to submergeeither for underwater exploration or to pass undetected by ships atthe surface and planes and satellites above.