How does a sub dive?

When the submarine is floating on the surface, the tanks are filled with air causing its density to be less than the surrounding water. When the submarine dives, the tanks are flooded with water causing its density to be greater than the water causing it to sink.

How submarines control depth?

The exact depth can be controlled by adjusting the water to air ratio in the ballast tanks. Submerged, the submarine can obtain neutral buoyancy. That means the weight of the submarine equals the amount of water it displaces. The submarine will neither rise nor sink in this state.

How does a propeller move a boat forward?

Propeller blades displace water, to create the forces that move a boat forward. The propeller works by turning torque into thrust. In other words, it converts power from the engine into an action. The action of turning the propellers creates force, by moving the flow of water downward and behind the blades.

How do submarines move forward?

A surface vessel, including a surfaced submarine, moves from point to point in two dimensions. Backward and forward motion is controlled by the submarine’s screws (propellers). Lateral submarine controls are imparted by the rudder (or rudders). Vertical submarine controls are imparted by the bow and stern planes.

How does a submarine navigate?

Submarines carry an inertial navigation system, which measures the boat’s motion and constantly updates position. Because it does not rely on radio signals or celestial sightings, it allows the boat to navigate while remaining hidden under the surface.

How does a propeller shaft work?

The propeller shaft transfers engine torque to the rear axle through one or more universal joints. The splines on the ends at the propeller shaft fit perfectly into the splines in the sleeve.

What is a skewback propeller used on a submarine?

An advanced type of propeller used on German Type 212 submarines is called a skewback propeller. As in the scimitar blades used on some aircraft, the blade tips of a skewback propeller are swept back against the direction of rotation.

What is the geometry of a marine screw propeller?

The geometry of a marine screw propeller is based on a helicoidal surface. This may form the face of the blade, or the blades face may be described by offsets from this surface. The back of the blade is described by offsets from the helicoid surface in the same way that an aerofoil may be described by offsets from the chord line.

What are the advantages of blade rotation in propellers?

In such propellers the blades can be rotated about axes normal to the driving shaft so that thrust and torque can be varied at constant shaft revolutions. This can help match the propeller and machinery characteristics. If the blade rotation is great enough the propeller can produce astern thrust removing the need for a reversing gearbox.