Roaming the Oceans

Roaming the Oceans

When anything tries to move through water, the water resists its movement. Boat designers try to minimize water resistance, called “drag”, by making boat hulls as smooth and streamlined as possible. Water underneath a boat pushes up against its hull with a force called “upthrust”. If the force of the boat's weight is equal to the upthrust of the water, the boat floats. If the boat weighs more than the upthrust of the water, it sinks. A submarine, or a smaller underwater craft called a submersible, sinks under the waves by letting water into its ballast tanks to make it heavier. It rises to the surface again by forcing the water out of the tanks with compressed air, or by dropping heavy weights to make the craft lighter. Most working boats, submarines and submersibles are powered by propellers with angles blades that push against the water as they turn.

Setting Sail

A sail is set at an angle so that wind blowing around the sail from the side reduces the air pressure in front of it, sucking the sail and the boat forward. This means that a sail can use a wind blowing in one direction to propel a yacht in a completely different direction. But a yacht can never sail directly into the wind.

When compasses were first used on ships, seamen did not understand how they worked and were afraid of the magical powers they seemed to possess. Compasses were hidden from the crew inside a box called a binnacle.

Manipulator Arm

A robot arm with a mechanical claw at the end of it picks up objects from the sea bed.

Below the Surface

Submersibles allow scientists to explore the sea bed, study living organisms in their natural surrounding and investigate shipwrecks.

Ocean. Photo by Elena.

Crew Sphere

The crew members sit inside a metal sphere because a sphere is the best shape to resist the crushing pressure of water. Air for the crew to breathe is also stored in spherical tanks.

Global Positioning System (GPS)

Navigators used to figure out the position of a ship at sea by studying the position of the sun or the stars. Now they use a system called Global Positioning System or GPS. Satellites orbiting the Earth send out radio signals that are picked up by a receiver in the ship. The signals tell the receiver where each satellite is, how fast it is flying, in which direction and what the time is. By using signals from at least three satellites, the receiver can calculate the position of the ship.

Thruster

A thruster is a propeller inside a tube driven by an electric motor. Submersibles are propelled and sterred by thrusters.

Ballast tanks

The submersible sinks by letting water into its ballast tanks.

Batteries

Electric power for the thrusters, lights, cameras and other instruments is supplied by a set of batteries.

Iron ballast

Iron bars provide some of the weight that is required to sink the submersible.