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How does a submarine work?

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Quick answer

A submarine works by changing its weight to dive and surface, using tanks that fill with water or air. To dive, it floods ballast tanks with seawater to become heavier; to surface, it blows the water out with compressed air to become lighter.

Step by step

Ballast tanks fill with water to make the sub heavier and sink.
Compressed air pushes the water out to make it lighter and rise.
Adjusting the balance lets it hover at any depth.
Propellers and fins drive and steer it underwater.
It carries its own oxygen and can stay submerged for long periods.

People also ask

How does a submarine dive and surface?

It floods ballast tanks with seawater to get heavier and sink, then blows the water out with compressed air to get lighter and rise.

How does a submarine stay at a set depth?

By balancing its weight against the water it displaces, fine-tuned with ballast and small 'trim' adjustments, so it neither rises nor sinks.

How do submarines get air to breathe?

They carry oxygen supplies and systems to scrub carbon dioxide; nuclear subs can even make oxygen from seawater, staying down for months.

What is buoyancy?

The upward force water exerts on an object; controlling it lets a sub float, hover, or sink.

How do submarines navigate underwater?

They use sonar, since light doesn't travel far underwater, to sense their surroundings.

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