So You Need To… Watch on YouTube

So you need to

How things actually work.

Cutaway from the video: How a submarine dives

It weighs thousands of tons, and right now it floats like any ship.

  1. So you open the vents on top. Air rushes out of the ballast tanks, and seawater floods in.
  2. But if it's even slightly too heavy, it never stops sinking.
  3. So trim tanks pump water in or out until the sub weighs exactly as much as the water it pushes aside. Now you hover.
  4. But every ten meters deeper, the sea squeezes with about one more atmosphere.
  5. So the crew lives inside a thick, round steel pressure hull that spreads the squeeze evenly.
  6. And to come back up, you blast high-pressure air into the tanks and shove the water out.

Water in, you sink. Air in, you rise. Get the balance just right, and you hover.

All videos

About

So You Need To… is a YouTube channel of short 3D explainers. Each video picks one problem, like stopping a river or landing a jet on a ship, and shows how it's done, with the machine cut open so you can see the parts that are normally hidden.

The facts in each script are checked before it's recorded. If you spot a mistake, leave a comment on the video.