How a torpedo works

In movies, you always see a torpedo (the long tube-shaped bomb) hit a ship, then there is a big BANG, a lot of fire and the ship starts to sink.

The way you see torpedos sinking ships in the movies might have been right 70 years ago, but that´s not how it is anymore.

Navy ships are designed with lots of different watertight compartments. This means that if something (like a torpedo) hits them, they just seal the damaged bits and the ship stays afloat. It might be leaning to one side like it´s drunk, but it will still float!

If you are interested in these rockets (because that´s what they are, they just go sideways instead of straight up!) you might like to know a few things about them for your science fair project.

So the people who make modern torpedos came up with some clever ideas. Take the Mk48 for instance. It packs a punch (about the same as a half-ton of TNT) but doesn´t need to slam into it´s target. As long as it is close enough, it uses sonar to aim for the centre of the ship. Then it DUCKS UNDER it. When it gets to about 30 feet under the center of the hull – this depth is really important – it explodes. All that explosive power becomes a HUGE gas bubble that rams into the underside of the ship at about 3 miles per second (that´s fast!).

This bubble bends the ship like a banana, but it´s not over yet. When the bubble shrinks again, it sucks the bent ship the opposite way, bending it again. Have you ever tried to break a bendy stick? You know how it works best when you bend it forwards then backwards, to weaken it? The torpedo does this to the ship. The hull gives out and the ship´s ´back´ is broken so now it can sink.

You can recreate all this at the science fair using basic rocketry principles. Just make sure it´s on a smaller scale and remember, SAFETY FIRST!

So once again, the movies are fun to watch, but not very scientific! Oh, and one more thing: There´s no red flames when a torpedo hits a ship… You only see the explosions in the movies because they look cool!