# Underwater projectile affected by Coriolis Effect

1. Feb 13, 2012

### minghia

If I am trying to fire a torpedo at another vehicle underwater do I need to worry about the Coriolis Effect? The speeds that torpedoes travel at are approximately 20 m/s and have a maximum range of around 10km.

Last edited: Feb 13, 2012
2. Feb 13, 2012

### xts

Coriolis effect is even stronger for underwater object than for the one moving in vacuum. But it still is negligible when compared to other forces disturbing the torpedo trajectory (water currents, waves, imperfect geometry, etc.) so since WWI (when torpedos reached range bigger than 1000 meters) all torpedoes are equipped with gyroscopic stabilisation of their course and/or some kind of guidance.

3. Feb 13, 2012

### minghia

I am trying to simulate a firing system for torpedoes and the only positional information I get about the launch vehicle is its latitude. I am curious as to why this is the case. I guessed the targetting solution may be affected by the Coriolis effect. If I wasn't modelling currents or any other underwater disturbance would I need to worry about it?

So if I only plot an intercept course for the target that should be sufficient?

Also is what you are saying about stabilsation true for a torpedo built in the 1970s?

4. Feb 13, 2012

### A.T.

Why?

5. Feb 13, 2012

### xts

@A.T.
torpedo itself is affected by Coriolis force in the same manner as a projectile moving in vacuum. Let's say (we are on Northern hemisphere) to the right. But the water surrounding it flows around in opposite direction. The water is affected by Coriolis force to its right, which causes hydrostatic pressure gradient, giving higher pressure on the left side of torpedo, giving thus additional force pushing it to the right. Actually - I am not able to calculate it precisely nor even to estimate the magnitude of this additional force, but sureley it adds up additional force in the same direction as Coriolis force.

@Minghia: "If I wasn't modelling currents or any other underwater disturbance would I need to worry about it?"
Of course, not. But that means your model is unrealistic.

"Also is what you are saying about stabilsation true for a torpedo built in the 1970s?"
All torpedoes built in 1970' were not only stabilized, but also guided by some system, like sonar, passive sonar, or remote guidance. Guided torpedoes were introduced during WW-II, while gyroscopic stabilisation was added to torpedoe mechanisms as early as at beginning of WW-I.
See wiki: en.wikipedia.org/wiki/Torpedoe

Last edited: Feb 13, 2012