gradenko_2000 posted:

hankor posted:

Do torpedos only use sound to find their targets? I don't know the first thing about submarines or electromagnetic fields but shouldn't a big steel tube full of electronics give of a signal that could be followed?

Sure it wouldn't be as efficient as targeting a sound source since it's projected over a bigger area but as a support system it could prevent the torpedo from chasing bubbles if there is no corresponding electromagnetic field.

voting3 drop bubbles and walkie talkie.

Yes, torpedoes only ever home in using acoustics. The Soviets use Magnetic Anomaly Detection technology to find entire subs since they're generally huge tubes of steel, but the range and precision aren't high enough to use it to actually hit subs. I believe the equipment for MAD is also so large that you can't feasibly fit it onto a torpedo.

I'm not sure how different Soviet torpedoes work, but in the case of the US Navy's Mark 48, it generally begins with the firing submarine acquiring a good targeting solution. That is, you know the target's course, range and bearing.

When you fire off your torpedo, it's actually linked to the submarine via a very thin wire. They do this because if a torpedo is traveling at high-speed, the cavitation means the sensor on the torpedo itself can't hear shit, so it's up to the submarine to act as a kind of mothership to guide the torpedo on its way to the target.

Once you get close enough (or the guidance wire is cut for one reason or another, usually due to drastic maneuvers on the part of the firing sub), then the torpedo switches from 'passive' sonar, or listening to its environment, over to 'active' sonar, or sending out pulses of sound and checking what echoes back. By the by, a noisemaker can still work against a torpedo even if it has already gone active, since the cloud of bubbles will act as a sort of wall to block the sonar pulse.

Torpedo trivia: The Soviets designed a 'wake-homing' torpedo, or a torpedo that runs at about 40-50 knots, faster than any warship, and homes in on the turbulence left by a ship's wake. It had a 500 kilogram warhead and was designed to kill US fleet carriers in a single hit. The idea was that you'd shoot it from a relatively long distance even if your solution was not very precise, because you can't miss something as large as the wake left behind by the USS Nimitz.