Torpedoes - experts needed

[Dr.Sid]

Hi .. it's me again being curious.

Does torpedoes have up and down side ? Are the supposed to swim in water with some orientation ? Or do they simply navigate in 3d, with symmetric sensors and ignore any bank (listing) ?

Do some torpedoes have bottom sounding ?

[SeaQueen]

The physics of underwater sound would imply that acoustic homers would have an asymetrical "cookie cutter" sensor, both vertically and in all likelyhood horizontally. Their sensors are just like any other sonar except higher frequency due to the size of the array you can fit in a torpedo's nose.

Originally Posted by Dr.Sid

Hi .. it's me again being curious.

Does torpedoes have up and down side ? Are the supposed to swim in water with some orientation ? Or do they simply navigate in 3d, with symmetric sensors and ignore any bank (listing) ?

Do some torpedoes have bottom sounding ?

[Dr.Sid]

I mean .. do the torpedoes rotate along it's main axis without relying on some orientation or are they stabilized to have one side always up ?

Btw. sorry for my incompetence but what do you mean by 'cookie cutter' ? Only possible meaning I found is 'without original conception' .. which gives some sense but not really.

[Frame57]

Hi Sid, ran this one by a TM. It was explained to me that the guidance is X-Y. The (MK-48) will change depth in a vertical way and course in a horizontal way. Keep in mind I am only a knuckle dragging Machinist Mate, so I tried my best to explain to him what you are asking, but this is all I was able to get out of the fellow. from his experiences he did not think that there was any other dimensional or spatial ability in how a 48 gets from point A to B. I am surprized that there are not any TM's on this site. I know there are a few of us bubbleheads here. But then again, I am not sure if it is classified material. But if you ever have a question about submarine hydraulic systems, boy I can chat ya up on that one. (yeah right!)

[Dr.Sid]

Well I would bet on the strictly 2d, bank stabilized navigation too. Depth reader can be bank independent but then you have to steer up/down and you must know which direction it is.

I guess the stabilization must be active because torpedo can spin too easily with no extending planes and only little room for low-center-of-gravity based stabilization. And if it had low center of gravity it would bank into turn as sub does and then it would have little means to stabilize again.

As for propulsion, most types are gravity independent, and negative G would happen .. but some types can handle the negative G only for short amount of time. Also I guess some orientation would be important during storage, because of batteries, fuel tanks and so on.

So at the moment I think it is stabilized because it can help the navigation and some types of propulsion. The stabilization is done actively by steering planes based on some sensors (probably 3d gyros reset at launch). Center of gravity would be intentionally neutral (exactly in the axis) so torpedo does not bank in turns.

It would also mean there is some 'this side up' label on the torpedo.

[Bill Nichols]

Originally Posted by Dr.Sid

It would also mean there is some 'this side up' label on the torpedo.

Yep.

[TopTorp '92]

Do understand correctly? Are you asking how the torpedo knows which way is up once it is fired into the ocean?
Both MK 48 and ADCAP have internal gyros that tell the weapon where to go as well as how to correct for changes in pitch and roll. The only caveat is that significant pitch/roll deviations will result in an internal shutdown before the weapon enables.

[Dr.Sid]

I mean if there is some bank held at all or if the torpedo is let to bank freely.

Anyway it's quite clear now that the bank is fixed. Thanks !

[TopTorp '92]

Originally Posted by Dr.Sid

I mean if there is some bank held at all or if the torpedo is let to bank freely.

Anyway it's quite clear now that the bank is fixed. Thanks !

It banks freely
TopTorp

[Dr.Sid]

Lol .. it was clear .. until now. You said:

1) The only caveat is that significant pitch/roll deviations will result in an internal shutdown.

2) It banks freely.

As I understand it these two are contradicting. Or maybe you don't mean bank & roll to be the same as I do ?

[TopTorp '92]

Originally Posted by Dr.Sid

Lol .. it was clear .. until now. You said:

1) The only caveat is that significant pitch/roll deviations will result in an internal shutdown.

2) It banks freely.

As I understand it these two are contradicting. Or maybe you don't mean bank & roll to be the same as I do ?

Shutdown is tricky, so I didn't really address all of the caveats. Also, I'm operating on decade old memory. So, just bear with me.

There are two systems protecting own-ship from a faulty torpedo that may turn and come after the home team.

From the moment the weapon is fired (TOF-Time of Fire) to the enabling point, that is the weapon slows to search speed, ACR (for anti circular run) protects ownship. This is the "internal shutdown" I referenced above. After the enabling point, ACR becomes disabled. ACR shutdown limits are technical and I no longer remember them. Pitch/roll is +- 5 degrees, I think. Gyro deviations are +- 168 til the first gyro null and then +- 5 degrees til enable.

After the enabling point, there is an additional safety feature for Mk 48 called ASH (anti self homing.) It is a discrete setting in the torpedo meaning it is either set in or out. It's too complicated to explain how it works because it uses counting system that counts twice as fast if the weapon changes course by a predetermined amount.

ADCAP is a digital weapon and no longer needs to know how to count the old MK-48 way. It uses FENCE after the enabling point and this feature not only protects ownship from a torpedo coming after ownship it also has lateral limits that prevents the weapon from homing on targets outside the lateral limits. Basically the weapon swims around in a digital box defined by the weapons operator. Any target outside the box is off limits. The idea is to protect hospital ships or if using the weapon in littoral waters, then the latteral FENCE settings may protect nearby civilian shipping.

The weapons operator may override both ASH and FENCE after TOF if the guidance wire remains in-tact. Unfortunately, if the wire breaks during an override command, then the safety feature remains permanently overriden til the weapon either runs out of gas or blows up.

To answer your original question, the weapon rolls freely after the enabling point has been reached. However, during the enabling run, there are safety limits that will shutdown the weapon if exceeded. It depends which phase you're talking about.

TopTorp