Re: [GZG] Re: Mines

Richard CJ wrote:
> 
> John Tailbey wrote -
> 
> 
>>A modern torpedo has a range of a few kilometres and without the wire
>>guidance from a submarines it has to rely on its own active sonar
>>to acquire its target.
> 
> 
> A few kilometres is understating it a bit. Even 20 yrs ago ranges in
the
> 30-50km bracket were not unusual. Torpedoes can also use passive
systems for
> final targeting to reduce the chances of detection.

Actual ranges are classified. (well Duh...)

A torpedo has X kilometres of wire inside, and the launching sub has 
another Y kilometres in the tube, to allow it to depart the firing point

after launch. The wire remains stationary once it's payed out.

The torpedo can be guided by the sub to distance X, and steered to 
re-attack if it misses the first (or second or third...) attacks, but 
after that the wire can be cut, and it can proceed autonomously.

They normally have at least 2 speeds. Often they'll use the fast speed 
to reach the target area, slow down to reduce self-noise to acquire the 
target (better sonar performance and reduced chance of target detecting 
them), then speed up again for the attack. Sometimes they'll cruise at a

slow speed at long ranges.

Sorry, this is one of the occasions where those who know don't say, and 
those who say don't know.

Source http://www.fas.org/man/dod-101/sys/ship/weaps/mk-48.htm

Range	Officially "Greater than 5 miles (8 km)"

Claimed
	       40 kt	  55 kt
MK-48	      44,550 yd  34,430 yd
MK-48 ADCAP   54,685 yd  42,530 yd

I cannot say whether these figures are accurate or not, merely that FAS 
figures are often wrong, sometimes right, but generally (not always) in 
the right ballpark.

Having worked with the Mk 48, I can't even say if the two speeds listed 
are correct, nor whether the figures above are under wire guidance, or 
"extreme range" before the fuel runs out.

I can say that the shorter the range, the bigger the bang, as the Otto 
monopropellant is a pretty decent explosive in its own right, and at 
short range there's a lot of it.

I've also worked with the SST-4 SEEL, SUT and DM2 A-3 SEEHECHT torpedos.

 From http://www.navweaps.com/Weapons/WTGER_PostWWII.htm

DM2 A-3: 22,000 yards (20,000 m) / 35 knots
Also a lower speed setting for increased range.
DM2 A-4: 55,000 yards (~50,000 m)/ 50 knots maximum speed, different 
speed settings

SUT 24,000 yards (22,000 m) / 35 knots
56,000 yards (51,200 m) / 23 knots

SST-4 12,000 yards (11,000 m) / 35 knots
22,000 yards (20,000 m) / 28 knots
40,000 yards (37,000 m) / 23 knots

Same remarks about reliability of figures apply, these figures may be 
wildly out, or exactly right, or anywhere in between.
These are all battery torpedos, rather than Otto fueled ones.

Passive guidance is only useful at slow speeds, self-noise is a problem.

Active guidance is useful when torpedos are fired in staggered pairs. 
The first torpedo pings and finds the exact position of the target 
(often quite different from where you thought it was), even if the 
geometry is wrong for interception, then the second going slow and 
passive can be steered from the sub till its at point-blank range before

it goes BOOGA BOOGA and it's too late for the target to take 
countermeasures. The first torpedo then probably can't be evaded any 
more by the wounded target, and that re-attacks to add insult to injury.

Of course to do this, you better not be firing at extreme range. The 
closer, the better.

That's about all I'm comfy saying.

Zoe
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