wrote in message
...
In article , "Keith Willshaw"
wrote:


The Skhval is a short range straight runner that does NOT
home in on the steering gear or screws. The Russian
torpedo that IS dangerous in this respect is the large
Type 53-65 passive wake homing torpedo,

Keith



I find this interesting. What do you mean by "passive wake homing"?

I know what passive guidance means; I'm just not sure what passive
signature a wake-homing Type 53-65 might be guiding on.


There are a number of techniques for detecting wakes which
include detecting the velocity changes caused by eddying in
the wake and also by IR sensors which detect the temperature
changes.

Whichever method is used the sensor looks upward and the rudder is
set automatically to turn the torpedo through a fixed angle
each time the torpedo crosses the wake of its target.
This enables a torpedo to follow a sinuous track towards the ship
(provided it enters the wake at an acute angle).

It is relative simple for the seeker to determine the boundaries
of the wake, which extends many lengths behind the target.
A wake is difficult to simulate, so countermeasures relying on
seduction are ineffective which is why are Navies showing so
much interest in Hard Kill defenses.

Keith