Ruler - old RN anti-torpedo weapon?

eshelon

eshelon

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From one of the comments on http://defensetech.org/2013/10/28/navy-deploying-new-anti-torpedo-technology/

"Right, you know the USN tried fielding a Mk46 mod for this role in 1992, and the Royal Navy had an anti torpedo rocket thrown weapon in the 1950s called Ruler, as well as both fleets doing work in that era on homing weapons (...)"
 
From: http://www.dtic.mil/dtic/tr/fulltext/u2/343269.pdf

In Project Ruler, a British approach, a torpedo was detected by passive sonar. Then
the approaching torpedo was ranged on by an active sonar to obtain fire-control information
which was used to aim and fire a four-barrelled mortar. The weapon range was 600
ft, and each shell had a charge of 200 lb high explosive. An acoustic proximity fuse was
to have been employed. The total weight of the system was close to 26 tons, and there
were difficulties with the fuse. The project was shelved largely because of these factors.
Click to expand...

Also note Project Camrose, from the same source:

In this project,-another British approach, a torpedo was detected by passive-scanning sonar
and if the steadiness of the bearing indicated a possible hit, a salvo of torpedo-like
rockets running underwater were fired to intercept the torpedo. A passive acoustic fuse
was used. Rough range for determining when to fire was obtained by assuming a certain
torpedo acoustic spectral density; then by listening on two separate frequencies and considering
%he relative attenuation, a range estimation could be made. Once again a large
head for each rocket (200 lb high explosive) was required. Once again total weight of the
system became prohibitive and the project was dropped.
Click to expand...

Additional Camrose information is available here: http://www.geoffkirby.co.uk/rocket-torpedoes.pdf

There is also a section in Warship 2007 dealing with both projects, it includes photos of a model of HMS Relentless with a Ruler launcher (4 barrels side-by-side) forward of the bridge and a single barrelled launcher either side of the bridge (though I can't make out the latter- I can only see what look like single bofors mountings).
 
JFC Fuller said:
There is also a section in Warship 2007 dealing with both projects, it includes photos of a model of HMS Relentless with a Ruler launcher (4 barrels side-by-side) forward of the bridge and a single barrelled launcher either side of the bridge (though I can't make out the latter- I can only see what look like single bofors mountings).
Click to expand...

->>> link
 
Interesting to find out more information about Ruler and Camrose. Along with Bidder and Fancy these were technologically advanced programmes that were obviously pushing sonar technology to its limits.
The Warship 2007 article is the first time I ever seen a model of Ruler as opposed to basic side-elevations on plans (although I had assumed an in-line arrangement). It looks a hefty bit of kit and retrofitting it to destroyers and frigates would probably have been problematic and would have resulted in sacrificing at least one gun turret in most conversions. The Relentless model is interesting but surely a Type 15 retrofit would have been impossible unless the conversions kept the forward magazines of the original destroyers? Did they have provision for forward magazines?
 
That was my comment. The RN concluded that false alarms would make a ship unable to cross the Atlantic one way without running out of ammunition, and so work shifted towards better towed decoys. Friedman's postwar British destroyers volume talks about it a little. This is why no active anti torpedo system has been fielded by any nation until recently; except for the Soviet RBU-1000 system which was only intended for countering relatively predictable wake homing torpedoes. It was meant to fire first floating decoys, then floating mines and finally exploding charges at point blank range. Effectiveness unknown, but only a few NATO wake homers ever existed anyway. It could also shoot decoys for active/passive homers which was likely more useful. Torpedoes are just not that loud compared to other ocean noise, and it does not help that you might have friendly ASW torpedoes in the water on a regular basis, convoy noise and the ship itself entering into evasive action any time it does suspect a torpedo is incoming.

The various Cruiser-Destroyer projects usually showed one Ruler launcher with 20 rounds. Sucker was big as well as heavy.
 
Re-reading Friedman's 'British Destroyer and Frigates', I noticed he does indeed mention that the Type 15, "design included an allowance for a future anti-torpedo weapon." Whether that was Ruler or Camrose is open to interpretation as is where they would have been located. Friedman also states that the planned Type 12 Stage III would get Ruler and its associated Type 176 passive sonar (and the Types 172 and 177 sonars). Again where is open to question but given the placement on the Cruiser-Destroyer and likely torpedo attack angles, aft was probably the most ideal place. That might replace the twin 40mm on the Type 12 and the twin 4in on the Type 15 perhaps.
The Draft Staff Requirement TSD 147/49 for the Cruiser-Destroyer on 18 January 1950 called for an anti-torpedo weapon which Friedman states was, "later specified as Double Ruler (a rocket launcher)." Does this imply the four-barrelled mount finally shown on the plans was a bigger version and that the single tube mentioned above on the Type 15 model was a basic Ruler launcher (or perhaps plans for a smaller two-tube version)?
 
I would suggest, based on the model shown in Warship 2007, and the unlikelihood of the RN being willing to sacrifice either the 4" gun or the 40mm bofors that in the Type 15s, it would have gone forward.

One of the reasons for the abandonment of Ruler and Camrose include the lack of sonar coverage to the stern of the ship.
 
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I would concur with that, simply because there was nowhere else for it (though given the declining value attributed to the 4in as the 50s went on its plausible they may have envisioned its eventual replacement), despite the lengths gone to clear the forecastle and make the ship suitable for driving into head seas. The later frigate-style bridge fitted to the last few Type 15s would have been ideal to see over the Ruler had it been fitted. The model and Friedman's comment seems to indicate perhaps space was left for a magazine forward (perhaps converted oil stowage), at least in the initial design.
 

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