'Alfa' appendages

[zoidberg]

While chasing down 'rabbit holes' this am, I came across a short feature on the Soviet 'Alfa' titanium subs.... all now withdrawn from service AFAIK..... Welded titanium hulls

I'm aware there's a small handful of ex-submarine service types on 'ere - although none admitting to service on an 'Alfa' - so I have a question that likely does not contravene the OSA1989.

This pic of an 'Alfa' on the slipway shows a pair of bulbous installations out on the ends of the horizontal stabilizer, each wih a two-blade prop. Being the nosy sort I am, I fell to wondering what might be the function....

The props are too small to effect propulsion ( I presume ) but may possibly assist low-speed manoeuvring.
They may be used to generate secondary electrical or hydraulic power, using water flow.
They may be associated with defensive towed arrays, since they would make some 'prop noise' if spinning on the end of a long cable, like last century's Walker Logs.

Any better-educated guesses?

 

[Deleted member 36384]

And I thought this was going to be a thread about the size of ones stern gantry and the number of accessories as a dominant show of alpha prowess in marinas.

 

[Stork_III]

Well Wiki says.....

"Propulsion was provided to the screw by a 40,000 shp steam turbine, and two 100 kW electric thrusters on the tips of the stern stabilizers were used for quieter "creeping" (low speed tactical maneuvering) and for emergency propulsion in the event of an engineering casualty. Electrical power was provided by two 1,500 kW turbogenerators, with a backup 500 kW diesel generator and a bank of 112 zinc-silver batteries "

 

[Daydream believer]

Catching lobster pots.. A lot of sail boats have started to develop similar technology with the "twin rudder" system

 

[Tranona]

Well Wiki says.....

"Propulsion was provided to the screw by a 40,000 shp steam turbine, and two 100 kW electric thrusters on the tips of the stern stabilizers were used for quieter "creeping" (low speed tactical maneuvering) and for emergency propulsion in the event of an engineering casualty. Electrical power was provided by two 1,500 kW turbogenerators, with a backup 500 kW diesel generator and a bank of 112 zinc-silver batteries "

Bit like trolling motors on a bass fishing skiff then!

 

[zoidberg]

"Propulsion was provided to the screw by a 40,000 shp steam turbine, and two 100 kW electric thrusters on the tips of the stern stabilizers were used for quieter "creeping" (low speed tactical maneuvering) and for emergency propulsion in the event of an engineering casualty. Electrical power was provided by two 1,500 kW turbogenerators, with a backup 500 kW diesel generator and a bank of 112 zinc-silver batteries "

Thanks. Had I been properly awake, I might have hunted that out for myself.

So the system is the origin of the 'Worm Drive' concept featured in Tom Clancy's 1984 book 'The Hunt For Red October'.... probably. Yon author had his 'finger on the pulse' in numerous situations.

 

[johnalison]

They look very small to be driving such a large object, even at creeping speed. I would have thought that a larger folding or feathering prop would have been more effective, but that may be why I have never been asked to design a submarine.

 

[zoidberg]

JohnA, I'm going to do a little speculating now.... something I rarely do on a public platform such as this!!

[speculate] Submariners are about the most tight-mouthed military types I've encountered anywhere, including Trappist and Jesuit Confessors. So this isn't derived from 'attributable knowledge'....

That 5-bladed prop the 'Alfa' was equipped with was designed with 'high-speed dash' in mind, with up to 40,000 shp driving it. That would be the most acoustically noisy thing in the ocean, for many dozens of miles, even when operating at relatively low power.

One technique used then and AFAIK still by submariners is the high-powered dash at speed, then 'turning down the wick' and coasting off at right angles for a mile or three very quietly, all the while listening for the sounds of pursuers. A trailing passive array would help give a quite accurate picture of who else was around and following. It was not unknown to do a complete 360 degree wide-radius 'quiet' turn - which is a very normal behaviour for any predator.

One problem with that is ( was ) that some positive motion is required to maintain flow over the 'planes, which keep the vessel level and pointing in the required direction. Those small 100kW electric thrusters would do that job very quietly, perhaps using the batteries, while keeping the sub 'manageable'. [/speculate]

 

[penfold]

Other than the whizzo titanium hull the Alfa was a load of junk, propulsion louder than the Parkhead forge beating out a gun barrel and molten lead reactor cooling which is exactly as impractical as you think it is and then some.

 

[Buck Turgidson]

Not a submariner but coastal command.
It doesn't matter what they were for. We knew the frequency.

 

[zoidberg]

C'mon, yooz guys, 'specially 'kipper fleet''. Gimme more!
Otherwise we may revert to another 'ouroboros' anchor argument....

 

[Neeves]

Let's revert - I know nothing about submarines.....

maybe that is the required qualification to contribute



And I wondered why fancy (?) red Italian motor vehicles had strayed into a boating forum.

Jonathan