Prairie/Masker system question

I believe the lafayette does have some measures to control thermal and sound like vibration isolated machinery mounts and seawater spray cooling of engine exhaust…or is it my P17 fetish acting up again ?

Sounds reasonable then. I just seems odd on a ship that cuts corners to save cost in many respects.

Not to me, since designed for low RCS it would be silly to subsequently give oneself away by high thermal, sound or EM signatures

Sounds reasonable then. I just seems odd on a ship that cuts corners to save cost in many respects.

What do you mean? The Lafayette class is primarily a patrol vessel that in war will perform escort duties. For those roles it is equipped just fine. The class does have the space set aside for more systems at a later date but for now its just not affordable for every vessel in a fleet to cruise around with 16 AShMs, hulking great VLS’s with dozens of AA and LAC missiles and an artillery battallion’s worth of NGFS capability. Consequently those systems are not on board and thats fine since they don’t fit the vessels role. However something that improves your chances against submarines, now thats something that fits the role and is therefore a perfectly reasonable inclusion.

Daniel

Sounds reasonable then. I just seems odd on a ship that cuts corners to save cost in many respects.

Seems unlikely given that La Fayette, using a CODAD powerplant, does not have any gasturbines as ready sources of bleed air. IIRC Udaloy has a Masker-type system but no such system on the props.

A special-purpose air system installed in many surface ships is the prairie-masker air system. This two-part system supplies a high volume of low-pressure air to a system of emitter rings or belts surrounding the hull and to the propeller blades through the hollow propulsion shafts.

The air supply for the prairie-masker system is provided by a turbocompressor. On ships with steam propulsion plants, the turbocompressor is composed of five major parts contained in one compact unit. They are the turbine-driven com-pressor, lube water tanks, air inlet silencer, lube water system, and control system.

The turbine-driven compressor consists of a single-stage centrifugal compressor driven by a single-stage impulse turbine. The compressor impeller and the turbine wheel are mounted at opposite ends of the same shaft. Two water-lubricated bearings support the rotor assembly.

The compressor runs at speeds approaching 40,000 rpm. A control system for the unit provides constant steam admission, overspeed trip, overspeed alarm, low lube pressure trip and alarm, and a high lube water temperature alarm. On ships with gas turbine propulsion plants, air from the prairie-masker system is taken from the bleed air system of an on-line gas turbine.

http://www.tpub.com/engine3/en33-72.htm

Seems to me as long as you have an adequate compressor and a source of air, you’re in business, regardless of type of propulsion machinery installed

wake homing torpedoes like the big Ru 26″ Type65 use a optical sensor to look up and sense the disturbed optical pattern caused by a ships normal wake. the kind of bubbles this system generates looks like a red rag to a very angry bull.

I guess ideal strategy is fire a couple of normal deep running sound/MAD fused torps to
act as ‘beaters’ and force ships to turn the bubbles on, then release the bigstick wake homers 😀

USN has experimented with CH53 helos hovering over a ships wake then slowly moving
on another line creating its own wake to decoy wake homers. dont know how successful that strategy is considered.

I’ve seen a reference on Wikipedia claiming the system on board french La Fayette ships but not. That information probably came from Net Marine sure if this is really the case. Any navy operating OHPerry, Spruance/Kidd/Ticonderoga and Know/Baleares classes of ships probably has it. Likewise A.Burke class and derivatives (e.g. Japanese Kongo class, KDXIII). I would think other JMSDF have it too. Italian ships like Guiseppe Gariable CV and Durand de la Penne DDG have it as well.

Seems unlikely given that La Fayette, using a CODAD powerplant, does not have any gasturbines as ready sources of bleed air. IIRC Udaloy has a Masker-type system but no such system on the props.

Do any subs have this ? I guess noise and the amount of oxygen needed could be an issue ?

Now imagine you’re a satellite looking for wakes. . . 😮

So, this system isn’t necessarily a quieting mechanism, it’s more of a way to mask the exact signature of the boat. So that the ship class/name isn’t given away by the noise. Is that correct? I would assume that all those bubble breaking the surface would produce a lot of sound and in the process mask the machinery sound of the ship. In essence an acoustic version of ECM?

Can’t be too noisy other wise it degrades the ship’s sonar performance.

So, this system isn’t necessarily a quieting mechanism, it’s more of a way to mask the exact signature of the boat. So that the ship class/name isn’t given away by the noise. Is that correct? I would assume that all those bubble breaking the surface would produce a lot of sound and in the process mask the machinery sound of the ship. In essence an acoustic version of ECM?

With and without: compare the wakes.

A picture tells a thousand words ………………….. 😀 😎

Here’s a pic

http://www.navy.mil/view_single.asp?id=2184

Its actually not that new. If you go to the national maritime museum in Greenwich in London, there is a real Frigate Propeller on display that has it, and explains how it works, although not in as much detail as the attachment above.

USN large combatants seem to have this air bubble system by default

http://www.fas.org/man/dod-101/sys/ship/weaps/prairie.htm

do other navies of the world use similar system ? any examples ?

Israeli Sa’ar 5 have the same system as did the Canadian Halifax class ships (these systems were deactivated in 1998 when the Canadian Navy determined that the operating costs of this system outweighed the benefits).
I’ve seen a reference on Wikipedia claiming the system on board french La Fayette ships but not. That information probably came from Net Marine sure if this is really the case. Any navy operating OHPerry, Spruance/Kidd/Ticonderoga and Know/Baleares classes of ships probably has it. Likewise A.Burke class and derivatives (e.g. Japanese Kongo class, KDXIII). I would think other JMSDF have it too. Italian ships like Guiseppe Gariable CV and Durand de la Penne DDG have it as well.