Catapillar Engine

[SubSerpent]

This may have been asked before, but has anyone implemented a working Soviet Typhoon class SSBN with a working catapillar drive similar to that of the Hunt for Red October movie?

[Oberon]

Not that I know of, I think the most they've done on a 'phoon is the prop shrouds.

[kgsuarez]

I don't think it'd be much fun to have such a sub in the game. How would you find it?

[Sea Demon]

We'd have to listen for that rythmic "clicking" sound.....

[Deathblow]

How was that engine theorized to work? Basically internalizes miniture propellars?

[SubSerpent]

The Petty Officer Jonesy character in the movie found it by taping the seismic anomaly noises that he heard and slowing the tape down 10 times which emmiited a noise that had to be man-made that was simply masked by the seismic anomaly sound. Could this not be somehow done? Would make the game much more interesting and that much harder to find catapillar driven subs.

[SubSerpent]

I think that engine was more or less a thruster based on a jet engine structure. Obviously it doesn't produce the amount of noise that a jet emits but it does the same thing in theory by sucking in water and puching it out the back which is a lot quieter than the standard "chopping" at the water using propellars. As the water is pushed out of the "jets" an amplifier within the structure releases a "cover-up" sound such as 'whales humping, or magma being displaced under the sea' in other words a seismic anomaly that does not sound anything like a submarine. This sound would simply flow out the back of the sub to cover up any man-made sound that might be generated by the machine.

[TLAM Strike]

According to the book once our sonar operators learned the characteristics of the caterpillar it became only slightly more effective (at the cost of reduced performance) than the current Russian subs.

Such was life in the cold war.

[Deathblow]

That sounds similar to the modern day "pumpjet propulsors" used on the latest attack submarines like the Astute, Virgiania, Seawolf, and later models of the Tralagar. (Scroll down toward the bottom: http://zone.sousmarins.free.fr/zone%...%20helices.htm ) Basically a series of stators and rotars to optimize the water flow through the propulsor. Of course it isn't the length of the ship, because such a structure would probably be unneccesary and with flow resistence drawbacks, not to mention that at slow speeds the props are only one of several noise sources (reactor coolant pumps, hull vibration, reduction gearing, etc), that would be as/more important to quiet as well.

[SeaQueen]

Originally Posted by SubSerpent

This may have been asked before, but has anyone implemented a working Soviet Typhoon class SSBN with a working catapillar drive similar to that of the Hunt for Red October movie?

As far as I know, no. Back when strange looking pods started appearing on the tails of Soviet submarines, people were very confused about what they were. One hypothesis was that they were some new type of ultra-quiet electromagnetic propulsion system. It turned out they were just the towed array reel.

[compressioncut]

Originally Posted by Deathblow

That sounds similar to the modern day "pumpjet propulsors" used on the latest attack submarines like the Astute, Virgiania, Seawolf, and later models of the Tralagar. (Scroll down toward the bottom: http://zone.sousmarins.free.fr/zone%...%20helices.htm ) Basically a series of stators and rotars to optimize the water flow through the propulsor. Of course it isn't the length of the ship, because such a structure would probably be unneccesary and with flow resistence drawbacks, not to mention that at slow speeds the props are only one of several noise sources (reactor coolant pumps, hull vibration, reduction gearing, etc), that would be as/more important to quiet as well.

No, the "caterpillar" was a magnetic drive that didn't have any moving parts as I recall - pulled water in one end and pushed it out the other in some sort of perstaltic movement. A pumpjet is basically either a really fancy propeller or very simple jet engine, depending how you look at it. They are very heavy (note the trim of that Kilo with the pumpjet), relatively complicated, and don't provide much of an advantage over a good conventional propeller.

Last year some defense contractor put out a press release about a new kind of propulsor they were developing - basically and advanced shrouded prop driven by an electric motor, so that none of the propulsion machinery penetrates the sub's hull. It sounded pretty neat.

[Deathblow]

Originally Posted by compressioncut

No, the "caterpillar" was a magnetic drive that didn't have any moving parts as I recall - pulled water in one end and pushed it out the other in some sort of perstaltic movement.

Sounds weird. One thing I do remember about THFRO when I read that part was that it didn't seem to make any sense at all though I don't remeber what kind of imagined techno-babble they tried.

My understanding is that a pumpjet is a more efficieny propellor because less of the energy off the propellor is lost to rotational swirl of the wake and with a pumpjet the energy lost to swirl is decreased, as well as the fact that the pumpjet blade ends see higher pressures than they otherwise would, decreasing cavitation tendencies.

Last year some defense contractor put out a press release about a new kind of propulsor they were developing - basically and advanced shrouded prop driven by an electric motor, so that none of the propulsion machinery penetrates the sub's hull. It sounded pretty neat.

Sweet, I've been fancinated by the possible performance of high power electric drives for a while now. Mainly how fast they would be compared to traditional drives.

[compressioncut]

Originally Posted by Deathblow

Sounds weird. One thing I do remember about THFRO when I read that part was that it didn't seem to make any sense at all though I don't remeber what kind of imagined techno-babble they tried.

My understanding is that a pumpjet is a more efficieny propellor because less of the energy off the propellor is lost to rotational swirl of the wake and with a pumpjet the energy lost to swirl is decreased, as well as the fact that the pumpjet blade ends see higher pressures than they otherwise would, decreasing cavitation tendencies.

Sweet, I've been fancinated by the possible performance of high power electric drives for a while now. Mainly how fast they would be compared to traditional drives.

Well, the Brits have been using pumpjets since the early/mid 70s (Swiftsure), while the Russians and Americans have been essentially happy to use normal, albeit highly engineered, propellers until very recently. I suspect that the fact they are massive has been the main drawback - if you look at that Kilo with it's propulsor disassembled, the stator section alone probably weighs as much as four or five normal props.

[Deathblow]

Originally Posted by compressioncut

Well, the Brits have been using pumpjets since the early/mid 70s (Swiftsure), while the Russians and Americans have been essentially happy to use normal, albeit highly engineered, propellers until very recently. I suspect that the fact they are massive has been the main drawback - if you look at that Kilo with it's propulsor disassembled, the stator section alone probably weighs as much as four or five normal props.

My guess is that the stators are probably made of steel whereas traditional props are probably titanium. There has to be some tangible advantage to them since everyone is making the switch now. My reading says that a pumpjet can achieve an equal amount of thrust with a smaller diameter than a traditional screw, something about better use of the blade ends for thrust production iirc.

[Bubblehead Nuke]

Originally Posted by Deathblow

My guess is that the stators are probably made of steel whereas traditional props are probably titanium.

Normal screws are made of bronze.The impellors???? no idea..

There has to be some tangible advantage to them since everyone is making the switch now. My reading says that a pumpjet can achieve an equal amount of thrust with a smaller diameter than a traditional screw, something about better use of the blade ends for thrust production iirc.

The noise of the screw turning is more 'channeled' in a fore and aft direction. With the impellor housing you get a baffling effect and that cuts down on your side aspect noise level. One other thing is blade count. What IS the number of impellor blades and how does something like DEMON interprept this into a TPK.