Ideal PLAN submarine

Ok, here it is, Sun Tzu class strike sub.



The hull itself is a lengthened Kilo, generally analogous to the Russian/Indian Amur class. But in terms of layout, the missile tubes are forward of the bridge, and angled about 20 degrees to allow them to not interrupt the lowest deck. The ten tubes are over-sized allowing a wide range of weapons/UUVs to be carried.

The missile tubes require the forward hull to have a bulbous profile, which also allows a relatively elevated yet forward placement of the bow hydroplanes.

Another characteristic is that it lacks a conventional torpedo room - again following the trend of the Amur class even the forward firing 533mm torpedo tubes are preloaded. In this sub they are mounted outside the pressure hull (as per the additional tubes on the Akulas). This has some difficulties with reloading, but reduces the crew by about 15 and increases usable space, at the cost of rounds carried.

I've also given it a Type-212/4 style blended bridge, and a large diameter (i.e. slower turning?) pumpjet propulsion - Towed devices in both fin-top and rear of pumpjet.

AIP... I presume so.

Very nice, but can you do an assymetrical screw version instead? I've determined that one reason why conventionals don't do pumpjets is because these are much heavier than a conventional propeller due to having more blades. The combination of having more blades and the weight makes it more difficult to turn, requiring more torque and power that are more typical of a nuclear submarine than a conventional. Unless for some reason we can build a more powerful electric motor for this. If we use reduction gears we may end up making noise on the gears counteracting whatever improvements in silence the pumpjet would have made.

I like your nose arrangement because although you did not intend it to be, at least consciously so, the way you put the nose allows for a spherical array bow antenna like the BQS-5. The advantage of having a spherical array, is that it offers a large field of view. You can modify the nose to reflect use of a spherical array.

Relative to Spherical arrays, planner arrays are better still, but some way off apparently.

Wow that is much better.

I don't know much about hydrodynamics, but I noticed that in the latest sail design, the corner in teh front part of the sails are now curved and blended to the hull, but they prefer to keep a sharp cutoff on the rear of the sail. Your design reflects that.

Which is better, conventional or "X" fins at the back? Gotland, Type-212 use X and they are highly regards.


Also, having browsed Azipod/et al I can't see why direct drive isn't already possible for subs. I'd be willing to sacrifice speed for quiteness.

And another thing, there are quite a few examples of SSKs with ducted propellers, not just nuclear boats. Examples include the NKorean Sang-O class and Chinese Romeo class off the top of my head.

I think direct electric drive ducted prop is way forward - quiteness before speed.

planeman said:

Which is better, conventional or "X" fins at the back? Gotland, Type-212 use X and they are highly regards.


Also, having browsed Azipod/et al I can't see why direct drive isn't already possible for subs. I'd be willing to sacrifice speed for quiteness.

And another thing, there are quite a few examples of SSKs with ducted propellers, not just nuclear boats. Examples include the NKorean Sang-O class and Chinese Romeo class off the top of my head.

I think direct electric drive ducted prop is way forward - quiteness before speed.

Click to expand...

X-form fins are better for shallow water operations, of which nuclear subs aren't that capable in.

A nuclear sub's strength is speed. A turbo-electric power plant is larger, heavier than a traditional powerplant. It has been trialled by the USN (USS Glenard P. Lipscomb and USS Tullibee), but the trials were not successful; the design was not very reliable, and suffered from the aforementioned issues. You loose around 50% in speed with a turbo electric drive. As a result from these trials, the USN went conventional for the LA boats.

The Walrus class also uses X fins. But these, the Gotland and the Type 212 are really small coastal subs. If you look around, subs like the Kilos, Songs and Yuans are larger. These subs can already be considered borderline littoral/blue seas.

i don't know how a turbine electric drive ends up being bigger. The French Rubis class uses them, and they're the smallest nuclear subs around---they're only as big as many of the larger sized conventional boats, not much bigger than a Yuan or Kilo in fact. As a matter of fact, all conventionals are essentially electrically driven when underwater.

In fact, the USS Tullibee is only 2300mt surfaced, as big as any conventional, which is not bad for an early generation nuclear sub. The sub is reputed for its quietness. Nowadays, quietness seems to have a greater precedence over speed.

Some earlier subs uses ducted propellers, but if you want to be quiet you want to use more blades so you can move more water for less propeller revolutions. Romeo and Sang-O are not exactly the most quiet subs around. The Russians tried to use a pumpjet with a ducted propeller design on one of the Kilos---that same sub now has this pumpjet removed. So far no one else is trying to drive a conventional with a pumpjet, so I guess there are some issues behind this.

I was thinking in terms of taking a hacksaw to an "Azipod" and grafting it onto the tail of a sub. No gears... less noise?

Also, is it possible to produce bubbles amidship to quiten the sub?

And is there potential for a semi-cavitating devise to reduce friction, used for economy rather than speed?

It should be noted that the Typhoon class uses two ducted propellers according to a photo I've seen.

Here is some research on the topic with ducted propellers.



The idea of putting a shroud around a propeller is very old but it was only in 1934 that Stipa and Kort showed that a practical propeller of this design was possible. Kort designed a whole series of ducted propellers which proved very valuable when used in ships like tugs, pushboats, supply ships, trawlers etc. For this reason, his designs became known as Kort Nozzles.

His breakthrough was to shape the shroud around the propeller like an aerofoil rather than a simple ring. If the high-pressure side of the aerofoil faces outwards (so the top is like an aircraft wing right way up), the duct is of the decelerating type. If the low pressure side is outwards (so the top is like an aircraft wing upside down) the duct is accelerating. An accelerating duct produces positive thrust and increases the efficiency of heavily-loaded props (a heavily-loaded prop is one where the power being put through it is close to the maximum absorbable for that prop design). A decelerating duct produces a negative thrust and is valuable for reducing cavitation. A decelerating duct is a major contributor to noise reduction which is why it is getting more popular with modern warship designs.

The major problem with ducted props is flow separation. This causes the drag of the whole system to increase sharply, efficiency drops and the propeller tries to work in a highly irregular flow. This is bad. A mass of work has been done on the standards for ducted propellers and a number of "optimum" units designed. These are referred to by numbers, the simplest member being Nozzle No.19A. Nozzle No.22 for example, has a longer shroud in proportion to the prop diameter and is more efficient but gives poor backing characteristics. If a commercial designer wants to use Kort Nozzles, he'll decide on the characteristics he wants then selects the appropriate nozzle.

In summary, ducted propellers are well suited for situations where the propeller has to accommodate heavy loads. However, such prop designs cannot work safely without flanking rudders for the prop race since ducted props give virtually no backing control. In passing, flanking rudders are a pretty good idea since rudder control on ships doesn't usually work below around 10 knots and under this speed ships have to steer using their engines. While no great problem with twin and quad screw configurations, this is impossible with single screw ships. In this case, flanking rudders can offer some element of control at low speeds. In passing, German S-boats used a rudder trick (called the Lurssen Effekt) to push their sterns down and thus get slightly better efficiency for their props.

A pump jet is a developed Kort Nozzle in which the shroud is extended and fixed guidevanes are installed fore and aft of the propeller. The duct diameter increases from the entrance of the duct to the propeller so that the velocity of the water falls and the pressure increases. This means that the prop diameter is larger and the thrust loading drops. A lot of the design art in this area is classified and the only treatment available in open source comes from Henderson in 1963.

according to european naval commentator, claim that China make tremendous break through in the development "magneto propulsion drive"
this form of propulsion was first install by the soviet typhoon class submarine.