Shipbucket

Great drawings and nice backstory.

Re: Igla
So You decided not to go in similar direction?:

(SLAM - navalized Blowpipe tested on HMS Aeneas in 1972)

ah, minimium diving depth was my inquiry that offers far more practical information of these type of boats operational flexibility in areas like Baltic, where the maxium depth is most likely never achieved. 300m is usually the maxium depth of modern submarines.

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Shipbucket mainsite, aka "The Archive"
New AU project "Aravala"

Hah. Got that the wrong way around, chief. Assuming you mean the lowest water depth in which it can operate dived, I would guess somewhere between 15 and 20m.
Does that make sense? That's hull height, superstructure height, some periscope length, a couple of meters' safety margin at the bottom. The absence of a reinforced laying-down keel like on some modern Swedish or German subs is partly compensated by the LIDAR and HF obstacle-avoidance sonar and the retracting auxiliary propulsors for fine maneuvering and station-keeping. Now that you mention it, I'm wondering how much this design looks like a scaled-down blue-water sub rather than a competent green-water one, particularly the SN version. Ah well. I'll have more SN-oriented, smaller classes to take up the slack anyway.

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Soviet Century/Cold War 2020 Alternate Universe: Soviet and other Cold War designs 1990-2020.
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Speed had long been a critical design goal for anti-ship attack craft, from their early torpedo days to the more advanced missile carriers of later days. Its pursuit had driven designers all over the world to some exotic solutions, most of which were less than satisfactory. Gas turbines were expensive and finicky fuel-guzzlers, planing hulls were unstable and lacked resilience, hovercraft were impractical and unreliable, and hydrofoils made up for their high speed in fair weather with disproportionate hindrances to low-speed cruise and handling in heavy seas.
Soviet shipbuilders had been at the forefront of this design effort since the late 1940s, coming up with some of the most outlandish ideas to be applied to that domain. One of those was the cavity-foil catamaran, also called catamaran hovercraft, that first appeared in the mid-1980s on the Project 1239 missile ship and would soon find wider adoption in other countries.
The Project 1239 "Sivuch" was a massive 1000-ton missile ship carrying the same awe-inspiring anti-ship loadout as the Project 956 destroyer, except at a speed of 45 knots. For all its punch and mobility, the Sivuch was costly and complicated to manufacture and maintain. Coupled with the rapidly evolving surface warfare systems of the 1990s, this meant that only two ships were delivered to the original specification. After all, such a high-end unit could ill afford to expend its outstanding mobility on outdated weapon systems.
Still, the premise was considered sound, and design work went on feverishly to increase manufacturability and reliability of the cavity-foil hull. In the meantime, within the limbo created by the absence of a new missile ship design, production went on with a Project 1239.1 variant carrying the newer Oniks missile system and a more modern air defense suite.

Pr.1168

The original layout of Project 1239 soon turned out to be inadequate for the integration of more modern weapon systems. specifically, the hull layout didn't leave room for vertical-launch tubes for the massive AShMs of the Oniks and Biryusa families. While the few original Pr.1239 ships would be modernized along the way, a new design was pushed forward that integrated the new vertical missile launchers directly in the side sponsons. A more advanced and compact propulsion plant would allow the ship to carry the newly-developed anti-ship loadout, i.e. the 18 Oniks missiles first installed on the Pr.1244.1 frigate. The rest of the layout was similar to that of the Pr.1239.
This similarity meant that the new class remained as overly expensive and complicated as its predecessor, and production rate remained dismal, with only three boats delivered in 8 years, each taking 4 between keel-laying and IOC.
In the end, the finished ships would have a lot in common with the bigger and slower Project 1166.4R frigate developed in parallel, with both classes often operating in parallel in the Soviet coastal defense squadrons. The cavity-foil classes would spend more time pier-side than their frigate counterparts to save on maintenance, adopting an "interceptor" mission profile not unlike that of the Pr.705 "Alfa" attack submarine, rushing out of their bases at high speed when summoned by the scouts in their units.






Pr.1168PL

While the cavity-foil catamaran missile ship evolved slowly towards a more frigate-like outlook, some within the Soviet Navy were pushing for a dedicated anti-submarine variant. In the past decades, a few experimental high-speed small anti-submarine ships (MPK) had been produced, mostly using hydrofoil systems. Variants of projects 1141 and 1145 had also been part of this development effort and became the first boats to deploy the RPK-9 anti-submarine missile system, paradoxically sealing the fate of the high-speed MPK concept, although this would only become apparent years later.
In the 1990s, with stand-off ASW missiles getting more efficient and widespread, two development tracks were started: while low-displacement, high-speed MPKs carrying the RPK-9 would evolve from Project 1145, the same missile system would be taken advantage of to develop larger and better-equipped MPKs, for all intents and purposes resulting in a new generation of ASW corvettes. Work proceeded with a classical displacement-hull ship that would result in the Project 622, and a parallel effort towards a high-end high-speed counterpart started with the Pr.1168 hull rather than from scratch.
Though the replacement of the anti-ship weapons systems with the current ASW equivalent posed little problem, the integration of helicopter facilities on such a small and cramped hull did not go without difficulties. Adding a hangar was made impossible by the extensive air intakes of the turbine propulsion plant, and support for the on-board helicopter was therefore limited.
In the end, the project foundered under the weight of its own contradictions. The helicopter-equipped 1000-ton-class MPK concept would soon gain traction, but the Pr.1168 was far from the ideal platform for it, and could only offer a paltry warload to compensate for its enormous operating costs. Cheaper and more straightforward hulls were preferred at every turn for the coastal ASW mission, and the helicopter-carrying hover-catamaran would have to wait for its day in the limelight, rearing its finicky, gold-plated head once more under the guise of the Project 1223 frigate, for barely better results.
In the meantime, the proliferation of long-range ASW missiles fired from multi-role launchers, coupled with on-board armed ASW helicopters and better-ranged sonars, finished undercutting the whole high-speed MPK concept, making flank speed proper a moot proposition when even corvette-sized ships could hunt down submarines several dozen miles ahead of its course.

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Soviet Century/Cold War 2020 Alternate Universe: Soviet and other Cold War designs 1990-2020.
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Very nice follow on for Pr.1239, a design I always liked and gives me inspiration for creating a "Western" equivalent design.

Most EXCELLENT work CL.... Very Impressive, as always

Jolly WELL DONE sir.... I really can't wait to see more of this truely outstanding thread

A pat on the back my friend

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Excellent additions, suitably problematic given their complexity but just the thing the Soviets probably would have played around with trying to make the concept work.

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English Electric Canberra FD
Interwar RN Capital Ships
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Never-Were British Aircraft

Another fantastic addition.

excellent design.

But:

I am not sold on a ship that weight 950 tons have 36000 hp and conventional propellers shall manage 50 knots. on a vessel that is just over 60 meters long.

Just look at skjold class, they are a 274 tons heavy vessel with 16100 hp and manage 0ver 60+ knots on a vessel that are close to 50 meter long

If we look on hp-per-tons:
- skjold class, 58,76 hp/tons
- PR. 1168PL, 37,89 hp/tons

so if we say to manage to get to 50 knots, she should have around 44 hp/tons, if we look at the difference between skjold class and PR. 1168PL. That give us 41800 hp. it's just an estimate, since I do not know how much power a SWATH hull need when it travel over a certain speed, Some ships you need to double the hp just to increase speed beyond a line.

for me, 40-45 knots is more realistic.

Thanks everyone for the feedback!
I couldn't dream of a more fitting compliment.
This was exactly the feeling I wanted to evoke with this design, as well as a fair bit of this thread. Ship design is always hit-and-miss, but the Soviets have historically pursued a lot of contradictory research avenues at the same time, and pushed them to more concrete realizations than most other countries.
Maybe it's just me, but I find this kind of experimental one-offs harder to work on than in-service ships, even when completely fictional. I tend to err on the side of caution for new designs, and spend so much time tinkering with the drawings to make them plausible that I'm sometimes at a loss as to where to stop optimizing a ship that never saw service, and what exactly can be considered experimental. Hah! I knew you wouldn't resist commenting on a Skjold-like design!
Still a good point, and well argued at that. But before diving into calculations, I would like you to check the B-sides and tell me if you also read 2x2x18000hp for both classes? I haven't edited this in the meantime, honest. You can check the date tag on the Dropbox page if you want.
That gives the Pr.1168PL at full load a p/w ratio of 75,79hp/ton (predictably double what you calculated), which is all the more honorable considering the Pr.1239 rates at 60,94hp/ton, pretty close to the Skjold.
Also keep in mind that, at least for Soviet ships (again based on the Bora), top speed is not supposed to be reached at full load. A realistic, operational full speed for the Pr.1168 would, indeed, be slightly over 40kt, hence the given cruise speed of 35kt (let's say with full lifting power and half on the propulsion, i.e. 56,84hp/ton).

I honestly haven't given that much thought to the internal layout of the Pr.1168, given how much it owes to its IRL predecessor. Also I haven't used the Skjold as reference, rather extrapolating from the Pr.1239 (Bora) to reduce the influence of different local design habits and idiosyncrasies (materials, safety margins, inefficiencies, habitability...).
The next class I'll post on the other hand, is fully original, more modern and was given a much more thorough examination, so there will be more for you to pick apart...

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Soviet Century/Cold War 2020 Alternate Universe: Soviet and other Cold War designs 1990-2020.
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