Obscure USN Frigate concepts and studies

[Tzoli]

Interesting that the dimensions were stated in between perpendiculars while modern ships mostly states overall length more often then waterline.

Also one source states Goalkeeper CIWS while other drawings shows Phalanx

LBP seems to be preferred by naval architects. Not sure why exactly.

Which design are you looking at specifically that has the Goalkeeper/Phalanx mismatch?

The NATO Frigates. Your scans show Phalanx, "that_person" 's drawing and description tells Goalkeeper or implies the Dutch Goalkeeper

 

[Yellow Palace]

So, displacement starts at 5183 tons for basically duplicating FFG-61 (~4100 tons) with reset service life margins, a second shaft and auxiliary diesel engines, a steel and composite superstructure with some stealth shaping, and updated armament.

That's quite interesting, because it basically bears the same relation to FFG-7 as CGBL does to CG-47. A baseline design for a modern USN frigate, as it were. The evolved Aegis Combat System version isn't quite an F100, but you can see a lot of similarity there. Only so many ways to design a modern frigate, after all.

LBP seems to be preferred by naval architects. Not sure why exactly.

Between perpendiculars is a more useful measurement for most engineering purposes, because it excludes the long but insubstantial bow and stern forms and gives a more representative measure of the useful length of the ship. Overall length can easily be thrown off by the addition of a strongly raked stem, or a cruiser stern in place of a transom stern. Waterline length isn't much use, because it changes with loading condition.

Incidentally, be very wary of draught figures reported for warships. Not only do they vary with loading condition, but public domain sources are inconsistent about using navigational draught (including projections below the baseline) or moulded draught (to the inside of the shell plating). Moulded draught is the figure used for design. Navigational draught includes things like the tips of propellers and sonar domes, which add no significant displacement.

 

[Tzoli]

Actually...
BPP changes with load as well as it's messured at the waterline at the front and the rudder axis at the aft

 

[TomS]

The NATO Frigates. Your scans show Phalanx, "that_person" 's drawing and description tells Goalkeeper or implies the Dutch Goslkeeper

OK, I see the confusion. The drawing captioned "A NAVSEA sketch of the NATO frigate" in Friedman (posted by that_person) isn't one of the slides I've posted. It's NFR-90, which is well known and has it's own thread here already. The Friedman caption suggests he had another source for this drawing, as it mentions details not in the slide deck I'm working from.

Edit: I'm not planning to post the NFR-90 slide, because it doesn't add anything new to the knowledge of that program that we've already documented elsewhere.

 

[TomS]

Between perpendiculars is a more useful measurement for most engineering purposes, because it excludes the long but insubstantial bow and stern forms and gives a more representative measure of the useful length of the ship.

Ah, that makes sense. So, for example, the flight deck extension added to the FFG-7s doesn't change LBP because it is basically a reverse-raked transom that adds very little volume.

 

[Yellow Palace]

Actually...
BPP changes with load as well as it's messured at the waterline at the front and the rudder axis at the aft

You'd think I'd remember that, but apparently not. It is, specifically, referred to the waterline at the design draught - draught with the ship in all respects complete, fully loaded, with full complement, stores, fuel, water and payload, plus any specified margins.

Using the intersection of the stem and the waterline does make more sense, plenty of ships don't have a well defined forefoot.

 

[Winchester]

So, as it happens, those export studies were next up. (PXM turns out to be a rabbit hole -- Friedman and this brief only referenced one of about a dozen configurations that were done under PXM around 1985-86, with multiple different hull technologies and equipment standards. That's probably going to be a separate thread at some point, when I get to the bottom of it.)

The FMS export frigate studies were done by Gibbs & Cox for a Royal Saudi Naval Force (RSNF) frigate requirement that was eventually fulfilled by the Al Riyadh class (a Lafayette AAW variant). Combat Fleets 1995 reports that the Saudis were looking specifically at the AEGIS version. As of September 1992 other candidates being considered were a modified Halifax-class frigate with Sea Sparrow, or FF-21. Which certainly covers the full range of capability, consistent with Saudi's usual acquisition strategy.

So, the interesting thing is that there are three versions that differ only in their radar and weapon control systems -- FFG-61 CORT, New Threat Upgrade (NTU), and the AEGIS Combat System (ACS). The actual armament was fixed across the three baselines: 32 Mk 41 VLS, 8 Harpoon, 1 Mk 45 gun, 2 CIWS, Mk 32 torpedo tubes, and 2 LAMPS III size helos. Same for the EW suite, which was SLQ-32(V)5 with Sidekick and the usual SRBOC launchers plus Nixie. ASW seems to be limited to the hull sonar (SQS-56, despite the typo across all three slides) and LAMPS III helos, with no mention of towed array or VDS.

So, displacement starts at 5183 tons for basically duplicating FFG-61 (~4100 tons) with reset service life margins, a second shaft and auxiliary diesel engines, a steel and composite superstructure with some stealth shaping, and updated armament.

Swap out the FFG-61 combat system for a version of NTU and the displacement jumps up to 5640 tons. And you add about 20 crewmembers.

Jump to ACS with ANPAR (SPY-1F) and displacement rises again, to 5723 tons. (Something weird happens with beam here; the heavier ACS version manages to be narrower than the NTU version, despite being longer and appearing to have more weight high. Not sure how that happened, but stability calcs can be weird. Or it could be another typo.)

(Images snipped)

I should have looked at this thread earlier this evening before I sat down and made an incorrect version of the bridge for this frigate in 3D... the drawing of the RSNF frigate in Friedman appears to be a tracing over the 3D concept art, and omits the crease between the forward face and the diagonal faces at the front of the superstructure. Thanks for posting it though, now I can go make new deckhouses.

Oh, and regarding PXM - when I look at the Saudi Badr-class corvette and compare it to the Variant 4 Monohull version that's depicted in US Destroyers, I get the distinct impression that the Badr-class is effectively the Variant 2 Monohull version of PXM - same combat system (Mk92), with the same armament (76 mm, Phalanx, 8 harpoons, 2 triple SVTTs), and the same propulsion (I think?)

The dimensions may be just a tiny bit different, but I'm willing to chalk that up to detail design vs proposal design.

Edit:

Stat/Ship	Badr-class	Variant 2 Monohull
Displacement	1038 t	950 t
Length	245 ft	262.4 (wl), 275 (oa)
Beam	31 ft 6 in	29 ft 6 in (wl), 36 ft 6 in (oa)
Draught:	8 ft 9 in	19 ft (sic)
Gas turbines	1 GE LM-2500	2 GE LM-2500
Diesels	2 MTU 12V652 TB91	2 x 3,700 hp
Speed:	30 knots	not given
Complement	75	35

Hmm. The stats ended up pretty different after all...

 

[TomS]

Oh, and regarding PXM - when I look at the Saudi Badr-class corvette and compare it to the Variant 4 Monohull version that's depicted in US Destroyers, I get the distinct impression that the Badr-class is effectively the Variant 2 Monohull version of PXM - same combat system (Mk92), with the same armament (76 mm, Phalanx, 8 harpoons, 2 triple SVTTs), and the same propulsion (I think?)

It's certainly possible. PXM seems to have gone through some different iterations, with armament including a very early version of RAM and Hellfire. Also considered were helicopter dipping sonars, lightweight VDS, etc. And there were both hydrofoil and surface effect versions in multiple sizes.

As I said, a rabbit hole.

 

[that_person]

Hey @TomS, quick question for you. In this post ( https://www.secretprojects.co.uk/threads/obscure-usn-frigate-concepts-and-studies.39022/post-522529 ) you were talking about the PXM studies. Your wording there has me interpreting that you have more info on the PXM studies. Is this by any chance true? I’m very curious to dive a bit deeper into this.

 

[TomS]

Hey @TomS, quick question for you. In this post ( https://www.secretprojects.co.uk/threads/obscure-usn-frigate-concepts-and-studies.39022/post-522529 ) you were talking about the PXM studies. Your wording there has me interpreting that you have more info on the PXM studies. Is this by any chance true? I’m very curious to dive a bit deeper into this.

Bits and pieces, but I'm still trying to organize it into a coherent story. Maybe after New Year.

 

[that_person]

Hey @TomS, quick question for you. In this post ( https://www.secretprojects.co.uk/threads/obscure-usn-frigate-concepts-and-studies.39022/post-522529 ) you were talking about the PXM studies. Your wording there has me interpreting that you have more info on the PXM studies. Is this by any chance true? I’m very curious to dive a bit deeper into this.

Bits and pieces, but I'm still trying to organize it into a coherent story. Maybe after New Year.

Sorry to bother you, but can I ask about the status of your PXM write-up? I'm hoping to make a 3D model out of Friedman's drawing, but I want to have more context to the project first, so that I know what I'm doing.

I've tried searching the internet a bit, but the only notable info I've come across is they wanted 12 hulls, with construction starting in 1990, and for the ships to be built in European yards.

 

[TomS]

Hey @TomS, quick question for you. In this post ( https://www.secretprojects.co.uk/threads/obscure-usn-frigate-concepts-and-studies.39022/post-522529 ) you were talking about the PXM studies. Your wording there has me interpreting that you have more info on the PXM studies. Is this by any chance true? I’m very curious to dive a bit deeper into this.

Bits and pieces, but I'm still trying to organize it into a coherent story. Maybe after New Year.

Sorry to bother you, but can I ask about the status of your PXM write-up? I'm hoping to make a 3D model out of Friedman's drawing, but I want to have more context to the project first, so that I know what I'm doing.

I've tried searching the internet a bit, but the only notable info I've come across is they wanted 12 hulls, with construction starting in 1990, and for the ships to be built in European yards.

It's not high on my list right now.

However, I think the bit you mention about building in foreign yards might actually be discussing the later PC instead -- that was developed specifically using in-production hulls from foreign builders (though the actual construction work was done in the US).

PXM started as a jobs project proposed by Boeing, basically a continuation/expansion of the PHM. But then it became a research effort to compare various "Advanced Marine Vehicle" configurations so you saw baselines PXMs with the same systems on monohulls, hydrofoils, and surface effect ship.

 

[JohnCitizen]

It really didn't. There's no evolutionary connection from this idea to LCS, as far as I'm aware.

The connection isn't between the specific designs--the hulls, etc--but between the concepts. The idea of lower intensity warfare. The thing is, if one suddenly found oneself fighting a peer or near peer, the CALOW could still be of use, while the LCS was/is just utter garbage.

 

[JohnCitizen]

It really didn't. There's no evolutionary connection from this idea to LCS, as far as I'm aware.

The connection isn't between the specific designs--the hulls, etc--but between the concepts. The idea of lower intensity warfare. The thing is, if one suddenly found oneself fighting a peer or near peer, the CALOW could still be of use, while the LCS was/is just utter garbage.

Second design, a Mobilization Frigate. This is a very austere ship designed to show what could be done to build an ASW escort very quickly without a sophisticated combat system or other equipment. Precise timeframe is unclear, but I'd guess mid-to-late 1980s (maybe just before the fall of the Soviet Union).

The choice of diesel-electric propulsion is unsurprising in a design that was explicitly calling back to WW2 DE concepts. The HP listed lines up very closely with contemporary diesel-electric locomotive plants; I would not be surprised if that was intentional, so they could use existing production lines for those engines.

Nothing shocking in terms of combat systems (other than how basic it all is). "SY-2" should be SYS-2, a track manager/integrator. Sea Sparrow isn't obvious in the drawing, but I'd guess it would be some form of Mk 48 VLS or possibly even an old NSSM launcher. Basically everything on this ship could have been recycled or procured very quickly from existing production lines.

Whoever drew this had limited graphics resources; note the Mk 45 gun mount scaled down in lieu of an actual Mk 75 76mm gun, for example. There are no antennas shown, but the SPS-49 would presumably have gone on the lower platform with SPS-55 at the masthead. Phalanx likely at the aft end of the hangar roof (a la FFG-7) with the Sea Sparrow somewhere forward of that, either at the front of the hangar roof if NSSM or in the break between the hangar and bridge superstructure if VLS.


View attachment 675266View attachment 675268

Not sure if anyone is monitoring this forum anymore as its now Jan 2024, but this is fascinating. Just stumbled upon it. Question: while this MOBFF was not "high end" even for the 1990s, couldn't its systems have been qualitatively upscaled? As long as not too heavy and there would be reliable power for more intense electronics?