US Navy CONFORM submarine

[Triton]

Images of a model from the US Navy concept formulation (CONFORM) submarine project from the late 1960s. CONFORM was a possible follow-on to the Permit (SSN 594) and Sturgeon (SSN 637) classes devised by Naval Sea Systems Command (NavSea) circa 1967-68. By November 1968, the initial CONFORM studies had produced 36 design concepts, examining such alternative features as twin reactors, single turbines, contra-rotating propellers, deep-depth capability, and larger diameter torpedo tubes.

One CONFORM concept was to use a derivative of the S5G Natural Circulation Reactor (NCR) plant that Vice Admiral Hyman G Rickover was developing for the one-of-a-kind Narwhal (SSN 671). The NCR uses the natural convection of the heat exchange fluids (coolants) at lower speeds rather than circulating pumps, a major noise source of propulsion machinery in nuclear submarines.

The S5G was estimated to be capable of providing a submerged speed of more than 30 knots with a CONFORM submarine hull approximately the same size as Sturgeon, about 4,800 tons submerged. 20,000 shaft horsepower would power a counter-rotating propeller.

One of the most innovative features of the pictured CONFORM design was its periscopes and masts that folded down flush onto the hull rather than retracting vertically into the hull. This feature would have reduced pressure hull penetrations, provided more flexibility in internal arrangement, and possibly alleviated the need for a sail. A small bridge structure could be raised and then folded down flush onto the hull.

The "front end" of the CONFORM was to be greatly improved, with an increased number of weapons, advanced sonar, and a high degree of automation.

According to Polmar, the CONFORM project was "scuttled" by Vice Admiral Hyman G Rickover in favor of the Los Angeles class.

Source: Cold War Submarines: the Design and Construction of U.S. and Soviet Submarines
by Norman Polmar and Kenneth J. Moore, Brassy's, Inc., 2004.

 

[JohnR]

I would image that developing the periscope with a hinge and "conventional" optics would be a challenge, also raising the periscope against water pressure if the submarine is going ahead would be interesting.

The concept would propably more workable with current technology non penetrating designs?

 

[Longshaor]

It is an interesting design that, in some ways, was more andvanced than the Los Angeles (SSN 688) class boats that succeeded it. The incorporation of HY-130 steel, for example, which would have allowed for deeper diving for a given pressure hull thickness, was never (at least as of the Seawolf (SSN 21) class) used.

Rickover & McNamara certainly seemed not to care for eachother, and Rickover clearly did everything in his power to kill ConForm, though to be fair, his Naval Reactors Division was apparently very close to being over streched (working on the S5G reactor for Narwhal (SSN 671), submarine versions of both the D1G and D1W destroyer reactors, and what would become the A4W carrier reactor). By refusing to allocate resources to further development (reducing the size whle increasing the power output) of the S5G, he fatally undermined the ConForm project, though it took the incoming Nixon administation & a new SecDef to end the program.

Given that ConForm was an OSD (Office of the Secretary of Defense) formulated project, I'm wondering if detail design of things like the periscope hinges were ever done.

- Source: US Submarines Since 1945: An Illustrated Design History by Norman Friedman (Chapter 10: Los Angeles and Her Successor)

 

[GTX]

Interesting - I've often wondered why there have not been more recent proposals with minimalist sails.

Regards,

Greg

 

[Triton]

According to Polmar, the CONFORM hull design and use of HY-100 steel could provide a test depth as great as 2,000 feet (610 m).

Looking for cuts in new military programs to help finance the Vietnam War, the Navy had to justify why it had three new submarine programs: Turbine Electric Drive Submarine (TEDS)/USS Glenard P Lipscomb, CONFORM, and DIG (SSN 688) in 1968.

Friedman makes the case that Rickover believed that there was a pressing need to counter the new fast Soviet SSNs that could attack aircraft carriers with nuclear-tipped torpedoes off the carrier's bow. It was believed that the Permit (SSN 594) and Sturgeon (SSN 637) classes were too slow to intercept and destroy these boats. Of the choices available, in Rickover's view, the DIG reactor powered submarine (SSN 688) was the best choice because it was ready for production. Rickover didn't want to wait for the final CONFORM submarine design or wait for a contest between the DIG reactor powered submarine prototype and the CONFORM prototype to determine which one the US Navy should purchase. Rickover stated that he would refuse to approve the S5G in a CONFORM hull under his authority in the civilian Atomic Energy Commission, thus scuttling the CONFORM project.

 

[Longshaor]

According to Friedman, the hull for ConForm was intended to be HY-130 with HY-100 as a fall-back if the former wasn't ready in time.

The Glenard P Lipscomb was a great example of the ongoing turf war between McNamara's people & Rickover. Where most military officers could not oppose McNamara because of his position as SecDef, Rickover as an AEC employee could use his Congressional contacts and support - as well as the office of the AEC - to undermine McNamara. To that end,he forced through the construction of a one-off experimental sub that would never see series production (which is why McNamara tried to kill it) as a sound test bed. The idea was that if the gear whine inherent in all other USN nuclear subs was removed, the designers would have a "clean" boat to test for other sources of radiated noise. The net result was a quiet, if very slow, boat. The DC direct-drive system, known as TEDS, was much larger than originally envisaged, and in service it proved both ineffecient and unreliable.

The interesting upshot of this battle was that

The TEDS fight did make OSD more wary of attacking Admiral Rickover; as a result, TEDS deeply influenced later decision in favor of Los Angeles.

-Friedman, US Submarines Since 1945, pg. 149.

 

[Graham1973]

Interesting project. Has anyone found more information?

 

[Grey Havoc]

This type propulsor found practical application on the USS JACK, of the THRESHER class. However, they never did work out a reliable shaft-seal system and the boat had to live with a constant flow of leaking water around the shafts. The Navy never revisited the concentric, counter-rotating propulsor again (other than paper studies – hello, ConForm!).

 

[Cjc]

So I think I'm confused about some parts, how would conform have compared to ssn-886?

 

[TomS]

So I think I'm confused about some parts, how would conform have compared to ssn-886?

It's a little tricky because CONFORM was never a single point design but rather a series of study concepts. The one most people are talking about was a design with similar speed to the 688 (Los Angeles). This design would have been smaller, with about 2/3 the power (20k shp vs 30k shp for the LA) and displacement (~4800 tons vs 6900 tons). It would also have been deeper diving and might have had larger torpedo rooms. It also would have had a much smaller crew compared to standard US submarine practice.

All of this assumed that:

1) HY-100 (or ideally HY-130) steel could be welded efficiently at scale (HY-100 couldn't until Seawolf and Virginia. HY-130 still isn't.)

2) The S5G Natural Circulation Reactor could be developed from 17000 to 20000 shp (possible but not a given)

3) contrarotating props could be made to work (uncertain)

4) automation would have been successful to reduce crew size (Rickover would never have allowed it)

 

[TomS]

A thought that occurred to me last night. Although CONFORM might have had larger torpedo rooms than the LA class, presumably by eliminating some accomodation space, it would have likely been a tighter overall design and might not have had room for the Tomahawk VLS that went into the 688 Flight II and III boats.

 

[Yellow Palace]

It almost certainly wouldn't, I think. In some ways it feels like it was meant as a 'submariner's submarine', in the same sense as the F-15 was a 'fighter pilot's fighter'. Advanced technology that made it better at its job was good. Anything that distracted from that one job was unwelcome. And cruise missiles, if they were contemplated at all, weren't a requirement for an attack submarine.

 

[Winchester]

OK, so some explanation is required. All of this is paraphrased from Friedman's US Submarines since 1945.

"CONFORM" stands for "Concept Formulation", and was part of the reforms that Robert McNamara crammed down the throats of the defense establishment in order to save money from procurement of advanced and "unnecessary" weapons, so he could fight the Vietnam war.

The effect of the reforms, as applied to naval shipbuilding, was to effectively start over development of several US Navy programs - aside from the 637-successor, the Littoral Fire Support ship and the DX program were also affected.

Under the reforms, the first stage of military procurement was "find out what you actually need", according to McNamara's procedures. The problem for the 637 successor in particular was that Rickover's outfit was already halfway done designing the 637 successor when McNamara forced the navy to start over, and Rickover had to agree in writing to do whatever CONFORM recommended.

Rickover's design, a submarine based on a stretched 637 with a D1G-based reactor for additional speed, was shuffled into bureaucratic hell while OPNAV spent their time seriously considering building submarines out of effectively hypothetical materials (HY-130) using hypothetical technologies (folding masts were just the start) that would require serious development time to even start on, as if they would be ready by 1974. And all the while, fast Soviet nuclear attack subs were multiplying, and the in production Sturgeon (637-class) could not catch them.

By 1966, HY-130 and HY-100 had both been dropped from consideration and the principal options for requirements were:

S5W, boosted S5G, or D1G for the power plant, using contra-rotating propellers
2, 4 or 8 torpedo tubes, with 11, 22, or 44 weapons.
Skipjack, Thresher, or 2,000 feet test depth
Thresher or Sturgeon-sized sail

The boat would be built from HY-80 steel.

Also, to save costs, the subs were envisioned to be as small as possible.

Rickover had other ideas, and had started working on submarinizing the D1W reactor, which would boost speed by 5 knots on top of the D1G, at the cost of a bigger but also more capable sub. At the same time, the D1W was also being developed into what would become the A4W for the CVN-68 class. Things went back and forth for a bit there, and at one point the CONFORM study was pointing towards a 305 x 33 ft, 4,500 ton submarine.

And then in February 1968, a Soviet Navy November-class submarine intercepted the Enterprise carrier group en route to Vietnam, and the Soviets unveiled the Victor and Charlie class submarines. Rickover apparently used a bunch of his pull in Congress to point out that the CONFORM proposals, as well as the existing subs, were just too slow to keep up with the Soviets and managed to get the D1G-based submarine reactor, as well as the 688 it would be housed in, approved and ordered.

But CONFORM wasn't done yet, and the 688-class was just ordered as an interim design at first, while the "true" successor was designed. Meanwhile Rickover's congressional allies made sure that the 688 program received multiple orders per year, and by 1969 the CONFORM program was abandoned because the Navy was already buying what looked to be a competent successor to the 637, procedures be damned.

Meanwhile, since the 688s were based closely on the Sturgeons and were considered "old tech", the Navy went back to trying to figure out the *next* submarine class, starting from a clean sheet of paper with concepts floated such as 25-inch torpedo tubes to launch bigger torpedoes and cruise missiles; vertically launched cruise missile tubes; a 40 ft diameter hull to stick an even bigger reactor into, etc. This became known as "APHNAS", and was effectively a cruise missile sub with 20 tubes for a very large missile called STAM, which came in cruise missile, ASW, and anti-ship versions under the designation UGM-89 Perseus. Among the concepts explored here was eight torpedo tubes, HY-100 steel construction, 40 foot diameter hull, conformal lateral sonar arrays, and bow-mounted sailplanes. If any of those ring a bell... yeah, Seawolf had a long, long history.

Elmo Zumwalt, proponent of "cheap and plentiful rather than expensive and irreplaceable", basically decide that 1 - none of this tech was ready, and 2 - each one of these would cost him more than one Los Angeles-class boat, and he needed the boats at sea, and cancelled APHNAS and sent the missile people back to the drawing board with orders to "make it fit a 21-inch tube and we'll talk".

The results of that latter order were the Tomahawk and Sea Lance programs.

 

[TomS]

The other interesting sub in this the next concept, circa 1980 to develop a low-mix nuclear sub called the Fleet Attack (FA). This would be be cheaper and slower than the LA class, leaving the carrier escort mission to the LA class (the need to pace a.CVN is one factor that drove the speed of the 688s). FA would have been a "short, fat" submarine for better hydrodynamics, leading to the nickname Fat Albert. IIRC, FA would possibly have had a larger torpedo room (thanks to the increased diameter) for more combat persistence.

 

[Winchester]

The other interesting sub in this the next concept, circa 1980 to develop a low-mix nuclear sub called the Fleet Attack (FA). This would be be cheaper and slower than the LA class, leaving the carrier escort mission to the LA class (the need to pace a.CVN is one factor that drove the speed of the 688s). FA would have been a "short, fat" submarine for better hydrodynamics, leading to the nickname Fat Albert. IIRC, FA would possibly have had a larger torpedo room (thanks to the increased diameter) for more combat persistence.

There were more interesting subs in between - it's amazing how many times "40 foot hull diameter with eight torpedo tubes and a D1W-based reactor" came up during the late 60s and the entire seventies.

Friedman has stats for the F/A as of early 1981 - 15,100 SHP, 237.5f feet length, 38 ft diameter, 4,965 tons submerged displacement, 6 tubes/32 weapons, and fairwater dive planes. Speed was "3 knots faster than Sturgeon" due to a more efficient hullform and propeller design.

The Submarine Force preferred the more multipurpose "SSNX", which had 38,700 SHP, was 301.25 feet long, 38,75 feet in diameter, displaced 7,263 tons, and had 6 torpedo tubes with 32 weapons, and 12 to 24 VLS cells and bow dive planes.

The decision for which sub to go with was deferred until December 1980, then Carter lost the election and Reagan went "build whatever we're already building" and the Los Angeles successor ended up deferred all the way to FY 89.

 

[TomS]

Thanks. I need to get hold of Friedman's postwar sub book. Polmar kinda skims over FA (he calls it FAS) and skips straight to SSN-21.

 

[Scott Kenny]

Interesting - I've often wondered why there have not been more recent proposals with minimalist sails.

Regards,

Greg

Old question, but the primary reason is that until the Virginia class sorted out fiber optics masts, having any height to your periscopes required a tall sail to support the height above the control room.

Let's use some guesstimates from the Ohio class:
Hull is 42ft in diameter.
The control room is on the Upper Level, about 35ft above the keel. That determines how far up the periscope can go above the top of the support structures. A periscope is a single instrument, kinda like a reflector telescope that has a very small mirror, they don't bend or telescope into a shorter package.

Top of the turtleback is about 15ft above the hull, so if an Ohio class didn't have a sail, the periscope could maybe stick 35 feet above the top of the turtleback, assuming that the periscope itself could survive having 20 feet of length unsupported by a fairing.

There's also some hydrodynamic reasons, but the primary is the need to house the periscopes and the rests of the masts and antennas.

 

[A Tentative Fleet Plan]

Friedman's US Submarines since 1945 mentions that the CONFORM SSN was supposed to have the Raytheon S70 integrated sonar system from FY70 onwards. Would this have used existing sonar arrays connected to new processing equipment, or would it have been an entirely new system?