Sixty years ago, Soviet engineers began developing a new submarine under strict orders to eschew previous design decisions in favor of innovative concepts wherever possible. The resulting boat, a guided missile submarine that was known first as K-162 and eventually as K-222, established a still-unbeaten underwater speed record and was the first titanium-hulled submarine ever, but also proved too expensive and complicated to be anything more than a one-off, earning the nickname "Golden Fish."
K-162/K-222, the only Project 661 submarine ever built, was the product of a direct order from the Central Committee of the Communist Party of the Soviet Union and country’s Council of Ministers on Aug. 28, 1958. The directive called for a new “high-speed submarine” and development began the following year. The Project 661 design was also known as the Anchar-class in the Soviet Union and NATO referred to it as the Papa-class, even though there was only ever one boat.
The immediate impetus for the development of the Project 661 design was the limited capabilities and poor performance of the first generation of Soviet diesel-electric guided missile submarines, or SSGs. These early boats were conversions of Whiskey-class submarines, which were themselves derived from World War II-era Nazi U-boat designs.
When work on the Project 661 submarine started, the Soviets had already separately begun development of new classes of purpose-built conventionally-powered guided missile submarines (SSGs) and nuclear-powered guided missile submarines (SSGNs), the Project 651s and Project 659s respectively, which were also known as the Juliett- and Echo-classes in the West. But the goal for the new project was to produce an entirely novel cruise missile-carrying submarine that would be even more capable than either of these interim designs.
The first major decision the designers made was to use titanium alloys for the submarine’s external and internal hulls rather than steel or aluminum. Titanium offered benefits in terms of its general strength and resistance to corrosion.
Though titanium is also only weakly magnetic, this did not render the Project 661 immune to detection by aircraft with magnetic anomaly detectors (MAD) or magnetic mines. This is due to the presence of more magnetic metals in the alloy, as well as various other components inside the submarine itself.
Compared to earlier Soviet submarines that still showed the influence of World War II-era designs, the hullform of the Project 661 was significantly different, featuring a rounded bow and a streamlined “split-feed” stern with twin propellers. The 1970s-era Project 949 SSGNs, or Oscar-class, would also use this same general arrangement.
The Soviets had never had to build such large titanium alloy components. So, while fabrication of the first components for the Project 661 submarine began in 1962, the need to devise entirely new and complex manufacturing processes meant the submarine was not officially laid down until December 1963. Years later, during construction of the titanium alloy hulled Project 705 submarines, also known variously as the Lira-class or Alfa-class, workers reportedly had to craft the hull sections inside a shed filled with inert argon gas, requiring the use of cumbersome "moon suits" with their own air supply.
For the Project 661 submarine, the Soviets also developed an advanced nuclear pressure water reactor, as well as a prototype lead-bismuth eutectic (LBE) cooled design. LBE reactors have greater thermal efficiency and can operate at higher temperatures than water-cooled designs without risk of the coolant boiling off.
Unlike other liquid metal-cooled reactor types, such as sodium or sodium-potassium designs, LBE does not react spontaneously with air or water, reducing the size and complexity of the entire coolant system and eliminating the risk of an explosion in the event of a leak. Unfortunately, LBE is also much more corrosive and has a higher melting point.
This means this type of reactor typically has a shorter overall lifespan and there is a risk of the coolant solidifying if the reactor drops below a certain temperature, requiring significant power to keep it sufficiently warm at all times. Furthermore, as the coolant becomes irradiated over time, it forms highly radioactive polonium-210 – a substance dangerous enough to work as an assassination weapon – as a byproduct, making it especially hazardous to refuel the system or otherwise handle any contaminated components.
The Soviets ultimately opted to install two highly compact VM-5 pressure water reactors, despite their lower performance. Even so, each one of them produced up to 177 megawatts of power. By comparison, the Echo-class SSGNs had a single, earlier VM-A that only generated a maximum of 70 megawatts.
The immense power from these reactors, combined with its lightweight, but strong titanium hulls, helped give the submarine a relatively blistering speed underwater. The Project 661 boat could cruise submerged at just shy of 44 miles per hour. It broke the world speed record for a submarine traveling undersea during its sea trials, reaching a maximum speed of more than 51 miles per hour.
The U.S. Navy’s Los Angeles-class nuclear-powered attack submarines, improved variants of which remain service today, have an official top speed of 23 miles per hour when submerged. There have been reports that these boats can actually get up to around 35 miles per hour underwater. The latest American Virginia-class attack submarines have a publicly stated top submerged speed of around 29 miles per hour, but this is still significantly slower than the Project 661 design.
The Soviet-era film below, though in Russian only, still offers an interesting look at K-162/K-222, its development, and the submarine in action.
The main armament of the Project 661 submarine was 10 anti-ship cruise missiles. At the time construction of K-162 began, the Soviets did not have a weapon of this type that a submarine could fire while concealed underwater. Existing SSGs and SSGNs had to surface first, making them vulnerable during the firing sequence.
So, they initiated the development of a new missile in parallel, which resulted in the P-70 Ametist, also known as the SS-N-7 Starbright. This weapon had a range of more than 35 miles and could carry a high explosive or nuclear warhead.
With these missiles and its extreme speed, the Soviets expected to use the Project 661 boats to intercept American carrier groups. Since the submarines could not reload their missile tubes, slotted into tubes between inner and outer hulls, at sea, they would have had to return to port to rearm. The design also had four torpedo tubes and room for a dozen torpedoes, primarily for self-defense.
Unfortunately, the benefits of the Project 661’s design came at the price of extremely high cost and complexity. It took the Soviets almost six years from when they laid down K-162 in 1963 to get her commissioned.
While the first Project 661 was under construction, the Soviets were also able to design the simpler steel-hulled, single-shaft Project 670 SSGN, or Charlie-class, lay down the first example in 1964, and have it commissioned in 1967. The Soviet Navy had commissioned five of these submarines before K-162 even entered service.
The Soviets ultimately decided not to produce any additional Project 661 submarines. But despite being the only ship of her class, K-162 did enter operational service. However, she proved to be just as problematic at sea as she was to build. Her high speed exposed problems that other submarines have never experienced.
At speeds over 40 miles per hour, turbulence along the hull created excessive noise, reportedly up to 100 decibels in some cases, louder than a truck driving by you, in certain places. For submarines, silence is key to survival. At its top speed, K-162 would also begin to suffer actual external damage from the force exerted on the hull.
So, after joining the Soviet Union’s Northern Fleet in 1971, K-162 made relatively few operational patrols. For unspecified reasons, in 1978, the Soviets changed her hull number to K-222.
It wasn’t until September 1981 that a U.S. Navy carrier-based anti-submarine warfare squadron even spotted the submarine during a cruise. The S-3 Vikings of now-inactivated Sea Control Squadron Three Zero (VS-30), the Diamondcutters, flying from the deck of USS Forrestal at the time, hold that honor.
Given the Soviet’s own concerns about her acoustic signature, it seems unlikely that this was entirely a product of her going undetected for a decade. In July 1981, P-3 Orions of Patrol Squadron One Zero (VP-10), flying from Naval Air Station Keflavik in Iceland had also detected the submarine after it sailed into an area where NATO naval forces were conducting an exercise. This earned that unit a Meritorious Unit Commendation from the Secretary of the Navy.
The lone Project 661 submarine saw the most action on the pages of Tom Clancey's 1986 novel Red Storm Rising. The boat briefly appears in the book to conduct anti-convoy operations.
The submarine’s biggest contribution appears to have been laying the groundwork for subsequent titanium-hulled nuclear-powered Soviet attack submarines, primarily the aforementioned Project 705 and the Project 945, or Sierra-class. The Alfas also used LBE-cooled reactors derived from the design originally intended for the Project 661.
The Alfa class boats were also capable of extremely high speeds, topping out around 47 miles per hour. But, while they were more successful than the sole Papa-class boat, they suffered from many of the same limitations, which you can read about in more detail here. They spent most of their time in port, poised to dart into the North Atlantic during a crisis.
K-222 was gone from the active rolls of the Northern Fleet before the collapse of the Soviet Union. In 1999, she was formally stricken and set to get scrapped.
In a final testament to her effectively experimental design, in 2010, the Zvezdochka Ship Repair Center, part of Russian shipbuilder Sevmash in Severodvinsk, began dismantling the submarine without removing her reactor or its reactive fuel first. At the time, the Russians were still in the midst of a selecting a consultant, via the European Bank for Reconstruction and Development (EBRD), to determine the best way of disposing of the boat’s radioactive components.
The Kremlin reportedly went ahead with breaking down K-222 before worrying about what to do with the reactor or its fuel because the submarine’s design did not have any specific provisions for removing the reactor for servicing or other purposes, to begin with. It’s not clear what happened to either the reactor plant or any other components of the boat in the end.
After more than six decades, the Project 661 design still holds the world record for the top submerged speed of any submarine. The boat was certainly an impressive feat of engineering, but given the problems it exposed with sailing this fast under the water, it seems unlikely that this record will get broken any time soon.
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