A Speedy Submarine Comes at a Cost: They are Terribly Noisy
The Navy could hear an Alfa-Class submarine coming, but could it outrun one?
Key point: The Alfa represented a design paradigm for “small but fast” attack submarines that would ultimately fall out of favor compared to “big but stealthy” designs; though isolated media reports have revealed some interest in future Alfa-like boats. Yet stealth, not speed, reigns as king in modern submarine warfare tactics.
The Project 705 Lira—better known abroad as the Alfa-class submarine by NATO—was basically a submarine race car, and looked the part with svelte tear-drop shaped hull, rakishly trimmed-down sail designed to minimize aquadynamic drag, and even its convertible-style pop-up windshield.
Military vehicles are generally designed out of a relentless quest for efficiency, but the Alfa’s iconic shape exemplifies how kinematically optimal designs often possess a striking aesthetic of their own.
This first appeared earlier and is being reposted due to reader interest.
Soviet nuclear-powered attack submarines tended to be faster and deeper-diving than their Western counterparts—though they were also noisier and more prone to horrifying accidents.
The Project 705, however, originated as a 1958-design concept to push the speed advantage to the maximum, allowing the submarine not only keep pace with but overtake NATO carrier task forces typically cruising at 33 knots—while keeping one-step ahead of enemy torpedoes and out-maneuvering enemy submarines.
This extraordinary performance would be achieved by ruthlessly maximizing speed and subtracting from weight. Thus the Alfa featured a relatively small hull made of titanium alloy. Titanium is a rare metal which can create surfaces as strong as steel for roughly half the weight. It is also paramagnetic, making the submarine’s hull more difficult to detect for maritime patrol planes using Magnetic Anomaly Detectors.
However, titanium can only be welded in an inert argon or helium atmosphere. This led U.S. engineers to assume it was simply impractical to weld large pieces of titanium on the scale necessary for a submarine hull. They underestimated Soviet determination: workers in pressurized suits would work in huge warehouses flooded with argon gas to assemble sheets of the shiny, rare metal.
The resulting Project 705 submarine measured 81-meters long but weighed only 3,200-tons submerged. For comparison, the 84-meter-long American Permit class submarine displaced 4,800 tons submerged.
The Alfa featured a typical Soviet double-hull configuration, but only one of its six internal compartments was intended for habitation by the crew. Extraordinary degrees of automation allowed a complement of 15 officers cooped together in the heavily protected third compartment of the vessel, instead of the roughly 100 personnel typical on contemporary SSNs.
In fact, only eight crew could operate virtually every system on the submarine from the command center thanks to its highly automated systems, allowing for very fast reaction times in combat. In the event of misfortune, the crew could make use of a spherical escape capsule built into the sail—the first to be found on a Soviet submarine.
The Alfa’s complement would later be doubled to 32 crew—but no enlisted ratings were invited onboard.
However, as the U.S. Navy discovered decades later while developing the Littoral Combat Ship, this degree of automation meant the small crew was incapable of performing maintenance and repairs while at sea.
The Alfa relied upon reactor consuming 90% enriched uranium-235 fuel, and liquified lead-bismuth-eutectic for cooling to produce 155 MW of power. As the liquified metal would solidify at temperatures below 257 degrees Fahrenheit, the reactors typically had remain warm lest the liquefied metal freeze, rendering the reactor non-functional.
Each Project 705 carried eighteen to twenty 533-millimeter torpedoes which could be automatically loaded into six tubes which could pneumatically ‘pop’ the weapons upwards to engage ships overhead. Optionally, RPK-2 “Starfish” nuclear anti-submarine missiles and ultra-fasted Shkval super-cavitating torpedoes could also be carried. Alfa variants armed with ballistic missiles (705A) or gigantic 650-millimeter torpedo tubes (the 705D) were conceived but never built.
After spending nine years in development, four Alfas were laid down in Severodvinsk and Lenningrad between 1967 and 1969. However, only one—K-64 Leningrad, had been launched and commissioned by the beginning of 1972. That same year, K-64 experienced both cracking in its titanium hull and a leaking liquified metal ‘froze’ on the exterior of the reactor causing irreparable damage. The super-submarine was decommissioned and scrapped just a few years after going on duty.
After several years of tweaking, six more Alfas were finally commissioned between 1977-1981, with later 705K boats using a moderately more reliable BM-40A reactors.
Undeniably, the Project 705 exhibited impressive performance. In a minute and a half, an Alfa could accelerate up to 41 knots (47 miles per hour) while submerged—though some sources claim eve higher speeds were achieved. Their high degree of reserve buoyancy also made them capable of executing fast turns and changes in attitude, and they could dive—and attack from!—depths that NATO torpedoes struggled to atain.
When racing at maximum speed using its steam-turbined turned five-bladed propeller, the Alfa-class was unsurprisingly noisy. But an Alfa commander in need of discretion had another trick he could pull from his sleeve: a secondary propulsion system in the form of two tiny electrically turned propellers that allowed the Alfa to slink around very quietly at low speeds.
The CIA initially mis-identified the Alfas as being diesel-electric submarines due to their small size. But two determined CIA case officers, Herb Lord and Gerhardt Thamm, began closely analyzing photo intelligence and reports on titanium components flowing to mysterious facilities in shipyards in Leningrad and Severodvinsk, as described by Thamm in this article. This led to a more accurate estimate the capabilities of the ‘titanium submarines’ by 1979, prompting the development of more agile Mark 48 ADCAP and Spearfish torpedoes by the U.S. and U.K. respectively.
However, the Pentagon appears to have been fooled by misinformation suggesting much larger-scale production of the Alfa than was the case. In fact, the Alfa had big problems to match its extraordinary speed.
As the special facilities required to keep the liquid metal reactors were often missing or broken-down, Alfa crews resorted to keeping the reactors running full time even while in port, making the reactors very difficult to maintain and unreliable. And the Alfas’ hot-burning reactors had to be replaced entirely after fifteen years in service.
The Alfa’s low reliability and maintainability at sea meant the submarine was conceived of as a sort of “interceptor,” kept ready at port to dash after key surface warships targets. In this role the Alfa amounted to a formidable foe to NATO submariners.
But all but one of the Alfas had been decommissioned by 1990, four of them having had their reactor coolant freeze while deployed at sea. The last ship, K-123, was refit with a pressurized water reactor and was finally decommissioned from duties as a training ship in 1996.
Safe disposal of the Alfa reactor cores encrusted with solidified lead-bismuth also proved quite challenging. Furthermore, over 650 tons of weapons-grade U-235 fuel used by Alfas was found unsecured in warehouses in Kazakhstan in 1994, where they had attracted interest from illegal arms dealers. The uranium was ultimately extracted to the United States using huge C-5 Galaxy cargo planes in a covert operation known as Project Sapphire.
The Alfa represented a design paradigm for “small but fast” attack submarines that would ultimately fall out of favor compared to “big but stealthy” designs like the Russian Akula-class and U.S. Sea Wolf-class SSNs—though isolated media reports have revealed some interest in future Alfa-like boats. Yet stealth, not speed, reigns as king in modern submarine warfare tactics.
That said, for all its serious shortcomings, the Alfa was undeniably a striking and ambitious design that pushed the limits of submarine performance in ways few modern designs even attempt.
Kyle Mizokami is a writer based in San Francisco who has appeared in The Diplomat, Foreign Policy, War is Boring and The Daily Beast. In 2009 he co-founded the defense and security blog Japan Security Watch. This first appeared in 2019 and is being reposted due to reader interest.