The nuclear attack submarine

During decades submarines were considered just the perfect weapon to wage war against the enemy merchant fleet. But during the Second World War there was an American submarine which in just four days detected, chased and sank three Japanese submarines. This showed that the importance of submarines in antisubmarine warfare could be considerable. In 1954 was commissioned the USS Nautilus, which being the first nuclear submarine in History, was as well the first "true" submarine and the first "modern" attack submarine.

However, in those years "teardrop" hulls more hydrodynamical than that of the USS Nautilus were already being designed. In 1959 was commissioned the first submarine which combined nuclear propulsion and a teardrop hull, the USS Skipjack, whose speed, over 30 knots while in immersion, remained unbeaten until the commissioning of the Los Angeles class in 1976.

The fact that nowadays a submerged submarine is capable of launching surface-to-surface missiles from her torpedo tubes, as well as cruise missiles from vertical launchers, has further diversified the role of every submarine. Hence modern submarines are classified in just two groups: SSN (for attack submarines) and SSBN (for ballistic missile submarines), for clear differences exist between these two groups.

Nowadays only three western countries have built and operate nuclear attack submarines: United States, United Kingdom and France. The next western country to join this small club should be Brazil, around 2025 perhaps. On the side of the countries that were ever confronted with the western powers, only Russia and China have built and operated such vessels, the first one in larger quantity. India is currently operating a nuclear attack submarine leased from Russia, and at the same time planning its own SSN for the future.

The nuclear attack submarine in the West

The North American nuclear attack submarine fleet started in 1954 with the commission of the USS Nautilus, to which followed in 1957 the USS Seawolf and from that same year also the four vessels of the Skate class. All of these submarines had in common a ship-like shaped prow and a propulsion plant with a single reactor and two shafts. From 1959 followed the six vessels of the Skipjack class, which as novelty incorporated a teardrop hull and propulsion by single shaft. All of these models were armed with six 533-millimeter torpedo tubes placed in the prow and none of them fired missiles.

The fourteen vessels of the Thresher class (later denominated Permit class) entered service in 1962. These vessels were powered by a single reactor Westinghouse S5W (same model as that used in the Skipjack class) and propelled by a single propeller. They were armed with four 533-millimeter torpedo tubes and initially equipped only with torpedoes. From the late 1960s they were prepared to fire antisubmarine missiles SUBROC and from the late 1970s also encapsulated antiship missiles Harpoon.

The leading vessel of the class was lost the 10th April 1963 during test depth trials, and with her died 112 mariners and 17 civilians. In the following photograph we can see the USS Barb (SSN-596) following the trail of the USS Thresher (SSN-593) on that fatidic day.

Thresher class nuclear attack submarine USS Barb
The Sturgeon class, formed by 37 vessels, was actually a remodelation of the Thresher class, with modifications that helped to navigate under the ice, such as hydroplanes which could rotate 90 degrees until being in vertical position. The first vessel was commissioned in 1967 and the last one in 1975. Some of the last vessels were provided with a towable sonar BQS-13. The propulsion plant continued using the reactor Westinghouse S5W. From the mid 1980s, the four torpedo tubes could fire, besides the other aforementioned weapons, the cruise missile Tomahawk, which has a range from 1200 to 2500 kilometers.

The following class was Los Angeles, 62 vessels that were commissioned between 1972 and 1996 to counter the Soviet class Victor, deployed from 1967. They were powered by one reactor General Electric S6G. They were armed with four 533-millimeter capable of launching cable-guided torpedoes Gould Mk 48, antiship missiles Harpoon and cruise missiles Tomahawk, or laying mines CAPTOR or Mobile. From the twelveth vessel of the class they were provided with twelve vertical launchers for missiles Tomahawk, placed outside the pressure hull between the conning tower and the sonar AN/BQQ-5, and hydroplanes were added in the fore section of the hull. As 2016 remain in service 39 units, constituting this one the most numerous class of nuclear submarines in service in the world.

The following class was the Seawolf, of which only three vessels are - and will be - in service, for they surpass the previous class not only in prestations but in price as well, being the most expensive SSN ever built. They are powered by one reactor Westinghouse S6W. While in immersion they are capable of silent speeds of up to 20 knots and a maximum speed of up to 35 knots. They can reconfigure their armament an even transport a group of 50 commandos. They have eight 660-millimeter torpedo tubes, emplaced amidships, which can launch cable-guided torpedoes Gould Mk 48, antiship missiles Harpoon and cruise missiles Tomahawk, or lay up to 100 mines. The military effectiveness of these vessels was estimated as triple than that of the previous class. They were designed to face the last models of Soviet submarines, but their price of one billion dollars each along with the reduction of the Soviet threat led to the cancellation of 26 units.

Seawolf class nuclear attack submarine USS Seawolf
The last class in service with the US Navy is the Virginia, conceived as a less expensive alternative to the Seawolf class. The new class is slowly replacing the submarines of the Los Angeles class, many of which have already been decommissioned. These new submarines, of which 48 have been planned, are expected to be acquired until 2043 and to remain in service as much as 2070. To see that the most powerful navy in the world pretends to go throughout a period longer than the Cold War era was, with the same class of submarines, clearly indicates how much the state of things has changed since the end of that era. This new class is armed with four 533-millimeter torpedo tubes capable of firing missiles and twelve vertical launchers for the cruise missile Tomahawk.

At the other side of the Atlantic, the Royal Navy received its first nuclear submarine in 1963, which not surprisingly was called HMS Dreadnought; but this time the technical primacy was not British and she was powered by an American reactor, the S5W. Later followed the five vessels of the Valiant class, commissioned between 1966 and 1971, the three vessels of the Churchill class, in 1970-1971, and the six vessels of the Swiftsure class, between 1973 and 1982. These three classes of submarines featured propulsion plants with a single reactor Rolls-Royce and a single shaft, and were armed with 533-millimeter torpedo tubes (five in the Swiftsure class and six in the others) prepared for launching antiship missiles Harpoon or laying mines. As 2016 all of these classes have been retired.

The following cutaway model corresponds to a British nuclear attack submarine of the Swiftsure class. These vessels had a length of 82.9 meters, a beam of 9.8 meters and a displacement of 4400 tonnes while in surface. They had a complement of 116 crewmen and were capable of a speed of 30 knots while submerged. Their armament comprised five torpedo tubes capable of firing surface-to-surface missiles. Two of these submarines saw service in the Falklands War in 1982.

Cutaway of a Swiftsure-class nuclear attack submarine
From 1983 were commissioned the seven vessels of the Trafalgar class, of which four remain currently in service. This class is just a refinement of the Swiftsure class including a new reactor core and sonar, having a similar internal layout and being only 2.5 metres longer. Improvements include several features to reduce underwater noise emissions, such as a "second skin" formed by anechoic tiles which allows to reduce acoustic signature against active sonars. These tiles are prone to get detached from the hull and have to be constantly replaced. Unlike previous classes, the Trafalgar uses a "pumpjet" propulsion system instead of a conventional propeller. And like other British classes of submarines, it is built with reinforced fins and retractable hydroplanes to allow emersion through thick ice caps.

The replacement of these submarines will be the seven vessels planned so far of the Astute class, of which three are already in service as 2016. They are a refinement of the Trafalgar class and they shall not require to have their nuclear fuel replenished during their whole service life. With a length of 97 meters and a displacement of 7400 tonnes while in immersion, they are largest than any of the aforementioned classes of British nuclear attack submarines. They have six 533-millimeter torpedo tubes which can launch torpedoes Spearfish (guided either by cable or autonomous active/passive sonar), antiship missiles Harpoon and cruise missiles Tomahawk, or lay mines.

Finally, France designed its fleet of nuclear submarines in a different way, for since the first moment this country focused its efforts into the SSBN branch instead of the SSN one, of which no vessel was in service until the commissioning, from 1983, of the six vessels of the Rubis class. With a length of 73.6 meters and a displacement of 2600 tonnes while in immersion, these submarines are smaller than SSN usually are. They are powered by one nuclear reactor K48 and propelled by a single propeller. Their armament comprises four 533-millimeter torpedo tubes which can launch torpedoes ECAN L5 Mk 3 and encapsulated antiship missiles Exocet, or lay up to 32 mines FG 29. As 2016 all the six vessels remain in service. Meanwhile, three new submarines of the new class Barracuda are in construction, to be delivered from 2018.

Rubis class nuclear attack submarine

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