Los Angeles class:The benchmark SSN

Intro-USN was facing a dilemma, its carriers were being shadowed by November class SSNs which could keep up with them at speeds over 30knots. This was highlighted by an incident in 1968 during which a November shadowed USS Enterprise even though the carrier was sailing at its top speed, proving that the west had underestimated the speed of this SSN. Intelligence received hinted towards a new SSN under development, which would enter service as the Victor having a 33kn top speed. Sturgeons  and Permits  managed top speeds only in higher 20s ie around 26-28kn meaning a total of 5-7kn speed disadvantage which is a lot . For USN, this translated into their acoustically superior submarines being out run by acoustically inferior submarines when the former was detected. This could also mean that the carriers needed to sail at slower speeds so that their escorting SSNs could keep up. Thus to counter this, development of a new SSN was started which would be a bench mark for all SSNs of the future and become the most produced nuclear powered submarine ever designed, this SSN would enter service as the Los Angeles class.

6USS Los Angeles SSN-688 under way

Under the guidance of Admiral Rickover, famous for building USN’s nuclear powered submarine fleet, design work on LA was started. He stressed on a new 30,000 HP reactor+turbine combination, originally developed for surface vessels,  to power this new SSN. It would be designated S6G by the USN. Los Angeles would end up being 10m wide and 110m long to fit this reactor, its piping and all the quietening equipment along with all other things needed by the submarine to perform its roles inside the hull. The hull itself was designed to be thin thus reduce weight and increase speed. This meant, Los Angeles would be the fastest American submarine in service at the cost of diving depth. She would displace close to 6900 tonnes which was 45% more than its preceding Sturgeons. Top speed was close to 33kn which was equivalent to that of early Victors.  It featured a large spherical sonar array in the bow and 2 towed sonar arrays (except for the first 2 LAs ie Los Angeles and Baton Rouge which had only 1 towed array) modified for low and medium frequency range. Weapons payload included 27 internal weapons which can be deployed through 4x533mm torpedo tubes. The payload could be tailored for mission requirements,  and any combination of the following weapons could be chosen.

  •  Mk48 later replaced by Mk48 ADCAP torpedoes,
  • TLAM,
  • TASM (Tomahawk Anti Ship Missile)
  • Harpoons and
  • Mines (on the later variants).

Flight 2 added 12 VLS cells which could house both the variants of Tomahawks and free spaces in the torpedo compartment for other weapons

010221-N-0000X-003In this pic the region marked by “1” shows the 5inch counter measure tubes of an LA and the region marked by “2” has the torpedo tubes

 Like all submarines, its sail had an array for sensors for ops at the surface or at periscope depth. It has 2 periscopes, Type 8 for observation and surface attacks and Type 18 for surveillance of surface targets. It also sports ESM antenna for detecting any vessels/aircraft with their radar working and a snorkel for running its diesel engines . The sail also sports a special sonar named MIDAS which stands for MIne Detection and Avoidance System, it is used for what its name suggests and under ice ops. by finding the thinnest of the ice so that the submarine can surface undamaged.  At the end of the sail in the following pic, we can see a wire which is called as the trailing wire. This is generally used to call submarines to the surface/periscope depth for communications or send/receive short messages when the submarine cannot surface.

1Sensor array on the sail

The first Los Angeles, obviously christened as USS Los Angeles SSN-688, was laid down at Newport News ship building yard on 8th of Jan 1972,  she was launched on 6th of April 1974 and commissioned on 13th of November 1976. She served for 33 years, during the height of cold war and formally decommissioned nearly 2 decades after it ended.  She had one of the longest careers of a USN submarine.

6USS Key West at periscope depth with her sensor array deployed.

Production was started in the year 1971 as stated above, and went on till 1996. Problems faced during construction meant that LAs were built with a lower grade steel ie HY-80 instead of the superior HY-100. This limited the diving depth to its present 300m, if HY-100 had been used, the diving depth would be 400m, it would have helped a lot as Soviet submarines like Victors could dive to 400m and LA would have been a perfect counter. Three different variants were produced, namely Flights 1, 2 and 3. Flight 1 was the basic variant, of which 31 copies were made. It was felt that the armament was less for its size especially compared to Soviet submarines hence Flight 2 featured additional 12 VLS cells for TLAM or TASM (before TASM was retired from service). Lot of development had taken place in  various fields after the Los Angeles had entered service hence the Flight 3  (often called 688I or the Improved LA) of the class featured several changes which are listed below.

  • Better quietening
  • New electronics,
  • Probably a more powerful variant of the reactor as well, thus increasing their speed further,
  • Hardened sail for under ice ops,
  • A shrouded propeller,
  • Control planes were moved from sail to bow.
  • From USS Miami, integrated sonar suite named BSY-1.

6USS San Juan, the first Flight 3/688I SSN to be commissioned, we can see the clean sail as the control planes have been shifted to bow and the light rectangular patch near the top of the sail is where MIDAS is placed.

USS Cheyenne and probably USS Greenville also featured 2 large wide aperture arrays, 1 on each side to test the concept for eventual deployment on Seawolf and Virginia classes.  A total of 62 LAs were produced divided into 31 of Flight 1, 8 Flight 2 and 23 Flight 3.

los angeles class (5)The shrouded propeller and wide aperture array is marked in this pic, taken during USS Cheyenne’s roll out ceremony.

The Soviets were developing Victors, so that they could completely outclass Sturgeons and were surprised to see this new SSN which was much quieter yet faster. Los Angeles gave the Americans total supremacy in the oceanic depths as early Victors were noisier and older Novembers were simply no match. The Soviets were thus forced to develop newer SSNs like the Akula and Yasen (although it entered service decades later than it was supposed to) to counter the threat. LAs successfully trailed Soviet SSBNs and SSNs for much longer time compared to older American SSNs.Reportedly, an  LA was usually stationed near all major Soviet submarine bases to gain contact with and trail any out going Russian submarine irrespective of the type.  LAs armed with VLS cells were tasked with striking tactical and strategic targets along with enemy shipping during the cold war. They did it successfully in post cold war conflicts in the middle east. They could also be fitted with a Dry Dock Shelter (DDS) or Seal Delivery System (SDS) to deploy a team of special forces operatives during combat or peace time for intelligence and various other operations. Like all weapon systems, it had its own weaknesses, it had sacrificed diving depth for speed. The Soviets were quick to understand this flaw and formulated tactics to use this drawback.  Soviet skippers were instructed to dive beyond 300m, if an American SSN was detected trailing them,  Alfa skippers were the first to apply this against Sturgeons, this was later perfected against the Los Angeles.

USS DallasHere is the famous USS Dallas with a DDS

6Here is USS Greenville with an SDS

Overall these submarines were game changing, these were quiet and gave an unmatched edge to the Americans interms of quietness. The Soviets only managed to surpass it near the end of cold war by fielding much smaller numbers of Akulas (around 5)  and Victor 3s (around 26) against more than twice the number of LAs ready for combat at any time. Over the years, many LAs featured in books and movies, off which USS Dallas became the single most famous LA after her role in the book and the movie The Hunt for Red October. It has been claimed that after the movie was released, her unofficial moto is “The hunt begins”. Around 40 of these still remain in service with Dallas retiring pretty soon. She might be preserved as a museum, making her one of the few nuclear powered submarines to be preserved as museums.

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2 thoughts on “Los Angeles class:The benchmark SSN

  1. Thank you for this blog(?). I love reading this and I appreciate your unbiased view on both American and Russian/Soviet equipment. I hope you plan on writing more because I will sure as hell read it!

    Like

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