Russian Project 877 in the English Channel in 2018A Russian Kilo-class submarine underway on the surface
The Kilo-class submarines are a group of diesel-electricattack submarines designed by the Rubin Design Bureau[1][3][4] in the Soviet Union in the 1970s and built originally for the Soviet Navy. Since it was introduced, more than 70 Kilo class boats have been built, and around 60 were in active service as of 2023, not only in Russia but also in Algeria, Vietnam, India, Iran, Myanmar, and Poland.[5]
The first version had the Soviet designation Project 877 Paltus (Russian: Па́лтус, meaning "halibut"), NATO reporting nameKilo.[6] They entered operational service in 1980 and continued being built until the mid-1990s, when production switched to the more advanced Project 636 Varshavyanka variant, also known in the West as the Improved Kilo class.[7][8][9] The design was updated again by the Russian Navy in the mid-2010s, to a variant called Project 636.3, also known as Improved Kilo II.[6] Due to the delays and other problems with the successor Lada-classsubmarine, the Improved Kilo II has been built in larger numbers, with several more units under construction as of 2023.[5]
Role
The Project 877 attack submarines were mainly intended for anti-shipping and anti-submarine operations in relatively shallow waters. Original Project 877 boats are equipped with Rubikon MGK-400 sonar system (with NATO reporting name Shark Gill), which includes a mine detection and avoidance sonar MG-519 Arfa (with NATO reporting name Mouse Roar).
Newer Project 636 boats are equipped with improved MGK-400EM, with MG-519 Arfa also upgraded to MG-519EM. MGK 400E can detect submarines with 0.05 Pa/Hz noisiness in 16km (9.9mi) and surface vessels with 10 Pa/Hz noisiness in 100km (62mi).[10] The improved sonar systems have reduced the number of operators needed by sharing the same console via automation.
Anechoic tiles are fitted on casings and fins to absorb the sound waves of active sonar, which results in a reduction and distortion of the return signal.[11] These tiles also help attenuate sounds that are emitted from the submarine, thus reducing the range at which the submarine may be detected by passive sonar.[12]
Project 636 and 636.3 submarines can launch Kalibr (and their Club export version) cruise missiles. It was reported in September 2022 that they can carry four Kalibr missiles, and can launch them through two of their six torpedo tubes.[13]
History
Kilo-class attack submarines began entering service with the Soviet Navy from 12 September 1980. They were originally intended for the Warsaw Pact nations, which is why their Russian nickname is Varshavyanka (woman from Warsaw). Among the first to be built, 13 were from the Krasnoye Sormovo Factory No. 112 in Nizhny Novgorod, and nine were from Amur Shipbuilding Plant in Komsomolsk-on-Amur. After the dissolution of the Soviet Union, another two Project 877 submarines were built for the Russian Navy in the 1990s. The Krasnoye Sormovo facility partnered with Admiralty Shipyards in Saint Petersburg to built 21 boats for foreign buyers (as of 2001), which included China, India, Algeria, Iran, Poland, and Romania, for a total of 45 units. Modified units for export were designated Project 877E, and those made for tropical waters were Project 877EKM. Another variant, Project 636 (NATO: Improved Kilo), was quieter, faster, and had better detection capabilities. Initially intended for Soviet use, it was made avaliable for export in 1993.[14]
A single Project 877 submarine, B-871Alrosa, is equipped with pump-jet propulsion, instead of a propeller.[15] It has been retrofitted for the Kalibr missile.[16] Its modification was started in 1990 and was not completed until 2000. When it returned to service, it was the only operational submarine in the Black Sea Fleet at the time.[14]
It was planned for the Improved Kilo-class (Project 636) to be succeeded by the Lada class (Project 677) in Russian Navy service. On 26 December 1997, two boats, one for Russia and one intended for India, were laid down.[14] However, by November 2011 it was apparent that the Lada class would be delayed because Sankt Peterburg, the lead boat of the class, had shown major deficiencies. On 27 July 2012, the Russian Navy commander-in-chief announced that construction of the Lada-class submarines would resume, having undergone design changes.[citation needed] Series production was reported to be underway in the latter 2010s.[17][needs update]
The Russian Navy also moved forward with the construction of Project 636.3, also known as Improved Kilo II, the result of further modifications.[5] The class "is slightly longer in length — the sub's submerged displacement is around 4,000 tons — and features improved engines, an improved combat system, as well as new noise reduction technology; it can fire both torpedoes and cruise missiles, launched from one of six 533-millimeter torpedo tubes."[1] The class has a seven-bladed propeller, instead of the six-bladed propeller of the Project 877 class.[16] In 2010 construction began on the first unit of the Improved Kilo II, Novorossiysk, which was part of a batch of six submarines built for the Black Sea Fleet. The last of this group was delivered in 2016. Another six were ordered for the Pacific Fleet, with the first entering service in 2019,[5][4]Petropavlovsk-Kamchatsky.[18] The last of these was scheduled to be delivered in 2025.[19]
In June 2022, an unconfirmed report from within Russia's defense industry suggested that a further tranche of six additional Project 636.3 vessels might be ordered to start construction in around 2024.[5][20] That year the first boat for the Northern Fleet was laid down, Mariupol, with all six of them to be named after cities in Russian-annexed parts of Ukraine.[21]
There are several variants of the Kilo class. The information below is the smallest and largest number from the available information for all three main variants of the boat.[22]
Displacement:
2,300–2,350 tons surfaced
3,000–4,000 tons submerged
Dimensions:
Length: 70–74 meters
Beam: 9.9 meters
Draft: 6.2–6.5 meters
Maximum speed
10–12 knots surfaced (18–22km/h)
17–25 knots submerged (31–46km/h)
Propulsion: Diesel-electric 5,900shp (4,400kW)
Maximum depth: 300 meters (240–250 meters operational)
Endurance
400 nautical miles (700km) at 3 knots (6km/h) submerged
6,000 nautical miles (11,000km) at 7 knots (13km/h) snorkeling (7,500 miles for the Improved Kilo class)
Price per unit is US$200–250million (China paid about US$1.5–2billion for 8 Project 636 Kilo-class submarines)[when?][citation needed]
Operational history
At the beginning of 2014, the Chinese PLA Navy held an emergency combat readiness test.[23] The Kilo-class submarine Yuanzheng 72, deployed on a combat readiness voyage encountered a "cliff" caused by a sudden change in seawater density. Because the seawater density suddenly decreased, the submarine lost its buoyancy and rapidly descended. The pressure on the submarine increased sharply, and the main engine room pipeline was damaged, and water entered. The vessel lost power due to a large amount of water entering the main engine room. The crew reacted quickly, and the submarine resurfaced in three minutes, avoiding a disastrous descent to the seabed, which was more than 3,000 metres (9,800ft) deep. The voyage was notable for creating many firsts for PLAN's submarine service.[24][25]
In 2015, five Kilo-class submarines were deployed to the Russian naval facility in Tartus, Syria. At least two of the units reportedly attacked land targets inside Syria with 3M54 Kalibr cruise missiles (NATO designation: SS-N-27A "Sizzler").[4] 8 December 2015 marked the first time a Kilo-class submarine fired cruise missiles against an enemy. Rostov-na-Donu struck two targets near the ISIS capital of Raqqa by the missile attack.[26] The B-237 Rostov-on-Don transited the Dardanelles on its way back to the Black Sea on 12 February 2022.[27]
B-871 Alrosa, a pump-jet Kilo class, which derives from the Project 877 hull, participated in the Russo-Ukraine War.
On 13 September 2023, B-237 Rostov-on-Don was severely damaged by a Ukrainian Storm Shadow missile strike while it was drydocked in Sevastopol.[30][31][32] According to satellite images taken in June 2024, the submarine was moved to a lesser used dry dock within the port (at coordinates 44.609975029014116, 33.537496816089906). Camouflage nets were, at least initially, thrown up to disguise its presence and to make observation more challenging. According to reports, the submarine is under repair.[33]
On 2 August 2024, Ukrainian Forces launched a strike against a Russian submarine and an S-400 air defense system in Crimea. Ukrainian sources claimed that the submarine B-237 Rostov-on-Don was "sunk on the spot" in the attack.[34][35][36][37][38] Other sources claim that the submarine was only hit and not sunk.[39] Satellite images showed the that camouflage nets were burned out by the strike.[40]
In September 2025, the Project 636.3 boat, Novorossiysk (B-261), reportedly suffered serious damage as the result of a fuel system malfunction while operating in the Mediterranean.[41]
December 2025 explosion in the Port of Novorossiysk
In December 2025, the Security Service of Ukraine published a video showing an explosion near an unnamed Kilo-class submarine in the Port of Novorossiysk, claiming that the submarine was struck by a "Sub Sea Baby" drone.[42] Satellite imagery published after the attack showed that the drone struck a pier 20 meters off the stern, with no apparent damage to the submarine.[43][44][45] The UK Ministry of Defence considered it highly likely that the attacked submarine was the B-271 Kolpino, noted that as of 18December2025[update] the submarine was docked where it was attacked and considered it likely that the attack had significantly damaged the submarine, leaving it unable to deploy or sail of its own accord.[46]
Operators
The first submarine entered service in the Soviet Navy in 1980, and the class remains in use with the Russian Navy today; around 5 original Kilo-class vessels believed to still be in active service with the Russian Navy (as of 2025), while new Improved Kilo–class subs are being delivered through the 2020s to replace them. About forty vessels have been exported to several countries:
Russian Navy: 5 original Kilo (Project 877) (status of 4 others, 2 Pacific & 2 Northern Fleet unclear), 12 Improved Kilo (Project 636.3)[60] delivered as of 2025.[61][62] up to six additional Project 636.3 intended to replace remaining Project 877 units; first three ordered in 2023.[63][64][65]
The government of Venezuela expressed interest since 2005 in acquiring nine AIP-powered conventional submarines, either the German U214 or later the Amur 1650. There was a Russian counteroffer due to technical issues at the shipyards back then, for five Project 636 Kilo-class and four Amur 1650, but it hasn't gone through yet.[69]
In 2017, the Philippine Navy showed interest in the Kilo-class submarine as part of its modernization program. Defense Secretary Delfin Lorenzana said the country was evaluating a Russian offer.[70]
Failed bids
The Indonesian Navy was interested in purchasing two used Kilo-class submarines, but the Chief of Staff of the Indonesian NavyLaksamanaMarsetio cancelled the plans in 2014 after inspecting the two submarines in Russia with an Indonesian Navy team. He said, "The submarines look good on the outside, but the inside is filled with broken equipment, and the two submarines have been in storage for two years." Indonesia instead bought six Improved Jang Bogo-class submarines, later known as Nagapasa-class submarine, including a transfer of technology, where Indonesia will eventually build four of six of the submarines with South Korea.[71]
Damaged by the cruise missile strike on Sevastopol drydock on 12 Sep 2023;[109] taken in for repair in dry dock;[33][110] claimed sunk by Ukraine in a second strike in Aug 2024[111]
As of December 2025[update] highly likely docked in Port of Novorossiysk, likely significantly damaged and unable to deploy or sail of its own accord.[46]
12"АПЛ Проекта 636.3"[Project 636.3 Nuclear Submarine]. pp.userapi.com (in Russian). Archived from the original on 30 August 2017. Retrieved 30 August 2017.
↑Anechoic tiles are fitted on casings and fins to absorb the sonar sound waves of active sonar, which results in a reduction and distortion of the return signal.
123Polmar, Norman; Moore, K. J. (2003). Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines, 1945–2001. Dulles, Virginia: Potomac Books Inc. pp.214―218. ISBN1-57488-594-4.
Darman, Peter, ed. (2004). Twenty-first Century Submarines and Warships. Military Handbooks. Rochester: Grange Books. ISBN1-84013-678-2.
Gardiner, Robert; Chumbley, Stephen; Budzbon, Przemysław, eds. (1995). Conway's All the World's Fighting Ships 1947–1995. Annapolis: Naval Institute Press. ISBN1-55750-132-7.
Further reading
Breemer, Jan S. (1989). Soviet Submarines: Design, Development and Tactics. Coulsdon, Surrey: Jane's Information Group. ISBN0710605269.
Miller, David; Jordan, John (1987). Modern Submarine Warfare. New York: Military Press. ISBN0-517-64647-1.
Miller, David (1989). Modern Submarines. Combat Arms. New York: Prentice Hall Press. ISBN0-13-589102-7.
Polmar, Norman; Moore, Kenneth J. (2004). Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines. Washington, D.C.: Potomac Books. ISBN978-1-57488-594-1.
Polmar, Norman; Noot, Jurrien S. (1991). Submarines of the Russian and Soviet Navies, 1718-1990. Annapolis, Maryland: Naval Institute Press. ISBN0-87021-570-1.
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