Kilo-class submarine

The Kilo-class submarines are a group of diesel-electric attack submarines designed by the Rubin Design Bureau 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.
The first version had the Soviet designation Project 877 Paltus, NATO reporting name Kilo. 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. 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. Due to the delays and other problems with the successor, the Improved Kilo II has been built in larger numbers, with several more units under construction as of 2023.

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, which includes a mine detection and avoidance sonar MG-519 Arfa.
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 and surface vessels with 10 Pa/Hz noisiness in. 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. 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.
Project 636 and 636.3 submarines can launch Kalibr 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.

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. 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, 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, was quieter, faster, and had better detection capabilities. Initially intended for Soviet use, it was made available for export in 1993.
A single Project 877 submarine, Alrosa, is equipped with pump-jet propulsion, instead of a propeller. It has been retrofitted for the Kalibr missile. 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.
It was planned for the Improved Kilo-class to be succeeded by the in Russian Navy service. On 26 December 1997, two boats, one for Russia and one intended for India, were laid down. However, by November 2011 it was apparent that the Lada class would be delayed because, 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. Series production was reported to be underway in the latter 2010s.
The Russian Navy also moved forward with the construction of Project 636.3, also known as Improved Kilo II, the result of further modifications. 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." The class has a seven-bladed propeller, instead of the six-bladed propeller of the Project 877 class. In 2010 construction began on the first unit of the Improved Kilo II,, 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,. The last of these was scheduled to be delivered in 2025.
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. That year the first boat for the Northern Fleet was laid down,, with all six of them to be named after cities in Russian-annexed parts of Ukraine.

Specifications

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.

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
* 17–25 knots submerged
Propulsion: Diesel-electric
Maximum depth: 300 meters
Endurance
* at submerged
* at snorkeling
* 45 days sea endurance
Armament
* Air defence: 8 Strela-3 or 8 Igla-1, but after sea trial it was rejected by the navy.
* Six 533 mm torpedo tubes with 18 53-65 ASuW or TEST 71/76 ASW torpedoes or VA-111 Shkval supercavitating torpedoes, or 24 DM-1 mines,
Crew: 52
Price per unit is US$200–250 million

Operational history

At the beginning of 2014, the Chinese PLA Navy held an emergency combat readiness test. 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 deep. The voyage was notable for creating many firsts for PLAN's submarine service.
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. 8 December 2015 marked the first time a Kilo-class submarine fired cruise missiles against an enemy. struck two targets near the ISIS capital of Raqqa by the missile attack. The B-237 Rostov-on-Don transited the Dardanelles on its way back to the Black Sea on 12 February 2022.
B-871 Alrosa, a pump-jet Kilo class, which derives from the Project 877 hull, participated in the Russo-Ukraine War.
Since the start of the Russian invasion of Ukraine in 2022, the Kilo class submarines of the Black Sea Fleet have participated in the conflict, firing Kalibr cruise missiles into Ukraine. After the sinking of the in April 2022, it was remarked that the Kilo-class subs were the only members of the Black Sea Fleet whose orders did not prohibit venturing into Ukrainian waters near Odesa during the Russian invasion of Ukraine. In September 2022, after the early 2022 Crimea attacks, the UK Ministry of Defence said that the Kilo-class submarines were moved from Sevastopol to the Port of Novorossiysk in Krasnodar Krai.
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.
According to satellite images taken in June 2024, the submarine was moved to a lesser used dry dock within the port. 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.
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. Other sources claim that the submarine was only hit and not sunk. Satellite images showed the that camouflage nets were burned out by the strike.
In September 2025, the Project 636.3 boat, Novorossiysk, reportedly suffered serious damage as the result of a fuel system malfunction while operating in the Mediterranean.
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. Satellite imagery published after the attack showed that the drone struck a pier 20 meters off the stern. Russia claimed that the attack didn't damage the vessel. Other sources say that it is unclear if the attack damaged the submarine. The UK Ministry of Defence considered it highly likely that the attacked submarine was the B-271 Kolpino, noted that 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.

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, while new Improved Kilo–class subs are being delivered through the 2020s to replace them. About forty vessels have been exported to several countries:

*: 2 original Kilo, 4 Improved Kilo.
*: 2 original Kilo, 10 Improved Kilo.
*: 10 original Kilo, 1 sustained major casualty – designated as the
*: one boat transferred from Indian Navy by March 2020.
*: 1 original Kilo –.
*: 3 original Kilo.
*: 1 original Kilo – .
*: 5 original Kilo, 12 Improved Kilo delivered as of 2025. up to six additional Project 636.3 intended to replace remaining Project 877 units; first three ordered in 2023.
*: 6 Improved Kilo –,,,,,.

Possible purchasers

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.
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.

Failed bids

The Indonesian Navy was interested in purchasing two used Kilo-class submarines, but the Chief of Staff of the Indonesian Navy Laksamana Marsetio 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, including a transfer of technology, where Indonesia will eventually build four of six of the submarines with South Korea.

List of submarines

Project 877

Operator	#	Name	Shipyard	Project	Laid down	Launched	Commissioned	Fleet	Status
	B-248		Komsomolsk-on-Amur	877
	B-260	Chita	Komsomolsk-on-Amur	877				PF
	B-227	Vyborg	Komsomolsk-on-Amur	877				BF
	B-229		Komsomolsk-on-Amur	877
	B-404		Komsomolsk-on-Amur	877
	B-401	Novosibirsk	Nizhniy Novgorod	877				NF
	B-402	Vologda	Nizhniy Novgorod	877				NF
	B-405		Komsomolsk-on-Amur	877
	291		Nizhniy Novgorod	877E					as of 2010
	581	Delfinul	Nizhniy Novgorod	877E					Unknown
	S55		Saint Petersburg	877EKM
	B-470		Komsomolsk-on-Amur	877
	B-806	Dmitrov	Nizhniy Novgorod	877EKM				BF	as of 2025
	S56		Saint Petersburg	877EKM
	012		Nizhniy Novgorod	877EKM					Upgraded in 2010, able to launch Kalibr/Club missiles
	B-439		Komsomolsk-on-Amur	877
	S57		Nizhniy Novgorod	877EKM					as of 2010, modernized to project 08773 in 1999–2001
	013		Nizhniy Novgorod	877EKM					Upgraded in 2011, able to launch Kalibr/Club missiles
	71	UMS Minye Theinkhathu	Saint Petersburg	877EKM					Modernized to project 08773 in 1997–1999, transferred to Myanmar Navy in 2020
	B-445	Svyatoi Nikolai Chudotvorets	Komsomolsk-on-Amur	877				PF	May have decommissioned 2020; listed as still in service by one source
	S59		Nizhniy Novgorod	877EKM					as of 2010, modernized to project 08773 in 2001–2003
	S60		Saint Petersburg	877EKM					as of 2010, modernized to project 08773 in 1999–2001
	B-808	Yaroslavl	Nizhniy Novgorod	877				NF
	B-394	Nurlat	Komsomolsk-on-Amur	877				PF	Status unclear; active as of 2018; likely to decommission in mid/latter 2020s
	B-800	Kaluga	Nizhniy Novgorod	877LPMB				NF
	S61		Saint Petersburg	877EKM
	B-464	Ust'-Kamchatsk	Komsomolsk-on-Amur	877				PF	Status unclear; active as of 2018; likely to decommission in mid/latter 2020s
	B-459	Vladikavkaz	Nizhniy Novgorod	877				NF
	S62		Saint Petersburg	877EKM					Modernized to project 08773 in 2005–2007. About to undergo mid-life refit as of 2025.
	B-871	Alrosa	Nizhniy Novgorod	877V				BSF
	B-471	Magnitogorsk	Nizhniy Novgorod	877				NF	Status unclear as of 2025; active as of 2018
	B-494	Ust'-Bolsheretsk	Komsomolsk-on-Amur	877				PF
	901		Saint Petersburg	877EKM					as of 2012. Upgraded in Iranian shipyard.
	B-187	Komsomolsk-on-Amur	Komsomolsk-on-Amur	877				PF
	B-177	Lipetsk	Nizhniy Novgorod	877				NF	Status unclear as of 2025; active as of 2018
	B-190	Krasnokamensk	Komsomolsk-on-Amur	877				PF
	902		Saint Petersburg	877EKM					Unknown
	B-345	Mogocha	Komsomolsk-on-Amur	877
	364	Yuan Zheng 64 Hao	Nizhniy Novgorod	877EKM	???
	365	Yuan Zheng 65 Hao	Nizhniy Novgorod	877EKM	???
	903		Saint Petersburg	877EKM
	S63		Saint Petersburg	877EKM					It was later scuttled.
	S65		Saint Petersburg	877EKM					as of 2010

Project 636.3

Italics indicate estimates.
Russian designation Project 636.6 is known as the "Improved Kilo II" class in the West.

Operator	#	Name	Shipyard	Project	Laid down	Launched	Commissioned	Fleet	Status
	B-261		Saint Petersburg	636.3	20 Aug 2010	28 Nov 2013	22 Aug 2014	BSF	Active; as of 2025 has a serious technical problem with diesel leaking from the fuel system into the submarine.
	B-237		Saint Petersburg	636.3	21 Nov 2011	26 Jun 2014	30 Dec 2014	BSF	Damaged by the cruise missile strike on Sevastopol drydock on 12 Sep 2023; taken in for repair in dry dock; claimed sunk by Ukraine in a second strike in Aug 2024
	B-262		Saint Petersburg	636.3	17 Aug 2012	28 Aug 2014	25 Jun 2015	BSF	Active
	B-265		Saint Petersburg	636.3	20 Feb 2014	25 Apr 2015	5 Nov 2015	BSF	Reported active in the Mediterranean as of 2026
	B-268		Saint Petersburg	636.3	30 Oct 2014	18 Mar 2016	25 Oct 2016	BSF	Active
	B-271		Saint Petersburg	636.3	30 Oct 2014	31 May 2016	24 Nov 2016	BSF	highly likely docked in Port of Novorossiysk, likely significantly damaged and unable to deploy or sail of its own accord.
	B-274		Saint Petersburg	636.3	28 Jul 2017	28 Mar 2019	25 Nov 2019	PF	Active
	B-603		Saint Petersburg	636.3	28 Jul 2017	26 Dec 2019	24 Oct 2020	PF	Active; carried out land-attack cruise missile tests in Jan 2022
	B-602		Saint Petersburg	636.3	1 Nov 2019	26 Mar 2021	12 Oct 2021	PF	Active; deployed in the Pacific fleet late 2022
	B-588		Saint Petersburg	636.3	1 Nov 2019	31 Mar 2022	16 Nov 2022	PF	Active
	B-608		Saint Petersburg	636.3	23 Aug 2021	27 Apr 2023	28 Nov 2023	PF	Active
	B-???		Saint Petersburg	636.3	23 Aug 2021	11 Oct 2024	11 Jun 2025	PF	Active
	B-???	Petrozavodsk	Saint Petersburg	636.3	2022		2025	BF	Ordered in 2020, improved design
	B-???	Mariupol	Saint Petersburg	636.3	Autumn 2024		2027	NF	Ordered in 2022
	B-???	Donetsk	Saint Petersburg	636.3	2023		2026	BF or NF?	Both ordered in 2022; two additional submarines with names Kherson & Zaporozhye also reported planned
	B-???	Lugansk	Saint Petersburg	636.3	2025		2028	BF or NF?	Both ordered in 2022; two additional submarines with names Kherson & Zaporozhye also reported planned