Indonesian submarine sunk in 2021
KRI "Nanggala" (402), also known as Nanggala II, was one of two Type 209/1300 diesel-electric attack submarines of the Indonesian Navy. It sank following an implosion in April 2021.
Ordered in 1977, "Nanggala" was launched in 1980 and commissioned in 1981. It conducted intelligence gathering operations in the Indian Ocean and around East Timor and North Kalimantan. It was a participant of the international Cooperation Afloat Readiness and Training naval exercise and conducted a passing exercise with . The vessel underwent major refits by Daewoo Shipbuilding &amp; Marine Engineering (DSME) in 2012 and Indonesian state-owned shipyard PT PAL in 2020.
On 21 April 2021, the ship went missing during a routine exercise in the Bali Sea. It was commanded by Colonel Harry Setyawan, and had 49 crewmembers and 3 weapon specialists on board. The Indonesian Navy, assisted by other countries, conducted a search, and three days later debris was discovered from the point of last contact, and "Nanggala" was declared sunk. There were no survivors; all 53 people on board the ship died. On 26 April, the Indonesian government awarded posthumous promotions to everyone aboard the ship.
The cause of the sinking is presumed to be a power outage. "Nanggala" had experienced outages before but recovered successfully. Lt. Col. Heri Oktavian, who was killed in the incident, had previously voiced his frustrations about the maintenance of the ship; he claimed that the workmanship quality and maintenance services performed by state-owned naval dockyard PT PAL were unsatisfactory.
Name.
The submarine was named after the "Nanggala", a powerful, divine short spear wielded by Prabhu Baladewa, a Hindu god mentioned in the "Mahabharata" and a character in "wayang" puppet theatre. Legend states that the spear is capable of melting mountains and splitting oceans.
The vessel was also known as "Nanggala II" in order to differentiate it from RI "Nanggala" (S-02), an older submarine sharing the same name.
Design and construction.
KRI "Nanggala" was ordered on 2 April 1977 and was financed as part of a US$625 million loan by the West German government to the Indonesian government. About $100 million was spent on the submarine and its sister vessel, . The vessel was designed by Ingenieurkontor Lübeck of Lübeck, constructed by Howaldtswerke-Deutsche Werft of Kiel, and sold by Ferrostaal of Essen – all acting together as a West German consortium.
"Nanggala" was laid down on 14 March 1978 and launched on 10 September 1980. It was tested in West German waters before it was handed over to Indonesia on 6 July 1981.
"Nanggala" left West Germany in early August 1981 with 38 crew members under the command of Lieutenant Colonel Armand Aksyah. The submarine was first presented to the public on the 36th anniversary of the Indonesian National Armed Forces on 5 October 1981. Sixteen days later, it was commissioned by the Minister of Defense and Security, General M.Jusuf.
Historical context.
During the 1960s, Indonesia was known as one of the largest Asian naval powers, with 12 Soviet-made Whiskey-class submarines in its fleet. However, by 1981, during the New Order, when "Cakra" and "Nanggala" arrived in Indonesia to reinforce the country's naval defenses, only one of the 12 Whiskey-class submarines had still retained the ability to dive. The Indonesian government had planned to purchase a Type 206A submarine from Germany in the late 1990s, but was unable to do so due to funding issues.
During the beginning of the Reform Era, an embargo on military equipment imposed by the U.S., as well as continuing financial problems experienced as a result of the Asian financial crisis, meant that the Indonesian Navy was unable to procure any additional submarines until 2017. As a result, "Cakra" and "Nanggala" were the only active submarines in the Indonesian Navy between the decommissioning of in 1994 and the commissioning of in 2017.
By 2020, Indonesia had made plans to own and operate eight submarines by 2024.
Service history.
"Nanggala" participated in several naval exercises, including the Cooperation Afloat Readiness and Training exercises in 2002 and 2015. In 2004, the boat participated in the Joint Marine Operations Exercise held in the Indian Ocean, during which it sank the decommissioned . In August 2012, the boat conducted a passing exercise with , accompanied by and a Bölkow-Blohm helicopter.
The submarine conducted a number of intelligence-gathering operations in the waters around Indonesia, including one in the Indian Ocean from April to May 1992, and another around East Timor from August to October 1999, in which the boat tracked the movements of the International Force East Timor as it landed in the region. During May 2005, the submarine was tasked with scouting, infiltrating, and hunting down strategic targets around Ambalat, after Indonesian KRI "Tedong Naga" and Malaysian were involved in a minor collision near the area.
"Nanggala" underwent a refit at Howaldtswerke that was completed in 1989. Roughly two decades later, the boat underwent a full refit for two years in South Korea by Daewoo Shipbuilding &amp; Marine Engineering (DSME) that was completed in January 2012. The refit cost US$63.7 million, replaced much of the submarine's upper structure, and upgraded its weaponry, sonar, radar, combat control and propulsion systems. After the refit, "Nanggala" became capable of firing four torpedoes simultaneously at four different targets and launching anti-ship missiles such as Exocet or Harpoon. Its safe diving depth was increased to , and its top speed was increased from to . In November 2016, the submarine was equipped with an ASELSAN KULAÇ echosounder system.
In 2012, three crew members of the "Nanggala" died in a failed torpedo launch exercise. The submarine was then sent to South Korea for repair.
Sinking.
On 21 April 2021, Air Chief Marshal Hadi Tjahjanto, Commander of the Indonesian National Armed Forces, reported that "Nanggala" was believed to have disappeared in waters about north of Bali. Indonesian Navy spokesperson First Admiral Julius Widjojono stated that "Nanggala" had been conducting a torpedo drill, but failed to report its results as expected. Further details emerged that "Nanggala" had requested permission to dive to fire an SUT torpedo at (20:00 UTC, ). At around 04:00, "Nanggala" should have been flooding its torpedo tubes in preparation for the firing of the torpedo. The last communication with "Nanggala" was at 04:25, when the commanding officer of the training task force would have authorized the firing of torpedo number 8. Chief of Staff of the Indonesian Navy Yudo Margono reported that "Nanggala" had fired a live torpedo and a practice torpedo before contact was lost.
The navy sent a distress call to the International Submarine Escape and Rescue Liaison Office at around 09:37 to report the boat as missing and presumably sunk. The navy stated that it was possible that "Nanggala" experienced a power outage before falling to a depth of . Widjojono stated that "Nanggala" was able to dive to a depth of . The deepest areas of the Bali Sea are over below sea level. It was also reported that the underwater telephone (UWT) of the submarine was defective during the drill, hampering communications between the boat and rescue vessels in the area.
At the time it went missing, "Nanggala" had 53 people on board: 49 crew members, 1 commander, and 3 weapons specialists. The highest-ranking naval officer in the submarine was Colonel Harry Setyawan, the commander of the submarine unit of the 2nd Fleet Command. Subordinates with him were Lieutenant Colonel Heri Oktavian, the commander of the submarine, and Lieutenant Colonel Irfan Suri, an officer from the Weapons Materials and Electronics Service.
At noon on 22 April, Yudo Margono stated that the oxygen reserves on "Nanggala" would be sufficient for the entire crew and passengers for three days after it had submerged, noting that the oxygen would run out on Saturday, 24 April, at 03:00 (20:00 UTC, 23 April). Submarine experts stated that submarines have backup systems that may provide sufficient oxygen for some time depending on the state of the equipment. A crisis center equipped with an ambulance and a mobile hyperbaric chamber was established at the 2nd Fleet Command headquarters in Surabaya. The center was also a source of information for the media and families of the submarine crew members.
Indonesian president Joko Widodo stated that the safety of the crew of "Nanggala" was of top priority and invited everyone to pray for the crew's safety.
Rescue efforts.
On around 07:00, an aerial search revealed traces of an oil spill on the surface of the water near the location where the submarine was believed to have dived. Indonesian Navy deployed three warships—, , and —to search for "Nanggala". Widjojono stated that a team of divers was searching for the boat. "Janes Defence News" also reported that the navy had sent a number of other warships to the area. The governments of Australia, Singapore, and India had responded to Indonesian requests for assistance.
On , the Indonesian Navy reported that an oil slick had been observed at multiple locations. Indonesian frigate "Raden Eddy Martadinata" had detected movement underwater at a speed of but was unable to obtain enough information to identify the contact before it disappeared. Admiral Yudo Margono, Chief Staff of Indonesian Navy, also reported that an Indonesian naval vessel had detected an object that was magnetic at a depth of .
The Indonesian Navy had deployed six additional ships to the area: , , , , and . Yudo Margono also noted on Thursday that three submarines, five airplanes, and 21 warships had been deployed in the search effort. Submarine had also joined the search. , a warship with more powerful sonar equipment, was expected to arrive on . The Republic of Singapore Navy deployed its submarine rescue vessel, and the Royal Malaysian Navy sent its respectively, to the scene. The Indian Navy announced that their deep-submergence rescue vehicle (DSRV) had departed naval facilities at Visakhapatnam, Andhra Pradesh, en route to the search area. U.S. Department of Defense press secretary John Kirby stated that the department was sending airborne assets to assist in the search. These included a Boeing P-8 Poseidon maritime patrol aircraft with one registered as 553.
On 23 April, the Indonesian National Police also sent four police ships equipped with remotely operated vehicles (ROVs) and sonar devices. Fleet Commander Australia, Rear Admiral Mark Hammond announced that HMAS "Ballarat" and HMAS "Sirius" would join the search operation. Other nations, including Germany, France, Russia, Turkey, and Thailand, offered assistance.
Discovery.
On 24 April 2021, the Indonesian Navy announced the finding of debris, including a part associated with torpedo tubes, a coolant pipe insulator, a bottle of periscope grease, and prayer rugs. Because the debris was found within of the point of last contact and no other vessels were believed to be in the area, the debris was believed to have come from the submarine, and "Nanggala" was declared sunk. Yudo Margono stated that a sonar scan had shown the submarine at a depth of , and its crush depth was presumed to be . Due to the maximum operational depth limitation of of "Rigel"'s two underwater ROVs, "Rigel" was unable to launch them and was assisted by the submarine rescue ship MV "Swift Rescue" of the Republic of Singapore Navy, which launched its depth-capable drone and located and made visual contact with "Nanggala" at 09:04.
On 25 April 2021, the Indonesian Navy confirmed that the Nanggala had imploded and that all 53 personnel on board were lost. Underwater scans identified parts of the submarine, including the rudder, diving plane, anchor, and external parts of the pressure hull, as well as items such as an MK11 submarine escape suit. 
The ROV Super Spartan from "MV Swift Rescue" of the Singapore Navy first made visual contact with the wreck and determined that the submarine had split into three parts. Using a multibeam echosounder, KRI "Rigel" confirmed the final position of "Nanggala" at a depth of at the coordinates , roughly from where "Nanggala" had dived.
Analysis.
Cause.
The Navy said "Nanggala" might have had a power outage. The boat had experienced a power outage before because of a blown electrical fuse, but the boat successfully recovered after the ship executed an emergency main ballast tank blow. After the finding of debris from "Nanggala", Yudo Margono said the submarine might have cracked instead of exploded, as an explosion would have been detected by sonar.
Indonesian legislator and retired Major General Tubagus Hasanuddin suspected the refit, performed by the South Korean firm DSME in 2012, may not have been performed properly. He said that