After five days of fierce searches, rescuers found the submarine on the seabed at a depth of 838 m. The ship split into several parts, killing all 53 crew members, writes news.com.au.
After the rescuers were able to find items from the submarine, it became clear that the worst had happened – the ship had sunk. There were many questions about how the crew-ready ship could break through so quickly.
How did KRI Nanggala 402 disappear?
Indonesian military officials now suspect the submarine was hit by a single internal wave. It is a powerful force generated when the mass of water is expelled through a relatively smaller passage.
Officials say the water density off the coast of Bali and the nearby Lombok Strait seems to have caused a “tremendous moment of strength.” The momentum generated was enough to suck the submarine down in a matter of moments, writes Nikkei Asia.
What are inner waves?
Internal (deep) single waves are powerful and hard-to-detect currents that pose a major threat to submarines and can cause much inconvenience to offshore oil rigs.
Satellite images captured by NASA in 2016 show a deep single wave forming near the Lombok Strait.
The space agency explained that internal waves occur when “interactions between layers are disrupted, such as when a tidal wave falls on the rough ocean floor, due to ridges or other obstacles.”
Because the Lombok Strait is a relatively narrow gap between the Pacific and Indian Oceans, the currents develop a “complex rhythm,” but “tend to merge about every 14 days and create an extremely strong tidal wave.”
The combination of ocean topography, strong currents, and water moving between the two oceans makes this place famous for the emerging sharp deep waves.
The waves are difficult to capture, they cause only slight ripples on the ocean surface, although they can actually add underwater, writes news.com.au.
“They couldn’t do anything”
Navy Chief of Staff Iwan Isnurwanto said the images, which captured a suspected single deep wave at the scene of the submarine’s disappearance, were taken from the Japanese weather satellite Himawari 8.
“They couldn’t do anything, they didn’t have time to do something if the submarine was plunged by such a wave,” Isnurwanto explained at a press conference at the naval headquarters in Jakarta.
“The ship probably turned at an angle (down), so all the crew members rolled down. We will continue the investigation, but this version explains everything best, “Isnurwanto added.
Other theories explaining why the submarine sank
Even before the sinking of KRI Nanggala, there were reports that the ship’s power supply could be disrupted.
Such a theory arose from a preliminary analysis conducted by the Naval Information Center. It has been speculated that a submarine may be at risk of failure of the power supply system during static immersion. The analysis warns that a submarine may sink at a depth of 600-700 m.
Therefore, in order to prevent this, it was proposed to install an emergency button on board.
Former General Tubagus Hasanuddin also speculated that the ship’s 2012 refurbishment and refurbishment in South Korea may not have been done properly.
He explained that in the same year that the refurbishment of the ship was completed, an accident involving the lives of three people occurred during a test of the ship’s torpedo launch system.
“I guess the result of this renovation is the misalignment or nuances of construction that drowned the KRI Nanggala-402. It’s a big disaster, “Hasanuddin said.
The ship was built in 1978 and last renovated in 2012, increasing the depth to 250 m.
A search of the area shortly after the connection with KRI Nanggala was severed revealed an oil spill and several items, including prayer mats and pieces of the ship’s torpedo tube. These findings caused great concern for the people on board.
The submarine is thought to have ruptured due to water pressure, with some items missing at the time.
It was scheduled that oxygen on board should be sufficient by three o’clock in the morning on Sunday, April 24th.
On Sunday morning, search vessels detected magnetic signals from the submarine. It was soon confirmed that the ship was on the seabed.
Indonesian President Yoko Widodo said the country was shaken by the first submarine disaster and that the government “expresses its deepest condolences, especially to the crew members’ relatives”.
The discovery of the KRI Nanggala 402 marked the end of a panic-stricken five-day search involving other countries, including the United States and Australia.
MV Swift Rescue, one of the lifeboats, is capable of pulling people out of the submarine if there are survivors, the Times News Service reported.
This vessel can lift up to 17 people to the surface and has decompression chambers and a medical center.
The KRI Nanggala 402 was one of five submarines in the Indonesian fleet.
The Chinese navy is preparing to help
Chinese naval vessels have arrived off the coast of the island of Bali to help lift an Indonesian submarine that sank last month with 53 crew members, the Indonesian navy said on Tuesday in preparation for a deep-sea operation.
The aid came from the leaving of island states’ waters by ships from other foreign countries, such as Australia, Singapore and Malaysia, which helped the Indonesian authorities find the submarine affected by the disaster.
The KRI Nanggala 402, one of Indonesia’s five submarines, disappeared in April in preparation for a torpedo launching exercise.
An underwater rescue machine provided by neighboring Singapore provided images confirming that the ship, built in Germany, was lying on the seabed at a depth of more than 800 m split into three parts. Upon receiving such data, any hopes of finding live crew members were dashed.
Two Chinese lifeboats were on duty off the coast of Bali, and a third was due to arrive later on Tuesday, the Indonesian navy said, adding that Chinese naval officials in Bali were helping investigate the data collected on the submarine.
All three lifeboats are capable of carrying out work at depths of up to 4,500 m.
According to the Indonesian navy, the Beijing ambassador to the country offered assistance to Defense Minister Prabowo Subianto.
“The Indonesian government welcomes this proposal,” the cabinet said in a statement issued on Tuesday.
The rescue operations will be joined by the vessel of the Indonesian Oil and Gas Surveillance Working Group, SKK Migas, which is used for drilling operations and has a crane capacity of 1,200 tons.
Last week, the Indonesian navy said it was considering submarine lifting measures such as powerful magnets and pontoons. In addition, it is planned to use an underwater robot.
The Indonesian military has not yet officially explained how the submarine was built in Germany and handed over to the Southeast Asian state in 1981.
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