What Happened to the KRI Nanggala-402?


Chapter 1: Maze

The day before the KRI Nanggala-402 went missing in waters off the coast of Bali, the submarine had been a hive of activity.

“It was undergoing maintenance late into the night,” Aura Aulia, the 18-year-old daughter of Second Lieutenant Munawir, told Hukum. “So late that the crew had to work overtime.”

A few days before its departure to the Bali Strait on 21 April, where it was to conduct live fire torpedo training exercises, the submarine had undertaken similar exercises in the Natuna Sea to the south of the Riau Islands, according to Aulia.

It is not clear if the submarine had suffered a technical or mechanical malfunction that required the crew to work on the 44-year-old vessel until well after dark, or whether it had been undergoing standard maintenance.

“I don't know if there was a problem in Natuna,” said Aulia. “Getting information has been like walking through a maze.”

Yet the lack of clarity surrounding what happened to the KRI Nanggala-402 has only fuelled speculation ever since the submarine was found broken into three pieces on the seabed on 25 April.

All 53 crewmen perished when the KRI Nanggala-402 was lost, and recovery operations have yet to locate their bodies, which are thought to be submerged in a mud crater 10 metres deep along with the main section of the vessel. 

Chapter 2: Secrets

No one can really say for sure what happens when submarines sink. 

The causes can be many, and both logistics and protocol can make investigations scarce. Necessary secrecy enshrouds these vessels and all who sail in them. The US Navy calls submarine work the “Silent Service”.

When a letter was discovered on the body of one of the seamen of the Russian submarine Kursk, who had initially survived after the vessel sank in 2000, swathes were redacted for fear of revealing operating procedures and other state secrets.

“The real danger on a submarine is not a blackout, but water getting into the batteries,” one expert told Hukum.

In 2017, the Argentine submarine, the ARA San Juan, sank after water leaked into its snorkel, the ventilation system and a battery connection tray, causing the batteries to short circuit and sparking the “beginning of a fire, or smoke without flame.”

While sailors may fear water, they also fear fire and the possible burns or smoke inhalation that come with it. More likely than not however, fire fighting equipment and training drills will mean that the flames will be extinguished before they cause any loss of life directly. Indirectly, fire can trigger a deadly chain of events such as a massive explosion that in turn rips a hole in the body of the boat.

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If a sailor survives an initial fire and subsequent explosion, they will then have to contend with water rushing inside their stricken vessel.

While immediate drowning is possible, seawater gushing into a submarine at massive pressure also causes adiabatic heating—producing a dense mist that leads to water spray asphyxiation as sailors suffocate on the droplets.

As a submarine sinks to the seabed and descends below its maximum depth, the boat and its crew will be crushed from both the inside and out, and nitrogen narcosis or the “Martini effect”—a phenomenon that usually affects divers and causes drunkenness and euphoria—is also likely to begin.  

“Most likely, there will be bleeding from the eyes, nose, ears and mouth,” an Indonesian Naval expert told Hukum. “You will definitely faint before you are crushed. It’s impossible to survive.”

Even if crewmen do somehow manage to withstand the initial cataclysmic event that sinks a submarine, they will still have to contend with the aftermath.

When the Kursk suffered an explosion that killed most of the 118 men aboard immediately, 23 remained alive according to a water stained letter found on Lieutenant Captain Dmitri Kolesnikov, who was perhaps alive for several days while trapped in an air pocket in the stern of the boat.

“I am writing blind,” said part of the letter, written by Kolesnikov using the glow of his wristwatch in the darkness of the blacked out submarine.

Even now, it is unclear if the 23 Russian seamen eventually died of drowning, hypothermia, lack of oxygen or crushing. 

Chapter 3: Logic

Uncertainty may also be the fate of the KRI Nanggala-402, and conspiracy theories haunt the stricken ship now and perhaps forever: that it was torpedoed; over capacity; attacked by a kraken-like creature; sunk because of black magic; impaled on a coral reef.

When the boat first set sail on 21 April, it had four more people aboard than usual, leading to speculation that it had been too heavy to take to the seas safely.

“Before balancing, the boat load is always checked and if it’s found to be over capacity, of course the submarine will not set sail,” said former Rear Admiral Frans Wuwung (74) who headed the Engine Room of the KRI Nanggala-402 from 1981 to 1985.

The submarine had also only brought three torpedoes with it instead of the usual eight. 

“One torpedo weighs 1 ton. So if you subtract five torpedoes, then you have lost five tons of weight. Do four people weigh more than five tons? I don’t think so,” said Wuwung.

Rumours of foul play in particular have also plagued the boat since it disappeared, in part following a statement released by the Indonesian Navy that noted that the submarine had sent out a “combat” (tempur) signal before losing contact.

“We can only speculate, but perhaps there was a torpedo or weapon explosion or a collision with an underwater vessel like a Chinese submarine,” said one British Navy expert when asked for possible theories about what might have transpired.

Yet others disagree.

“The combat signal doesn’t mean that they met an enemy underwater,” said Wuwung. “That was probably just to test that all the features on the submarine were running properly.” 

In an internal report, the Indonesian Navy floated the theory that the submarine suffered a blackout which caused it to plunge to the seafloor and break apart in the process—an assessment which prompted rumours of a cover-up by the authorities, but one which by far makes the most sense.

When a submarine is first constructed on dry land, it is made not in a single piece, but in three parts—front, centre and stern—which are then welded together and connected to become one complete ship.

It is these areas of the weld that are most susceptible to breakage and, as the submarine was found at a depth of over 840 metres (well below its maximum crush depth of 300 metres), its rapid descent would have caused immense pressure that “peeled the vessel apart at the seams”, one expert told Hukum.

"The fact that the submarine was found in three pieces also counters the narrative that the ship was shot at or detonated by another party,” added Wuwung. “If that had happened, there would obviously be a hole in the ship.”

“It’s just plain logic.”


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Additional reporting: Reno Surya

Photo credit: Ivan Darski


Water got in missing submarine’s snorkel and caused short circuit, Argentine navy says - SCMP

Soaked letter tells last hours of ‘Kursk' crew - Irish Times

Adiabatic Process - Britannica

Requirements to Serve on a Submarine - the Balance Careers

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