Teams Are Racing to Find a Submarine Before the Crew Runs Out of Oxygen

The clock is ticking.
Brad Bergan
The Indonesian submarine KRI Nanggala-402 at sea.US Navy / Wikimedia


Indonesian officials said the vessel would exhaust its oxygen supply today between 3 and 4 PM EDT (April 23, 2021). While the search has yet to be called off, it is with deep regret that we observe the passing of this deadline. With it comes the dwindling likelihood that the submarine, along with its crew of 53, survived. Please see our most recent coverage with the latest information. Our original coverage follows in full. 


The world is watching as teams race to locate and determine the fate of an Indonesian submarine that vanished along with 53 crew members — and the clock is ticking as the vessel will run out of oxygen on Saturday, according to a statement from a military official reported in CNN.

Chief of Staff Admiral Yudo Margono of the Indonesian Navy said the submarine carries enough oxygen for 72 hours in total, based on calculations of when the submarine dropped all contact amid a Wednesday military exercise. A German-built Nanggala-402, the vessel requested permission to dive at 3:00 AM local time (3:00 PM EDT) on Wednesday before it lost contact, according to authorities.

An oil spill was spotted where the Indonesian submarine dived

Margono said the submarine had just fired two torpedoes — one capable of arming and detonating — in a training exercise in the depths of the Bali Strait, which stretches between the Bali and Java islands. Before the war games and subsequent crisis, Margono said the KRI Nanggala-402 and its entire crew were well prepared. It had docked for maintenance in 2020 in Surabaya, a port city on Java.

The Indonesian military thinks an oil spill seen via aerial surveillance near the dive point may have leaked from the submarine. Margono added that the Navy also found an object at a depth of 164 to 328 ft (50 to 100 m) with magnetic properties — which means it probably came from something artificial. Like a submarine.

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For Margono, there are two possible explanations for the oil spill seen on the sea surface: either the submarine's tank is leaking from an excessively deep dive, or the submarine released its onboard fluid to assist in resurfacing efforts. The Indonesian Navy spokesperson First Admiral Julius Widjojono said the vessel can dive down to roughly 1,640 ft (500 m) below sea level.

But, worryingly, authorities suspect the submarine dove 328 to 656 ft (100 to 200 m) deeper than that.

How to surface a submarine with buoyancy

Ships stay afloat because the water they displace is equal to the weight of the submerged part of the ship — creating a buoyant force that works in the opposite direction of gravity. For any submerged submarine to surface, it needs to weigh less than the water its body displaces.

When both weights are equal, the vessel remains more or less at the same depth. But to change its depth, the submarine fills ballast or trim tanks with water or air to sink or rise, respectively. Submarines retain a supply of compressed air in air flasks for life support and for the ballast tanks. It can also use short and movable "wings" dubbed hydroplanes on the rear of the ship that can control the angle of dive or ascent.

We don't know how deep the submarine is, but to surface, it needs to push compressed air into the ballast tanks, forcing the water out of the submarine until its general density is less than the surrounding water — recreating the positive buoyancy surface ships employ. The submarine can then angle its hydroplanes so water moves upward over the rear, forcing it down and angling the entire vessel upward.

During an emergency, the ballast tanks may be rapidly filled with high-pressure air to "launch" the submarine to the surface at incredibly rapid speeds.

As of writing, two days remain for the 1,395-ton Nanggala-402 submarine to surface, and for the crew to be rescued. Depending on its depth, rescue craft might also attempt to dock and evacuate the crew, but authorities would first have to locate the vessel. And while the Bali Strait only has an average depth of 200 ft — the neighboring Bali Sea has a maximum depth of 5,217 ft (1,590 m), which is 3,577 ft deeper than the Indonesian submarine's maximum depth of 1,640 ft (500 m).

Our best hopes go out for the sailors and the search teams at work.