Preliminarily it sounds like maybe the inner torpedo tube door wasn’t closed and/or secured when they flooded the tube and opened the outer tube door.
Interesting possibility!
Reading the article, it doesn’t say what thpe of debris was recovered. I wonder if that might yield clues to what happened?
Wasn’t that Russian leviathan, the Kursk, lost when a torpedo malfunctioned and exploded? It sank in water shallower than its length!
IIRC, in Herbert Werner's book about his U-Boat experiences, "Iron Coffins", they discovered by accident, why some boats disappeared without a trace.
They left the outer doors of their torpedo tubes open while in port and when bombs were dropped, the concussion blew open the inner doors. He figured some boats had done that after an attack and the following depth charge attacks did the same.
Here's a gCaptain article that gives some background:
Missing Indonesian Submarine Was Old And Overloaded
The Indonesian navy’s missing submarine may have been too old and overloaded when it embarked on a military exercise on Wednesday, according to a defense analyst. The KRI Nanggala-402 that disappeared in waters off Bali island was carrying 53 crew during training, Indonesia’s defense ministry said. A submarine of that class has a maximum capacity of 40, according to Ridzwan Rahmat, principal defense analyst at Janes.
Its age does not help either. At over 40 years, the Cold War-era submarine is among the world’s oldest in service today and was not built to withstand pressure beyond 230 meters (754 feet) deep, Ridzwan said.
This adds greater urgency for rescuers who are racing against the clock to find the missing submarine and its crew. Air in the KRI Nanggala-402 is estimated to be breathable only until 3 a.m. on Saturday, Jakarta time, after which oxygen is insufficient, according to navy Commander Admiral Yudo Margono.
Survival rates are low for victims of submarine accidents in waters deeper than 200 meters. While people can self-evacuate to the surface in shallower waters less than 50 meters, pressure at greater depths is strong enough to crush steel hulls and lungs, according to salvage experts. About 118 crew died in 2000 when the Russian nuclear stealth machine Kursk exploded then came to rest on the ocean floor off Murmansk. About 44 crew perished when the aging Argentinian submarine ARA San Juan went missing in 2017. Navies in Singapore and Malaysia have sent ships equipped with deep submergence rescue vehicles to aid in the search.
The U.S.’s Poseidon airship is also en-route from the Philippines, while two Australian vessels have arrived on-site, Indonesia’s army spokesperson Djawara Whimbo said on Friday.
Meanwhile, Indonesia has deployed more than 20 vessels to scour the waters and is conducting aerial surveillance after an oil spill was found around the submarine’s starting dive position.
“Hopefully, this can be found soon while there is still spare oxygen,” the navy’s Margono said in a Thursday statement.
Refurbished Submarine
Questions are being raised as Indonesian authorities try to shed light on the Southeast Asian nation’s first submarine disappearance. According to the Janes analyst, the incident could have been avoided if the vessel wasn’t overloaded or kept in service for so long.
The typical life cycle for a naval submarine is only about 30 to 35 years, Ridzwan said. KRI Nanggala-402 was built in Germany in 1977 and joined the ranks of the Indonesian navy in 1981. It was supposed to be decommissioned but because of limited funding, the government decided to upgrade it instead in South Korea, he said.
“It was an accident waiting to happen,” Ridzwan said.
Rescuers will likely have to break the hull or conning tower as the submarine doesn’t have a rescue seat, he said. However, hopes of survival are growing dim. “It’s possible people don’t survive,” he said.
–With assistance from Claire Jiao.
Sounds like Ice Station Zebra.