What caused the ‘catastrophic implosion’ that killed 5 on Titanic tourist sub?

NEW YORK — The tragic news that five people died when a submersible imploded while on a dive to explore the Titanic wreck site is sparking questions and will be the focus of an investigation.

“I know that there’s also a lot of questions about how, why and when did this happen,” U.S. Coast Guard Rear Adm. John W. Mauger said. “Those are questions that we will collect as much information as we can on now.”

The sub was reported missing after it lost contact with the Canadian research vessel Polar Prince about 1 hour and 45 minutes into its dive Sunday about 900 miles east of Cape Cod, Mass., the Coast Guard said.

There had been earlier concerns about the safety of the vessel.

What do we know about the implosion?

Mauger said at a news conference Thursday that it is too early to tell at what point in its dive the vessel imploded, and added that listening equipment used throughout the search did not detect any type of catastrophic event.

However, a U.S. government official who is familiar with the incident but not authorized to speak to the media and requested anonymity told The Times that technology designed to listen to the ocean for movement captured the sound of the submersible imploding around the time communications were lost. That news was first reported by the Wall Street Journal, which noted the sound “anomaly.”

The Journal reported that “the Navy began listening for the Titan almost as soon as the sub lost communications, according to a U.S. defense official. Shortly after the submersible’s disappearance Sunday, the U.S. system detected what it suspected was the sound of an implosion near the debris site discovered Thursday and reported its findings to the Coast Guard commander on site, U.S. defense officials said.”

Mauger said Thursday that “the debris is consistent with the catastrophic loss of the pressure chamber.”

A robot submersible from the Canadian vessel Horizon Arctic discovered several major pieces of the 21-foot sub, the Titan, in a debris field on the ocean floor about 1,600 feet from the bow of the Titanic.

What did officials find at the scene?

Paul Hankins, a salvage expert for the Navy, said five major pieces of debris from the Titan were found, including the nose cone, which was outside of the pressure hull. The robot sub also found a large debris field that included the front-end bell of the pressure hull.

“That was the first indication there was a catastrophic event,” he said. A second, smaller debris field contained the other end of the pressure hull and other wreckage that indicated a total compromise of the vessel.

Officials said the debris was in an area away from the Titanic wreckage in a patch of smooth ocean floor and that there were no signs the vessel collided with the historic ship. The size of the debris field and the vessel’s last known location are consistent with an “implosion in the water column,” officials said.

How did the search proceed?

Since the sub went missing on Sunday, crews using specialized equipment worked around the clock to find the sub, which was designed to have an initial air supply of 96 hours. Officials also said it had only “limited rations” of food and water.

The search grew to 10,000 square miles, roughly the size of Massachusetts, and went 2½ miles deep. Through the days-long effort, officials maintained optimism that they were conducting a search-and-rescue effort and not a recovery mission.

Assets launched in the search included American and Canadian aerial support vessels that scanned the ocean’s surface and subsurface using sonobuoys; U.S. Navy divers; coast guard and research vessels from Canada, France and Norway, some of which were equipped with highly specialized remote-operated vehicles that could work on the ocean’s floor; and assistance from commercial vessels.

A moment of promise came Tuesday when the Coast Guard confirmed reports that banging noises were detected on the seafloor by sonobuoys dropped from Canadian aircraft. Although officials said the origins of the sounds were unclear, they became the target of search efforts.

At the news conference announcing the loss of the Titan on Thursday, Mauger said the underwater noises, which were also observed Wednesday, did not appear to be connected to the sub’s location. The implosion would generate “significant broadband sound” that would have been picked up by the sonobuoys, he said.