A pair of reports by the National Transportation Safety Board found evidence of imperfections in the carbon-fiber hull that was made for OceanGate’s Titan submersible — plus indications that the hull behaved differently after a loud bang was heard at the end of a dive in mid-2022.
At the time, OceanGate team determined that the loud bang was not a serious problem, but less than a year afterward, the sub and its crew were lost in a catastrophic implosion during a trip to the wreck of the Titanic in the North Atlantic,
Donald Kramer, an senior materials engineer who presented NTSB’s findings today at a Coast Guard hearing in South Carolina, declined to go beyond the data and speculate on whether the imperfections or the bang figured in Titan’s doom. But one leading theory for the sub’s failure suggests that weaknesses in the hull gave way under the extreme pressure of the deep ocean.
The five crew members lost in last year’s tragedy included Stockton Rush, who was the CEO and co-founder of Everett, Wash.-based OceanGate as well as the sub’s pilot; veteran Titanic explorer P.H. Nargeolet; British aviation executive and adventurer Hamish Harding; and Pakistani-born business executive Shahzada Dawood and his son, Suleman.
The NTSB based its newly published reports on a study of debris that was brought up from the seafloor, plus an examination of carbon-fiber samples that were cut off the ends of OceanGate’s hulls.
Two hulls were fabricated: The first one was used for test dives in 2018 and 2019 in the Bahamas, but was scrapped when a crack was discovered in the 5-inch-thick carbon-fiber composite. The second one was used for Titanic dives in 2021, 2022 and 2023. In addition, the NTSB studied samples from subscale test hulls.
Kramer said the surplus pieces from Titan’s second hull had “several anomalies within the composite and the adhesive joints, including waviness, wrinkles, porosity and voids.” Bulges in the hull were ground smooth at 1-inch intervals during the process of laying down the carbon-fiber strands, according to the reports.
Debris from the sub’s hull showed delamination of the composite, primarily at places between the 1-inch layers.
In addition to looking at the carbon-fiber hull samples, the NTSB analyzed data captured by acoustic sensors and strain gauge sensors mounted in the hull. OceanGate used the data from those sensors in a real-time monitoring system that it had hoped would provide advance warning of problems with the hull.
The NTSB focused on data from a notable dive to the Titanic in July 2022. At the end of that dive, the crew heard a loud bang resonating through the hull. One of the mission specialists who paid to participate in the dive, Fred Hagen, said during earlier testimony that “you would have to be brain-dead not to be somewhat concerned” about the noise.
According to other testimony, reports of the bang also stirred concern among other OceanGate team members at the time — including Phil Brooks, who was the director of engineering, and tech contractor Antonella Wilby.
Hagen said OceanGate determined that “the body of the fuselage of the Titan had just jumped in its carriage, so there was no damage.” Brooks said that “seemed like a reasonable explanation” at the time. But based on its study of the sensor data, the NTSB said strain gauges placed on a specific section of the hull showed significant differences in readings taken before and after the bang occurred.
“It means that there is a sudden change in both the longitudinal and the hoop strain at this particular location of the hull. … There’s a change in the strain in the hull that is occurring at this location that is not occurring at other locations,” Kramer said.
There were also unusual spikes in acoustic activity during the first dive that took place after the bang was heard, but the second and third dives afterward “show a trend of the hull becoming quieter,” Kramer said.
Kramer emphasized that the NTSB was continuing its tests and its analysis of the results. He dodged a question relating to causal connections between Titan’s implosion and the issues that were detailed in the agency’s reports. “That is still subject to our own internal analysis at this point,” Kramer said.
Eventually, the NTSB and the Coast Guard will produce separate reports delving into the causes of the Titan tragedy, and providing recommendations for regulatory changes aimed at heading off such tragedies in the future.
Other highlights from the hearing
William Kohnen, CEO and founder of Hydrospace Group, said the viewport that his company provided for OceanGate’s first hull was rated for use at a maximum depth of 2,150 feet (650 meters), but not for the Titanic depth of 12,600 feet (3,840 meters). He said he pleaded with the OceanGate team to get a better window. “We figured they could buy it in any number of places, and in the end, they did. They just didn’t buy it from us,” he said.
The investigative board’s chair, Jason Neubauer, said the viewport for the second hull was purchased in 2020 from a German company called Heinz Fritz.
Kohnen was the author of a controversial draft letter that questioned OceanGate’s practices in 2018. The letter was supposed to have been sent to OceanGate CEO Stockton Rush by the Marine Technology Society, but the MTS board told Kohnen it couldn’t be issued on the society’s behalf.
“It was considered outside the bylaws of the nonprofit organization,” Kohnen recalled. “I had to respect that, and I said OK, and I filed the letter. Was a letter received? That I can confirm, it was, because somewhere down in all the electronic letters that were circulated, one of them got passed on to OceanGate, and Stockton got the letter. And Stockton’s first reaction was to call me.”
Kohnen said Rush argued against his suggestion that OceanGate should get the Titan sub certified by outside experts. “It was the usual response that it takes too long, it’s too expensive, and they don’t know about this technology,” he recalled.
“I don’t think many people ever told Stockton ‘no,'” Kohnen said. “I don’t think he understood that concept very much.”
Bart Kemper, principal engineer at Kemper Engineering Services, said the root cause of the Titan sub implosion was still “indeterminate” — but he outlined potential failure modes involving the carbon-fiber hull, the bond between the hull and the sub’s titanium end caps, and the sub’s acrylic viewport.
In answer to a question that referred back to Kramer’s testimony, Kemper said that delamination in a section of the carbon-fiber composite hull could cause a shift in strain readings. He said he would not have gone ahead with further dives if a significant change in strain was detected in the hull. “I would have stopped operations and assessed,” Kemper said.
Kemper also criticized OceanGate’s engineering approach for not doing a life-cycle analysis of the hull. “This is just wrong,” he said. “It’s flat wrong.”
He said authorities should limit the crew of an experimental craft to an operator and assistant, with no passengers or cargo. He recommended that submersibles should be required to have a minimum level of navigation aids, emergency gear and a standardized lifting point for extraction by a remotely operated vehicle. Kemper said the Coast Guard and the submersible community should figure out “a reasonable minimum standard to require, and why and how to do it.”
Previously:
- Submarine expert recounts how a Titan trip unnerved him
- Former top engineer says cost concerns shortchanged safety
- OceanGate client recalls a tricky Titanic tangle
- Titanic traveler makes a tearful plea for citizen science
- Videos show the shattered remains of Titan sub
- OceanGate whistleblower traces the roots of his concerns
- Hearing reveals the last words sent by Titan’s crew
- A new chapter in the OceanGate probe, but not the end