The ruins of GiantThe ship’s modified carbon fiber hull was found to have separated into three separate layers, National Transportation Safety Board engineer Donald Kramer told the Coast Guard. hearing into the deadly explosion of the OceanGate submarine in 2023.
While Kramer did not offer an opinion on what caused the hull to separate into separate layers, he did testify to numerous hull-related issues, dating back to production in 2020.
Using carbon fiber samples saved from construction, as well as dozens of pieces recovered from the seabed, the NTSB has come up with the most complete picture to date of the experimental nature of the Gianthull
After GiantThe first vessel’s hull was found to have cracks and delamination after a deep dive in 2019, and OceanGate switched manufacturers for a replacement.
The new manufacturer, Electroimpact, used a multi-stage process to wrap and cure the five-inch-thick shell into five separate layers. Each layer is baked at high temperatures and pressures before being flattened, a sheet of adhesive is added, and another layer is built on top. The idea behind this multi-stage process is to reduce wrinkles in the final shell, which the company believes has plagued test models. not reaching their design depth.
However, Kramer testified that the NTSB found some irregularities in the new hull samples. There was wrinkling in four of the five layers, and the wrinkles got worse from layer to layer. The NTSB also found that some layers had porosity—voids in the plastic material—that was four times greater than specified in the design. The NTSB also noted gaps between the five layers.
“Impairments such as voids, surface blisters and porosity can weaken carbon fiber and under extreme hydrostatic pressure can accelerate hull failure,” Roy Thomas, a materials expert with the U.S. Bureau of Shipping, said at the hearing on Monday.
OceanGate did not conduct any additional testing using the new multi-phase process.
The NTSB was able to recover several pieces of the carbon fiber hull from the seabed, one still attached to one of the submarine’s titanium domes. In a report issued at the same time as Kramer’s testimony, the NTSB noted that there were few, if any, full-thickness pieces of the hull. All visible pieces had split into three layers of shell: the innermost of the five layers, a shell made up of the second and third layers, and another made up of the fourth and fifth layers. Like an onion being peeled, the hull had largely split at the glue between the layers.
The fragments of Giant may have sunk to the bottom of the sea after detonating, as recorded by a remote-controlled device.Photo: Reuters
