NASA disagreed with how OceanGate wanted to invoke the agency ...

A NASA employee testified during a weekslong hearing on the implosion of OceanGate's Titan submersible that the agency had disagreements over the sub maker's press materials mentioning NASA.

Justin Jackson, a materials engineer with NASA, testified Thursday during the U.S. Coast Guard's hearing into the June 2023 implosion of the OceanGate submersible, which killed all five passengers while on a deep-sea dive to the Titanic shipwreck.

Jackson said OceanGate's then-chief operating officer initially reached out to NASA to manufacture a composite hull and they signed an agreement under the Reimbursable Space Act Agreement in early 2020.

NASA had an interest in the fabrication of a thick composite hull for "exploration applications," though the COVID-19 pandemic prevented the agency from manufacturing or testing one for OceanGate, he said.

NASA did provide remote consultation to OceanGate on a one-third scale mockup, including a plan to try to fabricate a thick-walled hull, Jackson said. Conversations with the company ended in 2021, shortly after a disagreement over press materials invoking NASA, he said.

Asked by investigators why NASA refused OceanGate's request to use its name in a media release, Jackson said, “It was the language they were using was getting too close to us endorsing. So it was, our folks had some heartburn with the endorsement level of it."

As previously reported by ABC News, in some public statements, OceanGate suggested that its Titan submersible was designed and engineered with the assistance of entities such as NASA and Boeing. In statements to ABC News in the wake of the catastrophic implosion of the Titan, each entity described its role in the Titan submersible, or lack thereof, as more limited than sometimes stated by OceanGate.

Investigators also heard from a witness with Boeing regarding the company's past dealings with OceanGate over a carbon-fiber hull during the hearing on Thursday.

Boeing entered an agreement with OceanGate in 2013 to conduct a preliminary feasibility study for a concept vessel, the Coast Guard said. Boeing was asked whether it was feasible to "have a design with a certain amount of buoyancy and safety factor," Mark Negley, a materials and process engineer with Boeing, said during his testimony.

Negley said Boeing did not manufacture any parts for OceanGate or give advice on the type of carbon fiber to purchase and was not involved in materials testing.

Negley said Boeing did not work with OceanGate on subsequent requests from the submersible maker.

"I don't know [why] exactly, you know, I think maybe we were too expensive," he said.

The Titan submersible made multiple dives to the Titanic wreckage, located in international waters, before it catastrophically imploded on June 18, 2023. The experimental Titan sub was not classified by any agencies that regulate safety and was not registered as a U.S. vessel.

Lt. Cmdr. Jonathan Duffett with the U.S. Coast Guard Office of Commercial Vessel Compliance testified Thursday that the Titan seemed to meet the requirements for it to be registered as a U.S. vessel.

Because the Titan carried paying customers -- what OceanGrate referred to as "mission specialists" -- he said the Titan would have been considered a small passenger vessel, which would have made it subject to Coast Guard inspection.

John Winters, a marine inspector with the U.S. Coast Guard Sector Puget Sound, based in Seattle, testified Thursday on his experience working with Oceangate in 2010 on the Antipodes, a submersible OceanGate had acquired.

Winters said Oceangate CEO and co-founder Stockton Rush expressed frustrations with a small passenger vessel regulation that prevented the vessels from diving more than 150 feet.

"He did express, on multiple occasions, that regulations were stifling his innovation process," Winters said.

He said OceanGate changed to an oceanographic research vessel designation, which does not have that depth restriction, and the Antipodes never received a small passenger certificate of inspection.

Winters said that there was "never an attempt by OceanGate to circumvent" or not comply with regulations in the time he interacted with the company in 2010.

Winters said he did not provide Rush with guidance on regulations for Titan.

OceanGate suspended all exploration and commercial operations after the deadly implosion, which killed five people, including Rush.

The hearing on the incident began on Sept. 17 and is scheduled to run through Friday in North Charleston, South Carolina, though the proceedings might be impacted by Hurricane Helene, the Coast Guard said.

The main purpose of the hearing is to uncover the facts related to the implosion and to make recommendations, the Coast Guard said