Article written by a guy in the company who sold to Ocean Gate
the composite material to build the sub. If the dead crew had read
and believed what was said in the article then they might have
been scammed.
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Composite submersibles: Under pressure in deep, deep waters
Published 5/10/2017
Jeff Sloan
Even as massive amounts of money, energy and attention are being paid to the development of privately funded launch and delivery systems for space exploration — and the application of composites therein — an environment much closer to home is, despite its proximity, as remote and difficult in its own way to access and study.
At an average depth of about 3,810m, with a maximum depth, at Challenger Deep in the Pacific, of 10,916m, the world’s oceans offer a formidable challenge to explorers. Scientists, marine biologists or oil and gas engineers and others who would dive to such depths require a vessel that can withstand deepsea water pressure that, at the deepest point (almost 11,000m), is a massive 5,551 psi or 378 atmospheres.
Such vessels, called submersibles, offer capacity for three to five occupants, can explore depths from 1,200m to 6,500m, provide a viewing porthole or portholes, and are equipped with lighting systems and cameras. Conventional submersibles feature steel, aluminum or titanium hulls. Metallic hulls, however, because they are not buoyant in designs for depths of more than 2,000m, present challenges when it comes to managing ballast for ascent and descent. In particular, metal-hulled craft require the use of syntactic foam attached to the outside of the craft to achieve neutral buoyancy.
In 2014, submersibles manufacturer OceanGate Inc. (Seattle, WA, US) was coming off the successful launch of Cyclops 1, its steel-hulled, five-person craft, rated for underwater exploration to a depth of 500m. The company was set to embark on development of Cyclops 2, a five-person research-class submersible, designed for a maximum depth of 4,000m.
OceanGate CEO Stockton Rush says the company had been evaluating the potential of using a carbon fiber composite hull since 2010, primarily because it permits creation of a pressure vessel that is naturally buoyant and, therefore, would enable OceanGate to forgo the use — and the significant expense — of syntactic foam on its exterior. So, for Cyclops 2 OceanGate decided to avoid the metallic hull altogether
and began a search for a manufacturer that could help it develop a composite hull.
It is believed that the first time carbon fiber composites were applied to the hull of a deep-diving, manned submersible was for the one-person DeepFlight Challenger, commissioned by adventurist Steve Fossett in 2000 for a dive to the bottom of Challenger Deep (see Deepsea submersible incorporates composite pressure capsule). Designed and built by famed marine engineer and submersible designer Graham Hawkes, a principal at the time of Hawkes Ocean Technologies (Point Richmond, CA, US), it featured a cylindrical carbon fiber/epoxy composite hull with 6-inch-thick walls. It was nearing completion in 2007 when Fossett was killed in a light-aircraft crash. The Challenger was subsequently sold, and has yet to be fully tested or deployed in a deepsea dive. Spencer Composites Inc. (Sacramento, CA, US), a designer/manufacturer of composite parts and structures for a variety of end-markets, had designed and fabricated the DeepFlight Challenger’s hull.
“I knew of the submersible Graham Hawkes designed for Steve Fossett,” says OceanGate’s Rush. “And I knew Spencer Composites manufactured that cylinder.”
Spencer Composites’ president Brian Spencer signed a contract with OceanGate for the Cyclops 2 hull in early January 2017 and was presented with very basic — but challenging — performance parameters: Length, 2,540 mm; outside diameter, 1,676 mm; service pressure, 6,600 psi; pressure safety factor, 2.25. “They basically said, ‘This is the pressure we have to meet, this is the factor of safety, this is the basic envelope. Go design and build it,’” Spencer reports. And he was given six weeks in which to do it.
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Cyclops 2 will enter the water for the first time in November of this year, followed by a deep-dive test in early 2018. If that goes well, its first mission, in May 2018 in the North Atlantic, will be a descent to the wreckage of the Titanic, which sits 3,688m under the surface. The goal? Capture high-definition still and video images of the Titanic, and gather sonar and laser measurements of the ship and the ship’s debris.
After the Titanic mission, Cyclops 2 will be off on a variety of other missions that, says Rush, will keep the craft busy for the rest of 2018. OceanGate, he says, will build at least four Cyclops 2 submersibles, and as many as 20, depending on demand. Rush says Cyclops 3, 4 and 5 are already on the drawing board, will target depths of 6,000m and likely will feature carbon fiber composite hulls.
Manned deepsea exploration calls for a highly engineered composites solution that saves weight and preserves life — at 6,500-psi service pressure.
www.compositesworld.com
