Explorers in earlier centuries traveled the world in modes of transportation made of wood and metal. Today, however, journeying into the unknown requires vehicles built with more durable materials. When those vehicles include components made from composite materials, they gain the toughness, strength and resiliency necessary for groundbreaking expeditions. Composites are proving their ability to survive the harshest, most challenging environments deep below the ocean surface, at the coldest place on earth and even on another planet.
Exploring the Ocean Depths
Submersible vessels designed for deep sea exploration have to withstand tremendous pressure. At sea level, the air pressure is 14.5 pounds per square inch (psi); at 4,000 meters (about 2.5 miles) below the surface, the deep water exerts a pressure of 5,800 psi. Few vessels can withstand that force, but the Titan, a five-person submersible developed and operated by OceanGate, has traveled safely to that depth several times. The Titan’s strong pressure vessel, made of a CFRP cylindrical hull capped by titanium domes on each end, makes it possible.
OceanGate had used a metal pressure vessel for its earlier submersible, Cyclops 1. Switching to CFRP for Titan provided some important advantages. “Carbon fiber is three times better on a strength-to-buoyancy basis than titanium, and underwater that’s what you care about,” says Stockton Rush, CEO and co-founder of OceanGate. “Strength-to-weight is not the issue, but strength-to-buoyancy is.”
One problem with using carbon fiber was the lack of information about how it would react under deep sea conditions. Most testing on large CFRP pressure vessels, like gas tanks, has focused on tensile loads. OceanGate, however, needed to understand how such vessels would perform at the uniform external pressure they’d encounter undersea.
OceanGate initially worked with Boeing to develop a pressure vessel manufactured using automated fiber placement with prepreg windings. But Boeing’s software, developed to model FAA-certified materials, had to include off-axis plies, and that’s not what OceanGate needed. “In a pressure vessel, there’s no torsional forces, no off-axis; it’s all orthogonal. So if you want to orient your fibers to the loads, you really only need it in the hoop and the axial – around it and longways,” Rush explains.
The company then turned to Spencer Composites, which had previously built a CFRP hull for a project for Steve Fossett, the late aviator/adventurer. “Spencer had done a lot of work, pushing the envelope with the 0/90 degree lay-up, which is what we really wanted,” Rush says. Spencer’s approach – build, test, modify and build again – also appealed to OceanGate.
Spencer was able to produce the carbon fiber shell for the pressure vessel, but an attempt to create carbon fiber end domes wasn’t as successful. “If you’re filament winding the domes, it’s difficult not to have the fibers overlap in a baseball-wound fashion. We tried that and did not get the performance even close to what we had hoped,” says Rush. So the Titan includes the same type of titanium domes found on Cyclops 1.
The team also developed a GFRP insert to fit inside the hull. The titanium end domes and the research and navigation equipment are all attached to this insert so that the CFRP shell won’t be weakened by penetrations into it. Having a removable insert makes it easy to inspect the hull and to change the Titan’s configuration to accommodate five researchers, three researchers or even autonomous operation.
One argument against using composite materials in submersibles has been that they can fail without warning due to a weak point in the carbon fiber or composite structure that shows up only after multiple use cycles. To ensure that doesn’t happen, OceanGate has developed a unique monitoring system that includes both strain gauges and acoustical sensors that listen for any sounds that could indicate all types of failures. “We can hear small things, like air pockets in the resin or the resin collapsing or fibers buckling,” says Rush. If the sounds are different than they were on previous dives, at 1,000 meters or any other depth, the pilot can abort the dive and return to the surface so crews can check the pressure vessel.
The Titan measures 22 feet long, 9.2 feet wide and 8.3 feet high. It features the largest viewport of any deep diving submersible and is equipped with top-line equipment designed for deep sea exploration, including a high-definition camera, sonar and 40,000 lumens of external light. It’s designed to handle site survey and inspection, research and data collection, media projects and more.
Titan’s missions to date have been test dives. Rush made a solo dive to the 4,000-meter level last December. Four months later, he was part of the four-person crew that helped Titan set a world record as the first non-military submersible to carry more than three people 3,760 meters below sea level. Next summer, the Titan will take passengers down to explore the wreck of the Titanic, which rests two miles below the surface of the North Atlantic Ocean.
As Rush was traveling through these depths, with particulates in the water illuminated by the Titan’s light, he says it felt like journeying through a star field. The voyages have helped him fulfill a childhood dream of becoming an astronaut. “I was exploring space, but I’m exploring inner space,” he explains.
Like most explorers, Rush isn’t content with what he’s achieved. OceanGate is already working on its next generation submersible, which will be capable of descending to 6,000 meters. “With 4,000 meters, we only have access to half the ocean,” says Rush. “At 6,000 meters, 98% of the ocean is accessible.”
Using the Sun to Cross the Ice
Edwin ter Velde and his wife Lisbeth, explorers from The Netherlands, are on a mission they call a “quest for change.” After committing to a zero-waste lifestyle, they embarked upon a unique adventure to draw attention to that cause and to inspire people to live sustainably. Starting in mid-December 2018, they traveled for 30 days across Antarctica and toward the South Pole in a solar-powered vehicle made primarily from recycled plastic materials. They called the journey Clean 2 Antarctica (C2A).
Traveling across Antarctica isn’t an easy undertaking even in conventional, heavy-duty motor vehicles. It is the Earth’s coldest, driest and windiest continent, with average temperatures ranging from minus 76 degrees Fahrenheit at its highest elevations to a balmy 14 degrees along the coast. Any vehicle making this journey must be manufactured from materials that can withstand both the rigors of Antarctica’s climate and its rough, icy terrain. The Solar Voyager had that strength, in part because of the efforts of the Teijin Group.
Edwin ter Velde had initially asked Teijin to help sponsor the trip. “But we thought that partnering up and becoming part of this adventure by supporting it with the Teijin Group’s materials and knowledge would be a better way for us to support them,” says Martijn van der Leeden, new business developer, Solution 2.0, Teijin Limited. “Teijin provided lightweight and high-strength materials for Solar Voyager’s body and structure materials and supported the design and analysis of the tires.”
The Solar Voyager consisted of a truck and two trailers that carried the power-generating solar panels. Its total length was about 52.5 feet, and it weighed approximately 3,275 pounds.