From Pandora to the Pacific

In March 2012, filmmaker and ocean explorer James Cameron became the first man to travel solo, and only the third man ever to descend 11km down into the Challenger Deep, 50 years since Jacques Piccard and Don Walsh dived there in the bathyscaphe Trieste. The voyage of Deepsea Challenger into the deepest known place on Earth was the culmination of seven years of work by Cameron's design and engineering team.

E&T spoke to Ron Allum, Australian broadcast engineer and cinematographer turned submarine designer, about the electric green submersible that he co-designed with Cameron. "We learned a lot from the Russians," says Allum, whose collaboration with Cameron dates back to the filming of 'Ghosts of the Abyss' in 2001. "The Mir submarines that we used for 'Titanic' and the 3D IMAX movie 'Aliens of the Deep' are 1980's technology, albeit sound and robust." The team wanted to move submersible design into the 21st century.

One major goal was to bring the final vehicle in at less than 10t to maximise the number of support vessels that could carry the sub – the weight was part of the logic behind going for a single rather than multiple passenger vehicle. The final design weighed in at slightly less than12t.

Another key design element for any attempt at full ocean depth (FOD) is the ability to descend and ascend quickly, maximising bottom time, hence the vertical orientation and torpedo-like shape of the design. Cameron took two and a half hours to get down 11,000m, had almost three hours filming at the bottom and returned to the surface in an hour and a half. In contrast, the 150t Trieste spent only 20 minutes in the Deep in zero visibility in a cloud of silt.

The engineering challenge to accommodate the enormous changes in pressure and temperature on the materials during the voyage was huge. Allum says: "The external pressure of the depth of seawater on every surface is immense, way beyond the scope of normal engineering, over 1,100 times atmospheric pressure." An entirely new imaging technology – including an ultra-small stereoscopic camera that could be mounted on a boom arm – was needed. "The interior volume of the camera housing has to be small to minimise implosive force should it fail, as there is a risk of sympathetic failure in nearby vessels including the pilot sphere. We had a go once on a Mir, and that sounded like a hand grenade going off, but fortunately it was the only implosion on that occasion."

Key innovations

"Because space in the passenger capsule is so limited we wanted to get as much as possible outside of that, though obviously life support had to stay inside," explains Allum. "All the electronics went into the pressure-balanced oil-filled boxes, the thrusters, the lights, most of the cameras and a manipulator arm to collect samples were all mounted on the exterior."

Unsatisfied with the syntactic foams available at the time (some failed pressure tests), Allum decided to make his own from scratch in a patented process now co-owned with Cameron. The foam is essential to counteract the weight of the steel hull and gains in buoyancy as it goes deeper. "We needed foam that could be moulded into blocks so that we could attach equipment to it. With the foam problem solved in February 2011, manufacturing continued for the next 200 days," he says, before adding: "With Jim [Cameron] due to disappear into production of the next two Avatars in April 2012, we were up against it. It would have been nice to have had a second take on some of the electronics, but the sub really came together in the last 12 months."

While most of the key technological innovations were developed by Allum and his team, British engineers played a significant role. The life-support systems were supplied by Cornwall-based Ambient Pressure Diving. Martin Parker, AP Diving MD was approached by the Deepsea Challenger team after presenting at the Oztek conference in March 2011. "I visited them in Sydney, being very open with them as to how we would tackle the job. By May, we were on board. We redesigned the CO₂ scrubber from first principles delivering a better-than-military submarine spec for the cabin environment of less than 0.1 per cent CO₂ and 30 hours of endurance in a tiny package."

The first units were delivered in September 2011 and Parker was in the sphere a couple of weeks later on a simulated dive. Manned dives in the sealed sphere got longer and longer, up to a marathon 18 hours, and finally in-water trials started in January 2012. "My short dive inside the sphere gave me an insight into what it would be like on a real dive, and you have to hand it to Jim, it's not just the outer sphere that was made of steel."

Travel in style

The acrylic dome that forms the pilot's viewpoint was manufactured by world-leading acrylic specialists Blanson Ltd in Leicester, UK. Dr Charles Johnstone, chartered engineer and MD, told E&T: "We didn't know what the project was when we started to supply prototypes for pressure testing in 2007, it was top secret. The high-grade acrylic is cast here and precision machined to obtain the critical tolerances required to seal the vessel."

There was a bit of a hiatus as Cameron figured out how best to deal with the optics created by the conical interior of the spherical port, and everything had to comply with the American Society of Mechanical Engineer's standard for pressure vessels for human occupancy. Blansons supplied the 18.8cm-thick final port to the team in 2011.

The 1.83m-tall filmmaker spent the entire dive folded up in a 1.11m internal diameter steel sphere with his camera at the viewport. He took up yoga and running to improve his flexibility and to be able to cram his body into the cockpit. His view of the dive was via a monitor attached to the camera.

Ron recently formed Ron Allum Deepsea Services to make available the technologies that he and Cameron developed during the design of the sub. He believes that one valuable use of the light and extremely tough syntactic foam would be to protect the occupants of military armoured personnel vehicles from roadside bombs.

DeepFlight ambitions

Cameron's team is not alone in having ambitious plans to visit the depths of the oceans. Virgin Oceanic is currently in sea tests of a submersible originally designed by British engineer Graham Hawkes for Steve Fossett, and Richard Branson plans to use it to dive to the deepest parts of five oceans. Virgin Oceanic declined to speak to E&T, claiming that the US Department of Defence had identified their submersible as an "article of war" and that should they discuss it, Virgin risked being prosecuted. Deepflight Challenger looks more like an aeroplane than a submarine, and its hull is made of carbon fibre with a fused quartz hemisphere at one end.

Florida-based Triton Submarines have sold several 1,000m rated submersibles and have more orders on the books. They also have an FOD vehicle in advanced stages of design and are seeking funding for the build. Their design uses two large hemispheres of glass as the pilot's life support and viewing capsule. The 2.25m diameter, 7.5cm thick hull is large enough for three people. Reminiscent of an alien spaceship, the Triton 36000/3 design offers "wonderful visibility and, importantly for longer missions, passengers will be able to sit comfortably upright", explains CEO and founder Bruce Jones.

Everything hinges on the glass, which is being manufactured by Rayotech Scientific in San Diego. CEO Bill Raggio says: "We are building a test facility that will be able to take the entire vehicle down to 1.25 times maximum pressure. We have also invested in a diamond-tipped five-axis grinder that carves out the precise shape of the borosilicate glass – it's like watching an automated Michaelangelo in action."

Glass becomes stronger under compression, stronger than steel or titanium, but under shear it is weak, so rather than run any cabling through the life-critical glass hull, all controls to the exterior are via multiplexing fibre optic cables. This avoids expansion and contraction due to pressure and temperature changes in abutting materials. "It's this glass design that sets Triton apart, and its not untested at huge pressure," adds Jones. "Some 48cm spheres have already been used to deliver instruments into the deep ocean. We believe that there are no technical barriers to success."

Deep Ocean Exploration and Research in San Fransisco is aiming its vessels at the scientific community and supplied the manipulator arm on Deepsea Challenger. It also has designs for a 1,000m rated Ocean Explorer that can be shipped in a standard shipping container, as well as a FOD submersible. Liz Taylor, president of the company co-founded by renowned oceanographer Sylvia Earle, says: "Ideally we will secure funds to build the prototype 1,000m test platform in the coming year. There is a crying need for scientists to understand the planet's life support system: the ocean."

After all his hard work, Ron Allum had the dive of his life. "Jim needed to film the sub, so I flew it to 1,100m over canyons and huge escarpments while he filmed me from a ROV. I knew that I had to be the first person to see that magnificent underwater seascape. We have better maps of Mars and Jupiter than we do of our own ocean floor."