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Meet the Engineer Who Built James Cameron's Mariana Trench Submarine

Ron Allum has made a career developing submarines and exploring the deep ocean. It sounds like a pretty good gig.
Allum at a lunch for Australian of the Year finalists in 2013. Image: Pamela Martin/Getty

In 2002, James Cameron released a documentary exploring the wreck of the Bismarck, one of the most ill-fated battleships of World War II. By the release of his 2005 documentary on the Titanic, Cameron had made 33 deep-sea dives to the 3,800-meter-deep wreck And in 2012, Cameron was the first person to conduct a solo expedition to the deepest known part of the ocean floor, the Pacific's 10,994-meter-deep Mariana Trench.


But the Hollywood heavyweight didn't achieve all that exploration alone. Heading his deep-sea team and driving the design of new submersibles to take Cameron and his cameras to new depths is a very down to earth—even shy—Australian inventor called Ron Allum.

"Ron is a bonafide genius and everyone that works with him knows that to be true," Cameron has said.

I recently sat down for a cup of tea with Ron and his wife Yvette at the World Science Festival in Brisbane, Australia. It felt a lot like hanging out with my best friend's parents—only in this case, I was hanging out with a world-renowned exploratory inventor.

Ron was at the Festival to talk about his work on Deepsea Challenger, the submersible that took Cameron down to the Mariana Trench. In building the Deepsea Challenger, Ron completely rethought the design of submersible vehicles, from how they launch and travel through water to what they're made of. He designed a new material called "Isofloat" capable of withstanding the 16,500psi pressure at the depths of the Mariana Trench. And in addition to rigging lights and high-definition cameras to the vehicle for Cameron, Ron equipped the sub with scientific research equipment to take valuable samples from the sea.

Despite all the inventions, innovations and accolades, Ron is incredibly modest. "I like to facilitate the equipment to allow scientists to do their research and go further," he told me. "I just want to be there to support them in doing that. I don't admit to being a scientist but I can go out and get their samples."


The Deepsea Challenger expeditions revealed a variety of species living at extreme depths of the ocean, some of which are likely new species unique to that previously unexplored ecosystem. But Ron told me the proudest and most satisfying moments of his career have nothing to do with the Deepsea Challenger or any of his groundbreaking work with Cameron.

"No, I think it's all the stuff in the lead-up to Deepsea Challenger," he said. "I was known in my younger days for diving and cave diving. I've dived in some pretty bizarre places… That stuff is more important to me than Deepsea Challenger."

"I've always worked with scientists," he added. "Even in my caving days, I'd go to the end of these caves. It takes weeks of preparation and then when you get to these areas, it might take you three or four days to get to the end of the cave and it's all just to bring back a small water sample and that's so valuable to the scientist."

"When Ron talks about the little bit of caving he's done—he's done a world record cave dive," Yvette told me. "Around six-and-a-half kilometers into this massive submerged cave system. So this little bit of caving he's talking about…"

That world record cave dive in 1983 was through the underwater passageways of Cocklebiddy Cave on the Nullarbor Plain in southern Australia. The Plain is the largest arid stretch of limestone in the world and all its water systems are entirely underground. Ron told me that in 1988 he made his first documentary film there, titled "Nullarbor Dreaming." "That one was quite successful," he said, "mainly because the cave collapsed on us during production."


While Ron and the rest of the documentary team were underground, a freak cyclonic storm built up over the surrounding desert. Winds hit 100km/hr and the sky emptied rain plus hail the size of golf balls down on the Plain.

The cave's surface entrance formed a plughole, through which water rushed down to the cave.

"On long cave dives, we would dive into air chambers and set up a camp and stay there overnight, then go diving from there the next day," he explained. "I was actually on a solo dive coming back to the air chamber when the entrance collapsed."

"This cyclonic storm dumped so much rain that all the surface water came into the cave—it came gurgling down the plughole that was the cave entrance—and it completely collapsed the start of the cave," Ron said, adding that when he came back to the cave camp the turbulence and runoff from the Plain had started to turn the water opaque.

"If I'd come back a few hours later I would have just hit a wall of chocolate brown water. It could have been one of the scariest moments of my life… I do sort of keep thinking about that," he said, now 28 years later.

Ron said his and his team were very professional and managed to keep their cool. Using a cave radio that Ron had invented specifically for the trip, the underground team told the police, television networks and local mining community that had gathered above the cave to hold off on any rescue attempts.


They waited a day for the rocks to resettle and the cave to reform, then managed to squeeze their way through the newly formed path and entrance.

Surely that's just one in a book of scary stories from a career spent diving caves and deep seas, so I asked Ron about other risky situations he's found himself in.

He brushed it off and told me his scariest moment to date was probably getting married the second time.

Yvette laughed it off and said, "There's been a few… There was that crocodile incident." I looked to Ron, hoping for a riveting tale but he shrugged it off. "And what about that time with the great white?" Yvette asked. Another shrug from Ron. Yvette continued about the time Ron jumped off the back of a boat in the Jardine River, in Far North Queensland, in the middle of the night to film a saltwater crocodile.

"But I could see it!" Ron said. "I was chasing it. It was going hell for leather to get away from me… Although then I realized maybe that was junior and maybe mum was on her way."

"And then you got bitten by that croc in Costa Rica," Yvette reminded him.

"Yeah that was a bit stupid," he admitted.

I asked Ron, if he can continue to escape collapsing caves and out-run crocs, what's next?

Ron said he's focused on looking at ways to go deeper, safer and for longer. "After Deepsea Challenger, I just wanted to go further," he told me. "You know, recently scientists put a microphone on the bottom of the Mariana Trench, expecting it to be the quietest place on Earth, but they were astounded by the results. They're the kinds of things I just want to support. There is no reason why we can't explore the deepest points of our oceans and bring back valuable data."

"You never, never know if you never, never go," he said, reciting an Australian catch-phrase he's chosen to live by.