National Geographic


Expedition Journal

The Master Builder

“I just wanted to … say thank you … to everyone for making it possible for me to … make yesterday’s dive.” The shy and self-effacing Ron Allum, codesigner of the DEEPSEA CHALLENGER, had been waiting three years to say those words.

Team Cameron was on the bridge of the Mermaid Sapphire reviewing yesterday’s highlights of Allum’s 3,700-foot (1,128-meter), six-hour dive off the west side of Ulithi Atoll. Twenty-five minutes after leaving the surface, he reached a flat seafloor near a steep cliff. Crouched inside the DEEPSEA CHALLENGER, he reported a “strong current running.” While he waited on the bottom, the ship’s two-ton Quasar ROV was lowered through the depths until it was within sight. Then, assisted by the communications team on the Mermaid Sapphire, he and the ROV flew across the seafloor to rendezvous with lander Mike.

Jim was in the Mermaid Sapphire’s ROV room watching all of this on video screens. The three vehicles, ten cameras, and multiple arrays of lights parked on the seafloor transformed him into the A-list Hollywood movie director. “Move slowly to the right,” he told Allum. “Fly in close and dim your lights,” he advised ROV pilot Donnie Cameron. For three hours, the man on the ship and the man on the seafloor—co-inventors of the world’s deepest diving sub—worked together to make a permanent 3-D record of sediments and rocks, the sub and the lander, and the animals attracted to the lights.

When they finished, Allum turned south and began to explore his surroundings. “I’ve found a big rock,” he said. The sharp-edged rock marked the base of the cliff, and Allum—a man with a long history of cave diving— wanted to know what it looked like. Powering upward with his vertical thrusters, he discovered an almost vertical scarp filled with fissures and cracks. He ascended more than 100 feet (30 meters), shining his eight-foot (two-meter) column of lights on countless creatures, including glass sponges, black coral, and crinoids.

Everyone on the ship was cheering for the man inside the DEEPSEA CHALLENGER. His fingerprints were on most of the sub’s thousands of components. He had thought about them, he had responded to Jim’s thoughts about them, and he’d brought together the initial team that assembled them. His brilliant innovator’s mind conceived many of them. The buoyancy foam was just one example.

Syntactic foam for deep-ocean buoyancy had been around for decades and companies advertised products that would go to full ocean depth. When Allum tested their samples under hydrostatic pressure, they cracked or collapsed at 16,000 pounds per square inch (1,100 bars). After repeated failures, he started thinking about making his own. He spent months blending, testing, and tinkering and came up with a mixture of glass microspheres suspended in a mix of epoxy resin. Then, in a swoosh of lateral thinking, he decided not to set the foam in a vacuum like everyone else; he would set it under pressure. It worked. The DEEPSEA CHALLENGER‘s foam doesn’t yield until 22,000 pounds per square inch (1,517 bars) and gets lighter at depth because it compresses less than seawater.

There was a game-changing bonus: The foam’s compression and tension strength meant it could be machined into slabs and glued into a multilayered “strong beam” that fit the pilot sphere like a top hat. In a stroke of alchemy genius, Allum eliminated the need for a heavy-metal structure to hold the sub together.

Allum has about him an unsophisticated innocence, an inherent goodness that seems out of place in a fast-paced, high-tech world. When he climbed out of the DEEPSEA CHALLENGER after the dive, he struggled for words to express his gratitude. He didn’t need to make the effort; his mile-wide smile said it all. The football stadium cheers and applause from his teammates was a “thank you” for all he’d done for them.

Written by Dr. Joe MacInnis

Photograph by Joe MacInnis

Science Partners

  • Additional major support provided by The Alfred P. Sloan Foundation
  • NASA Jet Propulsion Laboratory
  • Scripps Institution of Oceanography, UC San Diego
  • University of Hawaii at Manoa
  • University of Guam