COURTESYFIVEDEEPSEXPEDITIONdidn’t have the cash. “I’d wanted to build one for more than
a decade,” Lahey explained. “I didn’t have the financial
capability, and I didn’t have a client willing to fund it.”
Then, in 2015, that client called.
Lahey told Vescovo that he could produce the vessel
in about two years, which seemed optimistic. There
was no commercial submersible in existence capable of
reaching the deeps, which range from 6,000 to nearly
11,000 meters. There were very few, in fact, that could
survive the ocean’s average depth of 3,688 meters. And
only four—all of them government-owned and unavail-
able for private use—were able to manage more than
6,000 meters. The newest and most capable of the
bunch, China’s Jiaolong, hadn’t gone below 7,062.
Lahey and his chief designer, an Englishman named
John Ramsay, were certain they could do it, especially
since the sub was so simple: It needed only two seats. That
allowed Ramsay to make the design compact, just 15 feet
long, 6.2 feet wide, and 12 feet high, about the size of two
stacked minivans. Keeping a sub small lowers costs and,
more important, weight. You have to make up for every
pound you add with buoyancy, and whatever provides that lift (air, gas,
foam) takes up space. That doesn’t matter for giant military craft that
carry wee nuclear power plants and rarely go deeper than 500 meters.
But it matters a lot for submersibles, a class of vessel toted on surface
ships and lifted into and out of the water by deck cranes.
At first, Vescovo saw plenty of things he could do without. He didn’t
even want viewports to see through. He wasn’t crazy about the idea of
a manipulator arm either. More stuff meant more opportunities for
delays—and failure. But he hoped to sell the sub after the Five Deeps,
and Lahey explained that there wasn’t much resale value in a vessel
with no windows or research capability. As Vescovo studied the slight
history of deep-sea exploration, and spoke with ocean scientists, he
also realized that he wanted his mission to have purpose. It was an
adventure, but it could and should also leave a scientific legacy.
Limiting Factor, which Vescovo named for a vessel in a series
of science-fiction novels by Iain M. Banks, does not look like the
torpedo- shaped submarines you’re used to seeing. Those have con-
tours that let them primarily cut forward in the water—not straight
down and back up. Ramsay says that when he looked around for
inspiration, he noticed that “there aren’t many things in the world
that are expected to go the same speed both ways.” Really, all he52 FALL 2019 • POPSCI.COM
Small but Mighty
Vescovo’s Limiting
Factor is rated for
unlimited diving depth.