Success at 27,000″: What About 36,000″?

Lori Roberts is a high school biology teacher in Muscle
Shoals, Alabama. Lori is a leader in ocean education and is a graduate
of National Geographic Education’s two-year professional development
program, the National Teacher Leadership Academy.

How does it feel to be alone in the dark and 27,000″ feet under seawater? James Cameron said, “…it’s simultaneously scary and exhilarating” after his final dive to the New Britain Trench. I wondered at this feat of engineering that allowed for a successful dive. He must have felt a surge of relief fill him when he heard the weights fall off.


The submersible DEEPSEA CHALLENGER is deployed into the water for a test.

Electromagnets hold the weights in place on the DEEPSEA CHALLENGER,
James Cameron’s sub. The weights assist the sub in its descent to the
bottom. When Cameron is ready to ascend and resurface, the power on the
electromagnets is turned off, and the metal weights fall off. What about
residual magnetism after the power is turned off–has this been
considered? How does it work? What if the electromagnets don’t fall off?

we even get into that: What is an electromagnet? My father Robert, a
retired engineer, explained it to me: Electromagnets consist of coils of
wire wrapped around a steel core, very similar in principle to a
capacitor or condenser. As my father and I discussed the concept, we
started thinking about residual magnetism and the impact it could have
on a successful dive by Cameron. According to How Stuff Works,
capacitors (also called condensers) store electrons. NASA used glass
capacitors to help deploy space probes, for example. My dad says that an
electromagnet, like a capacitor, can retain a residual charge of
electricity–even if it has been disconnected for a time period as long
as a year.

Dad told me a story: He warned a man against touching
a transformer (a condenser that is used for a power surge to help start
an electric motor). This particular transformer had been “turned off”
for a long period of time. The man accidentally touched it, and became
“enlightened.” He survived quite a few volts at very low amperage, but
still felt the shock. That is residual principle in action. The
electromagnets on the Cameron sub will obviously be energized for a
certain length of time. Will they turn loose  at 36,000″?

is a plan B–actually there are four fail safe plans in place for such
an event. Here is how it is supposed to work, according to mission
engineer Ron Allum: DEEPSEA CHALLENGER will sink initially, due to the
more than 1000 pounds of steel weights attached to it. The weights are
held in place by powerful electromagnets. In order for Cameron to
ascend, he must turn off the power to the electromagnets. If the weights
do not drop, Cameron will not rise. Allum says there are several backup
systems in place:

•    If there is a power failure, the weights will drop automatically.

•    At the surface, someone can command the weights to drop.

•    A special wire connects the weights to the sub; it corrodes in seawater after about 11 to 13 hours.

A “frangibolt” can be used to heat and break the bolts that keep the
weights in place. Ron Allum explained, “it is a special type of material
that has a good memory; you squash this assembly and it will stay
squashed until you heat it, and that will release the entire
weight-release mechanism.”


Crews prepare DEEPSEA CHALLENGER for its first test in the ocean at Jervis Bay, south of Sydney, Australia. In the coming weeks, the submersible will travel to the bottom of the Mariana Trench as the centerpiece of DEEPSEA CHALLENGE, a joint scientific project by explorer and filmmaker James Cameron, the National Geographic Society, and Rolex to conduct deep-ocean research. Photo by Mark Thiessen, NGS.

Godspeed, Mr. Cameron; this is an
amazing journey you are taking us on. What if you could take a
passenger? My students are divided on this topic. Some say, “I wish I
could take the journey with him.” Others say, “No way, I would be too
scared!” In any event, we are excited to live vicariously through James

For more on the science of the sub, visit the Systems and Technology section of the main website.

–By Lori Roberts

Critical Links
1. (Main National Geographic site for the expedition)
2. (National Geographic Education site for the expedition)
3. Expedition Journal (The official blog from the deck of Mermaid Sapphire, James Cameron’s mother ship. Our Education bloggers are using this blog, as well as the main website, to inform their writing about the expedition)

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