Accidental implosion yields new measurement for ocean's deepest point | Hacker News Reader

Accidental implosion yields new measurement for ocean's deepest point

nationalgeographic.com

52 pointsdivbzero36 comments

I attended a talk at Nat Geo by the engineers who built the drop probes enclosed by glass spheres. A few interesting bits as I recall them:

The glass is made in two hemispheres and the contact surface is ground flat. There’s no glue or mechanical attachment; the hemispheres are carefully lined up by hand and then they pull vacuum. Atmospheric pressure alone keeps them mated prior to submersion. Then of course they are pushed together harder and harder as they descend.

The engineers talked a university into letting them use their hyperbaric chamber for testing. One of the prototypes failed at high pressure, which sounded like a bomb going off. The glass was reduced to tiny slivers, which the university was still finding in nooks and crannies years later. (The Nat Geo team was not allowed back after that.)

The probes were timed on the bottom by using thin steel wire to attach the weight. Basically the wire would rust until it broke, then the globe would float to the surface and start broadcasting a radio beacon for pickup. They adjusted the time by varying the thickness of wire.

They also stuffed the globes with LED lights and used them as “sun-like” sources of illumination for underwater cave photography.

You don’t need to pull a vacuum for this. If the glass is sufficiently flat and clean, the pieces can be attached with a process called ‘contact bonding’ where the surfaces are close enough to be attracted by Van der Waals forces.

Is this similar to cold welding that may happen in space (where surfaces don't oxidate)?

It feels more similar to wringing gauge blocks (or other very flat surfaces) together, though it is more disputed how that works. You can separate the two objects if you pull them apart with a reasonable force (or more typically shearing and some leverage) and if you imagine the atomic scale structure of the surface, the crystal lattice will break down as atoms on the edge have bonds going into the material rather than free electrons hanging out waiting for another atom to bond to.

I don’t know if cold welding is really welding but contact bonding is certainly not like welding.

AFAIU cold welding is like welding in that the two materials which were separate atomic matrices become one, as atoms from one 'object' do not care if their neighbours are from a different 'object', if they are close enough to be attracted to each other. It only works if the material does not have an oxide layer at it's surface, which is why it's been observed to happen in space (and apparently caused issues with joints no longer being able to move, or something like that).

To be clear, this wasn’t my project, I just posted what I remembered from the talk.

> the hemispheres are carefully lined up by hand and then they pull vacuum.

I'm guessing it was not very close to vacuum? The article mentions air explicitly:

> As the instrument's glass collapsed under the weight of five miles of water, it released a pocket of air that oscillated under pressure before splintering into a veil of tiny bubbles.

Yes, sorry, I meant they created a pressure differential by sucking out some air; that is called pulling vacuum even if you don’t remove all the matter (hard vaccum).

"The night before each big deployment, he writes up a list of everything that could go wrong.

"It sounds a bit sadistic," he says. "But it's a really good exercise to do.""

Anyone else finding beauty in this?

The meticulous and tedious, often thankless nature of scientists and their work. Also a nice strategy to implement for some other projects/fields.

As a software engineer, one the reasons I like to write tests is because it forces me to think about everything that could go wrong.

Once I write tests for all the things that could go wrong and verify the correct behavior, I feel a lot better than if I only test the happy path (when everything goes right).

I wish software developers would take more time to think about how things could go wrong.

> I wish software developers would take more time to think about how things could go wrong.

I wish more PMs understood the need to spend developer hours on it.

I wish customers would pay for the developer hours needed to be spent on it.

PMs shouldn't have any input in how development is run (that's an EMs role). Dev time should be quoted to them including the time to test otherwise you're implying testing is optional and can be skipped

Fair and good point, but this depends a lot on the structure and health of the organization.

Canadian astronaut Chris Hadfield wrote about the very same thing in discussing preparations for space flight. Kinda cool. https://archive.org/details/isbn_9780316253017

That's called negative visualization and has roots in stoicism.

https://dailystoic.com/premortem/

Writing down everything that can go wrong is the only proper response to Murphy's Law.

Only when you've written them all down, do you have a list of things to actively expect to go wrong, and prevent or mitigate.

It is the difference in handling risk between using knowledge, skill, technology, and planning to manage risk, vs relying on Pure Dumb Luck and hoping to get away with something.

For anyone who doesn’t want to enter their email to continue.

https://outline.com/tdSyGz

Also, for some reason I always assumed the Challenger Deep was in the mid Atlantic Ocean. It’s not, it’s a few hundred miles southwest of Guam in the Pacific Ocean.

The middle of the Atlantic is the Mid-Atlantic Ridge, where (as you can tell by the name) the ocean is shallower than on either side. The ridge is pushed up by convection from below and by the rocks being warmer there. The gentle slide of the ocean crust down from spreading centers helps drive the spreading.

> The gentle slide of the ocean crust down from spreading centers helps drive the spreading.

Sounds like there is a self-reinforcing effect at play here?

Although the deepest part of the Atlantic Ocean is very deep indeed, north of Purto Rico.

https://en.m.wikipedia.org/wiki/Milwaukee_Deep

No, I'm not going to "enter my email to continue." Looks an interesting article, but, no, sorry, modal sign ups that continue after a refresh lead to a page close. :/

Turn off JS -- or leave it off by default -- and such annoyances tend to naturally disappear. (When the page content also disappears, that's usually when I leave.)

Just switching to reader mode works for me, though it gets rid of images too. (Admittedly the pictures are what generally draw me to National Geographic.)

Or, even better, install uBlock origin, and use one (or more) of the "Annoyances" lists.

or just enter someone else's email. i like using page@google.com

So back in the 1940's there was a proposal to use impolsions in the deep acoustic channel as an SOS system. https://en.m.wikipedia.org/wiki/Sofar_bomb

TIL about the deep sound channel.

I don't quite understand why an instrument imploding was such a unique inadvertent experiment? I would have thought that part of normal seafloor mapping was using sonar/ultrasound anyway, or pneumatic charges or something similar.

"Only a few people have ever visited Challenger Deep."

That kind of goes towards the answer of why it was useful, but also begs the question of why there haven't been more scientists there.

Possibly the combination of it occurring at great depth and there being another instrument-laden probe right there.

yeah you would think if it was so useful they could have planned an experiment like this. maybe it's illegal to set of underwater explosions on purpose for a research institute?

Oh man underwater exploration is so cool, the drone sonar mapping in particular.

Heard a cool podcast on Embedded FM 363 Squishy Nature

Talks about electronic design under deep water pressure/Rovers

Also enjoyed the Deepsea Challenge James Cameron free (w ads) on YT.

If this accidental implosion worked so well, why not use it purposely?

Also, it seems like a great scifi premise to stir up the kraken/cthulu/hydra.

So - interesting, turns out it is done, and in this very area too. I read the 1960 report of their dive[1], linked to in the parent article. And it talks about "800 TNT explosions" preceding their dive in the Trieste.

[1]http://www.deepseachallenge.com/the-expedition/1960-dive/

just type in some random email :)

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