Submarine to visit deepest parts of the ocean in Five Deeps Expedition | Hacker News Reader

Submarine to visit deepest parts of the ocean in Five Deeps Expedition

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83 pointsvinnyglennon27 comments

> It’s a spot no human has ever explored, and it’s so deep that any communications from the submarine will take seven seconds to travel back up.

I found this interesting. Are they going to use sound waves for communication? Aren't there any electromagnetic wave based communication mechanisms that work in the ocean or does the depth of water absorb all emails?

I'd guess they use either aucustic communications with some encoding sheme[0], or some kind of VLF communication system with very low bit-rates.

[0]: https://en.wikipedia.org/wiki/Underwater_acoustic_communicat...

The depth a RF signal reliably penetrates to in water is proportional to its wavelength.

Hence the ELF sites used to communicate with submarines - we're talking EM radiation at a frequency of a few tens of hertz.

These transmitter sites are huge - not to mention the power requirements, which is easily in the MW range - so they could only be used to communicate from shore to submersible. Return comms would have to be by acoustic means, due to size and power constraints in the submersible.

Also, the bandwidth of ELF systems is very low - think several seconds, if not minutes per bit - the bandwidth of an acoustic system is orders of magnitude higher.

Edit: I had bungled the first paragraph. My apologies.

ITYM "proportional", not "inversely proportional". The ELF transmissions have very long wavelengths.

-You are right; I was thinking 'frequency' but writing 'wavelength'. Thank you!

While I have to admit I am dubious of the scientific value of sending humans down into the abyss, I'll keep an eye out for news on their progress; there's no denying that most of the world's deep oceans are pretty much blank spots.

Also, while I think an AUV or ROV could accomplish as much as a manned submersible, I am envious as [] of the people who get to go down there! Where do I sign up?!?

Really? In my mind it sounds way too scary to do so!

But for some reason I would like space travel rather as to me it sounds safer but I can't back that up.

Going towards lesser extremes, I am also fine with flying but really dislike being on boats. Probably just an irrational tjinh I though.

I think the psychological trick played on our minds is that the water is weighing you down, preventing escape, while the emptiness of space gives the opposite feeling

It's also a harder technical problem. The pressure difference between the inside and outside of a spacecraft is pretty small (less than the pressure in your car tires). The pressure difference at the bottom of the ocean is several orders of magnitude higher.

I'm no physicist or engineer but isn't it easier to deal with the absence of pressure (a vacuum) than with lots and lots of pressure?

It's not so much the "direction" of the pressure as it is simply the scale of the pressure you have to deal with. ~15psi (space) vs ~15,000psi (ocean).

Sorry, yes, this is what I meant. There is less "difference" of pressure in vacuum vs. depths of the sea.

-That it is, but the upside to oceanographic research vs space is at least two-fold, IMHO:

a) You don't strap yourself into a seat on top of a few hundred tons of high explosives prior to getting started. Major plus in my book.

b) Barring catastrophic failure of the pressure vessel, all you need to do to get to a safe-ish state is to jettison enough weight to become positively buoyant - and off to the surface you go.

Wouldn't you also have to make sure you don't rise too quickly to the surface, or you'll suffer possibly fatal decompression complications?

The interior of the submersible is kept at surface pressure, so you'll be fine.

(When diving in shallower waters, in a suit, this would be a concern; however, as you are at (or very close to) surface pressure throughout the dive - no problem.)

That makes sense – thanks!

Yes but the engineering tradeoffs for space are harder. You have to get the vessel into space in the first place. The pressure hull of a sub can be stupidly heavy because it needs to sink. (Yes I know this is a gross over simplification).

It’s also a lot easier to contain pressure than to resist it. If you had to build something that would hold 15,000psi internally for some reason, it would be much simpler.

Yes, also because there is no direction of pressure in a vacuum.

In the ocean pressure comes in the form of current. I guess it can be very tricky to navigate in a high pressure fast or turbulent current.

Could it be that our species has had time to develop an instinctual fear of deep water that we haven’t had the chance to develop for space travel?

Your assumption that the species isn't afraid of space travel is invalid.

I don't know, deep space terrifies me as well. I remember trying a VR game that had my flying through deep space and to me it was terrifying.

The pressure difference is much worse underwater but in contrast to space it doesn’t take much energy at all to get there and back, the speed difference with your start/end point is very small, and it doesn’t matter very much how massive the vehicle is. Swings and roundabouts.

I’m pretty sure comfort is not the top design criterion when building a machine that can take multiple humans miles deep, but I’d love to see the inside of it. I imagine even a bathroom break could be challenging.

There's some detail on the interior of the sub on their site [1]; note the slider on the "Key Features" photograph that shows you the inside when the slider is moved to the left.

[1] https://fivedeeps.com/home/technology/sub/

I wonder if they will find more ecosystems independent of the sun. Or may be a good footage of the giant or collosal squids. Or something we can't even fathom currently. This is almost akin to deep space exploration for aliens except that here we are guaranteed to find some...

"Cthulhu likes that"

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