The Tech Behind James Cameron's Trench-Bound Submarine

MrSeb writes "Yesterday, James Cameron completed a five-mile-deep test dive in the Pacific Ocean, in preparation for a seven-mile (36,000ft, 11,000m) dive to Challenger Deep, in the Mariana Trench; the deepest place in the world. We don't know when the actual dive will occur, but it will probably be soon. At 36,000ft, the pressure exerted on the hull is 16,000 psi; over 1000 atmospheres, and equivalent to eight tons pushing down on every square inch of your body. Understandably, building a submersible (and equipment, such as cameras, motors, and batteries) that can withstand that kind of pressure, and then safely return to the surface, is difficult. This article digs into the technology required to get Cameron safely to the bottom of the ocean, film some 3D, IMAX footage, and then return to the surface."

Comments

units?

[Anonymous Coward]

How does one reconcile 16,000 psi with 8,000 tons per square inch?
Seems something is off.

Also pretty sure no human bodies will be experiencing that pressure

Re:units?

[Forty Two Tenfold]

Seems something is off.

Yeah, seems someone read "8" and then added three orders of magnitude. 1 ton = 2000 pounds.

Re:units?

[tsa]

Who cares. Those units don't exist anyway. How many pascal are we talking about?

Re:units?

[FridayBob]

... Also pretty sure no human bodies will be experiencing that pressure

On the contrary, it's most likely that they have and will ... though not while alive.

Some years ago I was into technical diving and learned that the deepest dive ever for a human was a simulated one in a pressure chamber. Using a special, and no-doubt constantly changing mixture of gasses that included plenty of helium, they were able to crank up the pressure to a simulated depth of about 750 meters (only about 7% of the Challenger Deep) before the "diver" could go no further. Apparently, his nervous system was no longer able to function properly beyond that point... just because of the pressure. His simulated ascent, by the way, took something like a month.

I was somewhat disappointed to learn all this, because it meant that a really deep dive using a liquid rebreather, like in The Abyss (1989, James Cameron), would never be possible.

Hard?

[kurt555gs]

Isn't this 1961 technology we're talking about? Remember the Treste!

Re:Hard?

[Caerdwyn]

Indeed, we do remember the Trieste.

Just like going to the moon... something we did in the 60's, we've basically forgotten how to do for the lack of will to do it. So we have to reinvent the wheel, only this time in a more risk-averse environment (and therefore far more expensive to accomplish).

Re:Hard?

[yodleboy]

why does the Trieste come up every time this new vehicle is the topic? The Trieste was an underwater elevator and no more. You went down, you saw a sliver of the bottom through tiny portals and you went up. It's less exploration and more "i got there first". Deepsea Challenger can actually, you know, MOVE. Sure they could have sent a robot, and maybe that gets you all hot and steamy. For me, it's nice to know that people are willing to explore somewhere now that manned space flight is on it's way out the door.

Re:Hard?

[yodleboy]

idiot? wow. did you bother going to the expedition site? it says all over the place they will be using the sub's ability to move horizontally @ up to 3 knots while to explore various areas for up to 6 hours. That sounds more than fractions of a kph or minimally mobile. maybe they are overly optimistic, but it's a big improvement on the original Trieste.

Re:Hard?

[hey!]

I suspect you are confusing a bathy*scape* with a bathy*sphere*.

Trieste could operate submerged 24 hours and could move freely at a speed of 1 kt. It was succesfully used to search for the wreck of the USS Thresher (SSN-593), which it found at a depth of 8400 ft, so obviously Trieste was a very capable boat.

In it's famous Challenger Deep mission it spent 20 minutes on the bottom made at least one important scientific discovery: sole and flounder swimming. Before that it was believed that vertebrate life could not survive at such pressures. Not a bad scientific haul for an 8h 23m work day.

The bathy*sphere* was no scientific slouch either, making significant contributions to both marine biology and physics.

Re:Avatar

[Forty Two Tenfold]

It did, but they got enough Unobtainium to build this sub.

Re:Avatar

[TheRaven64]

Blue people make good soldiers, when led by white officers...

Onion

[Anonymous Coward]

Um, maybe it's not this simple, but...

Lets say you have a submarine with a metal shell that can withstand the pressure at 1000 feet below sea level. (For simplicity, call it a pressure of '1000'.). You can lower it only that far into the water before the pressure exceeds the amount it can handle, and the shell collapses. Okay. Now, what if you place that shell inside an slightly larger one? Lower them both to, say 999 feet, then open a valve to let the water in between the shells. Close the valve, and drop the shells another 999 feet. The inner shell has the pressure of 999 pressing in, which it can withstand. But that 999 water also presses out. The outer shell then has 999 pressing out and 1998 pressing in, a net of 999 pressing in, which it can withstand.

Repeat with however many layers you need, and you should be able to go down to the bottom of the Mariana Trench, no?

Re:Onion

[Ethanol-fueled]

Heh, you're funny.

So to go down to 10,000 feet below sea level, you'd essentially need ten shells, each with a valve, with each shell becoming a point of failure. And that's more of an ideal situation, not taking into account how you're gonna get shit in and out of the vessel.

I work in this industry(shoutout to DeepSea Power and Light, here in San Diego), and we used pressurized oil to add structural integrity to certain electronic components. In fact, it was even mentioned in the article.

You could have one onion layer of super-high pressurized oil, but it would essentially behave like a solid which could be pushed into the inner shell. Shit, why not, oh, just have one shell designed to withstand the pressure? Or, better yet, fill the whole vessel with oil pressurized to 1000 bar? That'll show those damn skeptics.

Re:Onion

[tragedy]

A few problems with that approach. Among other things, I don't think you'd want an incompressible (or at least difficult to compress) fluid between the outer and inner shell. If it's "pushing out" on the outer shell, then it's also pushing in on the inner shell. Not to mention that you actually want to be able to see out of the thing with a window. Given the complexity of a window and how well our cameras work these days, the window represents a whole lot of complex engineering for very little benefit, but if you're going to have a manned craft, you might as well have a window, otherwise you have to shrug your shoulders and mumble when someone asks you why you bothered to actually go down there rather than spend that engineering money on a telepresence system you could operate from a ship on the surface or even from the comfort of home. So, if you need a window, you would have to have a window in every layer of your system and figure out a very complex system with super-high precision optics that work properly even when the high pressure has warped their shape. Then there's your connections between the controls in the inner part of the sub and all the equipment outside. I imagine the sub has two or more power systems with one or more for the cockpit and one or more living at outside pressure for the outside of the sub and with all the equipment outside the cockpit controlled "wirelessly" (or using the whole cockpit hull for a "wire" anyway). Having nested shells is going to require such a system to be very complicated and to be multi-layered as well, with each layer presenting another point of failure. Overall, you're better off in just about every way if your multiple shells are all merged into one shell.

Essentially, the only special technology you need for a human to survive to that depth is a thick enough shell around them. Nothing technologically amazing or any new ideas needed. Having a well sealed hatch and a well-sealed window are the more complicated parts, since those may not deform evenly with the rest of the shell, but even those aren't really hugely complex engineering problems. The trickier problems are getting all the stuff that needs to survive _outside_ the shell to survive at that pressure and to not explode from internal pressure back up at sea-level. Every single little part needs to considered,and not just mechanically since, at that pressure, materials may have altered chemical and electrical properties. The cockpit is simple and well-understood by comparison.

For some reason I'm not quite clear on, your suggestion has made me think of _Star Trek IV_, when Scotty trades the formula for transparent aluminium for plexiglass to make the aquarium for the whales since plexiglass is the best substitute for transparent aluminium. I still to this day have not been able to fathom why they couldn't just use regular, non-transparent aluminium, or whatever metal the Klingon ships inner structure was made from to make their tank. Why did it need to be transparent? I don't know and I don't know why this conversation so strongly reminds me of that.

Re:Cameron

[citizenr]

Remember how he was going to single-handedly fix the Horizon oil disaster off the coast of Louisiana? Never happened. Actually, not a single thing this guy has made headlines for has actually panned out.

Cameron != Kevin Costner you retard

Re:Cameron

[tsa]

Didn't Cameron find the Titanic?

Re:Avatar

[slew]

It did, but they got enough Unobtainium to build this sub.

Actually the alchemy that Mr Cameron performed was to transform 3D hypium and virutal Unobtainum into gold by using a motion picture catalyst derived from a pocahontas precursor...

Re:Avatar

[Nidi62]

Great. The last thing we need is an army of evil smurfs led by Gargamel

Re:Avatar

[LordLucless]

I've found that people with an IQ of over 80 think that judging people's IQ by the movies they watch says more about the observer than the observed.

You should read up

[dutchwhizzman]

Diving breathing issues aren't about gas pressure, but about saturation of blood and tissue with gasses. At higher pressure, your blood and tissue take up way more gasses than they do at surface pressure. Therefor, if you dive deep, you will become equivalent to a soda bottle. If you surface too quick, it's like someone shakes you and then takes the cap of the bottle. All of a sudden, there will be bubbles in your entire body. Those bubbles will kill your (brain) cells, by oxygen deprivation.

At higher pressures, gasses that are normally "inert" to the human body tissue, will form chemical bonds with your tissues, making the gasses poisonous. That is why there are different gas mixtures used for high pressure (deep) dives.

Even if you can overcome this by using liquids to replace the gasses, it appears that your nerve tissue will have electrical/chemical problems transmitting signals at about 750 meters (75 times atmospheric pressure).