timothy found BBC coverage of the voyage of the Nereus, which on May 31 dove to the bottom of the Challenger Deep in the Marianas Trench. Only two vehicles have accomplished this feat before, the last 11 years ago. "The unmanned vehicle is remotely operated by pilots aboard a surface ship via a lightweight tether. Its thin, fibre-optic tether to the research vessel Kilo Moana allows the submersible to make deep dives and be highly manoeuvrable. Nereus can also be switched into a free-swimming, autonomous vehicle. ... The Challenger Deep... is the deepest abyss on Earth at 11,000m-deep, more than 2km (1.2 miles) deeper than Mount Everest is high. At that depth, pressures reach 1,100 times those at the surface."
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I'm impressed with the two guys who did it *manned* in the 60s
from tfa :
In January 1960, Jacques Piccard and Don Walsh made the first and only manned voyage in a Swiss-built bathyscaphe known as the Trieste. The vessel consisted of a 2m-diameter (6ft) steel sphere containing the crew suspended below a huge 15m-long (50ft) tank of petrol, designed to provide buoyancy. During the nine-hour mission, the two men spent just 20 minutes on the ocean floor; enough time to measure the depth as 10,916m (35,813 ft).
Depends - Quote [physorg.com]:"By mimicking a brick-and-mortar molecular structure found in seashells, University of Michigan researchers created a composite plastic that's as strong as steel but lighter and transparent."
I'm impressed with the two guys who did it *manned* in the 60s
from tfa:
In January 1960, Jacques Piccard and Don Walsh made the first and only manned voyage in a Swiss-built bathyscaphe known as the Trieste. The vessel consisted of a 2m-diameter (6ft) steel sphere containing the crew suspended below a huge 15m-long (50ft) tank of petrol, designed to provide buoyancy. During the nine-hour mission, the two men spent just 20 minutes on the ocean floor; enough time to measure the depth as 10,916m (35,813 ft).
Yeah, I remember seeing a special on that when I was younger (like 10 years ago), and I still remember it, because it's such an awesome story. I really suggest that if anyone is bored you look this story up, it's really awesome.
The sad thing is that once they hit the bottom, the sand down there was so fine that it threw up a cloud of it that never cleared during the time that they were there, so they didn't get to see much except for what they saw right before they landed!
Are you sure that's the only time men got down there? I'd not be surprised if the Seaview [wikipedia.org] didn't manage it at least once. After all, that's exactly the type of thing she was built for.
submersibles actually manage to stay at the bottom of the trench for extended lengths of time? Short visits can only tell scientists so much about ordinary conditions. A permanent unmaned observation station could record a much larger data sample. Now all that's left to do is develop technologies that can withstand the pressure and power themselves of sulphur-feeding clamlike tube creatures.
Somebody smarter than myself, please comment on why we need a cable over a distance of 11km? There's a ton of off-the-shelf radio equipment that can easily handle that distance with very high bitrates.
I can imagine two possible problems:
First, the ocean might simply be good at blocking transmissions.
Second, the varying pressures and temperatures might distort a signal to the point where it is unusable. I'm referring to dielectric effects and the fact that the dielectric constant would not be constant in this sort of operation. But would it be "constant-enough"?
First, the ocean might simply be good at blocking transmissions.
Yes salt water is very good at attenuating RF, the higher the frequency the worse it is. Have a look at http://en.wikipedia.org/wiki/Extremely_low_frequency [wikipedia.org] on Wikipedia that highlights some of the difficulties, especially in relation to antenna size. Also at those frequencies you can end up with transmission rates less than one bit per second.
The VLF system used to communicate with Navy Submarines is an example. A message that could be received as a burst from a satellite in 2 seconds can take 20 minutes or more by VLF and that is with 1000 yards of antenna streamed from the boat.
First, the ocean might simply be good at blocking transmissions.
I don't have direct knowledge of the behavior of radio waves in water, but I would strongly guess this.
Even sunlight peters out at depths measured in dozens of feet, and that you need pretty strong lights to illuminate even 10 feet in front of you if you're at the bottom. Going through two miles of water would likely be quite a feat.
Further, I'm pretty sure that the reason water is "blue" is that blue light tends to penetrate better (think looking up from the perspective of a SCUBA diver 20 or 30 feet down), which suggests that longer wavelengths get blocked more, which is exactly the opposite of what you would want for radio penetration.
This is mostly a nitpick, but water is blue because other frequencies of visible light get absorbed and turned into molecular vibrations (or something like that, I never fully understood that mechanic). This is an entirely separate phenomenon from what causes it to attenuate RF signals.
I only bring it up because blue, and even red, light are much higher frequencies than would be used in RF transmissions (10^14 Hz for visible light as opposed to 10^11 at the most for RF).
Because of the electrical conductivity of salt water, submarines are shielded from most electromagnetic communications.
Very low frequency signals can penetrate about 20 meters.
Extremely low frequency signals can be received from deeper but are extremely limited in bandwidth.. and you need to use the whole earth as an antenna, etc.
You got it the first time. Radio transmission is very difficult in the water. You're pretty much limited to ultra low frequency transmission, like the military uses to talk to subs. It's slow, about 1 bit/sec [dtic.mil] and might have problems at extreme depths or in complex topography.
There's active work going on [wirelessfibre.co.uk] with underwater radio. It's really tough to do in salt water. But it's not quite impossible. There's considerable interest in making something that can push data through 100 meters of water depth. Oil industry operations would like to talk to their stuff on the ocean floor.
At longer ranges, there's at least one research project [europa.eu] which claims that there's a transmission window in seawater between 1MHz and 10MHz. They hope to get data across 1KM. That will be useful if it works.
ELF works; the US and the USSR both have used it in the 70-85 Hz band. The trouble with ELF is that the wavelengths are so long at 80Hz that you need an antenna the size of a county.
... the ocean might simply be good at blocking transmissions.
The ocean isn't just good at blocking transmissions. It's ridiculously good at blocking radio waves. If you work the math on this [qsl.net] page, you can see that your basic WiFi transmission (at 2.4 GHz) will experience an attenuation of almost 1700 dB/meter! At that rate you'd get far less than a millimeter of penetration.
Even the lowest frequency short wave bands (1.8 MHz) get 46 dB/meter attenuation. It starts to get possible to receive RF when you get down in the kHz range but of course, your data rate goes to hell.
For underwater communications under a couple hundred meters or so you can use an acoustic modem. Even then, your best data rate is going to be on the order 2400 baud or less.
If you want high speed underwater communications, you gotta use a cable.
It may give us access to 100% of the sea floor, but given the expense of sea exploration, how much will we actually explore? Setting records is nice and all, but it takes time, effort, and money to map the deep sea floor in any kind of detail.
It should be able to take samples and such, but what about repeat dives? The artile was a bit lacking, but hopefully google will turn up the juicy details on this particular little bot....
I would love to see Google Street View of the ocean floor. Who knows what we'll find down there... And it's easy for Google too; no complaints about privacy breach.
I suspect it would be like the time there was a volcano in New Zealand and somebody there set up a web cam people elsewhere could monitor it. Somebody in a different hemisphere took a look and because the scene was black assumed the surrounding area had blown up. Of course they were looking at night and had forgotten the time difference.
I worked on an ROV simulation back in the 90's and we needed to keep track of how many times the ROV turned around because twists accumulate in the cable. At some point you may have to sit in place and spin for a bit to undo the twists. Terrible things happen when the tether gets too twisted.
My uneducated guess is that the cable is so long that you'd wind up with (for example) a CW twist near the top of the cable and a CCW twist near the bottom of the cable - twists at the top wouldn't propagate all the way down.
It's pretty certain that the components are not functionning at 1 atmosphere of pressure. Give or take, the rule of thumb when diving is that the pressure goes up by 1 atmosphere for every 10m of depth. With a depth of 11000m, that's 1100 atmospheres of pressure. That's one of the most reliable methods they use to measure depth, actually.
It's not the outside pressure that causes things to crumple. It's the difference between outside and inside pressures. With that in mind, and keeping in mind that electroni
by Anonymous Coward
on Tuesday June 02, @11:06PM (#28191685)
Uhh. those solid state components you're thinking of tend to have voids in them, e.g. what's under that lid on the CPU.. a bare die and a bunch o' bond wires. Squish city at 1000 Atm.
What about wires? More than enough pressure to push water through the wire using the insulation as a tube.
It is REALLY, REALLY hard to design stuff to work at 1000Atm. What do you use for bouyancy? (Trieste used gasoline.. a liquid that is about the same compressibility as water) Syntactic foam with silica microspheres is fairly popular, because the tiny hollow spheres are pretty strong.
Interestingly, it's harder to design something that won't crush than something that won't explode. That is, building a compressed gas tank to hold 20,000 psi is easier than building one that won't crush under 20,000 psi.
You seem to know a bit about submarines so perhaps you could answer a question that has puzzled me. If you build a submarine like an onion with a hull inside a hull and put pressurized water / air between the two hulls to half the outside pressure would each hull then only need to be strong enough to resist half the external pressure?
I can't see the flaw but it feels wrong because it seems to imply that it would be at least theoretically possible to build a submarine out of sheets of tin-foil as long as there were enough layers and the pressure could be maintained accurately enough.
That idea won't work because it doesn't actually make sense. While it is definitely an interesting question; and one that I was initially puzzled by, I think you will be surprised by how clumsy the intuitive logic that brings us to that conclusion is.
Consider your onion, with two layers, and you are standing between them. To make things simpler, lets assume that instead of water pressure you actually have pressure from weights, and lets also change your onion from spherically shaped shells to just two flat surfaces. For example, you could imagine that you are just standing on an imaginary, levitating sheet of plywood and there is a sheet of plywood above you.
The "water pressure" from above you is say 100 lbs. This is how many weights are on the sheet of plywood above you, and it is as much as you can hold. So you say, lets "pressurize" the intermediate onion layer (you), and you position springs on both sides of you (or you could use water pressure). With this new pressurized layer, you can now withstand twice as much "water pressure" from above you, for a total of 200lbs. But that has nothing to do with how much pressure is being exerted on this imaginary sheet of plywood beneath you.
As you see, you could build a million onion shells and it wouldn't change anything about how much pressure the inner most layer, or the bottom sheet of plywood, must withstand. Indeed, all submarines already use your multiple hull theory, but not in the way you imagine. They all must withstand the pressure from a layer of ocean above them AND a layer of atmosphere above the ocean--the ocean doesn't protect against the atmospheric pressure.
That'll make for one traumatic moment when the lead mermaid tries to surface and bursts open from the tremendous drop in pressure. I don't think my kids would want to see that one.
Are you ready kids? (Score:5, Funny)
Aye aye, Captain!
Re:Are you ready kids? (Score:5, Funny)
I can't hear you!
Parent
Re: (Score:2, Offtopic)
undersea progress (Score:2, Funny)
Re:undersea progress (Score:4, Funny)
You're asking a lot there, buddy. Don't you think they got enough pressure as it is?
Parent
Re:undersea progress (Score:4, Funny)
Parent
Re: (Score:2)
Yea, Dethklok recording their new album and a giant radioactive seahorse.
Re: (Score:3, Funny)
I wonder if my great^8 grandkids (Score:2)
Re:I wonder if my great^8 grandkids (Score:5, Interesting)
I'm impressed with the two guys who did it *manned* in the 60s
from tfa :
In January 1960, Jacques Piccard and Don Walsh made the first and only manned voyage in a Swiss-built bathyscaphe known as the Trieste.
The vessel consisted of a 2m-diameter (6ft) steel sphere containing the crew suspended below a huge 15m-long (50ft) tank of petrol, designed to provide buoyancy.
During the nine-hour mission, the two men spent just 20 minutes on the ocean floor; enough time to measure the depth as 10,916m (35,813 ft).
Parent
Re:I wonder if my great^8 grandkids (Score:4, Funny)
Men had balls in the 60s.
Parent
Re:I wonder if my great^8 grandkids (Score:5, Funny)
Fixed that for you.
Parent
Re:I wonder if my great^8 grandkids (Score:4, Interesting)
Depends - Quote [physorg.com]:"By mimicking a brick-and-mortar molecular structure found in seashells, University of Michigan researchers created a composite plastic that's as strong as steel but lighter and transparent."
CC.
Parent
Re: (Score:2)
Re: (Score:3, Interesting)
Re:I wonder if my great^8 grandkids (Score:5, Interesting)
I'm impressed with the two guys who did it *manned* in the 60s
from tfa :
In January 1960, Jacques Piccard and Don Walsh made the first and only manned voyage in a Swiss-built bathyscaphe known as the Trieste.
The vessel consisted of a 2m-diameter (6ft) steel sphere containing the crew suspended below a huge 15m-long (50ft) tank of petrol, designed to provide buoyancy.
During the nine-hour mission, the two men spent just 20 minutes on the ocean floor; enough time to measure the depth as 10,916m (35,813 ft).
Yeah, I remember seeing a special on that when I was younger (like 10 years ago), and I still remember it, because it's such an awesome story. I really suggest that if anyone is bored you look this story up, it's really awesome.
The sad thing is that once they hit the bottom, the sand down there was so fine that it threw up a cloud of it that never cleared during the time that they were there, so they didn't get to see much except for what they saw right before they landed!
-Taylor
Parent
Re: (Score:3, Funny)
Re: (Score:3, Funny)
Oh yeah? Well, I'm going to be the first man to set foot on the surface of the sun!
Re: (Score:3, Funny)
After getting through the corona, that should feel downright refreshing.
Re:I wonder if my great^8 grandkids (Score:5, Funny)
That's why I'd do it at night.
Parent
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
Will see a craft reach the surface of one of the gaseous giants.
Unlikely, seeing as the gas giant planets don't have surfaces.
All I want to know.. (Score:3, Funny)
Re:All I want to know.. (Score:5, Funny)
Do they have a good pizza/wing place down there?
No, but there's a Starbuck's.
Parent
When will (Score:2, Interesting)
Cable? Why? (Score:5, Interesting)
Somebody smarter than myself, please comment on why we need a cable over a distance of 11km? There's a ton of off-the-shelf radio equipment that can easily handle that distance with very high bitrates.
I can imagine two possible problems:
First, the ocean might simply be good at blocking transmissions.
Second, the varying pressures and temperatures might distort a signal to the point where it is unusable. I'm referring to dielectric effects and the fact that the dielectric constant would not be constant in this sort of operation. But would it be "constant-enough"?
Re:Cable? Why? (Score:4, Informative)
Yes, it just might be. In fact, it is. You see, salt water is conductive.
Parent
Re:Cable? Why? (Score:5, Informative)
Yes salt water is very good at attenuating RF, the higher the frequency the worse it is. Have a look at http://en.wikipedia.org/wiki/Extremely_low_frequency [wikipedia.org] on Wikipedia that highlights some of the difficulties, especially in relation to antenna size. Also at those frequencies you can end up with transmission rates less than one bit per second.
Parent
Re:Cable? Why? (Score:5, Informative)
Parent
Re:Cable? Why? (Score:4, Informative)
First, the ocean might simply be good at blocking transmissions.
I don't have direct knowledge of the behavior of radio waves in water, but I would strongly guess this.
Even sunlight peters out at depths measured in dozens of feet, and that you need pretty strong lights to illuminate even 10 feet in front of you if you're at the bottom. Going through two miles of water would likely be quite a feat.
Further, I'm pretty sure that the reason water is "blue" is that blue light tends to penetrate better (think looking up from the perspective of a SCUBA diver 20 or 30 feet down), which suggests that longer wavelengths get blocked more, which is exactly the opposite of what you would want for radio penetration.
Parent
Re: (Score:3, Informative)
This is mostly a nitpick, but water is blue because other frequencies of visible light get absorbed and turned into molecular vibrations (or something like that, I never fully understood that mechanic). This is an entirely separate phenomenon from what causes it to attenuate RF signals.
I only bring it up because blue, and even red, light are much higher frequencies than would be used in RF transmissions (10^14 Hz for visible light as opposed to 10^11 at the most for RF).
Re:Cable? Why? (Score:4, Informative)
Parent
Re: (Score:2)
Because of the electrical conductivity of salt water, submarines are shielded from most electromagnetic communications.
Very low frequency signals can penetrate about 20 meters.
Extremely low frequency signals can be received from deeper but are extremely limited in bandwidth.. and you need to use the whole earth as an antenna, etc.
Re: (Score:3, Informative)
Hence, the tether.
Underwater radio (Score:5, Informative)
There's active work going on [wirelessfibre.co.uk] with underwater radio. It's really tough to do in salt water. But it's not quite impossible. There's considerable interest in making something that can push data through 100 meters of water depth. Oil industry operations would like to talk to their stuff on the ocean floor.
At longer ranges, there's at least one research project [europa.eu] which claims that there's a transmission window in seawater between 1MHz and 10MHz. They hope to get data across 1KM. That will be useful if it works.
ELF works; the US and the USSR both have used it in the 70-85 Hz band. The trouble with ELF is that the wavelengths are so long at 80Hz that you need an antenna the size of a county.
Parent
Re:Cable? Why? (Score:5, Informative)
... the ocean might simply be good at blocking transmissions.
The ocean isn't just good at blocking transmissions. It's ridiculously good at blocking radio waves. If you work the math on this [qsl.net] page, you can see that your basic WiFi transmission (at 2.4 GHz) will experience an attenuation of almost 1700 dB/meter! At that rate you'd get far less than a millimeter of penetration.
Even the lowest frequency short wave bands (1.8 MHz) get 46 dB/meter attenuation. It starts to get possible to receive RF when you get down in the kHz range but of course, your data rate goes to hell.
For underwater communications under a couple hundred meters or so you can use an acoustic modem. Even then, your best data rate is going to be on the order 2400 baud or less.
If you want high speed underwater communications, you gotta use a cable.
Parent
Nice, but what does it do? (Score:3, Insightful)
It may give us access to 100% of the sea floor, but given the expense of sea exploration, how much will we actually explore? Setting records is nice and all, but it takes time, effort, and money to map the deep sea floor in any kind of detail.
It should be able to take samples and such, but what about repeat dives? The artile was a bit lacking, but hopefully google will turn up the juicy details on this particular little bot....
Re: (Score:3, Funny)
I would love to see Google Street View of the ocean floor. Who knows what we'll find down there... And it's easy for Google too; no complaints about privacy breach.
Re:Nice, but what does it do? (Score:4, Funny)
Parent
Re:Nice, but what does it do? (Score:5, Funny)
They are getting sued by SCO though, for violating their patent for sinking to the lowest depths possible.
Parent
So then they were the first customers (Score:2)
Twists in the fiber optic cable (Score:5, Insightful)
I worked on an ROV simulation back in the 90's and we needed to keep track of how many times the ROV turned around because twists accumulate in the cable. At some point you may have to sit in place and spin for a bit to undo the twists. Terrible things happen when the tether gets too twisted.
Re: (Score:3, Insightful)
My uneducated guess is that the cable is so long that you'd wind up with (for example) a CW twist near the top of the cable and a CCW twist near the bottom of the cable - twists at the top wouldn't propagate all the way down.
Already been done? (Score:4, Funny)
Re: (Score:3, Interesting)
It's pretty certain that the components are not functionning at 1 atmosphere of pressure. Give or take, the rule of thumb when diving is that the pressure goes up by 1 atmosphere for every 10m of depth. With a depth of 11000m, that's 1100 atmospheres of pressure. That's one of the most reliable methods they use to measure depth, actually.
It's not the outside pressure that causes things to crumple. It's the difference between outside and inside pressures. With that in mind, and keeping in mind that electroni
Re:how hard can it be? (Score:5, Interesting)
Uhh. those solid state components you're thinking of tend to have voids in them, e.g. what's under that lid on the CPU.. a bare die and a bunch o' bond wires. Squish city at 1000 Atm.
What about wires? More than enough pressure to push water through the wire using the insulation as a tube.
It is REALLY, REALLY hard to design stuff to work at 1000Atm. What do you use for bouyancy? (Trieste used gasoline.. a liquid that is about the same compressibility as water) Syntactic foam with silica microspheres is fairly popular, because the tiny hollow spheres are pretty strong.
Interestingly, it's harder to design something that won't crush than something that won't explode. That is, building a compressed gas tank to hold 20,000 psi is easier than building one that won't crush under 20,000 psi.
Parent
Re:how hard can it be? (Score:5, Interesting)
You seem to know a bit about submarines so perhaps you could answer a question that has puzzled me. If you build a submarine like an onion with a hull inside a hull and put pressurized water / air between the two hulls to half the outside pressure would each hull then only need to be strong enough to resist half the external pressure?
I can't see the flaw but it feels wrong because it seems to imply that it would be at least theoretically possible to build a submarine out of sheets of tin-foil as long as there were enough layers and the pressure could be maintained accurately enough.
Parent
Re:how hard can it be? (Score:4, Informative)
Parent
Re:What They Aren't Telling Us... (Score:5, Funny)
That'll make for one traumatic moment when the lead mermaid tries to surface and bursts open from the tremendous drop in pressure. I don't think my kids would want to see that one.
Parent