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Earth Transportation Science

Research Vehicle Reaches the Bottom of the Ocean 165

Posted by kdawson from the ah-ooo-gah dept.
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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Research Vehicle Reaches the Bottom of the Ocean More

Research Vehicle Reaches the Bottom of the Ocean

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  • Are you ready kids? (Score:5, Funny)

    by Anonymous Coward on Tuesday June 02, 2009 @09:47PM (#28191125)

    Aye aye, Captain!

  • Wow, that is great. Hope they find some interesting stuff down there. Maybe some animals we didn't even know existed. Next up: Building the Seaquest
  • Will see a craft reach the surface of one of the gaseous giants. Now that would be a helluva science and engineering project.

  • All I want to know.. (Score:3, Funny)

    by nanospook ( 521118 ) on Tuesday June 02, 2009 @09:54PM (#28191205)
    Do they have a good pizza/wing place down there?

  • Only Two Vehicles (Score:1, Funny)

    by Anonymous Coward

    Plus all the boats that sank.

  • 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.

  • Cable? Why? (Score:5, Interesting)

    by Lord Byron II ( 671689 ) on Tuesday June 02, 2009 @10:06PM (#28191293)

    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)

      by John Hasler ( 414242 ) on Tuesday June 02, 2009 @10:10PM (#28191337) Homepage

      First, the ocean might simply be good at blocking transmissions.

      Yes, it just might be. In fact, it is. You see, salt water is conductive.

    • Re:Cable? Why? (Score:5, Informative)

      by commlinx ( 1068272 ) on Tuesday June 02, 2009 @10:11PM (#28191343) Homepage Journal

      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.

      • Re:Cable? Why? (Score:5, Informative)

        by BCW2 ( 168187 ) on Tuesday June 02, 2009 @10:17PM (#28191401) Journal
        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.
      • Yeah, try explaining to a government official that you need more funding because you're using elves to talk to your submarine. :P

    • Re:Cable? Why? (Score:4, Informative)

      by EvanED ( 569694 ) <evaned@g[ ]l.com ['mai' in gap]> on Tuesday June 02, 2009 @10:13PM (#28191357)

      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.

    • Re: (Score:2)

      by QuantumG ( 50515 ) *

      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)

      by ColdWetDog ( 752185 )
      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.

      Hence, the tether.

      • Underwater radio (Score:5, Informative)

        by Animats ( 122034 ) on Wednesday June 03, 2009 @12:10AM (#28192049) Homepage

        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.

        • There's active work going on 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.

          Since salt ware is conductive, couldn't you simply use electric discharge? Put a metal rod on the water and discharge an electric pulse through it; it'll expand in a spherical manner (or half-sphere if it ori

        • That's interesting although it seems like it is severely distance limited. Still need the tether if you want to go deep.

          Of course, the antenna length issue is less of a problem in the huge volume of ocean. A wire several thousand feet long strung behind a sub or rig isn't too hard as long as you stay away from twisty canyons, wrecks and sharks with lasers.x

      • Re: (Score:2, Interesting)

        by InfoJunkie777 ( 1435969 )
        I saw on the Science Channel show "Brink" about experimental LASER communication for close-range ship or sub-to-sub communications or sub to aircraft communications. Here is a link to the people trying to perfect it: http://www.janes.com/extracts/extract/jav/jav_0184.html [janes.com]. It seems to hold some promise.

    • Re:Cable? Why? (Score:5, Informative)

      by ssimmons ( 22842 ) on Tuesday June 02, 2009 @10:56PM (#28191605)

      ... 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.

      • Re: (Score:2, Interesting)

        by Earthquake Retrofit ( 1372207 )
        OK that tears it. I'm turning in my tinfoil hat for a saltwater Stetson.

        Steve

    • Re: (Score:2)

      by LWATCDR ( 28044 )

      Water blocks radio. If Radio worked don't you think they would have used it?
      The only way to send radio under water is to use ELF extremely low frequency radio. http://en.wikipedia.org/wiki/Extremely_low_frequency [wikipedia.org]
      As you can see the data rate is in bits per minute...

  • Nice, but what does it do? (Score:3, Insightful)

    by vampire_baozi ( 1270720 ) on Tuesday June 02, 2009 @10:08PM (#28191311)

    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)

      by tsa ( 15680 )

      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: (Score:2)

      by Mal-2 ( 675116 )

      It is best to explore and deliberately push the boundaries of these craft. You never know when they might be required urgently for something like the Air France Flight 447 black box search, and it is best to break them when there is time to fix them, rather than when they just have to work.

      Mal-2

  • Not to belittle the achievement, but how hard can it be to make something that won't crumple? Does every bit of equipment need to be at 1 atmosphere for it to function? Are there no solid-state components?

    • Re: (Score:3, Interesting)

      by KillerBob ( 217953 )

      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)

        by Anonymous Coward on Tuesday June 02, 2009 @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.

        • Re:how hard can it be? (Score:5, Interesting)

          by squoozer ( 730327 ) on Wednesday June 03, 2009 @03:37AM (#28193087)

          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.

          • Re: (Score:2)

            by HopeOS ( 74340 )
            I'm not an expert, but my first thought is that the problem lies with "pressurized water/air". Water does not compress well, and even if it did, the water/air mixture would separate leaving a void. By comparison, a rigid foam would solve that, and laminated sheets of foam are probably indistinguishable from thick foam when uniform pressure is applied. So the idea has merit, but possibly with different materials. I'm thinking of rigid cells containing a liquid for neutral buoyancy. -Hope

          • You are right. Your idea should work. However, designers until now have always chosen to have a single hull (which also consists of multiple layers, beams and parts that altogether withstand the pressure).

            I am not sure that tin foil is your ideal material, because it should at least be able to keep itself up in a tubular shape, and tin foil isn't able to do that when the tube is the size of a submarine. (In other words: tin foil doesn't need water or a pressure difference across a hull to collapse... it doe

          • Re:how hard can it be? (Score:4, Informative)

            by Tarquin_1 ( 1568757 ) on Wednesday June 03, 2009 @09:48AM (#28195819)
            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.

            • You're assuming really flexible hulls.

              Would it make any difference to a normal sub if you had a steel chamber containing a vacuum inside the crew area? Or to the vaccum chamber?
              Nope. The sub still has the same pressure inside, so the vaccuum chamber still has the same pressure on the outside. Neither sees any difference.

            • Thank you I now see the error in my thinking which I was fair certain must be there since it results in an absurd situation when taken to the limit. It's an interesting reason ing puzzle though.

            • 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.

              Come again?

        • Re: (Score:2)

          by LWATCDR ( 28044 )

          "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."
          That is because an air tank is loaded in tension and not in compression. Most material is stronger in tension than compression. Cement is one of the few that isn't. If fact the trick of build light strong anything is usually figuring out how to put convert the loads to tension.

        • Re: (Score:2)

          by LWATCDR ( 28044 )

          Just use vegetable oil for buoyancy. Actually I have no idea if it has the same compressibility as water or if it is light enough. If I remember correctly the Trieste used aviation gasoline. You could never do that today because it is such nasty stuff. Some subs even used mercury for trim since they could pump it back and forth to change the pitch of the sub.
          Building any type of sub is just hard. Trying to figure out how to build any type of hull penetrations for a sub like that makes my head hurt.

      • Isn't it an option to remove the difference between outside and inside?

        Is it so hard to build electronic components that:
        - Are individually insulated from the surrounding water.
        - Have no internal compressible parts.

        You'd then be able to let the water in. No pressure difference, no crunchy toy.

  • to the walmart setup down there by one of the previous vehicles.

  • "They said it was hauled from the Challenger Deep, but I'm positive that beast never swam in terrestrial waters until a week ago."

  • Twists in the fiber optic cable (Score:5, Insightful)

    by FranTaylor ( 164577 ) on Wednesday June 03, 2009 @03:05AM (#28192923)

    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:2)

      by ymgve ( 457563 )

      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.

      Why aren't you doing the un-spinning at the top of the cable? Seems like it would be better than spinning around at the bottom.

      • Re: (Score:3, Insightful)

        by An ominous Cow art ( 320322 )

        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.

  • You know it is interesting that we have sent a sub down there, but it would have been cool to also send down tech that could record any sealife down there on webcam...and place beacons per each say 1000ft to be able to keep sending commands down to each camera to be able to control their movement...pan right up down...etc... We were able to send 2 rovers to the moon, could we not just do something to leave behind to record, so we don't have to keep going down there every 11 years...

  • Already been done? (Score:4, Funny)

    by Lost Penguin ( 636359 ) on Wednesday June 03, 2009 @09:02AM (#28195167)
    Didn't the Titanic already make this journey? /Oh, you meant "and returned". //My bad...

  • Granted, it wasn't he really deep parts.

  • In related news, researchers have also discovered who actually lives in a pineapple under the sea.

    News at 11.

  • So, did they see the plug?

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