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Fluid-Filled, Robotic, Ocean-Bottom Explorer

A low-buget, unmanned, undersea vehicle
  [vote for,

Some fish can handle the conditions at the bottom of the oceans, so why not copy them? Fish are composed of fluid-filled chambers (cells) so, rather than a tough metal shell like most (or all?) deep-sea craft, this one has a thick, transparent, rubbery skin which is filled with a carefully chosen fluid. The fluid should:
* be transparent and colorless.
* be non-conductive.
* have low viscosity.
* have a freezing point well below that of the temperatures it could encounter.
* have a low dielectric constant to reduce interference with high-frequency circuits.
* be harmless to the mechanical and electronic parts, including digital cameras.
* have a refractive index which can be accommodated by the optical components.

The skin could be around one centimeter thick and be tear-resistant enough.

"Windows" for optics could be embedded into the skin as required.

Such robots should be within the budgets of many do-it-yourselfers.

Note: Off-the-shelf components might not be able to handle the conditions in the Marianis Trench.

Alvin, Jan 11 2013

Alvin http://www.flickr.c...551@N03/5858876256/
I thought you created this account just for this invention [fishboner, Jan 11 2013]

Critical temperatures and pressures http://en.wikipedia...selected_substances
Relevant to buoyancy. [8th of 7, Jan 12 2013]

Computer system immersed in Mineral Oil http://www.business...o-2016-7/?r=AU&IR=T
[AusCan531, Apr 24 2018]


       Why does it need a skin at all?
DrCurry, Jan 11 2013

To keep out the sea water. Sea water could damage mechanical parts and interfere with the electronics.

No, I've never heard of that before. This invention doesn't carry passengers.
Alvin, Jan 11 2013

       I think the idea is that you don't need a flexible skin if it is filled with an incompressible fluid. A metal shell with glass windows could might have enough flexibility to deal with thermal expansion, etc. If not, you could have a small diaphram or piston, allowing most of the device to be more durable and easier to open and close.
scad mientist, Jan 11 2013

       As a first pass at what liquid to use I found 3M FC-70. It is a clear liquid often used for immersing electronics for cooling.   

       3M has pretty complete specs on their web site, including:
Refractive index = 1.303 (water = 1.33)
Dielectric Strength 40 kV, 0.1" gap
Dielectric Constant 1.98
Electrical Resistivity 2.3 x 10^15 ohm cm
Coefficient of Expansion 0.0010 / °C
Kinematic Viscosity 12 centistokes
Absolute Viscosity 24 centipoise
Boiling Point (1 atm) 215°C
Pour Point -25°C

       It's mostly non-harmful. It won't kill you or the ozone layer, but could cause global warming, so it should be recycled. At a price of $295/kg you'll probably be fairly careful with it...   

       I assume there could be better/cheaper options, but this one looks like it could work.
scad mientist, Jan 11 2013

       I think you'd still want a metallic skin, if for no other reason than to prevent impacts or scrapes from being a problem, but I like the idea of an (non-conductive) oil filled metal craft with a small balloon open to the atmosphere/water to balance pressure.   

       You would need to select components that didn't have cavities in them, which you should be able to deal with for electronics, but optics would get a little challenging. Oil filled lenses are definitely possible, but they would need to be custom made because I don't think you'll find a fluid to match air's index of refraction. Likewise motors are going to have a much higher friction load if the rotor is oil filled.   

       Pneumatics would be right out, but it should be possible to make hydraulics work.
MechE, Jan 11 2013

       It might not be obvious enough from the article, but the idea is to have no shell at all. It would just be a robot with a skin over it which is filled completely with an inert fluid. There would be no more casing for the robot than one made for operation on land.
Another point to keep in mind is that it's intended to be usable in the deepest water on the planet, (several miles deep).
Alvin, Jan 11 2013

       I'm not going to imply that this idea is baked, or widely known to exist, or even that it's been done, but my (admittedly faded) memories of when I made underwater electrical connectors in the eighties tell me that there have been efforts made towards fluid-soaked electrical underwater systems.
normzone, Jan 11 2013

       I assumed that this was already done, but I guess it's not, so [+].
MaxwellBuchanan, Jan 11 2013

       Transformer oil is cheap, fairly inert, and non-conductive.   

       Something like a bag-in-box design would be attractive.   

       Electric motors would need to be low-revving so as not to lose too much power from churning fairly viscous oil.   

       Illumination could be achieved with banks of LEDs.   

       Cameras would be a problem … you'd need a lens stack designed to be filled with a suitable incompressible liquid, rather than air.   

       Batteries? No airspace permitted … wet cell batteries could be" flooded up" with oil over the electrolyte and then each cell could be vented into a separate small bladder. The oil would have to be unreactive with acid.   

       Manipulators could use closed circuit hydraulics working on differential pressure; ambient pressure would be irrelevant.   

       Any thoughts on buoyancy control? Slight positive buoyancy coupled with releasable inert ballast, e.g. sand, gravel?
8th of 7, Jan 11 2013

       Banjos, bees, custard?
normzone, Jan 11 2013

       Why have any liquid at all? if the robot is solid just vacuum seal it in a bag or even just lacquer every part. Drop it to the bottom of the sea. Attach non inflated balloons and a co2 cartridge for retrieval purposes.
Brian the Painter, Jan 12 2013

       At deep sea pressures, gasses don't exist. You need to make it inherently buoyant with non-foamed plastics or oil reservoirs, and then drop weights to make it surface.
Kansan101, Jan 12 2013

       Bring down an liquid filled canister. Attempt to pump out some liquid causing a vacuum to form in the canister.   

       Kevlar bag filled with C4 explosives. Don't know if it would work, but fun as hell to watch!   

       [edit] Normally liquid CO2 has to be at a depth of 10,000 feet (3,000 meters) for it to be dense enough not to rise.
Brian the Painter, Jan 12 2013

       Brian the Painter
//Why have any liquid at all?//
It might be possible to eliminate the liquid, but I expect it would be hard to design mechanical parts that could function when covered with a solid substance.

       Added later:
scad mientist
A fluid costing $295/kg would probably only be used by well-funded missions. Hopefully, something like gasoline or other boat fuel would be suitable so that after a mission, it could be drained out and used to power the boat back to shore.
Alvin, Jan 12 2013

       // At deep sea pressures, gasses don't exist //   

       Incorrect. The water is very cold, but still much hotter than the critical temperature of many common gases- that is, the temperature above which they won't liquefy, no matter how much pressure is applied.   

       Hydrogen, Helium, Nitrogen, Oxygen are all permanent gases at deep-sea temps.   

8th of 7, Jan 12 2013

       Man, you caught me talking out of my wazzoo. Damn it.
Kansan101, Jan 12 2013

       Don't mention it. It's just a talent we happen to have.   


       A little impromptu experimentation has demonstrated that a standard PC motherboard will operate perfectly well when completely submerged in paraffin. The hard disk, however, was not immersed.   

       Paraffin has a low viscosity which would not unduly affect low speed motors. Since there is no free oxygen, there is no fire risk when submerged. And paraffin would provide some buoyancy as a useful side effect.
8th of 7, Jan 12 2013

       I thought you were talking about solid paraffin until you mentioned viscosity. Actually, solid paraffin could be a good potting material for the electronics of the submarine. It melts off easily for maintenance, too, and if it doesn't all drip off, your soldering iron will just melt through it harmlessly.
notexactly, Apr 22 2018

       In liquid form it can be drained off and the board cleared in a few seconds with a compressed air jet; it even gets the liquid out of the connectors while still assembled. No need for any melting.
8th of 7, Apr 22 2018

       PC systems are already being submersed in vegetable oil, mineral oil and proprietary blends for cooling purposes. See Linky.
AusCan531, Apr 24 2018


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