submersible craft pressure problem

[dragonstar57]

if you have a Remote controlled submersible with no empty space in it will pressure be a problem?

is it possible for a hobyiest design to be able to withstand pressures of 681psi?

Edited November 8, 2010 by dragonstar57

[CaptainPanic]

From the description that you give, I see no problem yet.

If there is no "empty space", I guess you have filled the whole thing up with some liquid (pretty tough to do that with a solid - those almost always contain pockets of gas somewhere, which will make it implode in the end).

Liquids are often considered incompressible, and I think it's a safe assumption that you can go to pressures of 47 bar (or about 470 meters!!!) if there is nothing that can be compressed.

 

But why the hell would you want to build something like that?

 

The description leaves a lot of open questions. Like: how are you going to work on the buoyancy? Are you just gonna attach it to a rope? Or should it float at nearly 500 meters under the sea by itself (that's really difficult)??

[vordhosbn]

I am not sure that electronic components in the submarine's circuitry will be able to function properly under such pressure. In most el. component specification, standard atmospheric pressure is assumed, and that's the pressure it's tested on.

[insane_alien]

I am not sure that electronic components in the submarine's circuitry will be able to function properly under such pressure. In most el. component specification, standard atmospheric pressure is assumed, and that's the pressure it's tested on.

 

as long as it's nothing complex(just some batteries, a motor and i suppose a few actuators) then it should be fine.

[vordhosbn]

Well, "Remote controlled submersible" implies both control and communication module. At least some small electronic circuitry is required, imo.

[insane_alien]

remote control for that depth means a tether with some signalling wires attached.

 

radio to that depth is not really feasible.

 

i suppose some sort of sonic communication system could be utilised but the lag would be quite large.

[vordhosbn]

To state what's bothering me more clearly - if the vessel is filled with inert dielectric fluid, rather than air with 1 atm pressure, the electronic components inside will be experiencing essentially the same hydrostatic pressure, as the vessel itself.

This will no doubt at least interfere with their normal characteristics, if not damage them permanently.

 

I don't understand if you don't agree with the above statement regarding the inoperability of the electronic components under high hydrostatic pressure, or rather with the premise that the vessel needs electronic components?

Edited November 11, 2010 by vordhosbn

[insane_alien]

well, if you use solenoids for the control surface actuators and a normal electric motor for power then the presence of the nonconductive fluid will not hinder them and the solid bits are uniformly solid so the pressure won't affect them.

 

if owever you want to stick something complex on it such as a camera or even a computer, then that is going to have to be in a pressure vessel otherwise your capacitors will implode

[InigoMontoya]

I'm a bit puzzled.... Assuming we're talking about a reasonably small model, why the requirement for filled with fluid? Those pressures aren't particularly high if you're building on a small scale.

[Newbies_Kid]

why filled with liquid? why don't just throw a brick tied with a ballast tank into the sea?

Edited November 21, 2010 by Newbies_Kid

[Externet]

if you have a Remote controlled submersible with no empty space in it will pressure be a problem?

 

Should not be a problem

 

is it possible for a hobyiest design to be able to withstand pressures of 681psi?

 

Not at all. Fill any bottle fully with non-compressible parts of whatever and all will survive 681psi.

[dragonstar57]

remote control for that depth means a tether with some signalling wires attached.

 

radio to that depth is not really feasible.

 

i suppose some sort of sonic communication system could be utilised but the lag would be quite large.

my idea for that would be to make a small surface craft that would be programed to stay above the submersible at all times (or near it) with a laser light (not a burning laser) that would pulse the commands to a receiver on the vessel. and the surface vessel could use radio to the controller

 

 

To state what's bothering me more clearly - if the vessel is filled with inert dielectric fluid, rather than air with 1 atm pressure, the electronic components inside will be experiencing essentially the same hydrostatic pressure, as the vessel itself.

This will no doubt at least interfere with their normal characteristics, if not damage them permanently.

 

I don't understand if you don't agree with the above statement regarding the inoperability of the electronic components under high hydrostatic pressure, or rather with the premise that the vessel needs electronic components?

the vessel does need electronics. so somehow "shielding" them from the pressure would be necessary

why filled with liquid? why don't just throw a brick tied with a ballast tank into the sea?

while a ballast tank is a good idea a brick....is just a brick Edited November 27, 2010 by dragonstar57

[insane_alien]

my idea for that would be to make a small surface craft that would be programed to stay above the submersible at all times (or near it) with a laser light (not a burning laser) that would pulse the commands to a receiver on the vessel. and the surface vessel could use radio to the controller

 

thats not going to work. go take a dive under water some time, you'll notice that you can't see very far. this is because water doesn't transmit light very well over long distances. heck, you can even get the effect of the light scattering in some larger swimming pools.

 

there's a reason even military subs have to go to periscope depth to communicate(with the exception of one way ELF radio which can work near the surface but not at any significant depth)

 

you either have a tether or you have it autonomous or you have it very close to the surface.

 

and no, you're not going to be able to build an ELF antenna, the transmission cables need to be on the scale of a few kilometers.

 

 

the vessel does need electronics. so somehow "shielding" them from the pressure would be necessary

while a ballast tank is a good idea a brick....is just a brick

 

 

then your best bet is to keep the electronics simple, small and sealed inside the thickest piping you can find. also, pressurising the pressure vessel with a few (no more than 5) bars of nitrogen would help it suffer the pressures a bit better.

[dragonstar57]

 

you either have a tether or you have it autonomous or you have it very close to the surface.

 

would the weight of the tether not make that unfeasible?

if not why could the laser not be replaced with a fibber optic?

 

 

 

then your best bet is to keep the electronics simple, small and sealed inside the thickest piping you can find. also, pressurising the pressure vessel with a few (no more than 5) bars of nitrogen would help it suffer the pressures a bit better.

that basically rules out autonomous unless a small computer programed to take the craft to what ever "way points" that are set up is "simple and small" Edited November 27, 2010 by dragonstar57

[InigoMontoya]

would the weight of the tether not make that unfeasible?

if not why could the laser not be replaced with a fibber optic?

You can make the tether neutrally bouyant; or very close to. And yes, you could use fiber optics.

 

that basically rules out autonomous unless a small computer programed to take the craft to what ever "way points" that are set up is "simple and small"

Depends on what you're trying to do. It could be as simple as a gyro to keep it pointed in the right direction with a depth sensor that blows the ballast tanks (or releases the brick, or whatever) when it hits a certain depth. I mean, hey, the first heat seeking missiles didn't have computers in them (at least, not by our current definitions).... Whether or not a full blown computer is required depends largely upon what you're trying to do and how clever you are.

[insane_alien]

Depends on what you're trying to do. It could be as simple as a gyro to keep it pointed in the right direction with a depth sensor that blows the ballast tanks (or releases the brick, or whatever) when it hits a certain depth. I mean, hey, the first heat seeking missiles didn't have computers in them (at least, not by our current definitions).... Whether or not a full blown computer is required depends largely upon what you're trying to do and how clever you are.

 

quoted for truth.

 

for instance, you can make autonomous line following robots out of a light sensor and some resistors. nothing so complicated as a microcontroller. autonomous does not automatically mean complex. it just means it goes down, does some simple function till it either goes too deep or it runs low on power then comes up.

 

if you wanted it to be autonomous and do something complex like pick up some samples of the seabed or navigate its way into a crevass and back out againthen it would require some more complex logic that would necessitate a computer but i doubt you're building something with that complexity anyway.

[dragonstar57]

i was thinking of something that go to the bottom of the deepest lake i know of (lake superior on the us Canadian border) drive around collect basic video and come surface without damage to the system

[CaptainPanic]

i was thinking of something that go to the bottom of the deepest lake i know of (lake superior on the us Canadian border) drive around collect basic video and come surface without damage to the system

Good post. That's what engineers like: just a simple description of what needs to be done. This removes some unnecessary boundary conditions, and makes it possible to "think outside the box".

So, the main question is: what is the main goal of the project? To build the submersible? Or to get footage from the bottom of that lake? From your last post, I conclude that the goal is to make a video of the monsters of the deep in Lake Superior.

 

First of all, I really don't see the point of trying to make a submersible that is autonomous for this task... The practical problems are numerous (battery life to get 40 miles from the shore is already an issue - the buoyancy, the control systems, the balancing... you're looking at years of development probably). I'll just tell you what I would do:

 

You need to get a camera and a lamp to about 400 meter deep, and 60 kilometers (40 miles) off shore into a fresh water lake. The lake, according to youtube fishing videos is safe for relatively small boats (on a calm day)... I'd advise to just waterproof the video camera and the lamp. To attach them to a rope. Attach some weight (a brick). Sink it from a boat into the lake, straight down). Get the video. Pull it back up. Move the boat. Repeat.

 

Getting a video camera which is waterproof for 40 bars of water should be your only concern... and frankly, I would just buy one. That's so much easier than waterproofing a regular camera yourself.

 

I'm really sorry that I write absolutely nothing at all that involves any tinkering in the garage, playing with glue, soldering parts... I advise you to buy a camera. Add some weight... get a boat... and start filming.

 

I think it's much more realistic than building an autonomous submersible camera to investigate the largest lake in the world.

[dragonstar57]

Good post. That's what engineers like: just a simple description of what needs to be done. This removes some unnecessary boundary conditions, and makes it possible to "think outside the box".

So, the main question is: what is the main goal of the project? To build the submersible? Or to get footage from the bottom of that lake? From your last post, I conclude that the goal is to make a video of the monsters of the deep in Lake Superior.

i had not intended the lake to be the purpose but the test of the system.

i chose that test so it could handle the highest possible pressure that might be encountered in fresh water running.

this submersible is meant as the basic .1 version where various other functions would be added in later models.

[dragonstar57]

So, the main question is: what is the main goal of the project? To build the submersible? Or to get footage from the bottom of that lake? From your last post, I conclude that the goal is to make a video of the monsters of the deep in Lake Superior.

the goal us to build the submersible Lake Superior was an example used because it would have the most extreme conditions that could be encountered in fresh water.

and while there are no "monsters" i have heard that at some depths fish start to not have eyes that would be worth seing

[PaulS1950]

Electronics are not really a problem as circuitry can be epoxy encapsulated and then immersed in the same liquid as the rest of the craft.

If you use a ballast tank then you will have an air filled chamber that can implode and the vessel has to be heavier than water. It might be easier to use small weights like BBs that can be dropped from an "open" tank so that as the BBs are lost the water can flow in. That way it will decend but can surface just by releasing the BBs. I am unsure how a motor could be made to work but if it was looded in a separate compartment with a high dielectric fluid it could be made to work.

Using ultra-violet lasers you can extend the range for communication but it is still limited. Sound travels fast enough in water that using coded tones in the infra-sonic range might be usable for signals. (left, right, up, down and surface)

[dragonstar57]

Electronics are not really a problem as circuitry can be epoxy encapsulated and then immersed in the same liquid as the rest of the craft.

If you use a ballast tank then you will have an air filled chamber that can implode and the vessel has to be heavier than water. It might be easier to use small weights like BBs that can be dropped from an "open" tank so that as the BBs are lost the water can flow in. That way it will decend but can surface just by releasing the BBs. I am unsure how a motor could be made to work but if it was looded in a separate compartment with a high dielectric fluid it could be made to work.

Using ultra-violet lasers you can extend the range for communication but it is still limited. Sound travels fast enough in water that using coded tones in the infra-sonic range might be usable for signals. (left, right, up, down and surface)

then could it use a single sonic tone that would be like Morse code but transmuting binary code??

[Grouchy Hermit]

Sounds to me like your getting ready to lose your camera at the bottom of a lake. A tether sound like a good idea.

To get a window for the camera to not leak would be the hard part. Maybe you could include an area in the bottom to collect leakage and a pump to pump it out.

Do the math for me.....what is the psi at that dept....pipe is rated at psi. Its rated for explode, I would say it would take more to implode because of the arch.

Even if you could keep the electronics dry and safe you may still have to cut a hole in the hull for them to work your controls and this is yet another leak.

Your body has no empty space in it yet if you go to deep it will kill you. If the object is filled with fluid would the psi not just be transfered to whatever was inside the fluid. Unless all it had in it was fluid....fluid can carry energy....pump fluid down a tether line and use it for both energy and control.....but you would still need the camera...Maybe you could run fiber optics so the camera could stay topside.....but then you would not need a sub......huh.....let me think...spinning........aaahhhh

[dragonstar57]

Sounds to me like your getting ready to lose your camera at the bottom of a lake. A tether sound like a good idea.

To get a window for the camera to not leak would be the hard part. Maybe you could include an area in the bottom to collect leakage and a pump to pump it out.

Do the math for me.....what is the psi at that depth

about 681psi (did you read the op?)

[InigoMontoya]

[D'oh! Posted in wrong thread! Moderators, feel free to delete.]

Edited February 18, 2011 by InigoMontoya