[dentstudent (OP)]

We are gradually building and expanding the space station, and beginning the long process of manned inter-planetary travel to Mars. Is the concept of human existance underwater null and void?

[lyner]

Probably not -but don't hold your breath boom boom!

[another_someone]

We are gradually building and expanding the space station, and beginning the long process of manned inter-planetary travel to Mars. Is the concept of human existance underwater null and void?

Why should one preclude the other?

OK, I suppose the question is whether you are comparing like with like - we already survive very well underwater (just look at submarines and scuba diving) - at present, our projected human exploration of Mars world not go further in allowing us to survive on Mars than a submarine will allow us to survive underwater.

[Soul Surfer]

Experiments have been carried out with an underwater "lung" using a large surface area of permeable membrane that allows gas to pass betwen the water and air that would allow someone to breathe underwater continuously but the device is rather large and not easily portable as a backpack.  Small mammals have been kept "underwater" indefinitely using this technology.

[paul.fr]

we already survive very well underwater (just look at submarines and scuba diving) - at present

I think survive is all we do, you can not call it living. When i went to join the navy, onboard submarines you were paid an extra £200 because of the conditions.

[Karen W.]

My husband says the same from when he was in the Navy .. It was difficult at best!

[ukmicky]

Living underwater is in some ways harder than living in space, they say we know more about the surface of the moon than we do about the  bottom of the oceans which basically tells us how difficult an enviroment it is to survive in.

[another_someone]

Living underwater is in some ways harder than living in space, they say we know more about the surface of the moon than we do about the  bottom of the oceans which basically tells us how difficult an enviroment it is to survive in.

Can't say it is more difficult to survive underwater than in space - there have been orders of magnitude more man hours spent surviving underwater than in space.  What is true is that visibility in space is better, which is why we know more about the surface of the Moon (but not the surface of Venus) than the bottom of the ocean.

[ukmicky]

Living underwater is in some ways harder than living in space, they say we know more about the surface of the moon than we do about the  bottom of the oceans which basically tells us how difficult an enviroment it is to survive in.

Can't say it is more difficult to survive underwater than in space - there have been orders of magnitude more man hours spent surviving underwater than in space.  What is true is that visibility in space is better, which is why we know more about the surface of the Moon (but not the surface of Venus) than the bottom of the ocean.

The reason we have spent more hours under water as its a lot easier to get to the sea than space if we could find an easy way to transport us into space and to travel through it then that situation would change.

Also visibility in water isn't really a problem deep down as the water tends to be crystal clear all you need to do is bring some lights with you and its amazing how far they can see.


The problem with water is the pressure which  far harder to survive in. A vacuum is childs play compared to the presure of the deep.

[another_someone]

The reason we have spent more hours under water as its a lot easier to get to the sea than space if we could find an easy way to transport us into space and to travel through it then that situation would change.

There is also the problem that in space you need to take your means of survival with you, whereas this may have been a problem for early submariners (but, as you say, closer proximity makes it easier to carry what you need to where you need it); but now that we have nuclear powered submarines that are capable of extracting oxygen from water, and desalinating the sea; two major consumables that humans need to survive are readily available to hand without needing to be carried from home base.  Also, it is important that heat can be much more easily dissipated underwater than in space, thus making thermodynamic energy sources much easier to use.

Also visibility in water isn't really a problem deep down as the water tends to be crystal clear all you need to do is bring some lights with you and its amazing how far they can see.

This may be true in the Caribbean, but not in the North Sea.

In any case, water is still quite absorbent of light at certain wavelengths; although the biggest problem terns to be the lack of light reaching down from the surface, light scattering due to suspended particles in the water, and the impermeability of radio transmissions.  Against this, there is good transmission of sound.

The problem with water is the pressure which is can be far harder to survive in, a vacuum is childs play compared to the presure of water deep down.

I don't see the difference.

Where there is a difference is that the difference in pressure between a vacuum and normal atmospheric pressure is only 1 atmosphere (i.e. what you lose if you remove the 1 atmosphere we normally live under), while there is no limit (OK, some limits do exist, but they are very extreme) to the pressure one can increase one's environment to.  I don't really thing it is any more difficult to live under 2 atmospheres than to live under zero atmospheres; but I will concede that it is more difficult to withstand 30 atmospheres than zero atmospheres.  It really depends upon how deep down under the sea one is considering living.

[Atomic-S]

I wonder what the chances are of folding a semipermeable membrane having a large area, into a little canister by folding, and using it to filter oxygen out of the water for breathing purposes.

[another_someone]

I wonder what the chances are of folding a semipermeable membrane having a large area, into a little canister by folding, and using it to filter oxygen out of the water for breathing purposes.

You seem to be talking about a synthetic gill.

I can see no theoretical reason it could not be achieved, but you would need to take into account two additional factors - you would need a sufficient flow of water over your synthetic gills to provide a sufficient supply of oxygen (this may be a very large flow indeed if you have a large demand for oxygen), and you will need to draw away oxygen from the gills fast enough to ensure they it does not start to flow back across the membrane.  Of these, it is the adequate supply of water (and ensuring it is a fresh supply, and not merely your own deoxygenated water flowing around again) that will probably be the greater issue.  Ofcourse, removing so much oxygen from the local water will also have an impact on other life in the area.