Free Engineered energy?

So if you had a heavy metal torpedo in the ocean attached to cable that ran down over a mile to the bottom of the ocean. Couldn't you have this torpedo drop down to the bottom while running some kind of turbine either useing the cable or water like a dam would in a sort of way. Then at the bottom release compressed air into air bags to send the turbin torpedo back to the surface to transfer it energy onto some grid, and refill the compressed air tanks atumatically with this stored power. Then repeat the process again.

 With many of these working together would it be a viable energy sorce? 

Nice thinking. But no. 

The easiest way to see this is to observe that you have described what appears to be a perpetual motion machine without proposing a refutation of the laws of physics (which imply a perpetual motion machine is impossible).

What you have not considered is the energy required to compress the air. To see this energy cancels what you gain, you can observe that filling airbags at the bottom needs to display a mass of water greater than that gained by the negative bouyancy in order to float the torpedo. Displacing this mass costs as much energy as you can gain from the rise. This may need a bit more detail to be clear.

Elroch I think you are missing something. It is very cheap in energy terms to have a air pump motor compress some air. By the way you could run the turbine going up also.

 You are using gravity. Maybe it wouldn't work at a hundred feet but I think the deeper you go the better compressed air displacing water would work. You don't need more air the deeper you go.

 So if it wouldn't pay back enough energy at 100 feet would it work at 7 miles? Challenger deep? Or hypothetically what if we were on an alien planet with a 100 mile deep ocean?

 This is not pumping H2O up to the top of a dam which would not work. This is just using gravity which is free, and displacing water which is cheap.

 Now if you needed really strong pumps to push air into the bags or ballast which I don't think it would be a problem but if it would you could also ship out boulders and add weight to the torpedos that would be released at the bottom. Still long term that doesn't work. I still think my idea with cmpressed air in bags or a ballast device would work. I don't think it's a perpetual motion machine that doesn't work. It's more like a thing using gravity like the earth, and moon seem to do endlessly. In nature it works. Rain give us the water for dams. I think this could be done. Is it practical is the question.

 Well the question also still is doea it really work? I know perpetual motion machines are impossible, and like I said you can't pump water up a dam and get more energy out that it took to pump the water up there. But I am not convinced my idea is a failed thought yet.

If I am gathering this right, you're sending a dense submarine down (with the compressed air) as when the air is compressed the volume of the apparatus is small so the density is large.  Then when it hits the bottom you expand the air bags to increase the volume of the apparatus to bring it back up.  The kinetic energy would be harvested both ways accordingly, sapping off of gravity's work.

I think rather than the compression of air that causes an energy leak, it is the energy needed to inflate the air bags.  If you are trying to expand the volume of something by even a 10"x10"x10" volume under 5 km of water, you'd need to displace 5km*10"*10"*(water's density) of weight.  It would probably take a lot of energy to prevent the water's pressure from just collapsing the air bags.

Alternatively, (though this could just be what you meant in the first place), if we had some sort of material X that is slightly lighter than water and did not mix (so it would float to the surface if released 5km down).  The submarine has a large chamber capable of holding a lot of this material, which when combined with the vehicle's weight causes it to all sink.  But this chamber is capable of expelling the material X into the water and create a vacuum in the chamber instead, which if big enough could cause the sub to rise on its own (along with all the material X it held).  Its pretty much the same as an air bag except with vacuum.  But it would probably take a lot of energy as well creating a positive pressure against the water to force material X out instead of letting water get in, and the energy required increases the farther down you go.

 Yes the pressures are a problem. If I can remember the sub with two men that went 6-7 miles deap was ballast with diesel fuel that was just a little lighter than water. Then they released weight at the bottom. They didn't use airbags or what I am suggesting, but could it be they want a more controlled accent. 

  But, what is the pounds per square inch? If it's 8k you can pressurize air more than that. I will go look some stuff up...I should have first. 

In 1960, the US Navy sent the Trieste a submersible - a mini-submarine designed to go really deep down into the depths of the Marianas trench to see just how far they would go. They touched bottom at 35,838 ft/10,923m. That means, while they were parked on the bottom, they were almost seven miles/11km of water over their heads! If you cut Mount Everest off at sea level and put it on the ocean bottom there would still be over a mile of water over the top of it! Now if we could stay down there for a while and study what sea creatures that could live under this immense pressure(16,000 pounds per square inch) we just might be surprised what we will find. 

 Okay, so I think you need a ballast tank with sea water. Then you have to have a compressed air tank that is higher than 16,000 PSI (mind you this is at 7 miles deep, and not as much if you were to be at a depth of 1 mile) Then you have just to turn a valve, and your comming back. I see there is psi tanks 20k+ so maybe this would work. Just what does it take to refill a 20k+ compressed air tank at the top?

 Fluid that you carry is going to really cut down on your speed. This needs to work with air displacing fluid.   

Wait what about using a thermal vent. There is a lot of gas there to return torpedo.

M

ok!

Now you've identified a genuine energy source. There are some conservation issues though.