Can we use pressure to power an unmanned submersible for deep ocean exploration?

[The_Mark_of_Ivy]

This is a slight twist because I'm not looking to establish a colony under water, however my interest is still with ocean exploration. Allow me to ask the question:
Could we design an unmanned submersible exploration machine that can dive to the depths of our deepest capabilities with a sub, then dive deeper using the pressure we can calculate from that depth to power the machine in its additional exploration? So my thoughts were to construct a collapsible frame that is resistant up to the pressure of the deepest depth, then as the additional pressure collapses from going deeper that counter force creates energy to power this machine until it gets so low that the force crushes it past the minimum point that the functioning camera and other mechanics can hold their form. Your Questions/Answers

 

[NascentOxygen]

Hi.

I have edited your thread title to a more achievable goal.

Rather than let the pressure compress something, you could open a valve and tap the energy of inrushing water. But, energywise, you would be far better off not wasting extra fuel dragging an empty thick-walled shell all the way to the seabed in the first place.

Rethink this.

 

[CWatters]

+1

It's not energy that limits how deep a sub can go.

Sure you could gain some energy by allowing water into the sub but you might need to pump it out again if you want to surface.

 

[Baluncore]

The very deepest depths are less than 11 km. Manned submersibles have visited there before. https://en.wikipedia.org/wiki/Challenger_Deep

Electric batteries are probably the best solution to powering an underwater glider. https://en.wikipedia.org/wiki/Underwater_glider

Conservation of energy says you cannot get energy for nothing. Energy is not free. If you descend, and put energy into your descent, that energy may be available when you rise again. If you were to use that energy without rising, you would remain trapped on the bottom.

Once the density of your vessel is greater than water it will start to sink. As it sinks the external pressure will increase which will compress the vessel slightly, so it's density will increase. It may therefore tend to sink faster as it goes deeper. To rise again you will probably need to drop external ballast weights. You have to pay for those weights. Don't forget to attach them before the dive.

The density of water does not vary greatly with depth. You can expect water to be 2% more dense at 4 km than at the surface. It should take little energy to dive deeply if the vessel density can be made to closely track water density with changes in pressure. That will depend on design materials and structure. Avoid gas such as air bubbles in the vessel. They make return to the surface more difficult because they compress easily.

A camera can be filled with a clear fluid such as an oil to prevent collapse under pressure. Camera lenses need to be specially designed to allow for refractive changes when in contact with a liquid rather than air.