Exploring deep ocean at 1GPa with minimum metal available

Let's say there's a habitable planet somewhere, covered with very deep cool water ocean. By very deep I mean thousands of km, but the exact numbers don't actually matter.

According to water's phase diagram, at 0.6 GPa and 0^oC, or 1GPa and room temperature denser than water ice VI becomes stable. The water is significantly salty, and I have no idea how it would influence ice formation. Say it would just drive the boundary a bit deeper. Also I see no reason for temperature to be far from 4^oC where the water is densest, at least that's what we see in the Mariana trench. So let's say there's icy ocean floor somewhere between 60 and 100 km deep, until Titan or Neptune is actually explored.

Now there's also a layer of buoyant organic matter covering most of ocean surface. It is actually thick enough for a small human colony to survive on top of it. And that colony is desperate for metals. From the ocean composition they think there must be at least iron, copper, and gold somewhere in the sediments on the ocean floor. Also there must be a lot of sticky organic ooze there.

So the question is: how to explore the floor and bring back samples without using too much metal?

The colony has a few portable, reliable, efficient fusion reactors capable of using any hydrogen-rich substance. However, they don't want to risk any of those unless absolutely needed. Also they can mine nearby asteroids/moons for metals and silicates, but that's expensive and again they don't want to risk the only ship too much. They can 3D-print any material at hand into any imaginable form, let's say big crystals are out of reach though (a diamond monocrystal submarine, huh). A robot capable of any formalized, non-creative task can be programmed. Other than that, let's say they are on todays mankind level. Calling for interstellar help is prohibitively expensive, they're already in debt and they also sunk a leased spaceship.

What I could think of:

• brute force - make a very thick steel bathyscaphe. I have little idea if steel can withstand that kind of pressure.
• use graphite bricks (hello RBMK-1000). How do they patch the seams between bricks?
• Power - accumulators? wires? just H₂+O₂?
• handling the ooze - how? Freeze it with liquid nitrogen, then drill through?
• How long would the journey to the bottom take (w/o humans on board)?

Feel free to correct/criticize my assumptions here if you feel they are wrong. Links to existing similar worlds are appreciated as well.

posted over 7 years ago

Dallaylaen‭

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