# The Hydrolock - How to build a deep sea docking system?

How do you build a docking system at deep sea pressures? Example a Challenger Deep Sea Base at 10,000 meters seawater or approximately 1,000 atmospheres?

• how are you keeping humans alive at that depth? this has a pretty big impact on how a connection can work.
– John
Commented May 6, 2021 at 21:45
• See my comment on Nosajimiki’s comment below. A multistage chain of locks reduces the engineering challenge quite considerably. Commented May 7, 2021 at 9:14

I've been working on this thought problem about how to create a docking system for deep sea bases. It's not as straightforward as one might originally think because the system has to:

1. maintain hull integrity the whole time.
2. transfer between extreme pressure differences while:
3. -not having any pumps capable of doing so.
4. maximum pump depth right now is 5,500 meters. And that's pushing the limits of 100 years of development.

So bottomline, you can't just pump your way out of the problem like in a normal airlock that transfers gas from one pressure to another pressure usually between 0atm to 0.3atm (or 0psi to about 5psi). And you therefore can't pressurize the gas, so the airlock can't be one contained system with pressure tanks.

So having mentioned the hurdles, here's the basic thought process so far.

1. Have two pressure hulls capable of maintaining 1atm at 1000atms (10,000meters seawater).
2. Have one of these hulls contain water.
3. Transfer water between these hulls to transfer a relatively incompressible material from one hull to the other.
4. Equalize pressure between the hull containing water and ambient pressure so its hatch can be removed.
5. Dock another pressure hull to the removed hatch.
6. Re-equalize the pressures again, back to 1atm.
7. Remove the water from the docking hull to the water tank.

I call this a "hydrolock". In principle it works much like a torpedo tube. The pressure hulls are subject to massive stress at the seams (where the spheres meet). I'm not sure if these seams would rupture or leak.

Seals are formed by metal-on-metal contact, so I believe that the greater exposed surface area will keep a strong metal-on-metal seal at the seams since the seams represent a very small amount of total surface area.

• Industrial Engineers often used staged pumping systems to overcome high pressure limits. Pumping from 100atm to 200atm is about the same resistance as going from 1atm to 100atm. So, if you design an incremental system of 10-15 air tanks daisy chained together with compressors between each tank, you can achieve these pressures just fine... at least from a pumping perspective. A 1000atm air tank may be harder to come by Commented May 6, 2021 at 21:54
• @Nosajimiki’s thoughts are good here. I think that using a chain of locks could resolve the extreme pressure problem. It would be a slower result, but far more easy to mitigate against disaster. In many ways similar to raising and lowering passage over mountains for canal locks: use many, not one. I would feel far more comfortable living in a multistage locked environment! Commented May 7, 2021 at 9:12

Moon pool.

https://en.wikipedia.org/wiki/Moon_pool

A moon pool is a feature of marine drilling platforms, drillships and diving support vessels, some marine research and underwater exploration or research vessels, and underwater habitats, in which it is also known as a wet porch. It is an opening in the floor or base of the hull, platform, or chamber giving access to the water below, allowing technicians or researchers to lower tools and instruments into the sea... A moon pool also allows divers or small submersible craft to enter or leave the water easily and in a more protected environment.

No moving parts. Moon pools work. The only tricky thing is that atmospheric pressure of the gas above the water must be equal to the water or the water will come up thru the moon pool and compress the gas. Having high pressure gas in a habitat is easier on the habitat too because it makes it more crushproof.
1000 atmospheres is pretty high. You might need to pressurize your moon pool room, enter, close the hatch, and then depressurize the moon pool room, pumping your atmosphere back into canisters.

If your craft is too big to fit thru the moon pool, poke part of it up thru the moon pool and step out.

If it is a science fiction horror, monsters can come up thru the moon pool too. Good thing you have a hatch. Did you close the hatch?

• this only works if the air pressure is equal ot the water pressure, and humans can't breath air at that pressure.
– John
Commented May 6, 2021 at 21:46
• @John Thanks John, agreed. If anyone wants more elaboration, basic rule of thumb is a person cannot breathe more than ~2atm partial pressure of oxygen. You'll go into seizure. Called oxygen toxicity. There's another problem with moonpools. They aren't even effective when you need gas-mixes because the gas exchange rate through a moon pool is VERY HIGH. Meaning if you had a helium mix you'd lose almost all your helium in a short period of time. Commented May 7, 2021 at 0:04
• @IDNeon, John, anyone else: the Willk habitat has a hatch over the moon pool. Monsters, you know. Also losing your helium. Also adjusting atmospheric pressure inside after the submersible crawls thru. Now that we have settled that, let the upvotes flow! Commented May 7, 2021 at 12:28