# Which is harder to build/maintain, a habitable lunar colony or deep ocean floor base? **URL:** \ **Category:** Factual Questions\ **Created:** [October 10, 2011, 2:54am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144 "2011-10-10T02:54:56Z")\ **Posts on this page:** 6\ **Page:** 7
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 14, 2011, 5:20pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/121 "2011-10-14T17:20:55Z")
> [@Koxinga](#): > > Well, how does the pressure of the water at 12,000 feet down compare with the load borne by [a mine shaft under an equivalent distance of rock?](http://en.wikipedia.org/wiki/TauTona_Mine) It seems to me that it’s not only the pressure of the water that makes it dangerous, but also its extremely fluid state. I was wondering if really thick mud – either found on site or piped in from another location to cover the habitat – could mitigate that problem. Fine silt or clay won’t bear a structural load; the full 5300 psi at that depth will be borne by the structure of the habitat. If a leak develops, the clay will extrude into the habitat through the leak just like an ultra-high-pressure [Play-Doh Fun Factory.](http://en.wikipedia.org/wiki/File:Playdoh.jpg) ---
**Author:** ![StrangerThanFiction](https://avatars.discourse-cdn.com/v4/letter/s/f05b48/32.png) [@StrangerThanFiction](https://boards.straightdope.com/u/StrangerThanFiction)\ **Post date:** [October 14, 2011, 5:31pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/122 "2011-10-14T17:31:17Z")
> [@Boyo\_Jim](#): > > I don’t think any fish live down that far either. Sure they do. Fish in the abyssopelagic and bathypelagic zones may not be as abundant nor as sprightly as fish near the surface, but they do exist, and they are quite numerous and diverse. The deepest dwelling fish ever found were discovered in 2008 in the Japan Trench, at a depth of over 25,000 feet. [Researchers came upon a group of snailfish](http://news.nationalgeographic.com/news/2010/10/photogalleries/101014-deep-fish-seen-snailfish-eel-ocean-pictures/) who were surprisingly active considering their environment. That said, I don’t think they’d present much of a threat to a structure that has the ability to withstand the immense pressure at 12,000 feet. Also, I wanted to add a note about high pressure pumps. I found [this company](http://www.cncmi.net/pumpsizing.htm), which sells pumps for waterjets. Their highest capacity pump is capable of pressures up to 60,000 psi. It would be able to push 3 gph out of a sea-level atmosphere habitat placed on the bottom of a 135,700-foot deep ocean. In fact, the high-pressure fuel pumps on modern direct-injection diesel engines must generate sufficient pressure to inject fuel into a cylinder where the combustion process has already begun. Needless to say, the working pressures are fairly high. The pump on the engine I’m most familiar with, which is essentially a Mercedes car engine, is capable of supplying 24 gallons per hour at 19,200 psi. These things are all over the place; you may very well have pulled up next to one the last time you were stopped at an intersection. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [October 15, 2011, 3:13am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/123 "2011-10-15T03:13:03Z")
> [@Machine\_Elf](#): > > If you’re extracting energy provided by the pressure of the water, then you need a low-pressure reservoir to dump the water to. That’s the interior of your habitat, and here we’re back to the original problem of limited space in there. If you’re thinking “aha, I’ll just dump the water to the surface of the ocean,” well, it takes energy to pump it up there; notice that a pipe from the surface of the ocean to any arbitrary depth does not magically flow water from that depth up to the surface. > > If you’re extracting energy provided by the current (the kinetic energy of the water), then the static pressure is irrelevant; a current of any arbitrary speed provides the same potential for power generation whether it’s at the surface or at a depth of 12,000 feet. I’m fairly sure that’s not true. If you are able to place an unmoving circle of metal into a flowing stream of water, then you’re creating a vacuum behind it. Since it’s harder to establish a vacuum the greater the amount of pressure in your surroundings, the more effort it takes to keep your circle stable. No? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 15, 2011, 3:24am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/124 "2011-10-15T03:24:56Z")
> [@](#): > > If you are able to place an unmoving circle of metal into a flowing stream of water, then you’re creating a vacuum behind it. Not unless it’s an extremely fast-flowing stream. Note “fast”, there, not “high-pressure”. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [January 28, 2019, 3:17am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/125 "2019-01-28T03:17:23Z")
Bumped. PBS’s _American Experience_ will show a SeaLab documentary on Feb. 5 - check local listings: [https://www.pbs.org/wgbh/americanexperience/films/sealab/#part01](https://www.pbs.org/wgbh/americanexperience/films/sealab/#part01) ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [January 28, 2019, 3:52am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/126 "2019-01-28T03:52:52Z")
Question : what is the benefit of having your habitat all the way on the ocean floor? Wouldn’t a habitat just a mere 100m or less under the surface be deep enough to be unaffected by storms and waves? You’d anchor it with cables to the seafloor. Then, for the actual resource exploitation of the seafloor - assuming you want to do more than just live inside artificial caves with people - you use robots. It’s much more achievable to make robots resist the pressure because most of their components can just be directly exposed to the pressure, with equalizing membranes of oil. Very small armored housings would be needed for the sensors and things that need to be protected. The thing is, if you had the habit on the seafloor, you’re going to only be able to send robots outside \*anyway \*- the pressure is much too high for human divers. Even hard suits that have an internal pressure sphere only have robotic waldos to manipulate the outside world. As a side note, you could make your colony semi-submersible. You’d be able to surface with portions of it most of the time and enjoy the fresh air and sunlight and only would need to submerge for storms. [Previous page](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144.md?page=6)