# 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:** 20\ **Page:** 3
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [October 10, 2011, 4:04pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/41 "2011-10-10T16:04:52Z")
> [@Leo\_Bloom](#): > > Interesting. Could you elaborate, using fire truck hoses as a counter-example, if that’s a good way to go about it? And, what is the rate at which atmosphere increases in temperature relative to pressure? [Ideal Gas Law](http://en.wikipedia.org/wiki/Ideal_gas_law). PV = NkT. P is pressure, V is volume, N is the number of gas particles, k is a constant, and T is (absolute) temperature. So, T = PV/Nk. N and k don’t change, but when the water rushes in, the pressure of the gas spikes as the volume shrinks. I don’t know the exact rates, but pressure goes up faster than volume goes down, and the result is that the temperature increases. This is the principle that refrigerators work on, and it’s why a bicycle pump gets warm when you use it. Applying force to compress a gas results in a temperature increase. ---
**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 10, 2011, 6:19pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/42 "2011-10-10T18:19:19Z")
> [@](#): > > Quoth **constanze** : > The only problem I would see is in case of something going wrong: you can’t simply send a rocket to the moon right now, you need a window because of gravity. But park the ISS in moon orbit instead of Earth, and wait till we’ve perfected nanotubes for a space elevator, and response time could be quick, too. That doesn’t solve the problem: How do you rescue the ISS, if something goes wrong there? If the point is just to have two independent habitats so one can rescue the other, it’d be much easier to put both of them on the Moon. Preferably right next to each other, with an airlocked tunnel between them, for ease of access. At which point you don’t really even have two habitats any more, just one bigger one. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [October 10, 2011, 6:53pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/43 "2011-10-10T18:53:41Z")
> [@Chronos](#): > > That doesn’t solve the problem: How do you rescue the ISS, if something goes wrong there? If the point is just to have two independent habitats so one can rescue the other, it’d be much easier to put both of them on the Moon. Preferably right next to each other, with an airlocked tunnel between them, for ease of access. At which point you don’t really even have two habitats any more, just one bigger one. Because it’s far more unlikely that things will go wrong with two systems at once and the same time. Likewise, I would put a permanent floating platform over the deep sea habitat, with pressure chambers already in place, to avoid delays. ---
**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 10, 2011, 7:32pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/44 "2011-10-10T19:32:01Z")
Sure, but why put one of those systems in orbit? It’s not like the floating platform over the deep-sea habitat; that’s an environment that doesn’t need extensive life support systems beyond maybe wool sweaters. But an orbital platform has basically all the same problems as one on the Moon, and then some. ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [October 10, 2011, 8:31pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/45 "2011-10-10T20:31:58Z")
> [@iamthewalrus\_3](#): > > [Ideal Gas Law](http://en.wikipedia.org/wiki/Ideal_gas_law). PV = NkT. > > P is pressure, V is volume, N is the number of gas particles, k is a constant, and T is (absolute) temperature. > > So, T = PV/Nk. > > N and k don’t change, but when the water rushes in, the pressure of the gas spikes as the volume shrinks. I don’t know the exact rates, but pressure goes up faster than volume goes down, and the result is that the temperature increases. This is the principle that refrigerators work on, and it’s why a bicycle pump gets warm when you use it. Applying force to compress a gas results in a temperature increase. Slight hijack. Some brainy prehistoric rocket scientest (AKA: Cecil’s Great[SUP]256[/SUP] Grandfather) invented the [Fire Piston](http://en.wikipedia.org/wiki/Fire_piston) while everyone else was still banging rocks together to make sparks. You can buy commercial versions at camping and survival supply stores. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [October 10, 2011, 8:56pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/46 "2011-10-10T20:56:39Z")
> [@constanze](#): > > This is a good reminder: where does the power come from? For the deep sea habitat, you probably use either nuclear, or maybe wheels (no, I’m not kidding - the gulf stream has a speed of 2.5 meter per second. You would put the habitat some safe distance away, of course, and lay a long enough cable.). > > Maybe your topside rescue station (permanently installed) could use solar and send down electricity per cable, but ideally a colony/ habitat should be self-supplied. That leaves nuclear, with all the inherent problems. > > The moon habitat, on the other hand, has half of the moon for space to put solar modules to generate electricity, and half the dark side to radiate away heat. I think you could satisfy the ocean-floor energy needs with geothermal power. Although placing the colony near a vent probably comes with other problems, like a more corrosive environment or the threat of an eruption. And I don’t think you were suggesting that there are permanent light and dark sides of the moon, although some people might read it that way. ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [October 10, 2011, 9:15pm UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/47 "2011-10-10T21:15:52Z")
Important note– In both cases, you are _actually_ talking about an _underground_ base. Unless you are a darn-fool. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [October 11, 2011, 12:53am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/48 "2011-10-11T00:53:44Z")
> [@Projammer](#): > > Slight hijack. > > Some brainy prehistoric rocket scientest (AKA: Cecil’s Great[SUP]256[/SUP] Grandfather) invented the [Fire Piston](http://en.wikipedia.org/wiki/Fire_piston) while everyone else was still banging rocks together to make sparks. You can buy commercial versions at camping and survival supply stores. Cool. And I now remember I used to know the basic info that **iamthewalrus** graciously supplied. It turns out that fire hoses, BTW, have a compression ratio of 25:1. But why is this ratio higher than that of a race car, e.g.? ---
**Author:** ![lisiate](https://avatars.discourse-cdn.com/v4/letter/l/f05b48/32.png) [@lisiate](https://boards.straightdope.com/u/lisiate)\ **Post date:** [October 11, 2011, 1:31am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/49 "2011-10-11T01:31:35Z")
I’m not sure I understand your question. Are you asking why the compression ratio in a gasoline engine is less than in a fire hose? if so, it’s becuse the gasoline would ignite from the compression rather than the spark - causing knocking. Diesel engines use compression to ignite the fuel injected into the cylinder and some almost get up to 25:1, While we’re on the subject of pressure have a look at the _[Byford Dolphin Diving Bell accident](http://en.wikipedia.org/wiki/Byford_Dolphin)_ for an example of what can happen when things go wrong with a pressure differential of _9_ atmospheres: > [@](#): > > Diver D4 was shot out through the small jammed hatch door opening and was torn to pieces. Subsequent investigation by forensic pathologists determined D4, being exposed to the highest pressure gradient, violently exploded due to the rapid and massive expansion of internal gases. All of his thoracic and abdominal organs, and even his thoracic spine were ejected, as were all of his limbs. Simultaneously, his remains were expelled through the narrow trunk opening left by the jammed chamber door, less than 60 centimetres (24 in) in diameter. Fragments of his body were found scattered about the rig. One part was even found lying on the rig’s derrick, 10 metres (30 ft) directly above the chambers. His death was most likely instantaneous and painless. Granted that was a decompression event; but I won’t be volunteering to be in an undersea habitat subjected to far higher pressure differentials. ---
**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\ **Post date:** [October 11, 2011, 1:43am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/50 "2011-10-11T01:43:25Z")
Is pressure at the bottom of the ocean only vertical or also horizontal? That is, if your structure is a square (not that it would be), does pressure only come from the top or the sides too? How would one handle moving things in and out of an ocean floor base? Could you simply flood a compartment with water from the base then open the compartment to the outside, let the shipment in, close the exterior door, drain the compartment and open the interior door? I remember reading up on water jet cutting. At high enough pressure, water will cut through steel if it’s in a jet. Could this happen if there were a puncture? ---
**Author:** ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)\ **Post date:** [October 11, 2011, 2:20am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/51 "2011-10-11T02:20:10Z")
> [@Bosda\_Di\_Chi\_of\_Tricor](#): > > Important note– > > In both cases, you are _actually_ talking about an _underground_ base. > > Unless you are a darn-fool. I’m not sure what you mean by this, but it brings to mind one question I had: for the ocean floor base, could you avoid some of the pressure problems by _burying_ the living compartments? That is, except for the hatch perhaps, all other parts of the base would be “underground” as Bosda says. Also for a lunar base, I’ve read somewhere that scientists speculate there may be some sort of empty lava tubes under the surface of the moon that would be almost ready made for habitation, once you seal off the ends and pump the atmosphere in. ---
**Author:** ![appleciders](https://avatars.discourse-cdn.com/v4/letter/a/85f322/32.png) [@appleciders](https://boards.straightdope.com/u/appleciders)\ **Post date:** [October 11, 2011, 2:27am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/52 "2011-10-11T02:27:21Z")
> [@MichaelEmouse](#): > > Is pressure at the bottom of the ocean only vertical or also horizontal? That is, if your structure is a square (not that it would be), does pressure only come from the top or the sides too? Also from the sides. The water on the sides of the station is under tremendous pressure from above, and would move sideways into the station to allow the water above it to move downwards if your side armor fails. > [@](#): > > How would one handle moving things in and out of an ocean floor base? Could you simply flood a compartment with water from the base then open the compartment to the outside, let the shipment in, close the exterior door, drain the compartment and open the interior door? Probably. It’s the same basic airlock principle that we use in both spaceships and submarines today. > [@](#): > > I remember reading up on water jet cutting. At high enough pressure, water will cut through steel if it’s in a jet. Could this happen if there were a puncture? More or less. The pressure of the water rushing in would tend to widen punctures quickly. ---
**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 11, 2011, 2:28am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/53 "2011-10-11T02:28:43Z")
Pressure is isotropic: It pushes in all directions equally. And supplies would have to come in and out through an airlock of some sort, but it’d be tricky at best to make moving parts that can stand up to those sorts of pressure differences. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [October 11, 2011, 2:36am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/54 "2011-10-11T02:36:31Z")
I’m skeptical that there is a pump anywhere in the world right now strong enough to push the water out of an airlock and back into the surrounding ocean at a depth of 12,000 ft. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 11, 2011, 2:52am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/55 "2011-10-11T02:52:44Z")
> [@Boyo\_Jim](#): > > I’m skeptical that there is a pump anywhere in the world right now strong enough to push the water out of an airlock and back into the surrounding ocean at a depth of 12,000 ft. I don’t know if it can be done in a single stage, but it can be done with multiple stages. It certainly will not do that very quickly unless the pumps themselves greatly exceed the size of the airlock. There isn’t much need for a true airlock though, nobody is going in or out of a habitat at a depth of 12,000 ft. without a pressure vessel. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [October 11, 2011, 3:37am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/56 "2011-10-11T03:37:44Z")
> [@lisiate](#): > > … > > While we’re on the subject of pressure have a look at the _[Byford Dolphin Diving Bell accident](http://en.wikipedia.org/wiki/Byford_Dolphin)_ for an example of what can happen when things go wrong with a pressure differential of _9_ atmospheres: > … Holy crap. Plus the autopsy said that most of the guy’s lipids were essentially squshed out from his bloodstream and muscles. I should tell my endocrinologist; it would save me money instead of buying Tricor. And I thought the decompression of the guy Sean Connery shot in _Outland_ looked bad. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [October 11, 2011, 3:43am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/57 "2011-10-11T03:43:16Z")
And the deep ocean pressure differential is 40 times that. ---
**Author:** ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)\ **Post date:** [October 11, 2011, 3:46am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/58 "2011-10-11T03:46:32Z")
Amazing to think that there are environments we can temporarily visit right here on earth that are so much more hostile to human life than _frikkin’ outer space_. I mean, a person could survive exposure to the lunar environment for maybe 90 seconds or so, right? But it sounds like even a second at 12,000 feet would have them gathering your remains in a bucket. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 11, 2011, 3:48am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/59 "2011-10-11T03:48:34Z")
> [@Koxinga](#): > > Amazing to think that there are environments we can temporarily visit right here on earth that are so much more hostile to human life than _frikkin’ outer space_. I mean, a person could survive exposure to the lunar environment for maybe 90 seconds or so, right? But it sounds like even a second at 12,000 feet would have them gathering your remains in a bucket. Yes, this is why any habitat at great depth will be essentially underground. If not literally, you have to be covered with a massive amount of material to keep the weight of the ocean from flattening you like a cartoon steamroller. ---
**Author:** ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)\ **Post date:** [October 11, 2011, 3:52am UTC](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144/60 "2011-10-11T03:52:47Z")
> [@Leo\_Bloom](#): > > And I thought the decompression of the guy Sean Connery shot in _Outland_ looked bad. Sounds to me like a closer picture would be what happened to Rorschach at the end of _Watchmen_. [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=2) [Next page](https://boards.straightdope.com/t/which-is-harder-to-build-maintain-a-habitable-lunar-colony-or-deep-ocean-floor-base/599144.md?page=4)