I suspect both would be beyond the reach of today’s technology. But imagine that some time in the next century, you have the choice of funding one of these two projects.
(A) A lunar base that can support say fifty people for a minimum 25 years, or
(B) A base with the same specs but built on the floor of the deep ocean (well away from the continental shelf.
You’re responsible for everything connected to the project through the date of its conclusion.
Which would be harder?
It’s a matter of logistics. It’s exponentially harder to get supplies and gear to the moon than it is to the bottom of the sea. One scenario would be to build your underwater colony on the surface and once all is complete you tow it to where you want it and then sink it. From that point getting supplies down to the colony is just as easy. Getting things back to the surface is a little tougher but still tons easier than getting things from moon to earth.
Certainly there are a lot of other considerations but all of the dozens that quickly pop to mind are all easier to deal with on the ocean floor than on the moon.
Getting payloads to (and from) the ocean floor is easier than getting them to (or from) space, but on the other hand, building a habitat that can survive the ocean floor is a lot harder than building one that can survive vacuum (cue Futurama reference). I suspect that the launch costs end up being worse than the high-pressure costs, but it’s not a slam dunk.
One thing I’d say is that a small leak would probably be a minor problem in space, but instantly and catastrophically fatal in the deep ocean.
I think we already have the technology to build a moon base – though not the economy or the products on hand, like enough supply ships, etc. If we had a good enough reason to do it, we could get one going in relatively short order.
I don’t think the same can be said for an ocean floor base. I suspect it’s many orders of magnitude more difficult to maintain a reasonably comfortable and spacious living environment that can survive deep ocean pressures than one that could survive a vacuum.
If you’re just talking about the pressure differential, you’re right, it’s much less in space. A spacecraft hull just needs to withstand 1 atmosphere (or less, if you use an oxygen-rich air), while the pressure is much greater at the bottom of the ocean - about 1000 atmospheres if you want to go to, well, you know where.
But consider the other factors that make an undersea base easier than a lunar base:
Unlimited supply of water. A bit salty, but reverse osmosis will take care of that. But more importantly, it means an unlimited supply of oxygen; all you need is power for electrolysis. In fact, you wouldn’t even need a closed life-support system as you would on a space station. Just keep generating fresh oxygen and pure water, and dump the waste products. (I believe that’s what nuclear submarines do?)
Cooling. Water-cooling is far more efficient than radiative cooling. And you need cooling for anything that generates or uses power. (The radiator array on the ISS almost as big as the solar panels, in terms of total surface area.) In particular, nuclear reactors cooled by seawater is already a proven technology; a radiatively cooled nuclear reactor would be much more difficult.
The lower transportation cost for the ocean means the structure doesn’t need to be lightweight. And it’s much easier (cheaper and quicker) to design an over-designed structure than one that’s lightweighed to the extreme.
I’m willing to bet that these factors more than make up for the difficulty of dealing with the high pressure.
The structural strength needed for sea floor (even just the abyssal plain, not to consider actual deeps.) is simply too great to maintain without huge amounts of over engineered safety margins. The normal operational conditions make every single act of entry and exit a significant risk, and any sort of geological event a potentially devastating catastrophe.
If you get a containment breach in a lunar habitat, the force of expelling air is limited to one atmosphere of pressure. It moves outward, and will probably not have any effect on separate zones. The force of water moving into a sea floor habitat is several orders of magnitude higher, and delivers massive amounts of water moving at high speeds into any communicating airlocks. So, either you build every single zone as a separate structure with separate infrastructure, or you risk the entire structure failing from any breach event.
The total engineering cost of such habitats, and the complex systems needed to move into and out of them make operations highly complex, and exacting. Stress on the occupants would be significant. Opening a door and exiting or entering the habitat would be both expensive, and dangerous for the entire facility. Everything that is done on the sea floor will be done via remote control vehicles, which will require cable connections, and all the attendant limitations that implies. Surface vessels will need to be available at all times, probably requiring a floating platform for logistics on the surface, and port facilities for supply and whatever product is generated, even if it is only information.
Of course lunar habitats would have analogous risks, and expenses, but we already have forty years of engineering art on dealing with those risks. Long term operations at greater depths are something fairly new. Human exposure to such environments is currently measured in days, or weeks, and almost always at depths much less than the sea floor. Colony is a term that implies long term occupation.
Tris
Wouldn’t a small leak just create a slow flow of water, which would be taken care of by bilge pumps?
What would a “small leak” in a space base actually do? Would oxygen seep out of it, making it harder to breathe? Would the pressure be effected?
No, because behind the leak is the biggest pump in the work, the the whole weight of the ocean above, forcing water through the leak. It would make a fire hose look like a pussy.
In some other thread, someone said that in terms of pressure difference, going up from sea level to the top of Mt. Everest (about 30,000 feet) is about the same as going up from 17 feet under water up to the surface. I dunno how precise that is, but it certainly gives an idea of just how much heavier water is than air.
According to this site, atmospheric pressure doubles every ten meters or so of depth under water. According to this site, the average depth of all the world’s oceans is about 3800 meters, maybe a bit more by some estimates.
So it you go from earth surface to space, you go from 1 atmosphere to 0. You go to the average ocean depth, you go from 1 atmosphere to 380 atmosphheres.
Oxygen and whatever else made up the atmosphere would leak out – it is doubtful that it would be pure oxygen. As Tris mentioned, though, a leak in space would be 1 atmosphere pushing out. A leak at average ocean depth would be 380 atmospheres pushing in.
Ultimately a small leak would effect the pressure in space, depending of course upon how soon it is discovered and fixed. And just like a balloon will deflate, presumably the seal will not be perfect in any case, so there must be a reservoir of atmosphere to keep the the pressure up.
Not under that kind of pressure. You’d probably initially see a spray leak coming into the station, which would be extremely high pressure but low volume, but it would quickly rip a larger hole which would flood the station faster and faster as the hole enlarged. I think you’d have a brief (no more than thirty seconds) window of time to stop the leak before it cascaded into a massive failure.
However, I don’t think that a “small leak” scenario is the most likely. I think it is more probable that a flaw in the armor would simply cause the station to be crushed like a beer can on a frat boy’s forehead, only quicker and more completely. After that, the station would fill with water fairly quickly, but you’d be too dead to care.
The atmosphere (either air or pure oxygen, probably) would seep out. If it were a very small leak, you might not notice for hours or days until your instruments registered a pressure drop. In that time, you’d probably release small amounts of smoke or other visible gas or suspension into the atmosphere and try to track that back to the source of the leak, then seal the leak. A larger leak (say, fist-sized) would allow all the the air in any room smaller than a gymnasium to escape in no more than a few minutes, killing all the crew present. However, it would be quite easy to design your station with pressure-tight bulkheads so that the whole station is not threatened by a single puncture.
You’d be incinerated before you drowned. The failure of the pressure vessel at depth would create a piston of water moving through the habitat that would instantly compress the internal atmosphere into a tiny volume producing an accompanying spike in temperature.
It would, however, be mercifully quick.
jacques cousteau experimented with an undersea housing module in the 1960’s.
I recall several major magazine articles when I was a kid. They eventually abandoned the project.
I was just trying to look for a cite for this. I recall that there was some indirect evidence of it in submarines that had failed and gone below their crush depth. Of course, no one has ever survived such an incident to witness it, and if the navy ever tested a hull to destruction and documented what happened, then they haven’t declassified it AFAIK. But is would also be likely that any instruments in such a test would be destroyed moments after the breach.
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?
Yeah, I read it years ago when I was doing research for a submarine game. However, I can’t remember the source.
It sounds like the consensus so far is:The deep sea habitat is easier to build and maintain than the lunar habitat, but more likely to fail catastrophically.
My opinion: a catastrophic failure is the best way to go in either circumstance.
The deep sea one may be easier to build in the sense of supplies and logistics being more readily available, but I think it would be FAR more difficult to build from a technological standpoint.
Hell. I bet you could just use large oil tanks as habitats on the moon if you could slap engines on them and get them there. You’d have to send along a bunch of other shit too, but if you’re not worried about the cost, then you could do it pretty easy.
I agree you wouldn’t drown. I believe that you’d be crushed to death by the collapsing ship’s walls. I suppose it’s possible that water would breach one section and flood the rest, but I think that most super-strong structures like this tend to have interdependent supports, and a failure in one section would so badly destabilize the station that it would be crushed at least as quickly as it flooded.
Or just have neutral-buoyancy balloons with a layer of goop on the inside continually floating around in the corridors. A small leak would create air currents that would pull the nearest balloon to it, pop it, and automatically create a seal.