Well, this is not 100% on-topic, but here is the link to NEEMO, the NASA undersea habitat. People live there for up to 3 weeks at a time. There is no corresponding link to a NASA lunar habitat (other than the Habitat Demonstration Unitproject).
NASA was working on a long-duration lunar habitat, in some scenarios up to 90 days, with a crew up to 6 or so. Achieving that much is, as we say, a Small Matter of Engineering. An actual Moon Base would be more…challenging. Most scenarios involve resource extraction from the Moon–the discovery of water on the Moon makes this easier. Still, we know all the parts that we would have to build to get this to work.
And on thinking about it even further, you’d never even need to empty the lock. Have the inside end of the lock open into a pool in the base’s interior. Drive your sub in through the outer door, close the outer door, equalize pressure, open the inner door, drive through that one too, then surface in the pool.
The fact that water does have a nonzero compressibility does mean that water would slowly work its way into the habitat, a little each lock cycle. But that’s a long-term problem, and I imagine that slow pumping would be a lot easier than fast.
That’s what I came to mention.
Also, from a simple energy standpoint, sea floor is much easier. To bring construction materials to the Moon Base, you’ve got to rocket them up first. Rockets have a notoriously horrible energy/payload ratios.
To bring materials to DeepHab One, you only have to drop them from the surface. They’ll reach bottom eventually, no matter how deep “bottom” is.
I’d like some clarification from the OP. “Harder to build” – there are two totally separate ways to perceive this. One is logistical expense/convenience. The other is technological hurdles to overcome. Some of the latter might not even be issues if the former is not a concern. For instance, we don’t have to worry about self-sustaining food or air supplies in either location if we can afford to resupply them as often as necessary. Other technological hurdles must be resolved before we can even consider starting construction.
So are we talking about economically difficult or technologically difficult? For the former, I would say the moon base would be the hardest, hands down. For the latter, the ocean floor base would be, IMO hands down again.
I’m not sure I understand. Does your OP boil down to “which would be more expensive”? That’s what it sounds like.
Though there’s even another way to think about the costs – which could be made more attractive to Congress to fund? Cuz, ya know, what if there are Muslim terrorists digging their way into our country’s precious bodily fluids by way of tunnels under the ocean!!! We need forts down there to intercept them and defend ourselves!!
How deep are we talking exactly? Experiments in hyperbolic chambers showed that humans could safely live at pressures equal to that of depths around 2000 fsw (actually deeper but anything past that is pushing the limits of both safety and comfort). If the habitat is at or shallower than that then the architectural arguments become null. Even if it’s deeper pressuring the habitat to that would reduce the strain possibly making it easier.
Well never mind then, I suppose a 1.6% decrease in strain wouldn’t really be worth all that helium. I’m gonna have to agree with some of the other posters here. The ocean would be easier from a logistics perspective, but we simply don’t have the technology to accomplish anything like it yet. Either way the costs would be enormous, and cool though it would be I simply can’t think of a good reason to do so at this time.
What about liquid breathing? I’m not up on the latest (although as I understand it it’s still theoretical), but I’m wondering if that would solve the pressure issue, or if even then you’d need pressure hulls. Assuming you had a water-equivalent that you could breathe, what kinds of pressures could a human body adapt to?
That might help. My understanding is that one advantage to liquid breathing is in theory you wouldnt need to decompress (or at least it would be much easier)because you just load it with dissolved oxygen and nothing else and the body is good at moving oxygen around. The second advantage is that you don’t have to breath some other gas like nitrogen or helium, which besides the decompression problem cause other problems (nitrogen makes you go to sleep, helium give you tremors/convulsions).
However, its also my understanding that at great depths you have yet another problem. Water and proteins and other stuff your body is made of ARE slightly compressible. Its certainly possible that at extreme depths they get compressed enough (even IF you are breathing a liquid) that they don’t “work right” anymore. I seem to recall some extremely deep living species not being able to survive at surface pressures due to this exact problem (well the reverse of it anyway).
If I had to guess, the compressed body stuff wouldn’t cause problems (but it might) short term but the body could not take long term exposure to it.
That occured to me earlier in the thread, but I don’t see it as a long term option. As you mentioned I recall and article some years backck about biological functions operating differently under extreme pressures.
Not to mention all the standard biological functions that aren’t designed for an aquatic environment. Eating. Drinking. And of course the other ends of those processes. A perfluorocarbon soaked pepperoni pizza just doesn’t sound too appetizing.
Out of curiosity, could you use the pressure itself to generate power? We’ve been talking about how dangerous even a small leak would be because of the enormous pressure of the water. Suppose you could direct that pressure to a turbine generator.
I’m guessing the downside would be you’d be letting in water and at some point you’d have to pump the water back out of your station. And presumably the energy you’d need to pump the water back out would be greater than the energy you’d generate by letting it in.
For air, K = 1.4. All temperatures should be provided on an absolute scale (i.e. Rankine or Kelvin).
At 12,000 feet, the pressure is about 5300 psi. Assume the air in the habitat is initially at 14.7 psi and 70F (529R).
Now assume a catastrophic failure of a portal somewhere in the station results in water rushing in, compressing all the air in the station up to 5300 psi.
Final temperature of the remaining air pocket? T[sub]2[/sub] = 2385F. That’s pretty hot. Diesel engines run with a compression ratio of around 20:1; the temperatures and pressures in the habitat failure correspond to a compression ratio of about 67:1. So about 1/3 of the way through the failure event, air temperatures in the station would already be hot enough to ignite flammable items, burn skin, and sear your lungs. If the failure takes a significant amount of time to flood the station, it’s likely to be a pretty miserable death.
