A swimming pool on the Moon.

[Measure_for_Measure]

Would there be greater numbers of suspended water particles of water in the air? I see that Lehnert et al wrote of “Aerosol Deposition Along the Respiratory Tract at Zero Gravity: A Theoretical Study” in 1985. 1985lbsa.conf..671L Page 671

[si_blakely]

@Sapo

A presume that 1/6 g is enough that you cannot drown in a blob of water as you could in zero g. Is that even true? That a big blob of water in zero g could wrap itself around your head and drown you?

Even if the water did wrap round your head, any air you exhale will also stay put in a bubble round your mouth (it cannot go up), so you will probably asphyxiate slowly as the CO[sub]2[/sub] content goes up from rebreathing, rather than asphyxiate quickly from H[sub]2[/sub]O aspiration.

Si

[Shamozzle]

@Sam_Stone

I’m not sure that’s why there is a drain around the lip.

Isn’t it to accommodate circulation?

[Quercus]

@Chronos

Whether you float or not will be unchanged, but your buoyant force (like your weight) will be 1/6 of what it is on Earth. If you’re just backstroking on the surface, this isn’t a problem, but if you were to find yourself on the bottom of the pool for some reason, it’d take you longer to float back to the surface. I doubt it would be long enough to make drowning a serious hazard, for a pool of any reasonable depth, but the calculations are pretty messy, so I don’t feel like actually working it out right now.

What’s the messy calculation? Bouyancy is 1/6 of that on Earth, and mass is the same. So, for a bouyant object held under the water and let go, the acceleration will be 1/6 of that on Earth, and it will take square root of six times longer to reach the surface.
Am I missing something?

[Napier]

Oops. Missed the “indoors”.

This pool would probably be noticeably harder to play in because the waves would reach much higher and move much more slowly. Spray would also probably include more and bigger droplets going higher and staying airborn longer. You’d probably inhale a lot more water than you’re used to. I would guess diving would be about like it is on Earth except in slow motion. Surfacing would be slower to the extent that you rely on buoyancy as the force would be smaller, but strokes and swimming would be as vigorous as before. Maybe you’d have to learn more control to keep your strokes deep enough not to keep sucking air or missing the water as it sloshes, because not only are the waves higher, but the pockets of air between waves will run deeper too, I guess 6 times deeper. Maybe you would come entirely out of the water pretty often if you used old swimming styles, and flap uselessly in the air.

[Sapo]

@Chronos

Of course not: The few inches of rim isn’t even enough to hold the splashes in on Earth. Why is this a problem?

But if you want to have the same amount of splash containment (such as it is) as in an Earthly pool, just take whatever distance from water to rim you consider acceptable here, and multiply by 6.

Simple enough. It is quite a bit, though. You would end up with a postage stamp pool in the middle of a basketball court dome. And talking to someone in the pool from a chair outside might require an undesirable amount of yelling.

My concern is with the amount of water that splashes outside the pool and cannot be put back in the pool. This gives you the twin problems of having to dispose of all that water and of having to replenish it. I mean the water that falls on the floor where you walk around the pool, not:

@Sam_Stone

I’m not sure that’s why there is a drain around the lip. I think it has more to do with preventing sloshing back and forth. If the edges of the pool were just curved upwards, waves creates would slosh one way, then the other. With the right action, you could set up reinforcements to the wave and cause some major overflows. With the grates along the edges, the sloshed water is poured away and the energy dissipated. I’m guessing that water is returned to the pool - otherwise, the pool would have to constantly be repleneshed with new water. That seems like quite a waste.

Which could be the solution to the problem. That inner lip that catches the sloshing (that is in fact recirculated) could just be made higher and/or wider so water doesn’t splash outside where it has to be discarded but in that “clean” space where you can recirculate it back to the pool.

So we then have a pool encased in a tall step all around it. Might not look pretty but it would a lot less area than just multiplying by six the distance around it and losing all that water.

Probably a bit of a clear plastic shield at an angle all around it (think sneeze guard at the buffet meet hokey rink shield) would make for a smaller design and better visibility for mom to watch junior.

[Chronos]

What’s the messy calculation? Bouyancy is 1/6 of that on Earth, and mass is the same. So, for a bouyant object held under the water and let go, the acceleration will be 1/6 of that on Earth, and it will take square root of six times longer to reach the surface.
Am I missing something?

The messy part is fluid drag, which is non-negligible here. Even in the textbook-ideal case, it depends on the shape of the object (and humans of course have a very complicated shape), and even with a simple shape it would leave you with a rather uglier differential equation to solve than in the constant-force case.

Simple enough. It is quite a bit, though. You would end up with a postage stamp pool in the middle of a basketball court dome. And talking to someone in the pool from a chair outside might require an undesirable amount of yelling.

No, I meant in terms of depth, not the deck area around the pool. Like, if, in a normal Earthly pool, the water level is two inches below the height of the top edge, then a Moon-pool with the water a foot below the top edge would have the same amount of water splashing out. That’s not too impractical, I don’t think.

[Sapo]

@Chronos

No, I meant in terms of depth, not the deck area around the pool. Like, if, in a normal Earthly pool, the water level is two inches below the height of the top edge, then a Moon-pool with the water a foot below the top edge would have the same amount of water splashing out. That’s not too impractical, I don’t think.

Oh. That makes a lot more sense.

[Stranger_On_A_Train]

@Chronos

The messy part is fluid drag, which is non-negligible here. Even in the textbook-ideal case, it depends on the shape of the object (and humans of course have a very complicated shape), and even with a simple shape it would leave you with a rather uglier differential equation to solve than in the constant-force case.

Just assume the horse is a sphere…

Stranger

[The_Scrivener]

Assuming the surface tension would remain unchanged, you could experiment with “will it sink or float?” stunts. On earth, to skate on the surface you’d have to be like a waterbug; but on the moon, maybe light coins and small pebbles (but not churches or witches) could rest on the surface of a very still pool of water.

Given the slower propagation of larger waves through the water, NASA would be well advised to make it a wave pool for body surfing. Hang ten!

[Bryan_Ekers]

Of course, the real engineering accomplishment won’t be a mere moon pool.
It’ll be a moon river!

[Civil_Guy]

Let me be one of the first of many to say:

I bet it would be wider than a mile.

[Bryan_Ekers]

Sure…
…some day.