Clouds/water vapor within a Von Braun wheel space station?

You might do a Youtube search on ISS video tours to get an idea on how water behaves in zero G. Generally, cut some water loose and you have small round droplets, until they evaporate and the excess moisture removed from the atmosphere from the climate control system. Using the restroom can be particularly challenging and potentially quite unpleasant.

I'm just curious here, but wouldn't the supposed simulated pull of gravity in a rotating wheel environment really be more of a centrifugal 'push' towards the outermost surfaces.

Hmmmm. But yes, I can see how one would have to exert muscle use to stay vertical. Intriguing.

Apologies for derail.

dpaterso said:

There's no push as such, mass wants to travel in a straight line, but the rotating wheel takes you in an arc instead, it's that difference in momentum that gives the impression of gravity and sticks you to the deck.

-Derek

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Ah! As usual there's a logical answer. Thank you, Derek.

Devil’s advocate: Why water crops the old-fashioned way? Why not use some form of drip-irrigation, to deliver water to roots? Is the station purposefully built to simulate planetary weather effects like clouds and rainfall?

Introversion said:

Devil’s advocate: Why water crops the old-fashioned way? Why not use some form of drip-irrigation, to deliver water to roots? Is the station purposefully built to simulate planetary weather effects like clouds and rainfall?

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They'd probably use hydroponics in a closed system rather than growing crops in soil. There are some very successful complete cycling systems with fish filtering the water, among other techniques.

Water doesn't tend to form a fine mist however. It will tend to clump together via surface tension in to spherical droplets. With no 'gravity' at the center, it's only the outward momentum of the sprinklers that will direct the water to the edges. It won't gain artificial gravity until it is accelerated laterally somehow. Also, due to the Coriolis effect, it will not land at the location at which it is aimed.

That said, it is a very bad idea to try to water your crops this way. Assuming an earth like atmosphere, your evaporation losses will be high. No, you want to apply the water locally.

FYI, some dynamics you need to know about your rotating gravity spaceship:

1. Coriolis effect. Maximum at the Earth's poles (your 'axle') and zero at the equator (your living surface at the edge of the ring.)

Case 1 - poles. Let's say you place an X at the end of a road going directly South from the North pole, and throw a rock at it. The rock will travel towards the initial position of the X, but since the earth is rotating, the X will move laterally and the rock will land some distance beside it. Now if you drove down that road, you would head towards the X but incur a lateral force (Coriolis Force) so you can be accelerated laterally to keep on track with the X.

Case 2 - Equator. You are standing on the equator and throw a rock due North down a road with an X painted on the end of it. This time you are standing 90 degrees from where you were standing on the pole, and travelling laterally at approximately 24,000 mph. If you throw a rock at the X, the rock has the lateral momentum built in to it so it continues to travel laterally and along with the line, and it hits the X. Drive down the road, no lateral force. On the earth, as you move down the lines of latitude towards the equator, the Coriolis effect gradually transitions from maximum to none.

2. Eotvos Effect. The Eotvos effect is an apparent change in gravity when travelling in an east-west direction, and is strongest at the equator, and zero at the poles. Eotvos was a Hungarian physicist that was the first person to be able to measure it. If you swing a rock tied to a rope, centripetal force will cause a tension on the string. If you swing it faster, it will place a greater tension. If you are standing on the equator, you are being pried off the surface of the earth with a very small centripetal force which will counteract gravity, so you will appear to weigh less. If you travel in the direction of the earth's rotation, there will be a greater force, and in the other direction, a lesser force.

The Germans tried to do some experiments around WWI firing artillery shells east and west. The earth rotates to the east. The shells should fly further to the east than to the west. The Germans did not find a difference within the accuracy of the guns. Years later Eotvos placed accelerometers in ships traveling to the east and west. An accelerometer is basically a big heavy mass suspended by a spring that measures its own weight. By examining the recordings, Eotvos was able to determine that the accelerometers registered lighter in the east direction than they did in the west, by the calculated amount.

MaeZe said:

They'd probably use hydroponics in a closed system rather than growing crops in soil. There are some very successful complete cycling systems with fish filtering the water, among other techniques.

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That's very true.

I suppose it depends on what style the OP is shooting for? If they want the visuals of "croplands in space", then go for it, just try to make it efficient because water falling from the "sky" is harder to manage and probably will rust the hell out of things they don't want it to.

Also, OP, consider that soil capable of growing things is a relatively rare and heavy commodity. The bigger your plantable fields, the more soil you had to 1) find or make, and 2) drag up there. Dunno how much world-building you want to do for this, but a couple of thoughts...

I doubt you'd want to just strip-mine planetary soil to do this? For one thing, the planet probably wants that soil. For another, "soil" is a complex ecosystem of fungi, micro-fauna, etc. J. Random shovel of soil is going to include pathogens, weed seeds, etc that you wouldn't want.

You could take regular soil, sterilize it, add back in the living stuff. You'd probably rather "make" your own soil in-situ, and carefully introduce the micro-flora and -fauna you want? Slow. Expensive, not sure how technically feasible it is -- you'd need rock ground to a fine powder (plenty of orbiting rocks to mine for that), carbon, nitrogen, potassium, phosphorous, trace minerals and who knows what else -- agronomists could maybe tell you? -- all mixed and "quickened" with the living stuff.

So much excellent sci-fi knowledge in this forum.

Warm air can hold more water than cold air . Warm wet , air will rise in the sky . As it rises up , it cools , the water turns into droplets and we see clouds . Warm air hitting something cold , the water turns into droplets , we see condensation. So if this space station is all the same temperature , everywhere. You would not have any clouds . You would have air conditioning , and extract the water . That is what happens in the current space station. If you wanted to have clouds in a space station you would needed to have on part heated and one part cold . The warm air moving into the cold part would shed it's water and form a mist .

Yo, Meteorologist here.

Cloud formation is going to depend on the temperature and density of the air between the source of the water and where it's going. If there is 'space' in between or very little atmosphere, you won't get clouds and the water molecules will just disperse in all directions. If there is an atmosphere, then what happens with the clouds will depend on the structure of the atmosphere.

I'm guessing the most likely case is the atmosphere is more dense near the edge of the drum. In this case, the stuff coming out of the sprinkler (unless it's a giant hose it should be air with some water vapour) will move outwards until it reaches a point where the density of the atmosphere equals the density of the stuff coming out of the sprinkler. If enough of that stuff clumps together you'll get clouds. Assuming there is constant heating (eg. no tilt like on Earth) then the clouds should form around the same height.