Meteorology within a hollow space colony - Cloud formations determination

dicktice · 2004-09-26 18:57:05

I've been struggling with how to determine what the cloud formations would be within a hollow spinning asteroid (say) six miles inside diameter and ten miles long. Given reflected sunlight entering from either end, according to a 24-hour day/night cycle, what form would the cumulus clouds take as the result of convection thermals "rising" from the floor of the crop-growing and irrigated cylindrical valley floor, towards the spin axis? Assuming one-gee of simulated sea level gravity, and one-bar of Earth-normal atmospheric pressure, at the valley floor, the gravity goes to zero at the spin axis while the air pressure reduces to that of fifteen thousand feet, on Earth. With temperatures ranging from 100C here and there around the floor, to 0C at the spin axis, I imagine a sausage-shaped cloud-base at a condensation level of ten thousand feet (say), but what form the "tops" inside the sausage would take, has me befuddled. Adiabatic lapse-rate in a diminishing gravity field lies at the heart of my befuddlement. Any meteorologuists out there care to tackle this problem?

Palomar · 2004-09-26 19:12:34

*Perhaps theories about cloud development in an O'Neill Cylinder would provide some insights? It seems the "hollow spinning asteroid" you're musing about is similar, if not the same thing.

--Cindy

:edit: Heres]http://www.newmars.com/forums/viewtopic.php?t=3121]Here's a very old thread which contains related links. The meterological aspect was mentioned. Hope that helps.

dicktice · 2004-09-28 10:06:33

Thanks, Cindy--while those old posts, particularly Byron's, agree that the condensation "level" cloud bases due to convection thermals, would tend to appear (from the cylindrical valley floor) to be smooth and cigar-shaped, the shape of the "tops" inside the cloud formation (viewed along the spin axis from either hub) could not have been as shown. Meteorology of a O'Neill Cylinder may not been modeled, even yet. If not, what a great dissertaion for some up-and-coming meteorologist post-doc to take up! We're talking here, about heat-of-condensation cloudtop formation under conditions of buoyancy diminuation with alltitude, along with atmospheric pressure. Perhaps a new chart of adiabatic lapse rate for this, as yet not encountered model of an atmosphere, can be produced, for starters. Then, maybe we can all have a realistic discussion about what form the cloud "tops" would take, under varying weather conditions including freezing levels, within an O'Neill space colony.

Palomar · 2004-09-28 10:29:42

Meteorology within an O'Neill Cylinder may not yet have been analyzed. If so, what a great subject for some up and coming meteorologist to tackle.

*I couldn't agree more. I've seen a different illustration -- a "cutaway" artist's conception -- of clouds within an O'Neill Cylinder. They were portrayed as nimbus in appearance...but of course the artist may have known as much about meterology as I do...which isn't saying much. :laugh:

OC's interest me very much. Seems they are unfortunately considered something along the lines of curiosity relics of yesteryear.

--Cindy

dicktice · 2004-09-28 10:49:58

Small helium balloons are used to investigate the temperature inversion layers above cities, which they tend to define as they drift about within the air mass--under calm wind conditions. Such balloons, "released" inside a computer-generated virtual O'Neill Cylinder viewed as you say, in cross-section, might be a way to leapfrog the intermediate, adiabatic lapse chart stage, in order to obtain a realistic picture of the clouds to be expected under different controlled seasonal weather onditions.

Grypd · 2004-09-28 15:31:35

This makes for an interesting point what will happen if there is a fire where will the smoke go and how do we get rid of it?

RobS · 2004-09-29 11:36:05

I think you have to resolve some aspects of the design of the hollow asteroid before answering some of your questions.

1. If sunlight is shining in either or both ends of the asteroid through a small window, at great intensity, what is its distribution on the asteroid's "floor"? For example, if it shines in the north polar window and illuminates the entire southern hemisphere, the south pole will receive the most intense, straight-on vertical heating; the equator will receive the least heating because the light will be coming in most diagonally and because the equator will have a larger surface area. But the pole is already at the height of the clouds whereas the floor is way "down." So your thermal model can't simply assume the highest temperature at the ground level and adiabatic decreases with height, because of the high altitude "mountain" receiving intense sunlight at the opposite pole.

Making all of this more complicated, the sunlight will be shining horizontally straight through your clouds, heating them directly, especially the ones closest to the window; they might get several times more solar intensity per square meter than the equatorial floor. The clouds will also shadow the floor big time; a small cloud in the right place and the entire asteroid interior would be "overcast" until the cloud evaporates in the roasting heat. It may be that insolation will make the central axis the hottest spot.

2. Where will all these gigajoules of heat coming into the interior go? How will they be removed? Perhaps when the sun is shining in one end of the asteroid, there will be airconditioning working at the other end. The air conditioning could be a gigantic transparent tube running the axis of the asteroid with small holes in it. Huge fans would suck air into the axial tube from the cloud tops. Once in the axial tube the air would heat up enough to evaporate water droplets (because of the intense sunlight in the axis), so it would be transparent and wouldn't significantly block the passage of light through the axis. The air would then be pulled out of the asteroid, cooled in a gigantic heat exchanger, probably filtered, and the air would be readmitted into the interior, probably at the ground level. Think of the energy a system like this would take! If the system were reversed and air were taken out at ground level, cooled, and blown back into the asteroid through the central axial tube, you'd get clouds and rain real fast! So rather than computer modeling the weather, one would be computer controling the weather instead.

I think you will find that the energy demands for a system like this is mind-boggling. A six mile diameter, ten mile long cylinder is 10 kilometers by 16, the diameter produces a circumference of 31 kilometers, so the surface area inside is something like 496 square kilometers or 4,960,000 square meters. Assuming 1 kilowatt of sunlight per square meter, that's 5 million continuous kilowatts of sunlight, which becomes 5 million continuous kilowatts of heat to remove from the interior. A damn big air conditioner! It probably would require 1,000 square kilometers of radiator panels outside the asteroid!

- RobS

dicktice · 2004-09-29 13:27:00

Whoa, there: My intention in posing my question wasn't to start a discussion regarding the feasibility of a hollow asteroid design. That will be taken up later, but assuming all that has been accomplished--as a thought problem--what form will convection clouds takd from one-gee to zero-gee, viewed in cross-section?

Palomar · 2004-10-01 07:49:49

*Yeah, Rob, what's up with that? Trying to rain on dicktice's parade or something? :;): (Just kidding)

Dicktice: Why a hollowed-out asteroid? Why not just go with an O'Neill Colony?

I hope you also don't mind my asking: Is this part of a fiction story you're working on?

--Cindy

MarsDog · 2004-10-05 11:58:20

a hollow sphere does not produce any gravity inside. The gravitational field inside is the same as if the hollow sphere were not there (i.e. the field is that of any masses inside and outside the sphere only)

http://www.wordiq.com/definition/Divergence_theorem]No gravity inside hallow sphere. As if the spherical shell did not exist,
other than for preventing radiation and gasses from escaping.
-
However, once you put things inside. it will tend to clump,
not necessarily at the center of the hallow sphere.
-
Water vapor is lighter, so it will rise to the outside of the clump, and eventually the heavier things will drift towards the center, due to gas pressure differentials.
-
Cooling would be convenient;
since the water vapour would condense on the inside of the spherical shell,
and fall very slowly as large drops or as hail.
Raindrops as large as beachballs, due to very low gravity.
-
Adding rotation would counteract gravity; settling the contents into a ring.
Leading to an internal torus arrangement, in the equatorial plane,
The clouds would form and drift towards the center,
requering a cooling system at the center to form water.
The rain would fall from the center
-
Lenghtening the torus gives a cylinder. Gravitational bunching at the center.
The clouds squeezed towards the ends; cooling could take place, with the water slowly flowing back towards the center.
One large axial centered cloud, conveniently spreading over the cooler heat exchangers at the ends.
There would be turbulence and shearing effects, decreased rotation near the ends, due to conservation of angular momentum. A low pressure system centered along the axis.
-
Optimized tubeworlds are the most convenient way to set up the water cycle.
Air circulation and heat regulation combined in a large heat pipe.
Heating near the center, expanding the air and introducing moisture.
Cooling, condensing, making more dense at the ends, forms a large heat engine.
Maybe even set up windmills to generate electricity.

dicktice · 2004-10-07 16:13:23

MarsDog: Very interesting, but you and the others avoid the appearance the inside of the convection "sausage cloud" would present to someone looking along the spin axis, where the air pressure is equivalent to 15,000 feet altitude on Earth, but the gravity zero.
Cindy: The answer to your query, if you must know, is yes. . . .

MarsDog · 2004-10-07 19:19:02

Won't be any clouds or convection at thermal equilibrium.
Initially, a sausage cloud will form, but settle out as the heat flow stops.
-
A cloud is composed of very small liquid droplets or ice particles.
Coalescing and falling faster, as the droplets get larger.
Even in very low gravity, the droplets will settle out as dew or frost, eventually.
-
In order to form clouds, dew point conditions have to be induced.
-
To make more clouds, You could cool (air condition) the center of the sausage cloud,
or let saturated air rise, it will cool below the dew point, as a result of expansion; and collect the IR radiation into a "light pipe", and exhaust it into the 2.7K outside thermal background.
-
If you let heat in one end and exhaust it at the other, you would have a cylidrical cloud forming from evaporation, along the axis, moving towards the heat exhaust end, and condensing there. If the tube were slightly wider at the hotter, evaporation end, the water could flow "downhill" from the cooler end.
-
In a long spinning tube, the cloud would get bigger at the ends, and a heat exchanger, there, could conveniently dispose of the heat, continuing the http://ga.water.usgs.gov/edu/watercycle.html]water cycle. Note that the clouds are formed in the http://www.kidzone.ws/water/]condensation part of the cycle; changing from gas to liquid; where the heat of condensation is radiated.

srmeaney · 2005-03-19 05:06:47

Your best comparison would be a permanent Cyclone moving with a core rotational velocity of 100 kph that turns about the center of the cylinder (possibly driven by a giant wind turbine).

MarsDog · 2005-03-19 06:02:50

Your best comparison would be a permanent Cyclone

First guess is from http://csep10.phys.utk.edu/astr161/lect … nservation of Angular Momentum.

In order to have differential rotation, density has to change over time. Otherwise, frictional effects will equalize the spin rate.

It would be interesting to figure out the effect on the http://en.wikipedia.org/wiki/Precession]precession of the cylinder's rotation. For example, what would happen if you moved the heat exchangers, changing the mass distribution of the atmospheric flow.

dicktice · 2005-03-19 06:35:12

The hollow "ecoshell," within the spinning asteroid, as I imagine it, would be formed by swinging a chain along the spin axis, a catenary hollow in effect, 15 miles long by 6 miles in diameter, so that 1-gee occurs around the roughly cylindrical valley thus formed, and 0-gee along the axis of this 0.5 rpm rotating volume. Heat and light are brought in through 2,000 ft diameter fused quartz light pipes from the outside (rotational axis normal to the ecliptic) and dispersed by concave, zoned lens surfaces from either end to the opposing hemispheres of terraced living space. Night is simulated by blocking the light (never mind how), morning by light from the "east" end only, midday by light from both ends, and afternoon by light form the "west" end only. With 1-bar at the "bottom" of the valley "floor" the pressure altitude along the spin axis would be that at 15,000 feet on Earth. Solar heating of the valley during the day should produce thermal activity, resulting in culmulus cloud build-up with a cylindrical cloudbase 10,000 feet at intermediate-gee. Radial rain occurs when the clouds grow high enough, and snow higher up still, so that the spin axis has a polar climate while the valley floor is subtropical.Now, having set up my thought problem, I can't decide on the formation of the cloud "tops" withing the sausage formation surrounding the spin axis, during the passage of each "day."

MarsDog · 2005-03-19 16:03:10

http://mathworld.wolfram.com/Catenary.html]The curve a hanging flexible wire or chain assumes when supported at its ends and acted upon by a uniform gravitational force.

Greatest artificial gravity is at the greatest distance from the axis of rotation.
Hence the formation of a lake.

Starting from a cool lake and atmosphere.
Heating the lake causes evaporation and increase in humidity and air temperature.
The warm humid air rises and cools untill the relative humidity is 100 percent.
Clouds then form in a hallow cylindrical shape, along the axis of rotation.

The clouds, composed of small water droplets, gave up heat when the water wapor condensed into droplets. What you have is similar to a http://www.benchtest.com/heat_pipe1.html]heat pipe which distributes heat to even the temperature throughout. Eventually, all the droplets "fall" and thermal equilibrium is established.

The crucial decision is how the heat escapes.
The clouds will flow towards the heat exchanger.

dicktice · 2005-03-19 17:30:57

The curve formed by the nonuniform gravity field is "catenary-like" for purposes of the thought problem. The "cylinder-like" valley floor could become a lake, perhaps, but the "hemispherical-like" slopes are solar heated from opposing dispersion lenses at either end of the hollow spinning asteroid, producing thermals that rise radially like bicycle spokes, to form an "axel-like" cloudbase at the condensation "level", and beyond due to heat of condensation.... But then, what? Lumpy ice cloud? As for equilibrium being obtained, I don't think so.Precipitation rather, in the form of (radial) rain and/or hail accelerating to the valley floor, and snow accumulations causing low-gee avalanches surrounding the 2,000 ft diameter lenses, which cycle on and off to simulate 24-hour day and night. The inner-most zone of each lens should probably be convex with a 15-mile focal length, to focus on the hub of the opposing lens, to keep the spin axis clear. Quite a "weather machine," as a matter of fact, but the cloud formations between 10 and15 thousand feet (with the gees ranging from 0.6 to 0, say)gee) have me stumped.

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#1 2004-09-26 18:57:05

Re: Meteorology within a hollow space colony - Cloud formations determination

#2 2004-09-26 19:12:34

Re: Meteorology within a hollow space colony - Cloud formations determination

#3 2004-09-28 10:06:33

Re: Meteorology within a hollow space colony - Cloud formations determination

#4 2004-09-28 10:29:42

Re: Meteorology within a hollow space colony - Cloud formations determination

#5 2004-09-28 10:49:58

Re: Meteorology within a hollow space colony - Cloud formations determination

#6 2004-09-28 15:31:35

Re: Meteorology within a hollow space colony - Cloud formations determination

#7 2004-09-29 11:36:05

Re: Meteorology within a hollow space colony - Cloud formations determination

#8 2004-09-29 13:27:00

Re: Meteorology within a hollow space colony - Cloud formations determination

#9 2004-10-01 07:49:49

Re: Meteorology within a hollow space colony - Cloud formations determination

#10 2004-10-05 11:58:20

Re: Meteorology within a hollow space colony - Cloud formations determination

#11 2004-10-07 16:13:23

Re: Meteorology within a hollow space colony - Cloud formations determination

#12 2004-10-07 19:19:02

Re: Meteorology within a hollow space colony - Cloud formations determination

#13 2005-03-19 05:06:47

Re: Meteorology within a hollow space colony - Cloud formations determination

#14 2005-03-19 06:02:50

Re: Meteorology within a hollow space colony - Cloud formations determination

#15 2005-03-19 06:35:12

Re: Meteorology within a hollow space colony - Cloud formations determination

#16 2005-03-19 16:03:10

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#17 2005-03-19 17:30:57

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