David Hobby <[EMAIL PROTECTED]> asked
Robert--
You started all this. Am I right in thinking that you
WANT the habitat to have vaguely terrestrial weather? Something
like a layer of clouds a kilometer or two up? Sounds cool!
Almost: what I want to find out is whether clouds will form (for a
reasonable humidity at the surface, i.e., at the rim), and if they do
form, at what altitude? Let's presume a surface humidity of 50%.
(Incidentally, I have read that clouds formed in Zeppelin hangers in
conditions of high humidity, and that the big building at Cape
Canaveral for the Space Shuttle needs to have its air dehumidified
because of this danger!)
Going back to physical intuition again, it does seem
to me that we need to say which parts of the habitat are hot,
and which are cold. Weather is essentially a heat engine, so
the direction of heat flow should make a large difference.
Yes, this is true. Also, I realize that with a `tuna can' design, the
end caps are more important as heat sources than with a `cigarette'
design. Essentially, I think that the major source of heat is from
the `ground' at the surface, i.e., at the rim.
Basically, I am figuring that solar light and heat is reflected off a
central cone. Here is a diagram, but with the end caps bulging
outwards. The incoming sunlight (reflected from mirrors not shown)
comes through the top window (marked by the ^ ) and is reflected on to
the surface from a mirrored central cone (marked by the | and +):
_______^_______
/ \
| | |
| | |
| | |
\_______+_______/
The central cone is a mirror. It should not gain much heat from the
sunlight falling on it. I am thinking, but may be wrong, that with
this design, heat comes primarily from sunlight impinging on the
`ground', the surface at the rim. Some heat comes from sunlight
intercepted by the air and whatever is in it.
Not much direct light falls on the end caps, but indirect light falls
on them.
In so far as little direct light falls on the end caps, I think we can
figure that at each level, the temperature of surface substance of the
end cap will be a combination of the temperature of the air at that
altitude, the effect of indirect light, and conductivity through the
`ground'.
Presumably, the hull of a spinning habitat is constructed from a
nickle-iron asteroid. Besides being strong, nickle-iron is a good
conductor of heat. However, the surface materials inside the habitat
at the ends may well be a rock or regolith that conducts heat less
well than nickle-iron.
(Clearly, the `surface' at one gravity needs be like the regolith on
the moon, which is non-metalic. That oregolith needs to be planted
with enough worms, micro-organisms, and plants to turn into soil. A
long time ago, NASA planted some lunar regolith and found that it
turns into great dirt. You can grow plants on it just fine. I don't
know, but I hope that some asteroids have similar regolith.)
Presuming the end caps are mostly low-conductive stone or regolith,
the major temperature determiner for the end caps should be, I think,
the air, although indirect light will have an effect.
What do you think?
--
Robert J. Chassell Rattlesnake Enterprises
http://www.rattlesnake.com GnuPG Key ID: 004B4AC8
http://www.teak.cc [EMAIL PROTECTED]
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