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Viewing Single Post From: The giant space ship example
gbaikie

Chris Ho-Stuart
Dec 5 2011, 10:37 AM
gbaikie
Dec 5 2011, 06:33 AM
Now, it seems the most significant element is average atmosphere temperature- rather than ground temperature or surface air temperature.
Yes?
And next second important element would significant air mass "bordering/closest" to vacuum of space. And this second element I have no clue how to quantify.
So if second important element is not significant or could reduced somehow, then isn't first element to main factor in determining heat loss from atmosphere?


As the example of the Nitrogen/Oxygen atmosphere shows, we are going to need some measure of how effectively the atmosphere blocks infrared radiation. I'll be getting to that soon. With a transparent atmosphere (as you get with a mix of only O2 and N2) the heat loss from the atmosphere is zero; all the loss is from the surface directly. The atmosphere doesn't make any difference in this case.

When there is a non-trivial atmospheric absorption (absorptivity is a function of frequency and temperature) its gets more difficult, and this is the guts of the original problem you have posed. Basically, we need a way to describe the absorptivity of the atmosphere. If the atmosphere is N2, O2 and CO2 all well mixed, then we'll need the concentration of CO2, and some absorptivity data for CO2.


So from view of using the least amount energy [as 6,580,000 GigaWatts mind-boggling amount of energy] and in terms costs- making that many power plant costs zillions but nor is it cheap getting 5.4e17 kg of atmosphere or other elements.

It seem to me making the ground remains cold would be very easy comparatively. "Making cold" in space is far easier than it is on earth.

As I mentioned elsewhere one simply needs to not heat an area of the surface and result will be to collapse the atmosphere in that area.
Having a Niagara falls [to put it mildly] of the atmosphere, adds it's own complication, but the benefit is it gives is unlimited source "portable" cold. If you need rivers of liquid nitrogen that is doable.

The point is a model to understand climate, but I think being able to change variables provides different view and I think the benefit in terms of a starship of having some portion of planet have collapsed atmosphere would dictate having it.
Keeping the condition the same- 10 C surface temperature, global atmosphere, 1/10th gravity, and 1/3rd earth's atmospheric pressure is desired.
But also asking how you "save in costs", if say you have -20 C instead of 10 C; What happens if surface ground is much colder than 10 C; What if there was 1/5th instead of 1/3rd atmosphere is
also good.

I believe [perhaps as a crazy religion] that a purpose of science is to lower costs- science makes technology [and technology makes science]. Engineers are all about lowering costs. Exploration challenges science and technology [and by itself adds knowledge]. That democracy, science, exploration, freedom, trade, and happiness are an ecology- are interconnected and inalienable.
Therefore whatever is cheaper or more economical shouldn't be ignored- or is a tradition that shouldn't be dropped. And I am space cadet and an idea of some huge spaceship is too fascinating. :)

Anyways, your statement: "With a transparent atmosphere (as you get with a mix of only O2 and N2) the heat loss from the atmosphere is zero."

Is interesting. One aspect of having a large atmosphere was the idea of reducing loss of heat from the surface. It would great to have full atmosphere, but that seemed to make too complicated on 1/10th gravity world [I think the sheer distance/height of atmosphere would bring into play the gravity difference as factor. Even with this dwarf planet I am uncertain the molecule speed will not exceed it's gravity- and more atmosphere makes it more uncertain.].
And be easier if smaller world, but wanted enough gravity to get as much atmosphere as possible. Btw, this world's atmosphere is unlikely to survive near the sun [earth distance]- or at least it adds a lot of more complications and unknowns- like when would atmosphere be blown away by the sun within a year or decades/centuries

So it's your contention that there little or no difference if one had 1/5th earth pressure
as compared to 1/3?
One could also perhaps make it 1/2 earth atmospheric pressure. Half an Earth pressure could give atmospheric height perhaps as high as Neptune [though Neptune is massive and has much thicker atmosphere]. And the models of Neptune atmosphere are not very well defined.

Oh, I just thought of something, what does dust do in terms of heat. Low gravity world- lots of dust is fairly easy. It would interfere with beautiful view of the universe, but one could have as much dust as forest fire or volcano fairly easily.

Edited by gbaikie, Dec 5 2011, 06:57 PM.
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The giant space ship example · Physical theory for climate