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PostPosted: Thu Dec 17, 2015 4:01 pm 
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Ok, does anyone have recommend equations to determine the temperatures for the subsolar (100% day) and the anti-solar (100% night)? I used WBH, but I can't get anything that doesn't come across as uninhabitable. Temperatures on the dayside are so hot that all water boils off, while on the nightside even the atmosphere should freeze out. To prevent these two extremes from happening, one needs to have some reasonable amount of mixing that becomes a factor to offset Max+ and Max-. Or is it a case that all tidelocked worlds are indeed uninhabitable?

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PostPosted: Fri Dec 18, 2015 4:08 pm 
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For an example of a tidelocked world, look at the 2300AD adventure Kafer Dawn. Aurore, where the adventure takes place, is a tidelocked world orbiting what GDW alternately described as a gas giant and a brown dwarf in orbit around Eta Bootis. It may give you ideas of what to expect on a planet with a breathable atmosphere.

From what I recall, a tidelocked world with an atmosphere would theoretically be habitable, but only along a strip near the hot side of the terminator. If you're looking for a formula however, have you looked at this?

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PostPosted: Fri Dec 18, 2015 10:29 pm 
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Traveller wrote:
From what I recall, a tidelocked world with an atmosphere would theoretically be habitable, but only along a strip near the hot side of the terminator.


Yes, and the rules in WBH provide for that. The problem I had was that the ensuing equations for determining the sub-solar and anti-solar extremes made for such dramatic differences that I couldn't see how the planet would maintain a stable atmosphere or even hydrosphere. With temps on the sub-solar side well above the boiling point of water and below the freezing point of most gasses on the anti-solar side, I couldn't see how it would last.

Traveller wrote:
If you're looking for a formula however, have you looked at this?


No, I hadn't. Thank you! That gave me good numbers for the sub-solar, but still didn't convince me that an atmosphere could still exist under those extremes.

It might be that tide-locked worlds are atmospherically unstable and will be completely destroyed in a certain multiple of thousands of years (dependent upon mass). In order for them to be stable, there must be a significant warming effect due to hot winds blowing in from the dayside to offset the extreme cold of the nightside. If this is going to work in game terms (reality may eventually say, "No, not possible.") for me, I'm going to need some thermal moderation factor to plug in.

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PostPosted: Sat Dec 19, 2015 3:11 am 
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On another topic about tide locked worlds, we posited an ocean at the sub-solar. The water constantly evaporates and clouds cover the ocean (lowering the albeido and shading the surface), rise, get pushed towards the horizon and fall as rain. The rising heated steam and air will draw cold air at ground level from the horizon to the sub-pole. This creates a strong convection to at least moderate temperatures in the hemisphere.

It is just a concept.
The math to check it is beyond my experience and general interest.

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PostPosted: Sat Dec 19, 2015 4:32 pm 
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This Sky and Telescope article focuses primarily on moons, since virtually all moons are tidally locked, but its information should also apply in regards to tidally locked planets. In it, scientists at the Ames Research Center determined you only need a carbon dioxide pressure of between 1 and 1-1/2 atmospheres to not only make a tidelocked planet habitable, but also allow liquid water on the cold side. So, with sufficient CO2 in the atmosphere, there would be no problem with the atmosphere being warm enough.

The trick though is ensuring the planet has a dynamo, so the planet can generate a magnetic field to prevent the atmosphere from being stripped by the solar wind. Based upon information learned from the study of Io and Earth, there is a theory that sufficient tidal effects could allow for plate tectonics, leading to volcanism which would not only regulate the planetary temperature, but also fire up the dynamo necessary to generate a magnetic field.

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PostPosted: Mon Dec 21, 2015 6:37 pm 
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atpollard wrote:
On another topic about tide locked worlds, we posited an ocean at the sub-solar. The water constantly evaporates and clouds cover the ocean (lowering the albeido and shading the surface), rise, get pushed towards the horizon and fall as rain. The rising heated steam and air will draw cold air at ground level from the horizon to the sub-pole. This creates a strong convection to at least moderate temperatures in the hemisphere.

It is just a concept.
The math to check it is beyond my experience and general interest.


I would think that would indeed be more complex math than what normally appears in sourcebooks.

You don't happen to recall the title of that thread, do you? I'd be interested in reading it. If not, no sweat. I'll try some random searches.

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PostPosted: Mon Dec 21, 2015 7:07 pm 
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Traveller wrote:
This Sky and Telescope article focuses primarily on moons, since virtually all moons are tidally locked, but its information should also apply in regards to tidally locked planets. In it, scientists at the Ames Research Center determined you only need a carbon dioxide pressure of between 1 and 1-1/2 atmospheres to not only make a tidelocked planet habitable, but also allow liquid water on the cold side. So, with sufficient CO2 in the atmosphere, there would be no problem with the atmosphere being warm enough.

The trick though is ensuring the planet has a dynamo, so the planet can generate a magnetic field to prevent the atmosphere from being stripped by the solar wind. Based upon information learned from the study of Io and Earth, there is a theory that sufficient tidal effects could allow for plate tectonics, leading to volcanism which would not only regulate the planetary temperature, but also fire up the dynamo necessary to generate a magnetic field.


Thanks for the link!

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PostPosted: Mon Dec 21, 2015 10:44 pm 
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atpollard wrote:
On another topic about tide locked worlds, we posited an ocean at the sub-solar. The water constantly evaporates and clouds cover the ocean (lowering the albeido and shading the surface), rise, get pushed towards the horizon and fall as rain. The rising heated steam and air will draw cold air at ground level from the horizon to the sub-pole. This creates a strong convection to at least moderate temperatures in the hemisphere.


Wouldn´t that basically mean constant massive storms engulfing the entire planet?

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PostPosted: Tue Dec 22, 2015 9:49 pm 
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Sir Chaos wrote:
atpollard wrote:
On another topic about tide locked worlds, we posited an ocean at the sub-solar. The water constantly evaporates and clouds cover the ocean (lowering the albeido and shading the surface), rise, get pushed towards the horizon and fall as rain. The rising heated steam and air will draw cold air at ground level from the horizon to the sub-pole. This creates a strong convection to at least moderate temperatures in the hemisphere.


Wouldn´t that basically mean constant massive storms engulfing the entire planet?

OH YEAH, BABY!!

You want quiet, go settle on Mars. ;)

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PostPosted: Tue Dec 22, 2015 10:10 pm 
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Sir Chaos wrote:
atpollard wrote:
On another topic about tide locked worlds, we posited an ocean at the sub-solar. The water constantly evaporates and clouds cover the ocean (lowering the albeido and shading the surface), rise, get pushed towards the horizon and fall as rain. The rising heated steam and air will draw cold air at ground level from the horizon to the sub-pole. This creates a strong convection to at least moderate temperatures in the hemisphere.


Wouldn´t that basically mean constant massive storms engulfing the entire planet?


I think the subsolar point would be under a massive storm, but the rest of the dayside at least would have more normal circulation.

Folks should read Stephen Baxter's "Proxima" if they want a good idea of what a tidelocked world could be like.

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