Implications of a terraformed Venus/Triton

[Anthony]

It would be possible to terraform Venus without moving it if you added an enormous solar shade (it has to cover a bit under half of the sun). Probably something at L1 that uses solar sails for station keeping; it would be about a million kilometers away, 10,000 kilometers across, and would probably cause a permanent annular eclipse of the sun (which would vary in position noticeably over the course of a day).

This is still a ridiculous engineering task, and would be greatly complicated by adding a moon (so I suggest no moon), but it's not out of scale compared to all the other ridiculous engineering tasks involved in terraforming Venus.

[acrosome]

Originally Posted by Anthony

It would be possible to terraform Venus without moving it if you added an enormous solar shade (it has to cover a bit under half of the sun). Probably something at L1 that uses solar sails for station keeping; it would be about a million kilometers away, 10,000 kilometers across, and would probably cause a permanent annular eclipse of the sun (which would vary in position noticeably over the course of a day).

Yes. That'd be the statite soletta that I mentioned. Since L1 isn't terribly stable, it would need the statite stationkeeping mechanism.

To see the soletta you'd have to look directly at the sun, which we all know doesn't work very well. But if you had proper lenses, or a camera obscura, or whatnot, would you be able to see it? Maybe only as a sort of "diffraction pattern"?

Hmm.

[sir_pudding]

Pamela Sargent's Venus trilogy features a Venus terraforming project.

[Anthony]

Originally Posted by acrosome

YTo see the soletta you'd have to look directly at the sun, which we all know doesn't work very well. But if you had proper lenses, or a camera obscura, or whatnot, would you be able to see it? Maybe only as a sort of "diffraction pattern"?

If the structure is diffuse and just lets half the sunlight through, probably not. If the structure is opaque and just smaller than the sun, you can view it the same way you view a solar eclipse -- any time sunlight passes through a narrow hole to produce a dot further away (such as just passing through holes between tree leaves) the dot of light has the same shape as the sun (I watched the total eclipse in August. Near totality shadows just felt weird and wrong).

[acrosome]

Originally Posted by sir_pudding

Pamela Sargent's Venus trilogy features a Venus terraforming project.

Huh. Never heard of her. Looking at her biliography I can see why- lots of YA stuff and some mass-market Star Trek crap. But her earlier stuff might be interesting, like the trilogy you mention. And considering my project it would almost be required reading, wouldn't it? I'll Kindle it.

Originally Posted by Anthony

If the structure is diffuse and just lets half the sunlight through, probably not. If the structure is opaque and just smaller than the sun, you can view it the same way you view a solar eclipse -- any time sunlight passes through a narrow hole to produce a dot further away ... the dot of light has the same shape as the sun.

The designs I've seen are neither of those. Instead they are a series of concentric circular mirror rings that reflect a certain percentage of light away from the planet. This allows management of the statite effect (i.e. maneuvering) by changing the angle of the mirrors. Well, actually, most designs I've seen were for Mars terraforming, and thus reflected more light into the planet... but it would work just as well in reverse.

The question then, I guess, is how large are the individual circular mirrors? Answer: since I find the idea of using a camera obscura to see it interesting, rather large! I'll fiat say that you need a really large one to see it, though, like a literal room in a castle or something.

And, actually, I have just the group in mind to have discovered this...

Note to self: the sun appears just over 1/3rd larger from Venus.

Anyone have answers on how ridiculous the Titan energy budget would be? Do I have to live without a moon? Or for the smaller Venus orbital adjustment?

[sir_pudding]

Originally Posted by acrosome

The designs I've seen are neither of those. Instead they are a series of concentric circular mirror rings that reflect a certain percentage of light away from the planet. (Actually, most designs I've seen were for Mars terraforming, and thus reflected more light into the planet... but it would work just as well as I described.)

The books I mentioned use exactly this, and I think she even gives some hard numbers.

[Anthony]

Originally Posted by acrosome

Anyone have answers on how ridiculous the Titan energy budget would be? Do I have to live without a moon? Or for the smaller Venus orbital adjustment?

Maybe a tenth the energy requirement in either case? Still a lot.

Incidentally, a shield has dramatically different orbital requirements from a magnifier; while L1 is not stable, it doesn't require anything more than station keeping to stay there, unlike the proposed Mars mirrors (you can think of the Lagrange points as flat areas on surface. As such, it doesn't take any force to stay there. However, L1, L2, and L3 are like flat points at the top of a hill, so if you move you start rolling down the hill. L4 and L5 are like flat points at the bottom of a depression, so stuff tends to get stuck there). Station keeping would involve either adjusting the amount of sunlight passing through, or deflecting it to one side or the other instead of straight towards the sun.

[acrosome]

Originally Posted by Anthony

Maybe a tenth the energy requirement in either case? Still a lot.

Incidentally, a shield has dramatically different orbital requirements from a magnifier; while L1 is not stable, it doesn't require anything more than station keeping to stay there, unlike the proposed Mars mirrors (you can think of the Lagrange points as flat areas on surface. As such, it doesn't take any force to stay there. However, L1, L2, and L3 are like flat points at the top of a hill, so if you move you start rolling down the hill. L4 and L5 are like flat points at the bottom of a depression, so stuff tends to get stuck there). Station keeping would involve either adjusting the amount of sunlight passing through, or deflecting it to one side or the other instead of straight towards the sun.

I'm not following the difference you propose for shields vs. mirrors. Are you talking about defelecting away vs. towards the planet? If so, I fail to see how that could be so. But if you mean a literal solid shade versus a mirror, yes, I understand. Though even a shade could work if it was maneuvered by how angled it was to incident sunlight, and large enough that even when angled it still shaded the entire planet.

And in which case I have already mentioned the soletta being concentric circular mirrors. And I grok Lagrangian points, at least minimally:

Originally Posted by acrosome

Since L1 isn't terribly stable, it would need the statite stationkeeping mechanism.

But it sounds like you are saying that moving Triton isn't very do-able. Can anyone think of better options for a moon that's reasonably massive? (I assume not.)

[Fred Brackin]

Originally Posted by acrosome

But it sounds like you are saying that moving Triton isn't very do-able. Can anyone think of better options for a moon that's reasonably massive? (I assume not.)

Use superscience and move anything you want to. For anyone limited to hard science O'Neill habs are pretty much always a better option.

[Anthony]

Originally Posted by acrosome

I'm not following the difference you propose for shields vs. mirrors.

There is no easy orbital position that is useful for capturing extra sunlight for a planet. There is a point that is useful for deflecting sunlight away from a planet.

Originally Posted by acrosome

But it sounds like you are saying that moving Triton isn't very do-able. Can anyone think of better options for a moon that's reasonably massive? (I assume not.)

Other than massive and convenient coincidence, no.