Author Topic: Sun Shade concepts for Venus  (Read 44286 times)

Offline AlexCam

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Sun Shade concepts for Venus
« on: 09/10/2011 04:12 PM »
I know that all those large scale sun shade concepts for Earth that were floating around have turned out to be impracticable to implement or just to damn expensive. But what about Venus?

I wonder whether there are alternative ways to cooling Venus which use the sun shade concept, but use novel ideas. I have seen proposals for orbital sun shades around Venus, but those don't really are any easier to implement than a stationary Venus-Sun L-point based flat sun shade.

There are concepts that talk about seeding the Venusian atmosphere with genetically modified algae, principally that was proposed to modify the atmosphere. But what about injecting substances (organic or other) into the upper atmosphere that can build up some kind of reflective layer using atmospheric particles as building blocks that can effectively shade sunlight? Such a floating "dimming layer" might just be a cheap solution to cooling Venus to the point where CO2 ice forms and only a 3-4 bar atmosphere remains that is mostly nitrogen (bearable for humans at surface altitudes with breathing equipment).

Even more so, if this layer could be controlled it could simulate a 24 hour day cycle at some point in the future.

Offline aquanaut99

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Re: Sun Shade concepts for Venus
« Reply #1 on: 09/10/2011 04:16 PM »
Erm, if sun shade concepts for Earth are impracticable or too expensive, what makes you think they will be cheaper on Venus???

What am I missing here...

Offline AlexCam

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Re: Sun Shade concepts for Venus
« Reply #2 on: 09/10/2011 04:27 PM »
Erm, if sun shade concepts for Earth are impracticable or too expensive, what makes you think they will be cheaper on Venus???

What am I missing here...

Earth's atmosphere is 1 bar, Venus' atmosphere is 93 bar.

And we can (and are) shading the sun on Earth already (see Global Dimming), however it's pretty unlikely anyone would propose a radical concept of releasing lots of aerosols into the Earth's atmosphere to experiment with atmospheric sun shading to combat global warming.

I probably should have been clearer, BOTH sun shades for Earth and Venus which are space based are impracticable and too expensive. That's why I asked about new, different sun shade concept for Venus that use the specific properties of the Venusian atmosphere.

Offline aquanaut99

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Re: Sun Shade concepts for Venus
« Reply #3 on: 09/10/2011 04:40 PM »
Earth's atmosphere is 1 bar, Venus' atmosphere is 93 bar.

And we can (and are) shading the sun on Earth already (see Global Dimming), however it's pretty unlikely anyone would propose a radical concept of releasing lots of aerosols into the Earth's atmosphere to experiment with atmospheric sun shading to combat global warming.

I probably should have been clearer, BOTH sun shades for Earth and Venus which are space based are impracticable and too expensive. That's why I asked about new, different sun shade concept for Venus that use the specific properties of the Venusian atmosphere.

Ah ok, now I understand.

BTW, you're wrong about intentional aerosol release to combat global warming, it HAS been proposed. Problem is, it would only work if we keep it up for ever...

Offline Hop_David

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Re: Sun Shade concepts for Venus
« Reply #4 on: 09/10/2011 04:50 PM »
I know that all those large scale sun shade concepts for Earth that were floating around have turned out to be impracticable to implement or just to damn expensive. But what about Venus?

I wonder whether there are alternative ways to cooling Venus which use the sun shade concept, but use novel ideas. I have seen proposals for orbital sun shades around Venus, but those don't really are any easier to implement than a stationary Venus-Sun L-point based flat sun shade.

There are concepts that talk about seeding the Venusian atmosphere with genetically modified algae, principally that was proposed to modify the atmosphere. But what about injecting substances (organic or other) into the upper atmosphere that can build up some kind of reflective layer using atmospheric particles as building blocks that can effectively shade sunlight? Such a floating "dimming layer" might just be a cheap solution to cooling Venus to the point where CO2 ice forms and only a 3-4 bar atmosphere remains that is mostly nitrogen (bearable for humans at surface altitudes with breathing equipment).

Even more so, if this layer could be controlled it could simulate a 24 hour day cycle at some point in the future.

Recently Isaac Kuo posted this pdf which lays out a plan to capture an asteroid by exploiting 3 body interactions.

The talk about the comet Oterma which moves back and forth through Jupiters' realm as it moves between the sun's realm and exterior realm.



Baoyin et al look for an asteroid that drifts by sun earth L1 and L2 necks much as Oterma drifts by the Sun Jupiter L1 and L2 necks. With relatively little delta V (.4 km/sec) they propose to catch an asteroid near the boundaries of earth's sphere of influence.

For shading Venus, I would look for an asteroid that drifts by the Sun-Venus L1 or L2 necks and nudge this body into a halo orbit about Sun-Venus L1. After the asteroid is parked at SVL1, start disassembly to make a shade.

This is all science fiction, mind you.

Offline N45deg

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Re: Sun Shade concepts for Venus
« Reply #5 on: 09/11/2011 12:43 AM »
Recently Isaac Kuo posted this pdf which lays out a plan to capture an asteroid by exploiting 3 body interactions.

The talk about the comet Oterma which moves back and forth through Jupiters' realm as it moves between the sun's realm and exterior realm.



Baoyin et al look for an asteroid that drifts by sun earth L1 and L2 necks much as Oterma drifts by the Sun Jupiter L1 and L2 necks. With relatively little delta V (.4 km/sec) they propose to catch an asteroid near the boundaries of earth's sphere of influence.

For shading Venus, I would look for an asteroid that drifts by the Sun-Venus L1 or L2 necks and nudge this body into a halo orbit about Sun-Venus L1. After the asteroid is parked at SVL1, start disassembly to make a shade.

This is all science fiction, mind you.
[/quote]Why not just send your science fiction asteroid directly to impact Venus. Instant cooling effect with a smaller asteroid and then start the the science fictional mass rocket launches to populate. javascript:void(0);

Offline Moe Grills

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Re: Sun Shade concepts for Venus
« Reply #6 on: 09/16/2011 01:08 AM »
I know that all those large scale sun shade concepts for Earth that were floating around have turned out to be impracticable to implement or just to damn expensive. But what about Venus?

   Aha! I know what you're getting at!
Terraforming Venus, right?

Problems with idea?

Yes, lots.
 Let's start with financing.
Terraforming will cost trillions & trillions of dollars.
More money than available & in circulation in the United States today.

Second: Reducing sunlight on Venus will cool its atmosphere down somewhat; but it still will have an atmosphere with a pressure strong enough to crush a Brinks armored car like an empty beer can.
How are you going to eliminate most of the venusian atmosphere
to reduce pressure at its surface to tolerable levels?

And then there's carbon dioxide...way too much carbon dioxide.
You can use genetically modified bacteria to convert the CO2 into O2;
But then an atmosphere of high-pressure enriched oxygen will be
very corrosive.
 You need billions of trillions of tons of nitrogen to dillute the
(hypothetically)  enriched oxygen atmosphere.
Where are you going to get the huge quantities of nitrogen for the planet?

And Venus has no magnetic field.
How are you going to create a planetary magnetic field there?

And Venus takes 243 days to rotate on its axis.
How are you going to speed up the rotation 100-200 times?

I'm not being sarcastic, nor am I being blasphemous nor profane when I say that you are
trying to tackle a planetary scale problem without Godlike powers. 

« Last Edit: 09/16/2011 01:15 AM by Moe Grills »

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #7 on: 09/16/2011 10:35 AM »

Problems with idea?

Yes, lots.
 Let's start with financing.
Terraforming will cost trillions & trillions of dollars.
More money than available & in circulation in the United States today.

Well it's something that's only worth considering for the future, under different economic and technological circumstances, todays global economy is substantially larger than that of 1911, who knows what the wealth and technology of 2111 will make possible.

Quote
Second: Reducing sunlight on Venus will cool its atmosphere down somewhat; but it still will have an atmosphere with a pressure strong enough to crush a Brinks armored car like an empty beer can.
How are you going to eliminate most of the venusian atmosphere
to reduce pressure at its surface to tolerable levels?

And then there's carbon dioxide...way too much carbon dioxide.
You can use genetically modified bacteria to convert the CO2 into O2;
But then an atmosphere of high-pressure enriched oxygen will be
very corrosive.
 You need billions of trillions of tons of nitrogen to dillute the
(hypothetically)  enriched oxygen atmosphere.
Where are you going to get the huge quantities of nitrogen for the planet?

Freeze the CO2 out at a suitable location to form a mass like the Antarctic ice cap, all you're left with is an N2 atmosphere of around 3 bars pressure, and if necessary liquefy some of that in a crater on your CO2 ice cap.
The biggest challenges will be deflecting the comets needed to form seas and getting the atmospheric O2 levels up in an acceptable time frame
Quote
And Venus has no magnetic field.
How are you going to create a planetary magnetic field there?

Why do you need a magnetic field? You won't lose atmosphere that fast as a result of particle impacts, and the atmosphere itself will be adequate radiation protection for life on the surface.

Quote
And Venus takes 243 days to rotate on its axis.
How are you going to speed up the rotation 100-200 times?

If you can use space shields to block sunlight from the planet to cool it down quickly, you can use space mirrors to reflect sunlight to keep some parts of the surface in permanent shade (the CO2 ice cap), and have whatever length of day you want over the rest of the planet by blocking sunlight on the sun-ward side and reflecting sunlight onto the shadowed side (you could even have the whole planet on a synchronized day-night cycle so everyones in the same time zone). If you can't form an ozone layer because of the lack of magnetic field, you can have UV absorbent filters on such space Sun-shields and mirrors .
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Offline gospacex

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Re: Sun Shade concepts for Venus
« Reply #8 on: 09/16/2011 01:02 PM »
Quote
Second: Reducing sunlight on Venus will cool its atmosphere down somewhat; but it still will have an atmosphere with a pressure strong enough to crush a Brinks armored car like an empty beer can.
How are you going to eliminate most of the venusian atmosphere
to reduce pressure at its surface to tolerable levels?

And then there's carbon dioxide...way too much carbon dioxide.
You can use genetically modified bacteria to convert the CO2 into O2;
But then an atmosphere of high-pressure enriched oxygen will be
very corrosive.
 You need billions of trillions of tons of nitrogen to dillute the
(hypothetically)  enriched oxygen atmosphere.
Where are you going to get the huge quantities of nitrogen for the planet?

Freeze the CO2 out at a suitable location to form a mass like the Antarctic ice cap,

That'd be more like a kilometer-thick layer of solid CO2 over entire planet.

Even if you block the Sun completely, it will take centuries for all CO2 to freeze.

Offline KelvinZero

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Re: Sun Shade concepts for Venus
« Reply #9 on: 09/16/2011 01:22 PM »
Quote
Second: Reducing sunlight on Venus will cool its atmosphere down somewhat; but it still will have an atmosphere with a pressure strong enough to crush a Brinks armored car like an empty beer can.
How are you going to eliminate most of the venusian atmosphere
to reduce pressure at its surface to tolerable levels?

And then there's carbon dioxide...way too much carbon dioxide.
You can use genetically modified bacteria to convert the CO2 into O2;
But then an atmosphere of high-pressure enriched oxygen will be
very corrosive.
 You need billions of trillions of tons of nitrogen to dillute the
(hypothetically)  enriched oxygen atmosphere.
Where are you going to get the huge quantities of nitrogen for the planet?

Freeze the CO2 out at a suitable location to form a mass like the Antarctic ice cap,

That'd be more like a kilometer-thick layer of solid CO2 over entire planet.

Even if you block the Sun completely, it will take centuries for all CO2 to freeze.

I wonder. I have heard that stated before I think based on actual data of how venus is now, but does Venus's atmosphere mix much in its current state? I thought it was sort of stagnant and slow moving at the bottom. The sort of dramatic cooling we are discussing, especially if focused, could probably create massive permanent storms sucking super hot atmosphere up from the depths. Was this taken into account?

Offline peter-b

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Re: Sun Shade concepts for Venus
« Reply #10 on: 09/16/2011 01:24 PM »
It seems to me that lowering Venus' surface temperature would be far far easier than the next step: introducing the gigatonnes of hydrogen needed to fix its atmosphere's elemental balance.  :(

(This is the way to reduce atmospheric pressure, BTW; carbon sequestration by limestone formation on a geological timescale, coupled with conversion of atmospheric oxygen into water by the addition of hydrogen to the atmosphere).

As far as adding angular momentum to the planet, I've got no idea. Wrap superconducting coils around the planet and spin up using a drive current and the sun's magnetic field? You'd need to strip-mine a few NVOs to get the materials, of course...

Anyway, this seems like a reasonable engineering project, given a suitable timescale (200,000 years) and budget for getting it going (a significant proportion of Earth's Gross Planetary Product).
Research Scientist (Sensors), Sharp Laboratories of Europe, UK

Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #11 on: 09/16/2011 02:45 PM »
I read somewhere that within the upper atmosphere of Venus there is a fairly stable temperature band that is habitable.  I think the first Venusian colonists will be living in buoyant constructs within that zone.  On a much, much longer scale, perhaps extreme genetic manipulation, tremendous-scale removal of atmospheric gases, or both, or some other distant solution will allow us to live at Venus surface conditions, but I don't see sunshades as the enabler, and don't predict to witness a humans on Venus mission during my lifetime (or my grandkids).         
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Offline baldusi

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Re: Sun Shade concepts for Venus
« Reply #12 on: 09/16/2011 03:33 PM »
Wouldn't an angled impact of asteroids along the equator transmit some rotational momentum? It would also heat more than the hell that already is. I've heard someone saying that Venus lacks tectonics because it's greenhouse effect kept the surface to hot, that it actually acted as a heat pipe of the internal temperature to the surface, and thus radiated it much faster.
If that is so, is the interior of Venus solid? If it were still liquid, and you assume that some heat would still be crated by the radioactive decay of heavy elements in the core, and you could sort of lower the temperature of the surface rapidly while imparting rotational momentum (i.e. asteroid bombardment), couldn't you start some dynamo effect, with the core almost not rotating and the surface doing it?

Offline Hop_David

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Re: Sun Shade concepts for Venus
« Reply #13 on: 09/16/2011 03:43 PM »
I read somewhere that within the upper atmosphere of Venus there is a fairly stable temperature band that is habitable.     

Geoffrey Landis has written several papers on this as well as a few science fiction stories.

While comfortable temperatures and pressures exist at certain Venusian altitudes, the air is toxic and corrosive. Colonists in floating cloud cities would not have access to the surface. Therefore no metal mines for the Venusian civilization.

Earth-Venusian synodic period is very close to 8/5 years. Period of an earth-Venus Hohmann orbit is very close to 4/5 years. This makes a very nice cycler system possible. The cyclers earth fly by points would form a giant pentagram. This Venus cycler system is far more elegant than the proposed Mars Cycler schemes (Aldrin's and Niehoff's).

Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #14 on: 09/16/2011 04:27 PM »
Geoffrey Landis has written several papers on this as well as a few science fiction stories.
Thanks for that!

While comfortable temperatures and pressures exist at certain Venusian altitudes, the air is toxic and corrosive. Colonists in floating cloud cities would not have access to the surface. Therefore no metal mines for the Venusian civilization.

Stainless steel robotic/teleoperated blimp/submarines could have access to the surface. 

A series of these could even be lined up at different altitudes, designed with different buoyancy ranges, with cables going from one to the next (passing metals/ores up from one to the next sky-crane until they are at the floating colony)  They don't even need to be attached to eachother.  Just lower the hook down to the overweighted one below (which pulls the stations toward eachother until their offsetting buoyancies allow a break in contact and the load reels up to the next blimp station up.

Eventually might even have refridgeration ships to keep people cool inside using floating,buoyant broadcast powerstations which use atmospheric phenomena as an energy source.  The future is LARGE!
« Last Edit: 09/16/2011 04:29 PM by go4mars »
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #15 on: 09/16/2011 04:48 PM »
peter-b has got it about right. The resources and techniques needed to alter Venus to make it habitable would tax the most advanced spacefaring civilization, never mind little old 21st Century Earth.

This thread is an interesting theoretical discussion but I don't think such a thing will ever be attempted, even in the far future, not even when the means to do it exist. There is no reason to do so. You don't have to terraform any planet to support a large human population in space: O'Neill style habitats would be many orders of magnitude cheaper and can have the environment tailored to the needs of the population.
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Offline AlexCam

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Re: Sun Shade concepts for Venus
« Reply #16 on: 09/16/2011 06:20 PM »
peter-b has got it about right. The resources and techniques needed to alter Venus to make it habitable would tax the most advanced spacefaring civilization, never mind little old 21st Century Earth.

This thread is an interesting theoretical discussion but I don't think such a thing will ever be attempted, even in the far future, not even when the means to do it exist. There is no reason to do so. You don't have to terraform any planet to support a large human population in space: O'Neill style habitats would be many orders of magnitude cheaper and can have the environment tailored to the needs of the population.

I doubt you can support millions or billions of people in space in the future. Just too complicated. In contrast, Venus is basically Earth's twin sister planet and creative concepts can help with it becoming a more Earth like habitat.

At the end it is the sun shade that makes or breaks the concept of colonizing Venus. As it was said above, if you cool Venus through a sun shade over several decade (according to some estimates over 200 years), CO2 will freeze out of the atmosphere. That leaves a mostly nitrogen atmosphere with just about 3 bar. Something that allows humans to operate on the surface without protective suits, just oxygen masks. The sun shade could simulate a 24 hour daylight-night cycle.

That leaves us with how we can create a sun-shade without breaking the bank. A sun shade in space will likely break the bank. What I had in mind is something like "intelligent aerosols" in the Venusian atmosphere that are self-replicating and shade the planet. Aerosols that can stay in the upper atmosphere for the long-term and can be manipulated to either let light through or block it. That doesn't break the bank, if it could be done, it wouldn't cost more than any other current unmanned spaceflight mission. Of course we would need to wait quite a while for the temperatures to fall, but hey, it would be worth it!

Offline aquanaut99

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Re: Sun Shade concepts for Venus
« Reply #17 on: 09/16/2011 06:27 PM »
Terraforming Venus would be a challenge even for an ultra-advanced civilization. It would also be a waste of time and resources, since enven an Earth-like terraformed Venus would become uninhabitable due to solar brightening long before Earth itself.

Mars is a far better choice. And in the very long term, Titan is probably the place we should go to if we have to stay in our Solar System; it will be nice and cozy (smack in the middle of the habitable zone) when our Sun turns into a red giant...

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #18 on: 09/16/2011 08:48 PM »
When I fired this sunshade idea at Adam Crowl his maths suggested the atmosphere taking between 2 and 90 years to freeze out with a geometric mean of ~13 years. Not a very long wait for that much real estate.

A sunshade at the Venus-Sun L1 point would need to have an area of around 500 million km^2 to shade the whole planet, made from solar sail cloth at 10g/m^2 it would mass 5 billion tonnes, a huge mass compared to what we put into space now, not that much compared to what we move around on the surface of the Earth each year, so for a space based civilization I don't think such a sunshade would "break the bank"

Dry Ice has a density of 1.6g/cc, at the moment there's CO2 the equivalent of 650 meters of dry ice over the entire surface of Venus, how thick can you make an ice sheet? Well the average thickness of the Antarctic ice is 2,000 m, and the greatest measured thickness is more than 4,750 m, if we could get the average thickness of a Venusian CO2 ice sheet up to 6.5km it would cover 10% of the planet, leaving nearly 400 million km^2 uncovered.

My not great maths suggests that the momentum of the mass of the comets necessary to provide Venus with shallow seas would not be enough to change the rate of rotation by more than around 10 m/s, so you could maybe change it so only one face is towards the Sun, if there's any advantage in that, but not change it by enough to get anything like a 24 hour day.

Last I heard the theory is that Venus does not have plate tectonics, it's surface undergoes periodic reforming through massive volcanic events - a bit like as in the John Cusack movie "2012" - this could be a problem for terraforming that planet.
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Offline KelvinZero

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Re: Sun Shade concepts for Venus
« Reply #19 on: 09/16/2011 10:14 PM »
I doubt you can support millions or billions of people in space in the future. Just too complicated. In contrast, Venus is basically Earth's twin sister planet and creative concepts can help with it becoming a more Earth like habitat.

At the end it is the sun shade that makes or breaks the concept of colonizing Venus. As it was said above, if you cool Venus through a sun shade over several decade (according to some estimates over 200 years), CO2 will freeze out of the atmosphere. That leaves a mostly nitrogen atmosphere with just about 3 bar. Something that allows humans to operate on the surface without protective suits, just oxygen masks. The sun shade could simulate a 24 hour daylight-night cycle.

That leaves us with how we can create a sun-shade without breaking the bank. A sun shade in space will likely break the bank. What I had in mind is something like "intelligent aerosols" in the Venusian atmosphere that are self-replicating and shade the planet. Aerosols that can stay in the upper atmosphere for the long-term and can be manipulated to either let light through or block it. That doesn't break the bank, if it could be done, it wouldn't cost more than any other current unmanned spaceflight mission. Of course we would need to wait quite a while for the temperatures to fall, but hey, it would be worth it!
There is very little hydrogen on venus which makes engineering an earth lifeform for it problematic.
My favorite scheme is self replicating little reflective solar sails that have very basic 'flocking' ability. With something like that you could regulate the light to any part of the planet, even fake a 24 hour day with sunrise and sunset.

When people say it will cost trillions, it really is undefined. Until we have self replicating somethings that can thrive in other environments than earth we really have no hope. Once we do the cost is somewhere between zero and "oops they just ate jupiter".

I personally think we will one day learn to live within the small icy bodies of the solar system and forget why we ever thought the ability to stand on the 25% of earth which is not ocean was so important to us.

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #20 on: 09/16/2011 11:07 PM »

I doubt you can support millions or billions of people in space in the future. Just too complicated. In contrast, Venus is basically Earth's twin sister planet and creative concepts can help with it becoming a more Earth like habitat.

At the end it is the sun shade that makes or breaks the concept of colonizing Venus. As it was said above, if you cool Venus through a sun shade over several decade (according to some estimates over 200 years), CO2 will freeze out of the atmosphere.

Venus is emphatically not Earth's twin. Apart from size it is different in almost every other way. How does cooling it to the temperature of the Martian poles to freeze out the CO2 make it a "more Earth like habitat?"

I find it astonishing that you would call building space habitats "too complicated" compared with the sheer size of the enterprise you are proposing. There is no guarantee whatsoever that Venus can be made remotely Earthlike. Look at the other criticisms in this thread of the idea. There is no reason ever to do it, even if it were possible, which I doubt.



« Last Edit: 09/16/2011 11:09 PM by douglas100 »
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #21 on: 09/16/2011 11:13 PM »

I personally think we will one day learn to live within the small icy bodies of the solar system and forget why we ever thought the ability to stand on the 25% of earth which is not ocean was so important to us.

I think that is far more likely than Venus ever being made habitable.
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Offline colbourne

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Re: Sun Shade concepts for Venus
« Reply #22 on: 09/17/2011 04:54 AM »
Ignoring the ethics of such an act. I would propose a biological terraforming of Venus.
A small seed colony of biological agent could be sent to Venus which will convert the atmosphere to an  inert solid that would sink to the surface thus reducing the planets green house effect.

Offline Nathan

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Re: Sun Shade concepts for Venus
« Reply #23 on: 09/17/2011 05:30 AM »
Venus has the annoying habit of Resurfacing itself every half billion years or so. The place Is designed to sizzle.
« Last Edit: 09/17/2011 05:31 AM by Nathan »
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline AlexCam

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Re: Sun Shade concepts for Venus
« Reply #24 on: 09/17/2011 07:41 AM »

I doubt you can support millions or billions of people in space in the future. Just too complicated. In contrast, Venus is basically Earth's twin sister planet and creative concepts can help with it becoming a more Earth like habitat.

At the end it is the sun shade that makes or breaks the concept of colonizing Venus. As it was said above, if you cool Venus through a sun shade over several decade (according to some estimates over 200 years), CO2 will freeze out of the atmosphere.

Venus is emphatically not Earth's twin. Apart from size it is different in almost every other way. How does cooling it to the temperature of the Martian poles to freeze out the CO2 make it a "more Earth like habitat?"

I find it astonishing that you would call building space habitats "too complicated" compared with the sheer size of the enterprise you are proposing. There is no guarantee whatsoever that Venus can be made remotely Earthlike. Look at the other criticisms in this thread of the idea. There is no reason ever to do it, even if it were possible, which I doubt.

Most of what have been brought up in this thread as showstoppers is either undefined or incorrect. Some say it is too costly, without specifying why. Some say heavy volcanic activity is a problem without specifying the time frame of this activity (every few hundred thousand years, isn't a problem). Some talk about the lack of a magnetic field, failing to say why that would be a problem. Some talk about the lack of hydrogen or water, failing to say that there is enough of both to support a large human colony for thousands of years, although there is not enough to support oceans or lakes. Etc.

An interesting articles detailing the challenges and concepts required is e.g. laid out here http://www.paulbirch.net/TerraformingVenusQuickly.pdf

To sum up, if it were possible to inject self-replicating sun-shading particles in the upper atmosphere of Venus that cool the planet in the time frame (a few dozen years) people have suggested for all the CO2 to fall as snow, Venus would be by far the most benign environment for humans in the solar system outside Earth.

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #25 on: 09/17/2011 11:34 AM »

 Some say it is too costly, without specifying why. 

Some say it is affordable without specifying why.

Birch's paper is interesting. (I wish the BIS would put back issues of JBIS online, but that's another issue.) But the environment he ends up with still needs managing on a huge scale to keep it habitable.

The thing we have learned from exploration of the Solar System is how little we understand about planetary environments. There are too many unknowns to predict the outcome of modifying a planet like this.

You didn't reply to my point about about space habitats, the one that you dismissed as "too complicated." (Compared with terraforming a planet-are you serious?) The reason I raised the point is because the real showstopper for this proposal in reality is: why do it at all?
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Offline gospacex

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Re: Sun Shade concepts for Venus
« Reply #26 on: 09/17/2011 01:05 PM »
When I fired this sunshade idea at Adam Crowl his maths suggested the atmosphere taking between 2 and 90 years to freeze out with a geometric mean of ~13 years. Not a very long wait for that much real estate.

Something is seriously off with that math.

Icelandic lava flows about 20 meters thick took decades to cool down. Icelanders were even using them to generate electricity.

Venusian atmosphere is equivalent to a kilometer-thick layer of water by mass. I have hard time imagining that cooling down from hundreds of degrees Celsuis to -78 C in 13 years, much less in 2 years.

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Re: Sun Shade concepts for Venus
« Reply #27 on: 09/17/2011 02:14 PM »
Most of what have been brought up in this thread as showstoppers is either undefined or incorrect. Some say it is too costly, without specifying why.

You're saying it's not too costly?  Call me Buzz Killington, if you will.   
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Re: Sun Shade concepts for Venus
« Reply #28 on: 09/17/2011 02:22 PM »
When I fired this sunshade idea at Adam Crowl his maths suggested the atmosphere taking between 2 and 90 years to freeze out with a geometric mean of ~13 years. Not a very long wait for that much real estate.

Something is seriously off with that math.

Icelandic lava flows about 20 meters thick took decades to cool down. Icelanders were even using them to generate electricity.

Venusian atmosphere is equivalent to a kilometer-thick layer of water by mass. I have hard time imagining that cooling down from hundreds of degrees Celsuis to -78 C in 13 years, much less in 2 years.
Especially since all the heat needs to be radiated. No melting snow, wind or water to cool things down.

Offline aero

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Re: Sun Shade concepts for Venus
« Reply #29 on: 09/17/2011 04:20 PM »
No one has mentioned that the interior of Venus is very hot. It is a huge, (81.5% of Earth's mass) very hot rock with high internal temperatures. It may or may not have a liquid core but the rock is big enough and hot enough that heat inertia (if that is a concept) will keep the atmosphere gaseous for a very long time.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #30 on: 09/17/2011 05:11 PM »
When I fired this sunshade idea at Adam Crowl his maths suggested the atmosphere taking between 2 and 90 years to freeze out with a geometric mean of ~13 years. Not a very long wait for that much real estate.

Something is seriously off with that math.

Icelandic lava flows about 20 meters thick took decades to cool down. Icelanders were even using them to generate electricity.

Venusian atmosphere is equivalent to a kilometer-thick layer of water by mass. I have hard time imagining that cooling down from hundreds of degrees Celsuis to -78 C in 13 years, much less in 2 years.

Rock and soil are pretty good thermal insulators, air is not.

On Earth the lower atmosphere will cool by something like one degree C an hour through the night, on Venus we have 100 times the atmosphere and want to cool it by ~600C, so if we lose 0.01C/hr it would take 60000 hours - about 7 years, and because it's starting from a higher initial temperature the initial rate of heat loss would be pretty high.

No one has mentioned that the interior of Venus is very hot. It is a huge, (81.5% of Earth's mass) very hot rock with high internal temperatures. It may or may not have a liquid core but the rock is big enough and hot enough that heat inertia (if that is a concept) will keep the atmosphere gaseous for a very long time.

As I said above, rock is a pretty good insulator (you can walk bare foot over lava that's still at hundreds of degrees just a few inches inside, it would only be the upper most few meters of the crust that would feed heat to the atmosphere at a significant rate. Your hot crust point is relevant though to any CO2 icecap, as such an icecap would also be a good insulator.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #31 on: 09/17/2011 08:30 PM »
The discussion I had with Adam is here:
http://crowlspace.com/?page_id=170

My own BOE maths suggests that it'd take at least a century and a half for Venus to lose enough heat (working on the current heat loss rate of ~150W/m^2 (the disk receives about 2.5kw/m^2, high albedo means it absorbs only about 25%, and that's what it loses since it's in thermal equilibrium, and surface area is 4 times the size of the disc) common sense would suggest the the current rate of heat lose would fall as the planet cooled, but I could see how vertical movement of air could be enhanced, thus bringing more warm air to TOA and actually accelerating the rate of heat loss.
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Online savuporo

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Re: Sun Shade concepts for Venus
« Reply #32 on: 09/18/2011 04:57 AM »
You didn't reply to my point about about space habitats, the one that you dismissed as "too complicated." (Compared with terraforming a planet-are you serious?) The reason I raised the point is because the real showstopper for this proposal in reality is: why do it at all?
I think you are missing a basic trait of humans here. Regardless of if its sensible, expensive, realistic or anything else, once the capability exists, it WILL be tried.
Yes, most may choose to stay in space based habitats, but everything else will most likely be tried in some shape or form as well. There will be people insisting on trying to make Mercury livable.
Quite as some people insist on living in Rovaniemi, Finland.

In other words, IMO O'Neill habitats and Mars colonization are off topic for this thread.

Also i do not think manufacturing atmospheric sunshades for the entire planet is too far fetched, with partially self-replicating macroscale machinery, which is real technology even now.
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Offline aquanaut99

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Re: Sun Shade concepts for Venus
« Reply #33 on: 09/18/2011 06:05 AM »
You didn't reply to my point about about space habitats, the one that you dismissed as "too complicated." (Compared with terraforming a planet-are you serious?) The reason I raised the point is because the real showstopper for this proposal in reality is: why do it at all?
I think you are missing a basic trait of humans here. Regardless of if its sensible, expensive, realistic or anything else, once the capability exists, it WILL be tried.

No. Bad argument. I predict that if humanity survives this century, that trait will die. There is such a thing as a precautionary principle, you know. One should not do everything that one could. That's why we didn't nuke ourselves to kingdom come during the Cold War (we flew to the moon instead).

Quote
Quite as some people insist on living in Rovaniemi, Finland.

So? That's a nice enough place to live (all you need is some warm clothing for winter). Venus is not.

« Last Edit: 09/18/2011 06:05 AM by aquanaut99 »

Offline cro-magnon gramps

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Re: Sun Shade concepts for Venus
« Reply #34 on: 09/18/2011 08:02 AM »

Anyway, this seems like a reasonable engineering project, given a suitable timescale (200,000 years) and budget for getting it going (a significant proportion of Earth's Gross Planetary Product).

what of the SGPSP of 2200 ;) or Sol's Gross Planetary System Product; ok, we are talking Sci-Fi, but so is Terra Forming a planet; (bwt it is 3:48am so a good time to think of such things ;)
   Technical problems aside, there is nothing wrong in the concept, other than the moral one, if there is life forms on Venus; it is probably not going to be known for a few years, but if a CO2 based life form exists in Venus' atmosphere, then you may have a problem;
    but even putting that aside, it would take the resources  of a Class 1 at 1.10 % to even begin to work on something this big; perhaps it is appropriate that as a Class 0 society at 0.7 % we are even thinking it;
     good luck with your ideas;

Gramps

ps remember discussing this in the late 60's early 70's, with a bunch of Marxist Lenist University Students, over a carafe of red wine and pizza, while others played pong at another table with the screen built into the table ;-) now project your selves 40 years, to 2050 and think about this again!!?? imagine how technology and society will have changed LOL perhaps it doesn't sound so outrageous ;)
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Offline AlexCam

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Re: Sun Shade concepts for Venus
« Reply #35 on: 09/18/2011 08:15 AM »
Most of what have been brought up in this thread as showstoppers is either undefined or incorrect. Some say it is too costly, without specifying why.

You're saying it's not too costly?  Call me Buzz Killington, if you will.   

If we were able to create macroscopic robotic elements or biological elements that can be self-replicating and contain little sun-shades, that can be seeded in the upper atmosphere of Venus, then the actual costs of flying a mission there to start the sun shading will cost about as much as Venus Express. There is no need to do anything except deploy the first initial elements and let them take it from there.

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Re: Sun Shade concepts for Venus
« Reply #36 on: 09/18/2011 07:47 PM »
I think you are missing a basic trait of humans here. Regardless of if its sensible, expensive, realistic or anything else, once the capability exists, it WILL be tried.

No. Bad argument. I predict that if humanity survives this century, that trait will die.

The last sentence is an oxymoron. I'll let you figure out why.


Quote
Quote
Quite as some people insist on living in Rovaniemi, Finland.

So? That's a nice enough place to live (all you need is some warm clothing for winter). Venus is not.
One man's hell is another man's paradise, yes.

Enough with off topic though.
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Online savuporo

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Re: Sun Shade concepts for Venus
« Reply #37 on: 09/18/2011 07:55 PM »
If we were able to create macroscopic robotic elements or biological elements that can be self-replicating and contain little sun-shades, that can be seeded in the upper atmosphere of Venus, then the actual costs of flying a mission there to start the sun shading will cost about as much as Venus Express. There is no need to do anything except deploy the first initial elements and let them take it from there.

The problem here is that fully self replicating machinery may be very far off, but partial self-replication is achievable even now, see RepRap

Fabricating things like ICs currently just require a ton of infrastructure, and there are no good substitutes for something as simple as an 8-bit MCU that could easily be fabbed, although there are some avenues of research going on there.

Fortunately the hard to fab parts are relatively lightweight by mass, which would reduce the shipped mass requirements for terraforming scale projects from totally insane to moderately bonkers.
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Offline AlexCam

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Re: Sun Shade concepts for Venus
« Reply #38 on: 09/19/2011 05:08 PM »
If we were able to create macroscopic robotic elements or biological elements that can be self-replicating and contain little sun-shades, that can be seeded in the upper atmosphere of Venus, then the actual costs of flying a mission there to start the sun shading will cost about as much as Venus Express. There is no need to do anything except deploy the first initial elements and let them take it from there.

The problem here is that fully self replicating machinery may be very far off, but partial self-replication is achievable even now, see RepRap

Fabricating things like ICs currently just require a ton of infrastructure, and there are no good substitutes for something as simple as an 8-bit MCU that could easily be fabbed, although there are some avenues of research going on there.

Fortunately the hard to fab parts are relatively lightweight by mass, which would reduce the shipped mass requirements for terraforming scale projects from totally insane to moderately bonkers.

Organic material can self replicate. There have been suggestions of seeding genetically modified algae into the Venusian atmosphere.

Online savuporo

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Re: Sun Shade concepts for Venus
« Reply #39 on: 09/19/2011 05:53 PM »
Organic material can self replicate.
Yes, i have experienced it :)
Quote
There have been suggestions of seeding genetically modified algae into the Venusian atmosphere.
Sure, and it would be fantastic if this could be worked out. Im somewhat skeptical that our genetic engineering is advanced enough or has well understood long term effects and is controllable enough to attempt something like that.
Seeing the rapid developments in the field this may well be a viable option once the question of terraforming becomes relevant.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #40 on: 09/19/2011 11:18 PM »
Quote
There have been suggestions of seeding genetically modified algae into the Venusian atmosphere.

Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue.
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Offline Solman

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Re: Sun Shade concepts for Venus
« Reply #41 on: 09/21/2011 02:27 PM »
Quote
There have been suggestions of seeding genetically modified algae into the Venusian atmosphere.

Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue.

 If however there were balloon-borne ribbons of water absorbent material filling the sky there would at least be some green to the vista.
For a completely biological approach you could imagine lichen-like life forms with large hydrogen filled balloon-like structures floating in the sulphuric acid clouds excreting sulphur as they break the acid down into water. Or maybe not.
 I had the idea years ago of solar powered factories hung from acid derived hydrogen balloons floating high in the atmosphere that would break the CO2 down and form oxygen filled diamond bubbles or balloons with velcro like surfaces. The factories would drop them into the lower atmosphere where they would loosely stick together to form islands then continent sized islands and finally perhaps cover virtually the whole lower atmosphere. The atmosphere is gradually thinned and eventually the islands come to rest on the surface. The atmosphere would be sequestered. I know its half-baked but I hope amusing anyway.


     

Offline AlexCam

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Re: Sun Shade concepts for Venus
« Reply #42 on: 12/18/2011 01:50 PM »
Quote
There have been suggestions of seeding genetically modified algae into the Venusian atmosphere.

Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue.

Earth's atmosphere is not comparable to the atmosphere of Venus.

Offline Lampyridae

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Re: Sun Shade concepts for Venus
« Reply #43 on: 12/19/2011 07:19 AM »
I presented a paper on this back in my Hons year. The big thing that's missing is the fact that carbon dioxide is baked out of rock, and can be locked back into it. Venus' CO2 atmosphere came from a gradual period of calcination as it was cooked out of carbonate rocks. Reduce the temperature, and the metal oxides combine with CO2 to form carbonate rocks. Water would help this a lot.

The removal of CO2 from the atmo combined with falling temperatures results in a lot of rock fracturing. A lot depends on the porosity or potential porosity of the Venusian rock, which I really know nothing about.

It would take a while, but the unloading of 1km worth of CO2 would also create plenty of rock fracturing, not to mention cooling down even a few dozen degrees K - this a planet that knows hardly any temperature differentials. At night, CO2 ice would collect at the highest mountains, Ishtar Terra for example. Colonisation might actually be possible in the valleys, rather, with the CO2 plateaus reducing a lot of the planet's albedo (but some kind of sunshade would still be necessary).

On the topic of sunshades, a simple cloud of asteroidal dust at L2 would do the job, sepherded with light pressure from nearby solar mirrors.
« Last Edit: 12/19/2011 07:46 AM by Lampyridae »
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Offline ApolloStarbuck

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Re: Sun Shade concepts for Venus
« Reply #44 on: 12/30/2011 09:38 AM »
Organic material can self replicate. There have been suggestions of seeding genetically modified algae into the Venusian atmosphere.

This Idea was often pushed by Carl Sagan.  IIRC he later backed off the concept.
The original idea was that genetically algae would be seeded in the upper atmosphere and consume the carbon dioxide, reproduce and continue until the gas was absorbed enough to cause a reverse runaway greenhouse effect.
He later stated that it probably wouldn't work because as the algae sank into the lower levels of the atmosphere, it would simply "burn up" and release the carbon it had absorbed in the first place. Plus, there's no appreciable amounts of hydrogen that the algae would need.

But if you want to think REALLY big, how about just swapping Venus and Mars orbits.  Venus, pushed out to Mars' orbit, would get a chance to cool down and still be in the  habitability zone and Mars, being moved closer to the Sun, would heat up and get a thicker atmosphere...for a little while at least  ;)
« Last Edit: 12/30/2011 09:49 AM by ApolloStarbuck »
...weren't we supposed to be on Mars by now?

Offline Bob Shaw

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Re: Sun Shade concepts for Venus
« Reply #45 on: 01/03/2012 02:13 AM »
The idea of simply freezing out the atmosphere of Venus isn't an adequate fix for the excess mass of the atmosphere. It has to be persuaded to go somewhere else, or else you're permanently on a knife-edge, waiting for the stuff to return to a gaseous state and ruin all your hard work.

The answer is to heat Venus up, and break the feedback systems which govern the current atmosphere. We need to puff as much as possible of the atmosphere up, so that it reaches a height where the Sun can erode it away into interplanetary space. In effect, the situation at Mars is applied to Venus (thin, high atmosphere), and as both planets lack serious magnetic fields we may expect the process to be quite effective.

How to heat the atmosphere? Well, an albedo change would help, plus input from mirrors. The sort of mirrors that might be used could be either reflective, or Fresnel lenses. In either case you might use mirrors which are not actually in orbit, but which use the pressure of sunlight to hang in space. The sheer size of the required mirror technology suggests that it might well be a spinoff from interstellar propulsion systems, which in turns invites the use of the sort of intra-Mercurian laser cannon which are often posited for 'stay-at-home' starship propulsion devices, but repurposed to heat up Venus instead. Another option would be to move to the realm of masers to heat the upper reaches of the atmosphere (natural CO2 maser activity in the atmosphere of Mars was proposed decades ago). Ideally, of course, we use the Sun to do the job of both heating and erosion.

Once you have eroded the atmosphere your cooling job becomes much simpler, and as previously stated a nice little dust cloud factory at the inner LaGrange point would be a fairly cheap start.

Overall, though, the sort of resources and technology which are required to cool Venus are on a par with those required for interstellar flight.

Offline Danderman

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Re: Sun Shade concepts for Venus
« Reply #46 on: 01/03/2012 02:16 AM »
This is a little o/t, but I suspect that the actual solution to cooling Venus will involve moving some of its atmosphere, bit by bit, to Mars. Both planets would benefit from such an exchange. How that would happen is beyond me.


Offline kch

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Re: Sun Shade concepts for Venus
« Reply #47 on: 01/03/2012 03:40 AM »
This is a little o/t, but I suspect that the actual solution to cooling Venus will involve moving some of its atmosphere, bit by bit, to Mars. Both planets would benefit from such an exchange. How that would happen is beyond me.



Maybe something like this?



;)

Offline Danderman

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Re: Sun Shade concepts for Venus
« Reply #48 on: 01/03/2012 03:53 AM »
You have solved the problem.

Offline sojourner

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Re: Sun Shade concepts for Venus
« Reply #49 on: 01/03/2012 04:13 AM »
OK, this has always been a crazy idea of mine, and I know the science of it is really bad, but why not recreate the impact that gave Earth it's moon on Venus?  A food portion of the over abundant atmosphere is blown away, angular momentum is created,  the entire planet of Venus is basically "rebooted".  We just need to find a good Mars sized planet that no one is using....

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Re: Sun Shade concepts for Venus
« Reply #50 on: 01/03/2012 04:18 AM »
F = ma.

Mars' mass is 10^23 kg. To accelerate something the size of Mars at 1 m/s^2, you need 10^23 N of force. The space shuttle main engines produced 10^6 N of force.
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #51 on: 01/03/2012 04:54 AM »
Have a device float on the upper atmosphere, bring in the CO2, convert it to C and O2, release O2, take carbon to high orbit to make an artificial satellite of carbon.

Harvest some of the CO2 to make CO and O2 for fuel to take O2 ( from some of the CO2 to make C and O2, carbon left in Venus high orbit as above ) to Mars by use of a reusable orbital transfer vehicle.

Craft to scoop up CO2 ( Venus top atmosphere to low Venus orbit )powered by CO/O2.

Station in low orbit takes the CO2 to make CO, O2, C from solar power. If manned then habitat part of station rotates to make 1G for crew.

Crazy, but can that be built on to make something practical.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #52 on: 01/03/2012 05:43 AM »
There's around 460 million billion tonnes of CO2 in the Venusian atmosphere.
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Offline strangequark

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Re: Sun Shade concepts for Venus
« Reply #53 on: 01/03/2012 05:52 AM »
Have a device float on the upper atmosphere, bring in the CO2, convert it to C and O2, release O2, take carbon to high orbit to make an artificial satellite of carbon.
It would require roughly 1 billion times the total energy currently produced by the world in one year. Yes, I did the math. As far as using solar power, if you wished to accomplish it within 1000 years, using a 100% efficient solar array, with 100% efficient conversion to chemical energy stationed in Venus orbit, the required surface area is a bit more than the entire surface area of Earth.

As for the rest of the plan, everything else requires only slightly less ridiculous amounts of energy/power.

Any civilization capable of accomplishing this would have better way, like fusing the carbon and oxygen into metals...or magic.

Harvest some of the CO2 to make CO and O2 for fuel to take O2 ( from some of the CO2 to make C and O2, carbon left in Venus high orbit as above ) to Mars by use of a reusable orbital transfer vehicle.

Craft to scoop up CO2 ( Venus top atmosphere to low Venus orbit )powered by CO/O2.

Station in low orbit takes the CO2 to make CO, O2, C from solar power. If manned then habitat part of station rotates to make 1G for crew.
« Last Edit: 01/03/2012 05:56 AM by strangequark »
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Offline colbourne

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Re: Sun Shade concepts for Venus
« Reply #54 on: 01/03/2012 09:31 AM »
To do this cheaply the answer would have to be biological so that only a few small rockets are needed. They would carry some form of life that can convert the CO2 to  an inert solid able to survive on the surface.

Moving large objects on to a collision course with low energy usage demands the luck of finding a suitable asteroid on very nearly the correct orbit to eventually collide. A very small nudge is all that is then required.

Offline alexterrell

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Re: Sun Shade concepts for Venus
« Reply #55 on: 01/04/2012 04:29 PM »
Zubrin had a proposal to fire MgO and CaO from Mercury to Venus. These react with CO2 to form solid carbonates, thereby precipitating out the atmosphere.

Yes - it's far off. It would require a solar powered mining device and linear accelerator, which can (now for the tricky part) replicate itself like a Von Neumann machine. 


Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #56 on: 01/04/2012 06:58 PM »
Zubrin had a proposal to fire MgO and CaO from Mercury to Venus. These react with CO2 to form solid carbonates, thereby precipitating out the atmosphere.

Yes - it's far off. It would require a solar powered mining device and linear accelerator, which can (now for the tricky part) replicate itself like a Von Neumann machine. 
As long as you promise to leave enough carbon for a nice Venusian diamond ring.  ;)

The refractive index of diamond means you could build a big honker, (or a bunch of smaller ones in geosync) orbiting Venus along the ecliptic, to divert a lot of sunlight around the whole planet.

Again. Von Neumann seems to have the most likely approach...
« Last Edit: 01/04/2012 07:02 PM by go4mars »
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #57 on: 01/26/2012 09:33 PM »
Venus atmosphere
source
http://en.wikipedia.org/wiki/Atmosphere_of_Venus

Height km      Temp. C          pressure in bar
0                    462                92.10 ( similar to 910 meters below the surface of the Ocean )
50                  75                  1.066 ( near Earth sea level )
100                -112                0.0000266

Clouds in Earth's atmosphere are said to have living bacteria in them. It is said that there could be bacteria in clouds in Venus's atmosphere. So there should be future probes to study Venus before it might be terraformed.

Most of the thermal energy is below  50km and and air volume. Sources of thermal energy are from the Sun and inside of Venus. Solar sails placed in Venus GSO and using Sun light to move them around as needed would block some of the incoming solar enery. Solar sails places farther away could partly or fully eclipse Venus from the Sun. This would help to cool the planet.

Once that is in place, machines would need to be sent to the surface.They would change the CO2 into solids that would be stable in the hight pressure and temperature at the surface and still be stable at low pressure and tempertures when the planet atmosphere is changed to more Earth like. Other compounds would need to be changed also. Reducing the pressure and changing the quantities of compounds in the air would help lower the atmospheric tempature. So the machines change the compounds in the air to solids to get rid of the excess mass in the atmosphere.

Also causing the lower air to mix with the upper air can help in bleeding off some of the heat to space on the night side of the planet. Winds on Venus can be used to our advantage if some or all of the solar energy is blocked on the day light side of Venus.

The machines will need power. They might be able to use the heat from the surrounding air as a source of energy at first. Later on as the temp and pressure goes down solar or nuclear power might be a source of energy.

Any way we look at this it is a big project. Most likely not to take place any time before 2050. We will need in space infrastructure such as space stations and lunar manufacturing. Plus quick cargo and crew transport ships between planets ( one way less than 21 days from Earth to Mars or Venus ), possibly powered by some sort of fussion powered engine.

By 2050 we should have solar sails by then and single or two stage low cost reusable launch vehicles and a moon base. So the price to terraform Venus will go down as our in space infrastructure goes up.
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #58 on: 01/30/2012 12:32 PM »
A lot of the ideas for sun shades seem to be away to expensive to adopt. I think it can be done with far fewer space platforms with out the need of solid shades.

The use of lasers could be the answer. A laser light in space can shine on to infinity. Small solar powered laser platforms positioned in space slowly rotated and releasing a some sort of plasma gas (fog) this would form a thin disc many miles in diameter, a coloured Laser would be then switched on forming a sheet of light ( Similar to those seen at rock concert displays through dry ice) this would illuminate the discs of plasma. Having several layers of various coloured lasers would darken the colour of  the disc thus blocking a percentage of light from the Sun. Putting the platforms one in front of the other would further darken the effect. Solar wind would eventually blow away the plasma, so the platforms would need replenished from time to time or just replaced.

The area covered with just a hand full of platforms would be vast. Not needing any new out of reach technology, and relatively small low powered cheap lasers.
« Last Edit: 02/01/2012 09:20 PM by Da5id »

Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #59 on: 01/30/2012 12:49 PM »
The use of lasers could be the answer. A laser light in space can shine on to infinity. Small solar powered laser platforms positioned in space slowly rotated and releasing a some sort of plasma gas (fog) this would form a thin disc many miles in diameter, a coloured Laser would be then switched on forming a sheet of light ( Similar to those seen at rock concert displays through dry ice) this would illuminate the disc of plasma. Having several layers of various coloured lasers would darken the colour of  the disc thus blocking a percentage of light from the Sun. Putting the platforms one in front of the other would further darken the effect. Solar wind would eventually blow away the plasma, so the platforms would need replenished from time to time or just replaced.

The area covered with just a hand full of platforms would be vast. Not needing any new out of reach technology, and relatively small low powered cheap lasers.
Although I generally am in favour of anything related to lasers, because they are cool, I'm not sure I followed you there.  For example, how does a laser release fog?  You want a fog in space to block some of the sunlight? 
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #60 on: 01/30/2012 01:03 PM »
The use of lasers could be the answer. A laser light in space can shine on to infinity. Small solar powered laser platforms positioned in space slowly rotated and releasing a some sort of plasma gas (fog) this would form a thin disc many miles in diameter, a coloured Laser would be then switched on forming a sheet of light ( Similar to those seen at rock concert displays through dry ice) this would illuminate the disc of plasma. Having several layers of various coloured lasers would darken the colour of  the disc thus blocking a percentage of light from the Sun. Putting the platforms one in front of the other would further darken the effect. Solar wind would eventually blow away the plasma, so the platforms would need replenished from time to time or just replaced.

The area covered with just a hand full of platforms would be vast. Not needing any new out of reach technology, and relatively small low powered cheap lasers.
Although I generally am in favour of anything related to lasers, because they are cool, I'm not sure I followed you there.  For example, how does a laser release fog?  You want a fog in space to block some of the sunlight? 
The fog plasma or some sort of gas to create a cloud substance would be slowly released from tanks  at a slow rate carried on the platform. example in displays they have a dry ice machines  and a  laser shines (slices) through this.
A laser would not be seen in space unless you view it straight on, you need a substance with which to illuminate.
Layers of various colour  seen from the observer would be tinted (colour mixing) http://en.wikipedia.org/wiki/Color_mixing
« Last Edit: 02/10/2012 10:45 AM by Da5id »

Offline Rhyshaelkan

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Re: Sun Shade concepts for Venus
« Reply #61 on: 01/30/2012 01:30 PM »
Due to non-existent magnetic field Venus has lost its hydrogen(if it ever had it) over the billions of years of its life. If there is a solution for terraforming Venus we need:

Shades and reflectors that can mimic a normal rotation.

Cables encircling Venus to give it an electro-magnetic sheath. This could be powered by photoelectric cells or other solar engines on the shades/reflectors. Several cables at different orbits and different altitudes so as to not interfere with each other.

A massive influx of hydrogen. This will bond with the CO in Venus' atmosphere and rain down water, carboxl and other amino-acids, carbohydrates, and hydrocarbons. Throw in generous amounts of nitrogen, and we could see Earth's early history in evolution.

Even if the Sun does burn Venus to a cinder in 200 million years. That is time enough for whole periods of life to rise and fall. We need a decent engine to get out to the Kuiper Belt and deliver the necessary raw materials.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #62 on: 01/30/2012 08:54 PM »
A gas would be quickly dispersed and blown away like a comets tail, more substantial particles would pose a hazard. It would just turn into a dust belt in the inner solar system. I guess the laser is to provide light on the night side of Venus? Think about just how much energy would be required (over 100,000,000,000,000 kW), a laser that size could send you to the stars
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #63 on: 01/31/2012 12:54 PM »
A gas would be quickly dispersed and blown away like a comets tail, more substantial particles would pose a hazard. It would just turn into a dust belt in the inner solar system. I guess the laser is to provide light on the night side of Venus? Think about just how much energy would be required (over 100,000,000,000,000 kW), a laser that size could send you to the stars
A gas shaped disc at Venus L1 could possibly be held in place  by an optical-trapping system, this is currently being studied at Nasa (Tractor beams) http://www.bbc.co.uk/news/science-environment-15535115
The spread laser light would  shine through the disc, edge on to illuminate and tint the gas. I wouldnt think you need very high powered lasers for that. 
« Last Edit: 01/31/2012 12:57 PM by Da5id »

Offline dcporter

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Re: Sun Shade concepts for Venus
« Reply #64 on: 01/31/2012 03:54 PM »
Sorry, what's the purpose of illuminating and tinting the fog?

Offline Sohl

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Re: Sun Shade concepts for Venus
« Reply #65 on: 01/31/2012 05:53 PM »
"To Shade the Sun."

Da5id: Based on these postings, I expected you to be youngish student, but your profile says otherwise.  It seems you misunderstand some physics.

Unless I (and others?) are missing something in your concept, illuminating a cloud of dust won't affect optical properties like opacity at all.  Would shining a laser up from the surface of Earth onto a bank of clouds make it block even more of the Sun's heat and light?  I'm nearly certain the answer is no.  The only exception I can think of is a non-linear optical material, where illuminating the material sets up a change in charge distribution.  Anyway, I don't think ordinary dust or gas vapor would be non-linear enough to make your proposal work.  It just makes the dust or vapor light up (probably sending some fraction of the energy on to the planet), perhaps in a pretty way.

The optical tractor beam research, I think, is only for pinning or optically moving very small particles, one at a time, say for sampling dust by a space probe.  Not practical now for controlling diffuse and massive quantities of anything.

I think the "heat it up even more" ideas posted by others here have merit, if you can pump enough energy into the atmosphere to make it expand and blow off, turning it it a mega-comet for a while.  Actually, some pretty wild theories posit that Venus _is_ a historically recent mega-comet that was captured into its present orbit and is still cooling down. 

Offline as58

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Re: Sun Shade concepts for Venus
« Reply #66 on: 01/31/2012 08:28 PM »

Unless I (and others?) are missing something in your concept, illuminating a cloud of dust won't affect optical properties like opacity at all.  Would shining a laser up from the surface of Earth onto a bank of clouds make it block even more of the Sun's heat and light?  I'm nearly certain the answer is no.  The only exception I can think of is a non-linear optical material, where illuminating the material sets up a change in charge distribution.  Anyway, I don't think ordinary dust or gas vapor would be non-linear enough to make your proposal work.  It just makes the dust or vapor light up (probably sending some fraction of the energy on to the planet), perhaps in a pretty way.

Heating can change the opacity of pretty much anything, you don't need exotic materials for that... However, I agree that Da5id seems to have misunderstood something

Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #67 on: 01/31/2012 08:57 PM »
"To Shade the Sun."

Da5id: Based on these postings, I expected you to be youngish student, but your profile says otherwise.  It seems you misunderstand some physics.

Unless I (and others?) are missing something in your concept, illuminating a cloud of dust won't affect optical properties like opacity at all.  Would shining a laser up from the surface of Earth onto a bank of clouds make it block even more of the Sun's heat and light?  I'm nearly certain the answer is no.  The only exception I can think of is a non-linear optical material, where illuminating the material sets up a change in charge distribution.  Anyway, I don't think ordinary dust or gas vapor would be non-linear enough to make your proposal work.  It just makes the dust or vapor light up (probably sending some fraction of the energy on to the planet), perhaps in a pretty way.

The optical tractor beam research, I think, is only for pinning or optically moving very small particles, one at a time, say for sampling dust by a space probe.  Not practical now for controlling diffuse and massive quantities of anything.

I think the "heat it up even more" ideas posted by others here have merit, if you can pump enough energy into the atmosphere to make it expand and blow off, turning it it a mega-comet for a while.  Actually, some pretty wild theories posit that Venus _is_ a historically recent mega-comet that was captured into its present orbit and is still cooling down. 


The fog/plasma would be there just for something the lasers can project on to, it would serve no other purpose. Its's the layers of lasers I am trying to explain.

If you can imagine two lasers as a two sheets of thin round glass, one coloured Red another Blue, looked at flat on would appear a muddy dark brown. Several more of these combined would almost be black.

The optical tractor beam, well the time humans are ready to terraform Venus
Im sure they will be able to move more than particles





« Last Edit: 02/10/2012 10:29 AM by Da5id »

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #68 on: 01/31/2012 09:58 PM »
What Sohl said.
 Lasers will only affect the opacity of the gas if they cause a photochemical reaction, the illumination of clouds with lasers wont affect their opacity to sunlight.
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #69 on: 02/01/2012 04:09 AM »
"To Shade the Sun."

Da5id: Based on these postings, I expected you to be youngish student, but your profile says otherwise.  It seems you misunderstand some physics.

Unless I (and others?) are missing something in your concept, illuminating a cloud of dust won't affect optical properties like opacity at all.  Would shining a laser up from the surface of Earth onto a bank of clouds make it block even more of the Sun's heat and light?  I'm nearly certain the answer is no.  The only exception I can think of is a non-linear optical material, where illuminating the material sets up a change in charge distribution.  Anyway, I don't think ordinary dust or gas vapor would be non-linear enough to make your proposal work.  It just makes the dust or vapor light up (probably sending some fraction of the energy on to the planet), perhaps in a pretty way.

The optical tractor beam research, I think, is only for pinning or optically moving very small particles, one at a time, say for sampling dust by a space probe.  Not practical now for controlling diffuse and massive quantities of anything.

I think the "heat it up even more" ideas posted by others here have merit, if you can pump enough energy into the atmosphere to make it expand and blow off, turning it it a mega-comet for a while.  Actually, some pretty wild theories posit that Venus _is_ a historically recent mega-comet that was captured into its present orbit and is still cooling down. 

No not a student my profession is in visual arts industry.

The fog/plasma would be there just for something the lasers can project on to, it would serve no other purpose. Its's the layers of lasers I am trying to explain.

If you can imagine three lasers as a three sheets of thin round glass, one coloured yellow another cyan and the other magenta, looked at flat on would appear a muddy dark brown. Several more of these combined would almost be black.

The optical tractor beam, well the time humans are ready to terraform Venus
Im sure they will be able to move more than particles






Infrared light is what also needs to be blocked, not just visible light.
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Offline dcporter

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Re: Sun Shade concepts for Venus
« Reply #70 on: 02/01/2012 04:41 AM »
Regardless, you don't turn something translucent to opaque by making it glow the color you're trying to block.

Offline Sohl

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Re: Sun Shade concepts for Venus
« Reply #71 on: 02/01/2012 04:25 PM »
"No not a student my profession is in visual arts industry."

Da5id: Then am I wrong to assume you know about the difference beteen "additive colors" (e.g. colored spotlights shining on the same spot, phosphors on a TV or LCD screen) and "subtractive colors" (e.g. pigments mixing together like in oil paint and inkjet printers)?  Lasers on a fog/cloud would be additive.  You cant get something blacker by shining _more_ light on it (ignoring any unlikely photochemical reaction as was said earlier).

Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #72 on: 02/01/2012 07:27 PM »
"No not a student my profession is in visual arts industry."

Da5id: Then am I wrong to assume you know about the difference beteen "additive colors" (e.g. colored spotlights shining on the same spot, phosphors on a TV or LCD screen) and "subtractive colors" (e.g. pigments mixing together like in oil paint and inkjet printers)?  Lasers on a fog/cloud would be additive.  You cant get something blacker by shining _more_ light on it (ignoring any unlikely photochemical reaction as was said earlier).
I am talking about multiple levels of different coloured sliced Lasers beams, separated by small gaps between . Looked at side on, through the levels, with a light source behind (the Sun) The many levels of tinted lasers would filter the  Sun light.  Like Earth light on a Lunar eclipse.

 I am not suggesting mixing or combining the beams and shining on one spot or light up all the fog to make it glow. The fog is only used so the beam tint of the lasers can be seen.


« Last Edit: 02/10/2012 10:34 AM by Da5id »

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #73 on: 02/02/2012 04:05 AM »
"No not a student my profession is in visual arts industry."

Da5id: Then am I wrong to assume you know about the difference beteen "additive colors" (e.g. colored spotlights shining on the same spot, phosphors on a TV or LCD screen) and "subtractive colors" (e.g. pigments mixing together like in oil paint and inkjet printers)?  Lasers on a fog/cloud would be additive.  You cant get something blacker by shining _more_ light on it (ignoring any unlikely photochemical reaction as was said earlier).
I am talking about multiple levels of different coloured Lasers, separated by small gaps between . Looked at side on, through the levels, with a light source behind (the Sun) The many levels of tinted lasers would filter the  Sun light. 

 I am not suggesting mixing the beams and shining on one spot or light up all the fog to make it glow. The fog is only used so the beam tint of the lasers can be seen.



Has anyone tried this in the lab to see if how much if any amount of Sun radiation ( type that would heat Venus atmosphere and surface mass ) would be blocked by this idea?

Any idea how much power just the lasers would need?
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #74 on: 02/02/2012 08:12 AM »

Has anyone tried this in the lab to see if how much if any amount of Sun radiation ( type that would heat Venus atmosphere and surface mass ) would be blocked by this idea?

Any idea how much power just the lasers would need?

No power at all because the physics is wrong. See Sohl's original post.
« Last Edit: 02/02/2012 08:53 AM by douglas100 »
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #75 on: 02/02/2012 11:27 PM »

Has anyone tried this in the lab to see if how much if any amount of Sun radiation ( type that would heat Venus atmosphere and surface mass ) would be blocked by this idea?

Any idea how much power just the lasers would need?

No power at all because the physics is wrong. See Sohl's original post.
In all fairness to poster Da5id I had to ask after the posters last post. Experimentation over what we think. We have been proven wrong before from what we think and what really does happen in reality.

I personally believe the solar sail concept would work in blocking out the Suns radiation ( enough to allow Venus to cool down ). Blocking Sun light has been done to keep buildings cool ( shade then ).

Once cooled then we need to address the problem of the high pressure atmosphere, lack of O2, and H2O. If their is water under the surface that can be reached then might be possible to grow plants to change the CO2 to O2 and take the carbon to make the plant structure. That would reducing the atmosphere pressure taking material from the atmosphere to make the plant structure.
« Last Edit: 02/02/2012 11:30 PM by RocketmanUS »
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Offline Patchouli

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Re: Sun Shade concepts for Venus
« Reply #76 on: 02/03/2012 01:46 AM »
I wonder if one solution might be to redirect comets and asteroids at Venus some to impact and other in flybys to accomplish four things.
First throw dust into it's atmosphere causing an impact winter, two hopefully bast some of the atmosphere away,three seed the planet with hydrogen, and four impart some spin.

The bad part is this can put Earth at risk.
« Last Edit: 02/03/2012 01:49 AM by Patchouli »

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #77 on: 02/03/2012 02:07 AM »
I wonder if one solution might be to redirect comets and asteroids at Venus some to impact and other in flybys to accomplish four things.
First throw dust into it's atmosphere causing an impact winter, two hopefully bast some of the atmosphere away,three seed the planet with hydrogen, and four impart some spin.

The bad part is this can put Earth at risk.
For the spin up

If Venus was to have a 24hr rotation what impact if any would have on other bodies in the solar system?

How would this effect the gravitational pull on an object on the surface?

How would this effect the surface temp. up or down?

Less time to absorb solar energy at day time and less time to radiate heat at night time. How would this effect the winds at different altitudes?
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Offline Patchouli

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Re: Sun Shade concepts for Venus
« Reply #78 on: 02/03/2012 02:26 AM »

For the spin up

If Venus was to have a 24hr rotation what impact if any would have on other bodies in the solar system?
it would have no effect on other bodies.

Quote
How would this effect the gravitational pull on an object on the surface?
The effect on surface gravity would be negligible.
 
Quote
How would this effect the surface temp. up or down?

Less time to absorb solar energy at day time and less time to radiate heat at night time. How would this effect the winds at different altitudes?

The main reason I'd want to spin it up is that's the missing ingredient for a geomagnetic field.

The effects on average temps would be minor.
But it would greatly reduce the temperature swings on a terraformed Venus by preventing the day lite side from burning up and the night side from freezing.
« Last Edit: 02/03/2012 02:27 AM by Patchouli »

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #79 on: 02/03/2012 02:37 AM »

For the spin up

If Venus was to have a 24hr rotation what impact if any would have on other bodies in the solar system?
it would have no effect on other bodies.

Quote
How would this effect the gravitational pull on an object on the surface?
The effect on surface gravity would be negligible.
 
Quote
How would this effect the surface temp. up or down?

Less time to absorb solar energy at day time and less time to radiate heat at night time. How would this effect the winds at different altitudes?

The main reason I'd want to spin it up is that's the missing ingredient for a geomagnetic field.

The effects on average temps would be minor.
But it would greatly reduce the temperature swings on a terraformed Venus by preventing the day lite side from burning up and the night side from freezing.
So if had a 24hr day then would not have the high winds in a terraformed Venus? ( One side hot , one side cold if not spun up )
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #80 on: 02/03/2012 11:29 AM »

Has anyone tried this in the lab to see if how much if any amount of Sun radiation ( type that would heat Venus atmosphere and surface mass ) would be blocked by this idea?

Any idea how much power just the lasers would need?

No power at all because the physics is wrong. See Sohl's original post.

 The physics is wrong because Sohls interpretation of the original idea is wrong.
Light through a translucent medium will fade out light eventually, depending on it's density.
« Last Edit: 02/03/2012 01:50 PM by Da5id »

Offline dcporter

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Re: Sun Shade concepts for Venus
« Reply #81 on: 02/03/2012 02:26 PM »
So you're saying fog alone should do this? The lasers are just for fun?

Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #82 on: 02/03/2012 02:55 PM »
So you're saying fog alone should do this? The lasers are just for fun?

The Multiple layers of Lasers do the work of colour subtraction dimming in turn the next level of fog  down and so on, so the complete fog would not need to be so dense.

Correction:That of course would be additive not subtraction in colour. I made a mistake in the description.
« Last Edit: 02/10/2012 10:38 AM by Da5id »

Offline Sohl

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Re: Sun Shade concepts for Venus
« Reply #83 on: 02/03/2012 06:36 PM »
"The Multiple layers of Lasers do the work of colour subtraction dimming ..."

[ smacks forhead ]  In the chance you are not just goading me, I will try one more time.

Shining light is not subtracting.  It's adding.  Subtractive colors need pigment,  not laser light.  Pigment particles absorb the incoming light and then readmit that energy in a lower frequency form, like UV->visible light with florescent paint or increased thermal energy in the pigment itself (black paint heats up more than white).

Of course fog will dimish light, mostly by scattering it in different directions and perhaps  some modest amounts of absorbtion. If the fog is thick enough, it will shade the ground/object which would otherwise be lit and heated by the Sun.  All by itself. 

Adding _more_ light with lasers will not help it block more light.  The one exception is if the lasers somehow trigger a photochemical change in the fog droplets or cloud particals so they absorb or reflect light differently than they did before.  But it would be far easier and probably much more efficient to form your fog or cloud out of something already relatively good at absorbing or reflecting.  In other words, make a cloud out of stuff that is already a good pigment.  Or make it out of something already reflective.  Snow?  Won't stay frozen there, but I hope you get the idea.  You don't need lasers.  They won't help at all with the vast majority of materials you could make a cloud out of.  They may look pretty.

RocketmanUS said "Experimentation over what we think".  Yes I agree.  I would propose the following:

1) Get a nice strong spotlight that provides a color spectrum similar to the Sun.

2) Shine it at a target several feet away.  Measure the brightness.

3) Get a glass box.  Fill it with whatever fog/cloud you want.  Dry ice in water?  Stage fog?  Wood smoke?  Carbon dust?  I don't think it matter much.

4) Put the box in the path of the spotlight beam.  Measure the amount of light at the target, now reduced by some % from the no-box case.  Also observe the beam from the side as it passes through the box.  You will see it "light up" the cloud in the box. If the cloud is thick enough, you might even notice the cloud is brighter on the entry side than the exit side, just as you would expect from cumulative dimming.

5) Now shine whatever combination of lasers into the cloud in the box.  You can make curtain patterns or whatever pattern you like. Then measure the amount of the light reaching the target. 

My prediction is that you you won't get less of the spotlight beam getting through.  You seem to think it will.  If you are in the visual arts, you should be able to set up a stage with this experiment.  Try it and tell us what happens.
In fact, I am very certain it will be slightly _higher_ than the previous step if anything, because you are pumping _more_ light into the box and some of that additional light will be scattered toward the target. 

Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #84 on: 02/03/2012 10:49 PM »


My prediction is that you you won't get less of the spotlight beam getting through.  You seem to think it will.  If you are in the visual arts, you should be able to set up a stage with this experiment.  Try it and tell us what happens.
In fact, I am very certain it will be slightly _higher_ than the previous step if anything, because you are pumping _more_ light into the box and some of that additional light will be scattered toward the target. 

Well using the combination of laser as I mentioned earlier I think it may come out a very very translucent  brown, (If the laser curtains can act similar to a gel filter that is).
  How ever I do not have access or resources to set up such experiment. It does give me food for thought.

I would like to thank every one for the replies, Its probably clear I'm thinking way out side the box.
« Last Edit: 02/03/2012 10:50 PM by Da5id »

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #85 on: 02/03/2012 11:40 PM »


My prediction is that you you won't get less of the spotlight beam getting through.  You seem to think it will.  If you are in the visual arts, you should be able to set up a stage with this experiment.  Try it and tell us what happens.
In fact, I am very certain it will be slightly _higher_ than the previous step if anything, because you are pumping _more_ light into the box and some of that additional light will be scattered toward the target. 

Well using the combination of laser as I mentioned earlier I think it may come out a very very translucent  brown, (If the laser curtains can act similar to a gel filter that is).
  How ever I do not have access or resources to set up such experiment. It does give me food for thought.

I would like to thank every one for the replies, Its probably clear I'm thinking way out side the box.

Might try contacring Mythbusters. They could if they like the idea for their show set up some experiments, your idea and the solar sail idea.

For the solar sail idea. Place an ice cube on a plate and shine a heat lamp on it from several feet away from above. Time how long it take to melt the ice cube. Now do the same but with a piece of refective mylar ( from helium baloon ) between the heat lamp and the ice cube so the mylar will cast a shadow over the ice cube. Do this indoors with the inside temp around 70 to 80 deg fahrenheit, have the room temp the same for both with and without the mylar shade. Now try an ice cube on the plate without the heat lamp so we know the rate it melts at room temp. This all has to be done away from an open window so that the Sun's light will not play a part in the experiment ( best at night ).

My take is the unshaded ice cube under the heat lamp will melt fastest. The shaded ice cube under the heat lamp will melt slower and the ice cub with no heat lamp will melt the slowest.

You could also try this with colored filters instead of the reflective mylar to see what type of results you get. Not the same as the fog and laser though. Keep in mind that fog can reflect and or refract laser light.
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Offline dcporter

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Re: Sun Shade concepts for Venus
« Reply #86 on: 02/04/2012 02:47 AM »
Well using the combination of laser as I mentioned earlier I think it may come out a very very translucent  brown, (If the laser curtains can act similar to a gel filter that is).

They don't act like gels. Adding lasers together makes more white light not less brown light. Think of it this way: the gels are colored before the light comes along; the fog wouldn't be colored until the laser light shows up. That means you're adding instead of subtracting.

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #87 on: 02/04/2012 03:08 AM »
O3

If we made O3 from CO2 and the extra carbon made a ball out of it to drop to the surface.

So if we released O3 in the upper atmosphere would this help reduce heating?
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #88 on: 02/04/2012 08:23 AM »
Well using the combination of laser as I mentioned earlier I think it may come out a very very translucent  brown, (If the laser curtains can act similar to a gel filter that is).

They don't act like gels. Adding lasers together makes more white light not less brown light. Think of it this way: the gels are colored before the light comes along; the fog wouldn't be colored until the laser light shows up. That means you're adding instead of subtracting.
I think what best Im trying to describe or set up is levels of holograms acting as filters. (removing the need for fog altogether) .

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #89 on: 02/04/2012 09:38 AM »

The physics is wrong because Sohls interpretation of the original idea is wrong.

Light through a translucent medium will fade out light eventually, depending on it's density.

No, your idea is wrong. You can't block light with light.
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« Last Edit: 02/05/2012 05:24 PM by Da5id »

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #91 on: 02/06/2012 06:50 AM »
Terraforming Venus

When to cool it down?

To cool Venus down we need to block the heat source.

Or we need to change the atmosphere and most likely the planets rotation speed around it's axis to about a 24hr cycle.

Bringing the day cycle to around a 24hr time frame should calm the winds down.

So it probable is a better idea to look to see what type of atmosphere Venus will need to support human life, animals , and plants ( more Earth like ). What would the pressure need to be at different altitudes. What would the N2,O2,CO2,H2O, ect. percentages need to be. Would there be an O3 layer. Knowing what it all needs to be first will help us know how best to go about terraforming Venus.

So we might start by changing the ratation speed of the planet about it's axis. Then start the conversion process of the atmosphere. So how can that be done? That would most likely bring the temp. down to were we need it to be. So there might not be a need to block the Sun light? 
« Last Edit: 02/06/2012 06:52 AM by RocketmanUS »
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #92 on: 02/06/2012 08:43 AM »



 You can't block light with light.

I beg to differ.
http://www.livescience.com/8012-twisted-physics-scientists-create-light-knots.html
But It can be manipulated.


You are correct that light can be manipulated. But my point still stands. The article you cite is about holograms. A hologram is a physical object which intercepts the light. A giant hologram put in front of Venus would certainly reduce the amount of light reaching the planet. But that is not what was being proposed.

I wasn't going to post on this thread again, having criticised the need to ever attempt to terraform Venus and the enormity of the effort required to do it. It is a task for a civilisation well up the Kardashev scale. But treating it as a purely theoretical exercise, the most straightforward way to shade Venus using foreseeable technology would be to use a very large number of solar sails. I think that a single giant shade would be very difficult to make and would be subject to tidal forces that would make it hard to control. A cloud of billions of small solar sails, each kilometers in size and independently maneuverable would be a better solution.

As for spinning up Venus, well it's OT and the effort and energy to do it is magnitudes greater than building a planetary sun shade.

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Offline Sohl

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Re: Sun Shade concepts for Venus
« Reply #93 on: 02/06/2012 05:47 PM »
"I think what best Im trying to describe or set up is levels of holograms acting as filters. (removing the need for fog altogether) . "

Da5id: I think you misunderstand the definition of hologram, and seem to say that any pattern of interference of lasers _is_ a hologram.  It is not. 

You really need to go read a book on electro-magnetic physics, or at least a few chapters on EM wave propogation in a vacuum. A guy named Jackson wrote a seminal textbook used at the graduate level.  There are probably others that would be more accessible to someone at an undergraduate level.

If you cross two or more beams in empty vacuum, the waves of the electro-magnetic field will "interferre" like crossing ripples in a pond, but each beam will travel straight through the others without diminishing.  Another beam (e.g. sun beam) will also travel straight through.  The interferrence pattern from the "hologram" lasers will not inhibit the sunbeam at all. 

It's like you are saying you could set up a few hoppers of pebbles along a beach and have the pebbles drop regularly into the ocean.  The pattern of ripples would interfere and make make a *shield* that would significantly absorb or reflect the incoming waves from the surf, to make it a nice placid beach! Still think it will work?  If you argue the ripples are too small compared to the surf waves, you can make the pebbles as big as you want.  Make 'em house-sized boulders. Won't help.


Offline Rhyshaelkan

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Re: Sun Shade concepts for Venus
« Reply #94 on: 02/06/2012 06:25 PM »
Venus Mass =   4,868,500,000,000,000,000,000,000 kg

As soon as we master space-time to induce a spin on Venus...

Lacking the mastery of space-time we could build a ring that both shades and reflects, to mimic a 24 hour cycle. Early on though it would be 100% shade to reduce temps to something Earth normal. Large quantities of gasses will need to be imported to provide an adequate hydro and nitrogen cycle.
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #95 on: 02/06/2012 06:45 PM »



 You can't block light with light.

I beg to differ.
http://www.livescience.com/8012-twisted-physics-scientists-create-light-knots.html
But It can be manipulated.


You are correct that light can be manipulated. But my point still stands. The article you cite is about holograms. A hologram is a physical object which intercepts the light. A giant hologram put in front of Venus would certainly reduce the amount of light reaching the planet. But that is not what was being proposed.

I wasn't going to post on this thread again, having criticised the need to ever attempt to terraform Venus and the enormity of the effort required to do it. It is a task for a civilisation well up the Kardashev scale. But treating it as a purely theoretical exercise, the most straightforward way to shade Venus using foreseeable technology would be to use a very large number of solar sails. I think that a single giant shade would be very difficult to make and would be subject to tidal forces that would make it hard to control. A cloud of billions of small solar sails, each kilometers in size and independently maneuverable would be a better solution.

As for spinning up Venus, well it's OT and the effort and energy to do it is magnitudes greater than building a planetary sun shade.


More like 36 million solar sails 1 km x 1 km would effectively cover Venus on the Sun side in low orbit. At a given distance between the Sun and Venus 1,000 solar sails would do the job of shading Venus from the Sun light.
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Offline LegendCJS

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Re: Sun Shade concepts for Venus
« Reply #96 on: 02/06/2012 06:58 PM »
Venus Mass =   4,868,500,000,000,000,000,000,000 kg

As soon as we master space-time to induce a spin on Venus...

Lacking the mastery of space-time we could build a ring that both shades and reflects, to mimic a 24 hour cycle. Early on though it would be 100% shade to reduce temps to something Earth normal. Large quantities of gasses will need to be imported to provide an adequate hydro and nitrogen cycle.

Just a calculation fyi, haven't looked to see if it has been posted before.
 The Earth receives ~174 petawatts of energy from the sun.  Solar intensity is a little less than twice as high on Venus as on Earth, and the planets are roughly the same size, so I'm going to say that Venus receives 300 petawatts of energy from the sun.

The rotational kinetic energy of the earth of ~2*10^29 Joules.  The current rotational kenitic energy of Venus is close to 3*10^25 Joules.  So basically 2*10^29 joules of energy are needed to "spin up" Venus.

If some way could be found to convert this solar energy to rotational energy of Venus with 100% efficiency, for sake of upper-bound,  It would take over 22 thousand years to reach anything near a 24 hour cycle.

EDIT: upper-bound in terms of desirability, not time taken.
« Last Edit: 02/06/2012 06:58 PM by LegendCJS »
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Offline WellingtonEast

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Re: Sun Shade concepts for Venus
« Reply #97 on: 02/06/2012 08:21 PM »
I think "Patchouli" topic on using asteroid impacts warranted more detailed discussion.
   
We know single volcanic events can impact earth world weather so why is it not feasible that asteroids couldn't do the same for venus.

It is documented that there are smaller asteroids with water ice that we could possibly move one day (using current physics) such as :
http://www.nasa.gov/topics/earth/features/water_ice_asteroid.html

FYI - I am not proposing changing venus spin and moving large asteroids such as Vesta as that is only SCI Fi at the moment like inventing "unobtainium" metals and force fields.

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #98 on: 02/06/2012 10:00 PM »
Quote from: RocketmanUS link=topic=26743.msg858985#msg858985

[quote
More like 36 million solar sails 1 km x 1 km would effectively cover Venus on the Sun side in low orbit. At a given distance between the Sun and Venus 1,000 solar sails would do the job of shading Venus from the Sun light.

Yeah, I didn't bother calculating the cross sectional area of Venus. I get about 115 million square kilometers, but you're right that it's millions not billions.

However, you wouldn't want the sails in low Venus orbit, they would continuously collide with each other. It would be better to have them around the the Venus-Sun L1 point. Even there it would not be a trivial matter to control them in such a way as to block all solar radiation from reaching the planet.

I don't know where you get the 1000 figure from. You would need a greater area of sail as you moved the shade away from the planet toward the sun if you still wanted to block all the light.
« Last Edit: 02/07/2012 01:32 PM by douglas100 »
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #99 on: 02/07/2012 01:09 AM »
"Sun light passing through will project on Venus as a dark brownish hue. That's it"

Sunlight can't be filtered in this way

"Of course the idea hinges on. Can lasers act like a coloured filter?"

No. As has been explained to you again and again and again and...

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Offline 93143

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Re: Sun Shade concepts for Venus
« Reply #100 on: 02/07/2012 09:47 AM »
Those happen because the materials the light shines through absorb (or scatter) light unevenly across the visible spectrum, causing a bias in what wavelengths make it through.  This is a material property and is not directly related to what wavelengths of light are actually present.

Coloured filters and coloured lights work in opposite ways.  I'm afraid your idea betrays a lack of understanding of the physics of colour.

Pigments add to produce dark colours because pigments absorb light that isn't their colour, which is why they have colour in the first place.  Mix red and green pigments (as in layered filters, or paint on paper; it's all the same), and the green pigment will absorb red light and the red pigment will absorb green light.  Result?  Dark brown, almost black.

Coloured lights add to produce light colours, because the colour of light is an inherent, positive property that has nothing to do with absorption.  Mix red and green light, and the green light will stay exactly the way it is and the red light will stay exactly the way it is.  Result?  Bright yellow.

This is why there's a difference between additive primary colours and subtractive primary colours:

http://en.wikipedia.org/wiki/Primary_color
« Last Edit: 02/07/2012 09:52 AM by 93143 »

Offline tnphysics

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Re: Sun Shade concepts for Venus
« Reply #101 on: 02/08/2012 02:13 AM »
Those happen because the materials the light shines through absorb (or scatter) light unevenly across the visible spectrum, causing a bias in what wavelengths make it through.  This is a material property and is not directly related to what wavelengths of light are actually present.

Coloured filters and coloured lights work in opposite ways.  I'm afraid your idea betrays a lack of understanding of the physics of colour.

Pigments add to produce dark colours because pigments absorb light that isn't their colour, which is why they have colour in the first place.  Mix red and green pigments (as in layered filters, or paint on paper; it's all the same), and the green pigment will absorb red light and the red pigment will absorb green light.  Result?  Dark brown, almost black.

Coloured lights add to produce light colours, because the colour of light is an inherent, positive property that has nothing to do with absorption.  Mix red and green light, and the green light will stay exactly the way it is and the red light will stay exactly the way it is.  Result?  Bright yellow.

This is why there's a difference between additive primary colours and subtractive primary colours:

http://en.wikipedia.org/wiki/Primary_color

So OK, it won't work any way.


I shall take a bow and leave the stage.

I can see why you made the error-don't beat yourself up about it.

Keep being creative!

One thought I had was the idea of using nuclear explosions to redirect comets to slam into Venus. The comets would provide water and the impacts would hopefully eject some CO2. Furthermore, they (if sufficiently energetic) could pierce the crust and expose the CO2 to MgO and CaO.

Most importantly, the repeated impacts would blast light-absorbent dust into the atmosphere in huge quantities. The amount of light absorbed could be enough to significantly change the climate.

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #102 on: 02/08/2012 04:06 AM »
The easiest way to get water to Venus might be with a giant game of Kuiper belt billiards, select small (in the millions of tonnes) asteroidal/cometary objects passing close to Neptune, by altering their trajectory by a small amount before the swing-by a huge change to their orbit can be made with minimal expenditure. The aim is to direct these small objects into orbits that leads them to smack the real target comets (the billion tonnes plus ones you want to get to Venus) on the nose, killing enough of their solar orbital velocity to bring them in closer to the Sun for another orbit change through a swing-by of one of the gas giants.
 Doing it this way could reduce the energy expenditure by an order of magnitude compared to more direct methods.
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Offline dcporter

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Re: Sun Shade concepts for Venus
« Reply #103 on: 02/08/2012 03:56 PM »
One thought I had was the idea of using nuclear explosions to redirect comets to slam into Venus. The comets would provide water and the impacts would hopefully eject some CO2. Furthermore, they (if sufficiently energetic) could pierce the crust and expose the CO2 to MgO and CaO.
Would the explosions vaporize too much of the water you're looking to use?

Offline Tass

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Re: Sun Shade concepts for Venus
« Reply #104 on: 02/09/2012 09:52 AM »
One thought I had was the idea of using nuclear explosions to redirect comets to slam into Venus. The comets would provide water and the impacts would hopefully eject some CO2. Furthermore, they (if sufficiently energetic) could pierce the crust and expose the CO2 to MgO and CaO.
Would the explosions vaporize too much of the water you're looking to use?

Vaporized water is still water. What Venus needs is hydrogen. Add enough and when the dust settles (in a few thousand years) it will have water.

Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #105 on: 02/23/2012 11:21 PM »
Terraforming Venus
Or we need to change the atmosphere and most likely the planets rotation speed around it's axis to about a 24hr cycle.
Bringing the day cycle to around a 24hr time frame should calm the winds down.
So we might start by changing the ratation speed of the planet about it's axis. Then start the conversion process of the atmosphere. So how can that be done? That would most likely bring the temp. down to were we need it to be. So there might not be a need to block the Sun light? 

I have a modest suggestion.  Has anyone considered turning Venus into a homo-polar motor?  The basic idea goes something like this:
1-Place a gigantic solar powered ion beam cannon so that it is always above one pole of Venus. Since an ion cannon is also an ion thruster it could stay there as long as you had fuel to compensate for gravitational attraction. Just don't get too close.
2-Divert a comet or larger transuranic object to make a atmospheric grazing encounter with Venus. The fragmentation would make a spinning ring of ionized dust and gas going all the way down to the ionosphere.  The angle of the strike will determine the angle of the ring.
3-Turn on the ion cannon aiming at the perimeter of the ring.  A compensating electron beam will fire where we want the pole to be.
4-As electric charge builds up in the spinning ring a magnetic field will form per the right hand rule.  Electricity flowing outward will accelerate the particles in the ring all the way down to the ionosphere of Venus at right angles to the electric flow and induced magnetic field.
5-The neutralized particles in the ring perimeter will ultimately reach escape velocity and be dissipated to be replaced by more of the atmosphere.  Ultimately more of the air would be ionized as it spun around the planet with increasing speed.
6-Superhurricane winds are induced from the spinning ionosphere through angular momentum exchange down to the surface causing a slow increase of the planetary spin at the angle of the ring.  The ring will be self replenishing as more of the air and some the the surface is sucked up ionized and accelerated outward through the electromagnetic homopolar effect.
7- When enough of the air is gone and Venus is spun up enough turn off the ion cannon. If the original comet or moonlet has enough volatiles rain will begin to fall cooling the surface.  The residual ring if formed at a sufficient angle will add to the cooling effect.  Forming rain clouds during the shortened day and dispersing them at night perhaps by using the ion cannon at lower power will also cool things off.
8-If done right the planetary magnetic field and crustal tectonics may be induced from all this activity. Management of the remaining artificial ring and cloud formation will continue to maintain the environment.  Nevertheless the surface will be rather inhospitable until things settle down.
I realize this mega-project sounds ridiculous but no worse than slamming a thousand comets into Venus as some have suggested.  I'll leave it to physicists to determine energy needs and practicality.
 

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #106 on: 02/24/2012 09:58 AM »
That was ingenious. Like the use of the word "modest." :)
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Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #107 on: 02/24/2012 03:56 PM »
I have a modest suggestion.  ... I realize this mega-project sounds ridiculous but no worse than slamming a thousand comets into Venus as some have suggested.
  Neat idea! 

Could be combined with this if ring material could be compressed until the carbon is meta-stable, creating gigantic diamond sheets: 

...Venusian diamond ring.  ;)

The refractive index of diamond means you could build a big honker, (or a bunch of smaller ones in geosync) orbiting Venus along the ecliptic, to divert a lot of sunlight around the whole planet (to keep it dimmer and cooler for inhabitants).

If done right the planetary magnetic field and crustal tectonics may be induced from all this activity.
Could you elaborate on the mechanics of this?
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #108 on: 02/24/2012 07:27 PM »
Could be combined with this if ring material could be compressed until the carbon is meta-stable, creating gigantic diamond sheets: 
The refractive index of diamond means you could build a big honker, (or a bunch of smaller ones in geosync) orbiting Venus along the ecliptic, to divert a lot of sunlight around the whole planet (to keep it dimmer and cooler for inhabitants).
 Could you elaborate on the mechanics of this?

Actually I was thinking about introducing solar powered self replicating satellites into the ring shaped like flat reflective plates a meter wide. They'd scavenge the ring for raw material and make copies of themelves.  Computer commands would make them orient themselves as needed to shield or illuminate specific parts of the planetary surface. GPS would allow every satellite to know where it was and what it's role was.  Since the ring will be rotating opposite the direction of the planet I don't know how that will effect ring stability.  Might be better to start new with a new ring going in the proper direction.
Theory is that Venus has a rigid crust due to lack of water. Water gives the mantle elasticity to allow crustal subduction and therefore a heat gradient from the core out. No heat gradient combined with slow spin eliminates magnetic field.  Every 500 million years heat buildup under the Venusian crust causes a cataclysmic resurfacing event. The crust sinks under a global magma ocean for thousands of years. Bad for terraforming. Hitting Venus with comets is like hitting an egg with a hammer and not expecting goo to splatter everywhere. My slow spin method is like rolling an egg over a hard surface to delicately crack the crust into plates to allow heat to escape and eventually become genuine tectonic plates as water in the mantle builds up. The increased spin (my idea is 15 earth days per venusian day-LegendCJS's 22 thousand years reduces to 85 years, long but not unreasonable) combined with heat convection will regenerate the magnetic field.  The induced magnetic field in the ring may help kick start it as well.

Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #109 on: 02/26/2012 12:46 AM »
Interesting thoughts and ideas!!

I hadn't realized Venus had a 500 million year catastrophic cycle.  I have some reading to do!

Why 15 days? 
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #110 on: 02/26/2012 04:57 PM »
Interesting thoughts and ideas!!

I hadn't realized Venus had a 500 million year catastrophic cycle.  I have some reading to do!

Why 15 days? 

Terraforming doesn't have to mean making the planet exactly like earth, just livable. 15 days seemed a reasonable day period that could be achieved within a century with a "reasonable" energy budget. This is based on the fact that rotational kinetic energy is = .5 * Moment of inertia* angular velocity squared.  The energy needs for speeding up rotation can explode if you try to get too close to an earth day.  That will give about 16 sidereal days per year  Since venus spins retrograde one solar day will be gained per year. That gives an average solar day period of approx. 14 earth days, 7 days of sun and 7 of night.  The ring will provide light as needed during the long night and cloud creation and dissipation will control solar radiation with assist from the ring.  Animals and plants can be bioengineered to prosper in such an extended diurnal cycle.

Similarly I think reducing the Venusian atmosphere to 1 bar pressure may be too extreme.  Plants and animals could be adapted a 10 -20 bar surface pressure. Oxygen/nitrogen partial pressure would be earth normal but the majority of the atmosphere would remain carbon dioxide.  Biology of living things including humans could be modified to resist the toxic effects of carbon dioxide.  Frankly the plants would love it!  The greenhouse effects of CO2 would have to be dealt with either by the shielding systems described previously or perhaps by controlled stimulated emission of atmospheric heat using the previously mentioned ion cannon.
Humans not wishing to 'go native' would reside in climate controlled aerostats floating miles above the surface where air pressue and chemistry is closer to earth normal.  Since earth air is lighter than CO2 you would literally live in the 'gas bag'.  Access to space by shuttle would be provided by aircraft carrier dirigibles and a Rotating tether Rotovator system orbiting within the ring.

All of this is dependent on the homopolar motor concept working. I'm beginning to doubt if a properly oriented self regenerating magnetic field could be sustained to do the work as I described.  Modeling a complex system involving global atmospheric electric current flow and planetary ring particle dynamics is beyond by ability. But at least it's elegant.

Offline Archer

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Re: Sun Shade concepts for Venus
« Reply #111 on: 02/26/2012 08:27 PM »
Why do you want to change day/night duration after all? Long day (dawn, sunset) is strange, yet quite exotic :)

PS. I remember I was trying to calculate how much of Sun's energy can be reflected, if some (and large) areas of Venus would be cowered with something very reflecting, like aluminum powder - to reduce amount of sunlight consumed by the planet (after the planet is cooled down, we can use plants (genetically engineered) that have reflecting leafs - to make system self-sustaining). I figured out that I don't know too much (
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #112 on: 02/28/2012 04:11 AM »
Why do you want to change day/night duration after all? Long day (dawn, sunset) is strange, yet quite exotic :)

PS. I remember I was trying to calculate how much of Sun's energy can be reflected, if some (and large) areas of Venus would be cowered with something very reflecting, like aluminum powder - to reduce amount of sunlight consumed by the planet (after the planet is cooled down, we can use plants (genetically engineered) that have reflecting leafs - to make system self-sustaining). I figured out that I don't know too much (
Plants need light to grow and who wants a half month a darkness or light. The planet would shade it's self with a 24 hour period of rotation. One area would not get to much Sun light and over heat while the other side gets to cold and starts super high winds with the temperature difference. Better chance of controlling the temperature with a fast rotation. Plants do play a big part in global weather stabilization, but there is no need to genetically alter then. If we alter the DNA we have found that we end up with more problems then we thought we had solved ( I've know people in bio engineering for crops to resist pest and we ended up with food that was not as health for us to consume ). 
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Re: Sun Shade concepts for Venus
« Reply #113 on: 02/28/2012 04:34 AM »
The energy required to get the planet on a fast rotation is rather large, and wouldn't some of that energy end up being released in tectonic activity? Surely it's simpler to just use space mirrors to achieve a 24 hour day-night cycle?

 
« Last Edit: 02/28/2012 05:11 AM by Andrew_W »
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #114 on: 02/28/2012 05:00 AM »
As far as space mirrors, trying to keep them in exact place might not be easy. Also how would it effect the Suns radiation? Would it not reflect it all as it got it? Would some of the wave lengths not change and or be absorbed be the mirror? How to handle if one of the mirrors were damaged? Plus any other cost in maintenance and or installing them?

A possible way to increase the planets rotation is to use the light from the Sun. Around the equator build up mounds with one side of the mound to reflect the Sun light. One side of the mounds would be layered with material from Venus surface with high reflection and the other side with a less reflective property. Dams use water that push on peddles attached to wheels to turn generators. The mound act like the peddles and the ground around the equator acts like the wheel to increase the rotation of the planet. A slow increase over time.   
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #115 on: 02/28/2012 08:12 AM »

A possible way to increase the planets rotation is to use the light from the Sun. Around the equator build up mounds with one side of the mound to reflect the Sun light.   

Well, the Yarkovsky effect can alter the spin rate of asteroids as a result of solar radiation, but this is a planet we're talking about. Solar radiation pressure even at Venus's orbit is minuscule compared with the mass you are trying to influence. I doubt you could change the spin rate of Venus by any significant amount over the remaining lifetime of the Solar System by this method.
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #116 on: 02/28/2012 11:15 AM »

A possible way to increase the planets rotation is to use the light from the Sun. Around the equator build up mounds with one side of the mound to reflect the Sun light.   

Well, the Yarkovsky effect can alter the spin rate of asteroids as a result of solar radiation, but this is a planet we're talking about. Solar radiation pressure even at Venus's orbit is minuscule compared with the mass you are trying to influence. I doubt you could change the spin rate of Venus by any significant amount over the remaining lifetime of the Solar System by this method.

 Hundreds of thousands to maybe millions of nuclear atomic directional bomb blasts placed at the side of mountains, specially around the equator, and let off at the same time. Would this have an effect on rotation. Bit like a Hero's steam turbine.
« Last Edit: 02/28/2012 11:23 AM by Da5id »

Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #117 on: 02/28/2012 02:34 PM »

Well, the Yarkovsky effect can alter the spin rate of asteroids as a result of solar radiation, but this is a planet we're talking about. Solar radiation pressure even at Venus's orbit is minuscule compared with the mass you are trying to influence. I doubt you could change the spin rate of Venus by any significant amount over the remaining lifetime of the Solar System by this method.

Attached is a link that demonstrates the rotating momentum exchange effect on a conductive fluid I have suggested.  In it's earliest stage a planetary ring could be modeled as a conductive fluid. Electric current could maintain it in that state all the way down to the ionized atmosphere.  Of course the electrical current requirements will be astronomical and there is still that pesky issue of availability of a strong enough magnetic field.  ;)

http://www.evilmadscientist.com/article.php/SimpleMHD

Offline LegendCJS

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Re: Sun Shade concepts for Venus
« Reply #118 on: 02/28/2012 02:50 PM »

A possible way to increase the planets rotation is to use the light from the Sun. Around the equator build up mounds with one side of the mound to reflect the Sun light.   

Well, the Yarkovsky effect can alter the spin rate of asteroids as a result of solar radiation, but this is a planet we're talking about. Solar radiation pressure even at Venus's orbit is minuscule compared with the mass you are trying to influence. I doubt you could change the spin rate of Venus by any significant amount over the remaining lifetime of the Solar System by this method.

 Hundreds of thousands to maybe millions of nuclear atomic directional bomb blasts placed at the side of mountains, specially around the equator, and let off at the same time. Would this have an effect on rotation. Bit like a Hero's steam turbine.

No.  The bomb blasts would not be powerful enough to eject material into space, and without mass leaving Venus to carry away momentum there would be no effect what so ever on the rotation of Venus once all the dust settled.
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #119 on: 02/28/2012 02:55 PM »

No.  The bomb blasts would not be powerful enough to eject material into space, and without mass leaving Venus to carry away momentum there would be no effect what so ever on the rotation of Venus once all the dust settled.

Thank you. You beat me to it.
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #120 on: 02/28/2012 02:59 PM »

Of course the electrical current requirements will be astronomical and there is still that pesky issue of availability of a strong enough magnetic field.  ;)

Let's turn Venus into a magnetar. That should do it!  ;D
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #121 on: 02/28/2012 04:41 PM »

A possible way to increase the planets rotation is to use the light from the Sun. Around the equator build up mounds with one side of the mound to reflect the Sun light.   

Well, the Yarkovsky effect can alter the spin rate of asteroids as a result of solar radiation, but this is a planet we're talking about. Solar radiation pressure even at Venus's orbit is minuscule compared with the mass you are trying to influence. I doubt you could change the spin rate of Venus by any significant amount over the remaining lifetime of the Solar System by this method.

 Hundreds of thousands to maybe millions of nuclear atomic directional bomb blasts placed at the side of mountains, specially around the equator, and let off at the same time. Would this have an effect on rotation. Bit like a Hero's steam turbine.

No.  The bomb blasts would not be powerful enough to eject material into space, and without mass leaving Venus to carry away momentum there would be no effect what so ever on the rotation of Venus once all the dust settled.

I was really meaning a pushing effect rather than blasting.
Like Project Orion.

Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #122 on: 02/28/2012 05:06 PM »
Let's turn Venus into a magnetar. That should do it!  ;D

Heh! Perhaps scavenge magnets from the super sucker from SpaceBalls as someone suggested.

BTW
The mass of the Venusian atmosphere is 4.7*10^20 kg. To remove the gravitationally-bound atmosphere to Sun/Venus L1/L2, where it enters heliocentric orbit and disperses rapidly, Ei = 2.5*10^28 joules are required Ref-http://www.rfreitas.com/Astro/TerraformSRS1983.htm

That can be done by laboriously lifting the stuff up out of the gravity well or by flinging it out at escape velocity which allows you to use the reaction impulse to spin up the planet.

According to LegendCJS
'The rotational kinetic energy of the earth of ~2*10^29 Joules.  The current rotational kinetic energy of Venus is close to 3*10^25 Joules.  So basically 2*10^29 joules of energy are needed to "spin up" Venus.'

He's using the solar power of a disk the diameter of Venus assuming 100% efficiency so lets stay with that.

Obviously there isn't enough atmosphere to get Venus spin up to 1 earth day by a factor of 10 unless you REALLY fling the air out much faster. Wasteful of energy.

But spinning up Venus to a 15 day/night cycle in 85 years only requires approx 8.8*10^26 joules.  That's well within the available fuel (atmosphere) available and you'll even have atmosphere left.

After things settle down I'm convinced that the 15 day day will be perfectly acceptable to a properly selected and modified biosphere. That's half the day of the Moon. And remember that the leftover ring will be giving a great deal of reflected light during the night and clouds AND the ring will control a great deal of influent day sunlight. 

Offline LegendCJS

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Re: Sun Shade concepts for Venus
« Reply #123 on: 02/28/2012 05:30 PM »

A possible way to increase the planets rotation is to use the light from the Sun. Around the equator build up mounds with one side of the mound to reflect the Sun light.   

Well, the Yarkovsky effect can alter the spin rate of asteroids as a result of solar radiation, but this is a planet we're talking about. Solar radiation pressure even at Venus's orbit is minuscule compared with the mass you are trying to influence. I doubt you could change the spin rate of Venus by any significant amount over the remaining lifetime of the Solar System by this method.

 Hundreds of thousands to maybe millions of nuclear atomic directional bomb blasts placed at the side of mountains, specially around the equator, and let off at the same time. Would this have an effect on rotation. Bit like a Hero's steam turbine.

No.  The bomb blasts would not be powerful enough to eject material into space, and without mass leaving Venus to carry away momentum there would be no effect what so ever on the rotation of Venus once all the dust settled.

I was really meaning a pushing effect rather than blasting.
Like Project Orion.

Conservation of momentum doesn't care what you call it.  If all mass in the bomb ends up staying with Venus, no momentum is gained.  With project Orion, the majority of the mass of each charge ends up leaving the spacecraft for good carrying away momentum.  In space you also get transfer of momentum via photons from the bomb, but not so in an atmosphere as thick as Venus.

Edit: As a kind of snide side question, I'd really like to know what is your bomb bracing itself against to do this "pushing" on Venus?
« Last Edit: 02/28/2012 05:38 PM by LegendCJS »
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #124 on: 02/28/2012 05:41 PM »
Quote
only requires approx 8.8*10^26 joules.

2.8*10^10 GW centuries. 2.8 GW for 10 billion centuries.
I guess "only" is a relative term.

On the other hand it's only 2.2 seconds of total solar output.
« Last Edit: 02/28/2012 05:59 PM by Andrew_W »
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Offline Archer

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Re: Sun Shade concepts for Venus
« Reply #125 on: 02/28/2012 06:13 PM »
Quote
Plants need light to grow and who wants a half month a darkness or light
Like winter-summer cycle at Earth. During the Venus day (== summer) forests grow, during the night (== winter) small plants die, big ones go into anabiosis to be able to survive until dawn (== spring).
Maybe during the night there would be living plants that use planet heat as a power source (if terraforming companies will be able to create them).
Animals also need to be be very different from Earth ones.

You need to attract customers (and investors) to your Venus Terraforming Inc. somehow ;)
So many differences could be a good selling point. People like exotics.
« Last Edit: 02/28/2012 06:18 PM by Archer »
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #126 on: 02/28/2012 07:12 PM »
Quote
Plants need light to grow and who wants a half month a darkness or light
Like winter-summer cycle at Earth. During the Venus day (== summer) forests grow, during the night (== winter) small plants die, big ones go into anabiosis to be able to survive until dawn (== spring).
Maybe during the night there would be living plants that use planet heat as a power source (if terraforming companies will be able to create them).
Animals also need to be be very different from Earth ones.

You need to attract customers (and investors) to your Venus Terraforming Inc. somehow ;)
So many differences could be a good selling point. People like exotics.

Imagine a moist world where a fungal network connects all plantlife in lush jungles. During the long night smaller plants would derive nourishment from the network and during the day give it back. Every living thing would have the symbiotic fungus in their tissues providing sustenance and perhaps a form of bio-communication keeping things in balance.  During the night there would be a glow everywhere of the fungal symbiote in animals and plants.  A 10-20 bar thick atmosphere of mostly carbon dioxide would result in trees growing to enormous size.  Huge colonies of plants related to kelp would float in the moist air by means of air bladders filled with nitrogen/oxygen resembling floating mountains.  Huge reptilian bird creatures would nest in these flying mountains, effortlessly flying in the thick air and lighter gravity of Venus.  On some of their backs would be...blue blooded genetically modified humans, perhaps with an advanced hemocyanin in their viens to better resist carbon dioxide acidosis. 

How's that image for a Venus Terraforming Inc. advertising poster! ;D

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #127 on: 02/28/2012 11:02 PM »

Imagine a moist world where a fungal network connects all plantlife in lush jungles. During the long night smaller plants would derive nourishment from the network and during the day give it back. Every living thing would have the symbiotic fungus in their tissues providing sustenance and perhaps a form of bio-communication keeping things in balance.  During the night there would be a glow everywhere of the fungal symbiote in animals and plants.  A 10-20 bar thick atmosphere of mostly carbon dioxide would result in trees growing to enormous size.  Huge colonies of plants related to kelp would float in the moist air by means of air bladders filled with nitrogen/oxygen resembling floating mountains.  Huge reptilian bird creatures would nest in these flying mountains, effortlessly flying in the thick air and lighter gravity of Venus.  On some of their backs would be...blue blooded genetically modified humans, perhaps with an advanced hemocyanin in their viens to better resist carbon dioxide acidosis. 

How's that image for a Venus Terraforming Inc. advertising poster! ;D

See Olaf Stapeldon's Last and First Men. And that was written in 1930...
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #128 on: 02/29/2012 12:31 AM »
Start with Sun shade by solar sail.
Reduce atmosphere pressure by removing CO2 by on or more methods.

Once cooled and pressure lowered to Earth standers and O2 and N2 more like Earths for breathing. Then could place an outpost on Venus for exploration and mining.

Power source possible solar and geothermal.

Plant growth in green houses. During the long day have the green house covered for an 8 to 12 hour time to simulate night. During the long night use artificial light for an 8 to 15 hour period to simulate night time. Geothermal to keep plants warm if needed.

Later on if we could spin up the rotation to a 24hr day over time and after exploration then it might be possible to make Venus more Earth like.

Edit:
experiment, in a dark room shined a flashlight at a wall. Placed a piece of paper between flashlight and wall ( close to wall then close to flashlight ). Made a good shadow. So a solar sail at a given distance between Venus and the Sun would block a good portion of the Sun's radiation from getting to the Venus atmosphere. This would cause the day side to not have new heat energy to send to the night side throw the blowing wind. The night side would start to cool down and then pull warmer air from the day side. As the planet slowly rotates it will continue to cool. Final temperature would depend on part by how much energy from the Sun does manage to get to Venus past the solar sails shadowing.

 
« Last Edit: 02/29/2012 04:46 AM by RocketmanUS »
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #129 on: 02/29/2012 01:19 PM »
There has been discussion of using lasers to block sunlight and thereby cooling Venus. While I agree that this is not workable there is another technique using lasers that may work.  It's called laser cooling and there are several related techniques.  Gas atoms are excited by a precisely tuned laser beam and induced to radiate far more energy than they receive, dropping to a lower energy state, thereby cooling the gas.  If it could be applied on large scale to the Venusian atmosphere above the clouds then the re-radiated heat energy would be reflected from the clouds outward into space.  As the temperature dropped the upper atmosphere would become more dense and drop downward, upwelling more of the hotter gas closer to the surface which would radiate more heat.  Once this convective cycle was started perhaps only a relatively small amount of energy would be necessary to sustain it.  Modeling this technique would require a high speed centrifuge filled with gas with the temperature and composition of Venus.  At high G the gas would stratify to resemble on a small scale the conditions in the Venusian atmosphere.

en.wikipedia.org/wiki/Laser_cooling

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #130 on: 03/01/2012 05:12 AM »
There has been discussion of using lasers to block sunlight and thereby cooling Venus. While I agree that this is not workable there is another technique using lasers that may work.  It's called laser cooling and there are several related techniques.  Gas atoms are excited by a precisely tuned laser beam and induced to radiate far more energy than they receive, dropping to a lower energy state, thereby cooling the gas.  If it could be applied on large scale to the Venusian atmosphere above the clouds then the re-radiated heat energy would be reflected from the clouds outward into space.  As the temperature dropped the upper atmosphere would become more dense and drop downward, upwelling more of the hotter gas closer to the surface which would radiate more heat.  Once this convective cycle was started perhaps only a relatively small amount of energy would be necessary to sustain it.  Modeling this technique would require a high speed centrifuge filled with gas with the temperature and composition of Venus.  At high G the gas would stratify to resemble on a small scale the conditions in the Venusian atmosphere.

en.wikipedia.org/wiki/Laser_cooling
Read the link, I don't think that would work. One method only work with some elements. One of the big problems is the amount of energy needed to run all the lasers needed.

With all the wind on the surface, we should be able to use that to generate power. Separate the CO2 from the atmosphere and jet it at high velocity out of the atmosphere. With some of the CO2 leaving at escape velocity, removing heat and CO2. The problem with this idea is that we need CO2 for plant growth.


 
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #131 on: 03/01/2012 06:36 AM »
There has been discussion of using lasers to block sunlight and thereby cooling Venus. While I agree that this is not workable there is another technique using lasers that may work.  It's called laser cooling and there are several related techniques.  Gas atoms are excited by a precisely tuned laser beam and induced to radiate far more energy than they receive, dropping to a lower energy state, thereby cooling the gas.  If it could be applied on large scale to the Venusian atmosphere above the clouds then the re-radiated heat energy would be reflected from the clouds outward into space.  As the temperature dropped the upper atmosphere would become more dense and drop downward, upwelling more of the hotter gas closer to the surface which would radiate more heat.  Once this convective cycle was started perhaps only a relatively small amount of energy would be necessary to sustain it.  Modeling this technique would require a high speed centrifuge filled with gas with the temperature and composition of Venus.  At high G the gas would stratify to resemble on a small scale the conditions in the Venusian atmosphere.

en.wikipedia.org/wiki/Laser_cooling

What a facinating idea, could you provide some sort of energy budget?
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Re: Sun Shade concepts for Venus
« Reply #132 on: 03/01/2012 06:48 AM »

Read the link, I don't think that would work. One method only work with some elements. One of the big problems is the amount of energy needed to run all the lasers needed.

With all the wind on the surface, we should be able to use that to generate power. Separate the CO2 from the atmosphere and jet it at high velocity out of the atmosphere. With some of the CO2 leaving at escape velocity, removing heat and CO2. The problem with this idea is that we need CO2 for plant growth.
 

Great! How about an energy budget for accelerating most of 4*10^19 kg of CO2 to Venus escape velocity, and compare it to the amount of energy you can get from Venusian wind turbines, also, what method were you proposing to accelerate the CO2 to that velocity? I've no idea how we'd do it from the surface of the Earth.
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #133 on: 03/01/2012 04:04 PM »

What a facinating idea, could you provide some sort of energy budget?

Sorry.  I don't even know if this idea will work let alone what amount of energy would be required.  That's what mathematical and physical modeling by qualified scientists is about.  Like any speculative megaproject you can be sure that the energy budget will be huge.  The way to evaluate any megaproject is to determine if the theoretical energy required is less than that required by crudely hitting it with a club, or nuke, or comet AND if the result is what you expect or just a broken mess.

What I do know is that CO2 in the Venusian atmosphere has lots of heat energy.  CO2 can be stimulated to give off energy in CO2 lasers.  Laser cooling is a proven technique with many variations.  Can it or something like it be applied to a planetary atmosphere? That's beyond my ability to determine.

I did a variation on the MHD experiment described in the link previously posted.  I used a simple homopolar motor (disk neodymium magnet attached to a sharp nail and free spinning on the tip of an alligator clip as the - pole) in the salt and pepper water filled dish.  A loop of copper strip was placed around inner edge if the dish the to insure a radially uniform electric field and attached to the + pole.  An 11 volt 300 mA DC power supply was used.  Sure enough the magnet spun around in the water and the water spun in the opposite direction proving a definite momentum exchange between the two.

WARNING-If you do this experiment remember that explosive hydrogen gas will be generated!  Ventilate the area, Keep away from flames and wear safety glasses.  The salt water solution will turn green indicating a toxic copper chloride (?) solution.  Handle with caution and dispose of properly. AND your shiny magnet will lose its finish. Safety is your responsibility.

I'm still not sure if a magnetic field of the proper orientation and strength can be induced in a created Venusian planetary ring by electric current as I described.  I am sure that magnetic eddies will be formed by current flow but if they will combine to create a strong enough magnetic flux to accelerate the Venusian air to escape velocity is beyond my limited resources to determine.   


Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #134 on: 03/01/2012 06:31 PM »

Read the link, I don't think that would work. One method only work with some elements. One of the big problems is the amount of energy needed to run all the lasers needed.

With all the wind on the surface, we should be able to use that to generate power. Separate the CO2 from the atmosphere and jet it at high velocity out of the atmosphere. With some of the CO2 leaving at escape velocity, removing heat and CO2. The problem with this idea is that we need CO2 for plant growth.
 

Great! How about an energy budget for accelerating most of 4*10^19 kg of CO2 to Venus escape velocity, and compare it to the amount of energy you can get from Venusian wind turbines, also, what method were you proposing to accelerate the CO2 to that velocity? I've no idea how we'd do it from the surface of the Earth.
I should had say we might be able to-

On Earth we use pumps to force water up throw a fountain into the air. So I was thinking of shooting liquid CO2 up into the Venus air at high pressure. It would take a long time to remove that amount of CO2. I do not know how much energy it would take. First we would need to compress and cool the gaseous CO2 into liquid CO2. Then we need to know the gravity and air losses as the liquid CO2 was shooting throw the air to space. Plus a lot of the liquid CO2 would vaporize into gas, expanding and absorbing heat from the surrounding air. Only a small amount would make it past the outer atmosphere to escape the gravity pull of Venus. For Earth I believe escape velocity is around 25,000mph so the liquid CO2 would have to leave the nozzle of the pump at a far greater speed. In to days world of tech we probable could not make such a pump.

The other idea would be to make dry ice large enough that some of it would make it through the atmosphere to escape velocity before it absorbed heat and turned back into gas. Could an air cannon be made with enough power to throw a given mass to escape velocity throw that think an atmosphere?

It more likely be better to just take the CO2 and make O2, carbon blocks, and combine a lot of the excess O2 with elements from the Venus surface to reduce to Venus atmosphere. A lot of time and energy from the Sun and thermal heat from the air.
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Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #135 on: 03/03/2012 04:54 PM »
  Another  idea to remove a large amount of atmosphere and lessen the density of Venuses  atmosphere may be by way of a sort of nuclear depth charging,from space.

 A canister, say carrying  three Hydrogen bombs, entered into the Venusians upper atmosphere, each bomb released at various altitudes. The first bomb floats by balloon for a short time, the second deploys a parachute, the third aloud to free fall deeper into the cloud tops. Then detonated.
  Energy of the nuclear explosion would be directed in the desired direction. The  resulting massive  rising fireball would draw in and raise the cooler surrounding air and suck it up. The second and eventually the third detonations would accelerate the air further. ejecting volumes of atmosphere and any radiation to escape velocity and off planet.

  Multiple continuous bombardments over several years may be enough to lower the pressure on the surface.
 Materials for the bombs could be found and collected from asteroids or the moon and possibly launched from these locations.

 Please note the first detonation is well understood from the 1950/60s atmospheric tests in earths atmosphere.
Second and third detonations of what might happpen is pure speculation.
« Last Edit: 03/03/2012 05:28 PM by Da5id »

Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #136 on: 03/03/2012 07:29 PM »
[img]
What a facinating idea, could you provide some sort of energy budget?

Have a little time so I'll just add to the comments.  Although I can't provide a definite energy budget it may come out of the energy budget for electricity used in spinning up Venus as I described previously.  If the ion cannon electron beam were modulated in a rectified full or half wave pattern at the precise frequency to stimulate the CO2 in the air to a higher energy state which then will release accumulated energy in a population inversion similar to what occurs in a laser then cooling may occur over time.  Of course any energy used for this purpose would be lost to the momentum exchange effort and would have to be factored into the terraforming energy budget.  You don't get something for nothing. ;)

Speaking of that, a word about raw materials.  An ion cannon and the attendant solar panel is going to be a big hunk of machinery.  Where to get the construction material?  3554 Amun is an M-type Aten Venus crossing asteroid with a length of 2.5 km which may fit the bill.  There are others as well.  They are largely nickel/iron with massive deposits of silver, gold, platinum, iridium, in short the stuff necessary for building a solar powered ion cannon.  The precious metals alone could pay for the construction effort.  Once constructed the ion cannon can be used as a thruster to get it anywhere in the solar system.

We know Venus is bone dry. Without water any terraforming effort will be useless.  While others have suggested comets and kruiper belt objects, they're either too small or too far away.  May I suggest Saturns moon Phoebe?  Estimates are that the 200 km diameter moon is 50% frozen volatiles, mostly water.  If transported to a flat cooler Venusian surface it would create a uniform global ocean 30 feet deep.  But Venus is not flat so the depth of the shallow sea would be greater, say about the depth of Lake Erie. Great for biological productivity since it will all be within the reach of sunlight.  Phoebe is the farthest major moon from Saturn and orbits retrograde in an eccentric orbit.  That means pushing it out of Saturns orbit is not too (relatively) difficult and the retrograde orbit means a fast drop to the inner solar system where a reverse gravity swingby of Mars, Venus, or Mercury could kill velocity and get it to do an atmosphere grazing encounter to create the initial ring.  Afterwords (if it survives the encounter) it can be parked at one of the Lagrange points until later when it can be used to fill the seas.

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #137 on: 03/03/2012 07:35 PM »
From Da5id:

Quote
Another  idea to remove a large amount of atmosphere and lessen the density of Venuses  atmosphere may be by way of a sort of nuclear depth charging,from space.

I think you have seriously underestimated the amount of energy required to eject gas from Venus's atmosphere. Likewise, you seem to think that nuclear warheads are some kind of source of almost infinite energy.

Now I freely admit that I have made no attempt to calculate how much energy would be required to remove 90% of the atmosphere. It will be very large indeed. I think nuclear warheads are puny for this task: even if it worked (which I seriously doubt) it would take centuries to achieve.
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Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #138 on: 03/03/2012 07:37 PM »
@ Nyar:

Liked the use of "relatively" in your post!  :)
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #139 on: 03/03/2012 08:10 PM »
@ Nyar:

Liked the use of "relatively" in your post!  :)

Yeah! :D  I fully admit that these are enormous projects for a far future.  They're not going to provide us with an escape from our current problems here.  If they are done at all they will be done as visionary efforts to EXPAND the possibilities of life in the universe not as an escape from a dying planet.  They will occur AFTER we have stopped killing ourselves and our planet and have created a peaceful productive life affirming global civilization HERE!

"Before you and go out and play, you have to clean up your room."
Someones Mother
« Last Edit: 03/03/2012 08:11 PM by nyar »

Offline Da5id

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Re: Sun Shade concepts for Venus
« Reply #140 on: 03/03/2012 09:20 PM »


Quote
I think nuclear warheads are puny for this task.

I agree, I was thinking more on the scale of hundreds of times bigger than the Tsar Bomba.

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #141 on: 03/03/2012 09:51 PM »

I agree, I was thinking more on the scale of hundreds of times bigger than the Tsar Bomba.

Indeed.

Maybe the title of the thread should be changed to "Terraforming Venus." Sun shades haven't been mentioned too much recently.
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #142 on: 03/04/2012 12:38 AM »


Quote
I think nuclear warheads are puny for this task.

I agree, I was thinking more on the scale of hundreds of times bigger than the Tsar Bomba.

100 = 10^2

Tsar Bomba = 2.1x10^17 Joules

100 Tsar Bomba = 2.1x10^19 Joules

Influent sunlight striking Venus = 2.5x10^22 Joules/day (ref-energy conversion based on LegendCJS 174/300 petawatt earth/venus ratio)

To remove the gravitationally-bound atmosphere to Sun/Venus L1/L2, where it enters heliocentric orbit and disperses rapidly, Ei = 2.5*10^28 joules are required Ref-http://www.rfreitas.com/Astro/TerraformSRS1983.htm

2*10^29 joules of energy are needed to "spin up" Venus.' ref-LegendCJS -to one day/day

But spinning up Venus to a 15 day/night cycle in 97 (corrected) years only requires approx 8.8*10^26 joules ref-nyar

Please note the magnitude differences.  A useful reference is the chart on the link provided below.

http://en.wikipedia.org/wiki/Orders_of_magnitude_%28energy%29



« Last Edit: 03/04/2012 12:46 AM by nyar »

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #143 on: 03/04/2012 01:15 PM »
Thanks for doing that calculation. I was too lazy to do it. I knew that the power of even the most powerful nuclear weapon was magnitudes below what was required to remove a substantial part of the Venusian atmosphere (assuming the mechanism suggested would even work.) And I don't know if thermonuclear explosives can be arbitrarily scaled up to any yield.

The obvious point comes back again and again, the amount of energy needed to radically alter the environment of Venus is so large that it is quite beyond our current civilisation.
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Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #144 on: 03/04/2012 03:34 PM »
Thanks for doing that calculation. I was too lazy to do it. I knew that the power of even the most powerful nuclear weapon was magnitudes below what was required to remove a substantial part of the Venusian atmosphere (assuming the mechanism suggested would even work.) And I don't know if thermonuclear explosives can be arbitrarily scaled up to any yield.

The obvious point comes back again and again, the amount of energy needed to radically alter the environment of Venus is so large that it is quite beyond our current civilisation.

You're welcome.  :)  Bombs can be scaled up considerably but only by adding a third stage to the process.  The bomb essentially becomes a fast breeder reactor with a shell of U-238 being converted to fissionable material.  It's messy and generates lots of radioactive fallout.  Anything big enough to blow away any significant percentage of Venusian atmosphere would probably take more uranium than is present in the entire solar system and would leave Venus a shattered radioactive jumble unsuitable for human use for tens of thousands of years. Perhaps forever.  Clubbing a problem like this won't work.  You can't use a radioactive bomb to 'blow' away radioactive fallout!

Speaking of energy, after inspecting my last post I now realize I made a mistake.  The 8.8*10^26 joules I estimated to spin up Venus to a 15 day will be inadequate to remove enough of the atmosphere to go from the current 90 Bar to a more liveable 10 Bar (147 psi) atmosphere.

To do that you need  2.5*10^28 Joules x ((90-10)/90) = 2.2*10^28 joules.  This gives you two choices.

1- At the stated energy budget wait for 2.2*10^28/2.5*10^22/365 = 2,400 years for the process to complete.

OR

2- Increase the energy budget by a factor of 2.2*10^28/8.8*10^26 = 25.  Simply increasing the diameter of your solar power cell by a factor of 5 should keep you on your 97 year schedule.

Obviously you can do tradeoffs between these two extremes.

The upside is that day cycle will be shortened to 3 earth days. ;D

If we're gonna sling that type of energy around we'd be better off on expending it to repair our own world and turn it into paradise.  8)

Offline douglas100

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Re: Sun Shade concepts for Venus
« Reply #145 on: 03/04/2012 04:42 PM »

If we're gonna sling that type of energy around we'd be better off on expending it to repair our own world and turn it into paradise.  8)

+1
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Offline A_M_Swallow

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Re: Sun Shade concepts for Venus
« Reply #146 on: 03/04/2012 05:22 PM »
We can simulate a 24 hour day by closing the curtains and switching lights on, even in greenhouses.

Can we devise a micro-organism that can survive in Venus's atmosphere with a shiny skin that reflects the sun light back?  The ability to convert CO2 into a solid object such as carbon would be nice.
« Last Edit: 03/04/2012 10:21 PM by A_M_Swallow »

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #147 on: 03/04/2012 07:45 PM »
How about we just stick with Sun Shade concepts for Venus to artificially create a 24 hour day, and freezing out the CO2?
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Offline A_M_Swallow

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Re: Sun Shade concepts for Venus
« Reply #148 on: 03/04/2012 10:22 PM »
How about we just stick with Sun Shade concepts for Venus to artificially create a 24 hour day, and freezing out the CO2?

My sun shade is nearer the surface than yours.

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #149 on: 03/05/2012 06:47 AM »
We can simulate a 24 hour day by closing the curtains and switching lights on, even in greenhouses.

Can we devise a micro-organism that can survive in Venus's atmosphere with a shiny skin that reflects the sun light back?  The ability to convert CO2 into a solid object such as carbon would be nice.
As I said earlier: "Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue."

People keep coming up with the suggestion that all we need is some micro-organism that floats around in the atmosphere of Venus and ka-pow! Problem solved, well, nature hasn't solved that one on this planet, I doubt solving it in the Venusian atmosphere would be easier.
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
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Offline A_M_Swallow

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Re: Sun Shade concepts for Venus
« Reply #150 on: 03/05/2012 07:18 AM »
We can simulate a 24 hour day by closing the curtains and switching lights on, even in greenhouses.

Can we devise a micro-organism that can survive in Venus's atmosphere with a shiny skin that reflects the sun light back?  The ability to convert CO2 into a solid object such as carbon would be nice.
As I said earlier: "Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue."

People keep coming up with the suggestion that all we need is some micro-organism that floats around in the atmosphere of Venus and ka-pow! Problem solved, well, nature hasn't solved that one on this planet, I doubt solving it in the Venusian atmosphere would be easier.


There are plenty of things floating around in the Earth's oceans.  The density of Venus' atmosphere at the surface is 65 kg/m³ (6.5% that of water).  So something may be able to float.

Offline QuantumG

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Re: Sun Shade concepts for Venus
« Reply #151 on: 03/05/2012 07:35 AM »
As I said earlier: "Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue."

Umm.. you are aware that all sorts of bacteria live in the sky, right? Including incredibly high altitudes.


Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #152 on: 03/05/2012 08:58 AM »
There are plenty of things floating around in the Earth's oceans.  The density of Venus' atmosphere at the surface is 65 kg/m³ (6.5% that of water).  So something may be able to float.

At the surface? Nothing alive.

As I said earlier: "Algae have had hundreds of millions of years to colonize the atmosphere of Earth but the sky is still blue."

Umm.. you are aware that all sorts of bacteria live in the sky, right? Including incredibly high altitudes.


From what I've found most of the microbes in the atmosphere are plant pathogens, and simply use the atmosphere as a route between plants.
 http://www.livescience.com/2333-earth-clouds-alive-bacteria.html
 I don't know of any evidence that there are any micro-organisms that live airborne lives independent of the Earths surface, and of course there's a huge difference between an organism surviving, and it surviving and serving a purpose. Crops need to be tended and fertilized, weeds don't. So maybe it's possible to engineer an organism that, with a continual supply of nutrient top dressing onto Venus might perform a useful task, suddenly the simple idea of using atmospheric microbes got a lot more complex. If I recall correctly Carl Sagan looked at using microbes to fix carbon in Venuses atmosphere, but it was determined that the fixed carbon would combine with the O2 released as it fell through Venuses super hot lower atmosphere.
« Last Edit: 03/05/2012 09:00 AM by Andrew_W »
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Offline Solman

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Re: Sun Shade concepts for Venus
« Reply #153 on: 03/05/2012 01:54 PM »
 An organism could be designed with an oxygen (lighter than CO2) filled balloon like bladder to float above the surface and above the level at which temps are too high for survival, but upon its death it would presumably fall and be decompose in the heat of the lower atmosphere.
 It might be possible to have the bladder be made of material which will be able to contain the oxygen after the creature's death - maybe something like the shells of diatoms. In this case the bladder would remain above the level at which heat would decompose it. The high density of Venus's atmosphere would certainly help since the bladder could be more like a float than a balloon I suppose.
 That said, an artificial version could be made that would float in the atmosphere and use solar energy to make copies of itself out of the atmosphere's CO2. I imagine a thin diamond bladder filled with O2 liberated in the breakdown of CO2 into carbon for the diamond bladder.
 Alternately factories floating very high in the atmosphere above the sulphuric acid clouds for more sun could make diamond filled bladders filled with O2 and drop them into the lower atmosphere where they would float.
 If the bladders were covered with velcro like surfaces; they would stick together and form floating islands. Eventually the whole atmosphere at the level they float could be covered forming a new surface that as it grew thicker could support plants.

Steve
 

Offline Solman

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Re: Sun Shade concepts for Venus
« Reply #154 on: 03/05/2012 02:05 PM »
 More on topic - I've wondered if solar sail/sunshades in orbit around Venus should actually reflect sunlight onto a particular area of the atmosphere as they transited the night side of Venus. This would presumably create an updraft that would raise hot lower atmosphere to a high altitude where it would cool.
 The question is whether the heat added to create the updraft would be less than the resulting cooling. If it is then the shades would do double duty in blocking sunlight on the day side and updraft cooling of the atmosphere on the night side.

Steve

Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #155 on: 03/05/2012 02:25 PM »
This is from another site.  It provides a view on an issue that is missed, namely the fact that the Venusian air is not the only thing that is hot.

'Ray Wright on February 6, 2012 8:26 am

    Prompted by an article I saw in a science magazine about cooling Venus, about 30 years ago, I collaborated with a colleague of mine to work out how long it would take the surface layer of rock on Venus to cool down to 20 deg C, if one could remove the Venusian greenhouse effect at a stroke. The result was not encouraging — about 1 million years. The original article proposed seeding the Venusian atmosphere with algae, to absorb the carbon dioxide, but water is required too, and the Venusian atmosphere is too dry, so you would need to crash an ocean’s worth of water into Venus, using Oort Cloud or Kuyper Belt objects, to bring back all the water needed for a terrestrial environment. That would not be unimaginably impossible, but there’s little one can do to improve the cooling rate, given that rock has the thermal conductivity that it has. Even the original article about using algae estimated that 20,000 years would be needed for the surface to become habitable, but that left out the cooling rate problem. It’s a pity, but we’ll have to forget about terraforming Venus without magic. There’s no reason why we couldn’t have manned station in Venus orbit and even habitation platforms floating high in the atmosphere, though.'

Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #156 on: 03/05/2012 05:06 PM »
Here's the thread you quote from:
http://lifeboat.com/blog/2012/02/the-runaway-greenhouse-reversal-cooling-venus

It's a pity Ray Wright hasn't replied to Tom Kerwick's questions, It'd be interesting to know what his definition of "the surface layer of rock on Venus" is, as he points out "given that rock has the thermal conductivity that it has" it takes a long time for heat at depth to get to the surface, and that's why you don't need to wait for the top km of rock to cool, just the top couple of meters.
 
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #157 on: 03/05/2012 06:04 PM »
Use the solar sails to reflect more Sun light on Venus to heat it up more to were some of the molecules will reach escape velocity ( concentrate the light on one area ). Once some of the atmosphere is removed the cool it by blocking the Sun with the solar sails.

Other idea
Solar sails to block the Sun light , CO2 will cool to liquid and or solid. Once it drops to the surface it would absorb the heat from the Venus surface, boil and head up to high altitude to be cool again by radiating the heat to space. Cycle continues till surface is about the some temperature as the CO2. Pressure should be low enough on the high hills to land machines to convert the solid and or liquid CO2. Plant life could start in green houses.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #158 on: 03/05/2012 06:24 PM »
Use the solar sails to reflect more Sun light on Venus to heat it up more to were some of the molecules will reach escape velocity ( concentrate the light on one area ). Once some of the atmosphere is removed the cool it by blocking the Sun with the solar sails.

Other idea
Solar sails to block the Sun light , CO2 will cool to liquid and or solid. Once it drops to the surface it would absorb the heat from the Venus surface, boil and head up to high altitude to be cool again by radiating the heat to space. Cycle continues till surface is about the some temperature as the CO2. Pressure should be low enough on the high hills to land machines to convert the solid and or liquid CO2. Plant life could start in green houses.

I had been thinking in terms of the introduced water cycling through the crust and atmosphere accelerating the cooling of the crust, but you make a very good point about the CO2 performing that function during the cooling phase .
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #159 on: 03/05/2012 06:46 PM »
Use the solar sails to reflect more Sun light on Venus to heat it up more to were some of the molecules will reach escape velocity ( concentrate the light on one area ). Once some of the atmosphere is removed the cool it by blocking the Sun with the solar sails.

Other idea
Solar sails to block the Sun light , CO2 will cool to liquid and or solid. Once it drops to the surface it would absorb the heat from the Venus surface, boil and head up to high altitude to be cool again by radiating the heat to space. Cycle continues till surface is about the some temperature as the CO2. Pressure should be low enough on the high hills to land machines to convert the solid and or liquid CO2. Plant life could start in green houses.

I had been thinking in terms of the introduced water cycling through the crust and atmosphere accelerating the cooling of the crust, but you make a very good point about the CO2 performing that function during the cooling phase .
I got the idea from how some satellites are cooled.

Cooling is not our big problem. It is the high winds that there would be if the planet does not rotate fast enough around it's axes. If one side gets to big a temperature difference that the other side then high winds will happen ( not good for colony ).

I believe we will need to find a way to use the Sun's energy to speed up the planets axial rotation.

There is probably hydrogen under the surface of Venus. Would need to look at the exhaust of the volcanoes to see if the let out hydrogen and or hydrogen compounds. The is at least some hydrogen and water in the Venus atmosphere. 
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Re: Sun Shade concepts for Venus
« Reply #160 on: 03/05/2012 07:20 PM »
My approach is to use the momentum of Kuiper belt objects to stop the planets rotation with respect to the Sun, freeze out the CO2 in one big ice cap on the center of the dark side, and use shades and mirrors to create a single time zone over the rest of the planet. The tropical region would be at the center of the Sun facing side, the polar region at the center of the dark side, temperate zone on the terminator, so as on Earth you get a temperature gradient from one to the other; on Earth its about 100C over 10,000km (equator to pole), on Venus maybe 200C over 20,000km (Sun center to dark center). The terminator would in effect see two suns, the real one, and the reflected Sun from the mirrors at the Venus - Sun L2 point, both Suns always low in the sky, both seen for about half the 24 hour day as the L1 shades open and close.
« Last Edit: 03/06/2012 02:14 PM by Andrew_W »
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Offline Solman

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Re: Sun Shade concepts for Venus
« Reply #161 on: 03/06/2012 01:04 PM »
My approach is to use the momentum of Kuiper belt objects to stop the planets rotation with respect to the Sun, freeze out the CO2 in one big ice cap on the center of the dark side, and use shades and mirrors to create a single time zone over the rest of the planet. The tropical region would be at the center of the Sun facing side, the polar region at the center of the dark side, temperate zone on the terminator, so as on Earth you get a temperature gradient from one to the other; on Earth its about 100C over 10,000km (equator to pole), on Venus maybe 200C over 20,000km (Sun center to dark center). The terminator would in effect see two suns, the real one, and the reflected Sun from the mirrors at the Venus - Sun L2 point, both Suns always low in the sky, both seen for about half the 24 hour day as the L1 shades open and close.

 Wouldn't the thick atmosphere prevent the formation of a CO2 ice cap at the center of the dark side?  I would think that winds in an atmosphere with about 1/15th the density of water could transport quite a bit of heat.
 Even if you blocked the sun entirely over the sunward side of the planet the heat from the surface would keep things too warm for a long time wouldn't it?
 I realize the idea I mentioned above is pretty off-the-wall, but there seem to be advantages to creating a new surface for the planet far above the current surface - most importantly the diamond balloons would provide insulation from the dense atmosphere below.
 Also the new surface would only require that a relatively small portion of the atmosphere's CO2 be converted into diamond and oxygen. The balloons would be very thin skinned and even if the new surface is dozens of balloons thick the total thickness would amount to only a few centimeters if spread evenly across the entire surface of Venus.
 The new surface would presumably still have a thick atmosphere above it depending upon the size of the individual balloons - larger ones would be lighter and float higher. I think you could design for several atmospheres without compromising the ability of plants on this new surface to survive. Alternately the balloons could be made larger and float at the one atmosphere level.
 Perhaps the new surface could use electric motor driven propellers by the millions to actually rotate around the planet in 24 hours. Over time this might start the planet itself rotating in the opposite direction.
 I suppose one atmosphere, reasonable temperatures and a 24 hour day could be achieved (in almost 1 g) although the atmosphere wouldn't be breathable, there might be acid rain, and the surface couldn't support concentrated loads so no tall buildings.

Steve

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Re: Sun Shade concepts for Venus
« Reply #162 on: 03/06/2012 08:28 PM »
Sorry Steve, sometimes I'm a bit lazy or rushed with my comments.

The Sun shade is a prerequisite to everything else, Stopping the planets rotation is just an idea I like because with the substantial mass of large oceans hitting the planet stopping its rotation becomes theoretically possible, you're right that without a much thinner atmosphere the night side wouldn't be significantly cooler than the day side (it isn't even now with Venuses 116 day long (~2800 hour long) solar day). Also, because the quantity of CO2 being dealt with is so large, you'd get a dry ice cap 7km deep over 10% of the planets surface, so it might be prudent to not be reliant permanently on the sun shade to keep it in the dark.

The aspect of this strategy that I have most doubts about is the effect of such a large mass on the crust, obviously it's going to sink considerably under such a weight, the ice cap will in effect create its own kilometers deep crater, and those changes, along with the heat already in the planets crust are going to create some thermal issues under the ice cap.

Edit: I found a wiki reference that states: "Venus's crust appears to be 50 kilometres (31 mi) in thickness, and composed of silicate rocks." http://en.wikipedia.org/wiki/Geology_of_Venus
Which I think is encouraging for the huge CO2 ice cap idea.
« Last Edit: 03/07/2012 06:50 AM by Andrew_W »
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Re: Sun Shade concepts for Venus
« Reply #163 on: 03/06/2012 10:06 PM »
Here's the thread you quote from:
http://lifeboat.com/blog/2012/02/the-runaway-greenhouse-reversal-cooling-venus

It's a pity Ray Wright hasn't replied to Tom Kerwick's questions, It'd be interesting to know what his definition of "the surface layer of rock on Venus" is, as he points out "given that rock has the thermal conductivity that it has" it takes a long time for heat at depth to get to the surface, and that's why you don't need to wait for the top km of rock to cool, just the top couple of meters.
 

I hate to read long posts, so I apologize for this one. I made a bunch of simplifying assumptions and calculate that with a sun shade in place it will take less than 30 years to cool Venus from the current 460 degrees-C to 15 degrees-C.  Better assumptions and better models would give more accurate answers but here is a start. If you read further, then look for order of magnitude errors because if it really would only take around 30 years to cool Venus, then this idea deserves a closer look.

Venus is a terrestrial planet and volcanic, so it has a crust, a mantle and a liquid core.  Ignore that and treat the top two meters of crust as being perfectly insulated from the rest of the planet.  Now, block all sunlight. How long will it take for the temperature  of the  top two meters to cool to 15 degrees-C?

The solar intensity at Venus is 2600 W/sq.-m on the sunny half the planet so the black body radiation from Venus must maintain equilibrium temperature of 460 degrees-C. The radius of Venus is 6.05 E6 meters so the total solar radiation impinging the planet and hence the total black body radiation is 2.99 E17 Watts.

The surface area of Venus is 4.60 E14 square meters so the volume of the top two meters is 9.2 E14 cubic meters. The mean density of Venus is 5204 kg/cubic-m but the density of the top two meters  would be volcanic rock, more like Basalt, ~3000 kg/cubic-m.  That gives the mass  of the top two meters as 2.76 E18 kg.

Venus is very volcanic so assume that the top two meters are Lava, and Lava has a specific heat capacity of 0.84 kJ/kg-K.  (As does Basalt rock.)That gives the heat capacity of the top two meters as 2.32 E18 kJ/K.  We need to lower the temperature 445K for it to be 15 degrees Celsius. That requires the removal of 1.03 E21 kJ of energy by black body radiation. That is, 1.03 E24 Joules.

Total black body radiation was calculated above as 2.99 E17 Watts. That equals   1.08 E21 joule/hour.  So shade Venus and you will have a livable temperature in 40 days, about 6 weeks.  Does anyone believe that? Of course not. For one thing, the black body radiation will decrease as the temperature of Venus decreases so it will take longer for the temperature to drop from 20 to 15 degrees-C than it will take for it to drop from 460 to 455 degrees-C. The above ignores that fact but 15 degrees-C is 288 K so there will still be significant black body radiation at that temperature. Anyway...

Ok, so the atmosphere would still be pretty hot, 460 degrees-C at the surface. If someone can figure out the heat energy content and temperature distribution of the Venusian atmosphere they could calculate the time needed for it to cool, too. Then it is a matter of figuring out the equilibrium temperature distribution of the crust to maintain 15 degrees-C.

Taking a swag at the task of cooling the atmosphere, the mass of the atmosphere of Venus is 4.80 E20 kg, its 96% carbon dioxide and the specific heat of carbon dioxide ranges from about 0.83 to 1.15 kJ/kg-K over the temperature range of interest. Call it 1 kJ/kg-K for this guess. That means we need to radiate 4.80 E20 kJ/K . To drop 445 degrees we need to radiate 2.14 E23 kJ, or 2.14 E26 Joules.  That will take about 22 years assuming none of the atmosphere is cooler than 460 degrees-C. Some of it will be but can't guess how much. Of course a lower starting temperature means less time to cool so 22 years is worst case. (Except that the cooler it gets, the slower it cools, same as above.)

After Venus cools to the correct temperature distribution, and leaving the sun shade in place, put a "sun mirror" or mirrors in a high orbit, in continuous sunshine.  The sun mirrors would be controlled to provide a 24 hour day/night cycle and sized to provide  the correct amount of heat energy to maintain  the new equilibrium  temperature distribution and average surface temperature of 15 degrees-C.

When the temperature gets low enough to work in, the conditions are better to remove and replace or modify the atmosphere.  Sow grass, plant trees and water them.

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Re: Sun Shade concepts for Venus
« Reply #164 on: 03/07/2012 04:18 AM »

The solar intensity at Venus is 2600 W/sq.-m on the sunny half the planet so the black body radiation from Venus must maintain equilibrium temperature of 460 degrees-C. The radius of Venus is 6.05 E6 meters so the total solar radiation impinging the planet and hence the total black body radiation is 2.99 E17 Watts.

Venus is very volcanic so assume that the top two meters are Lava, and Lava has a specific heat capacity of 0.84 kJ/kg-K.  (As does Basalt rock.)That gives the heat capacity of the top two meters as 2.32 E18 kJ/K.  We need to lower the temperature 445K for it to be 15 degrees Celsius. That requires the removal of 1.03 E21 kJ of energy by black body radiation. That is, 1.03 E24 Joules.

Total black body radiation was calculated above as 2.99 E17 Watts. That equals   1.08 E21 joule/hour.  So shade Venus and you will have a livable temperature in 40 days, about 6 weeks.  Does anyone believe that? Of course not. For one thing, the black body radiation will decrease as the temperature of Venus decreases so it will take longer for the temperature to drop from 20 to 15 degrees-C than it will take for it to drop from 460 to 455 degrees-C. The above ignores that fact but 15 degrees-C is 288 K so there will still be significant black body radiation at that temperature. Anyway...

Taking a swag at the task of cooling the atmosphere, the mass of the atmosphere of Venus is 4.80 E20 kg, its 96% carbon dioxide and the specific heat of carbon dioxide ranges from about 0.83 to 1.15 kJ/kg-K over the temperature range of interest. Call it 1 kJ/kg-K for this guess. That means we need to radiate 4.80 E20 kJ/K . To drop 445 degrees we need to radiate 2.14 E23 kJ, or 2.14 E26 Joules.  That will take about 22 years assuming none of the atmosphere is cooler than 460 degrees-C. Some of it will be but can't guess how much. Of course a lower starting temperature means less time to cool so 22 years is worst case. (Except that the cooler it gets, the slower it cools, same as above.)

Thank you for your work in calculating heat capacities and estimated cooling rates.  It is important to look at the numbers rather than simply making assertions.  However I must disagree with your estimated cooling rate of 22 years.  I concur with your estimated heat removal requirement for the top 2 meters of surface ( 1.03 E24 Joules) and the air (2.14 E26 Joules).  However when I add this up and divide by 22 years I get 2.68 E22 Joules/day which is very close to the daily radiant energy on the lit surface of Venus (2.99 E17 watts x 24 hours x 3600 seconds = 2.58 E22 joules/day).  But that isn't possible since Venus reflects approx 80% of incident sunlight.  For the planet to be in thermal equilibrium the amount of energy radiating away must equal the energy absorbed.  If Venus could radiate heat at that rate it would have long ago cooled off.  I think you have neglected the absorptive qualities of the thick infrared absorbing atmosphere and the cloud layer which both combine to trap a good deal of heat and slow its migration to the upper atmosphere where it can be radiated into space.  I think when you factor the insulating qualities of the the atmosphere you'll find that it will take far longer to cool off the air and first 2 meters of surface than you think.

And no I don't think something that massive is going to collapse with a change of a few degrees at the top of the cloud layer.  As the energy is lost to space the cloud layer will simply drop in altitude effectively slowing heat transfer right to the end. 
« Last Edit: 03/07/2012 04:28 AM by nyar »

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Re: Sun Shade concepts for Venus
« Reply #165 on: 03/07/2012 12:38 PM »
There is a band in the Venusian atmosphere with the right temperature for living.  I'm not sure what elevation this is calculated (or measured?) to be at. 

Regardless, here's another solution:  Set up a gigantic fresnel lens in space akin to this idea: http://www.langorigami.com/science/technology/eyeglass/eyeglass.php

But make it sufficiently large that its focal point can vapourize rock through the atmosphere of Venus.  Use it to carve out extremely deep holes into the surface (perhaps an entire hemisphere or two of the planet).  The deep basin would hold most of the planets atmosphere, leaving the relatively thin high peaks within the habitable zone elsewhere.  Perhaps it would look like an exxagerated equitorial rind (like Iapetus but to Venus scale). 

Yes the vapourized rock would re-deposit itself, but if a lot of that occurred in places other than the deep basin(s), then all the better (the mountain peaks might even grow higher faster because they are cooler which would concentrate the re-deposition and increase their speed of growth relative to the residually hotter basins). 

Then parts of the planet you could stand on solid ground with atmospheric pressures and temperatures that are manageable. 

From the top of these peaks (if desired), diamond towers 100 km tall (built from atmospheric carbon) could form the base of bean-poles to space.  If the planet were slowed to never have a day-night cycle, the space base could be on the dark (shadowed) side, and always at the gravitational point behind the planet.   

The bean-poles could be used to transport carbon to space (reducing the atmosphere to make the rest of the planet more habitable) while providing the material to make the diamond rings which would refract a certain portion of sunlight completely away from Venus.  Initially someone could just circulate the gases to giant radiators (made from Venusian metals perhaps) in space which would cool the surface faster. 
« Last Edit: 03/07/2012 12:43 PM by go4mars »
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Re: Sun Shade concepts for Venus
« Reply #166 on: 03/07/2012 02:01 PM »

The solar intensity at Venus is 2600 W/sq.-m on the sunny half the planet so the black body radiation from Venus must maintain equilibrium temperature of 460 degrees-C. The radius of Venus is 6.05 E6 meters so the total solar radiation impinging the planet and hence the total black body radiation is 2.99 E17 Watts.

Venus is very volcanic so assume that the top two meters are Lava, and Lava has a specific heat capacity of 0.84 kJ/kg-K.  (As does Basalt rock.)That gives the heat capacity of the top two meters as 2.32 E18 kJ/K.  We need to lower the temperature 445K for it to be 15 degrees Celsius. That requires the removal of 1.03 E21 kJ of energy by black body radiation. That is, 1.03 E24 Joules.

Total black body radiation was calculated above as 2.99 E17 Watts. That equals   1.08 E21 joule/hour.  So shade Venus and you will have a livable temperature in 40 days, about 6 weeks.  Does anyone believe that? Of course not. For one thing, the black body radiation will decrease as the temperature of Venus decreases so it will take longer for the temperature to drop from 20 to 15 degrees-C than it will take for it to drop from 460 to 455 degrees-C. The above ignores that fact but 15 degrees-C is 288 K so there will still be significant black body radiation at that temperature. Anyway...

Taking a swag at the task of cooling the atmosphere, the mass of the atmosphere of Venus is 4.80 E20 kg, its 96% carbon dioxide and the specific heat of carbon dioxide ranges from about 0.83 to 1.15 kJ/kg-K over the temperature range of interest. Call it 1 kJ/kg-K for this guess. That means we need to radiate 4.80 E20 kJ/K . To drop 445 degrees we need to radiate 2.14 E23 kJ, or 2.14 E26 Joules.  That will take about 22 years assuming none of the atmosphere is cooler than 460 degrees-C. Some of it will be but can't guess how much. Of course a lower starting temperature means less time to cool so 22 years is worst case. (Except that the cooler it gets, the slower it cools, same as above.)

Thank you for your work in calculating heat capacities and estimated cooling rates.  It is important to look at the numbers rather than simply making assertions.  However I must disagree with your estimated cooling rate of 22 years.  I concur with your estimated heat removal requirement for the top 2 meters of surface ( 1.03 E24 Joules) and the air (2.14 E26 Joules).  However when I add this up and divide by 22 years I get 2.68 E22 Joules/day which is very close to the daily radiant energy on the lit surface of Venus (2.99 E17 watts x 24 hours x 3600 seconds = 2.58 E22 joules/day).  But that isn't possible since Venus reflects approx 80% of incident sunlight.  For the planet to be in thermal equilibrium the amount of energy radiating away must equal the energy absorbed.  If Venus could radiate heat at that rate it would have long ago cooled off.  I think you have neglected the absorptive qualities of the thick infrared absorbing atmosphere and the cloud layer which both combine to trap a good deal of heat and slow its migration to the upper atmosphere where it can be radiated into space.  I think when you factor the insulating qualities of the the atmosphere you'll find that it will take far longer to cool off the air and first 2 meters of surface than you think.

And no I don't think something that massive is going to collapse with a change of a few degrees at the top of the cloud layer.  As the energy is lost to space the cloud layer will simply drop in altitude effectively slowing heat transfer right to the end. 

Ok, good. The 80% reflection of the upper cloud layer - that is a large factor. It will result in a factor of 5 increase in the cooling time of sun shaded Venus. One hundred ten years to cool down is still an astonishingly short time.

Quote
I think you have neglected the absorptive qualities of the thick infrared absorbing atmosphere and the cloud layer which both combine to trap a good deal of heat and slow its migration to the upper atmosphere where it can be radiated into space.


No, these factors map into the heat balance of the planet and are inherent in the heat absorbed and re-radiated. Otherwise the current temperature of Venus would not be constant.
« Last Edit: 03/07/2012 02:03 PM by aero »
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Offline RanulfC

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Re: Sun Shade concepts for Venus
« Reply #167 on: 03/07/2012 08:38 PM »
There is a band in the Venusian atmosphere with the right temperature for living.  I'm not sure what elevation this is calculated (or measured?) to be at.
@ 50km above mean surface level. Pressure is @ 1atm, and temp an average of 100F more or less.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030022668_2003025525.pdf

http://www.universetoday.com/15570/colonizing-venus-with-floating-cities/

It helps greatly that normal Earth atmosphere (Nit/Oxy) is a lifting gas with almost as much lift per cu/meter as Helium :)

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Re: Sun Shade concepts for Venus
« Reply #168 on: 03/07/2012 11:21 PM »

Ok, good. The 80% reflection of the upper cloud layer - that is a large factor. It will result in a factor of 5 increase in the cooling time of sun shaded Venus. One hundred ten years to cool down is still an astonishingly short time.

One hundred ten years is still a long time for a commercial proposition, especially when you add on the time for the other processes to complete the terraforming of the planet.

I wonder if the rate of heat loss could somehow be accelerated, if radiating from lower in the atmosphere could be facilitated by removing some of the atmospheric constituents that absorb shorter IR wavelengths perhaps the rate of heat loss could be considerably increased.

Maybe introducing calcium carbonate to react with the SO2 to form Calcium sulfite (CaSO3) (melting point 600C) would disperse the cloud layer? though I don't know where all that lime would come from, I don't imagine there's a lot floating around in space.

Edit: Might be better to start with calcium hydroxide.
« Last Edit: 03/07/2012 11:31 PM by Andrew_W »
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Re: Sun Shade concepts for Venus
« Reply #169 on: 03/07/2012 11:36 PM »

Ok, good. The 80% reflection of the upper cloud layer - that is a large factor. It will result in a factor of 5 increase in the cooling time of sun shaded Venus. One hundred ten years to cool down is still an astonishingly short time.

No, these factors map into the heat balance of the planet and are inherent in the heat absorbed and re-radiated. Otherwise the current temperature of Venus would not be constant.

Yes it is an astonishingly short time.  Although the Emission per m^2 I've seen is 530 watts rather than the 650 watts you've come up with that's still within the ballpark of estimates like this. Good job.  I had thought you were using the emissivity of the surface which is approx 30 times higher but now I see you were using the atmospheric emissivity which is correct.  I can't help but feel that we're missing something but the math seems to show a long but not unreasonable cooling rate.  The Stefan–Boltzmann law states that the power emitted per unit area of the surface of a black body is directly proportional to the fourth power of its absolute temperature and that will certainly slow things down rapidly as the temperature of the atmosphere drops, but I've been too long away from calculus to determine by how much.  Obviously for all practical purposes it isn't one million years, though it still isnt going to happen fast enough to serve as a dumping ground for our exponentiating population either. ;)     

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Re: Sun Shade concepts for Venus
« Reply #170 on: 03/08/2012 03:57 AM »
There is a band in the Venusian atmosphere with the right temperature for living.  I'm not sure what elevation this is calculated (or measured?) to be at.
@ 50km above mean surface level. Pressure is @ 1atm, and temp an average of 100F more or less.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030022668_2003025525.pdf

http://www.universetoday.com/15570/colonizing-venus-with-floating-cities/

It helps greatly that normal Earth atmosphere (Nit/Oxy) is a lifting gas with almost as much lift per cu/meter as Helium :)

Randy

True.  Here's the data and a few speculative pictures

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Re: Sun Shade concepts for Venus
« Reply #171 on: 03/08/2012 04:24 AM »

One hundred ten years is still a long time for a commercial proposition, especially when you add on the time for the other processes to complete the terraforming of the planet.

I wonder if the rate of heat loss could somehow be accelerated, if radiating from lower in the atmosphere could be facilitated by removing some of the atmospheric constituents that absorb shorter IR wavelengths perhaps the rate of heat loss could be considerably increased.


I still believe that the best way is to avoid crude scoops and bombs and asteroid bombardment and do the job electronically, by using high voltage positive and negative ion beams to turn Venus into a homopolar motor literally spinning the atmosphere away while speeding up the planet in the opposite direction.  The turbulance induced in the atmosphere will expose a great deal of the surface air to black body radiation.  Even if the air doesn't leave permanently more radiative effect will occur as the air is sucked into the ring increasing the radiative surface area.  All the equipment will be space based and therefore avoids contact with the hot corrosive atmosphere and the stresses of the Venusian gravity well.  The only thing touching the surface will be the beams themselves, the invisible electron beam hitting the pole and the glowing positive heavy ion beam hitting the perimeter of the created counter-rotating ring completing the circuit and neutralizing the accelerated ionized atmospheric particles before they escape into space at escape velocity.  There is still a question about the arrangement's capacity to sustain its own magnetic field and the power consumption will naturally be enormous, but darn,...it would be beautiful! :o   

Offline QuantumG

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Re: Sun Shade concepts for Venus
« Reply #172 on: 03/08/2012 04:29 AM »
I remember reading something similar in a Stephen Baxter book. Of course, his planet engineers were using Venus as a dynamo, not a motor. I wonder if he invented it or borrowed it from somewhere.
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Re: Sun Shade concepts for Venus
« Reply #173 on: 03/08/2012 07:07 AM »
Reading up, I see that the sulphuric acid clouds of Venus are a result of a photochemical reaction, sunlight splits an oxygen atom from CO2 to form CO + O, this O atom combines with SO2 to form SO3, the SO3 reacts with H2O to form H2SO4, so the Venusian clouds would I assume reduce in size simply with the introduction of a sunshade? And without those clouds the rate at which heat energy would radiate upwards to the top of the atmosphere would increase?

http://en.wikipedia.org/wiki/File:Venusatmosphere.svg

And:
http://en.wikipedia.org/wiki/Sulfuric_acid#Reactions_with_non-metals

Quote
Sulfuric acid is produced in the upper atmosphere of Venus by the Sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapor. Ultraviolet photons of wavelengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen. Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venusian atmosphere, the result is sulfur trioxide, which can combine with water vapor, another trace component of Venus's atmosphere, to yield sulfuric acid. In the upper, cooler portions of Venus's atmosphere, sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above. The main cloud layer extends from 45–70 km above the planet's surface, with thinner hazes extending as low as 30 km and as high as 90 km above the surface. The permanent Venusian clouds produce a concentrated acid rain, as the clouds in the atmosphere of Earth produce water rain.

The atmosphere exhibits a sulfuric acid cycle. As sulfuric acid rain droplets fall down through the hotter layers of the atmosphere's temperature gradient, they are heated up and release water vapor, becoming more and more concentrated. When they reach temperatures above 300 °C, sulfuric acid begins to decompose into sulfur trioxide and water, both in the gas phase. Sulfur trioxide is highly reactive and dissociates into sulfur dioxide and atomic oxygen, which oxidizes traces of carbon monoxide to form carbon dioxide. Sulfur dioxide and water vapor rise on convection currents from the mid-level atmospheric layers to higher altitudes, where they will be transformed again into sulfuric acid, and the cycle repeats.
« Last Edit: 03/08/2012 07:47 AM by Andrew_W »
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Re: Sun Shade concepts for Venus
« Reply #174 on: 03/12/2012 04:06 PM »

Ok, good. The 80% reflection of the upper cloud layer - that is a large factor. It will result in a factor of 5 increase in the cooling time of sun shaded Venus. One hundred ten years to cool down is still an astonishingly short time.

No, these factors map into the heat balance of the planet and are inherent in the heat absorbed and re-radiated. Otherwise the current temperature of Venus would not be constant.

Yes it is an astonishingly short time.  Although the Emission per m^2 I've seen is 530 watts rather than the 650 watts you've come up with that's still within the ballpark of estimates like this. Good job.  I had thought you were using the emissivity of the surface which is approx 30 times higher but now I see you were using the atmospheric emissivity which is correct.  I can't help but feel that we're missing something but the math seems to show a long but not unreasonable cooling rate.  The Stefan–Boltzmann law states that the power emitted per unit area of the surface of a black body is directly proportional to the fourth power of its absolute temperature and that will certainly slow things down rapidly as the temperature of the atmosphere drops, but I've been too long away from calculus to determine by how much.  Obviously for all practical purposes it isn't one million years, though it still isnt going to happen fast enough to serve as a dumping ground for our exponentiating population either. ;)     

I found the problem.  See the attached link or it doesn't work I've attached a doc version.  The calculation is very simple and straightforward.

http://bartonpaullevenson.com/Albedos.html

The problem seems to be the calculation of the 'Effective Temperature" of Venus.  Using the correct effective temperature of Venus gives an equilibrium energy flux in and out of Venus of 163.2 W/m^2 instead of your 650 W/m^2.  That expands the cooling time frame to 650/163.2 x 110 = 438 years.  And that's without the asymptotic drop in cooling rate that will occur as the temperature drops.  I'm afraid that even with 100 % solar shade the near term prospect for getting Venus to a livable temperature is dim.

Offline nyar

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Re: Sun Shade concepts for Venus
« Reply #175 on: 03/13/2012 07:16 PM »
Reading up, I see that the sulphuric acid clouds of Venus are a result of a photochemical reaction, sunlight splits an oxygen atom from CO2 to form CO + O, this O atom combines with SO2 to form SO3, the SO3 reacts with H2O to form H2SO4, so the Venusian clouds would I assume reduce in size simply with the introduction of a sunshade? And without those clouds the rate at which heat energy would radiate upwards to the top of the atmosphere would increase?

It might but how much is a big question.  The clouds do retain some of the heat but the thick carbon dioxide atmosphere retains a great deal more. Carbon dioxide is transparent to visible light but in the infrared frequency it is opaque. I.e.: You couldn't see the surface at infrared frequencies even if the clouds were gone.  And conversely the infrared radiation at the surface is absorbed by the air immediately above it.  You'd have to initiate some powerful turbulence in the atmosphere to get the hot air at the surface up to the upper atmosphere where radiative cooling is more effective.  :-\ 

Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #176 on: 03/13/2012 07:29 PM »
Reading up, I see that the sulphuric acid clouds of Venus are a result of a photochemical reaction, sunlight splits an oxygen atom from CO2 to form CO + O, this O atom combines with SO2 to form SO3, the SO3 reacts with H2O to form H2SO4, so the Venusian clouds would I assume reduce in size simply with the introduction of a sunshade? And without those clouds the rate at which heat energy would radiate upwards to the top of the atmosphere would increase?

It might but how much is a big question.  The clouds do retain some of the heat but the thick carbon dioxide atmosphere retains a great deal more. Carbon dioxide is transparent to visible light but in the infrared frequency it is opaque. I.e.: You couldn't see the surface at infrared frequencies even if the clouds were gone.  And conversely the infrared radiation at the surface is absorbed by the air immediately above it.  You'd have to initiate some powerful turbulence in the atmosphere to get the hot air at the surface up to the upper atmosphere where radiative cooling is more effective.  :-\ 
Reconfigure the land to cause the air to go up. Make hills that would force the air up when blowing. Either that or use some sort of wind powered blower to force the hot air up ( might be able to use some of the thermal energy too.
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Offline go4mars

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Re: Sun Shade concepts for Venus
« Reply #177 on: 03/13/2012 07:38 PM »
Reconfigure the land to cause the air to go up. Make hills that would force the air up when blowing. Either that or use some sort of wind powered blower to force the hot air up ( might be able to use some of the thermal energy too.
  http://en.wikipedia.org/wiki/Solar_updraft_tower

Like one of these? 
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #178 on: 03/14/2012 01:30 AM »
Reconfigure the land to cause the air to go up. Make hills that would force the air up when blowing. Either that or use some sort of wind powered blower to force the hot air up ( might be able to use some of the thermal energy too.
  http://en.wikipedia.org/wiki/Solar_updraft_tower

Like one of these? 
Something like that but not using sunlight only the high winds and thermal energy in the atmosphere.

If the top of the tower were sealed and had a valve, and the pipes laid on the ground connected to the tower had valves at the other ends. The system could then be brought to a lower pressure ( pump out some of the gas ). The gas inside would then be at a lower pressure and temperature than that out side the pipes on the ground. They could then absorb the heat from the outside rising the temperature and pressure inside the pipes. Inside the tower the pressure  would be greater than the outside pressure at the top of the tower. Open the valve at the top of the tower releasing pressure and sending the hot gas to a higher and colder altitude and some of the heat from below with it. When the inside pressure gets close to the  outside pressure at the top of the tower then the valve would close again. When more gas is needed the valves at the ends of the pipes on the ground would open and let in more air close to the ground.

Tower and pipes would need a lot of surface area compared to inside volume to absorb heat. Made of material that is super conductive ( or as close as possible ) and resist corrosion and other times of damage.
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #179 on: 03/14/2012 03:58 AM »
Reading up, I see that the sulphuric acid clouds of Venus are a result of a photochemical reaction, sunlight splits an oxygen atom from CO2 to form CO + O, this O atom combines with SO2 to form SO3, the SO3 reacts with H2O to form H2SO4, so the Venusian clouds would I assume reduce in size simply with the introduction of a sunshade? And without those clouds the rate at which heat energy would radiate upwards to the top of the atmosphere would increase?



It might but how much is a big question.  The clouds do retain some of the heat but the thick carbon dioxide atmosphere retains a great deal more. Carbon dioxide is transparent to visible light but in the infrared frequency it is opaque. I.e.: You couldn't see the surface at infrared frequencies even if the clouds were gone.  And conversely the infrared radiation at the surface is absorbed by the air immediately above it.  You'd have to initiate some powerful turbulence in the atmosphere to get the hot air at the surface up to the upper atmosphere where radiative cooling is more effective.  :-\ 

CO2 like any other gas has an absorption spectrum, that absorption spectrum does not cover all IR wavelengths, so you're incorrect in asserting that the surface is not visible in the IR because of CO2, though there is a problem that the combination of H2SO4 clouds, CO2, CO, water vapor, SO2 etc between them do a pretty good job of covering the whole IR spectrum. If we could chip away at that list until holes were made in that absorption spectrum the rate of surface cooling could certainly be accelerated.

The reason that CH4 is about 20 times as powerful CO2 as a GH gas on Earth is because it covers some of those holes other gases don't.

The idea of pushing warm air up probably wouldn't work, as gases rise in an atmosphere they cool, and that's why Venus, Earth and other planets can have stable atmospheres with cold air on top, lift surface air to altitude and it'll be cooler than the air at altitude when it gets there (the exceptions to the rule are (1)hurricanes etc in which the surface temperature is so far above the temperature at altitude that the temperature range exceeds the stable lapse rate and (2)the convection that happens off the warmed surface that's pretty much limited to the troposphere).
« Last Edit: 03/14/2012 04:22 AM by Andrew_W »
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Offline RanulfC

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Re: Sun Shade concepts for Venus
« Reply #180 on: 03/14/2012 01:06 PM »
Andrew_W:
I understand the idea to be artificial "upwellings" of surface air. Really tough to do considering the wind-shear difference between the surface and (say) 50km, but the idea would be to pump the hot surface air to high altitude before it could appreciably cool off. Once there it gives off it's heat rapidly and then begins to sink back towards the surface.

I got that right folks?

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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #181 on: 03/14/2012 02:39 PM »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #182 on: 03/15/2012 12:07 AM »
Radical Terraforming Methods
http://forum.nasaspaceflight.com/index.php?topic=25012.0

Splinter threads for terraforming Venus and removing some of it's CO2.
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #183 on: 03/16/2012 12:12 AM »
Once the Sun shade blocks the incoming heat and the atmosphere cools,
How deep would the body of liquid CO2 be or if it's dry ice be? ( for this just assume Venus surface is flat no valleys or hills )
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Offline Andrew_W

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Re: Sun Shade concepts for Venus
« Reply #184 on: 03/16/2012 12:30 AM »
Dry ice is about 1.5 times as dense as water, at 90 atmospheres pressure  on a planet with 0.9 g surface gravity you've got about 1000 tonnes of atmosphere over each square meter. So Venus has enough CO2 to give a layer of dry ice 660 meters thick over the whole planet, pile it up in one place to have maybe 6600 meters thick over 10% of the planet.
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Offline RocketmanUS

Re: Sun Shade concepts for Venus
« Reply #185 on: 03/16/2012 12:43 AM »
Dry ice is about 1.5 times as dense as water, at 90 atmospheres pressure  on a planet with 0.9 g surface gravity you've got about 1000 tonnes of atmosphere over each square meter. So Venus has enough CO2 to give a layer of dry ice 660 meters thick over the whole planet, pile it up in one place to have maybe 6600 meters thick over 10% of the planet.
That means the high areas of the surface could be exposed for landing and exploration.

We would still have a nitrogen atmosphere. 3.5% is nitrogen, now it would be the main compound for the atmosphere.
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Offline yawan

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Re: Sun Shade concepts for Venus
« Reply #186 on: 08/02/2017 01:47 AM »
I'm making very rough calculations so please correct me if I'm wrong, but here is an idea.
Coat graphane with a thin layer of reflective metal.  Release it in a spiral in around L1.  Make sure the gravity and solar pressure are around equal.  Release it close to the SUN.  If you can get the calculations done right you can block out the sun for a while.  If you can keep it up long enough you can cool the planet past 3 and 4 um absorption frequencies to the equilibrium around 40 degrees Celsius and 8 atm of pressure 3 atm nitogen and 5 atm co2.  The rest of CO2 would form an ocean, and sulfuric acid would reach with the rock and form water.  You could still live at around 10-15 km in floating cities, but robotic mining would be a lot easier, and you would have water.

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Re: Sun Shade concepts for Venus
« Reply #187 on: 08/02/2017 07:25 AM »
I'm making very rough calculations so please correct me if I'm wrong, but here is an idea.
Coat graphane with a thin layer of reflective metal.  Release it in a spiral in around L1.  Make sure the gravity and solar pressure are around equal.  Release it close to the SUN.  If you can get the calculations done right you can block out the sun for a while.  If you can keep it up long enough you can cool the planet past 3 and 4 um absorption frequencies to the equilibrium around 40 degrees Celsius and 8 atm of pressure 3 atm nitogen and 5 atm co2.  The rest of CO2 would form an ocean, and sulfuric acid would reach with the rock and form water.  You could still live at around 10-15 km in floating cities, but robotic mining would be a lot easier, and you would have water.

I hope you've done the calculation for negative 40 degrees C, for the CO2 to become liquid. Any remaining water will float as ice on top of the CO2 ocean. Probably none, as it will have been transformed into bicarbonates during the cooling of the planet. Sulfuric acid will no longer be a problem, although the SO2 will take longer to react with rock surfaces.

Keeping the habitat comfortably warm, after stripping away most of the energy sources, is going to be a challenge.

Offline yawan

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Re: Sun Shade concepts for Venus
« Reply #188 on: 08/02/2017 03:36 PM »
No my pressure was off for calculating the pressure at which CO2 becomes liquid.
Cooling Venus temporarily past its 4um equilibrium would cool it to around 10 um average frequency.
https://scholarsandrogues.files.wordpress.com/2011/05/venus-co2-spectrum-lg.jpg
That would equate to around 40 degrees Celsius.  It would keep the pressure, but all the electronics would work on the surface, which would make mining plausible.
Some reactions would form bicarbonates.
Those bicarbonates would create sodium and magnesium bicarbonates which react with sulfuric acid to form water... so we'd end up with oceans soon enough.
And there are plenty of reactions that would create water straight away.
I'm not saying all the sulfuric acid would become water but most of it would.

Offline stefan r

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Re: Sun Shade concepts for Venus
« Reply #189 on: 08/07/2017 02:00 PM »
No my pressure was off for calculating the pressure at which CO2 becomes liquid.
Cooling Venus temporarily past its 4um equilibrium would cool it to around 10 um average frequency.
https://scholarsandrogues.files.wordpress.com/2011/05/venus-co2-spectrum-lg.jpg
That would equate to around 40 degrees Celsius.  It would keep the pressure, but all the electronics would work on the surface, which would make mining plausible.
Some reactions would form bicarbonates.
Those bicarbonates would create sodium and magnesium bicarbonates which react with sulfuric acid to form water... so we'd end up with oceans soon enough.
And there are plenty of reactions that would create water straight away.
I'm not saying all the sulfuric acid would become water but most of it would.

Mercury has a lower gravity and a lot of metal.  Mercury mines could out compete Venus.  The inner solar system will have a strong demand for carbon and hydrogen.  If your motive for colonizing Venus is strip mining then the atmosphere is the commodity not the obstacle.

Oxygen balloons float in a CO2 atmosphere. 

Tethers can be used to change the velocity of spacecraft.  If Venus manufactures graphene or fullerene tethers then cargo transports could use Venus's gravity for an orbital assist and take a tether with them too. 

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