Author Topic: Sun Shade concepts for Venus  (Read 89571 times)

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.
Douglas Clark

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.
Douglas Clark

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
Douglas Clark

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?
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

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.
Wilbur Wright

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.


Human spaceflight is basically just LARPing now.

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 »
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

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.
 
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
Wilbur Wright

Offline RocketmanUS

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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.

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

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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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