Cooling Venus using Lunar dust

Antius · 2015-08-14 04:50:18

I have toyed with a new idea to aid the terraforming of Venus. The idea is to deposit large quantities of lunar regolith dust, asteroid dust or pulverised waste material into orbit around Venus in order to reduce insolation reaching the planet, thus allowing it to cool.

Background:

In my opinion, the key to the viability of any terraforming solution is that it provides good returns for any future investor (in terms of access to land, habitability of land, access to materials, resources, etc.) in a timescale that is reasonably interesting to them (decades or centuries, i.e. their lifetime or at least their grandchildren’s lifetime). Grand schemes that require importing trillions of tonnes of water from the deep solar system are fun to consider, but unlikely in reality, unless one assumes that a future civilisation is gifted with god-like powers and has no concern about return rates on their investment. If we assume that, then we can achieve virtually anything, but the discussion loses its value as a real world practical suggestion

From this point of view, the immediate goal is not necessarily to create Earth analogue or perfect conditions, but to transform the planet from its present useless state, to one where human beings can at least access the surface and its resources on a reasonable timescale and, hopefully, even establish settlements there. The goal then is to reduce temperatures and pressures to more workable levels.

The key to achieving this is to reduce the insolation reaching the cloud tops, thereby allowing the planet to cool. The ideal solution would be a permanent sunshield, but this this would be a massive structure constructed from refined aluminium, weighing at least several billion tonnes. Whilst the investment required is achievable for a space civilisation, it will be desirable to achieve some reasonable return from the planet before it is made. So the question becomes, is there are cheaper way of blocking out the sun?

One obvious solution is to use some inert material to achieve the same effect. In the inner solar system, the easiest to access material is lunar dust or asteroid regolith. Both materials are extremely fine and have a high ratio of surface area to volume. The surface area of Venus is ~4.5E14m2. Assuming lunar fines with a diameter of 0.001mm are used and are placed in a relatively low orbit, some 4.5E8m2 would be needed, about 1billion tonnes. Sunlight pressure would tend to force the particles into elliptical orbits that intersect the atmosphere, so the dust belt would need to be replenished to maintain its areal density. If the half-life of the particles is 5 years, then ~100 million tonnes of fines would need to be delivered per year.

The economic viability of the concept depends upon how cheaply this can be achieved. It may take 100 years for the surface to cool sufficiently to begin habitation. On this basis, the total cost of the effort would be 100 years x 100million t/yr x delivery cost per tonne. If the delivery cost is $1000/tonne, then the total cost would be $10trillion. If it is 10 times lower, then the cost will decline accordingly. The most obvious choice of material would be whatever low value waste material happens to be most abundant at future high orbit manufacturing sites. Maybe silicon dioxide or alumina dust? Or just plain raw regolith dust?

Let’s say delivery cost is $100/tonne and the investors expect a 1000% return on their total investment after 100 years. This suggests that to justify the effort, the value of Venus after 100 years must be $10 trillion. A population of 1 billion people could therefore ‘buy’ the planet for $10,000 each or could pay perhaps $1000 each every year as a sort of rent. The resulting world would have a land area perhaps half that of Earth, with large liquid CO2 oceans covering the low lying areas of the planet. To maintain the shield, the colonists would need to pay a total of $10billion per year, $10 each per year.

Antius · 2015-08-14 05:58:01

According to Wiki, meteorite dust can persist in the Earth's atmosphere for several months. The Venusian atmosphere is denser, hotter and drier, so it is fair to assume that average residency period will be increased.

With this in mind, it may be more economic to break up small near earth asteroids and simply pound Venus with small fragments which burn up in its atmosphere, rather than attempt any precise orbital insertions of dust. This solves the additional problem of how to deploy the particles on arrival.

As a number of NEOs are Venus crossing, maybe this can be accomplished with minimal delta-V? Simple mass drivers mounted on the surfaces of Venus crossing NEOs could get the job done. A quantity of 500mt per year equates to 16 tonnes per second. Mass drivers mounted on perhaps a dozen or so NEOs with average delta-Vs of perhaps 100m/s would require a power source of 80MW. Easy enough to provide using solar power.

Void · 2015-08-18 21:57:40

Well, I think I will mess with this.

I like the towers notion at the poles, where I have wanted to suppose S02 could be sequestered, to reduce acid rain. This has been mentioned in other threads in recent time of this post.

But now contrary to other notions, I suggest putting super greenhouse gasses into the upper atmosphere of Venus to make it's atmosphere swell up. In addition I would like to not reflect light but absorb it. Perhaps floating Ping-Pong balls filled with N2. Wetted by the H20 clouds (After the acid rain is cured). Fertilized by dust as you suggested, either from space or the surface of Venus.

Turning the surface temperatures to thousands of degrees. Swelling the atmosphere.

Major problem: How to make towers that will stand such temperatures.

Anyway, since the solar wind sweeps atmosphere from Venus, if you swell it up further in the gravity well of Venus, it will sweep even more atmosphere away. To protect H20, perhaps O2 generated on the Ping-Pong balls by algae/cyanobacteria, would allow for an Ozone layer above the water layer.

The real objective would not be so much to deplete the atmosphere of Venus, but to harvest it.

Upper atmosphere manipulated into plasma, might be collected into plasma bubbles and directed to a Mars impact. Ideally Mars with a 2 bar atmosphere would be nice.

Venus itself would still support floating colonies. (The Ping-Pong balls would be too small to cause major damage if they impacted such colonies. Towers at the poles might still be possible.

And a major supercritical CO2 oven at the surface, perhaps refining substances desired.

900 degrees would kill you as much as thousands of degrees anyway.

Far fetched? You bet. Not the greenhouse gasses though, and the swelling atmosphere.

Antius · 2015-08-19 05:26:42

Void wrote:

Well, I think I will mess with this.
I like the towers notion at the poles, where I have wanted to suppose S02 could be sequestered, to reduce acid rain. This has been mentioned in other threads in recent time of this post.
But now contrary to other notions, I suggest putting super greenhouse gasses into the upper atmosphere of Venus to make it's atmosphere swell up. In addition I would like to not reflect light but absorb it. Perhaps floating Ping-Pong balls filled with N2. Wetted by the H20 clouds (After the acid rain is cured). Fertilized by dust as you suggested, either from space or the surface of Venus.
Turning the surface temperatures to thousands of degrees. Swelling the atmosphere.
Major problem: How to make towers that will stand such temperatures.
Anyway, since the solar wind sweeps atmosphere from Venus, if you swell it up further in the gravity well of Venus, it will sweep even more atmosphere away. To protect H20, perhaps O2 generated on the Ping-Pong balls by algae/cyanobacteria, would allow for an Ozone layer above the water layer.
The real objective would not be so much to deplete the atmosphere of Venus, but to harvest it.
Upper atmosphere manipulated into plasma, might be collected into plasma bubbles and directed to a Mars impact. Ideally Mars with a 2 bar atmosphere would be nice.
Venus itself would still support floating colonies. (The Ping-Pong balls would be too small to cause major damage if they impacted such colonies. Towers at the poles might still be possible.
And a major supercritical CO2 oven at the surface, perhaps refining substances desired.
900 degrees would kill you as much as thousands of degrees anyway.
Far fetched? You bet. Not the greenhouse gasses though, and the swelling atmosphere.

You wouldn't need to heat the atmosphere up for this plan to work. Just harvest gases from Venus' ionosphere using a collector in low orbit. A collector would either use a portion of the harvested atmospheric gases as propellant in an ion engine to counter the atmospheric braking effect or would be equipped with an EM drive to maintain orbit. The output would be a big ball of frozen CO2 protected from sunlight by sheets of aluminium. You would then have the problem of how to get it to Mars. An Earth flyby would reduce the propulsive work.

But who would pay for it? Shipping CO2 to Mars is a bit like shipping the proverbial coal to Newcastle.

Storing SO2 would be easier if you could store it as sulphates. This would happen naturally as you cooled the planet down. Acid would rain out onto the surface, reacting with local oxides to produce sulphates. Water would be liberated as a byproduct.

I like the idea of ping-pong balls. The balls could be manufactured from silica gathered from the surface, filled with N2 or CO and coated with trace elements needed for plant growth. Algae would then seed the surfaces. As ping-pong balls fall to the surface, the algae would be baked into char, which could then be sequested. The problem is that there isn't sufficient water in Venus atmosphere to support the algae growth in the first place. Shipping it from elsewhere would be insanely expensive.

As the planet cooled, CO2 within its atmosphere would sequester itself. The crust would contract opening porosities which the liquid CO2 would then fill. It would then react with oxides to form carbonates.

Last edited by Antius (2015-08-19 05:42:38)

Void · 2015-08-19 16:34:28

Your variation is a completely valid solution to your view of what is desired.

My view of what is desired is different, so of course my variation will differ.

I am the guest on this thread, and I request that you do what you can to discuss this in both directions, yours and mine.

My view of Venus is that what is wanted is to find a chink in it's armor sufficient to allow settlements there, but not requiring a large population, at least not at first.

Major terraforming would be a decision that the "Inhabitants" would make later. Perhaps they will instead want to keep their supercritical CO2 oven down below.

So, my emphasis would be on getting the most useful results to make Venus realistically habitible with the least effort.

I am just pulling a number out of the air, but I feel that if 50,000 people lived at each pole (100,000) total, that would still be useful to the human race, in terms of cultural diversity, and also an insurance policy for the greater chances of the continuation of the human race.

So, I look at the things which will be annoying in the zone of Venus which is most habitable.

1) Lack of a surface to walk on. 2) Acid rain which will damage equipment, and burn exposed skin. 3) U.V. light.

Floating cities and towers can help with #1, Towers can maybe help with #2, Ping pong ball slime agriculture can help with #3, and might also provide an important source of feedstock for organic chemistry, and might even provide food.

For instance your habitat might suck in these ping pong balls, and somehow place them in and enclosure where an animal may feed on the algae on their surfaces, and then eject them again.
Of course such animals (Fish?) will need some tolerance of toxins from the outside (CO2), and a method would need to be devised to deliver the ping pong balls to the feeding area with a minimum of intake of such toxins.

I do have an idea for sequestering Sulfur other than SO2. Iron Pyrites. At lower temperatures than the surface it might remain stable. It is not a champion building material, but I am thinking of some process where it would be woven into another material, maybe 3D printed. Perhaps your floating cities could be in part made of Iron Pyrites. (Fools Gold).

Dealing with U.V. will be an issue. To get free oxygen, you have to sequester something. You would need free Oxygen in a significant layer, in order to hope to develop an Ozone layer.

However here, I may have an idea, which is not too far removed from Carl Sagans original idea for terraforming, but it would only be used to a small degree.

If fish eat algae from floating ping pong balls, then the fish waste/Human waste (Humans presumed to eat fish), could be subjected to a hot oven (Not hard on Venus), gassing off the volatiles, and leaving a Carbon rich residue.

https://en.wikipedia.org/wiki/Carbon_fibers

So Carbon fibers as a building material, sequestered to remain un-oxidized for a prolonged period.

Making parts of the cities, and maybe towers as well.

So I want a Venus with water clouds that are not too acid. They don't have to be neutral P.H.
I also want to hope that there is a chance to produce a enhanced volume of free Oxygen, and that that Oxygen will tend to form enriched layer in the upper atmosphere. However wishing might not do the trick. The Oxygen might mix very well, and also with more O2, you might just get interaction between CO2, Oxygen, and U.V. light to produce CO.

But that would not be a total loss, because then your atmospheric engine would then work on Venus, since there would be quantities of CO and O2 mixed into the atmosphere.

In that case, you might need some type of transparent beads, with flotation gasses in them that would float higher than your clouds, and would filter U.V. light out.

Having achieved this then the inhabitants could lay their plans for the next phase of terraforming if any, like a caterpillar preparing to become a butterfly.

Last edited by Void (2015-08-19 16:36:16)

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#1 2015-08-14 04:50:18

Cooling Venus using Lunar dust

#2 2015-08-14 05:58:01

Re: Cooling Venus using Lunar dust

#3 2015-08-18 21:57:40

Re: Cooling Venus using Lunar dust

#4 2015-08-19 05:26:42

Re: Cooling Venus using Lunar dust

#5 2015-08-19 16:34:28

Re: Cooling Venus using Lunar dust

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