Space Cloud to Reflect Sunlight?

[Dook]

With the growing threat of global warming, couldn't we launch a series of rockets into space filled with water and have them discharge the water to create clouds in space between the sun and earth?

The water vapor cloud would absorb and deflect some of the heat. It wouldn't have to be very large. We would only need to reduce solar radiation by a small percentage.

 

[Borg]

With the growing threat of global warming, couldn't we launch a series of rockets into space filled with water and have them discharge the water to create clouds in space between the sun and earth?

The water vapor cloud would absorb and deflect some of the heat. It wouldn't have to be very large. We would only need to reduce solar radiation by a small percentage.

The short answer is no.
First, the water would quickly dissipate and second, the cost of putting a pound of anything into space is around $10,000. That's $1 million per 14 gallons of water (~7 pounds per gallon). Third, you would generate even more greenhouse gasses to launch that into space.

 

[Dook]

The water would quickly dissipate into what? To where? At it's smallest form water is still H2O. It wouldn't be a dense cloud of water like clouds on the earth, it would be very thin but that's what you want. We only need to block or deflect a small portion of heat. Also, the water cloud could be diffused in a way that puts it on a slow return trajectory back to the Earth so it would cease to exist in 10 or 20 years or whatever.

The cost of launching five or ten rockets into space is nothing compared to the threat of global warming. NASA's budget is $18 billion a year and they just tested a giant new rocket. What's the point of having NASA if they can't do something to actually help humanity?

Also, rocket fuel is hydrogen and oxygen that is gathered by breaking down water through electrolysis so all it's doing is returning the water to it's previous form. It's not creating any new greenhouse gasses.

If cost was the main factor there wouldn't be a NASA. How much money has NASA generated for the US?

 

[russ_watters]

At low pressure and temperature, water can only exist as a solid or gas, whereas clouds are mostly condensed liquid water. However, a cloud of snow would still work: When released into space, some water would boil off into a diffuse gas and the rest would freeze into thin snow. The problem is, you are vastly underestimating how much water would be required to do anything useful.

So, how much would you need to send up to make it worthwhile? [back of the envelope calcs...] Say you wanted to reduce the incoming radiation by 1%. That would mean covering 300,000 square km, or a square of 564 km on a side. Let's say the equivalent in snowfall depth is 2mm and snow is 1/10th the density of water. That's 64 million cubic meters of water, with a mass of 64 billion kg. At $20,000/kg, that's just over a quadrillion dollars to launch it into space.

...and hopefully once up there it wouldn't dissipate too quickly...

 

[1oldman2]

How much money has NASA generated for the US?

Some things are far more valuable than money, NASA is a gold mine in certain "currencies"

 

[Dook]

Okay, water is too heavy. What about using carbon dioxide gas then?

 

[davenn]

Okay, water is too heavy. What about using carbon dioxide gas then?

anything like a vapour or a gas is just going to disperse and become useless
so what will you use to keep it in place ?

 

[Dook]

Disperse to where? Are you saying that the sunlight will break apart the CO2 into smaller particles? That's not going to happen. That takes higher energy to break apart an atom. At it's smallest form CO2 is still CO2 and CO2 deflects infrared.

A thin vapor is what you want. You don't want a thick impenetrable cloud. You want a very thin cloud that you can build up slowly so you can measure how well it's working.

What will I use to keep it in place? Nothing. We can launch a rocket toward the sun and diffuse the CO2 somewhere midway. The CO2 vapor would be on a slow course toward the sun where it will be gathered in by Venus. Or the solar wind could blow it right back to the Earth but that is going to take years depending on where it's initially placed. That's another thing we would want, it should be temporary until we know exactly the effect it's having.

 

[Borg]

Russ has given you a rough estimate of the costs that show that your ideas cost far exceeds NASA's entire budget for the next 100 years (it doesn't matter whether it's water, CO2 or what). Whatever is used, it will disperse to the point of uselessness very quickly because stuff disperses in space. It's like trying to put out a forest fire with a cup of water - it isn't a viable solution no matter how you apply it.

 

[ebos]

I think another huge problem we have when we "eye-ball" things especially of a gaseous nature like water vapour, etc, is that we imagine in our mind's eye that it is quite light. Gases at our altitudes on Earth and not in space 'displace' a huge amount of atmospheric gases which are already there taking up space. For example, when a large white fluffy cloud rolls into view. It's floating so how much could it weigh? However, when we take into account that our atmosphere already has a substantial amount of weight, then we do the math of displacement, we can quickly see that our fluffy friend probably weighs thousands of tons. And that's not even a big cloud. Those huge thunderheads from which tornadoes spring or a medium sized hurricane (which itself wouldn't even deflect more than a couple of percent) weigh millions and even billions of tons. Even hydrogen, which appears to have NO weight, still has mass. It's just bouyant in our atmosphere because it's pressure is a lot less than our atmospheric pressure especially at STP.
Sorry about not providing any numbers but I just wanted to put a different, and quick, light on the subject.

 

[Borg]

Another thing to consider is that comets have been spraying water in the inner solar system for billions of years. Ask yourself why isn't the inner solar system filled with water?
This article on Gas Dynamics and Kinetics in the vicinity of comets goes into excellent detail about what happens to water in space. For example in section 4.4:

water photodissociation reactions provide the bulk of excess energy for the coma, with the main dissociation branch
H2O + hν → H + OH + Energy
providing most of the energy. Because there is excess energy after overcoming the chemical bond energy on the order of 2 eV for this reaction and the products H and OH must conserve both energy and momentum, so 17/18 of the energy is imparted to the H atom, producing it with an excess velocity of ~17.5 km s–1.

In layman's terms, the sunlight hitting water molecules splits the molecule and sends the remaining parts flying apart faster than a speeding bullet. At those speeds, they will disperse very quickly. And, if you could find a molecule that didn't split, it would still be given a similar boost in speed - again, dispersing very quickly.

 

[Baluncore]

Disperse to where? Are you saying that the sunlight will break apart the CO2 into smaller particles? That's not going to happen. That takes higher energy to break apart an atom. At it's smallest form CO2 is still CO2 and CO2 deflects infrared.

It takes much less energy to disassociate the O=C=O molecule than it does to break apart an atom. There is no shelter from the highest energy particles or UV in space.

A CO2 cloud may start as dry ice, but it will sublime over time. Comets have tails, the CO2 will be blown away by the solar wind. If the CO2 cloud was where it might be useful, between the Sun and the Earth, it will tend to be blown back towards the Earth.

Where will the space cloud be? If it is only between Earth and Sun, then it will have different orbital parameters and so orbit at a different rate. It will need to be continuously replaced as it gradually moves in it's orbit ahead of the Earth.

If the cloud filled a ring in equatorial Earth orbit, a bit like like geostationary satellites but with a faster period then, since the cloud is spread along 360° of an orbit, only a very small percentage would be in productive use at anyone time. The mass of cloud needed to be effective would need to be very high. The dispersion by the solar wind would remain a continuous disruptive process. How would such an orbit effect satellite communications or astronomers?

What about the legal, political or military action by the growers of crops or operators of solar PV panels on the Earth's surface?

 

[russ_watters]

Disperse to where?

Dissipate. Drift off into space.

What will I use to keep it in place? Nothing. We can launch a rocket toward the sun and diffuse the CO2 somewhere midway. The CO2 vapor would be on a slow course
toward the sun where it will be gathered in by Venus. Or the solar wind could blow it right back to the Earth but that is going to take years depending on where it's initially placed. That's another thing we would want, it should be temporary until we know exactly the effect it's having.

The Earth and Venus do not share a line of sight with the sun. So now you are describing a doughnut shaped cloud encompassing the entire region of the solar system between Earth and Venus. You can do the math yourself, but I expect by this point you are talking more mass than the Earth itself.

This is getting rather silly.

 

[1oldman2]

Okay, water is too heavy. What about using carbon dioxide gas then?

"space is big, really big" CO2 in the atmosphere however, that is a big part of the global warming problem to start with, somewhat counter intuitive as a solution.

 

[berkeman]

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