Carbon Nanotube Tether

[bratman]

First off we have all heard of the tether into space. How much heat could a pressurized helium filled carbon nanotube chamber take before bursting and would it be possible to make such a device? I want heated gas tube inside and helium filled sectional valved outer wall in order to sustain the weight of the tether. The heated gas inside would be non explosive.

 

I do not know anyplace else to discuss this or I would have tried there first.

[CaptainPanic]

First off, I'm not sure we have all heard of the tether into space. I have heard of ideas of the space elevator. Also, some satellites have been equipped with a tether... so it might be useful to provide some more background, or a link.

 

Second, I'm not sure that the term "pressure" applies when you're talking about carbon nanotubes. These are typically in the order of a few nanometers (hence the name) in width. This means that only a few helium or hydrogen atoms/molecules would fit in there next to each other. The interactions of the helium/hydrogen with the nanotube are probably as frequent as with the other gas molecules... and therefore I am not sure we can even call it a gas inside.

 

But reading your post makes me think that you want a balloon of carbon-fibre... so the gas would be several liters or even m3, in a strengthened structure.

 

If you're in space (no oxygen present), who cares about explosive mixtures? (I mean, you're not using gaseous TNT after all... Hydrogen itself is harmless without oxygen). Are you thinking of putting something in space? Why do you need helium?

 

So, basically, I haven't understood your question.

[insane_alien]

so basically you want to make a carbon nanotube cylinder and inflate it with helium for structural rigidity?

 

i'm not so sure this will work very well compared to the counterbalanced ribbon of nanotubes that most scientists think would be somehwere around feasible.

 

i mean for the first few kilometers, perhaps even tens of kilometers, it should be fine but the pressure required to keep it up will rise roughly exponentially as the pressure at the bottom will be FAR higher than the pressure at the top.

[bratman]

If you can shape carbon nanotubes into a ribbon can you make it into other shapes? It needs to have the strength to be able to make it to space which only carbon nanotubes can do at this point, and the last time a tether was the tether snapped and was only about 30 kilometers long. And not very thick.

 

 

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

Here is your link.

 

quote:

 

the strength required would be twice that of any existing material including graphite, quartz, and diamond.

 

I am wanting to push CO2 to space. Collect it, freeze it and then push it off never to be seen again. And I lied, methane would be another one that is explosive and more contributing to our plight.

 

Perhaps methane could be used to support the tether, as in propulsion 4 tethers supporting a 5th. Once the gases are in space freeze them after that I have not thought of a way to get rid of them other then pitch them. If methane block hit the earth again it would burn on reentry. Not what I am intending, I would like to see them sail off never to be seen again.

 

Explosiveness is an issue because of static electricity produced by the tethers.

 

I just want to have a friendly hypothetical discussion.

 

Correction: and the last time a tether was used the tether snapped and was only about 30 kilometers long. And not very thick.

[Mr Skeptic]

I'm assuming you want to use a coal fired power plant to power your space elevator? Just kidding. If you want to get rid of CO2, the solution is to replace our burning of fossil fuels. If collecting CO2 were easy, storing it on earth but not in the atmosphere would be far easier than sending it into space.

 

If you want to solve global warming with a space elevator, the thing to do is take up a bunch of solar panels.

[SkepticLance]

There is just under 2 billion tonnes of carbon dioxide in the Earth's atmosphere. To remove any appreciable fraction of that immense amount is not feasible.

 

Remember, this gas has real weight, and any pumping of the gas up a space elevator has to lift that large fraction a vast distance. We are talking 38,000 kms to get to the point where it has practically speaking no weight. It has to go even further to get to the point where, when released, it will spin off into space.

[bratman]

Yes gas has weight, I realize this one I did not just fall off of a mullet boat. Carbon dioxide, Methane. I am thinking while recording your replys. Shoving it back into the ground is not a reasonable idea either. Have you looked at the dead zones in the water lately?

 

Another approach..

 

http://www.sandia.gov/news/resources/releases/2007/sunshine.html

 

 

Also methane

http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/05/14/BAGJG6LG3R15.DTL

 

Any gas approaching space would have to be superheated and collected then frozen. Reentry into the atmosphere of frozen CO2 should change it to carbon monoxide and something else I read somewhere but carbon monoxide is not good for us either.

[CaptainPanic]

The production of 1 mole of CO2 gives you 393.5 kJ/mol of energy. 1 mole weighs 44.01 g/mol.

The production of 1 kg of CO2 therefore gives you 8.9 MJ/kg of energy.

 

Now lets see how high you can get something with this energy. I'll assume a constant gravitational acceleration if you don't mind: 9.81 m/s2.

 

E = m*g*h

h = E/(m*g) = 8.9E6/(1*9.81) = 907,000 m. That's 907 km. That's in orbit, not completely gone. Also, the CO2 will only have altitude, but to remain in orbit it also needs speed. Therefore, it will simply fall back straight down again.

 

Therefore, we can conclude that to really shoot 1 kg of CO2 into space, you will need to produce more than 1 kg of CO2 on earth. Hardly sustainable. If you want to utilize any of the energy from the combustion of carbon to CO2, you'll have to settle for shooting the produced CO2 into orbit, lower than 907 km altitude.

 

This means:

1. Eventually the CO2 will fall back. It's not a permanent solution, it is temporary.

2. We will get a ring, just like Saturn. Ours will consist of gaseous and solid CO2, and will be found between about 400 and 900 km altitude. Perhaps it attracts alien tourists?

 

I haven't mentioned methane, because I don't see why you'd shoot methane into space once you got it concentrated. You'd be better off selling it as "methane" or "natural gas" to consumers. They will voluntarily turn it into CO2 for you, and will even give you money for it.

 

And if you plan on wasting sustainable (solar/wind) power on shooting CO2 into space, you'd help the earth more if you just sold the sustainable electricity (so that no CO2 is produced to do that).

[SkepticLance]

To CaptainPanic

 

I agree with you that sending CO2 into space is not a smart move. There are much better ways of dealing with it right here on Earth.

 

However, we should not suggest it cannot be done. A space elevator has to go about 78,000 kms into space anyway to be able to work. The energy to lift things up the elevator, whether by carriage or by pumping, can be done using nuclear power - hence no CO2 emission. If the CO2 was released into space beyond the 35,000 km mark, and especially if released way out at 78,000 km, the centrifugal effect will flick it out into space, and it will never fall back.

[Mr Skeptic]

Yes, but the whole point is that it is totally not worth it. It would be cheaper and better to simply convert the CO2 to C + O2, giving us more oxygen, and pure carbon. Since I expect that carbon will one day become a major building material (it is, after all, what the space elevator would be made of), and it is already the element of choice for living things, we might regret sending it into space. If nothing else, the carbon could be used as backup power in the case of a global disaster. In any case, converting it into carbon and oxygen would be cheaper, and would free up the space elevator for something useful.

[CaptainPanic]

My point is that if you generate 1 kWh of nuclear derived electricity, you have 2 options to use it:

 

1. Put it on the grid for consumers to use it. This means that some dirty coal powered plant should generate 1 kWh less.

2. Use it to bring up a little CO2, which means that the coal powered plant will also have to generate the 1 kWh because consumers will still need it. In addition, the space elevator will not be able to bring up all the CO2 produced by that coal powered plant.

 

This scheme will only be useful if:

1. We have 100% sustainable energy, and a bit more (we have too much clean energy).

2. We really need to remove CO2 from the earth (and storage or conversion into C + O2 is no solution for some weird reason).

 

We should do this only if both criteria are met, and while we can discuss about the 2nd case, the first one most certainly is not happening yet.

 

And even if it could be an energy free transportation:

the centrifugal effect will flick it out into space

...the construction of a space elevator would be a little too costly to lift something silly as CO2. You should realize that in order to make any difference on the earth, the amount of CO2 we remove from earth should be in the same order of magnitude as our production... which happens to be something like nearly 10 billion tons of CO2 per year. That is over 300 tons per second. That's quite a space elevator. But, yes, it is not impossible. It's merely a giant engineering problem challenge. Edited September 11, 2008 by CaptainPanic
adding more arguments to not waste too much time on this idea :D

[iferdinand]

sequestration is the answer

[CaptainPanic]

sequestration is the answer

I don't think so. I think we would have to make carbonates which would totally screw up the pH of the entire planet. All other storages depend on some matrix in which the CO2 will fit, and the costs are just enormous.

 

Normal underground storage is also no option by the way:

The carbon we combust is either from natural gas, crude oil or coal.

For each molecule of natural gas (methane), we produce a molecule of CO2, which we can store in exactly the same gas field as where we found the methane.

 

That will not go for coal and oil. Even if we would be able to use empty oil fields, we can store a maximum of about 440 g/l of carbon: the density of solid CO2 is 1600 g/l, and CO2 consists of 12/44 of carbon (and 32/44 of oxygen).

 

Both coal and gas contain a higher concentration of carbon, so we need more space to store the produced CO2 than we created by extracting the oil and coal.

 

Then we could use other fields too perhaps (empty salt mines or something), but I think that the only place that is proven to be closed off completely from the surface is an empty gas field... Everything else is just dangerous.

 

It will not be possible to store all the CO2.

 

My plan to save the world is simple: clean sustainable energy. Remove the whole CO2 issue altogether. We already have the technology, we only need a little (a lot of) initiative.

[SkepticLance]

Actually, CaptainPainic, we still need quite a lot of technological development to switch to carbon friendly life styles. These are being developed, but the change over will take a few decades.

 

For example : we now have hybrid cars. The first plug-in hybrids will be on the market soon, permitting a car to be run as a pure battery operated vehicle for the normal short trips most of us use cars for. After that comes long range electric cars, and beyond that still comes rapid recharge (10 minutes), long range electric cars.

 

In the mean time, that will not work for trucks and buses for long journeys, and we need to develop fuels for them, such as biofuels and synthetic fuels. That development is also under way.

 

Abundant and non carbon dioxide generating electricity will be required. This need will be met by a range of methods, including new generation nuclear, hot rock geothermal, wind, tide, ocean waves, solar etc. Again, a few decades will be required to develop and build these generating plants.

 

Deforestation needs to be stopped, and a regimen in place to plant two trees for every one that is felled. You may be surprised to know that this is also under way, and the western world is already doing it.

 

New farming methods need to be instituted, and will be. The research into these new agricultural methods is already being done.

 

The thing is : we know what needs to be done, and it is being done. It will not happen overnight, and there is no point rushing into precipitous and stupid measures. The felling of tropical rainforest throughout Indonesia to plant palm oil for biodiesel to supply the EEC is an idiocy we need not repeat.

[npts2020]

The best solution is not to produce carbon dioxide, methane, ozone, etc in the first place. While hybrids and electric cars may help some, you still have to power them with something and you will still kill over 40,000 people a year, have traffic jams, high infrastructure costs, etc. I am in the process of writting extensively about automating Americas road/rail system and powering it with solar and wind energy. Anyone is welcome to check it out and comment at npts2020.blogspot.com.

[bratman]

If you can get the gas up to space intact and form it into some shape once its up there. What would need to be done is to sail it away somehow, launch it or send it flying hopefully towards the sun. You would not want it coming back to earth.

[Mr Skeptic]

Are you sure it wouldn't take less energy to simply separate the carbon from the oxygen and then bury it as coal? Or even just bury it as CO2?

[Tranquility]

As I understand it the planet is able to recover from the increased levels of CO2, but only if we stop adding to the problem. If we had a space elevator surely we could generate the energy we need in orbit, venting any CO2 that is created. The energy could either be beamed down to earth using a high powered laser or sent down a very long super conducting cable attached to the elevator?

 

Alternatively If the CO2 was created in orbit in a controlled environment surely it could be used to grow plants to create a useful biosphere in orbit. Nuclear energy would also be far cleaner when generated in orbit as the largest problem from fission based nuclear energy is the abundant radioactive waste from the coolant and spent fuel rods. The coolant may not be needed to the same degree as the cold vacuum of space would surely help there, and the spent fuel rods can be collected and then sent on one way trips to our sun.

 

I do however agree that this planet has a wonderful ability to recycle the material that makes the planet, if we start sending huge amounts of carbon into space we are reducing the amount we have down here. surely we need to find a better method of recycling the CO2 that is produced.

[insane_alien]

If we had a space elevator surely we could generate the energy we need in orbit, venting any CO2 that is created.

 

1/ why would it create any CO2? surely energy production would be solar in nature else why do it in space?

 

2/ this would cause some worrying mass balance problems. if you are generating significant quantities of CO2 up there then you'll need a few large pipes of oxygen and carbon up there. just means we're going to be losing oxygen and spending a fortune(albeit a smaller fortune than if it were launched on a rocket) transporting mass up the elevator.

 

The energy could either be beamed down to earth using a high powered laser or sent down a very long super conducting cable attached to the elevator?

 

if you have went to the trouble of a space elevator then superconducting cables are the likely choice, microwave beaming for all the unattached power satellites.

 

but this is besides the point, a space elevator could not be accomplished in the near future without massive and total international cooperation and spending. not to mention the resources it would consume during construction would cause deficits in other areas. our industry and economy aren't up to the task yet unless we have a 'build one or face extinction' scenario. we are not yet that deep in fecal matter.

 

Nuclear energy would also be far cleaner when generated in orbit as the largest problem from fission based nuclear energy is the abundant radioactive waste from the coolant and spent fuel rods.

 

no, it'll still produce just as much waste, all it would do is provide a potentially disasterous place to store it. much better we just bury it deep and seal it off. examples are the oklo natural reactor. this thing was dirty as hell and in contact with ground water and so on but it doesn't seem to have destroyed the environment there. where we want to bury the waste is safer than that.

 

The coolant may not be needed to the same degree as the cold vacuum of space would surely help there,

 

more coolant would be needed. space is cold, but exceedingly hard to dump energy into. you'd need MASSIVE radiators and they need to be out of direct sunlight or they won't work very well.

 

and the spent fuel rods can be collected and then sent on one way trips to our sun.

 

now there's a crap idea. do you know how much fuel you can recover from those things? thats like saying we should change the way we extract oil to taking a drop from every barrel send it off for processing and dumping the rest into the sea. reprocessing would be far better.

 

I do however agree that this planet has a wonderful ability to recycle the material that makes the planet, if we start sending huge amounts of carbon into space we are reducing the amount we have down here. surely we need to find a better method of recycling the CO2 that is produced.

 

or we could just switch to non-CO2 producing energy infrastructure. like nuclear. we have plenty of fuel as long as we make breeder reactors (4 years if we don't). not only that but there are also renewables such as wind wave and solar. CO2 sequestering from large plants both power and chemical(it isn't feasible to extract it from the atmosphere, its too low in concentration for that).

 

chucking everyting into space would just create different problems. what we need to do is learn to balance it all. and we can do it in both and environmentally friendly and economically friendly way. the technologies just need a few more years to mature.

[Tranquility]

Wow, thankyou insane alien for your reply. I hadn't thought these things through, was just throwing ideas out. But your science is correct. Think I will limit my responses in future.

[insane_alien]

don't limit your responses, just think them through a bit more.

 

everyone comes up with ideas that seem good but 99.99% they turn out to be crap if you think about them for a bit. it happens to you, it happens to me, it happens to nobel prize winners, everyone.

 

don't limit a thing, just think about things some more and there will be something more interesting to talk about thwere there may not be an obvious right or wrong and a nice good arguement can follow.

 

for instance, the space elevator idea isn't entirely without merit. it would be the perfect launching platform for massive solar arrays that could supply us with energy in the future. and carry us on to be a type I civilisation on the karashdev(i can never spell this name) scale. but its not likely to be used to house nuclear plants. and its a more likely to be a century down the line than soon enough to limit global warming. but there is merit for future environmentally friendly energy production.

[louis wu]

insane_alien

 

Your post 19 was was very well reasoned, however I would have to take issue with the following passage.

 

we could just switch to non-CO2 producing energy infrastructure. like nuclear. we have plenty of fuel as long as we make breeder reactors (4 years if we don't). not only that but there are also renewables such as wind wave and solar. CO2 sequestering from large plants both power and chemical(it isn't feasible to extract it from the atmosphere, its too low in concentration for that).

You are grossly underestimating the uranium reserves.

 

Known uranium reserves contain more energy than all known fossil fuel reserves.

http://wapedia.mobi/en/Uranium_reserves.

This is without considering that prospecting has not taken place in many of the geological areas likely to contain uranium ore. Major finds of uranium ore are likely.

On the other hand extraction of lower grade ores will require more energy to be used in the extraction and produce more nasty mining waste.

 

Use of MOX fuel will improve the bang for the buck in the next generation of nuclear reactors, but as you said FBRs will be needed to keep the world's lights on for more than the next few decades. There is a huge stockpile of ²³⁸U waiting to be turned into burnable fuel. Waste disposal may be a problem as proper storage facilities are lacking, due to lack of political will.

One viable waste disposal method may be subduction into the mantle; the Marianas Trench may be one suitable location.

Adoption of full nuclear fuel cycle could keep the world's base load supplied for centuries while we sort out fusion or space based solar power or build a Ringworld.

[insane_alien]

http://www.scientificamerican.com/article.cfm?id=how-long-will-global-uranium-deposits-last

 

given current usage rate of nuclear fuel without reprocessing or breeding, that source says we have 230 years. but thats only for 5% of global energy. with 100% utilization we have 11.5 years (the 4 year source is using only discovered sources)

 

the breeder reactor and thorium reactors will be absolutely necessary if we need to switch to nuclear. you can't get away from it.

 

the reason it is so low is because only over 99% of the uranium is not fissionable without putting it through a breeder.

 

i'm not grossly underestimating reserves, i'm saying that without breeder technology, offloading a significant portion of power generation onto nuclear would be disasterous and short lived.

 

with breeder reactors and thorium reactors, the fuel would last millenia.

[louis wu]

insane_alien

 

I don't want a bitter disagreement with you as actually I agree with you on the vast majority of your thoughts.

 

The link I provided states explicitly that 'The fission energy contained in the reserves is far greater than all fossil fuels on the earth combined (even including methane clathrates), without even considering the use of fast breeder reactors utilizing byproducts like plutonium.'

That is far more than 4 or 11 years of worldwide use for nuclear power.

 

The authors may have miscalculated, or they may have included reprocessing to MOX fuel and the use of non breeder fast reactors; both of which gain much more energy from the original UO₂.

 

Your Scientific American link may just consider an American perspective. Some American sources seem to consider that American practices are the best and only way. No USA reactor has ever used MOX fuel, whereas many European reactors have done so. Fast reactor studies stopped many years ago in the USA, but continue in France, Japan and Russia.

 

Stating that 99% of Uranium is non fissile is both true and slightly misleading. Natural uranium at 0.71% ²³⁵U can be made to go critical quite happily. The predominant ²³⁸U will produce some interesting fissile isotopes for MOX or use in a fast reactor.

 

Enriched U is used in reactors to obtain criticality with less moderation, and it also enables easier extraction of power from the coolant in a denser core.

[Mr Skeptic]

'The fission energy contained in the reserves is far greater than all fossil fuels on the earth combined (even including methane clathrates), without even considering the use of fast breeder reactors utilizing byproducts like plutonium.'

That is far more than 4 or 11 years of worldwide use for nuclear power.

 

That's slightly misleading. As stated, this includes the energy that will eventually be released by the radioactive waste over thousands of years, much of which will not even be in the reactor or any power plant at the time.