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DaveC426913
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I'm looking for good links to stuff on space elevators, particularly for laymen, or even school-age students.
DaveC426913 said:Forgive me Berke. I could not bring myself to think you were asking seriously.
wikipedia.org said:Orbital tethers
This concept, also called an orbital space elevator, geosynchronous orbital tether, or a beanstalk, is a subset of the skyhook concept. Construction would be a vast project: a tether would have to be built of a material that could endure tremendous stress while also being light-weight, cost-effective, and manufacturable in great quantities. Today's materials technology does not quite meet these requirements, although carbon nanotube technology shows promise. A considerable number of other novel engineering problems would also have to be solved to make a space elevator practical. Not all problems regarding feasibility have yet been addressed. Nevertheless, the LiftPort Group believes that the necessary technology might be developed as early as 2008[4] and that by developing the technology, the first space elevator could be operational by 2014.[5][6]
FredGarvin said:Dave,
You do realize that the mere posting of a question will bring every space elevator whack-o on the net in here in no time.
I am implying that the following has a serious crank factor to it. Personally I think that the space elevator will never happen, even if we have thousands of plants turning out carbon nanotubes by the truckloads. However, like most things I am adamant about, I wait to be proven wrong.Ivan Seeking said::rofl: I never realized that this qualifies as subculture, but it probably does!
Are you implicity suggesting that the idea itself is cranky, or just that that it has a crank following?
I knew it had a big following, I'd no idea it was considered by some to be cranky.FredGarvin said:I am implying that the following has a serious crank factor to it.
I call it cranky because of all of the people that have come on this board, it seems that 95% of them think that once we get carbon nanotube production going that it will be a simple matter of hooking them together with a tether and some motors.DaveC426913 said:I knew it had a big following, I'd no idea it was considered by some to be cranky.
FredGarvin said:I am implying that the following has a serious crank factor to it. Personally I think that the space elevator will never happen, even if we have thousands of plants turning out carbon nanotubes by the truckloads. However, like most things I am adamant about, I wait to be proven wrong.
Is that two questions or one...?Ivan Seeking said:Are you implicity suggesting that the idea itself is cranky, or just that that it has a crank following?
As of today, engineering challenges are a distant second to the challenge of producing carbon nanotubes in such quantities. It's like discussing a bridge from New York to London - sure, there are engineering challenges, but the scale is what makes the very idea of building a bridge from New York to London asinine.Ivan Seeking said:But in this case, I recognize that the engineering challenges are daunting - the harmonics and wind shear forces being the ones the most come to mind for me.
russ_watters said:As of today, engineering challenges are a distant second to the challenge of producing carbon nanotubes in such quantities. It's like discussing a bridge from New York to London - sure, there are engineering challenges, but the scale is what makes the very idea of building a bridge from New York to London asinine.
Ivan Seeking said:I tend generally to take the opposite view of things: I expect that it will happen until someone convinces me that it's not possible; and then I may or may not listen. But in this case, I recognize that the engineering challenges are daunting - the harmonics and wind shear forces being the ones the most come to mind for me.
TVP45 said:Nobody would ever insure the construction and the environmental impact hearings would still be going on when the sun went dead.
Ivan Seeking said:How is this any worse than the space program; say a mission to Mars?
You are equating things that are several orders of magnitude different in scale. Ie, this is a much bigger project than a translantic cable - you are off by perhaps 3 order of magnitude. And there has never been a time since wires were invented (much less decades after they were invented) that they could only be produced in microscopic quantities and for thousands of dollars a gram. So production of carbon nanotubes will have to improve by, oh, I dunno, ten orders of magnitude in both cost and scale.Ivan Seeking said:That doesn't seem like a fair analogy to me. I see it as being more akin to the transatlantic cable.
In what way does the scale of this concern you? We know that this is the issue but that can change quickly. It doesn't justify declarations of failure.
[separate post] How is this any worse than the space program; say a mission to Mars?
Fred said "even if". I'm not completely certain what he meant, but my position, if I were willing to let the first "impossible" go, would be "even if" we get past the first 'impossible', there is another one right behind it. But I'm not willing to let the first ''impossible' go.Besides, Fred was assuming that we have production of nanotubes going.
That's silly. Antimatter propulsion is science fiction. We have NO form of antimatter propulsion. We do, on the other hand have the materials for a space elevator, even if the logistics and engineering challenges are fabulously difficult.russ_watters said:So I would say, as a rough guess, that a carbon nanotube space elevator would be around 10^23 times more difficult to do than a translantic cable. It puts it on similar footing with things like anti-matter propulsion.
Correct. And far-out science fiction too. The Enterprise's "impulse engines" are fusion reactors. That, at least, is something that isn't just technobabble-gibberish. Antimatter? It is barely even concievable right now.DaveC426913 said:That's silly. Antimatter propulsion is science fiction. We have NO form of antimatter propulsion.
Not correct. The "challenges" posed by the materials far exceed any scientific/engineering endeavour ever undertaken by mankind. And that comes before the logistics and engineering challenges of building it. We can synthesize anti-matter and we can synthesize carbon nanotubes. And both on about the same scale.We do, on the other hand have the materials for a space elevator, even if the logistics and engineering challenges are fabulously difficult.
I'm not prepared to take those initial numbers for granted.russ_watters said:Lets do a little cost/scale exercise. No one has done it yet, but let's assume that it would be possible sometime in the relatively near future for a manufacturing plant to produce 1 meter of carbon nanotubes per year using a gigawatthour of energy. And let's assume that a million strands would be strong enough to support a space elevator. The cable would stretch to 1.5 times geostationary orbit (60,000 km). (power costs about $.1/kwh)
How many plants and how long would it take to build and how much would it cost?
Well, yeah - they are optimistic. My point is that even with very optimistic assumptions about production, it's still Star Trek level science fiction.DaveC426913 said:I'm not prepared to take those initial numbers for granted.
russ_watters said:You are equating things that are several orders of magnitude different in scale. Ie, this is a much bigger project than a translantic cable - you are off by perhaps 3 order of magnitude. And there has never been a time since wires were invented (much less decades after they were invented) that they could only be produced in microscopic quantities and for thousands of dollars a gram. So production of carbon nanotubes will have to improve by, oh, I dunno, ten orders of magnitude in both cost and scale.
So I would say, as a rough guess, that a carbon nanotube space elevator would be around 10^23 times more difficult to do than a translantic cable. It puts it on similar footing with things like anti-matter propulsion.
In order to start with the assumption that 'anything is possible', like you said you do, you are assuming that we will discover new technology with the absence of any scientific basis for the assumption. Such assumptions are unscientific and wrong. Fred said "even if". I'm not completely certain what he meant, but my position, if I were willing to let the first "impossible" go, would be "even if" we get past the first 'impossible', there is another one right behind it. But I'm not willing to let the first ''impossible' go.
BTW, I'm pretty sure you once suggested that it is best to start out with no assumptions. The 'anything is possible' assumption is the crank assumption that makes this a cranky subject.
Yes, I'm making them up and yes, they most certainly make for a meaningful post if they are educated guesses and illustrate the magnitude of the problem.Integral said:Russ I seriously expect that you are pulling some numbers out of your A$$.
Does making up numbers make this a meaningful post? Perhaps you should stick to generalities.
Well, you are also making big assumptions about the capacity of a factory and the power usage. These look pretty energy intensive to me:FredGarvin said:The only number that really requires estimation is the power required to produce the nanotubes.
Just for argument sake, let's say that a plant could make 1 nanotube the required length to get something into stationary orbit, let's say 1000 km, in 6 months. Let's also say that the power required is no more than a common household usage, let's say 20 kWh/day. Let's also assume that a bundle required for the space elevator requires 1 million individual tubes.
According to my calcs, that would equate to an energy (and only energy) usage of [tex]3.6x10^9 \frac{kWh}{bundle}[/tex] which equates to $360 M/bundle. In terms of the space program, that cost is not too exorbitant. However, does anyone have a handle on the cost for materials and equipment required to produce this stuff? I have no idea there.
However, looking at the time to produce, if there were 1000 factories churning out 1 tube 1000 km in length every 6 months, that still equates to 492 years to produce one bundle.
Like all engineering endeavors, we're already behind schedule.
http://www.azonano.com/details.asp?ArticleID=1108Carbon nanotubes can be manufactured using a variety of methods:
· Laser ablation uses a high-power laser to vaporise a graphite source loaded with a metal catalyst. The carbon in the graphite reforms as predominantly single-wall nanotubes on the metal catalyst particles.
· Arc discharge involves an electrical discharge from a carbon-based electrode in a suitable atmosphere to produce both single and multi-wall tubes of high quality but in low quantities.
· Chemical vapour deposition (CVD) is where a hydrocarbon feedstock is reacted with a suitable metal-based catalyst in a hot furnace to ‘grow’ nanotubes which are subsequently removed from the substrate and catalyst by a simple acid wash.
http://www.fuentek.com/technologies/carbon-nantubes.htm#techdetNASA scientists have developed an SWCNT manufacturing process that does not use a metal catalyst, resulting in simpler, safer, and much less expensive production. Researchers used a helium arc welding process to vaporize an amorphous carbon rod and then form nanotubes by depositing the vapor onto a watercooled carbon cathode. Analysis showed that this process yields bundles, or “ropes,” of single-walled nanotubes at a rate of 2 grams per hour using a single setup.
NASA’s process offers several advantages over metal catalyst production methods. For example, traditional catalytic arc discharge methods produce an “as prepared” sample with a 30% to 50% SWCNT yield at a cost of approximately $100 per gram. NASA’s method increased the SWCNT yield to an average of 70% while significantly reducing the per-gram production cost. Additional research is needed to determine the physical characteristics of NASA’s SWCNTs.
Carbon nanotubes have unique properties that make them incredibly strong and lightweight. They have a tensile strength that is 100 times greater than steel, and they are also very flexible. This makes them a perfect material for constructing a space elevator, which requires a strong and lightweight structure that can reach great heights.
A space elevator is a proposed structure that would allow for transportation between Earth and space without the need for rockets. It consists of a long tether anchored to the Earth's surface and extending into space, with a counterweight at the other end to keep the tether taut. Elevators or climbers would travel along the tether, powered by electricity and using the Earth's rotation to reach space.
Using carbon nanotubes for a space elevator would greatly reduce the weight and cost of the structure. Traditional materials, such as steel, would be too heavy and expensive to construct a space elevator that can reach high enough into space. Carbon nanotubes also have the potential to be mass-produced, making them a more feasible option for such a large-scale project.
One of the main challenges is the production and manufacturing of carbon nanotubes on a large scale. Currently, the production process is still expensive and time-consuming. Another challenge is ensuring the structural integrity and stability of the carbon nanotubes, as they are still a relatively new material and their long-term behavior is not fully understood.
While carbon nanotubes are currently the most promising material for a space elevator, there have been other materials proposed, such as graphene and diamond nanothreads. However, these materials also have their own challenges and limitations. Further research and development is needed to determine the most suitable material for constructing a space elevator.