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joe_doufu
Joined: 09 May 2005
Location: Elsewhere
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 Posted: Sun Aug 28, 2005 12:27 am Post subject: |
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| mithridates wrote: |
| And it won't take too long either. |
You mean construction? Or developing the technology? I'm not sure really what goes into building a space elevator. Why don't you tell us more? |
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some waygug-in
Joined: 25 Jan 2003
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| Posted: Sun Aug 28, 2005 3:29 am Post subject: |
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I don't know about the elevator, but here's something interesting about jet fuel.
http://www.wtvf.com/content/news/14060.asp
��It's about someone that really took some fuel that really didn't know what they were getting. If they try to put it in their car, they'll find out real quick it won't run,�� Daniel Taylor said.
The Jet A fuel that was stolen is basically kerosene with an additive, and is worthless to car drivers. But it��s worth about $4,600 to the small airport.
I don't think it would be that difficult to make a bio-fuel that would work in jet engines. The question would be "How much would it cost?" |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Sun Aug 28, 2005 5:24 am Post subject: |
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I'm talking carbon nanotubes, baby!
| Quote: |
The cable must be made of a material with an extremely high tensile strength/density ratio (the limit to which a material can be stretched without irreversibly deforming divided by its density). A space elevator can be made relatively economically if a cable with a density similar to graphite, with a tensile strength of ~65–120 GPa can be produced in bulk at a reasonable price.
By comparison, most steel has a tensile strength of under 1 GPa, and the strongest steels no more than 5 GPa, but steel is heavy. The much lighter material Kevlar has a tensile strength of 2.6–4.1 GPa, while quartz fiber can reach upwards of 20 GPa; the tensile strength of diamond filaments would theoretically be minimally higher.
Carbon nanotubes have exceeded all other materials and appear to have a theoretical tensile strength and density that is well within the desired range for space elevator structures, but the technology to manufacture bulk quantities and fabricate them into a cable has not yet been developed. While theoretically carbon nanotubes can have tensile strengths beyond 120 GPa, in practice the highest tensile strength ever observed in a single-walled tube is 63 GPa, and such tubes averaged breaking between 30 and 50 GPa. Even the strongest fiber made of nanotubes is likely to have notably less strength than its components. Improving tensile strength depends on further research on purity and different types of nanotubes.
A seagoing anchor station would incidentally act as a deep-water seaport.
Enlarge
A seagoing anchor station would incidentally act as a deep-water seaport.
Most designs call for single-walled carbon nanotubes. While multi-walled nanotubes may attain higher tensile strengths, they have notably higher mass and are consequently poor choices for building the cable. One potential material possibility is to take advantage of the high pressure interlinking properties of carbon nanotubes of a single variety. [4]. While this would cause the tubes to lose some tensile strength by the trading of sp2 bonds (graphite, nanotubes) for sp3 (diamond), it will enable them to be held together in a single fiber by more than the usual, weak Van der Waals force (VdW), and allow manufacturing of a fiber of any length.
The technology to spin regular VdW-bonded yarn from carbon nanotubes is just in its infancy: the first success to spin a long yarn as opposed to pieces of only a few centimeters has been reported only very recently; but the strength/weight ratio was worse than Kevlar due to inconsistent type construction and short tubes being held together by VdW. (March 2004).
Note that as of 2004, carbon nanotubes have an approximate price higher than gold at $100/gram, and 20 million grams would be necessary to form even a seed elevator. This price is decreasing rapidly, and large-scale production would reduce it further, but the price of suitable carbon nanotube cable is anyone's guess at this time.
The cable material is an area of fierce worldwide research, the applications of successful material go much further than space elevators; this is good for space elevators because it is likely to push down the price of the cable material further. Other suggested application areas include suspension bridges, new composite materials, better rockets, lighter aircraft etc. etc. |
| Quote: |
A space elevator, also known as a space bridge or star ladder, is a hypothetical fixed structure from the Earth's surface into space for carrying payloads. Plausible techniques for building a space elevator include beanstalks or Space fountains or even certain very tall compressive structures, similar to those used for aerial masts. A Space fountain would use particles fired up from the ground to form a dynamic, quasi-compressive structure. However, space fountains and tall compressive structures, whilst possibly reaching the agreed altitude for space (100 km), are unlikely to reach orbit and would require additional rocket or other means to leave the Earth.
A beanstalk (see Jack and the Beanstalk), on the other hand, is an orbital space elevator that uses a cable that 'hangs down' to the surface from synchronous orbit. It is also called a geosynchronous orbital tether, and is one kind of skyhook. A beanstalk attached to the Earth could eventually permit delivery of great quantities of cargo and people to orbit, and at costs only a fraction of those associated with current means.
Construction would be a vast project: a beanstalk would have to be built of a material that could endure tremendous stress while also being light-weight, cost-effective, and manufacturable. Today's materials technology does not quite meet these requirements. 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, optimists say that the necessary technology could be developed by 2008 [1] and the first space elevator could be operational by 2018 [2] [3]. |
http://en.wikipedia.org/wiki/Space_elevator |
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Bulsajo
Joined: 16 Jan 2003
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| Posted: Wed Aug 31, 2005 7:21 am Post subject: |
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Gas prices hitting $1.30CDN per litre in Ontario today  |
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