Talk:Megascale engineering

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Perhaps this should be merged with the "megastructure" entry? --Christopher Thomas 14:41, 13 Feb 2005 (UTC)

[edit] Unknown megastructures?

What about oil pipelines, powerlines, highways? These are structures that stretch for many, many megameters in length. [26-Jan-2005]

Good point! But they don't fit the "self-supporting" critera. - Beowulf314159 02:07, 27 January 2006 (UTC)

[edit] Space Evelators

The article tags space elevators as possible with current technology.

Is this correct?

My understanding is that while material science can produce the single crystal carbon filaments that would be required to produce an "orbital elevator" on Earth, it can only so so in very small amounts, and only short lengths (or at least not length of 10s of 1000s of miles length - my impression was of a few inches only).

I remember reading an article that said that a 'lunar orbital elevator is possible, as kevlar fibers have the tensile strength needed for such a structure in lunar gravity - but I've seen nothing about any material that can be produced in industrial quantities by current technology being sufficient for a Terran orbital elevator.

Is this article in error, or is my information out of date? Beowulf314159 15:21, 8 December 2005 (UTC)

Whether it's currently technically possible or not is debatable as it's never been tried and is such a radical idea that it's difficult to say if it will ever be possible. However, this is not entirely important; if there's no reference supporting that claim in this article it is at the very least original research and needs to be corrected. siafu 16:33, 8 December 2005 (UTC)

Oh, I think it's safe to say that the article is poorly referenced - however I don't think anyone who has been reading in any field that touches on exploratory engineering can say that it's "original research" - the concepts and structures expressed in this article have been around for a long time, and have been mentioned in many places. When I grab a spare moment I may have to slip some of the references in.

A space elevator for Earth would require a material with a minimum tensile strength of between 30 and 60 GPa, depending on how much tapering you were willing to tolerate. Carbon nanotubes have a theoretical tensile strength on the order of 120 GPa, and macroscopic laboratory samples have been measured to have a tensile strength in excess of 60 GPa. The problem is one of developing a suitable mass-fabrication technology, as opposed to any question of whether materials of the required strength are possible. More information is at carbon nanotube. As for documentation of the elevator concept itself, ample references exist, mostly cited at space elevator. --Christopher Thomas 20:16, 8 December 2005 (UTC)

The documentation/reference requested is not for the space elevator itself, or even any conceptual or exploratory engineering design, but some support for the claim that the project can be completed with existing technology, as stated in Beowulf314159's original objection. siafu 20:40, 8 December 2005 (UTC)

That information is at carbon nanotube, as mentioned above. We have macroscopic lab samples *right now* that have about twice the needed tensile strength. Nanotube composites are being produced, again right now, in large quantites, though the types of composite that are being mass-produced do not (yet) have the needed tensile strength. This is solely a matter of growing tubes long enough that London forces between the tubes and the binding material are strong enough to transfer stress between nearby nanotube fibers. See composite material. Nobody in the field doubts that this can be done. If you want a link for some of the work on composites, a sampling of papers are listed on Prof. Baughman's page at the University of Texas in Dallas's nanotech group. Many researchers at other universities are also contributing to the field; this group is just the one that's demonstrated the largest-scale fabrication to date. --Christopher Thomas 21:31, 8 December 2005 (UTC)

I think you may be confusing me with someone whose making an argument about the veracity of the claim; I am not. I was just indicating that without a citation this claim was at best not researched and at worst original research. siafu 21:41, 8 December 2005 (UTC)

Per my original response, you can find all the citations you want at carbon nanotube and space elevator. Copy appropriate ones here if you feel they must be in this article too. --Christopher Thomas 22:19, 8 December 2005 (UTC)

Indeed - the material is covered in the space elevator article, quite thoroughly. This article only claims that the current engineering technquies are sufficient - and think that is probably true. I wasn't asking if the materials were possible - that I knew. I was questioning the implication that we could take current technology and start building tomorrow if we have a few USD trillion to spare. This isn't quite true - we can't create nanotubes in industrial quantitues - but it's also not what the article claimed. I think it's easy to misread the article though, so I tried to make what was being said less easy to confuse. Beowulf314159 21:44, 8 December 2005 (UTC)