Talk:Space elevator

Centrifugal Physics

From Wikpedia, the equation for centrifugal acceleration is w*w*R. Where w is the angular rate of rotation and R is the distance between the rotating object and the center of rotation. Centrifugal acceleration needs to be equal to the acceleration due to gravity or greater. From Wikpedia, the acceleration due to gravity is 9.8 m/s/s. The Earth is spinning at a fixed w of (2*PI/(24*60*60)) = .0000727 radians per second. From Wikpedia, the Radius of Low Earth Orbit is an altitude up to 2000000 metres. From Wikpedia, the Radus of the Earth is over 6000000 m. So Earth's Low Earth Orbit centrifugal acceleration is w*w*R = .0000000052885*(8000000 metres) = 0.04 metres/second/second. This is less than the 9.8 m/s/s required to overcome the acceleration due to gravity. The earth is not spinning fast enough for a tethered system. —Preceding unsigned comment added by Wyatt arp (talk • contribs) 03:51, 7 August 2008 (UTC)

OMG! You're right! All those Ph.Ds missed it, but you're much smarter!

Alas, it's such a shame, but we can't use it in the article, because it's 'OR'.- (User) WolfKeeper (Talk) 04:39, 7 August 2008 (UTC)

• You're right about the OR, but there's no need to be snarky. Reyk _YO! 04:49, 7 August 2008 (UTC)

To clarify, centrifugal force and gravity balance at the height of the geostationary orbit. Below that the net force is downward; above that the net force is upward.

—WWoods (talk) 21:27, 11 August 2008 (UTC)

Mr Wyatt is correct. Contrary to popular opinion, and also contrary to what is stated in the article, a space tether does not rely on "centrifugal force", so centrifugal calcs will not give the correct result. The main operating principle is a satellite in geosynchronous orbit.

Centrifugal force doesn't really exist anyway.

—Bobcousins (talk) 20:51, 5 January 2009 (UTC)

Um... actually it does work to use that here since the Earth/space elevator is in a non inertial frame of reference. See Centrifugal force for more details. Whether centrifugal force 'exists' see:[1]- (User) Wolfkeeper (Talk) 21:00, 5 January 2009 (UTC)

I just did the math (high school physics, not Particle Dynamics), and I got a geo-synchronous height of 42,000km. With better math I am sure I would get the agreed upon geo-synchronous height of 35,000km. So Check your math.

$a_{cent}=w^{2}*R$

$a_{grav}={\frac {G*M_{earth}}{R^{2}}}$

$R_{Balanced}=({\frac {G*M_{earth}}{w^{2}}})^{(1/3)}$

Mech Aaron (talk) 19:18, 29 September 2008 (UTC)

That's the radius of geostationary orbit — the distance from the Earth's center; the height above the Earth's surface is 6,378 km less, that being the Earth's equatorial radius. See Geostationary orbit#Derivation of geostationary altitude.

—WWoods (talk) 23:34, 29 September 2008 (UTC)

Proposed cleanup

I've been following the debate and everybody seems to be getting bogged down in minutiae. Let's all take a step back and look at the big picture rather than getting into a edit war about what tags are and aren't valid. Dealing with the issues one by one.

• Sources. If something has been published in a journal or proceedings, cite it as a journal article. Citing a web site always leads to questions about the credibility of the source. This also protects against link rot.
• Length. Wikipedia's rule of thumb is "> 60 KB Probably should be divided". The length and the quality are linked as the article strays off onto tangents. Suggested division:

* Physics and structure: Way too technical. Suggest condensing this whole section into no more than a 3-4 paragraph summary and no more than one paragraph on each sub-section. Some could be split to Space elevator construction.

* Cable: There is a lot of overlap with Carbon nanotubes. Suggest condensing this whole section into no more than a 3-4 paragraph summary. Some could be split to Space elevator construction.

* Cable taper: The first paragraph is fine but nothing else is needed. I suggest splitting it off into a new article or link to the paper that came up with the equation. The equation is totally unnecessary.

* Climbers/counterweight: Seems okay but could be simplified a little

* Angular momentum, speed and cable lean: Too technical and unnecessary. A 1 paragraph summary and the diagram is sufficient for a general audience.

* Construction: Suggest a 1-2 paragraph overview and split to Space elevator construction. The fact that a company is now seriously proposing to construct one makes this notable in its own right.

* Failure modes, safety issues and construction difficulties: This is a very narrow aspect of the topic and goes into a lot of detail. Suggest splitting into Space elevator safety and Space elevator construction.

* Economics: A lot of this is already covered in Space elevator economics. Suggest migrating this whole section into that article and removing any overlap. Already linked as a "See also".

* Alternatives to geostationary tether concepts: This is straying a long way off topic. Since most of them already have articles, I suggest migrating these sections into the relevant articles and removing any overlap. They can be linked as "See also".

• Original research and synthesis. I can see why this is being raised. From WP:SYNTH, "Material published by reliable sources can be put together in a way that constitutes original research. Synthesizing material occurs when an editor comes to a conclusion by putting together different sources. If the sources cited do not explicitly reach the same conclusion, or if the sources cited do not make this argument in direct connection to the topic of the article, then the editor is engaged in original research." The text needs to be very carefully examined to ensure the sources explicitly say the same thing as the text and there is no unpublished synthesis.
• Tone. Parts of it read more like a term paper than an encyclopedia article.
• Too technical. I agree that it is too technical for a general audience. Part of the reason seems to be it goes into a lot of detail about relatively minor aspects of the topic described above.
• Fiction. I understand the issue being raised. If this article is to be taken seriously all mention of fictional space elevators should be moved into Space elevators in fiction and described in more detail there. Any non-fiction proposals similar to fictional descriptions make the fictional descriptions more notable, not the other way around.

Comments? Cosmomancer (talk) 08:33, 27 September 2008 (UTC)

Also the lead has a weird little paragraph appended to it. If sourced, maybe it should be moved? It currently makes the lead longer than recomended 4 paragraphs.

Splitting uncited sections from here into new articles is also problematic, only those long section with sources need to be summarised and spun off. Others should bbe trimmed back until the editors that want the information here present the sources that they used to write the sections, otherwise we get more articles like [[Space elevator economics]]], which has just the same problems as hereYobmod (talk) 07:24, 29 September 2008 (UTC)

I've made some bold edits that somewhat simplify the article with less wandering off topic. The new space elevator construction and space elevator safety can now be significantly expanded and improved without being too off topic from this article. Cosmomancer (talk) 12:55, 1 October 2008 (UTC)

Tags and Edits

It seems that a lot of the problem here is that we have editors who come into an article and tag it with problems, but don't do anything to fix the problems. It's easy to demolish, harder to rebuild.--2008Olympian _chitchat^seemywork 02:26, 28 September 2008 (UTC)

Don't be bullied by excessive tagging. 71.191.40.106 (talk) 05:10, 28 September 2008 (UTC)

Any attempt to delete uncited original research gets reverted. People have tried to improve the article, but cannot. Deleting off topic and unsourced information after a decent interval of leaving it tagged isn't demolition, it is good editiing. If people don't like the tags, replace them with sources!

Note, removing all the completely uncited paragraphs more tha halves the readable prose of thise page from 51Kb to 25Kb (see draft with OR removed)). An article of this length with so much unsourced text needs the tags to warn readers.Yobmod (talk) 11:53, 30 September 2008 (UTC)Yobmod (talk) 07:17, 29 September 2008 (UTC)

I see absolutely no consensus that this tag should be added, frankly you're in a minority of one. Given that, I consider this to be a deliberate, entirely excessive defacement of an otherwise averagely written and referenced article.- (User) Wolfkeeper (Talk) 18:56, 27 October 2008 (UTC)

Yeesh! When was the last time anyone actually did any work on the article? It seems like the two of you are more interested in arguing and edit warring about whether the big glaring template at the top is appropriate than in improving the article. Yobmod, if there's specific unsourced claims you could try to find sources yourself; or, ask Wolfkeeper, who seems to be clued up about space elevators. And please don't follow through with your threat of gutting the article, at least not until people have made an honest effort in sourcing it. And Wolfkeeper... there are vast tracts of unsourced stuff in there that need to be substantiated. You're adamant that the article more or less reflects the current state of things. Well, you must have read about this stuff somewhere- tell us where. Reyk _YO! 23:41, 27 October 2008 (UTC)

Look, all I'm saying is that the article has over 50 distinct reference tags to 46 distinct sources. If anybody wants to tag particular statements or sections fine-no problem-but adding 4 or 5 general tags to make claims about the entire article completely misrepresents the state of the article and is simply not what these tags are for; I could understand it if it had 10 references or something, but this is out of all proportion.- (User) Wolfkeeper (Talk) 01:26, 28 October 2008 (UTC)

Erm, you removed the citation needed tags i added, remember? And many others have added (diff [2]) But i still count 17 improvement needed tags in the article. Why not just add the cites, as you have read so much on the subject? I cannot add cites for things i have no sources for. Removing the citation needed tags, then claiming that the unreffed template is not-needed does not improve the verifiability of this articleYobmod (talk) 08:44, 28 October 2008 (UTC)

My original stated complaint was that there was tags without work to remove them, not that the tags were there to begin with. The work I've done on the article has focused on citing the statements in the article, as well as ensuring that the references actually support the propositions for which they stand. The tags are correct, the article was full of unreferenced statements, and still is to a great, if lessened degree. We should take advantage of the fact that this article's demotion from featured status gives it a chance to be in the spotlight of a renewed effort to resurrect it and point out what is wrong with the article to editors who come here in that spirit. I think the tags are accurate, and I note that there are a few less than when it was first tagged.--User:2008Olympian_chitchat^seemywork 09:38, 1 November 2008 (UTC)

I don't know the topic, but I know tag grafitti when I see it. "Defacing the article" is good, I'm going to remember that. Editing means writing - or helping writers to write better, which is why there are talk pages. I saw the offending paragraph and thought, "Ah, rhinocerous in a china shop!!" It's just a passive-aggressive way to argue without seeming to. "Who says so?!?!? Where'd ya get that?!?!? EH,EH?!?!?" Editing is writing, or helping to write better, IMHO. Tagging means nothing - personally I wish they didn't exist at all - they're a lazy way of thinking you're actually doing something. Jjdon (talk) 20:40, 10 March 2009 (UTC)

Vandalism

I have requested temporary semi-protection from the anon IP vandalism. Cosmomancer (talk) 06:18, 11 October 2008 (UTC)

Unclear

The article does now mention that not all plans involve a geosynchronous target, but it still doesn't explain why the most popular ones do; or at least, I didn't see it. Can someone please add, if not in layman's terms then at least with some explanation, why the geosynchronous orbit is so important? Why can't the elevator end at much lower orbits, and just have a mobile or airborne platform at the bottom? Obviously if this were possible the entire materials cost would be reduced enormously, which is why it comes to mind; but like presumably many other readers I am not seeing why this intuitive solution is not practical. Someone help? Leushenko (talk) 12:56, 31 October 2008 (UTC)

Most designs call for a stationary cable, whether or not the lower end actually touches down. The only way this can be achieved is with geosynchronous orbit. There are proposals involving much shorter "flyby" cables in a non-synchronous orbit, but this opens another massive book of engineering challenges in terms of transferring cargo to the cable. Stationary cables are the only designs under serious consideration.--Yeti Hunter (talk) 13:48, 31 October 2008 (UTC)

Summary image

A while ago I replaced the current image () with this SVG (). It seems to have been completely shunned by Verdatum, stating "the vector version of the image is incorrect". Problems cited are: the elevator appears to be stationed at the north pole rather than the equator (which is odd, because the svg uses a rather abstract representation of the globe, without any recognizable continents), and that the SVG does not mention geosychonronous orbit (which just isn't true; it does include that label). I must say I'm rather disappointed at the choice to completely cast this image aside due to some fairly minor qualms. Is there any good reason why it shouldn't be swapped back in? ~ Booya ^Bazooka 23:14, 24 November 2008 (UTC)

I must admit, it does really rather give the impression of orbiting at the North pole. The central continent looks a lot like africa/europe and the bit to the south looks like Australia. Of course it's completely non geographically accurate, but that does seem to be the impression. If you rotate the Earth through 90 degrees or something that might fix it. FWIW in general, I find the use of svg to be rather theoretically better than actually contributing to the project. svg are not significantly more scalable or device independent than gif or anything else for the purposes of the wikipedia, as the latest version of Firefox demonstrates only too well.- (User) Wolfkeeper (Talk) 01:33, 25 November 2008 (UTC)

I don't think rotating the planet would help. The current image clearly depicts the pole, while the arrow indicates an equatorial orbit. The SVG might be an abstract depiction of a planet, but it loses the suggestion of a top-down view. I am not opposed to replacing it with an SVG version, as long as the replacement is at least as descriptive as the current image. Wronkiew (talk) 01:49, 25 November 2008 (UTC)

I'm the Verdatum of which Booya speaks. My position matches Wronkiew. I happily would have edited the SVG to add some clarification of the image orientation, but my Inkscape skills are fairly mediocre, and the PNG image still existed and was perfectly acceptable. I would suggest adding a more accurate representation of the North or South Pole, and/or perhaps add some labels describing the planet's orientation/rotation, etc. and then sure, bring it in. -Verdatum (talk) 03:38, 25 November 2008 (UTC)

(Oh yeah, for everyone's info, this issue was originally discussed here.) -Verdatum (talk) 03:46, 25 November 2008 (UTC)

MediaWiki turns the SVG into a PNG in the article - the benefit isn't about browser display. Vector graphics are supposed to be easier to edit. And my main purpose in making it wasn't to change the file format, but to add the text labels. ~ Booya ^Bazooka 08:45, 27 November 2008 (UTC)

In practice though, they're harder to make, because you have to specify rather more information when you generate them. The toolset to manipulate them is also less reliable and advanced right now which doesn't help either.- (User) Wolfkeeper (Talk) 22:41, 30 November 2008 (UTC)

I just did a quick automatic trace of the raster planet and put it into the svg. Since the globe seemed to be the only point of discussion, and it is now nearly identical to the original, I'm putting the new version back in. A better globe image would still be welcome (the 2.5-megabyte trace makes me a little sad), and I like the idea of adding some markings (I hadn't even realized it was the pole, which is why it didn't make it into my adaptation in the first place). I just wish the image hadn't been out of commission for a year when the fix was so simple. ~ Booya ^Bazooka 08:45, 27 November 2008 (UTC)

I recommend an illustration that shows the correct scale of the position of geosynchronous orbit with the diameter of Earth. The current illustration is not to scale. Mydogtrouble (talk) 18:00, 14 January 2009 (UTC)

If I'm not mistaken, for the image to be to scale for a geostationary orbit, the length from the the center of the earth to the center of the Center of mass for the elevator would need to be approximately 6.62 times the length from the center of the earth to the outer edge/equator (42,164km / 6,371.0km). I'm not certain if this would look silly or not. If anyone is interested, I suppose they can try it out, and if it's not unreasonable, it might not be a bad idea. -Verdatum (talk) 19:33, 14 January 2009 (UTC)

Entire Mass of Cable

Estimating the required mass of the entire cabling system would be very useful here. My calculations show an approximation of roughly 1,000,000 metric tons of material required if the strongest estimates of buckytube are used. I would certainly be grateful if someone (preferably several contributors) checked with their own calculations.Mydogtrouble (talk) 19:38, 30 November 2008 (UTC)

It depends on the payload size you're trying to lift. IRC a payload to tether ratio of a few thousand is typical, depending on the CNT strength.- (User) Wolfkeeper (Talk) 22:38, 30 November 2008 (UTC)

I'm afraid your calculations (and those of any other editors) are Original Research. The mass of the cable should only expressed in this article as figures that can be attributed to reliable published sources. -Verdatum (talk) 19:51, 14 January 2009 (UTC)

The Center of Mass is not at GEO

The first image makes you believe that the center of mass is at GEO which is not the case at all http://gassend.net/spaceelevator/center-of-mass/index.html —Preceding unsigned comment added by 82.225.161.243 (talk) 12:18, 6 January 2009 (UTC)

Good point. I think the idea is that the initial orbital construction station needs to be there, and from there people assume that will stay put. Of course that might well be the case, but the center of mass will not at the end be at that station, then. Dismalscholar (talk) 06:49, 7 January 2009 (UTC)

Materials strength -- self-length

There's a concept known as self-length, designating how long a strand of a material can be before it breaks under its own weight. That's something that should be included here, because it makes it clear to laymen what sort of strength is required, and enables simple comparisons to available materials. I have no idea what the self-length of a buckytube cable might be; self-lengths of things such as steel cable, hemp, and nylon cab;e are easily available. Not too many people grasp tensile strength, but this is a concept I've had no trouble explaining even to younger teens.

Dismalscholar (talk) 06:47, 7 January 2009 (UTC)

You going to tackle the issues of harmonic oscillation which plague any suspension bridge too? Tethers are structurally similar to suspension bridges. Simple tethers would vibrate like a guitar string on sudden loading.

How about the other issues of loading shock caused to the structure when loads are attached? Instantaneous loads during initial tethering are far higher than sustained loads especially if the object to be picked up is slightly off from the optimal position for attachment (real life affects of weather or minor booster engine performance etc) by a few 100 meters. All you commonly see are the sustained load calculations. But like for real aircraft it is often the few moments of landing or in this case attachment that cause peak stresses and structural fatigue. Engines have fallen off jetliners due to such things when the aircraft industry was much more mature than tether building industry.

I have a feeling that all that is too technical for public consumption or even 3rd party authoritative inspection...despite the fact that collapsed bridges prove that engineers can make mistakes of oversight or miscalculation. The "off the record" answers I have heard from some interested but unfunded physics academics are that is more important to get the first tether built first before publicly addressing that issue or other difficult engineering complications. Basically if initial tests show a big problem these folks are in favor of simply de-rating that first tether's load lifting and call it a proof of feasibility project. Yikes! I hope that first tether is in lunar use then. For truly large cost projects the official funding and also the politics of extreme opposition sure make me uncomfortable with Wikipedia rules on authorities. One political side or the other basically controls those accepted voices Wikipedia will accept while fencing out many well-qualified people because they have no officil project involvement nor media selected role as spokesperson for the fanatic opposition.

But people shouldn't be too concerned I suspect that the disaster scenarios of opponents are a bit ivory tower as well. I doubt that a broken cable or falling tether assembly would repeatedly whip the face of the earth and squirm all about. One impact and it would shatter or embed itself in the crust. So the area of total destruction is unlikely to be more than a kilometer wide even if up to hundreds Kilometers long or just likely most the tether will follow itself own length to pile up in one relative small area only a few kilometers across. Unfortunately we unlikely to get good disaster projections from the same place as we get the official construction and safety info. In high stakes projects like this authorities tend to polarize into pro-construction "its as safe as houses" and "we need not specify complete disaster scenaroes" and the anti-construction side that publishes nothing but horrific and unlikely (even impossible) disaster calculations. 69.23.124.142 (talk) 19:37, 8 June 2009 (UTC)

Distracting Animated Images

The current image of the rotating carbon nanotube is a serious distraction for someone trying to read the text. The eye will naturally turn toward movement and trying to resist this imposes mental stress on the reader. If someone has an image to replace the animated carbon nanotube, I would suggest using it, instead of the current one. Bruhsam (talk) 12:58, 28 January 2009 (UTC)

Artificial gravity

In the discussion about what could potentially be the anchor for a space elevator, there is mention of locating a space station at the end. It occurred to me that being above GSO, there would be a substantial centripetal acceleration, and thus simulated gravity without the need for a spinning space station. Is this benefit mentioned in the relevant literature, and if so, does it bare mentioning in the article? ce1984 (talk) 09:48, 30 January 2009 (UTC)

Only if you have a source, and it benefits the article, of course.--72.74.112.203 (talk) 22:32, 6 May 2009 (UTC)

Clarification needed re: Equator

It's not really clear from the article that a tether type space elevator must be constructed at the equator. You can sort of deduce it from some of the wording of the article, and from the concept itself, but it's never actually mentioned directly. I wasn't actually sure, until I looked at the Space fountain article, where it is mentioned in the intro paragraph.--Pariah (talk) 00:29, 19 March 2009 (UTC)

Rotating Space Elevator concept

from PhysOrg.com, May 21, 2009: Rotating Space Elevator Propels its Own Load

The idea of the space elevator just got a little crazier. While the “traditional” concept involved using rocket propulsion or laser light pressure to propel loads up a cable anchored to Earth, a new study shows that a rotating space elevator could do away with engines or laser light pressure application completely. Instead, the unique double rotating motion of looped strings could provide a mechanism for objects to slide up the elevator cable into outer space. The space elevator could launch satellites and spacecraft with humans, and even be used to host space stations and research posts.[3]

Seems interesting and something that should probably be reflected in the article. N2e (talk) 13:21, 25 May 2009 (UTC)