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Ok, so I did a whole bunch of googles to find out what terms are most popular:
(Note these will vary over time as pages come and go and as google changes their page rank and so Results 1 - 10 of about 65 for "space ladder" geosynchronous. (0.28 seconds) forth.)
Analysis:
Beanstalk is the most popular, but only because of 'Jack and the Beanstalk'. Clearly 'beanstalk' on its own isn't enough; because beanstalk is ambiguous. If you remove that the correct order seems to me to be: space elevator, beanstalk, space bridge, space lifts, star ladder
WolfKeeper 21:23, 14 January 2006 (UTC)
Ok, so let's append 'geosynchronous' to the different terms to see what we get:
OTOH:
And the order is much the same. (Note that people that beanstalk geo hits jack and the beanstalk a lot here. Also, 'star bridge' rates unusually highly- that's probably because there are several companies including 'Star Bridge' in their name, and geo itself is also a common name for products.) WolfKeeper 22:41, 14 January 2006 (UTC)
Decision: space elevator, beanstalk, space bridge, space lift, space ladder, star ladder WolfKeeper 22:46, 14 January 2006 (UTC)
Hope you don't mind, I added "orbital tether" to your results above. It didn't rank very highly, though, so it's looking like not the best sort of title. In fact, it's looking like "space elevator" is indeed the correct title for a ground-to-orbit tether as far as Wikipedia is concerned. This now moves my dilemma to coming up with a new name for the generic ground-to-orbit elevator, so that the intro of this current article can be split off to it. I wouldn't want to use Space elevator (disambiguation) because disambig pages generally don't contain article-like information in them - they're supposed to be ignored wherever possible. Hm. Bryan 23:05, 14 January 2006 (UTC)
There is a section that recognizes sabotage as an area of consideration when planning a Space Elevator, as well as ways to protect against it. But what ARE these anti-terrorism plans? Gigem12 06:32, 1 July 2006 (UTC)
Could someone please explain to me why this sort of device doesn't violate the conservation of energy? Why wouldn't a climber, pulling down on the tether, force the satellite into a lower (faster) orbit, thus breaking the geosyncracy? i.e. Where does the potential energy a climber gets while climbing come from? —The preceding unsigned comment was added by 66.240.10.170 ( talk • contribs) .
The strength of the tether is marginal, particularly in the lowest section. How much benefit could be had from supporting some of that lower section on balloons? -- Midgley 22:44, 21 January 2006 (UTC)
Well, the average weight of the cable is under 1kg/km (lower particularly near the earth). A balloon might be able to go up maybe 30km or so I guess. So you'd only be saving 30km worth of cable worth of payload- about ~30kgs. WolfKeeper 23:46, 21 January 2006 (UTC)
A lot of people talking on this page seem a bit confused - even I had to think about it somewhat before I realised what's actually going on. A space elevator is first and foremost a satellite in geostationary orbit. Thus its centre of mass is in that orbit. The forces on the cable extending down to the Earth, and up to any counterweight, are tidal in nature. Consequently they are greatest near to the centre of mass, and that's where the cable is thicikest. In principle the elevator doesn't need to be connected to the earth at all, and should exert no force on Earth. In this case, manoeuvering the elevator eg to avoid satellites is accomplised by rocket thrusters mounted on the elevator itself.
Thus it is wrong to speak of 'supporting' the cable by balloons. If one, for example, terminates the cable at 20km altitude, the elevator will still function provided the payload can be got to the base. Balloons or airships could accomplish this, but a better option might be a tower.
Also, it may be worth mentionning of the possibility of using some sort of funicular system, or regenerative braking, to gain energy from descending loads. It's likely a space elevator _would_ be used for descent, since it would eliminate the heating problems associated with standard reentry. 128.232.250.254 14:15, 23 May 2006 (UTC)
I would not think of a balloon just as a means of supporting the cable, I would make it a transfer station, a hotel, an observation tower, a radio repeater and make money out of it, well, at least, cover its operating costs... whatever. People might not care to spend several days (and lots of money) to get to geosynchronous orbit, but many wouldn't mind spending some time, hours or a few days, watching the Earth from above, and specially the trip up and down.
A balloon up there would allow for two separate models of climbers, one from the balloon to the ground and one for the rest of the trip, one atmospheric, the other not. The first would be cheaper (good for bringing tourists to the balloon) the other more expensive, since it has to deal with vacuum and several days of travel.
Moreover, the balloon would allow for two different propulsion methods. Cars in the lower segment would be plain cablecars moved around by a continuous tape. Actually, in this lower segment, the cars might not even use the main cable at all, they would all just grip the moving cable. The taper of the cable, mentioned elsewhere as a problem to this propulsion mechanism for the full trip, is not a problem in such a short length.
The cars above would still use power beams, with an added advantage: there is less atmosphere to dissipate its energy. In this sense, the higher up the balloon can be, the better to avoid as much of the atmosphere as possible (and to give tourists to the balloon the better view).
Also, a hot air balloon big enough is self buoyant, the sun can heat it enough so that it just stays afloat without any fuel or need to replenish helium. Actually, leaks become a minor maintenance problem, not a catastrophe. I still remember reading an article in the IEEE Spectrum magazine about that around 30 years ago (yes, it really impressed me). Based on then current materials a 400m diameter balloon would be self supporting, the larger you made it, the more the payload it could carry, a mile wide balloon could hold 400 tons or thereabouts. Building it and launching it was a big problem then, but not if you have an elevator.
The balloon at that height would also provide a better anchor since several cables from separate ground anchors could converge in it, thus sparing the upper cable from most atmospheric turbulence. -- DevaSatyam 09:17, 1 September 2006 (UTC) wolfkeeper gave a good answer. A 30 kilometer altitude balloon supported platform increases the pay load by about 30 kilograms = 0.03 meteric tons. The platform is largely untested, humans would need a space suit at 30 kilometers. The climbers could climb the hold down ribbons for the platform, but it would be nesesatry to transfer the climber to the up ribbon at the platform. In theory robots can be designed to make that transfer, but that technology is also largely untested. The flipping of the ribbon around low earth orbit satelites and space junk is more difficult with the ribbon anchored at a platform instead of an anchor ship. Neil
Sorry for not being very constructive, but the whole article is a horrible collection of heresay and speculation. The space elevator concept is still largely science fiction. Th article leaves the impression that space elevators will be operational 2018, and if not shortly after.
I acknowledge that space elevators are theoretically sound concepts, but so are generation ships, dysonspheres and cryonic conservation of live humans. The engineering challenges are *vastly* beyond reach of current technology in a number of areas.
The first two paragraphs of the article are really good, no reason for critic here. But then follows a very large list of ideas and concepts concluded by a simplistic speculation why the problems of that approach can be overcome with no substantial evidence for any solution.
I think that the article should be substantially reduced in size, expelling the several wild speculations, especially about the future state of science.
Some examples:
"The primary power methods (laser and microwave power beaming) have significant problems with both efficiency and heat dissipation on both sides, although with optimistic numbers for future technologies, they are feasible."
What reasons exist to believe in an efficiency improvement in power beaming? This section is optimistic without reason.
"For higher velocities, the cargo can be electromagnetically accelerated, or ..."
This sentence asserts the possibility of building a *railgun* in *space*, another theoretically sound project with equally epic engineering problems. This section is plainly ignoring problems.
"He proposes that a single hair-like 20 short ton (18 metric ton) 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity."
How is that supposed to happen? Is the cable to be unrolled from space?
What drags it down?
Should it be deployed in flight? At 10 km/s without tearing? This section is too unspecific.
"Sabotage is a relatively unquantifiable problem. Elevators..."
The whole section contains commonplace knowledge about sabotage. It refers to no original source.
I actually envision a lauching platform for space travel over a cable for a balloon station 20-30km high. transport up though could be with 1 or two stages of balloons on cable. I imagine stages or at least a special construct for the upper platform are neccesarry becus you dont want to loose to much He. Cables if any, would firstly lead to the balloon platform (that should be huge)
perhaps spacecrafts can be launched from (rocket)propulsed balloons upthere, wich would allow for a smaller platform.
Is there a space in the non-tether solutions for Lofstrom's idea to be mentioned? I rather like it. Midgley 18:59, 16 March 2006 (UTC)
I was just wondering, how far one could see the elevator if such a thing would be constructed? —Preceding unsigned comment added by 212.149.214.123 ( talk • contribs)
Depends on a number of factors, really. Time of day, how refractory the outer layer of the ribbon is, the ultimate dimensions, weather, angle of view, etc.
We think the ribbon - on the first generation SE - is going to be a meter wide (average) and paper thin. Depending on your angle you'll have a hard time seeing just the ribbon more than a kilometer away under optimal conditions. Bdunbar 21:30, 24 March 2006 (UTC)
At time of writing, the article used 5.294e10 m^2/s^2 as the factor in the taper ratio calculation. However, substituting values in to the equation ( [1]) seems to give a value of 4.832e7 m^2/s^2.
Also, in (J. Pearson, "The orbital tower: a spacecraft launcher using the Earth's rotational energy" in "Acta Astronautica" vol 2 pp. 788, 1975) Pearson uses the equation:
where . Substituting h into the equation gives:
and
[2] gives 4.840e7 m^2/s^2, which agrees with the figure of 4.832 given above (the difference is because the factor of 0.776 is rounded). I shall change it myself and reference Pearson's paper, but I'm placing justification here for future reference.
Someone42 12:10, 18 April 2006 (UTC)
Um, what exactly is "magnetospheric braking of the cable to dampen oscillations"? -- Simonf 05:21, 17 May 2006 (UTC)
I removed this from the article:
"A lunar space elevator would need to be very long—more than twice the length of an Earth elevator, but due to the microgravity of the moon, can be made of existing engineering materials." -- The word was linked to the Microgravity article. If anyone had read it, they would have known that it was the wrong word to use here. Ravenswood 18:30, 23 June 2006 (UTC)
According to The Guardian [3], NASA will be inviting bids to build a space elevator, during this month (September 2006). If this is true, this is exciting news, however I didn't realise current technology is ready yet. The Guardian didn't state its sources for this report.
This really isn't a current event. We may expect significant updates maybe every few months. But this doesn't make it necessary to view it as a current event surely? Barnaby dawson 21:14, 3 September 2006 (UTC)
In the hazards, there's no mention of the possibility of airplanes or such to crash into space elevators... There should be, shouldn't there be?
The cable thickness equation is summarized as follows:
This equation gives a shape where the cable thickness initially increases rapidly in an exponential fashion, but slows at an altitude a few times the earth's radius, and then gradually becomes parallel when it finally reaches maximum thickness at geostationary orbit.
As a casual reader (me), the word "parallel" makes no sense. How can the cable thickness go from "increasing rapidly" to "slows" and then to "parallel?" Parallel to what? Please adjust. JM 216.165.146.161 07:28, 28 September 2006 (UTC)
This is seriously disappointing how often the word centrifugal is used in this article, whereas centripetal is used only once. I have neither the time nor the degree of concern necessary to make the appropriate changes to this featured article, but let it be known that there is no such thing as centrifugal force. Look at the first bullet under centrifugal's article and you'll see the words "Pseudo or fictitious." Please, please, please, when talking about matters of science such as the space elevator use the term centripetal. And yes, I am aware of a device called a centrifuge, but it does not use centrifugal force, contrary to what the Wikipedia article may say. Wikipedia is not, after all, the sole responsiblity of the respectable scientific community. It uses centripetal force. The word 'ain't' made it into the dictionary only by frequent batteries of misuse. Those of you responsible for Wikipedia's contents, please find it in your hearts not to let the whole centrifugal situation get any worse than it has gotten.-- Spawnofbusey 23:32, 16 October 2006 (UTC)
Am I the only who thinks this article is far to long? When it gets to the point that editing gets slow it is well beyond what it ought to be. Nobody sits down and reads through all this. I would recommend that some sections were moved into their own articles and that there was a much shorter section about them here(as hs happened with Space elevator economics). Elentirmo 00:26, 14 December 2006 (UTC)
Reference #16 says it's a 404 error at the location it was originally found. However I found it here, should I update the link even though it's not on a NASA website? Grant 19:18, 3 January 2007 (UTC)
I wandered away from this article for a while to do other things but I think a major problem I raised in #About this word 'Plausible' is still unresolved. The intro paragraphs for this article talk about how all sorts of structures that reach from ground to space fall under the classification "space elevator", and then there's an "orbital tether" header and everything after that reads like a separate article on just orbital tethers. Basically, there are two separate articles on two different topics that are spliced together in one page. My proposal before was to split off the orbital tether section into its own article ( orbital tether), leaving space elevator as a general overview of the various concepts, and although objections was raised they were very nonspecific as to what was wrong with the idea. Does anyone have any other solutions to suggest, or specific details as to why my proposed solution is bad? Bryan 20:13, 14 January 2006 (UTC)
I more or less did this once already, and people reverted it. I didn't call it orbital tether I called it 'beanstalk'; but otherwise that's what I did. I think there's enough people that think that space elevator == beanstalk/orbital tether that it won't fly.
Besides who says that space elevator really isn't just a beanstalk? Is a space fountain actually a space elevator? Is a space elevator a structure that reaches space or is it just another name for a beanstalk? Near as I can tell wikipedia has a significant chance to define what 'space elevator' exactly means here. It's not totally clear. WolfKeeper 21:03, 14 January 2006 (UTC)
Cut the teather... Let the lift fall to space. No energy needed for it to reach space other than the couterweight! Construct a Lift Station in space that controlls the teather so the shipment and the couterweight do not fall into space.
O --- Lifting Couterweight | | --- Lifting Cable | ------------- | | ------ Lifting Station ------------- | | | | | | ------ Station Teathers | | | | | | | (=====) | ------ Cargo | | | | --------------------------------
Lifting Station controlls rate of Lifting Cable passed through it. Multiple teathers attach Lifting Station to the ground, station is and acts like its own couterweight. Guides can be attached to station teathers to controll cargo as it heads toward space. In the event of the lifting cable breaking the cargo would not fall to space or earth by safety devices that can be placed in these guides. Station would also be able to assist in getting the cargo going in the direction it needs to be going after it reaches space. —The preceding unsigned comment was added by 71.8.208.173 ( talk • contribs) 19:46 UTC, 5 June 2006.
I was at a talk about carbon nanotubes a while ago and the speaker mentioned that they would be a likely material to be used if a space elevator was ever built. This is already mentioned in the article. Can anyone back this up with a published source? savidan (talk) (e@) 17:09, 14 June 2006 (UTC)
I believe the diagram is incorrect. It labels the point on the cable which intersects the imaginary line of "geosynchronous orbit" as "center of mass". But wouldn't the center of mass, by necessity, be at an altitude higher than geosynchronous orbit? I would think that no matter how heavy the counterweight is, if the center of mass of the entire system (cable + counterweight + any climbers) falls below the height of geosynchronous orbit, then the entire thing would collapse. Ravenswood 17:12, 21 July 2006 (UTC)
The diagram is incorrect, and most of the language involving the center of mass is as well. The center of mass is nowhere near GEO. It is not expected to, because different parts of the structure experience widely different gravitational and centrifugal acceleration (in the rotating frame). The gravitational acceleration near the surface is much greater than the centrifugal acceleration beyond GEO, meaning the part of the elevator beyond GEO altitude is much more massive than the part below. If you don't believe me, take a close look at the Cable Taper Plot. What needs to balance on both sides of GEO altitude are the forces, not the mass, and less acceleration means more mass. It does not matter, though, because center of mass is not a useful concept for extended objects in an inhomogeneous field anyway. To say "the center of mass is in geostationary orbit" is plain wrong. If I get some consensus, I will edit the text, but I do not know how to edit the diagram. Andreas 20:00, 13 June 2007 (UTC)
The article currently contains the following paragraph:
I had to read this three times before I understood what it was trying to say, and that only because the vision of a paper streamer in the wind suddenly popped in my mind. This is screaming for a visual illustration... linas 04:49, 11 December 2006 (UTC)
How can the slowing of the earth caused by the existence of the lift only 'insignigicantly slow' the Earth's rotation? Surely any slowing of it's rotation is a very bad thing and would need some form of countermeasure? The fact that this topic was skimmed over in the wiki gave me cause for concern. 129.11.76.215 09:04, 1 March 2007 (UTC)MrLaister
Like the title says, I'm wondering if there is any information on the hanging tether idea. It's basically the same idea as the normal elevator, but is only 4K long (with COM at 2km), and the Earth end of the cable has a sky-hook/platform for rockets to transfer cargo to the elevator. I understand that it's being developed for the next X-prize, but I only have Japanese language sources on it so I don't want to add it to the article. Anyone know anything about it? -- Bakarocket 17:01, 6 March 2007 (UTC)
I'm intrigued by the idea of a space elevator. But surely there are similar applications that would cost far less to implement and should be mentioned in this article. Off the cusp, I can imagine a space pump for ridding the world of gaseous, solid, and nuclear waste. We could pipe all our waste to a network of regional pipes that could then be ejected through a central space pump into outer space. Obviously, the harmful waste would have to be ejected with a sun-bound trajectory so it would be incinerated. Bet that would put a significant dent in our polution and waste problems. Moto 02:31, 10 March 2007 (UTC)—The preceding unsigned comment was added by Teeroy ( talk • contribs) 02:21, 10 March 2007 (UTC).
Partly as a matter of interest and partly because maybe it should be added to the page, does anybody know how elongation and deformation from tension (and maybe even tidal forces) would affect the calculations? —The preceding unsigned comment was added by 207.112.60.14 ( talk) 00:01, 29 March 2007 (UTC).
Ok, I looked into a little more. If you look at the Pearson article (reference number 7 i tihnk), on pg. 10 he has a discussion on elongation. When the tower stretches, more of it is passes geosynchronous orbit which, in turn, stretches it more. For a tensile strength/Young's modulus of .0482 he gives a stretch of 5%. Nanotubes have ~.06 which would give an even higher stretch. Unfortunatly I didn't see this mentioned in any of the other article so I'm not sure what the deal is. 207.112.60.14 04:08, 29 March 2007 (UTC)Yonni
Anyone? —The preceding unsigned comment was added by 24.168.30.85 ( talk) 01:25, 29 March 2007 (UTC).
I've removed these from the article - hopefully someone out there is involved in maintaining the article who can deal with them. I hate to see these tags on a featured article, and the onus is really on whoever added them to provide a reference. Richard001 08:51, 5 April 2007 (UTC)
It's been a while since I posted this, so can no one provide any answers to the questions I was asking? I think it's needed, if not for myself, then for the article. -- Hibernian 23:22, 14 July 2007 (UTC)
I am not an expert on the subject but seeing as no one else has adressed your questions I will try. I assume it will get into Space like the ISS, in pieces and assembled in space. An asteroid can be any size at all. For the third, you might want to read the source. 10max01 23:31, 14 July 2007 (UTC)
Your answer seems pretty adequate. 10max01 00:37, 15 July 2007 (UTC)
86.137.107.103 19:18, 29 September 2007 (UTC)== Cable taper plot ==
The cable taper plot shows a wildly different area ratio at GEO to that quoted in the text for steel (about 1.8 versus about 10^14). What assumptions is the plot is making about the type of material used? Are these in any way reasonable? I think that this discrepancy needs to be explained in the article. Matt 13:06, 6 August 2007 (UTC).
Using a value of 2GPa for the tensile strength of steel and density of 8000kg/m3, the equation says that the area at geostationary orbit should be on the order of 10^80 (area at ground level of 1cm2). Unless my arithmetic's gone wrong, I think that the thickness at GEO for steel should be changed. Concerning the taper plot, the inverse strength-density scale isn't all that useful - most materials seem to have inverse strength density ratios of orders of magnitude lower than this, so the ratio Area/Ao would be orders of magnitude higher for most materials. Essentially, the cable taper plot is correct, but not particularly useful - if anyone knows how to extend it for other materials, that'd be very useful.
86.137.107.103 19:18, 29 September 2007 (UTC)
The notion that removing a few km of cable from the bottom of the elevator makes for great savings is just wrong. According to a very simple finite element analysis spreadsheet by Bob Munck (available in the yahoo group), the bottom 100 km of a 20 ton payload elevator weigh just ~400 kg. So, by building a 100 km tower you will save ~2% of capacity, or 2% of cable material. I would call that insubstantial, compared with the expense and plain impossibility of such a tower. The problem here is that antiquated notions from the earlier SE work (towers, asteroids, etc. etc.) which have since been outdated by Edward's work have somehow lodged within this article and need to be cleaned up. I suggest removing most references to towers or elevated locations except for one place where this is explained. Andreas 06:21, 13 June 2007 (UTC)
I am aware of No Original Research, though I reckon that it must be the case that someone has already published what I am stating here, and hence that the information is citable. But, would strategically placing Helium Balloons at certain points along the tether aid the feasibility of creating the elevator? I believe that this might be so as the tension along certain points of the tether would be reduced via the use of such balloons (they would relieve the tension of the tether from under it's own weight at several strategic points along the tether). However, this is only something that could be done up to a height of about 20 miles up (the height to which most helium balloons will go. You might be able to squeeze out some more height using Hydrogen. It may even be possible to create several mile high rigid `floating structures' attached to helium/hydrogen balloons that could support the tether 30 miles up or so by attaching so structures to such balloons. Nevertheless, I remain pessimistic that the (600 mile?) barrier for fully fledged space access is traversible from such meagre heights (though, in actuality, this outlined approach might be more feasible than the space elevator AND overcome a significantly large proportion of the energy costs requires for getting into space).
If I have made an error in my reasoning, I would sure like to know.
Also, perhaps (solar powered?) magnetic sails (that force against the Earth's magnetic field) could be used to reduce the weight induced tension along several points of the tether? Perhaps more conventional thrust generation methods would relieve the tension allowable for a greater flexibility in material utilisation?
A general point could be that the space elevator doesn't really need to take up into space at all in order to be economically viable – it just needs to get us 10% of the way up (aren't most of the energy hurdles in relation to leaving the Earth's gravitational field used up in making the first small proportion of the distance?).
I have not done any calculations when making this post – though I do believe that the approximate figures given are unlikely to be terribly incorrect in principle at least.
ConcernedScientist 01:22, 30 June 2007 (UTC)
(Consider F=BIL, and a long superconductor on a moving air based platform to see that Carbon Nanotubes might not be absolutely necessary).
Anyhow, forgive my rambling, all of this is probably WP:NOR bound, so I'll stop making a mention of these ideas (though I doubt that they're Original Research as they are so obvious that someone must have posted them some time ago...).
ConcernedScientist 00:59, 15 July 2007 (UTC)
I believe balloons will not significantly improve the economics of the Earth/GSO cable configuration. Cable materials can be characterized by the length of a uniform cable that can just sustain itself against gravity without breaking, essentially l = (T/(g*rho)), if l is the characteristic length, T is breaking tension, g is acceleration of gravity, and rho is cable material density. For a tapered cable near the surface, the area must grow by a factor of e every time you go upwards by l. If I recall, l is on the order of 10 km for ordinary steel cable.
Unfortunately, the effective potential height of the Earth's gravitational potential well is about 5,500 km (again "if I recall"). So for steel we get an awful factor, of exp(5500/l) = exp(550) or so. This effective potential is the depth of the gravitational energy well of the Earth (which is just the radius -- about 6380 km for Earth -- for any spherical planet, since the 1/R^2 force's potential is -1/R) after taking into account the opposing centrifugal force, integrated from the surface to GSO. So, it reduces the problem from about 6380 km to ~5500 km, not a huge effect.
Near the surface, the gravitational acceleration is g ~ 9.82 m/s^2, so the potential height is essentially the same thing as the geometric height, 1 km per km. Thus what kills you is the region between the surface and 1 radius or so, where you have the bulk of the effective potential height that has to be overcome. Because the atmosphere is thin, scale height ~10 km, balloons won't work high enough (50 km is about their limit) to have much of an effect (just as shortening the cable by say, 50 km, so that the end dangles above the atmosphere, does not really help either).
The good news in the horrible exponential is that, IF you can find a material with a much better l, you can get a colossal reduction in the mass and a corresponding improvement in the economics. As far as I know, single-wall carbon nanotubes have the best l known to date, I believe the figure is over 1,000 km. Unfortunately, they are not yet available in quantity with uniform quality and sufficient length. I believe spinning such fibers into multi-strand yarns or cables is probably the way to go, but as far as I know it is still just an exciting possibility.
A comment here from someone in July 2007 attacked carbon nanotubes, but (while I am by no means an expert) the theoretical l numbers measured for some of them seem to make them the material of choice. I will try to provide better documentation from the literature as soon as I can, if it has not already been done by someone else. (Being new to this article I need to read it all carefully, and the discussion too.) Wwheaton ( talk) 08:15, 18 December 2007 (UTC)
I replaced the SVG diagram of the elevator with the original PNG one, because the SVG showed the elevator to go up from the north pole, which is nonsense. Many people don't intuitively understand why it has to go from the equator, because many don't understand the idea of an orbit. 79.120.55.7 07:01, 20 September 2007 (UTC)
In the "Construction" section, there is a reference to "Five Key Technologies for Future Space Elevator Development". The Smitherman paper mentions 7 low-TRL areas, which don't match up with the 5 in our article (Smitherman doesn't mention towers for example, but they feature in several of ours). Perhaps there is another NASA study from which those 5 were taken. Kingdon 23:03, 9 October 2007 (UTC)
"In an ideal cable, the actual strength of the cable at any given point would be no greater than the required strength at that point (plus a safety margin). "
Shouldn't it say less than?
Good article, however a discussion of the reasons why an elevator isn't being built right now is missing. What challenges are ahead? Are there any problems associated with making the ribbon? The article primarily deals with what an elevator would look like, if it was there. -- Oz1sej ( talk) 10:32, 23 November 2007 (UTC)
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Ok, so I did a whole bunch of googles to find out what terms are most popular:
(Note these will vary over time as pages come and go and as google changes their page rank and so Results 1 - 10 of about 65 for "space ladder" geosynchronous. (0.28 seconds) forth.)
Analysis:
Beanstalk is the most popular, but only because of 'Jack and the Beanstalk'. Clearly 'beanstalk' on its own isn't enough; because beanstalk is ambiguous. If you remove that the correct order seems to me to be: space elevator, beanstalk, space bridge, space lifts, star ladder
WolfKeeper 21:23, 14 January 2006 (UTC)
Ok, so let's append 'geosynchronous' to the different terms to see what we get:
OTOH:
And the order is much the same. (Note that people that beanstalk geo hits jack and the beanstalk a lot here. Also, 'star bridge' rates unusually highly- that's probably because there are several companies including 'Star Bridge' in their name, and geo itself is also a common name for products.) WolfKeeper 22:41, 14 January 2006 (UTC)
Decision: space elevator, beanstalk, space bridge, space lift, space ladder, star ladder WolfKeeper 22:46, 14 January 2006 (UTC)
Hope you don't mind, I added "orbital tether" to your results above. It didn't rank very highly, though, so it's looking like not the best sort of title. In fact, it's looking like "space elevator" is indeed the correct title for a ground-to-orbit tether as far as Wikipedia is concerned. This now moves my dilemma to coming up with a new name for the generic ground-to-orbit elevator, so that the intro of this current article can be split off to it. I wouldn't want to use Space elevator (disambiguation) because disambig pages generally don't contain article-like information in them - they're supposed to be ignored wherever possible. Hm. Bryan 23:05, 14 January 2006 (UTC)
There is a section that recognizes sabotage as an area of consideration when planning a Space Elevator, as well as ways to protect against it. But what ARE these anti-terrorism plans? Gigem12 06:32, 1 July 2006 (UTC)
Could someone please explain to me why this sort of device doesn't violate the conservation of energy? Why wouldn't a climber, pulling down on the tether, force the satellite into a lower (faster) orbit, thus breaking the geosyncracy? i.e. Where does the potential energy a climber gets while climbing come from? —The preceding unsigned comment was added by 66.240.10.170 ( talk • contribs) .
The strength of the tether is marginal, particularly in the lowest section. How much benefit could be had from supporting some of that lower section on balloons? -- Midgley 22:44, 21 January 2006 (UTC)
Well, the average weight of the cable is under 1kg/km (lower particularly near the earth). A balloon might be able to go up maybe 30km or so I guess. So you'd only be saving 30km worth of cable worth of payload- about ~30kgs. WolfKeeper 23:46, 21 January 2006 (UTC)
A lot of people talking on this page seem a bit confused - even I had to think about it somewhat before I realised what's actually going on. A space elevator is first and foremost a satellite in geostationary orbit. Thus its centre of mass is in that orbit. The forces on the cable extending down to the Earth, and up to any counterweight, are tidal in nature. Consequently they are greatest near to the centre of mass, and that's where the cable is thicikest. In principle the elevator doesn't need to be connected to the earth at all, and should exert no force on Earth. In this case, manoeuvering the elevator eg to avoid satellites is accomplised by rocket thrusters mounted on the elevator itself.
Thus it is wrong to speak of 'supporting' the cable by balloons. If one, for example, terminates the cable at 20km altitude, the elevator will still function provided the payload can be got to the base. Balloons or airships could accomplish this, but a better option might be a tower.
Also, it may be worth mentionning of the possibility of using some sort of funicular system, or regenerative braking, to gain energy from descending loads. It's likely a space elevator _would_ be used for descent, since it would eliminate the heating problems associated with standard reentry. 128.232.250.254 14:15, 23 May 2006 (UTC)
I would not think of a balloon just as a means of supporting the cable, I would make it a transfer station, a hotel, an observation tower, a radio repeater and make money out of it, well, at least, cover its operating costs... whatever. People might not care to spend several days (and lots of money) to get to geosynchronous orbit, but many wouldn't mind spending some time, hours or a few days, watching the Earth from above, and specially the trip up and down.
A balloon up there would allow for two separate models of climbers, one from the balloon to the ground and one for the rest of the trip, one atmospheric, the other not. The first would be cheaper (good for bringing tourists to the balloon) the other more expensive, since it has to deal with vacuum and several days of travel.
Moreover, the balloon would allow for two different propulsion methods. Cars in the lower segment would be plain cablecars moved around by a continuous tape. Actually, in this lower segment, the cars might not even use the main cable at all, they would all just grip the moving cable. The taper of the cable, mentioned elsewhere as a problem to this propulsion mechanism for the full trip, is not a problem in such a short length.
The cars above would still use power beams, with an added advantage: there is less atmosphere to dissipate its energy. In this sense, the higher up the balloon can be, the better to avoid as much of the atmosphere as possible (and to give tourists to the balloon the better view).
Also, a hot air balloon big enough is self buoyant, the sun can heat it enough so that it just stays afloat without any fuel or need to replenish helium. Actually, leaks become a minor maintenance problem, not a catastrophe. I still remember reading an article in the IEEE Spectrum magazine about that around 30 years ago (yes, it really impressed me). Based on then current materials a 400m diameter balloon would be self supporting, the larger you made it, the more the payload it could carry, a mile wide balloon could hold 400 tons or thereabouts. Building it and launching it was a big problem then, but not if you have an elevator.
The balloon at that height would also provide a better anchor since several cables from separate ground anchors could converge in it, thus sparing the upper cable from most atmospheric turbulence. -- DevaSatyam 09:17, 1 September 2006 (UTC) wolfkeeper gave a good answer. A 30 kilometer altitude balloon supported platform increases the pay load by about 30 kilograms = 0.03 meteric tons. The platform is largely untested, humans would need a space suit at 30 kilometers. The climbers could climb the hold down ribbons for the platform, but it would be nesesatry to transfer the climber to the up ribbon at the platform. In theory robots can be designed to make that transfer, but that technology is also largely untested. The flipping of the ribbon around low earth orbit satelites and space junk is more difficult with the ribbon anchored at a platform instead of an anchor ship. Neil
Sorry for not being very constructive, but the whole article is a horrible collection of heresay and speculation. The space elevator concept is still largely science fiction. Th article leaves the impression that space elevators will be operational 2018, and if not shortly after.
I acknowledge that space elevators are theoretically sound concepts, but so are generation ships, dysonspheres and cryonic conservation of live humans. The engineering challenges are *vastly* beyond reach of current technology in a number of areas.
The first two paragraphs of the article are really good, no reason for critic here. But then follows a very large list of ideas and concepts concluded by a simplistic speculation why the problems of that approach can be overcome with no substantial evidence for any solution.
I think that the article should be substantially reduced in size, expelling the several wild speculations, especially about the future state of science.
Some examples:
"The primary power methods (laser and microwave power beaming) have significant problems with both efficiency and heat dissipation on both sides, although with optimistic numbers for future technologies, they are feasible."
What reasons exist to believe in an efficiency improvement in power beaming? This section is optimistic without reason.
"For higher velocities, the cargo can be electromagnetically accelerated, or ..."
This sentence asserts the possibility of building a *railgun* in *space*, another theoretically sound project with equally epic engineering problems. This section is plainly ignoring problems.
"He proposes that a single hair-like 20 short ton (18 metric ton) 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity."
How is that supposed to happen? Is the cable to be unrolled from space?
What drags it down?
Should it be deployed in flight? At 10 km/s without tearing? This section is too unspecific.
"Sabotage is a relatively unquantifiable problem. Elevators..."
The whole section contains commonplace knowledge about sabotage. It refers to no original source.
I actually envision a lauching platform for space travel over a cable for a balloon station 20-30km high. transport up though could be with 1 or two stages of balloons on cable. I imagine stages or at least a special construct for the upper platform are neccesarry becus you dont want to loose to much He. Cables if any, would firstly lead to the balloon platform (that should be huge)
perhaps spacecrafts can be launched from (rocket)propulsed balloons upthere, wich would allow for a smaller platform.
Is there a space in the non-tether solutions for Lofstrom's idea to be mentioned? I rather like it. Midgley 18:59, 16 March 2006 (UTC)
I was just wondering, how far one could see the elevator if such a thing would be constructed? —Preceding unsigned comment added by 212.149.214.123 ( talk • contribs)
Depends on a number of factors, really. Time of day, how refractory the outer layer of the ribbon is, the ultimate dimensions, weather, angle of view, etc.
We think the ribbon - on the first generation SE - is going to be a meter wide (average) and paper thin. Depending on your angle you'll have a hard time seeing just the ribbon more than a kilometer away under optimal conditions. Bdunbar 21:30, 24 March 2006 (UTC)
At time of writing, the article used 5.294e10 m^2/s^2 as the factor in the taper ratio calculation. However, substituting values in to the equation ( [1]) seems to give a value of 4.832e7 m^2/s^2.
Also, in (J. Pearson, "The orbital tower: a spacecraft launcher using the Earth's rotational energy" in "Acta Astronautica" vol 2 pp. 788, 1975) Pearson uses the equation:
where . Substituting h into the equation gives:
and
[2] gives 4.840e7 m^2/s^2, which agrees with the figure of 4.832 given above (the difference is because the factor of 0.776 is rounded). I shall change it myself and reference Pearson's paper, but I'm placing justification here for future reference.
Someone42 12:10, 18 April 2006 (UTC)
Um, what exactly is "magnetospheric braking of the cable to dampen oscillations"? -- Simonf 05:21, 17 May 2006 (UTC)
I removed this from the article:
"A lunar space elevator would need to be very long—more than twice the length of an Earth elevator, but due to the microgravity of the moon, can be made of existing engineering materials." -- The word was linked to the Microgravity article. If anyone had read it, they would have known that it was the wrong word to use here. Ravenswood 18:30, 23 June 2006 (UTC)
According to The Guardian [3], NASA will be inviting bids to build a space elevator, during this month (September 2006). If this is true, this is exciting news, however I didn't realise current technology is ready yet. The Guardian didn't state its sources for this report.
This really isn't a current event. We may expect significant updates maybe every few months. But this doesn't make it necessary to view it as a current event surely? Barnaby dawson 21:14, 3 September 2006 (UTC)
In the hazards, there's no mention of the possibility of airplanes or such to crash into space elevators... There should be, shouldn't there be?
The cable thickness equation is summarized as follows:
This equation gives a shape where the cable thickness initially increases rapidly in an exponential fashion, but slows at an altitude a few times the earth's radius, and then gradually becomes parallel when it finally reaches maximum thickness at geostationary orbit.
As a casual reader (me), the word "parallel" makes no sense. How can the cable thickness go from "increasing rapidly" to "slows" and then to "parallel?" Parallel to what? Please adjust. JM 216.165.146.161 07:28, 28 September 2006 (UTC)
This is seriously disappointing how often the word centrifugal is used in this article, whereas centripetal is used only once. I have neither the time nor the degree of concern necessary to make the appropriate changes to this featured article, but let it be known that there is no such thing as centrifugal force. Look at the first bullet under centrifugal's article and you'll see the words "Pseudo or fictitious." Please, please, please, when talking about matters of science such as the space elevator use the term centripetal. And yes, I am aware of a device called a centrifuge, but it does not use centrifugal force, contrary to what the Wikipedia article may say. Wikipedia is not, after all, the sole responsiblity of the respectable scientific community. It uses centripetal force. The word 'ain't' made it into the dictionary only by frequent batteries of misuse. Those of you responsible for Wikipedia's contents, please find it in your hearts not to let the whole centrifugal situation get any worse than it has gotten.-- Spawnofbusey 23:32, 16 October 2006 (UTC)
Am I the only who thinks this article is far to long? When it gets to the point that editing gets slow it is well beyond what it ought to be. Nobody sits down and reads through all this. I would recommend that some sections were moved into their own articles and that there was a much shorter section about them here(as hs happened with Space elevator economics). Elentirmo 00:26, 14 December 2006 (UTC)
Reference #16 says it's a 404 error at the location it was originally found. However I found it here, should I update the link even though it's not on a NASA website? Grant 19:18, 3 January 2007 (UTC)
I wandered away from this article for a while to do other things but I think a major problem I raised in #About this word 'Plausible' is still unresolved. The intro paragraphs for this article talk about how all sorts of structures that reach from ground to space fall under the classification "space elevator", and then there's an "orbital tether" header and everything after that reads like a separate article on just orbital tethers. Basically, there are two separate articles on two different topics that are spliced together in one page. My proposal before was to split off the orbital tether section into its own article ( orbital tether), leaving space elevator as a general overview of the various concepts, and although objections was raised they were very nonspecific as to what was wrong with the idea. Does anyone have any other solutions to suggest, or specific details as to why my proposed solution is bad? Bryan 20:13, 14 January 2006 (UTC)
I more or less did this once already, and people reverted it. I didn't call it orbital tether I called it 'beanstalk'; but otherwise that's what I did. I think there's enough people that think that space elevator == beanstalk/orbital tether that it won't fly.
Besides who says that space elevator really isn't just a beanstalk? Is a space fountain actually a space elevator? Is a space elevator a structure that reaches space or is it just another name for a beanstalk? Near as I can tell wikipedia has a significant chance to define what 'space elevator' exactly means here. It's not totally clear. WolfKeeper 21:03, 14 January 2006 (UTC)
Cut the teather... Let the lift fall to space. No energy needed for it to reach space other than the couterweight! Construct a Lift Station in space that controlls the teather so the shipment and the couterweight do not fall into space.
O --- Lifting Couterweight | | --- Lifting Cable | ------------- | | ------ Lifting Station ------------- | | | | | | ------ Station Teathers | | | | | | | (=====) | ------ Cargo | | | | --------------------------------
Lifting Station controlls rate of Lifting Cable passed through it. Multiple teathers attach Lifting Station to the ground, station is and acts like its own couterweight. Guides can be attached to station teathers to controll cargo as it heads toward space. In the event of the lifting cable breaking the cargo would not fall to space or earth by safety devices that can be placed in these guides. Station would also be able to assist in getting the cargo going in the direction it needs to be going after it reaches space. —The preceding unsigned comment was added by 71.8.208.173 ( talk • contribs) 19:46 UTC, 5 June 2006.
I was at a talk about carbon nanotubes a while ago and the speaker mentioned that they would be a likely material to be used if a space elevator was ever built. This is already mentioned in the article. Can anyone back this up with a published source? savidan (talk) (e@) 17:09, 14 June 2006 (UTC)
I believe the diagram is incorrect. It labels the point on the cable which intersects the imaginary line of "geosynchronous orbit" as "center of mass". But wouldn't the center of mass, by necessity, be at an altitude higher than geosynchronous orbit? I would think that no matter how heavy the counterweight is, if the center of mass of the entire system (cable + counterweight + any climbers) falls below the height of geosynchronous orbit, then the entire thing would collapse. Ravenswood 17:12, 21 July 2006 (UTC)
The diagram is incorrect, and most of the language involving the center of mass is as well. The center of mass is nowhere near GEO. It is not expected to, because different parts of the structure experience widely different gravitational and centrifugal acceleration (in the rotating frame). The gravitational acceleration near the surface is much greater than the centrifugal acceleration beyond GEO, meaning the part of the elevator beyond GEO altitude is much more massive than the part below. If you don't believe me, take a close look at the Cable Taper Plot. What needs to balance on both sides of GEO altitude are the forces, not the mass, and less acceleration means more mass. It does not matter, though, because center of mass is not a useful concept for extended objects in an inhomogeneous field anyway. To say "the center of mass is in geostationary orbit" is plain wrong. If I get some consensus, I will edit the text, but I do not know how to edit the diagram. Andreas 20:00, 13 June 2007 (UTC)
The article currently contains the following paragraph:
I had to read this three times before I understood what it was trying to say, and that only because the vision of a paper streamer in the wind suddenly popped in my mind. This is screaming for a visual illustration... linas 04:49, 11 December 2006 (UTC)
How can the slowing of the earth caused by the existence of the lift only 'insignigicantly slow' the Earth's rotation? Surely any slowing of it's rotation is a very bad thing and would need some form of countermeasure? The fact that this topic was skimmed over in the wiki gave me cause for concern. 129.11.76.215 09:04, 1 March 2007 (UTC)MrLaister
Like the title says, I'm wondering if there is any information on the hanging tether idea. It's basically the same idea as the normal elevator, but is only 4K long (with COM at 2km), and the Earth end of the cable has a sky-hook/platform for rockets to transfer cargo to the elevator. I understand that it's being developed for the next X-prize, but I only have Japanese language sources on it so I don't want to add it to the article. Anyone know anything about it? -- Bakarocket 17:01, 6 March 2007 (UTC)
I'm intrigued by the idea of a space elevator. But surely there are similar applications that would cost far less to implement and should be mentioned in this article. Off the cusp, I can imagine a space pump for ridding the world of gaseous, solid, and nuclear waste. We could pipe all our waste to a network of regional pipes that could then be ejected through a central space pump into outer space. Obviously, the harmful waste would have to be ejected with a sun-bound trajectory so it would be incinerated. Bet that would put a significant dent in our polution and waste problems. Moto 02:31, 10 March 2007 (UTC)—The preceding unsigned comment was added by Teeroy ( talk • contribs) 02:21, 10 March 2007 (UTC).
Partly as a matter of interest and partly because maybe it should be added to the page, does anybody know how elongation and deformation from tension (and maybe even tidal forces) would affect the calculations? —The preceding unsigned comment was added by 207.112.60.14 ( talk) 00:01, 29 March 2007 (UTC).
Ok, I looked into a little more. If you look at the Pearson article (reference number 7 i tihnk), on pg. 10 he has a discussion on elongation. When the tower stretches, more of it is passes geosynchronous orbit which, in turn, stretches it more. For a tensile strength/Young's modulus of .0482 he gives a stretch of 5%. Nanotubes have ~.06 which would give an even higher stretch. Unfortunatly I didn't see this mentioned in any of the other article so I'm not sure what the deal is. 207.112.60.14 04:08, 29 March 2007 (UTC)Yonni
Anyone? —The preceding unsigned comment was added by 24.168.30.85 ( talk) 01:25, 29 March 2007 (UTC).
I've removed these from the article - hopefully someone out there is involved in maintaining the article who can deal with them. I hate to see these tags on a featured article, and the onus is really on whoever added them to provide a reference. Richard001 08:51, 5 April 2007 (UTC)
It's been a while since I posted this, so can no one provide any answers to the questions I was asking? I think it's needed, if not for myself, then for the article. -- Hibernian 23:22, 14 July 2007 (UTC)
I am not an expert on the subject but seeing as no one else has adressed your questions I will try. I assume it will get into Space like the ISS, in pieces and assembled in space. An asteroid can be any size at all. For the third, you might want to read the source. 10max01 23:31, 14 July 2007 (UTC)
Your answer seems pretty adequate. 10max01 00:37, 15 July 2007 (UTC)
86.137.107.103 19:18, 29 September 2007 (UTC)== Cable taper plot ==
The cable taper plot shows a wildly different area ratio at GEO to that quoted in the text for steel (about 1.8 versus about 10^14). What assumptions is the plot is making about the type of material used? Are these in any way reasonable? I think that this discrepancy needs to be explained in the article. Matt 13:06, 6 August 2007 (UTC).
Using a value of 2GPa for the tensile strength of steel and density of 8000kg/m3, the equation says that the area at geostationary orbit should be on the order of 10^80 (area at ground level of 1cm2). Unless my arithmetic's gone wrong, I think that the thickness at GEO for steel should be changed. Concerning the taper plot, the inverse strength-density scale isn't all that useful - most materials seem to have inverse strength density ratios of orders of magnitude lower than this, so the ratio Area/Ao would be orders of magnitude higher for most materials. Essentially, the cable taper plot is correct, but not particularly useful - if anyone knows how to extend it for other materials, that'd be very useful.
86.137.107.103 19:18, 29 September 2007 (UTC)
The notion that removing a few km of cable from the bottom of the elevator makes for great savings is just wrong. According to a very simple finite element analysis spreadsheet by Bob Munck (available in the yahoo group), the bottom 100 km of a 20 ton payload elevator weigh just ~400 kg. So, by building a 100 km tower you will save ~2% of capacity, or 2% of cable material. I would call that insubstantial, compared with the expense and plain impossibility of such a tower. The problem here is that antiquated notions from the earlier SE work (towers, asteroids, etc. etc.) which have since been outdated by Edward's work have somehow lodged within this article and need to be cleaned up. I suggest removing most references to towers or elevated locations except for one place where this is explained. Andreas 06:21, 13 June 2007 (UTC)
I am aware of No Original Research, though I reckon that it must be the case that someone has already published what I am stating here, and hence that the information is citable. But, would strategically placing Helium Balloons at certain points along the tether aid the feasibility of creating the elevator? I believe that this might be so as the tension along certain points of the tether would be reduced via the use of such balloons (they would relieve the tension of the tether from under it's own weight at several strategic points along the tether). However, this is only something that could be done up to a height of about 20 miles up (the height to which most helium balloons will go. You might be able to squeeze out some more height using Hydrogen. It may even be possible to create several mile high rigid `floating structures' attached to helium/hydrogen balloons that could support the tether 30 miles up or so by attaching so structures to such balloons. Nevertheless, I remain pessimistic that the (600 mile?) barrier for fully fledged space access is traversible from such meagre heights (though, in actuality, this outlined approach might be more feasible than the space elevator AND overcome a significantly large proportion of the energy costs requires for getting into space).
If I have made an error in my reasoning, I would sure like to know.
Also, perhaps (solar powered?) magnetic sails (that force against the Earth's magnetic field) could be used to reduce the weight induced tension along several points of the tether? Perhaps more conventional thrust generation methods would relieve the tension allowable for a greater flexibility in material utilisation?
A general point could be that the space elevator doesn't really need to take up into space at all in order to be economically viable – it just needs to get us 10% of the way up (aren't most of the energy hurdles in relation to leaving the Earth's gravitational field used up in making the first small proportion of the distance?).
I have not done any calculations when making this post – though I do believe that the approximate figures given are unlikely to be terribly incorrect in principle at least.
ConcernedScientist 01:22, 30 June 2007 (UTC)
(Consider F=BIL, and a long superconductor on a moving air based platform to see that Carbon Nanotubes might not be absolutely necessary).
Anyhow, forgive my rambling, all of this is probably WP:NOR bound, so I'll stop making a mention of these ideas (though I doubt that they're Original Research as they are so obvious that someone must have posted them some time ago...).
ConcernedScientist 00:59, 15 July 2007 (UTC)
I believe balloons will not significantly improve the economics of the Earth/GSO cable configuration. Cable materials can be characterized by the length of a uniform cable that can just sustain itself against gravity without breaking, essentially l = (T/(g*rho)), if l is the characteristic length, T is breaking tension, g is acceleration of gravity, and rho is cable material density. For a tapered cable near the surface, the area must grow by a factor of e every time you go upwards by l. If I recall, l is on the order of 10 km for ordinary steel cable.
Unfortunately, the effective potential height of the Earth's gravitational potential well is about 5,500 km (again "if I recall"). So for steel we get an awful factor, of exp(5500/l) = exp(550) or so. This effective potential is the depth of the gravitational energy well of the Earth (which is just the radius -- about 6380 km for Earth -- for any spherical planet, since the 1/R^2 force's potential is -1/R) after taking into account the opposing centrifugal force, integrated from the surface to GSO. So, it reduces the problem from about 6380 km to ~5500 km, not a huge effect.
Near the surface, the gravitational acceleration is g ~ 9.82 m/s^2, so the potential height is essentially the same thing as the geometric height, 1 km per km. Thus what kills you is the region between the surface and 1 radius or so, where you have the bulk of the effective potential height that has to be overcome. Because the atmosphere is thin, scale height ~10 km, balloons won't work high enough (50 km is about their limit) to have much of an effect (just as shortening the cable by say, 50 km, so that the end dangles above the atmosphere, does not really help either).
The good news in the horrible exponential is that, IF you can find a material with a much better l, you can get a colossal reduction in the mass and a corresponding improvement in the economics. As far as I know, single-wall carbon nanotubes have the best l known to date, I believe the figure is over 1,000 km. Unfortunately, they are not yet available in quantity with uniform quality and sufficient length. I believe spinning such fibers into multi-strand yarns or cables is probably the way to go, but as far as I know it is still just an exciting possibility.
A comment here from someone in July 2007 attacked carbon nanotubes, but (while I am by no means an expert) the theoretical l numbers measured for some of them seem to make them the material of choice. I will try to provide better documentation from the literature as soon as I can, if it has not already been done by someone else. (Being new to this article I need to read it all carefully, and the discussion too.) Wwheaton ( talk) 08:15, 18 December 2007 (UTC)
I replaced the SVG diagram of the elevator with the original PNG one, because the SVG showed the elevator to go up from the north pole, which is nonsense. Many people don't intuitively understand why it has to go from the equator, because many don't understand the idea of an orbit. 79.120.55.7 07:01, 20 September 2007 (UTC)
In the "Construction" section, there is a reference to "Five Key Technologies for Future Space Elevator Development". The Smitherman paper mentions 7 low-TRL areas, which don't match up with the 5 in our article (Smitherman doesn't mention towers for example, but they feature in several of ours). Perhaps there is another NASA study from which those 5 were taken. Kingdon 23:03, 9 October 2007 (UTC)
"In an ideal cable, the actual strength of the cable at any given point would be no greater than the required strength at that point (plus a safety margin). "
Shouldn't it say less than?
Good article, however a discussion of the reasons why an elevator isn't being built right now is missing. What challenges are ahead? Are there any problems associated with making the ribbon? The article primarily deals with what an elevator would look like, if it was there. -- Oz1sej ( talk) 10:32, 23 November 2007 (UTC)