Talk:Space elevator/Archive 1

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Removed: NASA and the European Space Agencies should definitely start production of these space elevators if we are ever to exist as a race off of this planet, so that we dont put all of our eggs in one basket. Otherwise, this is great stuff! --MichaelTinkler

Whups. I got some of the text off of a NASA web page, I guess I didn't edit it carefully enough. :) I'll check it some more for NPOV now.

To answer the next question I'm sure a lot of Wikipedians will now ask, yes, the text is pretty much verbatim from an external source, which is usually a big no-no. I can't find an explicit copyright statement on the pages. But the page in question is part of NASA's "project liftoff", which is a fully tax-funded educational project, and is hosted on nasa.gov, which is tax-funded site, and while NASA makes a bit of noise about being a semi-independent non-government entity, recent court decisions have made it clear that they are an agency of the government with regard to regulations covering agencies of the government (they are subject to FOIA, for example), so it appears that we are safe from copyright problems. --LDC

Please quote a link to the page used as the basis of the article. Paul Beardsell 12:13, 1 May 2004 (UTC)

Good to hear a second opinion confirming my understanding of the situation. I did a bunch of editing on it as well, it'd be annoying to have it turn out to be illegal after all. :) -BD

How about using fibers made of synthetic spider silk protein? I heard spider silk is stronger than kevlar.

Unfortunately, I'd bet protein-based cables wouldn't hold up very well in the vaccum and hard radiation of space. Not to mention that spiderwebs have a high liquid-water content, necessary for their springyness and flexibility. A pity since it'd be really cool to string spiderwebs into space like that.

Shouldent this article contain some scepticism about space elevators e.g the potential downsides/risks/practical problems of a space elevators. This article reads like a space elevator promotion article at the moment G-Man 16:48 29 Jun 2003 (UTC)

Added a section on failure modes, is that the sort of thing you were thinking of? Bryan

The NASA report (http://flightprojects.msfc.nasa.gov/fd02_elev.html) (this link does not work) had a neutral discussion of the pros and cons. Astudent 05:19, 2003 Aug 16 (UTC)

"Artsutanov suggested using a geosynchronous satellite as the base from which to build the tower. By using a counterweight, a cable would be lowered from geosynchronous orbit to the surface of Earth while the counterweight was extended from the satellite away from Earth, keeping the center of mass of the cable motionless relative to Earth. Artsutanov published his idea in the sunday supplement of Komsomolskaya Pravda (Young Communist Pravda) in 1960."

Call me dumb, I can't seem to get the counterweight thing. Where would the opposing force (away from Earth) origin? I know some basic newtonean physics but this sounds weird unless there's some propulsion system (or another planet with sufficient gravity) to pull the (long!) extention towards space -- Rotem Dan

The opposing force is centrifugal. By extending the counterweight outward from geosynchronous orbit using a cable, the counterweight is forced to keep moving at geosynchronous velocity despite the fact that an object orbiting at that radius would be moving slower. The counterweight is thus moving too fast for its orbit and wants to fly away from Earth, but the cable that hangs downward prevents this. Bryan

Thanks, I think I got it (I was confused with the centripetal force but now it makes sense; <yeah I'll work on my physics on the next semesters>). This is a very interesting trick! also nice work on the failure points. Cheers -- Rotem Dan

Regarding cutting the space elevator at the anchor:

In Bradley Edwards' space elevator design, the ribbon is balanced so if it is cut at the anchor, it would not move. I found this quote from Newsweek: "What’s to keep the whole thing from flying out into space or crashing down to Earth? The upper half of the elevator gets thrown outward [by Earth’s rotation], and the bottom end is pulled down by gravity. Even if you cut it at the bottom, the ribbon would just float there." Going Up? - Newsweek Astudent

That looks drastically oversimplified to me. If you have a space elevator that is exactly balanced, so that the weight of its lower portion is pulling downward with exactly the same force that the counterweight is pulling upward with, then as soon as you put any additional weight at all on the bottom end there will be more force downward than there is upward. The elevator will be pulled downward as a result. This would result in a catastrophic failure since moving the counterweight inward reduces the centripetal force, which accelerates the fall of the elevator. Without drastic measures such as cutting a large section of the lower end off to reduce the weight of the lower portion, the entire space elevator will fall down to Earth's surface. I suspect that Edwards is oversimplifying for MSNBC's benefit; he probably just means that if you cut the elevator it won't fall down to the ground. Bryan

Thanks for your reply. I was wrong earlier about the exactly balanced ribbon. Your explanation is very good. Astudent

No problem. Orbital dynamics aren't very intuitive even for conventional orbiting objects, let alone ones tied to the ground. :) Bryan

True, but we were only talking about cutting it. You wouldn't put a cargo going up on a cut cable, as that would cause the whole thing to fall.

Operationally, you'd need weights that you can move up and down on the out portion of the cable, so that you could lift cargo. You'd probably want some type of linear induction motor thingy, so you could just move weight up and down on that section, depending on whether you were lifting anything from earth's surface at that particular point in time. You're probably always want it slightly imbalanced pulling against the earth's gravity (long-term loss to earth's rotation and other problems not-withstanding), or a very fast response system, so that someone coming up and yanking on the cable doesn't cause it to crash.

~ender 2003-11-13 19:32:MST

This article says "geosynchronous" but "geostationery" is clearly what is meant

According to the article "Geosynchronous orbit" a sattellite with an orbital period equal to the rotation of the earth is geosynchronous. Only if it orbit is above the equator it's also geostationery. If its orbit is not above the equator it oscillates in the sky (I don't know if it moves in circles in the sky or if it only moves back and forth).

In this article about space elevators it is clear from the text geostationery is meant but I see most of the times geosynchronous. I don't know if the sources use the word geosynchronous or if the people that added the text accidentally used geosynchronous instead of geostationery.

If in one or more sources it is called mistakenly geosynchronous there, it should be mentioned in this article I think.

Anyway if I'm not mistaken geosynchronous should change to geostationery everywhere in this article. As I'm not sure how it's called in the sources I won't change it.

I'm really sorry I'm not in the mood to check all the sources. I hope someone else can do that. Laudaka 04:47, 15 Feb 2004 (UTC) (Paul/laudaka)

Actually, in both The Fountains of Paradise and Red Mars, the space elevator on Mars is designed to swing back and forth to avoid the moon of Mars (which is much closer than Earth's moon), so technically, it doesn't have to be geostationery. --ssd 05:52, 17 Mar 2004 (UTC)

Well, they were designed to shimmy out of the way of Phobos and Deimos, but they still run essentially straight out from Mars so they still count as geostationary (or to be really pedantic areostationary) -- wwoods 08:42, 17 Mar 2004 (UTC)

Hey, guess what, everyone? I just got this in the mail:

---

Subject: Re: Contact Form from LiftPort- The Space Elevator Company Date: Thu, 11 Mar 2004 10:02:36 -0800

sure, feel free to use our images. thanks for asking, a lot of people just "take" them. :-)

would you please post a link back to us?

when its up, please send me the link so i can look it over. thanks. and thanks for your interest in our project. take care. mjl

On 10 Mar, 2004, at 3:42 PM, Nobody wrote:

> The following was sent > On: 03/10/04 6:42 pm > > Name: Karen Pease > Email: daystar_setting@myself.com

> Comments: > I am interested in whether you would be willing to grant permission to > use one of your conceptual drawings or renderings in Wikipedia (a free > online user-created encyclopedia - http://www.wikipedia.org) as the > illustration for the encyclopedia entry for "Space elevator". > Naturally, the picture would be captioned as being an illustration > Liftport's design, which would get you a bit of free publicity. > > Just let me know - my email address is daystar_setting@myself.com.

> > > > Michael J. Laine President Chief Strategic Officer LiftPort Group

  "The Space Elevator Companies"

245 4th Street Suite 508 Bremerton WA 98337

360.377.0623 - vx 360.824.7394 - fx laine@liftport.com

www.liftport.com

---

I'll get a picture uploaded right away. Would we prefer a drawing or a rendering? I prefer the drawings, personally... Rei

[1] has some images, and I think they're better than some of the ones currently in the article. Since it's a NASA publication, I assume these are public domain? Fredrik 19:05, 17 Mar 2004 (UTC)

Well, I'm not particularly impressed by the pictures in that publication, and the NASA proposals seem a lot less well thought through than the Liftport or HighLift proposal systems (for example, discussing climbing with electromagnetic propulsion without running the numbers, which work out to an incredibly unfeasable amount of extra bulk to the cable). Also, while NASA generally releases everything to the public domain, you still need to ask if it isn't specifically stated. Rei

I thought the state of matters is that *everything* NASA releases goes into the public domain. Fredrik 17:26, 19 Mar 2004 (UTC)

Most of NASA's work is in the public domain, but that doesn't *guarantee* that something that NASA has posted is in the public domain. You still need to ask permission or find somewhere in which the document is declared to be public domain. For example, here on NASA's page about Project ASPEN, they specifically state that their information about it is not in the public domain [2]. You can't just assume. Rei

"NASA artwork of the space elevator ... created by Pat Rawlings" is the attribution. That tells me that NASA owns it. The last page tells me that the publication may be distributed without limitation. I can't find a specific statement that addresses the specific status with respect to the public domain. Apparently public funds paid for it, if that figures into the discussion. - Bevo 18:13, 19 Mar 2004 (UTC)

History: Whose notes were sent behind the Iron Curtain?

In the first History paragraph, the last line says, "His notes were sent behind the Iron Curtain after his death." The context implies "he" is Nikola Tesla, who was a naturalized American citizen at the time of his death and had his papers seized by the FBI for national security reasons. I doubt they went behind the Iron Curtain. Was it instead Russian Konstantin Tsiolkovsky's papers that "were sent behind the Iron Curtain"? If so, it should say so explicitly. -- Jeff Q 05:59, 30 Apr 2004 (UTC)

Impossible

This is now a featured article. Of course it reads very well but the balance is poor - it is all very Popular Mechanics. It would serve Wikipedia well if it were more plain just how difficult a project this is. Cost is almost the least of the problems. Typically a solution to one problem makes another much worse. Paul Beardsell 09:34, 30 Apr 2004 (UTC)

I agree. My first thought when I saw this on the Main Page was, "Wha? Is this really worth a 'featured article' -- a hypothetical engineering problem?" Alcarillo 15:15, 30 Apr 2004 (UTC)

I have done a lot of work to remove the overly optimistic aspect from this article by adding in a lot of the potential pitfalls and pointing out out how far behind current materials tech is from what is needed for a space elevator. I'm surprised that people still view it as being so overly optimistic. --Rei

I think it is great. Very interesting. Congratulations, guys! 198.54.202.2 17:22, 30 Apr 2004 (UTC)

Yes, it is a great article. But, face it, this will not be built ever^H^H^H^H in the next 50 years. It's more likely we blow ourselves up or die of the plague or get hit by a meteorite or the 2nd coming happens first. Well, nearly! That this is entirely speculative needs to be said. We'll have all the gadgets that the Jetsons had first! Paul Beardsell 21:17, 30 Apr 2004 (UTC) I hope the small edit I have done to the article is considered acceptable. Please, as always, revert if you like! Paul Beardsell 21:26, 30 Apr 2004 (UTC)

And that is your personal opinion. And many people at NASA disagree with you about whether it will eventually be built, or whether it is impossible. 50 years? Probably not. However, it is not entirely speculative - NASA, as well as many private organizations, have run many calculations and simulations on it. I have even a cable tension calculator program (spelsim) on my computer right now. It is possible, but will not occur until we can produce materials on the large scale that have tensile strengths that we currently only have on the nano-scale. In short, you must argue that this is an impossible task. If you think so: why?

The burden of showing that this is a practical idea is yours. Start by naming the people at NASA (you invoke them, not me) who think this is a practical idea. Paul Beardsell 23:32, 30 Apr 2004 (UTC)

If you'll note, the article does include all of the potential pitfalls, and where the current level of technology stands on them. If you have any other potential pitfalls please add them; if not, don't complain. --Rei

I am not complaining. All I did was fix the incorrect impression that many/most/all optimists thought that construction was starting real soon now. Do you think that? Paul Beardsell 23:35, 30 Apr 2004 (UTC)

Regretfully (because it is a neat concept) cold fusion is a whole lot more likely. There isn't anything that NASA doesn't have a look at. In this case, to rule it out. Bending forces on the cable as the object is speeded up laterally as it travels up the wire, the mobile anchor to avoid storms, the meteriotes, the corrosion, the dodgy economics (Heck, you cannot send 1KG that distance on the ground for that price!) Allow us Wikipedians some dignity. It's only a tiny change I have done and I have now moderated that further. Don't be annoyed by me. I'm sorry if I am having a go at anybody's pet idea. 212.56.101.83 23:18, 30 Apr 2004 (UTC) I'm sorry I did not mean to be anonymous. That is me. It seems I am not alone and my change has been beefed up by others. Paul Beardsell 23:22, 30 Apr 2004 (UTC)

Economics questions

$3/kg it is claimed. How much does it cost to send 1 kg 38000km horizontally? Why would it be cheaper to do this vertically?

Electricity will be sent up the cable for power. How much power loss is there over 38000km? Or are we relying on superconductivity?

Paul Beardsell 23:56, 30 Apr 2004 (UTC)

When considering how much it costs to send stuff horizontally, bear in mind that to be an accurate comparison you'd have to assume that a perfectly straight and level railroad exists along that path with no adverse weather conditions and no traffic obstructions. The cheapness becomes a little more believable under those circumstances; how much does it cost to mail a 1kg postal package to the other side of the world and back with transportation systems far inferior to that? As for power transmission, a variety of techniques have been proposed in addition to running it up the cable; the elevator cars could carry their own self-contained power source, or (as depicted in the Liftport images currently used in this article) you could beam the power to the elevator with lasers or microwaves. It may also prove more economical to power the elevator system from the top, using a solar power satellite at the geosynchronous station. I don't have any numbers, but as far as I'm aware these matters are still somewhat up in the air depending on your technology assumptions. Bryan 01:23, 1 May 2004 (UTC)

Power source: Solar cells at the top is a possibility but there is still the problem of transmission losses. Containing a microwave or laser beam to a small enough diameter so as it can be picked up by a small enough collector not to be prohibitively heavy is impossible. Beaming that much energy through the atmosphere also has unacceptable power losses. So, it's self-powered cars? We put a jet engine turbine in the elevator car to generate the electricity. Or we direct the jet engine downwards to push it up. And where do we put the jet fuel and the oxygen for the jet engine? It's just a rocket on rails. I suggest we discard the rails. Paul Beardsell 11:41, 1 May 2004 (UTC)

It is in fact quite possible to contain a microwave or laser beam to a small enough diameter for a small collector on the elevator car; you need a larger emitter to focus that small, but since the emitter is on the ground (or geostationary orbit) you can make it as large as necessary. A high-frequency laser would be easier to focus than microwaves due to diffraction limits. As for onboard power sources, why do you suggest a jet engine (especially as a source of thrust rather than electricity)? One benefit of an elevator over a rocket is that you don't need a high thrust-to-weight ratio to launch; you can use low-power but highly efficient power sources instead. You could use a small nuclear reactor, for example, or fuel cells. Bryan 21:01, 1 May 2004 (UTC)

Lateral acceleration (to 3km/s) is more of a problem than hauling the thing up the cable. That cannot be done using a nuclear power source: You need something pushing sideways. Paul Beardsell 06:07, 2 May 2004 (UTC)

The angular momentum ultimately comes from Earth's rotation, which is infinitesimally slowed when a payload goes up the elevator and intinitesimally sped up when a payload descends. Bryan 06:16, 2 May 2004 (UTC)

The angular momentum of the whole system is preserved - there is no infinitesimal change to the whole system. Sure the earth itself has an immeasurable change in its angular velocity. The angular momentum of each KG sent to geostationary orbit is increased dramatically. That has to come from somewhere. A lateral force is required on the mass. Without it we will bend the cable and pull the station out of orbit. Paul Beardsell 06:29, 2 May 2004 (UTC)

The amount of angular momentum gained by the payload moving outward on the cable is exactly the same as the amount of angular momentum lost by Earth. The payload is much, much lighter than Earth, so the same amount of momentum will produce a much, much greater change in velocity for the payload than it will for Earth. Bryan 06:43, 2 May 2004 (UTC)

Yes. But angular momentum must be transferred one to the other! Newton II: A change in velocity requires a force. At geostationary orbit the speed is 3km/s. At the equator the speed is 1 km/s. The force is to speed up the object, the reactive force (Newton III) slows down the earth. Momentum is preserved but work is done! Paul Beardsell 06:58, 2 May 2004 (UTC)

Yes, this force is provided by the tension in the cable. Bryan 07:06, 2 May 2004 (UTC)

Tension is along the cable. We need a force perpendicular to it. Paul Beardsell 07:45, 2 May 2004 (UTC)

The cable tilts slightly when payloads move along it, as I described below. This gives an eastward or westward component to the cable's pull. Bryan 07:54, 2 May 2004 (UTC)

Cost: I think that the $3/kg figure is the marginal cost i.e. the cost of lifting 1 more kilogram. It neglects the cost of capital. Paul Beardsell 11:41, 1 May 2004 (UTC)

I removed this:

Of course, if we assume the same lossless conversion of energy, rockets can deliver payloads for a comparable cost. The use of rockets avoids having to solve the major engineering problems associated with a space elevator. And we can start now without the massive capital outlay. Oh, assuming the same lossless conversion of energy that the economics of the space elevator depends on, of course.

Reasons:

It's written in an informal style
The way it's worded, it promotes rather than presents this point of view
I would like to see some evidence that lossless energy conversion in rockets could be achieved at all and without major, costly engineering and research difficulties

I don't mean to be rude here, and I agree that all aspects of the issues involved must be presented. This particular part isn't substantial in its presentation, however. Perhaps the best solution would be to restructure the whole economics section. Fredrik 13:54, 1 May 2004 (UTC)

OK, I agree with your 1st two reasons BUT the whole article is written in a space elevator promoting fashion. Let's be clear about this: This is an interesting but UNIMPLEMENTABLE idea. Essentially we would be better poking fun, than cosying up to those crank consultancies trying to siphon off their own 1% of NASA's huge budget. Paul Beardsell 15:21, 1 May 2004 (UTC)

As for the third reason: It is the space elevator article which wants to assume lossless energy conversion for itself. I simply would like the same privelege for rockets. Paul Beardsell 15:21, 1 May 2004 (UTC)

Advanced versions of the space elevator can recycle the energy of downward traffic to lift upward traffic. Rockets have no such potential. Talk of lossless conversion simply sets the lower bound on the cost; nobody thinks that could be reached in practice. --wwoods 16:43, 1 May 2004 (UTC)

Untethered Space Elevators

I read on the Internet a while back of a proposal for an untethered elevator. The bottom of the elevator would be in low earth orbit, above wind and lightning. But I can't find my source now. If anyone knows more perhaps they could write something.

Zeimusu 12:20, 2004 May 1 (UTC)

It does not work: The lower orbit has a shorter period than the upper. The lower station races ahead of the upper. They rotate about each other making the whole assembly useless. Paul Beardsell 13:57, 1 May 2004 (UTC)

Not so. There are proposed tether systems which rotate, and others which don't. See tether propulsion for some info. Being much shorter than the space elevator, they are much more likely to be built. --wwoods 16:43, 1 May 2004 (UTC)

I don't know which proposal in particular Zeimusu is talking about, but he may simply be talking about a space elevator that doesn't quite reach the ground. The lower end would be reached instead by a suborbital spacecraft, or if it's low enough perhaps a high-flying aircraft, either of which would be much cheaper than a spacecraft that had to attain orbit on its own. Bryan 20:45, 1 May 2004 (UTC)

A low earth orbit space elevator is discussed in this conference publication from the external links section. Fredrik 20:58, 1 May 2004 (UTC)

Of course, it is possible to arrange that, for a short while, the lower station and the upper station are positioned one above the other on a radius to the centre of the earth but this is a dynamic equilibrium, not a stable one. As with any dynamic equilibrium the one above the other positioning on a radius to the centre of the earth would require active management. With computers and small impulse engines this can be managed UNTIL...

...we send something up (or down) the elevator. Then the mass of the elevator (which will be many 100's of tonnes) does not only have to be lifted against gravity (a problem which no one here is ignoring) but also (de-)accelerated to the same velocity as that of the other station. This requires lateral forces which could be provided by a rocket engine but that will require fuel and oxygen to be carried on board the elevator (hence the 100's of tonnes - the same amount of fuel as a rocket not on rails would require). The lateral forces cannot be supplied by an on-board nuclear reactor - all that can do us pull the elevator along the cable. This lateral acceleration problem does not only apply fatally to the untethered version of the space elevator BUT...

...also to the tethered version. Any mass taken to the geostationary position needs to be accelerated to the same lateral velocity as the station. This cannot be easily balanced by a descending mass (the cable being pushed sideways in one direction by the descending and in the other by the ascending elevator) because the cable is comparitively very, very thin in comparison to its length and each elevator car will be at a different position on the cable. The cable will be pushed sideways one way and the other. It will bow and snake and pull the station out of its orbit.

Paul Beardsell 05:58, 2 May 2004 (UTC)

In the case of an untethered elevator, yes, it would need to be dynamically rebalanced and the momentum restored. This could be done by high-efficiency thrusters such as ion drives, though, so there's still some benefit there over conventional rockets (hypersonic skyhooks have similar station-keeping requirements). As for the tethered version, the tower would be kept in tension by having its center of mass slightly beyond geostationary orbit. This means it's stable against minor perturbations and the angular momentum can be taken directly from Earth's rotation. No problem there, this is a basic issue that I'm sure pretty much every space elevator study would check before going on to other details. Bryan 06:13, 2 May 2004 (UTC)

OK. I have removed some stuff here I got wrong. It's in the log if you're interested. Paul Beardsell 08:09, 2 May 2004 (UTC)

It happens to the best of us, and if nothing else it lets us know what sorts of misunderstandings may need to be addressed in the article itself. It's too late at night for me to do it now, but tomorrow I'm going to go through the article and see if any of the explanations I used here in talk: need to be inserted there. Bryan 09:11, 2 May 2004 (UTC)

I think you need to do some more basic learning at this point. Ion drives do exist, and indeed have been used in various space missions - Deep Space 1, most famously. Ion drives cannot launch things into space, however, as they don't have sufficient thrust; they're only useful once they've been launched by other means. The cable doesn't need to be rigid to transfer angular momentum to and from Earth; when a payload goes up or down it the elevator tilts very slightly to the east or west, and as a result the tension gains a tangental component that pulls Earth's surface in that direction until everything balances out again. This doesn't apply to untethered elevators because they aren't connected to the ground. Bryan 07:06, 2 May 2004 (UTC)

Wrong way around, if the center of mass is beyond geostationary then it will be moving too fast to be orbiting there. It will want to move outward. Bryan 06:43, 2 May 2004 (UTC)

The further away the slower the angular velocity of the orbit. But if you were right then the result would be the same: Your second favorite holiday destination would be decimated by a lump of useless scrap complete with ion drives. Paul Beardsell 06:52, 2 May 2004 (UTC) OK, I'm wrong here too.

You seem to have a very basic misunderstanding of how orbits work, here. The elevator is moving too fast for its orbit, so it will be thrown outward. Since it's tethered to the ground, this provides tension in the cable. It's just like twirling a weight attached to a string. Bryan 07:06, 2 May 2004 (UTC)

I was (wrongly) referring to the natural, untethered speed of a satellite at that altitude. Paul Beardsell 08:05, 2 May 2004 (UTC)

Avoiding other satellites

That other low earth satellites' orbits will have to be adjusted from time to time so that they do not collide with the cable is discussed in the article. That the same techniques will be used to adjust the orbits of some asteroids is also presumed. But now we have a cable which is being bent side to side by the ascending/descending cars to provide the force to accelerate/decelerate them as they move to/from the geostationary position. Over 38000km I reckon the cable will be deflected by 100m at least - possibly a lot more. How will this all be taken into account when deciding which satellite orbits need adjusting. No longer do we have to worry about a swathe being cut through the sky which is 2m wide but one which is 200m wide. What if there is a glitch of some description and a car is stopped for a few minutes? The deflected cable will swish gently from side to side over 200m. This will be unexpected! What about all those satellites we nudged? Paul Beardsell 19:02, 4 May 2004 (UTC)

A reasonably broad margin of error will be called for, I imagine. Arrange it so that no satellite comes within a kilometer of the predicted position of the elevator, and then you're fairly safe against both unexpected swaying of the elevator and unexpected course deviations by the satellite (within that margin, that is). Air traffic control does this sort of thing all the time; nobody would normally plan a trajectory that only barely misses some obstacle, they'll always try to leave room to be on the safe side. Bryan 01:10, 5 May 2004 (UTC)

Article moderation required

Bryan, first I ought to thank you for taking so much time to explain things to me. I apologise that on one or two occasions some explanations may not have been necessary if I had read the article more carefully. However this is not true for many of the points I have raised: The answers may be obvious to you but not to many otherwise scientifically literate readers of the article. When I make an ill-informed observation this is an opportunity to improve the article. When I make a good observation, likewise.

In my view (but I would say that wouldn't I) the bias is the other way. There seems to be a tendency here to sweep problems under the carpet. Supporters of the concept refrain from criticising points made by other supporters that they disagree with. In the article itself and here on the talk page the choice is presented as if it were uncontroversial: For reasons of the weather either the base must be movable or it must be untethered. Avoiding satellites make the movable base problematic so now it is no longer required.

It seems to me supporters of the concept seem to me to feel free to swap from one set of mutually exclusive proposals to another as they seem fit. This might not be true for any one individual but as a group you are remarkably uncritical of one another. I know there is no group per se!

This is a highly speculative proposal that should be presented in an encyclopedia as such. An introductory sentence does not compensate for the overall tone. This otherwise excellent and highly interesting article needs to be moderated.

Paul Beardsell 12:11, 5 May 2004 (UTC)

But this is simply not true. There's no good reason to move the base or leave it untethered, so the tradeoff that you claim is required simply doesn't exist. Look, I have no problem at all with putting cons in this article as well as pros. I practically wrote the entire "failure modes" section of the article when someone mentioned here that there wasn't anything in here discussing problems the system had. But if you want to talk intelligibly about the problems a space elevator might have then you have to have at least some basic knowledge about how the idea works. Your questions have been useful, they've resulted in some new material being added to the article in answer to them, but your constant harangueing about how we're all being foolish by overlooking "obvious" flaws and that the concept won't work for nonsensical reasons is making me feel quite frustrated and adversarial. If you don't know how this concept works, ask questions to learn about it instead of starting out by trying to lecture people on how you imagine it works. Then perhaps you'll be able to come up with some objections that can't be dismissed by anyone who knows a bit about this stuff out of hand. Bryan 15:32, 5 May 2004 (UTC)

If there is no need for a movable base station why do you not say this in the article? (The article is uncritical of this proposition.) Do not tell only me! As you said, you wrote the failure modes section. The economics section which was wildly optomistic and certainly not NPOV has been helpfully rewritten by another editor and this has been at least partly provoked by me. There was room for improvement and, I think, there still is. I think you respond to my confrontational style, not really to the substance of my points: With one exception (my originally flippant paragraph in the economics section) my wrong/lecturing/nonsensical/haranguing (select any of your epithets) contributions have been confined to here, to the Talk page. To educate myself about space elevators I could consult an encyclopedia: Wikipedia fell open at this article one day and I was entertained by the article but some of my questions were not answered by it, some facts seemed wrong (they might have been right but not obviously so to the scientifically literate albeit elevator-ignorant reader) and some "facts" were wrong. You put me in a catch 22 situation. But I acknowledge my style may not have helped. Paul Beardsell 16:27, 5 May 2004 (UTC)

I do thank you for confining this argument to talk:, if it had been taking place in the article itself I would have lost my temper long ago. Even as it is I've let my frustration get to me more than I should, sorry about that. Perhaps you could try making a list of the details that you feel the article still doesn't go into enough detail about, and we could go from there? Bryan 01:52, 6 May 2004 (UTC)

Take a break

For God's sake, Psb, every single time I try to reply to a comment, I get an edit conflict and you've already posted half a dozen more. I can't take this. Instead of asking us questions, go read a report on the physics and economics involved instead of harassing us here. I'm out of here until you calm down. Rei 18:03, 6 May 2004 (UTC)

You invoke your supernatural being, I'll invoke mine. Just have a look at the log.

(cur) (last) . . 19:13, 6 May 2004 . . Psb777 (=Take a break =)
(cur) (last) . . 19:08, 6 May 2004 . . Psb777 (=Cost per kilogram= shout me down, why don't you)
(cur) (last) . . 19:03, 6 May 2004 . . Rei (Take a break, Psb!)
(cur) (last) . . 19:01, 6 May 2004 . . Rei
(cur) (last) . . 18:58, 6 May 2004 . . Psb777 (=Economics questions= lossless misleading)
(cur) (last) . . 18:49, 6 May 2004 . . Rei (=Cost per kilogram=)
(cur) (last) . . 18:28, 6 May 2004 . . Psb777 (=Economics questions= Lighten up, Rei.)
(cur) (last) . . 18:09, 6 May 2004 . . Rei (=Economics questions=)
(cur) (last) . . m 15:51, 6 May 2004 . . Psb777 (=Economics questions=)

You exagerate just a little. Multiply by 0.5%, why don't you. My edits have also been plagued by conflicts. I'm glad you're taking a break. Paul Beardsell 18:13, 6 May 2004 (UTC)

I'll step back in just quickly to correct Psb's "truncation":

(cur) (last) . . 18:16, 6 May 2004 . . Psb777 (=Take a break=) (cur) (last) . . 18:13, 6 May 2004 . . Psb777 (=Take a break =) (cur) (last) . . 18:08, 6 May 2004 . . Psb777 (=Cost per kilogram= shout me down, why don't you) (cur) (last) . . 18:03, 6 May 2004 . . Rei (Take a break, Psb!) (cur) (last) . . 18:01, 6 May 2004 . . Rei (cur) (last) . . 17:58, 6 May 2004 . . Psb777 (=Economics questions= lossless misleading) (cur) (last) . . 17:49, 6 May 2004 . . Rei (=Cost per kilogram=) (cur) (last) . . 17:28, 6 May 2004 . . Psb777 (=Economics questions= Lighten up, Rei.) (cur) (last) . . 17:09, 6 May 2004 . . Rei (=Economics questions=) (cur) (last) . . m 14:51, 6 May 2004 . . Psb777 (=Economics questions=) (cur) (last) . . 14:43, 6 May 2004 . . Psb777 (=Economics questions= regeneration hampered by transmission losses?) (cur) (last) . . 02:02, 6 May 2004 . . Psb777 (=Avoiding other satellites= dodgems) (cur) (last) . . 01:52, 6 May 2004 . . Bryan Derksen (cur) (last) . . m 00:23, 6 May 2004 . . Psb777 (=Cost per kilogram= fmt) (cur) (last) . . 00:04, 6 May 2004 . . Psb777 (=Cost per kilogram= rocket launch cost per kg payload) (cur) (last) . . 23:40, 5 May 2004 . . Psb777 (=Cost per kilogram= cost of propellent) (cur) (last) . . 18:13, 5 May 2004 . . Psb777 (=Cost per kilogram= cut'n'paste) (cur) (last) . . 17:40, 5 May 2004 . . Rei (cur) (last) . . 17:30, 5 May 2004 . . Rei (Geez, Psb, give me a chance to respond.) (cur) (last) . . 17:19, 5 May 2004 . . Psb777 (=Cost per kilogram=) (cur) (last) . . 17:18, 5 May 2004 . . Psb777 (=Cost per kilogram= invitation to explain reversion) (cur) (last) . . 17:16, 5 May 2004 . . Psb777 (==cost per kg==) (cur) (last) . . m 17:08, 5 May 2004 . . Psb777 (=Economics questions= clarity) (cur) (last) . . 16:57, 5 May 2004 . . Psb777 (=Economics questions= please look at kid with marbles homework) (cur) (last) . . 16:47, 5 May 2004 . . Psb777 (=Economics questions= kid with marbles doesn't know his acronyms) (cur) (last) . . 16:44, 5 May 2004 . . Psb777 (=Economics questions= kid with marbles responds) (cur) (last) . . m 16:30, 5 May 2004 . . Psb777 (=Article moderation required=) (cur) (last) . . 16:27, 5 May 2004 . . Psb777 (=Article moderation required= style vs substance)

And that's only for the talk page. Psb, can you not understand why people get sick of someone who hasn't even read a paper on the subject trying to take over an article? Rei 19:14, 6 May 2004 (UTC)

I quoted from the log to show that over the period that Rei was saying he was experiencing edit conflicts that he was making as many edits as me. It is true that I made numerous small edits earlier but that is just not relevent. Rei wasn't here then. Paul Beardsell 22:42, 6 May 2004 (UTC)

This page is getting awfully big; anyone object to removing discussions which are no longer active? --wwoods 18:14, 7 May 2004 (UTC)

Please, go ahead, hide as many of my earlier misconceptions as you can manage. Paul Beardsell 18:25, 7 May 2004 (UTC)

Go ahead. :) Rei 19:11, 7 May 2004 (UTC)

plea for politeness

My yesterday's change to the economics section has been reverted by Rei. Please explain why or I will revert back .... Refrain from ad hominem attack, please. Paul Beardsell 17:18, 5 May 2004 (UTC)

Some people seem to be straining to reach the conclusion that something must somehow make space elevators impossible to operate. Before you do that, consider reading Edward's report: [3].

Is there something crucial in Edward's report that the Wikipedia article leaves out ?

discussion trimming

/Archive 1 - Prior to May 8 2004

Okay, I trimmed it down to only 62 k. I don't think I cut any live discussions, but you can check the page history, and copy & paste it back if necessary. --wwoods 08:00, 8 May 2004 (UTC)

I wonder if it would be better to split this article into 2 or more parts somehow ? Perhaps a detailed economic exploration of a "simple" "basic version" (up-only, unmanned, etc.), and another page listing all kinds of variations and additions ("advanced version") and history. DavidCary 17:23, 11 May 2004 (UTC)

I agree with Paul Beardsell that we need to compare apples-to-apples; do we need 3 seperate economic analyses to compare

* satellite to LEO: rocket vs. elevator
* satellite to GEO: rocket vs. elevator
* human payload to LEO: rocket vs. elevator

? -- DavidCary 17:23, 11 May 2004 (UTC)

The elevator doesn't really go to LEO -- it goes to GEO, and beyond. --wwoods 00:24, 12 May 2004 (UTC)

advanced versions

Regeneration is hampered by transmission losses. Elsewhere these are said to be very high. If the 0.5% efficiency figure is used again then it is almost not worth bothering. Or is there another flaw in my thinking? Paul Beardsell 14:43, 6 May 2004 (UTC)

Will we build the advanced version after we have built the basic version? To solve other problems we have people suggesting here we detach the cars at the top to send them back. Is that a feature of the the basic version? And the energy you have to recover is not only the up/down potential energy but the sideways kinetic energy. Any plan for that? Paul Beardsell 06:23, 2 May 2004 (UTC)

OK, I've reworded the section. I believe it now incorporates both views without making a stronger case for either. Comments are welcome. Fredrik 16:19, 1 May 2004 (UTC)

Yes, much better balanced. Thanks. What remains unclear is

whether the now sub-$2/kg figure includes both the energy required for lifting 38000km and the energy required to accelerate it laterally.

whether the capital cost is included

Paul Beardsell 18:43, 4 May 2004 (UTC)

vertical potential energy and sideways kinetic energy

"vertical and tangential energy"

I put some numeric calculations dealing with

up/down potential energy
sideways kinetic energy.

at http://c2.com/cgi/wiki?SpaceElevator .

Want me to move them here to wikipedia ? -- DavidCary

First off, people need to stop trying to distinguish between vertical and tangential energy.

Why ? -- DavidCary 17:23, 11 May 2004 (UTC)

energy conversion efficiency of the wireless power beam

I agree with Paul Beardsell that "100% conversion efficiency" of the wireless power beam is unrealistic.

Perhaps it would be less controversial / more realistic to

use the conversion number in the Edwards report (1% if I remember correctly)
use the $100/lb figure published at http://isr.us/SEHome.asp?m=1

at least until we get a better estimate of a "realistic" number.

Would it be crazy to stick with the Edwards report of up-only elevators in the economic analysis of a "basic elevator", then add these other nifty ideas and improvements in a later section (perhaps fore-shadowing with "Even neglecting other suggested improvements, this economic analysis shows ...") ?

Can we say the climbers use Beam-powered propulsion ?

operational costs compared to rockets

It is unavoidable that it takes 57e6 N*m = 16 KWh of energy, per kilogram, to move any mass from the ground to geosynchronous orbit (allow me to call this "orbit energy"), no matter how you do it.

The overwhelming reason space elevators are (in theory) far less expensive than rockets is because

rockets have to accelerate their propellant with them.

That's it.

Other reasons (such as

propulsion is more efficient with a larger reaction mass. Rockets use tons of reaction mass to get pretty good efficiencies. The "reaction mass" of the space elevator is planet Earth.

The "reaction mass" of rockets burns up. The "reaction mass" of the space elevator (planet Earth) can be used over and over again.

rockets have to travel at high speeds -- some kinetic energy is lost to air resistance loss

because SE can spread out orbit energy over a longer period of time (days instead of minutes) means don't need to pay (at $10,000 per pound) for padding you otherwise would need to protect fragile cargo from launch vibration.

) are much less significant.

variations: "run electricity up cable" seems reasonable until ...

As to whether you can just run energy up the cable, that seems pretty unreasonable unless you have a superconducting cable. I've done the math on how much energy will be lost; there's no way it can be done if there is any resistance at all, even if you use silver wire. To power the elevator, you're going to need a lot of power going through it, so even with superconductors, weight is a definite issue. For a quick calculation, if your wire weighs only 10 grams per meter, that's about 358 metric tons worth of cable that you have to support. It would take a truly incredible space elevator to be able to support that kind of weight.

Edward's design has the "initial cable" has a mass of 19 800 kg, slightly less than a Russian geosynchronous communication satellite. At geosync, it's is strong enough to hold up the rest of the cable hanging "down" with a safety factor of 2.

(Should we discuss "running electricity up the cable" in an article -- rather than this talk page ?)

No ... using carbon nanotubes ... a 20,000kg cable of Edwards' design has a maximum cross section area of 2cm, and with the low density of CNTs, is incredibly light. You do the math of what happens if you try and make it hold a couple hundred tons worth of superconducting cable. That's why you need power beaming. Rei 17:09, 6 May 2004 (UTC)

The lossless conversion number is what should be included; of course there will be loss, but people need to know the lower bound.

There are all sorts of ways to regain energy. If you had lossless energy being spent on the way up, equal up/down traffic, and lossless regeneration/transfer, the elevator's total energy usage would be zero. Noone proposes anything close to this ;) However, since most proposals on how to get energy up to the elevators are incredibly lossy, any energy that you can gain on the way (such as from down-travelling elevators, magnetospheric braking, etc) are a huge advantage. Also, down-travelling elevators need to get rid of energy.

Well, the lower bound is NOT the lossless transmission of energy. Here is an example where you do not have to be a rocket scientist (heck, I've always wanted to use that appropriately) or a space elevator expert to know that the theoretical best efficiency is never 100%. This is what you are implying. The base cost is NOT theoretically lossless. With the best will in the world microwave and laser even in a vacuum is very lossFULL. So it is misleading to suggest figures of $1.74 unadjusted. It is misleading to suggest that the regenned energy is going to make any difference if only a very small percentage of that is recoverable. What I had presumed was that you would not want a misleading article. Paul Beardsell 17:58, 6 May 2004 (UTC)

Lastly, I have to back up the removal of the rockets paragraph. For one, it is incorrect. Energy-lossless rockets don't come even close to the space elevator's economics, because you have to accelerate your propellant with you, you have to travel at very high speeds that suffer severe wind resistance problems, etc. Chemical rockets aren't incredibly lossy when it comes to the amount of energy contained within them to how much thrust you get out of them; they're just an inefficient propulsion method. There's a big difference. For a space elevator, you'd need to have energy wasted at 6,000:1 ratio (or have other major expenses) to be as inefficient as using the most efficient chemical rockets.

This does not include capital costs. This is a baseline. The inefficiencies of the system are discussed elsewhere, such as the fact that our best energy beaming systems get less than 1% efficiency.

Ok, I think I've covered my take on the subject. --Rei

But the capital cost is so huge that it is a travesty to not take them into account when pretending to discuss the economics! How many KG do we have to elevate before we break even against inefficient chemical rockets? Paul Beardsell 20:44, 4 May 2004 (UTC)

The baseline capital cost is mentioned elsewhere in the article as 5by$, which I believe is based on Dr. Bradley Edwards' work. If you want more detail, I suggest you read through Edwards' calculations. The key element is the tensile strength of the cable. While I have some problems with some of Edwards' assumptions, it is a fully calculated and quite detailed work. If a cable with a tensile strength of over 100GPa can be produced, the system will only cost a few billion dollars. The cost of the system rises exponentially if you have to reduce the tensile strength, however; this is also discussed.

So, if we transport 2.5billion kg we will only have doubled the cost per KG to $4/kg. Or if we transport 2.5million kg the cost will be $2002/kg. But if we use the efficiency figure of 0.5% then its $2000(capital cost)+$400(marginal). Or $2400/kg. Paul Beardsell 22:52, 4 May 2004 (UTC)

It seems that as a consequence of me asking questions a number of important clarifications have been made. Possibly I missed a thing or two but some of it was not clear. Paul Beardsell 22:52, 4 May 2004 (UTC)

Cost per kilogram

We must compare like with like. Rei's recent edit changing Bryan's figure of $100 to $1.74 is not valid because it is being compared with the actual rocket launch cost. As 0.5% is considered optmistic the correct figure must be at least 1.74*200 = $350/kg. Despite that this does not include capital costs and so is still understated in comparison to the rocket figure which includes at least some capital cost. I will change the figure accordingly. Paul Beardsell 02:33, 5 May 2004 (UTC)

Um, in a discussion of baselines of a per-lift cost, No You Won't. When one mentions that it takes 10,000$ to lift a pound of mass to LEO on the space shuttle, that 10,000$/lb doesn't include capital costs for the shuttle. Consequently, it is completely irresponsible and completely inaccurate to compare the two. If you want to get into the economics and costs of the entire system, read Edwards' work. Quit acting like an authoritative source when you haven't read a d**n think about the subject. You're getting annoying. It's like having a six year old in a discussion of particle accelerators talking about how they have problems with the concept due to their experience playing marbles. Rei 16:21, 5 May 2004 (UTC)

Shuttle? Araine is $13000/kg (1993 figures) to LEO. To geostationary is $25000/kg (1999), the kid with the marbles reckons. (But if I am the kid with the marbles you are the one attempting to leave the boot marks in his face.) There are plans dating from 1993 which are a lot more feasible than the space elevator to reduce rocket LEO costs to $1300/kg. If the same factor applies then $2500/kg for geostationary. Capital cost inclusive and no major invention required. Compare that to the $2400/kg for 2.5million kg I have calculated for the basic $5bn elevator (and on which I invite criticism). Put that in your economics section. Paul Beardsell 16:44, 5 May 2004 (UTC)

... LEO (Low Earth Orbit). ... Ariane is a lot cheaper than the shuttle. For one, the Ariane series is generally unmanned, although they have been used to launch tests of the Hermes mini-shuttle (which itself notably increases the launch costs, but still cheaper than the shuttle). ...

(we're talking about [4], right ?)

The article you linked is complete and utter extrapolation. It is worthless. I certainly hope this wasn't published anywhere other than his website. This person has no clue what makes rocket launches expensive, and thinks that it is just a "quantity of production" issue. It's not. The propellants are already mass produced. Much of the skin and some of the internal components are simple mass-produced material, and won't gain much from automation. The shuttle costs $500-600m *per turnaround* to launch. This isn't "repaying capital costs" - this is what is needed for the inspections, replacing the parts that are designed not to survive, paying for all of the fuel, etc. Even if you go to disposable vehicles, you're not saving yourself a ton. The orbiter only costs 1.3-2b$, but is designed for over 100 missions. The construction capital cost is already low. And with its capacity for 25,000 kg to LEO, even with the most pessimistic numbers, the capital cost is only 800$. It's the per-launch cost that costs a fortune. It costs almost a million dollars just to carry the shuttle across the country.

Let's put it this way: each of the external boosters carry 453,592 kg of propellant. The main tanks contain 500,000 gallons of liquid oxygen and hydrogen. Lets guestimate that it is 3 kg per gal; that's then 2 million kg of propellant that you have to pay for on each mission. Are you going to try and claim that this isn't "mass production"? The solid boosters have the following fuel breakdown: 16% atomized aluminum; 70% ammonium perchlorate; 2% fine iron oxide powder; 12% polybutadiene acrylic acid acrylonite binder; and 2% epoxy curing agent. Go ahead - find a way to reduce the production cost. Tell me what it is - and while you're at it, tell NASA - I'm sure they'll be interested. The hydrogen/oxygen burning is more efficient, but as Ariane has made clear, cryogenic tanks are very dangerous.

BTW - when people say that it costs 10,000$ to lift a pound of mass to orbit on the shuttle, that is *NOT* counting capital costs (do the math - I've provided the numbers).

Paul Beardsell 23:40, 5 May 2004 (UTC) supplies some excellent links:

http://www.eere.energy.gov/vehiclesandfuels/facts/favorites/fcvt_fotw205.shtml which says "hydrogen costs ... $1.00-$1.40/lb for delivered liquid hydrogen."
http://www.astronautix.com/props/loxlh2.htm which says "By the 1980's NASA was paying $ 0.08 per kg [of liquid oxygen]" and "In the 1980's NASA was actually paying $ 3.60 per kg [of liquid hydrogen]" and also mentions "LOX/LH2. Optimum Oxidiser to Fuel Ratio: 4.00. ... Density: 0.28 g/cc. ... Oxidiser: LOX. Oxidiser Density: 1.14 g/cc. ... Fuel: LH2. Fuel Density: 0.071 g/cc."

That gives us

LH2 at 0.071 g/cc =~= 270 g/usgallon
LH2 at $3.60/kg =~= $1.63/lb (apparently NASA pays a little more than the average industrial user at the other site)
LH2 at ($3.60/kg) * (270 g/usgallon) = $0.97/usgallon

LO2 at 1.14 g/cc =~= 4 kg/usgallon
LO2 at $0.08/kg =~= $0.036/lb
LO2 at ($0.08/kg) * (4 kg/usgallon) = $0.32/gallon

The appropriate propellant mix (4 g LO2 + 1 g LH2, which eventually produce 5 g H2O) gives an average of

LO2+LH2: (4/5)*($0.08/kg) + (1/5)*($3.60/kg) = $0.78/kg
LO2+LH2 (4/5)*(usgallon / 4 kg) + (1/5)*(usgallon / 0.3 kg) = 0.87 usgallon/kg =~= 1.15 kg/usgallon
LO2+LH2 (calculated another way) at 0.28 g/cc =~= 1.06 kg/usgallon
LO2+LH2 at ($0.78/kg) * (1.06 kg/usgallon) = $0.83/usgallon

I think that's close enough for back-of-the envelope calculation; remind me to do more accurate calculations later. -- DavidCary

Ariane 5 fuel payload = 645000kg. Volume is 430000usgallons. Cost is $94600. Ariane 5 payload is 6000kg. Fuel cost per kg to geostationary orbit is $16. Or $7.20/lb.

Will you tell NASA or must I?

Paul Beardsell 00:04, 6 May 2004 (UTC)

... Third, you've got the Ariane 5 completely wrong. There is the main cryogenic stage, and there are the two solid booster stages, in addition to the upper stage. The cryogenic stage contains 132.7 metric tons of liquid oxygen, and 25.84 metric tons of liquid hydrogen.

So that's 25 840 kg of LH2 * $3.60/kg =~= $ 93 000 worth of LH2, plus a bit more for the oxidizer, comes out to about what we calculated above.

The solid rocket boosters' fuel (aluminum, polybutadine, ammonium, etc) is notably more expensive thant the LOX and LH.

Ooopsies, I forgot all about that. Anyone have dollar figures for that ?

And even with all of this, you're still completely out of whack. Ariane-5 alone does not take human payloads up (and with the cancellation of Hermes, probably never will) (I wouldn't want to ride one, anyway... ). Its payload is notably reduced and costs drasticly increased if you include the ARD (if you want reentry, you need that). Etc. Lastly, you're looking at payload to LEO. You're comparing apples and oranges, and you're looking at the oranges under a microscope and the apples through a fisheye lens. Even with all of that, the Ariane series cost between 10 and 20 thousand dollars per kg to LEO, with the Ariane-5 at 11.8. The Titan series gets better; I'm not a big fan of the Ariane series. The propellant is only a small part of the issue. Rei 17:49, 6 May 2004 (UTC)

Even this boy with marbles, the one who cannot read, knows that LH2 is 280g/usgallon. A lot less than a pound weight per gallon. So get your facts straight! Your vivid imagery does not compensate for being careless! In the article I doubled the cost to $30 fuel cost per kg transported to be safe. I tell you what, let's double it again: It does not destroy the argument. You tell me how much the fuel costs and we'll plug that figure in. Paul Beardsell 18:08, 6 May 2004 (UTC)

Would you mind if I moved this discussion to [Ariane] ... or is there a page about the economics of rocket propellant in general ? Atlas launch costs, shuttle launch costs, [Space Shuttle program], Ariane launche costs, etc.)

Once again, I will ask you: Go read a paper on the subject of space elevators. I would suggest Edwards, but there are a number of good studies out there, so take your pick. Rei 17:30, 5 May 2004 (UTC)

alternative ways to space

By the way: there ARE cheaper ways to get things to space than standard chemical rockets being worked on.

Excellent. Do any wikipedia pages exist for these other ways ?

Yes:

the HARP project, which uses ballistically launched sabot-fired projectiles to get a chemical rocket into the upper atmosphere; it was cheap per launch, the development costs were proportionally tiny, and they were almost to orbit (they had reached the altitude, and had demonstrated that a rocket can survive the launch and fire at altitude; they just needed to apply the proper thrust to make it orbit).

Other methods are things like the high powered coil guns, railguns, and ram accelerators (also with a second-stage rocket); as well as combining any of these methods and/or conventional ballistics with a scramjet engine (and second stage rocket).

However, the space elevator is the "maximum cost efficiency per launch" method physically possible - and it *is* feasable if materials tech advances. Rei 17:40, 5 May 2004 (UTC)

sway

Do you think that the sway will only be 200m? I just guessed a figure. But if the cable is 2m or 20m wide this is a tiny proportion of the length. The cable needs to be light and tension will have to be limited to limit the necessary strngth of the cable. How stiff will the cable be? If the sway is 2km and we want a 1km safety margin either side then it is a 4km swathe being cut through the sky. Space traffic control is going to be very difficult! And the sway could be 20km or more! A 22km swathe would surely be impossible to manage. Every low earth satellite would have to have its orbit adjusted every several hundred revolutions. Every second week!

I answered this one already, but it looks like my answer's been deleted without the question also being removed. Paul's way overblowing the scale of the sway and the magnitude of the space traffic control problem the elevator would present. Next time someone archives this page, please be more careful about how you cut things; this whole talk page has become a colossal mess. Bryan 04:27, 12 May 2004 (UTC)

weather

And then, just as we have it all worked out, the weather forecasters force us to move the base 50km to avoid a storm. So we decide to build an untethered elevator instead but this destroys the economics: All the fuel wasted in rockets overcoming air resistance to get to the base station.

But once we are above the atmosphere rockets are no longer as inefficient and ion drives work: We can take the cable cars off their rails!

I know I'm going to be told I have added nothing knew - that all this is known. But what I am trying to illustrate is that each solution seems to make another problem worse.

Paul Beardsell 01:52, 5 May 2004 (UTC)

...

The sway is smaller the lower you go. If the cable's anchored on Earth's surface, and LEO is only a few hundred kilometers up, you're not going to get more than a few hundred meters sway at most at those altitudes at the absolute maximum - we're talking about extremely small angles here, not something you'd be able to see with the naked eye. At higher altitudes there's huge amounts of space for satellites to maneuver in. You don't seem to appreciate just how big a volume of space is being dealt with, and how tiny satellites and the elevator will be in comparison to that vastness.

...

Bryan 07:31, 5 May 2004 (UTC)

Just a couple comments, Bryan.

I agree completely with your comments about sway in the atmosphere. Sway outside the atmosphere is relatively easy to deal with, assuming that NASA's current work on magnetospheric braking/acceleration pans out (the physics are good; it's currently a materials problem, in that the last time they tried, they had gas leak from the insulation which created a plasma that severed the tether). Not only does braking against the magnetosphere resist momentum of the tether, but it also generates electricity. Even without magnetospheric braking, harmonics can be avoided by proper timing of the climbing craft.

Dr. Edwards did a number of calculations on the effect of weather, and found that such an elevator *is* succeptable to wind even with the tiny cross section that you get using his >100GPa fiber calculations (although his design uses a flat epoxied ribbon, which I find unreasonable; a more realistic design would be a partial hoytether mesh, which would also suffer from wind less and be less succeptable to damage). Nonetheless, the cumulative effect of winds across the entire troposphere can start to have problems when they get close to hurricane force. His solution was not only a moving platform, but locating the elevator in the waters west of the Galapagos, where storms, high winds, and lightning, are incredibly rare and would be relatively easy to avoid.

Interesting, I would have thought most of the equator would be relatively "safe" since tropical cyclones don't form there. In any event, I presume the movement of the platform wouldn't be fast enough to present extra space traffic control difficulties? Bryan 01:52, 6 May 2004 (UTC)

If the platform is moved maybe the satellites don't need to be nudged. Dodgems for the space age. Paul Beardsell 02:02, 6 May 2004 (UTC)

You have to deal with gusts and high-altitude winds, not just sustained surface winds. Also, all storms may be dangerous because of lighting (one interesting suggestion on the HighLift Systems message board, if the conductivity/water buildup on the cable was too high, is to "maypole" the cable near the ground so that there are multiple paths, and the severing of one wouldn't be a showstopper). Rei 18:01, 6 May 2004 (UTC)

above the weather

I agree with your comment about ion drives. The biggest problem with that, furthermore, is the sheer cost of getting them to LEO to begin with, due to the inherent inefficiencies in chemical rocket propulsion. Rei 16:15, 5 May 2004 (UTC)

Review please

I am trying to moderate the Economics section of the article. Rei keeps on reverting my proposed change. I propose the following text. Essentially my changes are (i) a modification to the first paragraph to repair the misleading comparison of the full cost of rocket launches to the marginal cost assuming lossless transmission of energy of elevator lifting and (ii) a new paragraph which essentially points out that unless a helluva lot of mateial is transported the elevator cannot be justified on cost grounds. The proposed text

Economics

With space elevators like this, assuming a 0.5% energy conversion efficiency, materials can be sent into orbit at a fraction of the current costs. Total marginal cost is between $10,000 and $40,000 per rocket payload kg today and this compares to a marginal cost of $350 ($1.74 adjusted by the 0.5% efficiency factor) per space elevator transported kg. The marginal cost of a trip would consist solely of the electricity required to lift the elevator payload, some of which could be recovered by using descending elevators to generate electricity as they brake (suggested in some proposals), or generated by masses braking as they travel outward from geosynchronous orbit (a suggestion by Freeman Dyson in a private communication to Russell Johnston in the 1980s.) This means that hospitals, mining facilities, international trade, and travel could all be done in space with the help of these space elevators.

The efficiency of power transfer is a limiting issue. The most efficient power beaming in the present-day is a laser beaming system with photovoltaic panels on the climber optimized to the wavelength of the laser. With the best (and most expensive) current technology, between atmospheric losses, losses in generation of laser power, and losses in absorption on the panels, the efficiency is around 0.5%, the multiplier used above. And if climbers are to be disposable, the most expensive photovoltaic panels may not be an option.

Losses due to atmospheric spreading could be reduced by the use of adaptive optics, and losses due to absorption could be reduced by a properly chosen laser wavelength. But although laser and photovoltaic technologies have been rapidly advancing, it is unknown whether the losses can be reduced to an acceptable level. Barring significant development, costs will remain far higher than in the speculative optimal figures, and space elevator transports will be more expensive than current rocketry.

The cost of the power provided to the laser is also a limiting issue. While a land-based anchor point in most places can use power at the grid rate, this is not an option for a mobile oceangoing platform.

Up-only climber designs must replace each climber in its entirety or carry up enough fuel to get it out of orbit - a potentially costly venture.

When comparing the costs of the space elevator with conventional rockets it is important to take capital costs into account. Whereas the cost per kilogram to place 1kg in geostationary orbit using Ariane 5 is about $25,000 this does include much of the capital cost: The cost of fuel being but a tiny percentage of that, less than $30/kg. The energy cost of the space elevator is perhaps $350/kg, if a 0.5% transmission efficiency is taken into account. With the lowest estimate of capital cost of around $5bn for the simplest space elevator, the elevator requires a substantial payload to be transported before it would become cheaper than rockets. The next generation of Ariane rocket can lift twice the payload, requiring perhaps twice the fuel, but other costs are unlikely to double. It is speculated by some, possibly naively, that future technological and efficiency advances, coupled with a demand to shift into geostationary orbit the amount of material which would justify a space elevator, could reduce rocket costs substantially, making the task of justifying the elevator on cost grounds somewhat more onerous.

OK, what's wrong with that? Rei says the fuel cost is out but if so it is not out enough to ruin the argument. Paul Beardsell 22:42, 6 May 2004 (UTC)

Let's try something constructive: Here's a proposal. Lets try and agree on a general plan, then make the edits.

The problem with including specifics on economics beyond a baseline is that you have to pick a particular space elevator design plan. There are many out there, with varying levels of research behind them. If I had to pick, I would support the HighLift (Bradley Edwards) proposal, partly because it is one of the most thorough I've come across, and partly because I'm most familiar with it because I spent a while debating details on the message board for it (and, just so you know, I was one of the pessimists there). However, I would like other people's stances first as to what design plan to cover.

The 0.5% is just an approximate number, and Edwards thinks he can get notably higher (although I disagree on some specifics). We can get more exact numbers if you would like; again, however, it really varies depending on what specifics you use. With adaptive optics, there are really only three issues: absorption by the air (which varies based on the wavelength); efficiency of power to light conversion by the laser (unfortunately, different lasers have different wavelengths, so it is a balancing act with the above mentioned issue); and the efficiency of the solar panels (used to be pretty bad, but high-end panels are getting pretty good - however, with Edwards' proposed one-way climbers (which I disagree with for a variety of reasons, this being one), the best may not be affordable. The biggest loss is the energy conversion from wall to light power by the laser. Diode lasers are the only really efficient ones currently, but diode lasers have poor coherence. There's more work to be done if we want to improve the laser efficiency figure.

Whatever base stats are chosen, it needs to be explained that this is one possibility, and may be more or less efficient than other methods. ... you may want to look at how quickly launch costs have been advancing since the 50s - the old Titan series is actually more cost efficient than new series' like Ariane, and is close to the new Atlas series. This page has a nice graph made from Astronautix stats [5] which puts it into perspective.

So, trying to portray chemical rockets as having the potential to advance anywhere close to that of a space elevator seems kinda silly (you'll find most people at NASA will agree on this); however, I do agree that an example or two of the overall economics of the system (instead of just the baseline) would be a nice addition. Rei 23:14, 6 May 2004 (UTC)

OK, anything which isn't a whitewash of the costs is fine with me. The problem with the costs of space transport is that the costs are often at least partly hidden in defence budgets - the accounts are not transparent. Another problem (from an economics perspective) is that some people so much want to do the space exploration that the huge cost is played down by them. Similarly, the science/exploration/adventure/survival "right stuff" aspect almost makes cost a non-issue, from time to time. And, of course, the benefits of space travel, even if they are substantial, are often intangible and difficult to measure. However, there is an economics section in the article and that section must be seen to deal honestly with the costs.

I think my use of the term capital cost was unhelpful or it was misunderstood here. I do not know how transparent the Ariane accounting is, but the charge per kg lifted is $25,000. My estimate of the fuel cost per kilogram lifted, (for LH2+LO2, admittedly, and even if it was out by a factor of 10, which it wasn't) at $15 per lifted kg (doubled in my proposed edit of the economics section, above) certainly shows that Ariane customers are paying for a lot more than just fuel: They are paying extra presumably to contribute to or to cover the manufacturing cost of the essentially disposable rocket, staffing costs, the cost of preparing the launch, cost of maintaining the launch site etc. This $25,000/kg figure rocket figure is used in the first paragraph of the economics section in comparison to the $1.74/kg figure for the idealised electricity usage of the elevator. As I have tiresomely demonstrated, this is a misleading comparison. There is the cost of building the elevator which is not factored into the 1.74 figure whereas the cost of the rocket is factored into the $25,000 figure. Essentially the issue is one of marginal cost vs total cost. For the rocket it is the same total cost per kg, more or less, no matter how much we lift. For the elevator we need to lift a lot before the total costs fall below the rocket. Why this obvious point is resisted I do not know. The economics section, as it stands, reeks of bias.

Before a reply, if any, is crafted, please take a second to read what I have written. Responses have put words in my mouth. Please note that yet again I have not mentioned the word "shuttle".

Paul Beardsell 11:45, 7 May 2004 (UTC)

( Beardsell correctly calculates the density of LH2, someone claims his LH2 calculations are "way off", Beardsell gets upset. I think I would too. Focus on getting the correct numbers in the article, people. I don't care who was "right" and who was "wrong". -- DavidCary 17:23, 11 May 2004 (UTC) )

We need to discuss both a reusable space launch mechanism (like the shuttle) and a disposable one (like most versions of the Ariane series). Also, note that you are being unfair by comparing a rocket which cannot compare a human payload to a space launch system like a space elevator which *can*. Additionally, you are comparing a system with no reentry capability (without an additional module that you're not factoring in) to one that has reentry capability like a space elevator. That would be like me comparing Project HARP to the Space Shuttle (yeah, you could launch people, but they'd be liquified on arrival). This is consequently an unfair comparison, and I would like you to acknowledge that. Furthermore, you're comparing costs to LEO; a space elevator can go to GEO and even directly fling craft as far as Saturn. I will discuss both systems below anyway, and only cover the far lower LEO costs. But, again, I want you to acknowledge that you're making an unfair comparison.

You have this upside down. I am not the one who is comparing rocket costs to elevator costs. It's right there in the article NOW. I did not introduce the comparison. Someone else did. And you reinforce it with your placing of your 1.74 figure in the same sentence as the 25,000 figure. Both expressed in US$ per lifted kg. It is not my comparison. I would be happy to remove the comparison but happier to compare them more fairly. And it is an unfair comparison for the reasons I give AND for the reasons you give. I AM NOT MAKING THE COMPARISON. The comparison is made already. UNFAIRLY.

As I demonstrated with the shuttle, the turnaround cost per launch of the shuttle of inspections, refuelling, replacement parts, etc *ALONE* costs the 10,000$/lb. *AND*, as I demonstrated (which you keep ignoring), given the 100-flight expected lifetime of the shuttle, the manufacturing cost per kilogram is almost nothing..

I never mentioned the shuttle.

If instead of making components of the Ariane 5 reusable (as ESA is trying to do), your goal is mass production to try and lower costs - GOOD LUCK. This is a 278 metric ton craft. You will NEVER get a 278 metric ton high-tech spacecraft for cheap, *regardless* of "mass manufacturing"; furthermore, much of the craft *already is mass manufactured*, from the fuel to the casing to most of the electronic components. I don't know why this is a difficult concept for you. Rockets have not been getting measurably cheaper, and there is no sign that they are going to by any significant amount, no matter what we do. Also, I'm wondering why you keep focusing on the Ariane; the Ariane program, by many standards, has been one failure after another. If I were to send a payload up on an Ariane, I'd want to have a pretty darn good insurance policy ;)

Once again, you put words in my mouth: I cited one paper which suggests cost savings in rocketry are possible. I said it was "speculative" and "possibly naive". Your attack on the study some time back may or may not have had substance but it was masked by the vitriol. As to the Ariane: The issue isn't the Ariane specifically. By contrast, I am not an Ariane-bigot. And if any one rocket fails the consequence is? Insurance for the elevator? Before you reply remember I did not raise the issue of insurance - you did. Paul Beardsell 18:03, 7 May 2004 (UTC)

In short, the cost of a disposable rocket MUST be factored into its launch cost, while the cost of building a reusable rocket becomes relatively insignificant to the turnaround costs.

... Fine. Let's factor it in. Paul Beardsell 18:03, 7 May 2004 (UTC)

(...discussion about incompetence and insanity snipped...)

... Here is Edwards' report ... [6]. He's not the most optimistic, nor the least optimistic, of analysts out there, so it would only be proper to mention that other proposals have higher and lower costs for construction; also, it would be proper to mention that this is the cost for an elevator on Earth; elevators elsewhere (such as Mars, and especially on smaller bodies) are far cheaper. As you'll notice referenced near the end, once you get a single space elevator up, the cost of all future space elevator construction drasticly drops, and continues to drop. So, while your first elevator will be the most expensive to repay capital costs (but still far, far ahead of anything chemical rockets could conceivably achieve), future elevators' capital costs drop drastically. In fact, one of Edwards' suggestions is to use the elevator to build other elevators and sell them to industry, paying off the initial investment in short order. And, furthermore, one must not forget that this doesn't just bring payloads to LEO, it brings them to GEO and [does all kinds of other cool and wonderful things]. It is completely unfair to compare to a single stage, no-reentry, human-incapable disposable LEO rocket, and I'm sure you know that. Rei 16:48, 7 May 2004 (UTC)

The hidden issue is this: What is the project? For you, it seems, the project is the elevator! NO! The elevator is not pretty enough to be justifiable on its own. What is the project that requires us to lift (and return?) many millions of tons to GTO? Because when we know the tonnage, whether passengers will be making frequent trips, when we know how much material must be returned, etc etc, then the rocket vs elevator comparison can be more fairly made. In the interim THERE IS NOW AN UNFAIR COMPARISON IN THE ECONOMICS SECTION. I will have yet another attempt to make this better. Not perfect (because you are the prickly judge) but better. And I ask you to leave the better version in place. Paul Beardsell 18:03, 7 May 2004 (UTC)

Rei: Additionally, you must think that groups like NASA and the ESA are incompetent. They've spent phenominal quantities of money on rocket systems, and they haven't gotten anywhere remotely close to what you think rockets should cost, so clearly they're incompetent, right?

I wouldn't lean too hard on this point. There's ample reason to believe the cost of getting to LEO via rockets could be cut by ~an order of magnitude. --wwoods 18:14, 7 May 2004 (UTC)

Could you document this, please? From someone who actually has any sort of authority in the field? They haven't been really cut for 50 years - what's your evidence? Psb has an article by someone who has no apparent experience in rockets (the founder of Autodesk, Inc and co-author of AutoCad - a programmer. At least his programming had *something* to do with design). On the other hand, lets see what NASA has to say. "Current systems have essentially pushed chemical rockets to their performance limits." [7]. I mean, there are improvements in the works: better materials tech to enable reuse without so much maintinance; aerospike engines for more efficiency at different altitudes in the atmosphere, reducing the need for more stages; more compact propellants (such as solid hydrogen, or forms of benzene instead of kerosine) to reduce the needed size of propellant tanks, reducing mass and air resistance; etc. But these things can only go so far.

Your quote says "performance" not "cost". You continue to resort to ad hominem attacks. You should play the ball, not the person. What is wrong with the paper? Paul Beardsell 19:55, 7 May 2004 (UTC)

I found this but would be interested to see any other reference. Paul Beardsell 18:25, 7 May 2004 (UTC)

meta wikipedia: intersperse vs. quote

Ok, again, I'll ask you not to intersperse comments. It makes it hard to follow.

I would rather intersperse my comments. I find it easier to follow. And it avoids the illusion you create of answering my points by quoting selectively from my post. Which needlessly increases the length of the post and makes it hard to follow.

I would rather intersperse my comments. Well, it's your choice if you want to be a pain to the person you're debating with.

This is something that applies to every talk page, not just the space elevator talk page. Could we take this to

? -- DavidCary 17:23, 11 May 2004 (UTC)