h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: The Space Elevator - A805466
Author: Reciprocal Episkypos Connerie II - U200599

A brief description of the concept and possibilities of a space elevator

nice article, but it has some inaccuracies in it.

for a start, most of the technology of how to build it is explained quite clearly in arthur c clarke's book (I think it is the fountains of paradise, but I will have to check).

some of the problems in the article stem from quite basic misunderstandings of the technology which have knock on effects.

for a start, the cable has to be manufactured in geostationary orbit, and then fed out from that facility in both directions (out, and down).

this minimises the number of shuttle launches needed to being just enough to manufacture the space to earth tethers.

when you get onto the actual lifts, all of the main problems have been solved by the japanese when they managed to produce a practicle example of a start trek style turbolift based around mag-lev technology.

you also underestimate the economic arguament. for a start, your costing for sending things up and down are about twice what they should be, due to a misunderstanding of the technology. the downward part of the journey would be powered using the techniques of regenerative braking making the down traveling car act as a generator. most of this energy would be reused to push the car back up, so you would only need to produce enough power to overcome the inefficientcy in the system (plus a little bit).

once you have an elevator, you imediately have a captive market with the satellite industry. launching something into space using rockets is very inneficient, and thus very expensive. also sending something up into orbit using a freight elevator imediately saves them a lot of money because of the cheapness of the insurance. (rockets tend to blow up, and are thus expensive to insure).

as soon as you have a practical space elevator, you immediately reduce the cost of mars missions a lot. this makes a mars colony much more economical, which in turn makes asteroid mining much more economical.

as you have probably guessed by now, I do know a little bit about this subject.

keep up the good work though, as a lot of the article is very good.

Thanks for the comments; just a few issues I'd like to address:

1) Why do you claim that the tether has to constructed in geostat orbit? Yes, it has to be fed out from there, but not manufactured. Given the cost of setting up a manufacturing facility for carbon nanotube in outer space, and also given that the material would have to be shipped up there for the construction (unless we moved some other asteroid into place for resources, again a large undertaking), it would be cheaper to manufacture the cable on earth and then ship it up to the geostat satellite. Also, it was my impression (and please correct me on this if I'm wrong) that the cable had to be fed out from both sides at the same time (otherwise, you start changing the centre of mass), and, as such, you would have to ship enough cable for both the asteroid and earth tethers.

2) I was unaware that the Japanese had created such a device... I will research it and update the article accordingly

3) I didn't calculate the energy costs personally; they were found, I believe, on the NASA site, so if you think they are twice as high as they should be...

4) Regarding economics, yes, it would revolutionise the satellite industry, but there is only so much to be gained from throwing satellites up into the sky, and at the cost levels provided by an elevator, the source of people wanting to send up satellites would drop rapidly, because they'd all have sent them up. To justify the costs of building an elevator, it would need to open up entire new markets. The mars colony and asteroid mining are two good examples, yes, but at the moment I don't think the human race is in a social or economic position to attempt such long term ventures. Maybe you disagree with this point.

Anyway, as I say, thankyou for the comments- I'd be interested to see your take on some of the points I've raised here

there are a lot of economic arguament in favour of this technology. nasa's own site gives a cost of $222 for a person with 150kg of luggage to orbit, compared with the current cost of $10,000 per kg.

considering there are already people paying $15,000,000 for a trip into space, I think a tourist industry would be an almost imediate consequence, especially as people will currently pay those sort of figures for a night in a good hotel in london.

asnwring your other points, you are talking about a 21,000 mile (35,000 km) long cable from sea level to geosynchronous orbit, and another one going further out to act as a counter balance.

a drum with 35,000 km of cable on it would be just a little large, and at least as difficult to work with as the manufacturing plant.

The cable needs to be one continuous cable with no joins (a lot of people get things wrong on joins) and a drum this size would be massive. to lift this into space, you would need a massive lifting body, orders of magnitude bigger than anything I have heard anyone contemplating. to give you a clue as to the difficulties, mars direct needs a lifting body capable of moving 125 tons into space in one go (which can be built with existing technology). the thing you are suggesting to lift such a drum would be much harder to build.

nasa do do a good job with the calculations, but everything they calculate is massively overpriced. they routinely overestimate manpower requirements, which has a knock on effect for all the other technology required. using mars direct as an example, their estimate using their assumptions was 7 times as expensive as the scheme the original authors of the plan came up with while at the same time being only a "plant the flag" mission.

as to satelites, how would you like broad band settelite access to the internet for a couple of pounds per month? the current cost of satelite services are arbitrarily inflated due to the unrealistic cost of launching them.

another consequence of building an elevator to space is the simplicity of building another few. you could then easily connect them together and have travel to any time zone in the world for a few hundred pounds.

you question the economic and social condition of the planet as a questionable point in the construction, but the returns would be massive, just like with the moon program, but it wouldn't take as long.

imagine america deciding to set up such a thing from their continent, with the massive increase in communications satelites that they would get as a result (not to mention all the ancilliory industries needed to build the elevator). america spent around 10 years going to the moon, and reaped the rewards for about 20 years.

long term research of this type always pays off. the moon shots returned (directly) about $7 for every $1 that was spent on it. the channel tunnel has similar return rates, so has the swiss tunnels through the alps.

The figures you quote are the ones I used in my report. I accept your claim that nasa's costings are over-priced, but as I'm sure you'll appreciate, I'm not going to try and calculate my own figures for the cost of building and using an elevator. The difference between $1.50 and $0.75 in any case is negligible when compared with the cost of sending somebody up in a shuttle, and this is the point I was trying to illustrate.

Yes, I appreciate the economic potential of an elevator; I hoped I had made this clear in the article, but I think you are confusing economic potential with short term return. The virtue of simply having a space elevator will not immediately open up a space tourist industry; the infrastructure simply does not exist. For one thing, the man who went up into space had to undergo rigorous training to ensure he could cope with both acceleration (less of a problem with the accelerator) and zero G (still a problem). The training itself probably cost him many thousands, limiting the numbers of people immediately. However, this is less of a concern; there are still many people who would be willing to pay thousands for a trip into space. The problem is that the facilities do not exist on earth to train any large number of people for space flight. Even if it did, the training took many months- how many people would have both the luxury of being able to devote large amounts of their time to training, or the willpower to do so?

These concerns can be overcome, for example through the building of a rotating space station, able to generate an artificial gravity field, but such a station would be almost as large an undertaking as the elevator itself- not only in terms of construction, but in certification, safety checks, and, paramount to the 'average person', insurance checks. Sure, you may be able to go up to space for only $300, but if the insurance to do so costs thousands, you're greatly limiting the scope. It's unfortunately not as simple as saying, 'oh, we have a space elevator, bow we can send lots of people into space'. Yes, a space elevator would have incredible potential for return in the long run, but in the short run it would be phenomenally expensive, on scales much larger than the channel tunnel and the moon project. You mention America, perhaps the singular least forward looking country in the world. They won't impose tighter emissions controls at the moment, despite the clear benefit to them not only in a cleaner environment, but in having less dependence on oil- switching to alternative fuels would have almost a knock on effect of making any country the world's foremost superpower when the oil begins to run out, but has any country seriously put any effort into it? No- because in the short run, it would be horrendously expensive. Can you serioulsy expect any country to begin perhaps the most expensive project undertaken by man, in expectation of a large return in, what, 100 years time? If you can, you are a much greater optimist than I...

Regarding the necessity of taking all the cable up at once; yes, this was something I completely overlooked, and as such I see what you mean about it, and will update the article accordingly. However, I still envision the problem of having to ship up the manufacturing equipment and the material to construct the tether (or manouvering an asteroid into place)... either of these things would have expenditures ranging into hundreds of millions...

I also disagree with the point you make about America building an elevator- while they could do it from their continent, they could not do it from their country, and as such a lot of the jobs involved in the construction, the relatively unskilled labour, would come from the host country. I can't imagine this being politically acceptable in America, especially when the project would be costing billions of dollars. While a lot of high tech industries would benefit greatly, as you say, from an increase in business, the unskilled labour force, a high pressure group, would not. Also remember that this project would be coming out of government funds- costing the taxpayer.

Sorry, but where did you get the figures for return on the moon flights? Unless I'm missing something obvious out, I can think of very little direct return from the moon project? Yes, the technology enabled America to launch satellites, but that is indirect revenue- where is this supposed 7:1 ratio you give coming from? The moon project brought little back in terms of material, didn't provide any goods, or even much saleable information. The channel tunnel and through the alps, yes, but both these projects have supporting infrastructure at either ends. How successful would the channel tunnel have been if we also had to build France at the other end?

As I say, thanks for the corrections on the technology, but I do think you're drastically oversimplifying the economics issues.

Just to say, I've updated the entry to cover what you mention about the construction of the tether in space, and the latest developments in maglev vehicles

once it is built, I expect it to pay for itself within a generation.

how do I work this out, well, I start off by pricing satellite launches just a little less than they are now. this brings in a good return, and also reduces the insurance for satellite launches.

as the amount left to recover goes down, so can the price of lifting stuff to orbit.

obvious things to be launced are a massive increase in space probes and new technology testers which are currently limited by launch cost.

another obvious use would be for mars direct. once you had mars direct up and running, it would pay them to build it themselves, thus simplifying the whole process of setting up a permenently manned base on mars.

relatively unskilled labour is a red herring. nothing on this project could be done with people just plucked out of the fields, but you might be able to do it with people just plucked out of the universities.

as to what the return was from going to the moon, you have the reduction in size of computer equipment, so that a 4 function pocket calculator is no longer the size of a fridge, kicking out at least as much heat as an electric fire.

you have the improvement in aviation construction techniques, so that you can actually build jet airliners.

you have a hole host of new materials that are used all over the place.

you have the development of techniques to manage previously unmanagable projects, without which we wouldn't be able to build the 747 let alone the much more complex 777.

there are a whole host of radio based technologies which are essential to the satellite industry.

how about the improved understanding of this planet we got from comparing it in detail with samples from the moon.

and of course the trickle down of money from spending such a large amount doing the job. all those people working on it got paid, and were then available for other jobs which would have been imposible prior to the moon program. everyone getting paid also paid taxes, which went back into the goverment.

and most important of all, the incredible optimism, that "we can do anything" because they just had done.

I'm sorry, but I think a generation is highly optimistic for a project that would cost as much as a space elevator. Yes, I concur with your rationale over launching satellites, but, as I mentionned earlier, simply sending more birds up won't help. Once you have however many of the things up there, you simply lose the benefit of having any more... yes, the increase in communications bandwidth would be exponential, but once every household has cheap broadband access via satellite, what then? Also, do you honestly think that the USA (being the only country with enough resources to feasibly attempt such a project) would allow countries such as China to use their space elevator to launch spy satellites; what would be another large market? There's a great deal of politics involved in such an issue also.

You mention space probes and new tech tests- most of these (especially the former) are funded by acedemic institutions, which are funded by the government. They haven't got half the funds available to recoup the cost of a space elevator project, certainly not when considering that the government would just have spent a great deal of it's scientific funds on the elevator itself... As I previosly mentionned, the elevator has to open up new markets, rather than just reducing the cost of existing ones. Mars direct is a good example, but even the cost of making the probes/generators is going to be high enough to mean mars direct is still trying to recoup its costs a few years later. Only when raw material can start being brought back from mars will the profit begin to take effect, and, though you evidently know more about the mars direct project than I, I'm fairly sure a mining operation is not yet part of the plan. Likewise for asteroid capture missions; simply the planning and construction of suitable equipment would put them in debt before they even got near an asteroid... it would be years before they could start recouping the costs of an elevator.

Even if, as you claim, the costs could be recouped within a generation after construction, the construction itself would be on the scale of a half century project. Simply putting the infrastructure in place to even contemplate building a 50km tower at equatorial latitudes would take the best part of a decade, as would preparing an asteroid capture mission (or two). Carrying out the capture mission would take another decade, or longer, and the construction of the tower would take at least 20 years (the channel tunnel took 6 years), and then after that you have to launch the geostat station and construct 70km of cable. Then, the whole thing has to be checked, trains have to be loaded and tested... worst case scenarios explored. In all this time, the elevator would return no direct revenue, and all this time it would be chewing up funds left right and center. Again, do you really think such a thing would be even contemplated in today's economic conditions?

The large proportion of the project would be done with relatively unskilled labor... even considering the anchor tower (likely to be the largest construction part of the project), can you see university graduates driving the cranes, can you see them mining the resources to build the thing, or laying the railways that will be needet to bring the resources in? Will it be graduates fitting the windows in the tower, decorating it, installing the miles of electric cabling, the plumbing, the internal transport? Yes, the people designing the elevator, the people supervising it, those organising it will be highly skilled graduates, but the majority of the workforce? They will be composed of people with very few qualifications, skills, and the like, especially given that most equatorial countries are undeveloped, poor, and uneducated.

Your claimed returns on the moon project are anything but direct return. They are, at best, technologies that were developed for the moon project that also had other uses. The majority of them would have developed without the moon mission, and none of them, except the last, would have been hindered in the slightest if Apollo had just sat on the launch pad for the next 30 years. Computers were getting smaller and smaller anyway, the development of the transistor saw to that, and while this may have been sped up by the moon project, it most certainly wasn't a direct result of it.

satellites are reletively cheap to build (as evidenced by the fact that there are some amateur radio satellites already up there. it is the launch cost which is the expensive bit.

what on earth makes you think that people will accept an arbitrary limit on the speed of their datastream? when I started using computers, 1200/75 viewdata services were fast. since then you have got an entire new internet radio industry (of low transmission quality) which would get an imediate boost from having 1gb/second transmit rates. so would the (currently embryonic) video on demand industry (imagine napster for movies), and this is just a few of the extra things you can do with more bandwidth.

space probes and technology testers are again limited by the launch cost, not the construction cost.

there are many ways to get extra income out of a space elevator, without needing a massive office complex or hotel. the anchor could be massively smaller simply by modifying the construction method a little.

There is also a faulty assumption in your construction plan. while having a 50km high hotel type building would be nice, it is by no means essential for the construction of such an elevator. this is another example of the nasa over specification problem with knock on effects.

when you remove this massive office block (which you would have difficulty building with existing or near forseeable technology), you remove most of the requirement for unskilled labour.

you also remove the need for massive infrastructure to build it, as well as the infrastructure to maintain this towering folly. admittedly you would need some infrastructure for freight, but not much more than a container port complex and a long road.

capturing 1 asteroid to act as a counterbalance is currently possible using the technology from the deep space one probe (ion engines).

I also think that you are underestimating the payback from tourism people already pay thousands to pop over to australia and be able to say "I saw airs rock". I see no reason why people would not pay to go up to the transfer lounge and look down on the atmosphere, or up into space.

if you then add the orbital construction industry which would naturaly be based from there (ie a star trek space dock) and a lot of people would quite happily go and watch the latest mars colonisation ship being built and launched (they already pay a lot to go watch shuttle launches).

if you add resteraunts at waystations part way up (which would not be that hard to do) then you have an entire new industry, high altitude dining (people will already pay thousands to have a daytrip to new york).

I'm beginning to develop the impression that this argument is going nowhere... still...

satellites may be cheap to build, but probes and the like certainly aren't. Even ignoring the launch cost, these things often cost in the terms of tens of millions... even a cruise missile is over a million usd a piece. Couple this with the fact that the government's science grants would be going down, and you're not exactly looking at the science community being able to repay the cost of an elevator.

I didn't say anything about an arbitrary limit... I simply said that there was a point at which providing extra bandwidth would be pointless, because we wouldn't have anything to take advantage of it. OK, so TV on Demand and streaming video could use higher bandwidths, but they would also require a mass upheaval of existing practice on earth, especially on the legal front. Also, simply putting more sats up there isn't going to magically increase the speed of transmission for a number of reasons. Firstly, any competing broadband service is going have to provide a good upload speed as well as download- this means vastly increasing the power of groundstation transmitters on people's houses, as well as providing tranceiver dishes, which do not come cheap. Secondly, the massive increase in traffic is going to need vastly more complicated switching systems, not only between frequencies but between satellites. To provide a 1gb/s rate, we're talking about a massive increase in bandwidth, meaning we can't just go frequency hopping... we have to go satellite hopping, or else you get nothing due to interference. This, in turn, means trackable satellite dishes, remotely controlled by a central system. All in all, an immensely complex and expensive proposition. Trackable dishes cost thousands of pounds already...tranceivers even more.

While I agree that there is no theoretical reason why the anchor cannot be a lot smaller, but I have as yet seen no design that has not included a large tower. If you know of one, please give me the url and I will consider revising my article. However, while your criticism of nasa is no doubt mainly accurate, you forget that if a tower was to be built, they are the ones most likely to be coming up with the final plans for it. As such, I stick by my reasoning that the tower would be a major part of the elevator, along with all the necessary infrastructure to support it.

I never said capturing an asteroid was not possible, just that it would take a long while just to plan the mission, build the equipment, and carry it out. Just having the technology doesn't make the project instantly viable- most space missions are launched at least 3 years after initially being proposed, usually more.

I'm not underestimating what people will pay for- I'm sure people would pay simply for the ride up and down again, but I think you are overestimating the elevator's initial ability, both legal and technological, to cope with them. Even for simply an up/down trip, insurance would demand that there are facilities capable of coping with, say, an unability to take the passengers back down again. This would have to include toilets, which means rotating sections, as well as food, water, emergency fuel... probably even some kind of life raft, before you could even think of sending untrained people into space. There's also the acceleration on the way up and down, which, while lower than in a shuttle, would still be very high for somebody not used to it; this would require basic medical facilities
and personell able to use them. Also, the simple problem of air recycling would put strict limits on the number of people that could be in the station at any time. Once again, it is not simply a case of letting them pay to take a journey up... space is not australia.

I disagree with you about waystations- I think they would be very difficult to construct. They can't dangle on the cable... you yourself mention the problem of joins, and neither could they feasibly cling on. They would both get in the way of the elevators and cause undue wear on the cable. They would either have to be suspended independently, or held up by some permanent magnetic fiedl, something very hard to implement.

This may be of interest: a bbc web article on a story I read elsewhere (in the Newcastle Metro newspaper if you must know).
Basically, NASA have thrown USD$565000 at a project designed by High Lift Systems of Seattle.

http://news.bbc.co.uk/2/hi/technology/2188107.stm

Yes, the cost would be great, but it pales in comparison to the cost of constructing an Iron Dust Black Hole 1 light year from Earth, as Discussed in the book "The Iron Sun". There are several parallels however; the project should be a world venture, as discussed in the aforementioned book. A country can only afford so many Boeing 747's, even less 777's. This number grows smaller for aircraft carriers, then space shuttles, and finally in today’s economy, there is financial room for only one beanstalk per planet. It should be either a multinational or a multi-corporate project, rather than the domain of a single entity. Just as the Cassini project was badmouthed (even by respected physicists!) so will be any beanstalk construction that involves orbiting a nickel-iron asteroid anywhere near earth. Imagine Green Peace's response.

As an aside, if the nano-forge become reality, all of your costs go out the window anyway.

the bandwidth payoff on satellites would be in terms of web cache and proxying.

because generally most stuff on the net is designed to be done as on demand broadcast, there is nothing stopping the adoption of this technology in various local regions, which would also include on satellites.

upload can still be done to webservers and the like in the standard way.

you mention the need for massive change in the legal system, but as even microsoft are prepared to state that peer to peer is here to stay, that change is going to have to happen anyway.

the legal cahnges are part of the ongoing intellectual property wars which will drag on for years, with the loss of big names on all sides of the arguament.

true, probes cost a lot, but a lot of that is due to their upfront development cost. if you can know from day one that the launch cost is going to be massively less, and can therefore share the development cost over more probes, the costs come down a lot.

if you think I am talking out of my hat on that one, look at the mars mapping missions from the early 90's onwards. they managed to use the same probes to map the moon, the earth (secretly as spy satellites) and multiple probes to mars, for less than the price of one ordinary mars probe.

I don't think the air recycling problem is so difficult either, as it is basically a variant on existing long haul flight and space station technology

the air problem does however mean that the more people you intend to take up, the more "free space" you end up with. this is why the cabins on the enterprise D in start trek are much bigger than the ones in the original series.

once you get a proper space industry with regular launches (which would not require that much of an increase in traffic) you have a self funding industry.

still, on the whole I like the article.

keep up the good work.