I know this has been discussed before, but it is appearing the whole space elevator idea is looking rapidly more feasible.
A company called HighLift Systems intendes to test prototype technologies for the space elevator in the next few years (http://space.com/businesstechnology/technology/space_elevator_021120.html)
So, what do you think? Is the elevator, feasible, or is it just a pipedream? And would it really be as advantagous as is often claimed?
-Oli
And here
I still think it’s an interesting idea. Might be real soon! Might never happen. Oh well…
I don’t think it will happen real soon… but it would not surprise me if it happens in my lifetime. (I am 33)
Cheap, economical access to space? There’s plenty of money to be made with anyone who comes up with that. Hilton has pledged that the moment someone comes up with affordable space travel, they’ll put a hotel in orbit. Considering that many of the folks involved with this have oodles of brainpower at their command, I’d say that they’ll be able to pull it if off. If they can’t, then you might as well start writing humanity’s obituary now.
Beware: Here there be offensive song lyrics.
[spoiler]
Oh, give me a locus where the gravitons focus
Where the three-body problem is solved,
Where the microwaves play down at three degrees K,
And the cold virus never evolved. (chorus)
We eat algea pie, our vacuum is high,
Our ball bearings are perfectly round.
Our horizon is curved, our warheads are MIRVed,
And a kilogram weighs half a pound. (chorus)
If we run out of space for our burgeoning race
No more Lebensraum left for the Mensch
When we're ready to start, we can take Mars apart,
If we just find a big enough wrench. (chorus)
I'm sick of this place, it's just McDonald's in space,
And living up here is a bore.
Tell the shiggies, "Don't cry," they can kiss me goodbye
'Cause I'm moving next week to L4! (chorus)
CHORUS: Home, home on LaGrange,
Where the space debris always collects,
We possess, so it seems, two of Man's greatest dreams:
Solar power and zero-gee sex.
-- to Home on the Range
[/spoiler]From the UNIX fortune file. 
I looked at your link, starman, but there’s nothing to it.
All we need to do is to get nanotubes from microscopic to tens of thousands of miles! No problem! Would next Thursday do?
There are already lots of places in the world that are doing research into growing nanotubes. Another effort won’t add anything much. A mere $13 million in research funding is a drop in the bucket.
Hundreds of these little companies form every year. They burn through their money, show no results, and are turned down by the venture capitalists when they go begging the second time.
I love the idea of a space elevator, but I guarantee that these folks will have nothing to do with it.
Wake me up when a nanotube of a mile is made. Then I might start believing in miracles.
P.S. Derleth: I must just be jaded, but I looked hard for offensive lyrics and didn’t find any. Are you leaving off a verse?
Exapno Mapcase, the only real point of contention I have with your post is this:
Nanotubes of just feet or even inches in length would probably be enough of an enabling technology.
The key to multistrand “rope” strength is the strength of the individual fibers compared to its cross-section, and their length to thickness ratio.
I think the strength of each nanatube compared to its cross-section is well enough established so that I don’t need to address it here.
Typical nanotube diameters are about 1 nm. A 10cm tube would already have a length to thickness ratio of 100 million to 1. Making nanotubes of even greater length would have a real, but fairly small effect on the strength of a macro scale cable made from them.
Well, yes and no. A 10cm tube would prove that the current concerns that long nanotube chains are impossible are wrong.
But 10cm is still a laboratory curiosity. Go up to 1 km and then you’re doing it commercially. You have to have an active industry going before you can think about the 100,000 km mentioned in the article.
We’ll find plenty of uses for long nanotubes on earth well before a space elevator is ever erected. As I said, wake me then and we’ll talk.
The point was that 10cm long tubes (if makable, and in significant quantity) would be all that is needed to make the cables of any length desired.
They don’t need to be able to make single tubes longer than a couple of inches to make it viable for any of these projects.
What are you doing to splice together the 10cm tubes? Can you splice nanotube directly to nanotube? (And if so, can’t you make longer tubes in the first place?) And if you can’t, then how can your splices be as strong as the tubes?
I’m really asking here, because I don’t know the answers and I don’t remember reading anything about splicing tubes together, only about growing them.
Not at all… you don’t splice fibers together end to end to make a rope either.
The point I was trying to make is that you don’t have to have fibers any longer that a few inches to make a good composite cable (rope).
If you made a cable out of 10cm nanotubes that was 1cm in diameter, it would be composed of roughly 30 - 35 million individual fibers in parallel. These would be bonded together somehow. As long as you didn’t conspire to get all the fibers to end and start in the same point of the cable, you would expect the cable to have at least 95% of the strength of the same size cable made of continuous fibers for its whole length. Current measurements put the tensile strength for single walled nanotubes around 200 gPa.
That would translate to a cable that could carry 20 million pounds for each square inch of cross section.
A 1cm cable would have a cross section of 3.14 cm^2 or about about a half a square inch. That would translate to about 10 million pounds for the 1 cm diameter cable.
I was using splicing generically. Say bonding then.
To get to 100,000 km you would need 1 billion 10 cm tubes. At 30 million individual fibers per cross section, that’s 30 quadrillion tubes. (And almost 30 quadrillion bonds.)
That’s what I call industrial production. (And quality assurance.)
Let’s see. A thousand factories producing one 10 cm nanotube per second would require – ~1 million years.
Then you’d have to put them together.
Nope. 10 cm is a laboratory curiosity.
I want to make this work, I just can’t.
(It’s late - please don’t jump all over me if the math isn’t right. It should be reasonably close. Correct where necessary.)
I think where you are missing it, is that they are not joined end to end. The bonding would be side by side.
I would also guess there are a billion glass fibers in a single Corvette. Look at how many Vettes, boats, and other fiberglass products are made per day. Trillions of glass fibers are manufactured per day, many trillions probably.
In yarn or natural fiber rope, the individual strands are not that long. And they are not even bonded together… They are simply woven/twisted together. Friction is what holds it all together, and still they are tremendously strong.
Also, I would imagine that a if they get a good manufacturing technique down, a single machine would produce trillions of fibers per day. Even in the lab, they don’t “put” them together… they are grown, more accurately, they set up the conditions so that they self assemble.
The trick is to get a set of conditions where reasonably long tubes self assemble with a relatively small proprotion of that are garbage. It will probably be much harder to sort the good ones from the bad than actually make them. If you set up a chamber were one will grow, countless others will do the same right beside it.
Putting them together should be something along the lines of feeding them into a big hopper and working them though some type of eyelet that squeezes them together and applies some type of adhesive to them so they stick together.
Just like any other composite, you don’t have to worry about the exact placement of any single fiber, it just has to average out well.
I make ropes as a hobby activity, so a few comments that may be relevant…
The glass fibers in, say, the hull of a boat, do not provide all the strength. AFAIK the fibres spread the load and arrest cracks, but the characteristics of the resin will still place an upper limit on the strength.
Synthetic ropes are strong and are made from fibres that are effectively infinitly long. bonding is not an issue.
Natural fibre rope are usually made from natuarally long fibres. Hemp and flax fibres must be getting on for a metre long. It is possible to make a yarn from shorter fibres such as wool, but this is not as strong. Twist in the yarn holds the fibres together by friction - untwist the yarn and is falls apart. Natural fibres have a high mutual friction. Natural fibres have natural twist and they are combined into yarns using twist in the opposite direction, this seems to be an important feature of well made yarn.
The twist in the yarn holds the fibres together and the friction between the fibres distributes the load evenly. The twist also makes the yarn flexible because when the yarn is, say, wrapped around a curve, each fibre can remain the same length - part of the fibre is on the inside of the curve and part on the outside.
A nanotube rope will need fibres that have a high friction when they are placed together - it will help if they have a high natural friction and if they are long.
Can nanotubes be made with a twist?
Yarns can be twisted together to make ropes and ropes can be twisted together to make bigger ropes and so on. Generally, the more layers there are in the heirachy, the more flexible and elastic the rope becomes.
scotth: In serious modern ropes, they yarns are very carefully placed so that they maintain a constant position in the rope. Doing so can at least double the strength of a rope. I guess that if the technology was available, it would be worth making sure these went in just the right place too.
G. Cornelius - I suspect the actual contruction of nanotube cable will be completely linear. It will probably not look twisted, etc.
I would say it will probably look alot like a graphite golf club shaft or fishing pole.
I think I overused the rope analogy.
Anyway, the big things, natural rope does not require continue fibers to be strong. It remains strong because the fibers begin and end at random in the rope, cable, or composite shaft. That is the key statement.
That is a ridiculously low number. It is likely that nanotubes in the future would probably be “cultured” rather than extruded or whatever. You get a big vat with the right combination of chemicals and you do something magical and, voila, 24hrs later, you have 5 tons of 10cm long nanotube.
OK, you all are slowly overcoming my pessimism, although I tend to freeze up as phrases like “do something magical.” I’m also still somewhat confused by synthetic ropes having fibers effectively infinitely long and translating that to 10cm fibers.
OTOH, there is always the little issue that nanotube fibers literally don’t exist today. They aren’t even 10cm. They aren’t bundled. There is no factory growing them.
The question is: are we where we were when the transistor was invented in 1948? Or when the integrated circuit was developed? Or the Josephson junction? Oops. That last one never did work, did it? I don’t think anybody knows the answer to this question.
Which, to get back to the OP, is why this space elevator company is about as feasible as that company that plans to put a million tourists a year on a space station. Do something magical, indeed.
Well, nanotubes are already made in enough bulk to be used commerically. They are already being used in flat panel TV’s and mixed with plastic to make it conductive for a number of electronics and automotive uses.
The something magic happens, simply means that Shalmanese doesn’t know the technical details of how they do it.
What we can’t do today is make long nanotubes in bulk.
10cm certainly, and .5cm probably would be long enough to make all these wonderful new structures.
I can’t predict if they will get it figured out how to do it or not, but alot of progress has been made already. These things were first discovered in '82. Industry has only really been playing with them a short time.
Interest is so high because we can see obvious uses for them, if cheap bulk production of long tubes is realized. Industry has a HUGE carrot to get the problems resolve. Whoever succeeds first is gonna be wealthy on a grand scale.
The Josephson junction certainly works. I think it was the supercooling that made it unfeasible.
I suspect that the carbons in the nanotubes are so tightly bonded to each other (that’s why the tubes are so strong, after all) that there will be little friction between tubes. So the resin or whatever holding them together will have to be equally strong. Come to think of it, what is going to make the resin stick to them?
And what is this business model? If the cost is several hundred dollars a pound, then a week at the Geosynchronous Hilton will not cost less than a couple hundred thou, which puts it somewhat out of the range of the upper middle class. Asteroid mining? Maybe, but I don’t think you are going to find a gold asteroid and if you did it would just kill the price of gold. I would love to be proved wrong, but I just don’t see it. Maybe in a century.
On the other hand, money on the order of 10 billion should not be an insuperable obstacle if there is a viable business model. Half that much was raised for that satelite cellular system that ended up as a bust.
You know, all predictions of the future are likely to be wrong. Go read science fiction of 50 years ago. We were going to have personal helicopters, moving sidewalks, automated highways (this one could actually happen) and all sorts of things like that, but no one ever predicted that I could sit in my La-Z-Boy, laptop on my lap and communicate with people around the world.
how long do you think a space elevator would last, before some fundamendalist tries to blow the heathen structure up?
love the hotel in space idea…