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Thoughts on the Space Elevator
Keith Curtis writes to tell us that Glenn Reynolds, of Instapundit fame, has posted his thoughts on why NASA should be building a space elevator instead or their current plans. Keith has also posted his throughts from an engineer's perspective (although admittadly still not a rocket scientist). "The challenges are many, but it has been a viable option since carbon nanotubes, structures so strong that one the width of a human hair could lift a car, were invented. A space elevator could be between 10 and 2000 times cheaper than conventional technology and will force NASA to change just about everything they do. Hopefully one day that bureaucracy will wake up and realize it."
Sigh. Ya know, we could build a structure to space with todays (hell, 20+ year old) technology if we wanted. The Launch Loop concept was published 20 years ago and is viable today. It costs less than a space elevator is predicted to cost and, unlike the space elevator, can be built from the ground up instead of from orbit down. So yeah, please stop saying stuff like: once we have strong carbon nanotube fibres we'll have a space elevator two weeks later. It doesn't work like that. The majority of studies that remain to be done to make the Launch Loop a reality are much the same as the many studies that still need to be done to make the space elevator a reality. Someone has got to finance those studies and unless you can get PhD students to do it on government funding that means you've got to pour money into a hole that might never fill up.
How we know is more important than what we know.
this is where private ventures come in. let them take the risks and develope the tech. i'm dubious about space evelvators, but hell it's at least possible in theory if you can find materials that will last
If you mod me down, I will become more powerful than you can imagine....
The August issue of IEEE Spectrum also had a story about the space elevator. This article is available online here. Not knowing much about the space elevator, I found this article very informative.
People keep saying if it fell it would burn up, but it would seem to me that something strong enough to support all the weight needed would be strong enough to withstand any heat generated by falling.
Considering that it wouldn't betravelling that fast, I don't see how it could generate a lot of heat. Compared to say a shuttle reentry.
Wouldn't we also need to build it from space down?
All this is mute until we can make nano tubes as easily and reliable as we make rope.
The Kruger Dunning explains most post on
"But, I don't remember ever hearing that we actually have the technology to produce enough carbon nanotube material to actually build a prototype device of some sort let alone a cable spanning to LEO."
A space elevator must extend to geosynchronous orbit, 36000 km up.
I rarely criticize things I don't care about.
The LiftPort Group of companies working towards a space-elevator are making a great deal of progress. Slashdot reported on the faa approval of their high altitude tests, for example. See here and here for more LiftPort specific information. Check here and here here for several reports concerning the viability of the elevator -- be sure to check the NIAC pdf. Blaise Gassend has a great collection of information. Finally, though carbon nanotubes are still in their infancy (its been a little around ten years since they were discovered) - their theoretical tensile strengths are perfect for application in a space elevator construction. This recent development spells a rosy future, and many innovations yet to come.
http://en.wikipedia.org/wiki/Pixie_dust
It already exists. Just not for what you are thinking about using it for. IBM owns the patent on Pixie Dust. Although I can't see that they care about it anymore now that they sold thier hard drive division.
It's not that easy, the space elevator is supposed to work because it has (will have) a counterweight on geosynchronous orbit that keeps the elevator in place. The space elevator is more like a string tied to a balloon than a wooden stick.
There are two factors in an orbit: altitude and velocity. The elevator will take care of the altitude, so essentially all you need to do is get off of the elevator at the right level, and fire a rocket to get you to orbital velocity. This will take less fuel then launching from the surface. The higher you let go of the cable, the less fuel you need to get to orbital velocity.
"I'm not impatient. I just hate waiting." - My Dad
I've always thought they should consider a variation on the space elevator, where the top was in LEO, and the bottom hung down into the atmosphere. To get things to the top, you simply fly something up high enough that it can latch onto the bottom. Then when you get to the top, you wait for a second one to swing by and take you higher.
It would be like Jungle Hunt, but without the alligators.
You want the truthiness? You can't handle the truthiness!
NASA's Exploration Systems Mission Directorate is already funding space elevator research - John Mankins who was formerly a big cheese at ESMD is a space elevator advocate. One of NASA's Centennial Challenges is to directly foster space elevator work. A Space Elevator is at the moment an idea. Building a space elevator with current technology and expertise may be even less practical than sending humans to Mars with current technology and expertise - much further work is needed but for space elevators the unanswered questions are arguably more fundamental. People love to criticize NASA and point out how company X, Y or Z already has capability A without considering that there are fundamental reasons e.g. to do with energy, systems scaling etc which mean that going to Mars is vastly more difficult than say a suborbital hop. Companies working on prototype space systems and tackling problems in innovative ways should be encouraged by they do not yet provide a certain path towards desired goals like putting people back on the Moon.
Prolog rules
Can be... could be... That's the problem. The tech isn't there. The carbon nanotubes that are long enough, aren't strong enough. The carbon nanotubes that are strong enough aren't nearly long enough.
The tech isn't there. How can they start building something that doesn't have the prerequisite materials? The current plan NASA is proposing they can start building **soon**.
The R&D you need to produce space elevators is currently being performed worldwide by a variety of companies and is well-funded. Diverting $100B isn't going to up the timescale **that** much. Not to mention while it looks good on paper, we haven't even tried a prototype yet.
-everphilski-
A space elevator will be made of carbon fiber nanotubes correct?? What would be the effect on a hurricane hitting the elevator? Can the string be realed in from one end?? Would it be more prudent to build this in a place far away from a coastline??
negliable if built correctly. The local winds wouldn't have enough kinetic force to move the cable much.
"There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."
It's not even the quantity, it's the fact that we haven't been able to assemble macroscopic quantities of them that have anything like the strength of a single nanotube. Weave them at all, and you end up with lateral forces that tear them apart. The highest quality nanotube sheets to date ... are still far from the >100 GPa needed for a space elevator.
And that's not the only unobtanium he's smoking, either. Notice the nonchalant reference to 3He providing power. How much has been spent on fusion power? And how much of that was for 3He instead of 2H-3H? But, yeah, it'll be there as a side-effect of the $6 billion price tag on the elevator.
As long as there is a counter weight it does not need to extend beyond geosynch.
Just a Tuna in the Sea of Life
What you have been talking about sounds similar to a "sky hook".
A variant on a space elevator, it's basically something in orbit that dips down and gets a package from orbit.
Fly me to the moon Let me sing among those stars Let me see what spring is like On jupiter and mars
Liftport is testing weak ribbons. The sort of ribbons they want simply do not exist. It's unobtanium.
I don't know why I have to post this information on each space elevator thread (you'd think people would have gotten it down by now), but here we go again. The strongest measured SWNTs thusfar are just over 60GPa; most were lower. Most space elevator designs call for >100GPa; probably the cheapest and most thought out plan, by Dr. Bradley Edwards (of Liftport fame), calls for >120 GPa.
It gets worse. That's the strength for individual tubes. Bundles are 100GPa ribbon come true.
If you need links, I'll gladly provide them; I just don't want to have to post this every few days. We don't have a space-elevator cable material, and won't any time to, so everyone who says that we should just build a space elevator instead of a new launch vehicle might as well be clamoring for pixie dust.
Also, I can kill you with my brain.
Its just a pie-in-the-sky dream, and will be for the next century(ies). We dont have bucktubes "thick as a hair but strong enough to lift a car". We dont even have them a meter long and strong enough to lift an apple.
Exactly. Wake me up when we have a carbon nanotube bundle as thick as my arm, and as long as my car. Then tell me how much it will cost to manufacture.
Then build a bridge or two out of it, to prove that it's as strong as the theoreticians think.
For comparison, the world's longest suspension bridge is Akashi Kaikyo Bridge in Japan. It has a main span of 1,991 meters, or under 2 km. It cost an estimated 500 billion Japanese yen (U.S. $3.6 billion) to build the bridge. It took ten years to build.
That's for a problem with well understood materials science, done under normal Earth gravity, with normal, terrestrial manufacturing and construction processes.
With the space elevator, people can't even agree on how big it has to be (either 100km, or 36,000 km, or somewhere in between), how strong it has to be, or where it will be built.
In any case, right now it's 50 times longer, and billions of dollars more expensive than the billion dollar bridge: and that's just the material's cost. We can't build a space elevator yet. Why?
If we don't have agreement on a design yet, and we don't have a materials supplier, and we don't have a budget, and we don't have a prototype, and we don't have a plan... how the heck is anyone supposed to build it?
Any decent engineer would throw those plans back on his client's desk, and tell them to come back when they had worked out exactly it was they wanted him to build.
A space elevator isn't going to be built until we have cheap, reliable, and available materials build it out of, until we have machines capable of building it, until we have trained construction technicians capable of operating those machines, and until we, in general, know and agree on what we're building, what we're building it out of, how we're going to build it, what it's going to cost, who pays for it, and who bears the liability for failure.
That day may come. But there's one heck of a lot of materials science that needs to be done first. Build a large carbon nanotube cable. Then build a cheap one. Then prove that you can build a few hundred thousand cables in a cost effective, time efficient process. Then prove that the cables remain strong and reliable under all adverse conditions. Then find a way to mass produce them cheaply and safely, without health hazards to the workers who build them. I doubt that will take less than ten years, probably more like thirty, before we've got the fundamental materials science for carbon nanotubes down.
Once we've done all that, we'll finally have enough data to decide if we can really build a "space elevator", and how much it will cost, and whether the costs will be worth it.
Wake me up in thirty years.
--
AC
Hurricanes aren't an issue.
You would be building this very close to, if not on, the equator. Hurricanes do not form there, and I can't even think of one that has ever crossed the equator.
From TFA: It would cost about $6 billion in today's dollars just to complete the structure itself, according to my study
From the parent: I've heard a similar figure before, and it's amazingly cheap if you think about it.
From me: It's only cheap because it's the amount is at best misguided, or at worst an outright lie.
The worlds longest bridge was just completed in Japan: it cost 3 billion US dollars to build, and took ten years to construct.
The bridge was only 2km long. The smallest distance anyone says we need to reach space is a full 100 km; some people say we need 36,000 km instead.
If we could build a space elevator out of steel (we can't!), and if price scaled linearly with length (it doesn't!), and if we weren't building straight up (we are!), it would still cost around 50 * 3 billion or $150 billion dollars to build.
If the construction time scaled linearly (it won't; we've never built a space elevator before) it would take 50* 10 = 500 years to complete.
That's the time and cost to build a bridge as long as the shortest elevator, without any special R&D costs. That's well more than the $6 billion the article claims, or the $100 billion he says NASA is "wasting" elsewhere.
The article also claims that carbon nanotubes have been manufactured which a lift a car; this just isn't true. He's lying to make things sound good; carbon nanotubes may have that strength in theory, but no carbon nanotube has ever lifted a car.
Carbon nanotubes are currently an interesting research project, not a building material! I can't get carbon nanotubes at my hardware store; they currently only exist in labs, are too tiny to see, let alone build with, and cost more per unit volume than gold! The longest carbon nanotube manufactured to date was only 4 cm! Attempts to stitch carbon nanotubes together have currently ended up with fibres weaker than kevlar; far too weak for a space elevator.
We can't build a space elevator until we first get building materials that are big enough to actually see, let alone construct a 100 km chain out of. We'll also need a minimum of $150 billion dollars, probably much, much more. I'd say multiply the costs by 10 for using a brand new material (nanotubes, assuming can get them working at all ), by 10 for the human costs of untrained manpower, by 10 again for the uncertainty factor of a project that's never been done, and by 100 for working against gravity.
That's 150 trillion dollars; and I think that's a reasonably conservative estimate, all told. If we need the 36,000km version that some experts claim we need, instead of the 100 km that some people say we can get away with, the project just won't happen. Even 150 trillion is a lot; really. We could do a lot of other things with that money...
--
AC
To further back up the parents thoughts... Yes, carbon nanotubes have incredibly high strength to weight ratios. Unfortunately, current synthesis methods yield polydisperse products both in terms of diameter and length. And the longer tubes are ~1-2 microns. Will researchers improve the synthesis methods? yes, eventually. But since nanotech is so well funded these days (and thank god, I cant imagine living on a more meager stipend than the one I'm currently pulling in), there are a relatively large number of groups researching nanotubes, NONE of whom have come up with any earthshattering improvements. The improvements come in small steps, and as a result we wont see anything like this for many many years.
Liftport is testing weak ribbons. The sort of ribbons they want simply do not exist. It's unobtanium.
If you read our literature (blog, press release, articles - heck you can write and ask) you'd discover we're not testing ribbons at all.
What we are doing is testing lifter technology. Sending a bot up and down in a reliable fashion is one of those easy-until-you-really-think-about-it deals. A whole lotta picky engineering needs to be ironed out to make those work in a reliable fashion.
Display some adaptability.
and no this isn't a troll actually visualize part of a frickin space elevator falling into the ocean, or worse on a nearby town.
Only the cables below the break will fall down. The rest of the elevator will fall up.
The space elevator seems to be still hovering at that point where it certainly looks to be theoretically feasible, but where no one really has a clear path towards bringing this construct about in reality.
New rockets are engineering work: we have all the materials we need to use, we know all the physics that describes their behavior, and so as you said there's a clear (albeit expensive) path to figuring out how to put it all together.
A space elevator would still require science work, because the central problem is mass production of materials with properties we only know how to produce at microscopic scales. We can try and pour money at that problem, but who's to say how much it will speed up the solution? Scientific breakthroughs don't usually measure in man-hours and aren't easily predictable in dollars.
We probably ought to try pouring money at the problem anyway. We may soon be able to make cheap material that's stronger than diamond but more flexible than rubber. Even if it isn't good enough for a space elevator at first, it'll be in demand for everything from tires to Gibraltar Bridge cables.
Actually, the design for one of the ribbons was so thin and wide that the wind resistance alone meant that it fell at about the speed of a cardboard box.
See http://www.elevator2010.org/site/primer.html and http://www.liftport.com/faq2.php#science2 for starters, Google for more.
What really makes sense is an infrastructure that makes getting people and payloads in particular to and from space cheap and reliable, even ordinary. The only chance for that right now is a space elevator.
You have a 3% chance of death flying on a space shuttle. That's an incredibly poor record, and incredibly expensive.
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Hmm, I wonder what happened to my post. It's like my second paragraph is all messed up (and my other paragraphs missing). It was supposed to read something like:
It gets worse. That's the strength for individual tubes. Bundles are around 20GPa currently. They're limited by VdW and pi bonding. It gets worse still, however, because the best bulk fabric isn't as good as individual bundles, and are only (5-10) GPa. And even that's not ready for mass manufacture. Notice how many orders of magnitude this is off from what is needed.
Can it be improved? Yes, but not that much. Individual tubes can be made more consistant, and potentially have higher tensile strength (although probably not the earlier theoretical predictions) by tube type selection and refined production methods, but there clearly are major limits on this, and even those things will likely take decades of research before we can approach what their limits are.
Bundles can be improved by longer tubes, but again, they're not going to be stronger than the tubes themselves - only weaker. Getting long tubes (which will strengthen how tightly the tubes end up adhering to each other overall) in a mass-producable method is not going well. The way tubes today are assembled, be it CVD, electric arc, etc, is that the tube is extruded from a gathering sphere of condensing carbon, and it seems to be limited in its capability to grow. Short tubes can be merged, but that makes getting good tensile strength even harder. Instead of the problematic method of using long tubes to maintain bundle strength, you can do pressure-induced intertube bonding (trade sp2 bonds for sp3), but that'll weaken your tube tensile strengths.
In short, both problems, incredibly difficult or even potentially intractable by themselves, help defeat each other. Even with the best of luck and most dilligent research programs, with current tube-strength measurements there's not much hope for a realistic strength fiber any time in the forseable future, if it is even physically possible at all.
Also, I can kill you with my brain.
Since the Moon rotates only once every 29 days or so, the cable would need to be so long that it would hit the Earth, in theory.
Also, in any location other than directly toward Earth or directly opposed to Earth (on the far side of the Moon), Earth's gravity would distort the elevator.
There is a way to place a space elevator on the near side of the Moon, by using the Earth's gravity to counterweight the "top" of the cable, rather than using centrifugal force.
This type of elevator has several advantages:
- It is much shorter than it would otherwise need to be, meaning it uses much less material in its construction, and the material does not need to be as strong as for a longer, non-Earth's-gravity-counterweighted cable.
- The cable goes through L1, one of the Earth-Moon Lagrange points, which is a node on the Interplanetary Superhighway.
- Material mined on the Moon can be lifted "up" the elevator, through the Earth-Moon Lagrange point, then lifted "down" the cable toward the Earth, and deposited directly into Earth orbit.
This last advantage is particularly, uh, advantageous, because such orbits are highly elliptical, and could even intersect the Earth or its atmosphere, which would allow material (e.g., the He3 that you mentioned) to be shipped from the Moon to the Earth without using any rockets at all!The only parts of the Moon that are in constant sunlight are perhaps a very few locations at the poles, which are useless vis a vis a Lunar Space Elevator (although this article proposes a non-vertical Lunar Space Elevator terminating at the Lunar South Pole that could be used to lift water (believed to be located there) into Earth orbit).(Note, however, that it's still longer than the Earth's Space Elevator.)
In fact, such an elevator's cable could be made out of Kevlar!
Search Google for more info.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Uh, I don't know what kind of carbon you're thinking about, but the kind of nanotubes that are used would be neither flammable nor (very) conductive. Any charge built up on the cable would remain fairly local, and not traverse the cable up or down.
-Jesse
Nothing says "unprofessional job" like wrinkles in your duct tape.
No, you're just ignorant. I'll admit that the Patriot is way, way oversold as an anti-missile missile, but if you're in an airplane and someone shoots one at you then you're dead. Patriot was designed to take out Soviet fast movers in the NATO theatre of operations and all of its tests showed that it was very good at that. Taking out missiles is something that it was never designed to do, the Army decided to make modifications to it to try to get some SDI cash in the late '80s. The fact that they had some success is indicative of how well they engineered the Patriot as an anti-aircraft missile.
cheap labor conservatives - they want to keep you hungry enough to be thankful for minimum wage.
> an ego-boosting "been there, done that" trip to the Moon
We're not.
"There are significant differences between the Apollo of yesteryear and the NASA plan of today, Spudis said.
In the first place, the systems making up the vehicles are being designed for maximum leverage: long-life, cryogenic-based propulsion, with potential reuse in space, Spudis explained.
Secondly, the mission is different.
"In Apollo, the mission was to prove we could land on the moon and return safely to Earth. In this case, the mission is to determine the best site to collect and use the resources of the moon and to emplace the necessary infrastructure to do so," Spudis said....
In point of fact, Spudis continued, "Apollo, for all its beauty, was essentially a technical dead-end ... one-use systems, storable propellants, a paradigm of launching everything from Earth."
Spudis told Space.com that this system, as blueprinted by NASA, is designed from the beginning to adapt to a different paradigm: the use of off-planet resources -- lunar-manufactured propellants -- to create a permanent transportation infrastructure in cislunar space, the territory between Earth and the orbit of the moon."