Space Elevators Going Up 473
MikShapi writes "CBC is running a new piece on the Space Elevator. Nothing dramatically new, as we're all still waiting for one of the many Carbon Nanotube research centers to announce they reached the famous 100GPa red line from page 10 of the NIAC Phase 2 Report, thus obtaining 'unobtainium' [pun intended], the material necessary to build the Elevator. The report predicts this will happen during the course of the next two years or so. It's then that the fun really starts - A REAL all-out space race, open to everyone with will and a national budget, winner probably getting to own space [read last paragraph]. In the meanwhile, we can all spread the word, discuss, debate and brainstorm every nook and cranny of the program here on Slashdot, and give Edwards a shoulder by giving the program every bit of mass-exposure we can."
Top floor.. (Score:5, Funny)
Re:Top floor.. (Score:5, Funny)
Re:Top floor.. (Score:5, Funny)
Re:Top floor.. (Score:4, Funny)
You'd need a very fast way to defy gravity and climb that cable. I say screw the cable. We need bungee cords. it's going to increase the speed at which we can get objects into outer space. Not to mention the revenues stream from all those GenX Addrenalin junkie millionaires out there that would want a ride.
Re:Top floor.. (Score:5, Funny)
Re:Top floor.. (Score:5, Funny)
Re:Top floor.. (Score:5, Funny)
After 63,000 miles of listening to elevator music, everyone will be insane!
Re:Top floor.. (Score:4, Informative)
The top orbit will have "gravity" in exactly the opposite direction because it's spinning faster than than the required speed to stay in orbit. It has to pull on the cable to keep it from falling down.
It is somewhat like going through the earth. As deeper you go the gravity will diminish. In the middle of the earth: None. On the other side the gravity will increase again but in the opposite direction.
Emergency open / close buttons (Score:5, Funny)
Re:Emergency open / close buttons (Score:5, Funny)
I wonder if anything bad happened to them?
KFG
Re:Emergency open / close buttons (Score:4, Funny)
Doubtfull (Score:5, Insightful)
A REAL all-out space race, open to everyone with will and a national budget, winner probably getting to own space
I predict that there will not be a space race, because the cost-benefit isn't acceptable yet. If this technology is only 2 years away (doubtful again), then there would be massive funding to accelerate the program if there was enough interest. Lack of interest now means that there is probably not going to be much interest when the nanotubes arrive.
DoggRe:Doubtfull (Score:5, Insightful)
Re:Doubtfull (Score:5, Informative)
Re:Doubtfull (Score:4, Insightful)
Re:Doubtfull (Score:4, Informative)
Can you say "bullwhip the size of a planet"? I would NOT want to be beneath the path of that thing if it broke. The tsunamis would be interesting too.
Actually, there should not be too much of physical backlash or impact from it - the majority of the cable would burn up when entering the atmosphere. The main danger, as covered in the article and Edward's report, would be the danger from inhaling nano-tube particles. Some early results of rats exposed to nanotube inhalation have been pretty negative.Re:Doubtfull (Score:5, Funny)
OPENING OF NEW SPACE ELEVATOR ENDS IN FIASCO
During the official opening of the first space elevator
a tragedy happened when the president was asked
to "cut the ribbon". This prematurely destroyed the
twenty billion dollar project, sending a rock with a
100,000 km long ribbon attached to it into space.
Read more on pages 2, 3, 4, 6 and 8.
Re:Doubtfull (Score:4, Informative)
I do appreciate the joke, but if you were to actually cut that ribbon at ground level, all that happens is that the space elevator goes into a slighly elliptical orbit: the cut end of the ribbon ascends a few miles into the atmosphere only to come back down 12 hours later to pretty much the same location, where it can be snagged and re-anchored (same procedure as when the elevator is first lowered from orbit). A mishap for sure, but nothing more.
Re:Doubtfull (Score:5, Insightful)
Though the orbit is geosynch, it isn't because of the distance of the center of mass of the thing. It's the distance of the center of mass of the thing while tied to the ground.
Let it go, and it gets an elipitcal orbit that is NOT geosynch, and the thing comes back from it's elipical orbit somewhere else on the same latitude.
Next, you are also assuming the thing does not have any "springyness" and bunch up on itself.
Not a trivial problem.
I bet you a taco dinner that if the cable gets cut on the ground it never comes back in a way that can be used.
Re:Doubtfull (Score:5, Interesting)
Re:Doubtfull (Score:5, Insightful)
However, I think there's a majorly false claim in there, which is that the first owner will lock out everyone else. Obviously, the first order of business when you have a space elevator is to put up more of them, and for a while they may indeed have a monopoly. But given the resources still available on Earth, someone will eventually tender an offer for a fully-completed cable that the first entity can't refuse; no matter how valuable the cable, it is possible to pay the owner off today with $X dollars, which the first entity will (correctly) perceive is more valuable to have it in liquid form, available to then invest back into other things. That price may be sky-high, pun semi-intended, but there are people on Earth who will be able to afford it.
By buying a completed cable, they can jump-start themselves up, and as more and more entities do this, it'll start looking more even. While the first mover will have a true advantage that may last a very long time, I don't see a situation where they maintain a 20x advantage over everybody in perpetuity; the value proposition of liquidating one of the cables is just too appealing.
This assumes a capitalistic owner of the first tether, and if the US gets there, the world can for once be glad that we see everything in terms of dollars, sooner or later, because that means that we will indeed have our price (though in the truest capitalistic tradition, it will be all the traffic can bear!). If it's not the US, well, it depends on who gets there first, but even so, it would take a very strong government to turn down the offers it would get... some of which are quite likely to be of the "offer you can't refuse" variety. ("Dear China: We still have nukes. Sincerely, All Nuclear-Capable Countries.") I still can't imagine a plausible long-term scenario where somebody maintains a massive, multiplicitave lead indefinately, though again, serious short- and medium-term advantage do accrue to them. (If nothing else, they'll need to draw on international capital to invest in space itself.)
Re:Doubtfull (Score:4, Interesting)
In any case, regardless of the economics, there are several countries which will want to have their own space elevators, simply for reasons of national security or prestige. The US would not be at all happy with the idea that China could cut of its reasonably-priced access to space, for instance. So, don't expect anyone to have an elevator monopoly for long.
Re:Doubtfull (Score:4, Interesting)
That's correct, because the exponential growth will begin several years *before* the space elevator is operational, as soon as it looks like the project might actually succeed. Do you know how airplanes, satellite launches, RAM, and other items dependent on scarce, expensive manufacturing capabilities are procured? Companies purchase options for these things decades before they actually need them. In fact, much of the manufacturing capacity is *financed* through such options. Why would the space elevator be any different?
nobody invests in things [that don't exist yet]
*Investment* is by definition in things that don't exist yet. Otherwise it's called a *purchase*. Investors are very well capable of looking years ahead and weighting risk vs. profit.
it will take years of R&D before the new stuff that will be created will actually be ready to load on an elevator.
A communications satellite that goes to GEO by space elevator differs from one that goes to GEO by rocket only insofar as the former has to suffer far less g-forces on ascent and can therefore be built more cheaply.
The US would not be at all happy with the idea that China could cut of its reasonably-priced access to space, for instance.
Like they're not at all happy that China could cut off its reasonably-priced access to clothes, shoes, and electronics, for instance?
"Old Wealth" in the US? (Score:5, Informative)
Have you ever looked through the Forbes 400? "Old money" in the US is largely a myth.
The ten wealthiest individuals in America are Gates, Buffett, Paul Allen, Larry Ellison, Michael Dell, and the Walton heirs. (Steve Ballmer is 11th, incidentally.) Of these, only the Waltons inherited their money, and that not from some ancient rail baron, but from a self-made man who died in 1992.
100 GPa red line is not enough (Score:5, Interesting)
I'm more interested in the length of the nanotubes than in their strengh since increasing the strengh is quite easy (basically all we need is to increase the fraction of carbon nanotubes in the composite) compared to increasing the length of the composite.
Re:100 GPa red line is not enough (Score:5, Informative)
While there is a difference between achieving 100 GPa over very short lengths and over 100,000 kilometers, it's not as much as you might think.
The longest individual nanotubes we can reliably produce are on the order of a couple of centimeters. But once we have nanotubes on the order of a meter long, they will probably be sufficient to produce a long ribbon with sufficient loading on the nanotubes themselves.
The limiting factor is not the length of the nanotubes in a composite (beyond a certain point, anyway), but rather how effectively the nanotubes themselves can be made to bear the load. Nanotube exteriors are slippery, like graphite, so the challenge is being able to stick them together in a substrate the transfers load effectively between them.
For this, a process known as "functionalization" comes into play. This basically means adding small appendages to the nanotubes so that they have more traction within the substrate.
LiftWatch.org [liftwatch.org] carries regular space-elavator news items. Here are some recent articles on CNT advances:
Re:100 GPa red line is not enough (Score:4, Informative)
*This assumes that each section of the elevator has the same mass as any other equally long section.
Re:100 GPa red line is not enough (Score:4, Informative)
The carnage would be non-existent. The proposed ribbon has the approximate shape, weight and composition of carbon paper (remember those?). All but the lowest few km would burn up in the atmosphere. The rest might land on your head with all the force of a fluttering sheet of newspaper [www.isr.us].
Read Kim Stanley Robinson's Red Mars. Skip to the last few chapters if you just want the space elevator stuff.
The truth doesn't always make good fiction, and good fiction doesn't always tell the truth.
Re:100 GPa red line is not enough (Score:4, Informative)
You've missed a zero - last time I've checked [wikipedia.org] high-strength steel alloys were below 1 GPa.
The "cable" is going to have to be pretty substantial.
You're missing the point: since virtually all the tensile strength is required to support the mass of the ribbon, that ribbon must perforce be both extremely tough *and* extremely light. Plans call for a ribbon weight of only 7.5 grams per meter, which is actually less than a sheet of laser printer paper.
I think it would hit the ground, relatively intact, at supersonic (but nowhere near asteroid) speeds.
Nonsense. The proposed ribbon is made of carbon, and thus has the aerodynamic and chemical properties of an extremely long and tough piece of paper. In other words, any pieces accelerated to high speed by orbital dynamics will burn up; any remaining fragments will flutter harmlessly. The only extant concern is the potential release of (potentially carcinogenic) free carbon nanotubes; this needs to be investigated.
All of which you would already know if you'd bothered to follow the link I provided instead of arguing from ignorance.
Fwoosh! (Score:5, Funny)
Well, that's fine. Calculate the length of that sucker just right and you've got a quick, exhilarating way to travel from one point on Earth to another.
Huh??? (Score:5, Funny)
OK for someone who can hardly remember a thing about High Scool Chemistry, Unobtainium, what's that? A new term for good karma?
Re:Huh??? (Score:5, Informative)
Re:Huh??? (Score:4, Informative)
Re:Huh??? (Score:5, Funny)
And once it's obtainable, it will retain the name "unobtanium", because administratium will continue to be a necessary component of any NASA project. If you aren't aware, administratium is the only element whose atomic weight increases after fission.
Oh, oh yeah? (Score:5, Funny)
Not if our brand-new Department of Homespace Security has anything to say about it!
Imagine, if you will, a solid 3D column of security, with an outer edge in the shape of the U.S., starting at the U.S. and extending infinitely into space. I think if we tried, we could even make it glow the whole way. Put a scare into some of those E.T.'s.
Re:Oh, oh yeah? (Score:4, Funny)
yeah yeah troll, flamebait, yeah whatever
Put the elevator in Cayambe, Equador (Score:3, Interesting)
Re:Put the elevator in Cayambe, Equador (Score:3, Insightful)
Re:Put the elevator in Cayambe, Equador (Score:5, Informative)
Re:Put the elevator in Cayambe, Equador (Score:4, Informative)
This is good and all....but (Score:4, Funny)
Re:This is good and all....but (Score:5, Informative)
According to the book, the plan is to send up a rocket with the smallest possible cable. The cable gets lowered to Earth and secured (cable also gets spooled out in the opposite direction, in order to keep the spacecraft in orbit). Then they send up a series of progressively larger robots along the ribbon. Each robot adds more material to the ribbon as it climbs, and when it gets to the top of the ribbon, it stays there to add to the mass of the counterweight. So basically we bootstrap our way up.
Better Space Sation ? (Score:3, Interesting)
Re:Better Space Sation ? (Score:3, Interesting)
One should hope so, shouldn't one?
Re:Better Space Sation ? (Score:5, Informative)
With the competition that all of this new technology is/will be producing, a commom point like the ISS is important to unite the major countries.
Re:Better Space Sation ? (Score:4, Informative)
The ISS however, is moving at about 6-7km/s, in a different orbital inclination, barely a few hundred k's up. Getting material from the elevator to the ISS is going to be rather tricky.
I hope they've done all the sums involved with regards to moving the base of the cable around a bit, wouldn't want it to get severed by a LEO satellite.
Re:Better Space Sation ? (Score:5, Funny)
What does the Space Station do?
Re:Better Space Sation ? (Score:3, Interesting)
I doubt that very much.
It's not in a geosynchronous orbit, and it's not in an equatorial orbit.
The platform from which the cable is lowered to the Earth (and from which the counterweight is "raised" away from the Earth) must be in an equatorial geosynchronous orbit, in order to remain above the same location on Earth at all times.
Moving the ISS to such an orbit is probably not cost-effective.
My guess, though, is that the ISS could (and probably w
Star Trek... (Score:5, Funny)
What does human advancement require? (Score:5, Insightful)
But they go hand in hand with each other. Unless we truly believe Matthew 5:5, that the weak will inherit the Earth, it will take a worldwide view of humanity to move us to the next stage of human advancement which is the eventual separation of humans from the Earth and into the galaxy. We can go this alone, leaving the world's poor to their own devices, while the space superpowers leave them behind. However, when the day comes that certain small groups of humanity take to the heavens leaving this world and venturing off into the depths of space, how will history treat those of us living now who failed to hold the hands of those unable to stand with us as we raised humanity to new heights?
The space elevator is a great achievement. Hopefully we will begin to have a true space-based space program that is not dependent upon sending rockets to the space station. This would be the largest step in the path to Earth separation since the first manned space programs.
However, taking steps only with our strongest leg means we are still limping. We must strengthen all our limbs as members of the human family, IMO.
Re:What does human advancement require? (Score:5, Interesting)
Re:What does human advancement require? (Score:3, Insightful)
Think of all the fuss made about the outsourcing of jobs. These jobs are a perfect way for Indians to earn money and rise above poverty. That is way people should be helped: give them an oppurtunity. Instead, people (such as prospective presidents) are trying to eliminate this! *sigh*
Then there is this War on Terror business. Although many people will argue that it w
The "weak" will inherit?! (Score:3, Interesting)
A more accurate interpretation suggests that those who inherit the earth are exactly the opposite of weak. Instead, the "meek" originally intended was a word to describe a ready and willing warrior. My university's Bible professor likened it unto the steed of a knight. Eager for
Re:The "weak" will inherit?! (Score:4, Insightful)
Can you give me a reference for this? The OED has no mention of this inversion of meaning. The closest it gets is the primary obsolete meaning, "Gentle, courteous, kind. Of a social superior: merciful, compassionate, indulgent." (see http://dictionary.oed.com, subscription required).
Wrong, according to Strong's Concordance (Score:5, Informative)
In other words, Jesus was saying that the humble and mild-mannered will inherit the Earth. You can find this same word commonly translated as meek in 1st Peter 3:4. Also, if you look at the context of Matthew 5:1-13, the opening of one of Jesus's sermons, it's quite clear that he's saying that rewards await the humble and downtrodden. They "are the salt of the Earth" and there is not an aggressive or angry group among "the poor in spirit," "those who mourn," "the meek," "those who hunger for righteousness," "the merciful," "the pure of heart," or "the peacemakers."
I'd be very surprised if Strong's Concordance was wrong on the issue given the context and the modern descendant of the word. I'd love to see some evidence for your professor's claims.
Re:What does human advancement require? (Score:5, Insightful)
I'm sure that more is spent on any one of: cosmetics, fizzy drinks, cigarettes, SUVs, cocaine. If you're just talking about govt expenditure; at least 100 times as much is spent on the military.
If access to space is much cheaper, the benefits to the world will be immense; though it'll take a few decades. Even back in the 70s when O'Neill advocated space colonies in the L5 orbits it was possible to make a case. With a much cheaper launch method it becomes compelling.
Re:What does human advancement require? (Score:4, Informative)
We've all benefited greatly from weather and telecom satellites.
Note these are both forms of information -- to get physical goods and energy, it's still much too expensive. Thus a radically cheaper way to get to orbit will make much more possible (solar energy collection, asteroid mining, to pick a couple at random).
Re:What does human advancement require? (Score:5, Insightful)
Were it not for exploration and technological advancement, we would almost certainly still be living as serfs to some fuedal lord.
When the US was founded as a large republic, many people thought it would never make it. The success of representative government has improved the lot of many people, and arguably, the poor of the entire world.
Now, we are all at a standstill. There is no place for people to go who seek to try something new. There are no experimental governments anymore, and there are no nation-wide experimental social systems. Individuals or small groups fight to improve the world, but there's nothing to be done against the inertia of the status quo. Things will improve, but slowly.
Space offers that opportunity we need. Naive people see space as a playground for the rich. If we're going to have a playground, we're going to need to build it. The first people who will go permanantly up in a space elevator will be construction workers and engineers.
When you take into account the resources available, and what it means for an end to mining and power production on earth, you have a pretty powerfull vision.
It's remarkably short sighted to argue against taking ALL of humanity a step foward because we're not all on equal footing. We NEED to take this step foward, DESPERATELY, in order to help solve poverty, exploitation and many other ills in the world.
Re:What does human advancement require? (Score:5, Insightful)
With all due respect, I call bullshit. Your arguments and the parent post's arguments are simply so much sentimental claptrap.
There's so much clamor for 'intellectual honesty' in the current political climate, let's start here.
Let's call a spade a spade. Space exploration is worthwhile because we, as a society, have decided that the enrichment of human knowledge is a virtue per se. Knowledge for the sake of knowledge. Human endeavor. It needs no other rationalization.
To say that space exploration is worthwhile because of unrealized, indeterminate side effects that are not the goal or intention of the pursuit, but held up, nevertheless, as some sort of social promisory note is just sophistic rhetoric. Tomorrow, I'll go tell the homeless guy down the street the good news: "Worry not, dear poor person, for we are building a space elevator that will elevate the dignity of all humankind, and so too shall your station rise!" Yes, and then I'll go tell the patients in the oncology ward that we shall cure cancer by building flying cars, for surely some modicum of the technology needed to build a flying car will make cancer fly from the body as well.
Here's the thing: Multiple fronts. Society proceeds on multiple fronts. We don't stop space exploration because we have sick and poor people. We don't stop researching epilepsy because we have diabetes, stop researching diabetes because we have AIDS, stop researching AIDS because we have cancer, stop researching cancer because middle aged men have erectile dysfunction. What we DO do (giggle) is engage in a torturous debate in resource allocation. In terms of real life application, space exploration is an incredibly expensive, high risk investment with a possibly high payoff potential on a very far time horizon. But in the short term, we learn a lot about how the world works. This does improve the human condition in some abstract sense, but to say that it is a necessary step to curing some of our pressing social ills is disingenuous. The way to address our pressing social ills is to, you know, address our pressing social ills. We just have to figure out how to do that in a responsible way and still leave enough money over for the purer, less immediately tangible pursuits that we collectively value. Doing this factor analysis well is the hallmark of good government.
Two books... (Score:5, Informative)
The Fountains of Paradise by Arthur C Clarke and Red/Green/Blue Mars by Kim Stanley Robinson. Both discuss the politics and sociology surrounding the construction and use of a space elevator. Good books, well worth a read.
Re:Not to be picky or anything... but.... (Score:4, Interesting)
Wouldn't that actually be four books?
Technically, yes. But in a shoot-off between the cheap Merlot I am currently drinking, and the cheap (and obvious) point you are making, YOU LOSE! (in a diplomatic sort of way, not meaning to put you down, you understand, but, like, the Merlot is getting me drunk, what are you doing to help my plight? Savvy?)
Well if its built in the US (Score:5, Funny)
650 tons of material. (Score:3, Interesting)
Re:650 tons of material. (Score:4, Informative)
At the time the scientists were looking to get enough Uranium (238) and Plutonium to build the bomb. Everything else around was ready but they were producing only grams of the required materials a week.
In only 2 years they improved the production quality and quantity dramatically to levels they didn't even dreamed of before.
That's when they understood that what they though was granted long before (the 'rest' of the engineering needed for the bomb) was the actual hardest part to 'build'.
Maybe this will happen to the space elevator with the nanotubes.
Re:650 tons of material. (Score:4, Informative)
Bouyant cables! (Score:3, Interesting)
Why not create a chain of bouyant cables [slashdot.org] instead of focusing on strong and light ones made from carbon nanotubes??
Re:Bouyant cables! (Score:4, Insightful)
Re:Bouyant cables! (Score:3, Funny)
And the good lord google said: even my children have flown over 82,000+ miles or 131962.6 kilometers using boyancy, which is way above AC's stated 35,785 km geostationary orbit my child.
So lord google, what is the altitude for geostationary orbit?
And the lord google replied: 35,787 km above mean sea level.
That was 82000 FEET = 15 miles.
This may be the coolest thing I've ever seen (Score:5, Interesting)
Listening to him go through all the numbers and technical details you're left not only with the amazing scope of the thing but the feeling that, ya know, we might just be able to build this thing!
G.
Nanotubes made out of carbon (Score:5, Funny)
Such is the case with a group of scientists from the National Research Laboratory in Los Alamos, N.M. (''Los Alamos'' is Spanish for ''More than One Alamo''). According to an Associated Press story that I am not making up, these scientists are proposing to build an elevator that would be 62,000 miles high. That's right: 62,000 MILES, which is 32 million stories. At the top would be a revolving restaurant serving what the scientists promise will be ''really mediocre food.''
- Dave Barry [miami.com]
test planet (Score:4, Funny)
build one there first maybe?
Love in an elevator... (Score:5, Funny)
Can you imagine making love in THAT elevator?
Talk about Mile High Club...
don't be so quick... (Score:5, Informative)
To make a long story short:
They did it.
By finding a way to dissolve nanotubes, then slowly concentrating the solutions, they formed a liquid crystal of nanotubes. By extruding this through a syringe, they formed an aligned, macroscopic, nanotube rope.
I've seen this stuff... somewhere, and it looks just like black string.
What's left?
They used tubes grown by high pressure carbon monoxide, which leads to a lot of defects. If they switch to methane, the defects will largely be gone, but the yeild drops.
They probably need to chemically connect the tubes. You can do that with an electron beam, but that would be a pain industrially. I'm sure there's a way around it.
I'm sure that same group of people has already figured out many more problems and solutions than I can think of. I havn't seen anything out about the mechanical properties of these ropes yet, but I would expect something within a few months, and I would be surprised if it wasn't amazing.
I used to be a skeptic when it came to a space elevator, but now...
Re:don't be so quick... (Score:5, Informative)
Here's the link to that article you just spoke of:
Phase Behavior and Rheology of SWNTs in Superacids [acs.org]
For those of you suspcious of "blind" links:
http://pubs.acs.org/cgi-bin/sample.cgi/mamobx/200
Re:don't be so quick... (Score:4, Interesting)
There are some pictures of real carbon nanotubes in plexiglass containers available here [liftwatch.org], taken with my crappy digital camera at LiftPort [liftport.com].
Cool story: at one point some of this material, which looks more or less like soot, spilled onto the flat, seemingly smooth table top. After wiping it off, there was a permanent black smudge left on the table top that no amount of scrubbing would remove... some of the nano-scale CNTs had slipped down into the microscopic grooves and divots on the table surface!
Can Imagine this Erection ! (Score:4, Funny)
A second note that almost killed me with laughter was , well let me start with I used to be in the building trades, one day while at a supply house, a New blue truck pulled up, the sign on the side ? "Short STEEL Erection" I was dying, they specailzed in Steel reinforced concrete. I always love that one I think they were out of Canton OH
Nobody is going to build one of these. (Score:4, Interesting)
This isn't a harmless piece of cable we're talking about. The real barrier is going to be whether or not it'd be dangerous if it breaks or if it's cut. If it'll burn up and IF the burnt nanotubes aren't dangerous then maybe there will be a snowballs chance in *$#@ that the public will ok such a project. You can be guaranteed that if it's dangerous though that everyone will just assume that it will break or be broken intentionally.
Re:Nobody is going to build one of these. (Score:3, Informative)
I remember reading about this concern somewhere. The idea was that the carbon nanotubes would be stretched almost as thin as paper. Should the ribbon break all that would happen is the ribbion would float back to Earth like paper and no one would get hurt.
no g-forces _and_ weightlessness? (Score:3, Interesting)
You'd also have a hard time interacting with any orbiting satellites (except those in a geo-stationary orbit) because they'd be flying by at 13,000 mph.
"We have to fix the satellite. Here it comes, I'll grab it with my giant catcher's mitt... WHOA! That almost took my head off! Well, at least it won't come around again for 90 minutes."
Defects will kill the project (Score:3, Interesting)
As a structural engineer... (Score:5, Interesting)
For context: the most common type of structural steel currently used has a yield strength of 350 Mpa. 100 GPa is 285 times stronger. And stronger isn't enough, it has to be dependable and resistant to cyclicle loading and fatigue, which isn't easy to quantify, especially under such unusual conditions.
To suggest that this can be achieved in a couple of years sounds silly to me, considering whatever material used would a lengthy term of testing and a proven track record before sinking billions of dollars into it.
Ridiculous, but plausible... (Score:5, Insightful)
Yes, it sounds outrageous, but it's theoretically possible to do this with nanotubes, apparently. As I understand it, nobody has actually demonstrated a macroscopic piece of nanotube composite with this kind of strength though.
True, but the things made possible with such a material would surely attract billions of dollars worth of R&D. Can you imagine what it could do for things like aircraft design?
Re:Ridiculous, but plausible... (Score:4, Insightful)
General Products Hull's here we come!
My prediction (Score:4, Interesting)
Re:My prediction (Score:5, Insightful)
What's sad is that it may well take that long.
However, the best thing we could do to promote the sky elevator is to develop and build nonotube-based structures here on Earth.
For example, if you were to rebuild the Golden-gate bridge in San Fransisco with nano-tube cables instead of steel cables, would they even be visible from the shore?
An impressive, previously infeasible structure, such as a bridge spanning the entrance to the Mediteranean, or across the English Channel would do much to get everybody used to the idea that something like this could, in fact, be done.
Also, projects like this would give us opportunities to answer questions about its durability, relability and safety in a large number of circumstances.
Building a space elevator with nanotubes as the first project is fundamentally stupid. Build something more reasonable first!
Hmm (Score:5, Insightful)
1/625 possibility of being destroyed in 2031 (Score:3, Insightful)
Re: Splitting hairs (Score:4, Informative)
There's a 1/100,000 chance of being destroyed by the leonids in any one of the 'minor' leonid years. And this is ignoring all of the other mundane risks such as cumulative damage by oxidation and the like.
None of those mundane (or outlandish) things you mention have anywhere near that kind of risk profile.
Why individually? (Score:4, Insightful)
Do your elevator pitch (Score:5, Insightful)
On a serious note, they predict it would be hit, if not moved, by a large space object around once a year. They think they can spot these objects and move it as needed. But what about smaller objects. How much damage will they do? How easily can they be detected? How often will they hit?
And worse, what about deliberately launched smaller objects, radar-invisible small objects fired by a nation that doesn't want another nation to own space.
Economics (Score:4, Interesting)
Just to pick some numbers:
Space elevator: $5B each, one 4 ton payload per day
Nanotube composite rocket: $.1B each, one 8 ton payload every two days
In other words, it will never happen.
Only $5 billion? $500 billion maybe. (Score:5, Insightful)
More people fly from the UK to the continent these days because it's much cheaper, faster and more flexible.
A WEEK?! (Score:3, Insightful)
I wonder if there's any chance that it could use a maglev system. Japan's at 581kph or so. If you could fly straight up at even 500kph that cuts the trip down to 3 days.
Cost (Score:5, Insightful)
NASA is the reason space is expensive. Companies like Starchaser and Scaled Composites are the ones who will make space cheaper and will "own space".
Cable propagation lessons from the launch loop (Score:5, Insightful)
As a climber goes up, the surface anchoring system must pay out more cable to fill in the less tensioned region under the climber, faster and faster as the climber accelerates up the cable, proportional to the speed of the vehicle, total acceleration (including gravity) and inversely proportional to the mass per meter and the square of the propagation velocity of the material.
This is continuously changing, so forces and velocities at the surface are changing also. The problem is, this is an underconstrained and essentially undamped end-terminated system - as the cable gets very long, you develop big standing wave complexes with only two points (surface and top anchor) to remove or store the energy. Keeping the standing waves from building up is difficult, but not impossible. However, it does add an additional constraint on launch rate; you have to spend a lot of time damping out the waves, even granting that these people are more clever than I am at modelling and removing this energy.
Tapering of the cables, necessary even with magic nanotube unobtainium, makes the math even more "exciting", with the additional constraint that the through-atmosphere sections, along with the sections that dip into the atmosphere during wave motion, have to be thoroughly protected against atmospheric degradation (hint: C + O2 -> CO2 ). The portions of the system below the Van Allen belt have to be armored against atomic oxygen damage. Atomic oxygen will burn off the leading edge of ISS at rates approaching a millimeter per decade; the space elevator will be stationary in the gas field, but there are still a lot of fast moving oxygen atoms up to, and through, the radiation belt.
All motor driven systems have limits to their power-to-weight ratio. To get to GEO, we have to add about 60MJ/kg. If we take 33 hours to do so, we need to move an average of 500 watts per kg (total climber weight) through the (photovoltaic or microwave) energy collectors, motors, rollers, etc. For comparison, a 1500 kg sports car with a 300 horsepower gasoline engine uses 150 watts per kg. However, that underestimates the problem. Most of the energy will be added at the beginning of the climb, during the first 10% of the travel distance, as the climber leaves the depths of the gravity well, so expect thousands of kilowatts per kilogram in the power train during this phase. If there are unexpected variations in the power, the change in climbing acceleration will add more ripples to the cable.
I tried to avoid these problems with the launch loop (see URL below) by keeping the altitude under 100 km and the motors on the surface. Even over those "short" distances, cable propagation issues are problematic. Funny/bad things like lightning, ice buildup, fractally gusty winds, and jittery payload forces require special attention, and all reduce the capacity of the anchoring and stability cables. Everything above the atmosphere is exposed to a steady rain of the garbage that your launch system has accumulated in orbit (it all comes down, eventually). Reentry systems for human payloads (in case of failure) add weight. Problems, problems.
At the end of the day, though, the killer issue is lack of demand. The launch loop, with about the price as a space elevator (+/- 3dB) and using materials and technologies we have had for two decades, can put 80 tonnes of payload into orbit *per hour*, for less than $10/kg. Unfortunately, nobody wants that much mass in orbit, even at that miniscule price. Perhaps "if you build it, they will come", or perhaps you end up with another white elephant lik
Re:Uh.. (Score:5, Insightful)
Two different elevators guy. One on mars and another on earth. For lauching payloads from both planets. We are going to eventually have to travel home from mars....
Re:Uh.. (Score:3, Funny)
Re:Unobtainium (Score:5, Interesting)
I'm not the least bit concerned about the carbon nanotubules. I'm still trying to figure out how their going to ATTACH the damn thing. All buildings are essentially resting upon the Earth. This thing can't rest, it needs to be attached. For a cable this long, a "stupid hurricane" could set up a vibration is going to build to the point where the whole thing starts "walking" across Columbia.
Re:Conservation of angular momentum is the fatal f (Score:5, Insightful)
There ain't no free ride into space: The elevator will simply replace violently exothermic chemicals with the slow sapping of earth's rotational energy.
Re:Conservation of angular momentum is the fatal f (Score:5, Interesting)
The site doesn't actually run through the numbers or mention how long this recovery time would be. The logic does make sense -- if the tether becomes slanted relative to the surface of the earth (my objection), then by definition there is a lateral component to the centripetal force on the tether, which should allow the sky station to steal some angular momentum from the earth. at some unspecified rate.
The site doesn't actually run through the numbers or mention how long this recovery time would be. If any physics mavens are irritated enough by my parent post to actually run the numbers, I'd be genuinely interested in seeing the solution worked out.