Space Elevator An Impossible Dream? 448
bj8rn writes "Three months ago, the dreams of a space elevator finally seemed to be coming true after a successful test. An article in Nature, however, suggests that there's reason to be pessimistic. Ever since carbon nanotubes were discovered, many have been hoping that this discovery would turn the dream into reality. Pugno, however, argues that inevitable defects in the nanotubes mean that such a cable simply wouldn't be strong enough. Even if flawless nanotubes could be made for the space elevator, damage from micrometeorites and even erosion by oxygen atoms would render them weak. It would seem that sci-fi will never be anything other than what it is: a fiction."
Never? (Score:5, Insightful)
It would seem that sci-fi will never be anything other than what it is: a fiction.
Never? That's a very, very long time. I would never bet against never. Never always wins. (Especially if you believe in an infinite universe.)
Successful Test?!? (Score:5, Insightful)
Reason #0 to be pessimistic: A "successful test" isn't a climbing robot. The climbing robot isn't the hard part of the problem. The hard part of the problem is the materials science.
Nor is it the sort of discoveries we've seen in the materials side of the equation; fibers measured in millimeters. That's not a prototype, it's just basic research. Interesting basic research, worthy basic research, and good basic research to be sure, but it's not a demonstration of practicality by any stretch of the imagination.
When someone builds a small footbridge out of these things, I'll be interested. When you can scale that to a mile-long suspension bridge that supports two lanes of traffic in each direction, I'll be optimistic.
Never say never (Score:3, Insightful)
It always amazes me how a spider can weave a thread which is so strong and flexible yet for all our mastery of the earth we cannot yet reproduce its properties.
I believe we will find a pathway to the stars, whether it is a single tether or an entire webbed tower I don't know but I am not ready to give up on mans' inginuity.
Psha! (Score:3, Insightful)
Which is, of course, always the case. But the starry-eyed folk have always known they'd have to engineer some constant repairing mechanism. I just don't see how this is a big deal.
unwarrented negativism (Score:5, Insightful)
There is so much that we don't know about the physical universe, that to even say we are beginning to understand what is possible is silly. Faster than light travel? Possible or not? As far as we have observed, not. Does that mean it's impossible? NO! We aren't even sure what time/space is, how can we say what is and isn't impossible? Is a space elevator impossible, just because this one method might be impractical? NO!
Somehow I wonder if the submitter was just trying to sound sensationalistic to make sure his story got accepted. And I just fell in his trap. Oh well. He did seem rather gleeful about the whole thing, though.
Impossible (Score:4, Insightful)
Re:Never? (Score:5, Insightful)
Sure, carbon nanotubes are neat, and gave us the impression we could build stronger structures and materials than previously. But why does their existance mean we're sure to find something equally strong AND able to withstand being a space elevator cable?
Don't get me wrong - saying 'never' is unwise, but it's almost as bad to assume humanity will be capable of everything one day.
Re:Wireless Elevators (Score:4, Insightful)
This would naturally also make any kind of "power beaming" technology interesting, even if it would be quite inefficient, as long as it could be transformed into significant thrust easily in the receiver.
Re:Never? (Score:5, Insightful)
Re:At Last (Score:3, Insightful)
What you propose is essentially what's being done. A small amount of money is being placed into theoretical research on Space Elevators, and that is what gets into the news because they are fun to think about, but the vast bulk of the money is (quite rightly) being spent on basic carbon nanotube materials research -- which is a good investment whether we end up building space elevators, or not.
As it is we're just pouring money into a money pit of a dream impossible with today's technology. Typical of our government... missle defense anyone?
Can you point to any actual figures about how much money is being wasted on research that has no application outside of Space Elevators? Or are you just assuming the worst, and bellyaching about the products of your imagination?
Re:Successful Test?!? (Score:3, Insightful)
Nor is it the sort of discoveries we've seen in the materials side of the equation; fibers measured in millimeters. That's not a prototype, it's just basic research. Interesting basic research, worthy basic research, and good basic research to be sure, but it's not a demonstration of practicality by any stretch of the imagination.
When someone builds a small footbridge out of these things, I'll be interested. When you can scale that to a mile-long suspension bridge that supports two lanes of traffic in each direction, I'll be optimistic.
Can't say I agree. The hard part of the problem is the materials science... and here we have in labs macroscopic fibers of a suitable material. Is it long enough? No. Is it strong enough? No. But neither were the first cables of drawn steel strong enough to do what we use them for today in applications you would consider uterly common. Like suspension briges.
The material science, the hard part of the problem as you say, is progressing fantastically. Not "operational space elevator in twenty years" fantastically, but we've made orders of magnitude improvements in strength/weight that were unfathomable twenty years before. I'd say there's every reason in the world to be optimistic, until further research shows that we are in fact heading down an impossible path.
At the point at which we've built a suspension bridge out of carbon nano-fibres, you're way past the point where anyone with any sense would be optimistic. Assuming we've solved the other problems that now seem inconsequential, like climbing robots, then building the elevator would simply be a matter of dedication of resources. Much like building the first steel suspension bridge after the development of sufficiently good steel wire.
Now Is Never (Score:2, Insightful)
When we better understand genetics and what it takes to build self-sustaining repair subsystems, we will be able to build sustainable structures that exist in our atmosphere and beyond it. It's the same with our space stations and our space vehicles. They have an expiration date that is inevitable based on chance encounter with destructive environmental agents. The Earth is a self repairing structure that has been alive for billions of years. The Moon has been up there quite a while, too, and it's connected to the Earth by gravity. If we find a way to ride that link, we may well have the elevator we need already there.
But as far as coping with environmental damage, we have the same issues on earth with just about every object we create. It wears out and it wears out pretty rapidly. Even we wear out, though our repair systems allow us to do quite a few amazing things over a long period of time before we die. If we really want renewable structures, then they will have to have a "nervous system" of sorts that perceives structural damage and a "repair system" of sorts that can restore damaged areas to original state.
This is not impossible. Our bodies are proof that it is possible. We just don't know how to do it yet. Likely because it's never been a big enough priority. When we start to use up all the easily accessible non-renewable material resources on the planet, we may start making breakthroughs in this area of recycling and repairing rather than discarding (a la "cars no longer go to the junkyard because it's too costly to waste all those materials, so instead we build cars that can repair themselves and last 3 times longer (at which point we'll probably call them "horses").
Never isn't quite now, but it's not far.
Another way? (Score:3, Insightful)
Re:Now Is Never (Score:4, Insightful)
Bridging the gap between computer science, robotics, molecular genetics, and biochemistry seems like a bizarre and convoluted route to addressing the problems stated in the article.
First, modeling engineered devices on real world objects, even features of living objects, is not a new concept. Second, we're talking a fairly simple system, a big long ribbon, not a complicated self-regulating autonomous device. Nor is there any reason to make something that would need to be as fault tolerant and robust as possible more complex than it needs to be. So, self-reparing system may sound sexy, but if a simpler mechanism can be devised than inventing an entirely new class of devices and methodologies to fix the problem, that is rightly the domain of material sciences, i fail to see why we'd want to start spouting off ungrounded hype about inter-disciplinary science that at the moment is... to be kind, speculative.
Bah - perfect crystals are the *lower* limit... (Score:2, Insightful)
Nearly perfect crystals (what TFA is whining about) have been known to fail catastrophically, and quickly for as long as people have associated the word 'brittle' with 'crystal'.
Now, many *amorpheous* covalent structures (eg: window glass - although it is often weak) can have both extreme strength - as strong as a perfect crystal, perfectly aligned - and extreme thoughness (robustness in the face of damage).
Extremely complicated - although not amorpheous, materials can also be as strong as their constituent carbon bonds, and can (not usually at the same time in nature though) be even more forgiving of damage. Most woods (particularly the softwoods we are surounded by) for example, will react to penetrations (like nails) by bending around the damage, and with the massive crosslinking, the column of fibres damaged is only weakened for a short distance near the damage.
This means that we only can be sure that the *largest* hole in the material will cause significant weakening as the others should not be right next to it and thus would be 'second and subsequent' links in an analagous chain, and thus of much lesser consequence. Amusingly, a hole wouldn't neccessarily even cause weakening proportionally to its fraction of the cross-sectional area of the material.
TFAuthor noticed that a single carbon tube is weakened after losing a Carbon, way weakened by two, and toast shortly after... then used his own 'secret recipe math' to 'prove' that big piles of nanotubes would be statistically likely to fail.
Without defining the *exact* nature of the cross-linking reinforcing the tubes you can make almost no statements about how forgiving the material is going to be of damage. The researchers quoted in TFA who are working with actual buckytubes, trying to actually build something, are correct to shrug off the TFA as being both theoretical, and wrong. They have more pressing problems (like getting past the 1 GPa point) than worrying about the theoretical maximal properties of layouts of tubes that they were not even *considered* using.
And, yes, it is freaking idiotic to say something technological is impossible, when the physics do not rule it out. It is merely *daft* to assume that something prohibited by current physics is impossible - but that is not the case here.
Low-earth orbit -- monkey physics fails again. (Score:3, Insightful)
This isn't science, it's an ill-conceived editorial. Ignore this article and get back to work, my space monkey minions! Soon space will be ours!
Re:Never? (Score:2, Insightful)
Depends on how you define "between". In some geometries, and according to some views on infinity, five is indeed between three and four.
Re:Never? (Score:3, Insightful)
It's a foolish person ... (Score:4, Insightful)
So far as I can see, all the objections mean is that a space elevator cannot be built with the technologies we currently have -- and all of them seem to be of an engineering bent, as opposed to some fundamental theoretical problem. Engineering problems tend to get solved over the long haul.
And even if the problems presented do turn out to be too difficult to construct an Earth-based space elevator, the technology could still be used on the Moon, which presents a much smaller challenge. I suspect that we already have the capabilities required to construct a lunar space elevator -- all that we lack is a permanent lunar base.
Re:Never? (Score:5, Insightful)
Sure it may take 1,000's, 1,000,000's, or perhaps even 1,000,000,000's of years.
And I'm of the opinion that unless there's some mass societal changes, no one's going to be doing serious science in 100s of years.
Re:Never? (Score:4, Insightful)
Re:Damaged by Oxygen? (Score:3, Insightful)
Not that I have any better information...
Re:Never? (Score:3, Insightful)
Same with something like a space elevator. Perhaps it is impossible, as proposed, with current technology. Who knows what we'll come up with tomorrow.
The moral? Never, ever use the word impossible except with a not or a never positioned correctly in the sentence.
Re:Never? (Score:3, Insightful)
> sphere is indeed finite, and if there's an infinite number of them, then every possible state occurs.
Yes, but not for the reason I think you're thinking.
Just because something occurs an infinite number of times does not mean all possible states of the system must occur. There could well be states that are simply impossible to reach; for example, 0000 is a valid state for a 4-bit integer, but the bits will never reach that state if the controlling process is "add together two random integers between 1 and 3", even if you try an infinite number of times.
However---as I understand things, at least---the reason you would get all states is because of quantum effects. Basically, there's a tiny-but-finite probability of tunnelling into the state you're looking for, so---provided there is no interaction between spheres---you'll see each state represented an infinite number of times.
All that being said, though, there's little or no evidence of the universe being infinite, and no evidence at all that it makes a lick of difference one way or the other what's going on "outside" the observable universe, so it's pretty much moot at this point.
Re:Never? (Score:3, Insightful)
Re:Never? (Score:3, Insightful)
Re:Never? (Score:3, Insightful)
Wrong definition.
the operative defintion isn't "between", but what you mean by "three," "four", and "five."
If you mean these words to be what they commonly are in English -- that is, the points on the scale of whole numbers indicating (111), (1111), and (11111) things respecitvely -- then you can't get (11111) by any measure between (111) and (1111).
Or, in other words, there are some thing that we KNOW can't happen, and saying that they can is equivalent to saying that it's possible that the universe was all created yesterday. That is, it's an interesting mental exercise, but beyond that it's a waste of time.
Cumulative damage problem solved long ago (Score:3, Insightful)
Set up an elevator, and when micrometeorite damage reduces the safety margin too much, use it to haul up its replacement.
Re:unwarrented negativism (Score:4, Insightful)
The next thing is to stand your beanstalk up you need to do something like ship it to geostationary orbit with a rocket and unwrap it - so we are talking about sending a vast amount of mass up there by rocket. Obviously from this a beanstalk would only make sense in the context of it being a small piece of a larger plan that involves getting incredible amounts of mass into orbit. There's been space snakeoil companies around before (eg. the Australian spaceport company which consisted of two people - I'm assuming one to scam the money and one to answer the phone) and unbelievably optimistic beanstalk people asking for money may well exactly that, since with current designs it would have to be built of unobtainium and requires robots powered by a technology Tesla abandoned a century ago once previously unknown laws of physics became clear.
Re:Never? (Score:5, Insightful)
There is a time and a place for mathematics to be deep and mysterious. If you throw around comments like this, nobody will care when we reach one of those times.
Of course, if this was just an attempt at humor, forgive me. My anger should be directed at the moderators!
Problems to overcome (Score:3, Insightful)
There are also other avenues to space. We haven't heard much about laser powered propulsion, but there are possibilities as civilian and military researchers develop new and more powerful lasers. It would be a nice swords-into-plowshares project if we could use some of the military's new weapons for an application like this.
Also, we don't necessarily need to be able to loft huge payloads at first. If we can send up small satellites or maybe even a small manned capsule repeatably and cheaply, it would be a good start. That is after all how we started with chemical rockets, so there's nothing wrong with starting small.
Oh, bullshit (Score:3, Insightful)
Compute the resonance frequency of a device 60,000 miles long.
Which mode would you like to excite? Things don't always fail at the first resonant frequency. Many/most do, which makes the others that much more spectacular (and unexpected, I might add).
What danger to airplanes? Are you envisioning something that's going to randomly and rapidly maraud across the surface of the Earth or something?
Of course not. Not until it snaps due to a flaw or an unforseen event. I'm not saying that there will be a plane flying around when the string goes pop (note, I said "when" not "if"). That chance is very, very remote - you know, like large-comet-impacting-Jupiter remote.
On the flip side of that argument, luckily, nobody has any reason to intentionally try and fly an airplane into such a structure. That's why planes never fly into buildi... oh, right.
For instance, what you probably think happens if there is a cut near the ground is the exact opposite of what happens, because your intuition is not set up for these kinds of problems.
So what happens when the fiber is severed in low earth orbit? There's a lot of money tied up in communications satellites, and the companies who own them would be pretty pissed off to lose them. Not to mention the public outcry if the loss of a major bird or two interupts their viewing of the World Series.
Even more interesting is what you're going to do with all the low earth orbit satellites. There are lots of them out there, and they'll be travelling at up to 7km/s relative the fiber (perpendicular to the strand axis, esp. for polar orbits). Not all of them are active (LAGEOS and similar passive reflectors come to mind), and will no be able to correct their orbits. No matter how thin the strand, eventually their paths will cross.
Your intuition is worthless. Nothing personal; mine is too. Having studied the topics involved I can say I understand some of this stuff intellectually, but I can't say I understand it in my gut. But I do know not to trust my gut in this domain.
(For what it's worth, similar concerns apply w.r.t. nanotechnology. Your intuition about how things work does not do very well at that scale. Our brains function at the in-between scale we all live and work in, and does not do well outside of that domain.)
Yes, when you deal with orbital dynamics, the x, y, and z we deal with on the ground doesn't apply anymore. In addition to the article, there is one other thing that will keep the space elevator from happening in the lifetime of my children: safety. I've mentioned it above, but this sort of thing is going to have to be safe. No, I take that back, it's going to have to have a proven failure rate of zero. Too many things can go wrong, and the publics tolerance for failure is so thin - well, it makes a carbon nanotube thickness seem large. I think the political hurdles are larger than the technological ones - and that's saying quite a lot.
Re:Never? (Score:3, Insightful)
Actually, do I really need to keep going here? I seriously hope you were kidding.
Re:Oh, bullshit (Score:3, Insightful)