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Space Elevator An Impossible Dream?
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."
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.)
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.
We consider ourselves masters of our universe, however there is so much yet to learn.
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.
liqbase
I thought the whole point was to be constantly rebuilding the 'string' (ie running repair bots up and down the structure or finding other repairing methods). This doesn't prove that space elevators are impossible. It just means we'd need to make a few more tech advances.
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.
OK, the summary is ridiculous here. It assumes that because one method of making a space elevator might be impossible, that it can't be done, ever in any way.
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.
Qxe4
Even if it were possible to operate such a large collection of vacuum tubes with the small power supplies available for household electrical equipment, the glass fabrication process has too many flaws to enable mass production on such a scale. It would seem that the "personal computer" will never be anything other than what it is: a fiction.
I have discovered a truly remarkable
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.
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?
I don't care if it's 90,000 hectares. That lake was not my doing.
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.
Are they seriously suggesting there is no way to make a space elevator or just not this way? I would think you get work out most of these kinds of issues by engineering better materials and by using something more redundant. If one cable isn't strong enough in the face of defects could they use say four that would each support the corner of an elevator? Could they make cables that would diagnose their own injuries and repair themselves? Every weakness is something that can be addressed and fixed.
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
... of the theoretical maximum strength of a material.
:)
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.
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!
Liberty you never use is liberty you lose.
... that treats today's limitations as if they extend into the future indefinitely.
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.
Classic. An attempt to refute a statement with an article from a user-editable non-scientific online source on a very controversial subject with questionable citations.
Not that I have any better information...
Civil engineers simply build things stronger than they need to be. The safety margin allows a structure to absorb some damage from rust, rot, barges running into it and so on while remaining robust enough not to kill anyone.
Set up an elevator, and when micrometeorite damage reduces the safety margin too much, use it to haul up its replacement.
So, we've found a few flaws in our plan. I doubt that means that this will be scrapped forever. We're always developing new materials and new ways to apply them. Perhaps someone will come up with a nanotube which has a non-reactive sheathing that can resist oxygen erosion.
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.
It's good to use your head, but not as a battering ram.
I will grant you that things of this scale do not fit the paradigm of everyday items (aka "everyone owns a washing machine"). But to dismiss some of these items is just asking for trouble.
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.
Is it just my observation, or are there way too many stupid people in the world?