Guest essay by Eric Worrall
South China Morning Post has published a claim that Chinese researchers have successfully synthesised a sample of a carbon nanotube material so strong it could be used to construct the tether cable of a space elevator.
China has strongest fibre that can haul 160 elephants – and a space elevator?
Scientists say just 1 cubic centimetre of the carbon nanotube material won’t break under the weight of more than 800 tonnes
Tsinghua University researchers are trying to get the fibre into mass production for use in military or other areas
PUBLISHED : Friday, 26 October, 2018, 12:03am
Stephen ChenA research team from Tsinghua University in Beijing has developed a fibre they say is so strong it could even be used to build an elevator to space.
They say just 1 cubic centimetre of the fibre – made from carbon nanotube – would not break under the weight of 160 elephants, or more than 800 tonnes. And that tiny piece of cable would weigh just 1.6 grams.
“This is a breakthrough,” said Wang Changqing, a scientist at a key space elevator research centre at Northwestern Polytechnical University in Xian who was not involved in the Tsinghua study.
The Chinese team has developed a new “ultralong” fibre from carbon nanotube that they say is stronger than anything seen before, patenting the technology and publishing part of their research in the journal Nature Nanotechnology earlier this year.
“It is evident that the tensile strength of carbon nanotube bundles is at least 9 to 45 times that of other materials,” the team said in the paper.
They said the material would be “in great demand in many high-end fields such as sports equipment, ballistic armour, aeronautics, astronautics and even space elevators”.
…
Those cables would need to have tensile strength – to withstand stretching – of no less than 7 gigapascals, according to Nasa. In fact, the US space agency launched a global competition in 2005 to develop such a material, with a US$2 million prize attached. No one claimed the prize.
Now, the Tsinghua team, led by Wei Fei, a professor with the Department of Chemical Engineering, says their latest carbon nanotube fibre has tensile strength of 80 gigapascals.
…
If this claim is verified by other researchers, the properties of this new material are straight out of science fiction.
Space elevators are the ultimate cheap space launch technology. Instead of blasting into space using a rocket, space elevators allow launch vehicles to literally climb to orbit along a long cable, using electric power supplied via the cable.
The way space elevators work, a satellite is placed in a geosynchronous orbit, and a long cable is dangled down to Earth, where it is tethered to a ground station. Geosynchronous satellites orbit the Earth once every 24 hours, so from the point of view of someone on Earth they appear to permanently hang in the same place in the sky, providing the perfect orbital tether to the top of a very long elevator cable. TV satellites are also placed in geostationary orbits, so you can point your satellite dish at the transmitter, and never have to adjust it again.
The catch is the tether cable has to support its own weight for at least 22,000 miles, so the cable material must be immensely strong and extremely light. The new Chinese nanotube material may satisfy both of these requirements.
Space elevators could be used to construct solar power satellites for an affordable price.
The new material might even make electric cars practical – the Post claims it could potentially be used to construct a flywheel battery for an electric automobile capable of holding 10,000 miles worth of electric charge.
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Why do they want to put 160 elephants into space?
Dunno, but I’m not standing under them!
More importantly, is that an African elephant or an Indian elephant?
Or just one of those little Chinese elephants from down South?
I’m thinking its one of those white elephants we hear so much about….
But why don’t they stay in the kitchen ??? 😀
Here’s a pink one, though it drinks milk rather than ethanol:
http://news.bbc.co.uk/2/hi/science/nature/7951331.stm
We had a bar down the street called the “Pink Elephant”
old construction worker,
The famous Pink Elephant Pub is in Phnom Penh, Cambodia.
There are a lot of Pink Elephant restaurants and bars scattered around the globe.
The one in Boca Grande, FL rates 4.5 out 5.0 in 543 reviews on Trip Advisor.
I guess “is a lot” would be grammatical.
how many swallows could it support of the African variety?
That would depend on airspeed velocity, whether it is unladen, and your favorite color, I suppose, Eric. Of course, they are non-migratory, so it would only work over Africa.
At five tonnes each, it would have to be a load of bull elephant, but could be either African or Asian.
Or if it was all the stuff from the Escathological Cargo Cult of the CAGW, just a load of bull.
Then again, if was real elephants, I would not want to be underneath when they release their payload.
So it can be elephants all the way down.
yup modeled elephants allllllllll the wayyyyyyy down
LOL!! This page is full of wit.
A space ‘ elephant ‘ may have exterminated dinosaurs
More on the Chicxulub Crater – The impact that changed life on Earth
https://www.bbc.com/news/science-environment-45986449
Thanks!
A bad day on planet Earth.
Anti-asteroid defense should be a mission for the proposed Space Force, if it ever actually comes to be.
Just fling 160 elephants at the offending ‘roid
@ur momisugly John,
There are 160 elephants in the room with regards to global warming and it’s difficult to NOT see them. Hide them in outer space along with the missing heat for CYA!
Maybe someone can help me out here. I vaguely remember a shuttle experiment where they floated a metal ball on a tether. As I remember the electric potential shorted out the experiment. If you tether 22000 miles do you end up with a permanent lighting bolt?
taz1999
I wondered the same thing. I was involved in the Launch of STS-75 which deployed the Italian Tethered Satellite System (TSS). The experiment deployed a 12 mile cable which produced 3500-5000V. The experiment failed when the insulation broke down due to a manufacturing defect and caused the cable to part from the Orbiter.
That being said the TSS deployed an electrically conductive cable, not sure if carbon nano fibers fall into that category.
The electric potential was from the conductive tether cutting across the Earth’s magnetic field at ~8km/s.
“Why do they want to put 160 elephants into space?”
because that’s 160 elephants that are protected from ivory wild theft.
And they could possibly die there and good reason to gather the ivory.
And they could possibly die and good reason to collect the ivory legally.
Look up newest computer games “grand theft ivory”.
Save biodiversity! Stop penguin tossing!
https://www.google.at/search?q=computer+game+penguin+throwing&oq=computer+game+penguin+throwing&aqs=chrome..69i57j33.28639j1j7&client=ms-android-samsung&sourceid=chrome-mobile&ie=UTF-8#scso=_LsjVW5GeK-irrgSN4KGIAQ6:0
If that flywheel battery explodes, I would not want to be anywhere near it.
The skyhook is a neat idea, if one actually has the materials and will to do it.
Cornering with that thing on board might be fun, I guess it might have substantial angular momentum.
That all depends on the orientation of the flywheel and whether it employs counter rotation to negate the precession forces. Bicycles and motorcycles use these forces to their advantage to corner (and necessarily “roll to yaw”).
Flywheels are used to stabilize the orientation of many satellites including the ISS (International Space Station). Eventually these flywheels become “saturated” and lose their ability to function.
But, as you mention all tempts to create filament wound flywheels has not ended well for any of the attempts. Yet we cannot nor should not stop trying.
Rocketscientist – usually before flywheel saturation, we do momentum dumps – for the last few decades at least.
Yeah, I didn’t consider the gyroscopic effects, just the power density, which is an issue with very high density batteries as well. A failure would make it a rather effective bomb.
Gimbal!
Yeah. You think it was hard to turn that little gyroscope you started spinning with a foot of string? How about one with the energy of 500 gallons of gasoline!
Most of these “possible uses” have been so poorly thought out. This sounds more like hype than serious breakthrough.
I immediately had the same idea.
Presumably its inside a nanotube case…
This could be the biggest news story of the decade. Not biggest science story – biggest story.
If they have really achieved this then the sky’s the limit. No wait, the sky’s just a starting point.
And all the Earthbound applications are potentially wonderful too.
Could make a really good cheese slicer as well.
Or an invisible nanofilament knife-thread!
Dark, I know.
Someone throws two balls at you, one on each side. Suddenly you’re in two halves…WTF?
Or approaches you, holding a handle with a weight circling around his head…what harm could that puny thing possibly do?
..or the new Ronco bird slicer
Or, indeed, a splendid garrote.
. . . the military will be real interested
The theoretical strength of carbon – carbon bonds does not allow for a space elevator that reaches the Earth’s surface.
It would work fine on the moon.
And of course there is the little problem of air friction.
“And of course there is the little problem of air friction.”
You’d think so, but mostly no. The top end of the elevator is a satellite traveling at exactly the rotation speed of the Earth. i.e. it’s geostationary. It’s rotating in the Earth’s equatorial plane and the bottom of the cable is on the equator “under” the terminal. The cable isn’t actually holding the satellite in place. There’s no air friction other than “normal” winds.
BTW, I’m far from convinced that a space elevator will actually stay working very long when one considers all the forces acting on the Earth and the terminal satellite. For example the direction of the gravitational attraction of the moon will vary in a monthly fashion. That tends to move the terminal around relative to the ground station. Except that cable presumably constrains the terminal’s motion in some directions, but not others. Which seems to me to net out to a “downward” force that isn’t experienced by normal geostationary satellites. But I’m a lousy physicist, so I’m probably wrong.
Or, let’s just consider the elevator gliding up the nanocarbon string to the satellite. Somewhere along the way it would have to accrue the matching lateral satellite velocity (which is almost escape velocity, but not quite). This can be imparted only by bowing the string, which pulls down on the target satellite! Not a good thing! Realistically, the string can only provide radial momentum; angular momentum would still have to be provided by rockets.
Good thought!
As this could be a good start, more and more feasibility studies should be proved to ensure safety from the start up to the end of each journey.
Does the tether have to be the same ‘diameter’ all the way up to 22,000 miles? I would expect that miles 1 through 10 (From the Earth) would have different strength requirements compared to miles 20,000 through 20,010. Segments needing greater tensile strength could just be ‘doubled up.’
Um…that’s not how stress (load) is calculated. It is based upon cross-sectional area NOT volume. Mass is calculated by volume.
Stress carrying capability is measured in square cm. One cubic cm could create fiber extraordinarily long but also extraordinarily thin, or it could create a fiber infinitely short and infinitely large in diameter.
This is meaningless drivel.
Agreed. There is a huge difference between static and dynamic strength/loading. I’ll likely be long dead before this amounts to anything practical with regards to space elevators and much else.
They seem to have fallen prey to not understanding the “Square / Cubed Law of Materials”.
The load carrying capability of a material (strength) increases with it cross-sectional area while the mass (hence weight if in a gravitational field or subject to force) increase with cube of its dimensions. Therefore the mass increases much faster than the strength. Eventuality any structure will grow to a size that cannot support its own weight under load. The ratio of this depends upon the loading forces (here we call it gravity).
Stronger “strength to weight” materials have been developed throughout history, wood, stone, copper, bronze, iron, steel, composite).
I am dubious of these claims. And the inaccurate reporting enforces my skepticism.
The principle is flawed. While the geostationary satellite keeps a fixed position above equator, it still rotates with the Earth once every 24 hours – on a much larger radius. The additional orbital velocity required is about 3 km/s (almost 2 miles per second). You have to accelerate any load ascending on a space elevator to that speed. Proponents are very discrete about this.
George – they use perpetual motion machines to accelerate the load. The art students who designed this have thought of everything.
I disagree, there is no flaw. Nobody has said it would not take energy to haul things into orbit. But unlike a rocket, it does not have to carry it’s energy source with it. A lot of the fuel used b a rocket is burned up lifting that fuel the first few thousand feet. On a space elevator, the cab would be powered by electricity which would be provided by power stations either end and carried through the cable/ribbon. This makes the elevator much more efficient in terms of energy used per pound of payload delivered to orbit. It would be slower than a rocket, of course, probably taking a day to make the trip one way, but for most purposes, that would be acceptable.
Something that uses an motor to “crawl” up a fiber is going to be more efficient than a rocket motor.
I’m suspicious of the claims of sending power along the cable. You need two conductors to send electrical power.
Yes, the rocket propulsion is extraordinarily wasteful. This proposal gets the load up much more efficiently – unfortunately, it will also lean sideways.
If I was going to use something to haul me 22,000 miles above the earth I would damned sure want more than one cable doing the lifting. More than one cable gives you more than one power conductor so there is your circuit for transmitting power to the lift car.
Second thing is, a conductor being waved in a magnetic field will generate a potential difference from one end to the other. This thing could be used to generate power.
Third thing, how do you tow 22,000 miles of cable into space?
Finally, what happens if this thing breaks? The outer end flies into space while the other half falls back to earth in one humonguss pile (however you spell humonguss). I would not like to be underneath.
Then there is the problem of voltage drop. I don’t know what the impedance is along the wire, but even at near perfect conductivity, twenty-two thousand miles is a fairly long run.
The concepts that won lifter designs contests use lasers.
competition lifts were done years ago.
Eric, it wouldn’t fall into a pile. It would fall to the east and quickly wrap around the earth until it burned up in air resistance.
Kim Stanley Robinson described a falling space elevator in the later parts of Red Mars.
Curios G. The force would need to be perpendicular to the elevator correct? And if so how much energy is needed in that direction relative to a rocket? Just curious 😉
Stephen Rasey
October 26, 2018 at 8:22 pm
Eric, it wouldn’t fall into a pile. It would fall to the east and quickly wrap around the earth until it burned up in air resistance.
Kim Stanley Robinson described a falling space elevator in the later parts of Red Mars.
and Im sure another older book I read had a space elevator crashing and wrapping around the equatorial areas doing massive damage.
I refound n read it about 4 yrs ago and damned if I remember who wrote it;-( sorry
Steven Mosher
October 26, 2018 at 7:08 pm
“The concepts that won lifter designs contests use lasers.
competition lifts were done years ago.”
Yes, I remember watching videos on that. So, the cable itself does NOT require separate electrical power nor electrical transmission properties. All that you need is a way to hit the elevator car’s target with your laser (or equivalent) and a way to focus on the target. The car itself is a kind of electric vehicle powered by the laser ‘shot’ into it.
That is definitely safer with regards to speed and friction, but time of travel will be high.
Other treatments of this idea have suggested that descending cars would use regenerative breaking, and that power would be shunted over to ascending cars, cutting down the amount needed.
Yes I had wondered about this and also just how much correction will need to made to orbital decay that results from winching loads into orbit.
They could use hundreds of elevators going up one cable and down a second cable. The elevators going up take water, air, food and chinese manufactured goods. The ones coming down the second cable bring trash, sewage and broken chinese manufactured goods.
The principle is NOT flawed. But yes, the actual, final position of the satellite would probably need continual adjustment – but so what?
Yes, you end up needing to add tangential velocity, but if it works, you still don’t need to carry quite as much reaction mass as if you had to leave from Earth at sea-level on thrust alone.
Remember, the surface from where you left is already moving East at about 300m/s.
You could go, say, halfway up the rope, send back your empties, get them re-filled on the ground, then sent back to you, having themselves expelled enough reaction mass for the tangent velocity required. This is still better than using up 90% of your rocket’s mass to get to medium-height orbit.
For the first 200km, you only need to accelerate tangentially by about 15m/s.
I’m still a little sceptical about the material, though. As Rocketscientist mentions, the load per cross-sectional area is what you want. The load per unit volume is like specifying temperature in acres.
What’s wrong with specifying temperature in acres? “Climate scientists” have been doing it for years.
Or energy in C?
I think they meant a 1 cm cube, translation/journalist error.
That gives a sq cm as the cross-section and assuming claimed tensile strength of 80 gigapascals, that works out to 815 tonnes in earths gravity.
Remember it is “reporters” writing this article. They are notoriously bad at science.
I read about this 10 years ago when China formed a consortium of nations, excluding the US, to develop a surveillance satellite system that would blanket the earth, and that such a system would knock out all other satellites in space. The original development of the materials for this elevator were developed by White and Chinese American students of astro-science in an American university. A prototype was demonstrated on video. Yes, the Communist China imperialists are very serious about this.
Ahh, the “Fountains of Paradise”
thank you:-) thats the one!!!
WHERE IS MY COMMENT, AGAIN???
▲ It’s above here ! ▲
(:-))
Sorry marlene, couldn’t resist
LOL!
marlene ==> ALL comments undergo moderation here. Some just the auto-magical programmatic moderation (scanning for forbidden words — obscenities, threats, etc) and others, also programmatically are shifted to human moderation based on a set of rules (of which I do not know the details). Sometimes a bit of patience is called for.
You could go to the Tips page and ask the Mods to explain it to you.
Thanks.
If this is a ballistic armor game-changer, there won’t be any independent verification outside of China. That tech door only swings one-way.
If they actually build it you can be sure it’ll be replicated elsewhere. The design is published and even if they tried to keep it secret, others would figure it out. Just knowing that it’s possible with current carbon nanotube tech is a major clue.
Remember this is the same country that “extinguished” a coal mine fire. If you want proof just drive to the mine, it will be the one with the coal smoke coming out.
Ballistic armour was my first thought as a practical and immediate use-case. Space elevators, not so much. I’m thinking of the testers starting with small-calibre weapons and after every increment going, in a deadpan voice, “We’re going to need a bigger gun.”
Space elevators are an interesting concept and have been considered for decades, however it is not necessarily clear on how they would be constructed.
As I have mentioned before; “Any scientist can calculate a number, but it takes an engineer to demonstrate just how big of a shit load that really is…or isn’t.” Or, “Rocket science is easy, but rocket engineering is a bitch!”
Such a tethers would necessarily need to be lowered from space down to earth (try as you’d like its still very hard to “push rope”), and as they were lowered would be subject to all the gravitational loads and orbital forces as well as atmospheric forces. The mass of getting enough cable into orbit is a huge challenge, and such a cable would have to grow in diameter as it was lowered due to the increasing mass of the suspended cable, lest the weight of the cable would cause it to break itself.
Now what exactly would all this mass and drag do the orbiting elevator reel? Well, simply put: not very good things.
The logical method would be to manufacture the cable in orbit rather than try to pre-assemble it on the ground. Not sure where all the raw material would come from, though.
nanobots on an asteroid making the cable
That was my first thought too….and the cable would create drag
“a satellite is placed in a geosynchronous orbit, and a long cable is dangled down to Earth”
Conservation of angular moment says that any such cable hoisting stuff into orbit would be trailing back against the direction of rotation.
“Now what exactly would all this mass and drag do the orbiting elevator reel? Well, simply put: not very good things.”
Can you say deorbit?
I guess if you had large enough station keeping rockets and an unlimited amount of fuel on the geosynchronous platform holding the tether, then theoretically the platform could remain stationary with respect to the earth. However, without such systems to counteract the radial force downwards, the mass of the 22,236 mile long tether would deorbit the satellite.
Simple physics…
Most employ a counterweight you dont hang it from a satellite.
And, unless this fiber is rigid like a pole, then whatever is sent up it will be pulling on the “rope”.
People have mentioned electric power being supplied to the load but unless that power can be converted into thrust, then you have, in effect, someone trying to climb a rope that’s not tied off.
But I’m just a layman. Maybe I’m missing something (or a lot things).
Thrust is provided through “wheels” attached to the carbon ribbon powered by an electric motor. The “rope” is not floating but attached to a counter weight. Think swinging a rope with a weight attached while doing that could an ant climb the rope? But you are fundamentally correct for every action there is an equal and opposite reaction. So does this slow the earth’s rotation? To late for me to contemplate that.
But what is the counterweight?
I suppose centrifugal would provide some but it seems the anchor point in space would need to have some way to provide thrust itself or the more loads sent up the lower it would be pulled.
Perhaps each load would need to include fuel for the thrusters?
In a basic space elevator the anchor point on the ground provides the lateral thrust needed to accelerate the lifted load. This factor, along with how far you can allow the tether to lean, is a limit on how fast mass can be lifted. Or a current can be run along the tether to push against Earth’s magnetic field.
Not only drag, but considerable electrical potential.
If I remember elementary electro-mechanics properly moving a conductor through a magnetic field is what we describe as a “Generator”.
If such a device is built it would generate significant electricity.
The mass of the ‘elevator cars’ would also whip them out to the end with extraordinary force. We’ll need to harness this force to ‘pull them back down again’. I suspect the elevator will would much like a funicular.
just need a ground rod every mile or so… you scientists are so negative.
It’s orbiting at the same rate that the earth is spinning, so it isn’t moving though an electric field.
The cable would be moving through the solar magnetic field even if it is stationary with respect to the Earth.
If moving through the solar magnetic field was a big issue, then we could use the electric grid to capture energy from the same source.
We don’t. The reason why is the solar field is too weak.
I’m not saying the potential electrical current between the earth and the sky would light your cigar, but I hear it fried a Russian who tried to duplicate Franklin’s experiment.
As a reading assignment, I would recommend two novels:
_The Fountains of Paradise_ by Arthur C Clarke, and _The Web Between the Worlds_ by Charles Sheffield
Both depict in orbit assembly of the beanstalk, with Clarke’s approach bootstrapping the load carrying beanstalk on a preliminary scaffold. Sheffield posits some fancy orbital exercises to fly the completed stalk in.
Both incorporate a surface anchor & a rather large ‘counterweight’ mass just beyond synchronous orbit, keeping the beanstalk under tension.
Kim Stanley Robinson used a space elevator in Red Mars. Find a Carbonaceous asteroid. Move it into Mars sync orbit. Then have robots spin the cable upwards and downwards. The upward section becomes an elevator to a launching sling for trans-earth injection. The downward part becomes the elevator cable. When the cable is broken at the sync station, the downward part falls around Mars to the east at increasingly rapid rates like a giant whip.
Rocket – just a nit, but as you hang the cable from the geostationary satellite, you have to build counter mass going higher. Otherwise, center of mass falls below geostationary orbit, and the satellite no longer remains in “one place” relative to Earth.
Quotes are used because the satellite does move in a figure eight. Small enough that a ground antenna doesn’t have to re-orient itself.
Not, a nit at all. I could go into quite a dissertation regarding the feasibility of these concepts and the technical hurdles required to be overcome, but as I am loath to annoy the audience ( “I could tell you what I do, but then I would have to wake you up again”) I elided by a few minor points such as the enormous anchoring loads to keep this attached to earth.
“I could tell you what I do, but then I would have to wake you up again”.
That’s much better than “If I told you what I do, then I would have to kill you”. 😉
Brilliant comment…please do wake me up.
Geostationary orbit altitude is 35,786 km, so that 1 cm^2 cable would weigh 5,726 tonnes. Actually, it has to extend further than 35,786 km, because it’s the elevator’s center of mass that has to be kept at geostationary altitude. And I’m sure you would need multiple strands to make it work, though let’s suppose it just took one.
Launching from earth would require roughly 1,400 expendable Falcon 9s, or 2,100 Falcon 9s with reused first stages. I’m sure they would be able to get down to the $40 million launch price with reuse, and that flight rate, so the launch cost would be around $82 billion. We’ve spent more than that on ISS; heck, the NASA IG just reported that we’ll spend $8.9 billion on the Space Launch System by 2021, and it will probably never fly! So the cost does not seem prohibitive, at least for one strand.
SpaceX can currently produce 40 Falcon 9s per year, so the time to build the first strand would be about 53 years, and that’s only 2.5 times the time it will have taken to build and launch the James Webb Space Telescope (if it actually launches in 2021, which I’ll believe when pigs fly). So even the time is not really unreasonable.
I wonder about the utility of using it for space solar power. There are two major problems, one practical and one environmental. As a practical matter, how does one deliver electric power from South America and Sub-Saharan Africa to places which consume the most energy? Then there’s a question for the climate science “community” to ponder: What happens to global temperature when we start taking clean, sustainable sunlight that would never have hit the earth in the first place, and pump it down a wire for it to be instantly dissipated as heat at the earth’s surface?
Playing devil’s advocate for the CAGW acolytes: Don’t re-orient the panels towards the sun, have them constantly facing away from the Earth. That way it only blocks light that would have reached the Earth, and efficiency losses of the panels and transmission mean that there will be a net cooling effect. ‘Free’ electricity and less global warming.
Does no one even watch scifi anymore? Assuming you arrive at a geo-orbiting satellite with s spool of nanostuff, each element of the cable is perfectly happy to stay there! As you unwind the cable it is not going to “drop towards earth” unless you pull it! Reducing its lateral velocity along the way! I’ll leave it to some industrious mathematician to calculate the path described by a string pulled by one end in the gravity field, I just know it won’t be straight down.
First part of the tether has to be pulled. Beyond that gravity gradient will do the pulling for you. You will need something to dampen rotation, but that can be done by passive 1960’s tech.
The “weight” of a theoretical space elevator cable would be less than you might think, since gravity decreases as the square of the distance from Earth. The effective force of gravity on a geostationary satellite is by definition zero, due to the orbital dynamics. Still, a space elevator would require an immensely strong cable.
The weight of the cable increases as it is nears the Earth so too will the load upon it and therefor the stresses incurred. Until to reaches its full extent it will assume a catenary like shape and be whipping around at its earthly end with rather sever magnitudes, like a tail in the wind.
Ah, yes an interesting proposal, but who will ‘put the bell onto the cat’?
Can’t you just start with a very very thin cable and use it to pull up a thicker one and so on..
The very thin cable is still beyond current materials capability.
As I understand things, the issue has not been, are carbon nanotubes strong enough. The issue has been making them long enough with sufficient quality control to make a space elevator.
The entire concept seems to be ignoring the “Square/Cubed Law of Materials”
A material’s strength is based upon its cross-sectional area load carrying properties, hence dimensions squared.
The mass or weight and hence implied load due to forces is a function of the cube of its dimensions.
Therefore the mass (and weight under force) increases much faster than the strength.
All materials will experience a point wherein structures build from them will collapse under their own weight.
Engineering can design increase margins for these structures, but eventually the ratio will be reached and the size would require an infinite support base.
This is a concern only when scaling up from humans to, say, elephants. For a rope, the mass will increase linearly with length, not in a cube/square fashion. Therefore, the only question is do you run out of rope strength before you get to where you’re going? Per the article, NASA says you need 7 gigapascals of yield strength to git ‘er done. They’ve got 80 gigapascals. What exactly is your objection again?
For beanstalk design, this is called the ‘taper factor’ – how much thicker the stalk needs to be, where it is caring the maximum tension [typically at synchronous altitude] tan where the stress is at minimum [typically at the ground anchor]. The overall beanstalk center of mass will need to be in geosynchronous / geostationary orbit, so some large ‘counterweight’ mass is needed above geosynchronous height.
yes, the designs have counterweights
Ahh but don’t forget buoyancy effects. If you make the material light enough it will float in air!
The same thing the oil industry uses in drilling very deep wells – If you put a long enough drill string together eventually it will pull apart of its own weight. SO, they put heavy drill ‘mud’ in the hole and the steel drill pipe ‘floats’ in the dense liquid. Lo-o-ong drill strings and deep holes.
I put this right up there with their concept of LEO (low Earth Orbit) geostationary reflective “moons”.
Seems they need to revisit elementary orbital mechanics.
Their next announcement will be that they intend to explore the Sun, but to avoid burning up they intend to visit during the night.
An Earth-based space elevator would consist of a cable with one end attached to the surface near the equator and the other end in space beyond geostationary orbit (35,786 km altitude).
This is from Wiki,
not surprising it doesn’t give the calculation for the orbit of the counter weight…
http://www.liftport.com/the-earth-elevator.html
Cool. That’s all. Waiting for confirmation and a demonstration. Plus, I’m wondering what the costs would be to have terrestrial production levels – never mind space-elevator-levels.
A geostationary satellite is not good enough; the satellite has to be well beyond geostationary altitude so that the cable applies its own weight to keep it orbiting at geostationary angular speeds. You have to start at geostationary altitude, and as you reel out the cable the satellite altitude must slowly increase to compensate for the increasing perceived weight of the cable. You need to slow down the leading edge of the cable as it approaches the earth to counteract the high orbital velocity, and keeping the whole stand straight, and free of oscillations. And heaven help whatever is on the ground should the strand break at any time.
Since it is past geostationary orbit, the tether would need to be strong enough to hold the satellite in orbit. So, when a piece of space junk hits and snaps the cable, the geostationary satellite, and whoever is on it, but be sling-shot out into space ….never to be seen again.
Yes, but it would make for a impressive display while it lasted.
To borrow from General Pierre Bosquet after having witnessed the charge of the Light Brigade: –
C’est magnifique, mais c’est ne pas la space elevator!
It may be important, but a space-elevator is problematic. What happens if it fails? It crashes uncontrollably at re-entry speed across vast tracks of land….
If true, this would actually be more important for construction of earth-bound items.
depends where it breaks
http://gassend.net/spaceelevator/breaks/
Very interesting, Steve. The animations suggest that if failure were immanent or had just occurred, the correct course of action might be to blow up the anchorage.
Thanks, Moss, that’s very interesting — link saved. Of course even if it broke off into space, satellites or anything else would be at risk. Now that would REALLY be some space junk!
If the tether fails, everything flies off into space.
If the tether fails, everything lower than the break will fall to a lower orbit, therefore shorter orbital period. it moves eastward, pulling itself down further. It is a cascading failure that will bring the tether down as a whip.
Yes, Steve Mosher posted just about 10 minutes after you did with a link to very interesting simulations.
If verified this technology would be quite transformational. Batteries for electric cars would be nice but having load levelling storage technology for the wider grid would significantly reduce costs to all users. Throw in efficient solar energy from space and the future looks very good indeed. Fossil fuels have dominated for thousands of years primarily because of energy storage density but the conversion efficiencies are fairly low unless you just need to heat something up. Switching our gadget crazy society to fly wheel tech would allow very high in/out storage efficiency and in combination with electric motors you get a step change in efficiency for the entire economy. Science!
There are *plenty* of really valuable applications for such a material here on the surface. The planetary risks from failure of a space elevator cable are not insignificant, at least for those living near the equator. I don’t think Lloyd’s has insurance policies for that.
At over 22,000 miles long, a cable whipping about at reentry speeds has the potential to damage a lot more than just equatorial regions.
I imagine that being carbon, the tether will burn quite nicely during reentry. Should be quite spectacular. It’s entirely possible that being both flammable and low mass, little or no tether material would make it to the surface and that which did would not be much of a threat to anything.
(Still, though, I think I’d prefer to watch all that through a TV monitor … from a solidly built concrete bunker).
Yeah, this should open more applications on the ground as well. Especially for bridges connecting longer distances like between islands.
Have any of the proponents of a space elevator ever seen an elevator?
The tether is the least of it. The elevator car needs guide rails with a braking system, counter-weight and an electric winch presumably situated on the ground and therefore a double length of cable going over a pulley in the satellite. When the winch starts to lift the elevator up, the force on the pulley in the satellite will pull the satellite towards Earth so what will stop it moving?
The satellite will also be pulling on the winch as centripetal forces try to fling it away from Earth. The elevator car once it reaches the satellite will also be subject to centripetal forces, so to return it to Earth rather than gravity the winch will have to pull it back down.
The stresses and strains on the cables will be immense and that is before air currents in the atmosphere are considered or icing up of the cables, rails, elevator car which will have to be heated and supplied with air and presumably an escape capsule for when disaster strikes. The whole length of whatever structure will require anti-collision lights along its lengths to avoid aircraft blundering into it.
If it even is possible, it will not be cheap to build, maintain and operate.
My understanding is that the elevator car would climb on a “track” on the cable, not hooked to another cable. The car will need to have its own motor, solar-powered. Perhaps there will be a matching car that climbs down another track synchronously. The round trip might take many days (traveling up/down at 60 mph would take 16 days or more).
Why would it be limited to 60mph?
Unless you have some other means of adding momentum to the system (electro-dynamic tether, ion thruster, …) lateral momentum to the elevator comes from the tether being pulled to the side by the rising elevator, and the base pulling the other direction.
Why not just use Sky Hooks? They are much cheaper and available everywhere…
Yes, they’re usually in the same store aisle as the boxes of left-wall nails and boxes of right-wall nails.
…Not to mention the smoke shifters and containers of jet wash.
…and do not come back without the bucket of steam!
I’d just like to see them sort it out when it gets tangled.
Yes, and that’s inevitably going to happen. My extension cords, computer cables and garden hoses are as alive as snakes, always winding up in circular contortions and various knots of all types.
No, the Chinese have not built such a fiber. Any such fiber would be immediately applied to defense applications and would be top secret. This is a load of garbage. You know what they want though? Somebody to come help them set up a shop to produce their new wondermaterial. Then they learn new manufacturing techniques for real materials that can be applied to defense applications.
I seem to recall reading this before, should all be up and running next year:
“In as little as 15 years, Edwards says, a version that’s three feet wide and thinner than the page you are reading could be anchored to a platform 1,200 miles off the coast of Ecuador and stretch upward 62,000 miles into deep space, kept taut by the centripetal force provided by Earth’s rotation. The expensive, dangerous business of rocketing people and cargo into space would become obsolete as elevators climb the ribbon and hoist occupants to any height they fancy: low, for space tourism; geosynchronous, for communications satellites; or high, where Earth’s rotation would help fling spacecraft to the moon, Mars, or beyond. Edwards contends that a space elevator could drop payload costs to $100 a pound versus the space shuttle’s $10,000. And it would cost as little as $6 billion to build—less than half what Boston spent on the Big Dig highway project.”
http://discovermagazine.com/2004/jul/cover
I think you will find that the supposed journalist who wrote that crap didn’t give a fig about the predictions he made in his article the day after he received the cheque for it, let alone 14 years later.
The biggest lightning rod in history
http://mill-creek-systems.com/HighLift/chapter10.html
Thanks for that link. Good Mill Creek guys acknowledge that an ascending load will have to be supplied a 3km/sec orbital velocity – but don’t bother, time itself will supply it, it will ascend for a long time. But they computed that the ribbon will withstand Cat 5 hurricanes.
And, those do not occur over the equator, and less so in the middle of a continent.
“160 Elephants” would be a good name for a band.
Just sayin’.