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Report: Space Elevators Are Feasible
Daniel_Stuckey writes "It's the scourge of futurists everywhere: The space elevator can't seem to shake its image as something that's just ridiculous, laughed off as the stuff of sci-fi novels and overactive imaginations. But there are plenty of scientists who take the idea quite seriously, and they're trying to buck that perception. To that end, a diverse group of experts at the behest of the International Academy of Astronautics completed an impressively thorough study this month on whether building a space elevator is doable. Their resulting report, 'Space Elevators: An Assessment of the Technological Feasibility and the Way Forward,' found that, in a nutshell, such a contraption is both totally feasible and a really smart idea. And they laid out a 300-page roadmap detailing how to make it happen."
The main thing stopping us is funding and lack of materials of the right tensile strength.
For anyone interested in the concept of the space elevator, The Fountains of Paradise (1979 Novel) by Arthur C. Clarke, is a must-read!
It's a very well-written novel that focuses on many of the technical aspects of building a space elevator.
Perhaps it is true that "plenty of scientists take the idea seriously" - but the summary links to a book commissioned by the International Space Elevator Consortium.
I am Audience.
As bigjarom mentioned, what's holding us back right now from cheap lift via skyhook is that we haven't quite gotten our carbon nanotube strength up high enough. It's theoretically quite possible.
After that, it's just a question of how do we get enough materials and probably some sort of ribbon* making facility into GEO to actually do the laying. One idea I have is that rather than having to ship all materials to GEO, only to drop it towards the earth, you have a descending constructor that you supply. Though the orbital mechanics of resupplying it can get quite hairy...
*Modern design philosophies has the cable being more of a flat ribbon than circular.
I don't read AC A human right
How else are you to land and/or launch from a new planet/moon? We still need rockets. Unless stargate
It's the scourge of futurists everywhere: The space elevator can't seem to shake its image as something that's just ridiculous, laughed off as the stuff of sci-fi novels and overactive imaginations.
I've first heard of space elevators decades ago, and not once have I read or heard anyone saying it's a ridiculous or laughable idea. All I've heard is that it'd be a really great, smart and economical way to access space, if only a strong and light material could be found to prevent the cable from being several miles across in diameter at the base and collapse under its own weight. Where did the story's submitter get that from?
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
they have a young scientist named Peter Parker working on it.
Some drink at the fountain of knowledge. Others just gargle.
One of the things I don't see discussed much is the potential failure modes for such a system.
My wife is a physical oceanographer, and one of the failure modes for instruments deployed on cables from a ship is a 'wuzzle' -- a large tangle of steel cable. Given the nature of the stuff, a length of cable that fits nicely in a spool on deck can twist itself into a knot larger than the ship.
So one thing I'd like to know is what are the potential hazards a couple thousand miles of elevator cable falling to the Earth's surface? Could we end up with tangles miles in diameter?
I think a space elevator is a great idea if it's feasible, provided that in the criteria for "feasible" we include being prepared for the conceivable ways the project could fail.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
Or, just read the linked report by a team of ACTUAL scientists instead of a SCIENCE FICTION story written 35 years ago.
You can't, unless you want to pay for it.
"First they came for the slanderers and i said nothing."
I assume you are NOT denigrating SCIENCE FICTION, but just to be sure, I will point out that Clarke also wrote about using geosynchronous communication satellites long before anybody had launched one.
i say let's get fusion right first, then invest in SETI programs, then make contact with another intelligent force, then see how they approached the space elevator problem. Then we can apply alien civilization best practices to leap-frog the current space elevator timeline.
In the above book, a Martian space elevator fails (more specifically, is induced to fail by the deliberate application of high explosives.) The result is highly destructive. The Martian equator is no longer an imaginary line, but rather a prominent physical feature.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
SETI as fun as it is seems pretty pointless to me, at least in its current form. I doubt any advanced civilization would use radio communications for more than 200 years. IMO we would be better off looking for other signs, such as Dyson Spheres.
One would have thought that the odds of SETI succeeding were lower than mankind successfully building a space elevator.
If the break is below the half-way point it will go up if the break is above the half-way point it would come down.
Also the process that seems to most likely for construction would be to deploy from the mid point of the cable and then spool in both directions at once. This way the overall forces remain in balance.
Also everything I have read about planned space elevators has it based in the middle of an ocean. This allows some movement if necessary to avoid something large in space but also gives some safety in the event of a failure. If the cable broke below the mid point controlled explosions all the way along the cable would reduce most of the damage with the a large % of the resultant bits burning up in the atmosphere or landing in the ocean. It would probably be much worse for things in orbit than things on the ground.
Taking space elevators to their logical conclusion though would see them being the bases of super towers that reach into space. The cables end up being the foundation supports of the tower.
You are confusing a space elevator with BitCoin.
Or, just read the linked report by a team of ACTUAL scientists instead of a SCIENCE FICTION story written 35 years ago BY AN ACTUAL SCIENTIST.
FTFY.
Clarke had 256 pages and apparently conveyed the general ideas. Paying for 300 pages seems like a stupid thing to do if you want a general idea.
If they cannot communicate how it is feasible in an elevator speech, I don't expect to learn much in the manifesto.
3 pages has sufficed to explain the Higgs (excluding cartoons); I expect to understand the space elevator, in big boy words, in 2 or less. Anything else is hiding something, or so poorly written it cannot be trusted.
Superfluous vocabulary is ostensibly a plausible alternative, however a great many potential readers may find themselves sidetracked by such unnecessary verbosity. As such, I have expectations of a concise manner of thought conveyance as would be warranted by the writers. Vis a vis- said writer probabilistically desires their audience foremost not fall immediately into slumber.
I believe everything below the break point will fall to the ground and also in a path that wraps around the earth. Everything above will go up and stop at a new higher equilibrium point, still straight and under tension.
Why do we need a Space Elevator if we have Transporters?
Really? I was always under the assumption that space elevators were considered a good design and that we were just waiting for materials to present themselves that would be ideal for the conditions.
Well you might also remember that Clark predicted FTL drive in your rush to find a pedestal tall enough.
And maybe you should actually READ the study before dismissing it because it has too many big words.?
Oh, wait, this is Slashdot, we don't do that, do we.
Sig Battery depleted. Reverting to safe mode.
Connected to a platform in space, the mass of the platform is to spin with the Earth's rotation. Centrifugal force is actually pulling on the elevator 'cable'.
$5 / month hosted VPS on linux = awesome!
Neal Stephenson and Keith Hjelmstad who is at Arizona State University have looked into this. The thought is to build a structure that reaches the stratosphere and then launch rockets from the top.
The Tall Tower
I have no idea if this is easier or harder then a fulls space elevator. I would guess not as hard. Sadly, the web site has little activity since I firsrt saw it. Still, it's interesting in the context of a space elevator.
Why is Snark Required?
I don't think these elevators would operate like a normal elevator, where you have cables pulling a structure up, so you wouldn't have to worry about a spool of anything getting tangled. Most designs have the structure actually "crawling" up the cable.
Given the nature of the stuff, a length of cable that fits nicely in a spool on deck can twist itself into a knot larger than the ship.
lol that's kind of hilarious
"First they came for the slanderers and i said nothing."
The super-rich are not the only potential market, people of modest means engage in tourism as well. All the super-rich are doing is helping to pay for the necessary r&d and initial infrastructure. Costs will come down with improved technology and greater experience. Even **IF** tourism was the only potential space industry there would still be a potential market of millions of travelers. Its just a matter of time as costs work their way down the willingness-to-pay curve.
That said, I do not believe the commercial utility of space is limited to tourism. And whether we are dealing with tourism, scientific research or industrial application there will be a point where getting the resources locally will make more economic sense than lifting the resources from earth. That will open up even more commercialization of space.
Have you read it? Let me know if it's any good. To me, it just looks like a scam to get people's money.
No money involved, they give it away for free if you know where to look:
http://www.virginiaedition.com/media/spaceelevators.pdf
Archived here:
http://www8.zippyshare.com/v/72888832/file.html
http://www.sendspace.com/file/16c8xj
http://wikisend.com/download/118300/spaceelevators.pdf
Nanomaterials are strong and light enough, but the rub is that scientists can't get them to scale yet. Luckily, billions of dollars are being poured into this area of research. The report predictsa suitable material will be ready by the 2020s.
Materials are the sticking point and they can predict anything they want. Will those predictions come true? We will only know if and when it happens. I think it is doubtful. From what I can find they have made carbon nano tubes about 130cm long. Extending them to 62,000 miles might not be possible.
Saying something is feasible based on prediction of scientific progress is dubious at best.
If engineered correctly, the total force applied at ground level could be "up" rather then "down".
I almost feel bad whooshing someone with a 5 digit ID. Almost.
Length: 100,000km, anchored on the Earth with a large mass floating in the ocean and a large counterweight at the top end, called an Apex Anchor.
Width: One meter
Design: Woven with multiple strands to absorb localized damage and curved to ensure edge-on small size hits do not sever the tether.
External Power: The power must be external as the gravity well is extreme and lifting your own power is a non-starter.
Dr. Edwards’ approach was to use large lasers pointing up to the climber with a “solar panel like” receiver on its nadir position.
Cargo: The first few years will enable 20ton payloads without humans [radiation tolerance an issue for the two week trip] with five concurrent payloads on the tether for the two-week trip to GEO. [Currently, the plan is seven concurrent payloads for one-week travel.]
What could possibly go right?
Cryonics - Keep cool and carry on.
"You can't, unless you want to pay for it."
And quite a bit. Around $30 is a lot for a "report".
Makes me think this is yet another attempt to sneak in an ad disguised as a discussion piece. We've been seeing an awful lot of those lately.
Actually, its very easy to make (though depending on your definition of "flying pigs" and if the pig has to be alive in the end; i.e. can we use a cannon or a plain or does the pig have to do its own thing) and might have some good uses.
Yeah, if you want a materials strength nightmare, forget about the elevator cable.
Think about a foundation strong enough to withstand the pressures of a 100-200 mile high tower pressing down.
Why don't you think about familiarizing yourself with the concepts behind the space elevator? There won't be anything like that. The end of the cable "floats" in the receptacle. It hangs from its anchor asteroid.
Oh wait! Lemme get my unobtainium!
Why don't you instead get a quick education in the topic we're discussing before you flap your yap?
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
In a novel by Frederik Pohl, one of the heechee series, terrorists set off a bomb at the ground terminal of a space elevator and it causes the rope to fall to the ground.
Someone found a free copy of the report. Enjoy.
"First they came for the slanderers and i said nothing."
Here's a link to the actual report, so enjoy.
"First they came for the slanderers and i said nothing."
Falling to Earth? Why would it?
Because the cable would break as a result of fatigue from the massive strains placed on it. Seriously, we're talking about a 22,000 mile cable where a single fault could cause the whole thing to come crashing down.
"First they came for the slanderers and i said nothing."
And thus another duplicate ID is outed.
Sig Battery depleted. Reverting to safe mode.
Apart from Ecuador or Africa, the equator is mostly ocean
Using the elevator for transfer of goods - will work but the goods will get a huge dose of radiation
Using it for transfer of organic matter (i.e. humans) above LEO is not feasible due to the speed/shielding needed
The worst part of Van Allen belt is about 19000km wide and starts at around 7000km high. Apollo moon missions passed trough it at roughly 15km/s, spending roughly 2*21 minutes in it.
The astronauts received roughly 1rem of radiation through 3 layers of thick aluminum radiation shielding.
That is 1/5 of the yearly the limit in US for people working with radiation.
At reasonable speed (~200m/s) the elevator would take ~26h to pass through the belt, meaning it would need at least 75x more radiation shielding than Apollo did and that the lift would need 15m thick aluminum honeycomb walls (using 70's technology).
Even with todays technology the shielding will be way too bulky/heavy for elevators to be viable alternative to rockets for above LEO human transfer.
>>You loons haven't even built an upper atmosphere elevator
Right, because an "upper atmosphere elevator" is completely infeasible. A space elevator would have to be taken into space in pieces, constructed there, and the cables rolled "down" to earth from an anchor point a hundred thousand miles out. The science behind it is perfectly sound - unfortunately we lack the material necessary for the "cables", at least in any manufacturable form.
But an "upper atmosphere elevator"? The science behind that is not sound. Besides making a pyramid with a base of 10,000 square miles, there's no way to stabilize a structure at that height without something anchoring it in place from the space end.. you'd need... a space elevator to do that. :p
"The true measure of a person is how they act when they know they won't get caught." - DSRilk
Arthur C. Clarke was actually a scientist who wrote science fiction. The actual bulk of his work was science education.
Probably because it's best modelled as a lot of little chunks each with different gravitational force on them and forces from the elements above and below - and that's not trivial if the thing has a break in it somewhere.
The simplest mode of failure is if the thing is under a huge amount of tension and somebody cuts it off at the base - as in at least one movie. In that case the entire thing flies off into a high orbit (for the counterweight, trailing the ribbon behind it) or escapes entirely. Having a huge amount of tension make sense in keeping it straight, but of course constraints of reality would get in the way if we finally have a real material that comes close to having the right properties for an Earth based space elevator.
What do you think the pyramids were for?
What do you think pyramids are foundations for?
Not so simple. Gravity varies with distance along the length of the beanstalk. Also whether it snaps in two unequal lengths or fragments depends on a few things. Being designed to fragment and burn up (like your suggestion) sounds like a good idea, and it's likely without explosives since there's not likely to be any room for overdesign. Large stresses from other then the direction it's designed to take it are going to rip things apart if it's something like carbon nanotubes.
Easy - you have it pulling up. :)
Then you have a different nightmare
People who live within a few hundred kilometres had better not be scared of spiders.
A robust system should not totally break because of one point of failure. A single elevator is fragile because any natural (meteorite), man-made (space junk) or intentional (war) cause acting anywhere along the 100'000 km long cable can totally destroy it with dramatic consequences on Earth when parts of the cable impact the surface. The elevator design could be made more resistant by building a network of cables, not a single cable.
the desire of anyone with the ability or funds to do it to go to space
Not only the desire to go, but some destinations ("space" is not a place) are necessary, too. I would expect that the main use of this device would be for freight, not people. For a start the safety requirements are much less stringent (apart from if it collapses on top of people) and therefore the implementation costs would be less.
There's also the little matter of geography. A space elevator would have to be built on or near to the equator. At present none of the equatorial countries have the will, means or need to build one. In the past the imperial powers have created global infrastructure, but there are no more imperial powers and there is not sufficient political stability for others to want to risk 10's or 100's of trillions of <insert name of preferred currency here> in some tropical location outside of their control.
politicians are like babies' nappies: they should both be changed regularly and for the same reasons
Sadly, my slow education shows that you need some as well since the material is still currently unobtainable. Not beyond hope but we can't get it now - hence "unobtainable"
That's overload. Fatigue is lots of little overloads making cracks grow over time.
Also whether it goes down, or up, and then bits of it down later, depends on a lot of things, like how much tension is on the thing. Even if it snaps off at the top end the forces of re-entry are likely to break it up a lot as bits of it decelerate at different speeds and pull on each other. Then will it burn up or stay intact like the graphite crucibles used with molten iron? We don't know enough about the properties of what's likely to be used, apart from the obvious of the minimum strength to weight ratio for it to work at all.
Read the study? I'm impressed when someone here takes the time to read the summary!
Required reading for internet skeptics
I've always liked the idea of space elevators, but I've also been bothered by a problem that I've never seen addressed, "micrometeoroid erosion". Sure, you can build one. But how long is it going to last, with nothing to protect the main cable/strands/shaft/whatever-you-want-to-call-it from a near-endless --though admittedly low-rate-- series of impacts by speedy dust particles?
And definitely less than I spend in beer when I go out. Don't be so cheap that you're left behind... Buy it!
MSBPodcast.com The opinions expressed here are my own. If you don't like 'em... Think up your own stuff.
If the break is below the half-way point it will go up if the break is above the half-way point it would come down.
Actually, everything below the break falls down, and everything above the break falls up, no matter where the break occurs. The centripetal acceleration is capable of holding the entire mass of the cable plus the weight of all the cars, plus some force to tension the cable. The falling down is also generally not that catastrophic, for the most part, since the max speed of the falling cable will be less than or equal to 50% of terminal velocity for a naked cable due to transverse forces based on the pull from the rest of the falling cable. If you don't assume a naked cable, but a cable with periodic airfoils, the remainder of the cable could be guided to a safe fall shadow.
My problem with that is it assumes infinite strength of the cable and a simplistic 1D model of the forces - HOWEVER THAT DOESN'T MATTER IN THE CONTEXT. It's just a background special effect and not important to a story where any disaster would do and I doubt the author looked into it in as much detail as many on this thread.
I had a long and boring discussion with a bunch of arts students some years ago about that example when they insisted it was what would really happen (which is not a line the author took - just those students) instead of a nice neat fictional disaster to move the plot along. As soon as I started drawing diagrams and mentioned that the pull of gravity will vary over the length of the cable they got very hostile.
A real answer would be more complicated and messy and there would likely be chunks of cable raining down on people's heads over a wide area of the planet for weeks. however that would mean a different and probably far less interesting plot.
Cool! Thanks!
Up mod parent:
http://www.virginiaedition.com/media/spaceelevators.pdf
We don't even know that much, but we may be getting close.
First floor perfumery, stationery and antimatter......
Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.
A well engineered space elevator would be a new source of power, producing more than it would cost to maintain it. Assuming that some form of mass (captured asteroid, lunar regolith, etc) could be delivered to the geosynch platform.
Regenerative braking on material moving down the elevator would produce power. A particularly elegant system would launch cannisters of regolith from the lunar surface to the geosynch platform with a railgun, then the cannisters are "dropped" down the elevator with regenerative braking moderating the descent. At a way station in the stratosphere the cannisters are offloaded to gliders that then ship the regolith to its points of use: as low cost aggregate in road building and construction. Most of the cost of concrete is in transporting the aggregate from quarry to point of use; this approach eliminates those costs and is environmentally benign.
So long as the mass moving down the elevator is sufficiently large, there would be a surplus of power.
There is probably something basically wrong with this; it seems to simple. But I like the idea of seeing buildings in my neighborhood built of Moon rock.
Will
It was also, sadly, complete bullshit ("sadly" because it's one of the worst research failures in the series, which is otherwise fairly good hard sci-fi). The material he envisioned making the cable out of was not only wildly impractical, it was apparently chosen explicitly because of several characteristics it exhibited that are exactly opposite of what would be desirable. You need a material with an extremely low mass per unit length. You do not need a highly durable material, certainly not on the scale of diamond hardness. You also want a ribbon, not a true cable. That gives the climber more surface area to grip for a given amount of mass per unit length.
The result would be more akin to a silk scarf a few feet wide (at the base, several times that at geosync) and many thousands of miles long slowly falling to earth. Some, possibly much, would be burned up in the atmosphere. Some more would flutter to the ground, buffeted by the winds but no more harmful than if some airplane unspooled a bunch of tissue paper in the high atmosphere and then let it go. Some places it might tangle and fall to the ground in a knot, but even then it would have a fairly low terminal velocity and relatively low mass. You might destroy a building or two in the worst case; you would not wreck the entire circumference of the planet
The very concept of building the ribbon out of anything that could contain the energy needed to produce a "kilometres-wide path of destruction" without harmlessly burning up in the atmosphere is as idiotic as it is unrealistic.
There's no place I could be, since I've found Serenity...
Ocean, actually. We have rather a lot of it, especially around the equator.
Sigh. This whole "the cable could fall and kill us all!" bullshit has been debunked again and again, but still people keep pulling it out of their asses like they have any idea what the fuck they're talking about. Do at least a little research before spouting your mouth off, OK? For starters, ribbon, not cable. Think silk scarf, not suspension bridge.
Oh, and as for the idea that where you built it would matter for people living "in the cable fall direction"... you really don't get the scale of this thing, do you? The Earth's circumference is less than 25000 miles. The distance to geostationary orbit - which is the shortest such a ribbon could be, realistically it would be about twice that - is more than 22000 miles. If it *did* fall, and somehow survived re-entry and came down in one continuous piece, it would probably wrap around the equator. But that wouldn't happen, because any material which could survive such a fall would be completely impractical for use as ribbon material in the first place!
There's no place I could be, since I've found Serenity...
Protective polymer coating, topped up every time the car passes over it?
Arthur C Clarke was not what most people would think of as a scientist (a job leading scientific research for a university or company or so forth). Nor did his scientific speculations revolve around applying the scientific method, which is a good description of what a scientist does in a very broad sense.
Slashdot: providing anti-social weirdos a soapbox, since 1997.
Don't worry, Monsanto genetic engineers are working on it...
Not a space elevator, as it has to be located at the equator to be able to rotate with Earth.
Think what you will, accuracy be damned.
Perhaps it hasn't been addressed much, but from what I've seen part of the 'protection' is that you would be more or less continously extruding new cable(on the order of a couple miles a day!), so as time goes by the cable WOULD be refreshed.
Besides that, if you're sensible you're going to orient your ribbon so it's the narrow end that's facing most probable impacts, highly limiting it's cross section. Then you have to factor in that this material will be the strongest material used in space to date; it should be quite resistant to those effects.
I don't read AC A human right
This probably would be possible but not worth doing. With direct space access, the cost of space-solar power goes down to practically nothing, and it would be easier to beam a steady stream of energy via microwaves then try and capture surges from decelerating payloads (i.e. trains do this, but the energy is just loaded through resistors elsewhere - its a way to keep subway tunnels cool).
The real benefit is just access to space-borne resources. We'd have such a large new playground to take whatever we wanted from, without affecting the Earth's biosphere one bit. The drive for space industrial development would be huge the second it was demonstrated even barely break even.
Main problem I foresee is what happens when someone presses all the buttons.
Make sure the contra-weight is large enough to attract an atmosphere.
There's always a neat solution.
If Pandora's box is destined to be opened, *I* want to be the one to open it.
They were before the crust shifted, same thing happened on Mars, look at the crater distribution of the red planet and you can see how the crust shifted 90degrees.
Nope, it is pretty easy to balance it in such a way that it will float. This is done by making the end longer/heavier to get it to pull more or shorter/lighter to make it pull less.
Yet another example of sci-fi authors completely failing to consider the "sci" part of sci-fi. If you bombed the base of a space elevator, the ribbon would fly *in to space*. The bottom is an anchor, holding the ribbon (not "cable" or "rope") to Earth. Ideally it's not under much tension - the high-tension part is the middle bit which sits at geosync, balanced between the pull of gravity and the centrifugal force of the upper segment/counterweight - but it's almost certainly under some (much like a ship's anchor chain, actually). How the fuck would cutting a ship's anchor cause it to sink? That's about the level of stupidity in what you just said.
There's no place I could be, since I've found Serenity...
If they cannot communicate how it is feasible in an elevator speech
Depends on the elevator... a space elevator speech could last hours, if not days. ;-)
XML is like violence. If it doesn't solve your problem, you're not using enough of it. --AC
*SIGH*
Nope! Wrong again.
The ribbon (not cable) is balanced such that at the base point, gravity counteracts centrifugal force, and the tension is near-zero. If the tension is any higher than that, that means the whole ribbon is subject to more tension than it has to be. It also means your counterweight (which is probably just an equal length of ribbon *above* GEO to counteract the length below) is heavier than it has any reason to be, which would make launching the whole thing more difficult.
The base could easily be placed on a barge in the middle of the ocean. In fact, that's just about ideal; it can move around relatively easily, if the ribbon needs to dodge out of the way of something. It's also easier to control access for the sake of security, and may have a handful of political advantages too. Oh, and the base of the ribbon? Kept under tension by means of winches. The ribbon will actually rise and fall a bit, as climbers go up and down it (climbers near the bottom tug the whole thing downward, reducing tension at base to possibly negative unless you take up the slack). That's OK.
There's no place I could be, since I've found Serenity...
So, in order to prevent the whole thing from crashing down, there has to be a safety margin of extra ribbon above GEO, meaning some extra tension in the wire, even at ground level. That barge can't be too light-weight, or else it'll turn into a space-barge...
and when they realised their mistake, they started building those pyramids in Central America and Polynesia instead.
how do we get enough materials and probably some sort of ribbon* making facility into GEO to actually do the laying.
There's no way this will get built with materials launched from Earth, it will have to use resources mined in space. Just the segment from terra to GEO will have to be 23 thousand miles long; even just for a single "strand" we don't have a vehicle that can lift anywhere close to that much material. Lifting all the "strands" necessary would take many thousands of launches.
OTOH, once SpaceX gets its reusable boosters working, it will be much cheaper to get up there. That will speed up the development of space-based industries (such as asteroid mining) that would make this project more feasible. It's not inconceivable (barely) that such a project could be undertaken in my lifetime, but I rather doubt it.
In the meantime, a rotating skyhook seems much more viable, especially for the moon.
XML is like violence. If it doesn't solve your problem, you're not using enough of it. --AC
Cairo is almost dead on the equator.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
They feed pigs with wild hemp in Bhutan, does that count?
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
If they cannot communicate how it is feasible in an elevator speech....
Ah, but you forget, a space elevator speech is a lot longer ride!
Speed of Light: 299,792,458 m/s (meters per second)
Great Pyramid Grand Gallery: 29.9792458N Latitude
coincidence?
Some drink at the fountain of knowledge. Others just gargle.
thinking of the pig from sinfest :D
http://sinfest.net/archive_pag...
Lifting all the "strands" necessary would take many thousands of launches.
Not from what I'm seeing. At least one source says that a 'starter' cable can be had as light as 9 metric tons. Another says 20.
A Falcon Heavy can lift over twice that to orbit, though maybe not all the way to geosync...
After you get the first thread down, you use that thread to lift more mass to increase capacity.
I don't read AC A human right
Forget Pizza Hut drones, where's my pork chop cannon?
Wow. NONE of you actually read the post I replied to.
Taking space elevators to their logical conclusion though would see them being the bases of super towers that reach into space. The cables end up being the foundation supports of the tower.
I was specifically talking about a tower, as opposed to merely a cable-based elevator.
Chas - The one, the only.
THANK GOD!!!
Cairo is almost dead on the equator.
huh?
https://www.google.com/search?...
30.0500 N, 31.2333 E
Cairo, Coordinates
-Kz-
You are contradicting yourself. If a single car is sufficient to pull a "balanced" tether out of orbit, then only a similarly small outward force is necessary to counter the force of a car, therefore even a small base-mass (such as a ship or barge) is sufficient to counter that outward force. Ie, if a one tonne car pulling down at 1.5g would pull the tether out of orbit, then you only need a few tonnes outward force (measured at the base) to prevent that. And thus only a few tonnes beyond that to sufficiently anchor the tether down.
Therefore you do not need to "drill really deep into bedrock to suitably anchor this beast".
(In reality, you'd want an outward force a full order of magnitude higher than the cargo capacity. And an anchor-mass another order of magnitude higher than that. So a 1 tonne payload, a ten tonne outward force, a 100 tonne base. Double or triple for reserve. Well within the capability of even a small ship or barge.)
A bigger problem is actually the sidewards torque due to Coriolis as the cars rise and fall. This creates not only additional pull on the cable/ribbon, but specifically bends or crimps the ribbon as the car passes. This will stress the material well beyond the simple linear forces.
Science is all about firing a drunk pig out of a cannon just to see what happens.
I'd like to see a stability analysis on this kind of system. I suppose it would be a nice exercise for the student, so maybe I'll give it a whirl when I've got some downtime.
Clarke also invented the communications satellite. Or, the idea of it.
One day I feel I'm ahead of the wheel / the next it's rolling over me / I can get back on / I can get back on
Like everyone else looking at this, they assume we'll have to use a carbon nanotube tether. They propose a spun tether of nanotubes, but use the strength of individual nanotubes in their model. Nanotube yarn is about 1/10 the strength of the raw material (which is insufficient). Growing the raw material directly would only take a few thousands of years more than the four they plan on using.
You don't actually know anything about Clarke's work, do you?
http://scifi.stackexchange.com...
One day I feel I'm ahead of the wheel / the next it's rolling over me / I can get back on / I can get back on
If you think flying pigs are hard, you obvious have had a Roadrunner cartoon defincency since childhood.
Apocalypse Cancelled, Sorry, No Ticket Refunds
During a speech he once gave, someone in the audience asked Arthur C. Clarke when the space elevator would become a reality.
"Clarke answered, 'Probably about 50 years after everybody quits laughing,'" related Pearson. "He's got a point. Once you stop dismissing something as unattainable, then you start working on its development. This is exciting!"
Makes sense to me; original link here.
We have both people worried about space elevator cables crashing to earth if an airplane hits one and people concerned about SETI not picking up incidental radio leakage from alien civilizations on the same story.
Can I get somebody to please express concern about the LHC creating a black hole on Earth so I can go home for the day?
My God, it's Full of Source!
OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
if you're sensible you're going to orient your ribbon so it's the narrow end that's facing most probable impacts
That's what she said.
All my liberal friends think I'm a conservative, all my conservative friends think I'm a liberal.
We need to develop extremely high strenght carbon fibers not only for a Space Elevator but for vehicles and such because it's a great way to offset all of the extra carbon being released. Hell if we can use enough of the free carbon, we can cool the earth and gain quite a bit of arable land back from the oceans plus with a quad set of Elevators and a connecting ring, we could move most if not all of our farming to orbit. Lots of possibilities there and I would love to see such before I release my keyboard/mouse from my cold dead hands.
Mod me up/Mod me down: I wont frown as I've no crown
If God had intended man to elevate, he would have given him counterweights.
yeah, building a 13 GT space elevator from carbon nanotubes seems like a great idea -- until the nanites come looking to use the carbon from your body.
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
Their estimated price is $500/kg which is a ridiculous price.
Today a falcon 9 can launch 13150kg to LEO for $50million.
The projected elevator can lift 13150kg to LEO for $6.6million.
A nice improvement until you consider that a reusable falcon 9 launch will cost perhaps $500,000.
Which means Space-X with a little luck can reach $38/kg.
It is not hard to imagine that with modest success at re-usability Space-X can drop the cost from $50million to $5million with just a reusable first stage, which would make the Space-X price $380/kg.
That makes space elevators uneconomical before they are even built.
Now a careful reader will note I am arguing GEO vs LEO prices. Once in LEO a ion engines can be used to make the transition to a higher orbit with all of the same efficiencies of an elevator and they already exist.
I fail to see the economics of a technology with a huge up-front cost and that it looks like a much less expensive investment in rocket technology can devastate.
So turn it sideways so that one slightly non-tiny object can destroy the entire ribbon? :-)
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when it come down? Having something that can wrap around the globed several times may not be such a great idea when it breaks at the anchor point.
The Kruger Dunning explains most post on
I recall seeeing a youtube video where a scientist set a pile of carbon nano-tube fibers on a surface and flashed them with a typical photo-strobe, and after a few seconds sparks were visiable in the fibers and a few more the pile burst into flames! So appearently the plan is to take one of the highest conducting non-superconducting materials we know of, attach it to the Earth at the equater where almost daily rain and thunder storms occure due to the moisture and static generated by the Trade winds and have machines shinny up and down the worlds biggest lightning rod that is likely to burst into flames if lightning even gets near it; man I would love to see that!
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Seriously, we're talking about a 22,000 mile cable
No. It's at least double that. A space elevator doesn't just go up to GEO, it's "balanced" at GEO, there's an entire outward arm. (And in reality it would be under tension, so the outer arm would be more massive than the inner, the balance point would be well below GEO.)
where a single fault could cause the whole thing to come crashing down.
No fault could cause the "whole thing to come crashing down". Only the portion below the break could fall. And since it's a known failure mode, you'd have built-in separation points at various lengths. When there's a failure, you release a piece of cable/ribbon at the top and/or bottom ends of sufficient mass to allow the centre section to go into a stable orbit. This allows recovery and repair.
Science is all about firing a drunk pig out of a cannon just to see what happens.
Actually in a design I saw some time ago, the cross section of the ribbon would be more like an arc of a circle. No straight line path of a micrometeorite would be capable of severing the cable.
Conversely, you don't know what scientists do, do you?
They don't write down neat ideas in single page essays that get no scientific review. Maybe you could say he was an inventor?
It was a neat idea, but Clarke wasn't the first person to come up with the idea, nor was his short essay widely disseminated, nor did it influence the actual development of geosynchronous orbits.
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making facility into GEO to actually do the laying.
Facility? laying?
You launch up a spindle of ribbon. You take the loose end of the ribbon, and you chuck it towards earth and unwind the spindle. Gravity takes over and pulls it's end down.
(You also take the other end of the ribbon and throw it out away from earth, centripital force takes it and pulls it up.)
There's really no "laying" of the ribbon. But hey, sure, putting some sort of station at GEO with the ribbon is probably a good idea. Something with thrusters that can make corrections and, I dunno, store all the crap they send up there. But initially, the thing that does the unspooling is just whatever vehicle that carried it there.
You are correct up to the fourth word.
Excuse me, but please get off my Pennisetum Clandestinum, eh!
Then you have to factor in that this material will be the strongest material used in space to date; it should be quite resistant to those effects.
I don't have the numbers handy, but I'm thinking the ribbon material is a couple orders of magnitude at best stronger than conventional materials, while impact energy is MANY orders of magnitude higher than the "strength" in question.
To put it another way, if an impact dumps enough energy to raise several cubic millimeters of material to a five-figure Kelvin temperature, the "material strength" becomes somewhat irrelevant. Vapor/plasma doesn't resist tension very well.
In fact, I'd think that stronger materials would receive more transferred energy from an impactor as it's punching through. You'd just have to count on having enough material left to hold things together.
Actually there are proposals that take the properties of modern super materials (carbon composites) and calculate the maximum height of a (compression) tower. And, depending on your assumptions, you can actually get above 100km. Even steel towers could theoretically get to 10-15km using modern designs.
There are also designs for rotating orbital tethers which have a tip-velocity equal to the Earth's surface velocity, dipping into the atmosphere to pick up airborne payloads. (Or tower-borne if you combined it with the 100km carbon-tower.) From an engineering and economic standpoint, these are much simpler than a full space elevator, since they require much less strength in the materials, and are built at much shorter lengths.
There are also proposals for neutral buoyancy towers which are... theoretically... possible. (Essentially a series of hydrogen-filled balloon toruses stacked on top of each other, creating a net lift sufficient to hold another tower on top, above the bulk of the atmosphere.)
Science is all about firing a drunk pig out of a cannon just to see what happens.
At one time I believed that the space elevator was the only way we would ever be able to move into space on an economic basis. All rocket based methods were just too expensive. That was until I read what Elon Musk had to say about it http://www.spacex.com/news/201.... The real reason that space exploration is expensive is that we throw away the spacecraft after a single use not the fuel used to get there. Space elevators are very energy efficient and would have great longevity, however, the practical and economic problems of building a 30,000 mile long cable is vastly larger than the problems of solving reusability of spacecraft. SpaceX is well on the way to solving the reusability problem. They have a practical road map and are executing it in spectacular fashion. They have already tested and proven vertical rocket powered landing technology and on their next Space Station resupply mission they will be testing booster landing leg deployment and engine restart to try and achieve a soft splashdown in the ocean. There last attempt of restart was successful however the descent became unstable and they had to abort. It is believed that the landing legs will provide extra aerodynamic stability allowing for a successful soft splashdown. I believe it is only a matter of a few years until they have a fully reusable system. This innovation will drive down the cost of space travel by a factor of 100. In 10 years the average upper middle class American will be able to afford a vacation in space. Travel to Mars will still be expensive but not unattainable for many.
Cover it with a good thick layer of whale oil...say Minke or Blue Whale, still got plenty of those left!
All those moments will be lost in time, like tears in rain.
Actually, unlike a beanstalk, skyhooks are potentially viable using nothing stronger than common carbon-fiber - you really only need a thousand miles or so of cable to make a tumbling skyhook that can transfer you between atmospheric-speed sub-orbital and near-moonshot orbits. Still some serious challenges in making a strong enough cable that can span the US, much less getting it into orbit and keeping it from being destroyed by orbital trash, but theoretically at least it's well within the limits of current technology.
Of course it's not quite as sexy as taking an elevator directly from the surface into orbit, but those Airship-to-orbit folks seem to have solved most of the major issues with surface-to-dark sky airships, which could be the ideal platform for rendezvousing with the (locally) slow-moving tip of a skyhook above any potentially problematic weather. And a tumbling skyhook would be far faster and more energy efficient than either a second-stage airship or any beanstalk climber possible with existing technology.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Unfortunately, it's also highly feasible as a terrorist target. How are you going to patrol the entire span of the cable for kamikazes?
"Love heals scars love left." -- Henry Rollins
Or...
Christians
Jews
Communists
White supremacists
Environmentalists
Neo-luddites
Unionists.
And whatever the fuck these guys are.
Science is all about firing a drunk pig out of a cannon just to see what happens.
The space elevator can't seem to shake its image as something that's just ridiculous
Maybe because it IS ridiculous. It's a cool idea but it is science fiction and will remain so for the foreseeable future.
But there are plenty of scientists who take the idea quite seriously, and they're trying to buck that perception.
Plenty? No there aren't. We do not have the technology to build this and will not have said technology anytime soon. I know someone will say "but carbon nanotubes!" and they are still in the realm of science fiction when it comes to uses like this. Even if we did have the technology, the economic case for it is far from clear. This thing would be hugely expensive, potentially incredibly dangerous (imagine it breaking), requires technology we aren't even close to having, have an uncertain economic payback, be a target for terrorists, etc. Maybe in a few hundred years it will be possible but it isn't going to happen in the lifetime of anyone reading this.
To that end, a diverse group of experts at the behest of the International Academy of Astronautics completed an impressively thorough study this month...
Which you can buy in hardcover for just $29.95. Perhaps if they were really serious about it they might not be trying to sell the report for a profit.
It's a space elevator speech. You'll have plenty of time.
"Molest me not with this pocket calculator stuff."
- Deep Thought
If they cannot communicate how it is feasible in an elevator speech, I don't expect to learn much in the manifesto.
It IS an elevator speech - a SPACE elevator speech - that takes three days to get to the top floor...
unfortunately we lack the material necessary for the "cables", at least in any manufacturable form.
That is just the tip of the iceberg of things we lack. The cables are just the most obvious missing technology. You need things like power, HVAC, orbital debris removal, meteor defense, terrorist defense systems, a base strong enough and heavy enough to hold on to it on both ends, elevator systems, servicing equipment, some way to actually construct the darn thing and equipment to do it, vastly more advanced robotics, and much much more. These things might be more mundane but they are no less important and all of it would have to be developed. Many of the problems are probably solvable but that doesn't make them trivial.
Why, the equator doesn't rotate independently of the rest of the planet? We might assume that having the center of pull ouside of the diameter of the cable would cause concerns about the cable being strong enough, or it would give the cable an "Up and Down" side would be bad. The cable would of course have to be "landed" on or above the equator,but then it could be towed to its intended attachment site.
Additionally when we think of the term equator, most of us you the geographic definition of a fixxed line half way between the poles or at right angles to the axis of planetary rotation, yet we'd need an astro-physists's definition because the planet isn't of homogenous density, and there are tidal forces from the Moon and Sun tugging various changing eccentricities into the system so the differnce in the cable landing at a site micro-radians from the moving equator and one 20 or 30 degrees from the equator is quantitative not qualitatiive; a cable 52,398 miles long is going to amplify an error a lot.
Apocalypse Cancelled, Sorry, No Ticket Refunds
I've always liked the idea of space elevators, but I've also been bothered by a problem that I've never seen addressed, "micrometeoroid erosion". Sure, you can build one. But how long is it going to last, with nothing to protect the main cable/strands/shaft/whatever-you-want-to-call-it from a near-endless --though admittedly low-rate-- series of impacts by speedy dust particles?
I imagine they'd do something similar to how some of the new suspension bridge cables are designed. The main cables are actually cable bundles, and they're made so that individual strands can be replaced if necessary.
Yeah, because we're totally sure that FTL will never ever ever be possible.
Unity? Screw that: XFCE. Slashdot Beta? Screw that: SoylentNews. Australis? Screw that: Pale Moon. UX developers DIAF
Talk to a physicist.
The point is that Science Fiction authors have to simply assume some things into existence, usually without a lot of explanation or examination of the actual science behind it. They need a hook to allow stuff in their stories that can't be done, either at the time or ever.
That they get lucky sometimes, and something actually comes true is always attributed to huge omniscience and foresight.
Clark was no different. He was just more well read than most. He didn't even invent the concept of a space elevator. A couple of Russians did.
Sig Battery depleted. Reverting to safe mode.
Where did the story's submitter get that from?
Even its biggest proponent acknowledged that some people laugh at the idea. In response to the question "when will the space elevator be built?" Sir Arthur C. Clarke said "about 10 years after everyone stops laughing."
That that is is that that that that is not is not.
Then you have to factor in that this material will be the strongest material used in space to date; it should be quite resistant to those effects.
I don't have the numbers handy, but I'm thinking the ribbon material is a couple orders of magnitude at best stronger than conventional materials, while impact energy is MANY orders of magnitude higher than the "strength" in question.
To put it another way, if an impact dumps enough energy to raise several cubic millimeters of material to a five-figure Kelvin temperature, the "material strength" becomes somewhat irrelevant. Vapor/plasma doesn't resist tension very well.
In fact, I'd think that stronger materials would receive more transferred energy from an impactor as it's punching through. You'd just have to count on having enough material left to hold things together.
Correct.
Stronger materials are worse in structure impact scenarios because they transfer nearly all of the energy to the structure. You need flexible materials, a non-rigid design, and break-away failure modes. This all then necessitates a very redundant (and thus large) structure. If your carbon nanotube cable/ribbon takes a high-energy impact, the issue isn't the entire cable/ribbon surviving, it's preventing the energy from transferring to the structure (the anchors and the payload).
I say build it with 3 times as many cables as needed, and install electronic sensors to measure impacts on each cable. When a sensor detects an impact, it can signal to the anchors to cut its cable. Since the cable isn't perfectly solid, the sensor has a good chance of telling the anchors to cut the cable before the energy from the impact reaches the anchor. The cable becomes slack and can't transfer the impact energy to the structure in anywhere near as direct a fashion as if had remained under tension by both anchors. You could incorporate this into the elevator car, too, so it has the option of cutting a cable. You just need to have sensors spaced strategically so you can reliably signal and execute the cut before the energy reaches the structure.
Could we end up with tangles miles in diameter?
Maybe, but it would be a very low-density object with lots of surface area. With such a tiny ballistic coefficient, the atmosphere would slow it down to a very low terminal velocity and it would hit the ground (or more likely, the ocean surface) gently.
That that is is that that that that is not is not.
The Space Elevator Will Mean: Less Parking, Weird Ribbon Thing, Constant Loud Whirring Noise, Increased Space Elevator Truck Traffic. Developers have submitted plans to build a massive space elevator in Williamsburg! This monstrosity, completely out of context with existing development in the neighborhood, will be accessible only to the wealthy, forcing thousands of average Williamsburgers from their homes and live-work spaces! Jobs the elevator will generate (operators, repairmen, astronauts) are certain to go to non-residents! Don't sit idly by and let this elevator cast its impossibly long, cold, and very narrow shadow over our homes! CALL 311 AND TELL THEM 'I JUST DON'T NEED THIS SPACE ELEVATOR!'"
Then read the study
They address micro-meteorites, lightning, induced currents, radiation exposure, and a whole host of other objections. The biggest problem they identify is the obvious one. We don't have any materials to build the tether with yet.
They "project" that such materials will become available in the 2020's, which is good....that's a whole 14 years before nuclear fusion!
There was a proposal a few years ago that looked at construction in detail. If you could get an adequate strength material (which is hard enough to make on the ground, making it in orbit is going to be even harder) you don't really need to lift that much of it to get started. I think they were talking about a half dozen shuttle launches or something.
That gets you an elevator with a low lift capability. You use it to lift more cable to make the elevator stronger. Most of the mass of the final tether is lifted efficiently with a space elevator rather than rockets.
That depends on the science fiction. The classic hard SF writers (like Clarke) tried to outright make things up as little as possible, and then only when necessary. Fountains of Paradise, for example, didn't really make anything up except a material strong enough to make a space elevator out of. As you pointed out, the concept itself was worked out before, and, assuming the materials and some way to get them up there, the concept is sound. Much of hard SF is aimed at considering the implications of the technology that is likely to result from existing science.
Many hard SF writers are actually physicists, engineers or astronomers of some type. Clarke had a degree in physics and mathematics, worked on RADAR during WWII and wrote technical papers for the British Interplanetary Society regarding geostationary telecom satellites (another idea he "assumed into existence" in his books).
Most people don't know what scientists do, including many people who call themselves scientists. People who develop technology are engineers, although that title is claimed in a lot of places to mean someone who can take responsibility for designing and/or building something (like a bridge or a twinkie package). Applied scientist is a weird term that is often used to get around that, but applied science often isn't much like the science you're thinking of.
Clarke did various things typical of an applied scientist or engineer. That's presumably what the OP was thinking of when he said "physicist."
Three possibilities, depending on where the break is:
1) cable being flung out into interplanetary space
2) pretty reentry effects and most of the cable burning up
3) somewhere between zero to a dozens of kilometres of lightweight cable falling to the ground.
The magnitude of the Coriolis force depends on how fast you go. The first space elevators will probably be cargo only, with climbers that take weeks to make the trip. We might decide that space elevators simply aren't a good option for people or rapid transport at all. Or maybe the rapid transit cars need to have small lateral rockets to compensate.
That's not engineering, it's wishful thinking. Which is not to say it is *wrong*, just unjustified.
The system is designed to be in static equilibrium, so it is by no means guaranteed that the kind of results you are envisioning are the only possible alternatives.
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Considering all the atmospheric forces on the cable, plus the length, having the anchor point even 100 miles from the equator probably wouldn't make a significant difference. That 100 miles is the short side of a very long triangle. In fact I could see having two (or more) cables anchored a hundred or two hundred miles apart, converging above the atmosphere somewhere. If each is strong enough to hold the thing together in an emergency, then even if one is damaged by something the other(s) can take up the slack, prevent the entire thing from falling down/apart, and provide continued service to allow repair machinery and materials to continue to be transported. In normal times the multiple cables would provide additional capacity.
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
FTFY
"They have gun control in Cuba. They have universal health care in Cuba. So why do they want to come here?"-Paul Harvey
Sorry that was what I meant - just put it terribly.
You didn't actually say anything in your post. Do you have another reasonable failure scenario? If so, spit it out and we can talk about it.
He's also the one who first wrote about geostationary satellites. :)
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
In reality, you'd want an outward force a full order of magnitude higher than the cargo capacity.
The number of people talking about the issue of balancing the elevator makes me think perhaps I have misunderstood. I figure I'd probably put a counterweight mass on a climber above geostationary. Geostationary is where things balance, right? The mass above geostationary (at angular velocity of 360 deg / day) wants to fly away, and it holds up the ribbon. Want to put a heavy load on the ribbon bottom? Send a signal to have the counterweight climb further up (which, past geostationary, feels like down to it, right?), increasing the amount it pulls up. Perhaps the distance necessary to apply this effect is substantial, but heck we're already going to geostationary, right?
And from a message further up:
The base could easily be placed on a barge in the middle of the ocean. In fact, that's just about ideal; it can move around relatively easily...
Well, you've basically got a pendulum that is 35,000+ Km long. That's going to be a pretty long period to make it do anything, I bet. Maybe easier would be to just detach it from your barge and roll it up into the sky at the balance point if you need to get out of the way of some terrestrial event.
-- "Oh. This guy again."
Yes, metals are bad. Water (source of hydrogen = protons) is the best shield, or so say Those Who Know Such Things.
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
I read Arthur C. Clarke's stuff when I was young (and no, this was not last week!). As well as Heinlein, Asimov, PJ Farmer, and many, many others. I was enthralled and entranced. The spirit of exploration has been deep seated within me since those days.
When I read the comments for this topic, I am struck by:
1) The number of people who share my love of exploration, discovery, and maybe a chance to save the species. This number is woefully small.
2) The number of people who have no sense of awe, excitement of discovery, no desire to look past their own immediate universe. people to whom the horizon marks the end of the universe. This is, then as now, too many.
If we (the rest of us) listen to the nay-sayers, we will still be sitting, fighting over the girls and land, on this wore-out world, when the sun goes nova. And that will be sad.
I'm not trying to insult anybody. And my conversation style, grammer and spelling, tend to leave a lot to be desired.
- X/Y -
The question would be, what is the effect of an impact on a ribbon, and it's detachment from it's anchors, going to do for any load going up or down that ribbon? My feeling is that it's not particularly healthy to be riding that ribbon, unless your elevator car is actually able to transfer to another ribbon even after it's anchors have detached. Might be a good idea to not be under any likely fall paths from a given spot on a strand either.
From the perspective of over-engineering the project, I would suspect that what you would want to do is have elevators using some combination of 3 or more ribbons, oriented in different directions, with the ability of the load to be handled on any single strand, but with the expectation that at any given time the loss of no more than one strand would be acceptable, and passengers would be expected to evacuate (with appropriate suits and chutes) and cargo loads would be "aimed" at uninhabited areas. (Agreed that may be "interesting" at certain altitudes....)
You never know...
It's behind a paywall. No, I won't read it before commenting on it. It's not worth the money or time. I presume it says it's possible but not practical, unless done by a government or world consortium. The return is too long and too risky.
Learn to love Alaska
The number of people talking about the issue of balancing the elevator makes me think perhaps I have misunderstood.
Different emphasis depending on what you are trying to explain. The system is almost in balance. The amount of tension at the ground is completely arbitrary. So when discussing payload movement, it's the "almost" that's important. When explaining how the concept works to someone (Chas) who thinks it's a billion-tonne "tower" pressing on the ground, it's the "balance" that's is emphasised to them.
Want to put a heavy load on the ribbon bottom? Send a signal to have the counterweight climb further up
That would work, but IMO if the ribbon is capable of handling the force from the climber+payload, then why not use a base-anchor heavy enough to handle the tension when there isn't a climber? Ie, leave the system in permanent tension.
For early versions (small ribbon, no GEO station), apparently they want to have winches on Earth feed out excess ribbon to increase tension, or pull it back to reduce it. The idea is to keep the tension on the ground-station roughly constant, and fairly light. This is because they assume the first version will be at the very edge of possible, and kept as small and light as possible in order to be able to build it at all. For example, the counterweight would be the rocket-stage and drum from the original deployment. You start in GEO and let out the ribbon, the drum naturally moves outwards to balance the descending arm. [Rather than the usual image of a central deployment at GEO feeding out two arms in balance.]
Re: wobbling versus retracting.
It would also take a long time to winch up and redeploy it each time, during which the the system is useless. Given the number of satellites (especially in LEO) and orbital debris that it would have to dodge out of the way of, it wouldn't spend enough time in operation to justify its existence. During a ship-driven "wobble", otoh, it can still be launching and retrieving climbers.
Science is all about firing a drunk pig out of a cannon just to see what happens.
Comments from the peanut gallery are unwelcome, especially when the fucking peanut gallery doesn't even know if they're right or wrong. Tread lightly, and wise up.
I note that you posted anonymously so that your hypocrisy would not be attached to your name. Why don't you tread lightly, and fuck off?
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
How the hell do they propose to keep satellites and whatever other space junk there is from hitting the space "cable"? I've never seen this addressed.
Besides all the innumerable other problems with space elevators, at the end of the day they don't actually get you into orbit unless you go right up to the top - a 50,000 km (ish) journey. At 200 Km/h 50,000 km will take 10 days for each trip up and that will also severely limit the elevators total mass capability. Anyway the problem here is that to reach a stable orbit at lower altitudes requires huge sideways speeds, space elevators cant provide any of that sideways motion.
Closely related but even more serious is that due to conservation of momentum the vertical upward translation of a space elevator car creates a negative (backwards) lateral force on the elevator cable. (ribbon string?) This creates at two really big problems. Firstly the sideways force adds extra dynamic tension creating problems for stability with the car and increasing the overall load so requiring a stronger cable. Secondly and more importantly the sideways force pushes the whole structure backwards tending to destabilise its orbit and actually push it out of orbit. - And the great irony here is that the only solution ends up being a rocket attached to the counterweight - one almost equal in power to the rocket that would be needed to deliver the cargo to geosynchronous orbit directly from the ground. No elevators are almost COMPLETELY useless.
As for orbital rings, yes some of the technology looks formidable but they are at least easier than elevators and should have much better ability to deliver heavy cargos to Earth orbit - ie they might actually work. There are plenty of other ideas that are probably even better - like the idea of the Loftstrom loop https://en.wikipedia.org/wiki/... .
However at the end of the day the best solution is simply bigger and better rockets - say using gas core closed cycle nuclear rocket engines. A ship using these could get to orbit with one stage, deliver heavy cargo's then use retro braking to return to Earth - making it fully reusable, far cheaper, far safer, and vastly more capable than current tech. -
https://en.wikipedia.org/wiki/...
https://en.wikipedia.org/wiki/...
When you look at the kinds of rockets needed to get (anything substantial) out to the other planets or to most asteroids anything other than nuclear rockets is simply a joke - getting into Earth orbit is the easy bit.
Below the speed of light Special Relativity is one of the most accurate theories in physics - above the speed of light..