Space Elevator May Become Reality

mojotek writes: "The NASA Institute for Advanced Concepts has a study(15Mb pdf) about the feasibility of a "Space Elevator" comprised of a 22,000 mile long cable built out of carbon nanotubes. In theory, it would be able to carry loads of 20 tons to space without using a single rocket engine. Sounded way too sci-fi for my taste at first, but this article at TechTV actually helped fill in the holes."

Comments

TV?

[oregon]

We're getting science news from the TV now are we?
Heaven help us!

[ding] 345,234th floor...

[GCP]

vacuum gloves, radiation belts, high-velocity hardware...

Re:[ding] 345,234th floor...

[Anonymous Coward]

Hmm, wouldn't that be "2nd floor".

Re:[ding] 345,234th floor...

[Anonymous Coward]

Is carbon nanotube a good conductor of electricity ?

If the answer is yes, then you have the world's tallest lightning rod. Sure hate to have billion of amps vapourizing the magic rope.

Re:[ding] 345,234th floor...

[buckrogers]

It _is_ a conductor... And it will be a 22,000 mile long generator that is powered by moving through the suns magnetic field. It should generate a lot of power. :)

I think that there are going to be a lot of issues with building a structure this big, and people will die and there will be disasters, but in the end everything will work out and riding a space elevator into space will be about as exciting as riding an elevator to the top of a tall building, or driving over a bridge.

Until space colonies are self supporting there will be a need for massive resupply from the ground to support even a few people and rockets make the shipping costs for these supplies prohibatively expensive.

The ability to ship people and supplies up in an elevator will make it economical for companies to start up their own space stations. It will make it fesible for small groups of wealthy people to start up their own space colonies. Space hotels will be able to make money. It will also make it cost effective to manufacture items in space and send them in the downward travelling containers.

Re:[ding] 345,234th floor...

[Anonymous Coward]

Why is this "offtopic"? MODERATORS SUCK! If anything, it's +1 Funny.

Meet George Jetson!

[Anonymous Coward]

Not to dismiss the elevator out of hand, but wouldn't research into efficient space vehicle propulsion yield better long term results? While the engineering feat of building an elevator would certainly yield advances in science and technology, the elevator's limit would be its height. Non-tethered vehicles have no such limit.

Re:Meet George Jetson!

[RetroGeek]

Most of the effort of getting around, is getting UP. Once you get up its cheap to move around.

Also, you can transfer fuel up by the tanker load.

Re:Meet George Jetson!

[mmontour]

Not to dismiss the elevator out of hand, but wouldn't research into efficient space vehicle propulsion yield better long term results?

Not really, because the "efficient" propulsion systems probably won't be able to lift a rocket off the ground. E.g. the DS-1 ion engine, high efficiency but only about 0.1N of thrust - or nuclear engines that would be too dirty to run in the biosphere, but would work fine in interplanetary space.

If a space elevator could be built, the cost of lifting payloads into space could drop dramatically, and that would create a lot more incentive for companies to develop these efficient space-only engines.

Re:Meet George Jetson!

[coyote-san]

Robert Heinlein (iirc) once commented that low earth orbit (LEO) is halfway to anywhere, and that's even more true of geosynchronous orbit (GEO). It takes a *lot* of fuel to get out of the earth's gravity well, and getting to GEO for the cost of electricity (provided by in-space solar cells!) would profoundly change everything.

If you want to leave earth orbit, you take a second elevator that runs from geostationary station out to the anchor and let go. Depending on the length of this section, you'll have a ballistic launch to anywhere else in the solar system. Well, you'll need a modest amount of fuel unless the plane of earth's orbit is exactly aligned with your destination, but you'll need orders of magnitude less fuel than you need today, and you can get that fuel up to the launch point for the cost of electricity alone.

If you want to leave the solar system, you let go of the upper elevator and hop to the center of a freespinning tether, then inch outward. When you reach the end of this tether, you could be traveling at a few percent of c. You'll be at Alpha Centari within 100 years... and a second tether there could capture you and slow you down. That's too long for passenger traffic, but brief enough that interstellar colonization is a realistic possibility by the end of the millennium.

So all things considered, I think research into carbon nanotube space elevators has better long term potential than anything rocket propulsion technology. Even antimatter propulsion, excluding some unknown mechanism to mass-produce anti-atoms.

Re:Meet George Jetson!

[RedWizzard]

Spacehooks (elevators etc) are the most efficient way of getting into orbit by far and that's the trickiest part of space travel. Once you're in orbit it's fairly cheap to get elsewhere. The trouble with an elevator is not the efficiency it's the engineering requirements and disaster scenarios.

Re:Meet George Jetson!

[uchian]

I can take a good reason to build an elevator straight out of a book called 'science of the Discworld'. Basically, the argument goes that if you have an elevator into space, then you can reuse energy, whilst if you have a propulsion system then you cannot.

How does this work? Simple. After you have successfully sent so much stuff into orbit, your going to start to want to bring things back down, whether this be from mining other planets or simply getting the astronaughts back to their parents. Normally, we waste all of the energy on reentry because we don't use it for anything. With an elevator, the energy being exerted by gravity on the way down can be used to balance out the gravity being used to get other stuff up. Hence, you don't need as much energy overall to get stuff into orbit.

And as others have already stated, once out of the earth's gravity, you don't need that much energy to move around at all...

Re:Meet George Jetson!

[WolfWithoutAClause]

Efficiency is irrelevant really. The problem is expense. Rockets are efficient enough- it works out at about 14 lbs of fuel per pound of payload. Sounds a lot till you realise that that is about $14 per lb of payload cost. The rest is building and maintaining the rocket and the launch site, mission control etc. etc.

Research into cheaper rockets goes on. The cheapest rocket at the moment costs about $2500/lb (Proton rocket); but they make a good % profit per launch, I can tell you.

Re:Meet George Jetson!

[badboy_tw2002]

Actually, it burnt up, so no retrieval necessary

Re:Meet George Jetson!

[matthewmichaelagee]

I studied this concept as part of a commercial space development group back when I was in college. It's quite compelling.

There're two significant challenges in implementation, though.

The fundamental flaw in the concept lies in conservation of rotational inertia. Think about a spinning ice skater - as she draws her arms in, she spins much faster. The opposite is also true - as a rotating mass extends from its center, its rate of rotation decreases.

The space elevator rotates at a constant geosynchronous rate, but as its payload is raised along that axis, the difference between its linear inertia at the surface of the earth and its linear inertia around the circumference at geosynch altitude (or any significant altitude along that axis) is absorbed by the elevator's structure.

Unless the payload applies some sort of thrust perpendicular to the axis of the elevator, that difference in inertia only works to pull the whole system back down to earth. Effectively, the amount of energy you'd have to put into the system to keep it up would equal the thrust expended to send the payload into orbit by conventional means.

Then there's the whole issue of vibrational harmonics. Accumulated shocks from winds, payloads, and even space dust would propagate up and down the string (any human structure of that incredible length would effectively be a string in tension) and create severe vibration problems. That'd take some *seriously* epic engineering to dampen.

NASA has done some experiments with tethered satellites which address the vibration issues (as well as accumulated electric charge from atmospheric drag), but they were intended more for spinning-wheel satellite applications than for space elevators.

It's a really cool idea that unfortunately is a something-for-nothing scheme. If there were some kind of cool electric thruster system which didn't rely on reaction mass, it'd be feasable, but then we're straying into Area-51 technology. ;)

Re:Meet George Jetson!

[arsaspe]

The benifit of the elevator is that on the way down, you can convert all that gravitational potential energy back into electricity, so even though it takes a lot of energy to lift the elevator, you get most of it back.

Re:Meet George Jetson!

[ptrourke]

Nope. For surface-to-orbit, rocket propusion is no more than a short-term solution. And remember, the "elevator" doesn't just go up to geosynchronous orbit; its anchor is in geosynchronous orbit - the top of the elevator is even further out (the elevator's center of gravity must be in geosynchronous orbit).

This thing would make travel to the moon something you could afford for the weekend. Rockets will never manage that.

Re:Meet George Jetson!

[cb0y]

but an anti-Gravity pulse type elctromagnetic system would be much better , aka like UFOs

Re:Meet George Jetson!

[Pig Hogger]

...
Basically, the argument goes that if you have an elevator into space, then you can reuse energy, whilst if you have a propulsion system then you cannot. ...
Normally, we waste all of the energy on reentry because we don't use it for anything. With an elevator, the energy being exerted by gravity on the way down can be used to balance out the gravity being used to get other stuff up. Hence, you don't need as much energy overall to get stuff into orbit.

More than 50 years ago, the Virginian Railroad used electric trains with regenerative braking. Heavy coal drags trundling down the mountains were generating enough power to enable the empties to go up the mountain without having to kick-in the powerhouses.

It's amazing to see "modern" science re-inventing the hot technology railroads invented 50-100 years ago...

Re:Meet George Jetson!

[coyote-san]

Another Robert Heinlein observation, this time from _Friday_. The issue is never energy, it's how the energy is stored.

The energy required to lift a ton of cargo to GEO is the same regardless of the mechanism used (and disregarding any power you can extract from descending cargo). But there's a tremendous practical difference in that energy coming down superconducting power lines from a solar array out by the ballast or if it comes from liquified oxygen and hydrogen stored in disposable tanks. It makes a tremendous difference whether you the energy is coming via an existing infrastructure (e.g., power cables) or if if you have to waste some fuel to lift the fuel you need now.

I don't know what the current factors are, but I wouldn't be surprised if putting something into GEO requires 99 kgs of fuel for every kg of payload. A beanstalk would get you there with no "waste" other than the reusable elevator car.

As for harmonics caused by weather... I think this has been dismissed. This cable is under millions of tons of tension, and has a cross section of well under a meter when it's in the atmosphere. The load bearing core will be surrounded by a much larger infrastructure for the elevator, power cables, etc., but since it's not load bearing it can be dampened -- and is still on the order of a few meters. With such a small profile and high tension you aren't going to see much energy transferred from weather systems into the cable. (Earthquakes are another matter.)

And the conservation of momentum issues are real, but I (and others) are skipping many of the fine details for overall clarity.

Re:Meet George Jetson!

[Anonymous Coward]

hey fuckwit. star trek is not real. you just used a "fact" from a FICTIONAL FUCKING TV PROGRAM

Re:Meet George Jetson!

[3141]

Really?

Re:Meet George Jetson!

[riverat544]

Any linear intertia lost by the teather from hauling mass into space will be canceled by the intertia gained from coming down (if they are equal of course). Once we get established in space it will be easier to get most raw materials from out there and what will be going up will be mostly people. If we start moving some polluting heavy industry (like steel production) to space we will probably be hauling more mass down than up.

Re:Meet George Jetson!

[Anonymous Coward]

Didn't Clarke have a great deal to do as a proponent of the Space Elevator. I know Heinlein used it as a plot device, but it was Clarke who recently wrote in to Scientific American arguing about carbon nanotubes.

Re:Meet George Jetson!

[Phil-14]

Of course, there's still the question of how much
stuff you'll have to boost to orbit in order to
build the cable. The cable is capable of solving
space transportation problems only after we're
three or so orders of magnitude better at it than
we are now. And therefore not of interest.

Re:Meet George Jetson!

[Anonymous Coward]

There were a few great books about this (sci-fi) Red Mars, Green Mars, and Blue Mars. They solved the problems by using elevators carts going up and down at the same time to balance it out. They also had segements. You'd go up a mile and stop, get on another cart for another mile, etc. They used a large asteroid to tether the cable in space, and they bottom of the cable hovered over the ground. (eliminating the earthquake problem)

Of course the elevator was knocked out by rebels. A very real danger if something that delicate were to be built here. (Imagine a massive carbo nnanotube cable falling and wrapping it self around the equator!)

Re:Meet George Jetson!

[jmccay]

One important question has yet to be answered. How will having some rising from the Earth effect the spin of the Earth and it's orbit on both a short term and long term effect? I would like that studied before we consider building on of these things. For once I would like to have the results up front!

Re:Meet George Jetson!

[Anonymous Coward]

No, because with any rocket you have to lift your own fuel. With a space elevator (or other ideas like mass drivers) you only have to lift your payload. The space elevator has the potential additional benefit that you can use regenerative braking on the trip back down, or on the trip past geosynchronous orbit, and recover some of the energy.

I wonder if trips to space would be cheep?

[Indes]

since there could be an elevator, Would we be able to get rides up there to have some fun being weightless? or would that be one of those million dollar price tag things.

Re:I wonder if trips to space would be cheep?

[Anonymous Coward]

optimistic (but plausible) estimates put it around $10 per kg.

So your average adult could probably go up for $700, assuming it didn't turn into a tourist trap (multiply by 100).

Re:I wonder if trips to space would be cheep?

[s20451]

To transport you (70 kg) up to an altitude of 200 km would take roughly 140,000 kilojoules of energy (you do the math ... first year physics stuff). However, they can't just lift you, they also have to lift a vehicle containing you. Say the vehicle weighs 500 kg for every person it can carry -- this would take rougly 1,000,000 kilojoules. If they do this electrically (which is one of the more expensive forms of energy), at 100% efficiency it would eat up roughly 300 kWh of energy. At 0.30/kWh (say), that's roughly $100.

Of course, a clever engineer would realize that every vehicle going up eventually goes down ... so the vehicle on the way down could be used as a generator, feeding power to the load of a vehicle going up. Equally obviously, we're not considering the amortization of the construction cost, which would be monumental.

Re:I wonder if trips to space would be cheep?

[spectral]

I'm probably mistaken, but at least someone will correct my mistakes I'm sure. I believe that if you were to stand at a place that's tethered (so you were rotating at the same rate as the earth itself), you wouldn't feel weightless (you would feel slightly less force due to gravity, but not weightless.) to be weightless, you'd have to be orbiting the earth (like the space shuttles do), so as you fall towards the earth, your orbital velocity moves you tangential to the earth's radius just the right amount that you go around in a circle, constantly falling but never getting closer. To notice the difference, figure it takes a space shuttle what, 90 minutes to circle the earth? The platform you're standing on never will. (it'll always be above the same spot, assuming that it's rigid (which wouldnt make much sense, but whatever, the assumption simplifies it a bit.))

Re:I wonder if trips to space would be cheep?

[s20451]

Whoops, the math isn't as simple as I thought. I assumed that the force of gravity is the same from the surface of Earth up to 200 km ... to calculate it exactly you would have to integrate. Any other errors are left as an exercise for the reader ... :-)

Re:I wonder if trips to space would be cheep?

[jjeffers]

I'll confess, I haven't read the 15MB PDF ... but wouldn't the device you are describing be very similar to rail gun? How are it's passengers going to withstand those sort of G forces?

It would be pretty damn cool to smell the corona discharge after one of those things fired :-)

Re:I wonder if trips to space would be cheep?

[coyote-san]

A one-way trip would take about 5 days or so, and your weight would gradually decrease from normal to zero as you reached the geostationary station.

You would not stop at the 200km height, no more than you get off a ski lift at the first tower.

At the 200km height another poster mentioned - you would have a hard time finding any change in your weight. Instead of being something like 6400 km from the center of the earth you're 6600 km away. That's enough for about a 6% change - less than the annual weight change by many people on yo-yo diets.

Re:I wonder if trips to space would be cheep?

[goonies]

and you could have the longest free fall in skydiving history ever ;)

Re:I wonder if trips to space would be cheep?

[TheAlmightyQ]

Are you familier with geosync orbit? The space shuttle is in low earth orbit and thus has to complete an orbit in approx. 90mins in order to "fall" around the earth. But if you get up to about 36,000k (I think thats right) your orbital time would be exactly 1 day. In other words you would be in free fall around the earth, but the ground below you would be rotating with you.

Look at the moon for example, it is so high that it takes ~30 earth days to orbit.

Re:I wonder if trips to space would be cheep?

[dodald]

Gravity has nothing to do with the speed of rotation. Its not intuitive, and its putting my physics circuits into overload :). We have geosynchronous satellites. If you are orbiting at the same speed as the rotation of the earth, you are still orbiting. More Info.

Re:I wonder if trips to space would be cheep?

[inburito]

It would totally depend on how far from the earth you were. If you are exactly on a geosyncronous orbit then you would definetly feel weightless no matter what. I'd assume that such a space elevator would be "anchored" on a geosyncronous orbit since otherwise it would drift and probably break the whole assembly.

If you are below the geosyncronous orbit you'd feel slight gravitational pull and above it you'd feel the effect of sentripetal force of the elevator keeping you attached to the earth - you'd actually be standing on the roof then.

Shuttles are normally orbiting the earth at a speed and height (mv^2/r=GmM/r^2) where earths pull is just enough to keep them on a steady circular course around earth - so they are technically free falling but never approaching earth. Geosyncronous orbit is just a special case where you're going at the same angular velocity as earth.

Re:I wonder if trips to space would be cheep?

[Sylver Dragon]

I'll confess, I haven't read the 15MB PDF ... but wouldn't the device you are describing be very similar to rail gun? How are it's passengers going to withstand those sort of G forces?

Actually, you wouldn't have to worry about the forces involved bothering the passengers any more than you do on a normal roller coster. While escape velocity sits around 11 Km/s, that is for a ballistic launch. The kind where all of the acceleration happens within a very short time. This thing will be accelerating much slower. Since it can continue to exert a force of the vehcile.
Simply put, if you can make a vehicle that has a force capable of continuously producing ~9.8m/s/s acceleration upwards, it will continue at whatever speed it currently has upwards, with no acceleration or decelleration. Though as you get higher you would, technically, accelerate using this same force. As such, the elevator could accelerate at a slow rate, and probably never acheive 11Km/s, but still hit geosynchronous orbit.

Re:I wonder if trips to space would be cheep?

[Anonymous Coward]

It's me again posting as Anonymous as not to Karma Whore :) The cable would be end about 22,000 miles up which is the point where it would be in geosynchronous orbit. So when you got to the end of the cable you would in fact be weightless.

Re:I wonder if trips to space would be cheep?

[uberdave]

The difference in the gravitational force at surface+200km is relatively negligable.

Re (Radius of Earth)=6378136 m
Ro (Radius 200km up)=6578136
Fe,Fo are force of gravity on earth, and 200km up.
Fe=G*M1*M2/Re^2
Fo=G*M1*M2/Ro^2

Fo/Fe=(G*M1*M2/Ro^2)/(G*M1*M2/Re^2)

or

Fo/Fe=Re^2/Ro^2=6378136^2/6578136^2

Fo is about 94% of Fe, or about 9.2m/s^2

Re:I wonder if trips to space would be cheep?

[Kymermosst]

Would you really be weightless, or would the centripital force created by the rotation of the Earth (and hence, transferred to the cable) be enough to keep you pinned to the cieling when you get to the top?

Re:I wonder if trips to space would be cheep?

[WolfWithoutAClause]

30c per kWh is a lot. I usually pay about 10c. Plus, access to space would give very cheap access to 24x7 solar energy, which would further reduce energy costs.

Re:I wonder if trips to space would be cheep?

[Anonymous Coward]

The gravitational potential energy of an object wrt a planetary object is -Gm1m2/r, where G is a small constant I can't quite remember. (Yes, the gravitational potential energy is negative)

At the Earth's surface, this would be equal to -6.25*10^7 J/kg * m.

200 km up, it would be -6.06*10^7 J/kg * m

It would take 1.9 MJ (=0.53 kWh) to lift a 1 kg mass 200 km from the surface. Subtract about 5% from all of your results and it will be correct.

Re:I wonder if trips to space would be cheep?

[Uzull]

Beside of the regain of energy by the vehicle going down, the lift would produce electricity when idle ! The lift, out of carbon nanotubes would be conductive, and crosses the magnetic field of the Earth, and therefore inductive electricity would be produced. A experiment was done several years ago on a Space Shuttle. At that time there problem with the cable widing system, and the experiment had to be abandoned.

Re:I wonder if trips to space would be cheep?

[Anonymous Coward]

Since the end point would be in geosynchronous orbit, wouldn't it spin with the magnetic field rather than relative to it?

Wonka-Vator?

[saarbruck]

I didn't see anything in the .PDF about armoring the elevator against Vermicious Knids. It's just that sort of oversight that will be their undoing. Mark my words. Or Roald Dahl's.

Re:Wonka-Vator?

[JediTrainer]

Funny... they didn't mention 'sky hooks' either. You'd think they could keep their terminology straight.

Re:Wonka-Vator?

[Jonny Ringo]

I don't know what scares me more the 15Mb pdf file or the elevator to outer space.

Re:Wonka-Vator?

[Anonymous Coward]

That's an interesting children's book. Here are some others you might enjoy.

Re:Wonka-Vator?

[Anonymous Coward]

what the heck is a "sky-hook" anyway?

Last time this came up on /.

[Bill Currie]

I did the math and worked out that if you gibbed the cable (say 1m chunks), you'ld wind up with something like 25-30 thousand km (I don't remember the exact figure) of the cable crashing down on earth and the rest flying off into space. However, I didn't figure out if the cable would fall east or west (west would be better, but I think it's less likely). Either way, that's a little over 1/2 way around the world and while the only land mass likely to be hit is Africa, I don't imagine the impact with the water would be particularly fun (possible tsunami).

Re:Last time this came up on /.

[geekoid]

actually it would wrap aroung the equator, fall west word, and wrap around the earth.
The tram is "mega-tsuanmi". No I didn't make that up.

Re:Last time this came up on /.

[jjeffers]

Why not have a self destruct mechanism ... so if it started to fall high explosive would blow it into more manageable sections. Possibly only eliminating Equador :-)

Re:Last time this came up on /.

[Amazing Quantum Man]

You'd have to nail it high up for there to be any "damage". If you sever it at the bottom, you wind up with a free floating base that you can reattach. The point is that the entire elevator is in stable geosync orbit (actually, it's CM is in geosync), so that if the base is snapped, it doesn't fall.

Re:Last time this came up on /.

[xah]

In reality, we have no way of knowing what would happen, beyond guessing.

If all we needed was a "hanging" beanstalk, however, why attach it to the Earth at all? Just let it blow around in the wind.

Re:Last time this came up on /.

[goonies]

Actually i think the CM would have to be higher than geosync so that you have some force on the cable (CM trying to leave this orbit) plus to carry the 20 tons of payload...
(yes, i didn't read the .pdf as well - tell me if i'm wrong)

Re:Last time this came up on /.

[Anonymous Coward]

yes distruction disorder and chaos. see the series red green blue mars by kim stanely robinson for some accurate projections of the devatation. and no it wouldn't be fun. the tsunami would be pretty much for sure, and all along the length. I think analysis of the force of that much mass falling such a distance would make your hari stand on end. the end would probably crack like a whip and strike with enough force to seperate a good quantity of hydrogen and oxygen from the ocean. and I think the tip would be flaming as it hit so ignition would occur. lets see the temperatures involved would be phenominal(extreemly durable mass falling from orbit add rotational velocity and whip effects), and nanotubes have that weird super fast heat transfer property so the whole thing would be blazing like the inside of a fusion reactor. I haven't ever put pencil to paper but I'd say odds are you could kill every person on earth with one of these things. think about kicking up all of the sand in the sahara, vaporizing a good quantity of the liquid water on the planet and sending shoockwaves to as powerful as the most powerful earthquakes ever.
good thing we don't know how to manufacture nanotubes in quantities to make such a project possible ;-)

Re:Last time this came up on /.

[RayBender]

Wait - if you cut the cable at its base, wouldn't it actually lift and fly into space? Only the part between the ground and the break in the cable would fall down. So if some yutz flew an airliner into the base of the cable you'd have to reattach it - not pick up 36,000 km of it off the surface of the planet.

Of course, if you cut it higher up, or cut into a bunch of pieces then some of them would come crashing down...

Either way - the technology to build this thing is so outlandish that we shouldn't hold our collective breath.

Re:Last time this came up on /.

[TheAlmightyQ]

You have to remember that while this structure would be incredibly long, it wouldn't necessarly be that massive.

Look at the world trade centers for example, in human terms those were unbelievably massive objects, and when they crashed they didn't exacly cause an earthquake.

So while a space elevator crashing to earth might cause a lot of damage where it falls, it's not going to trigger any large scale disasters

Re:Last time this came up on /.

[sheetsda]

How difficult would it be to cause such a failure? The article mentions the thing might be a terrorist target, and also mentions these carbon nanotubules are around 30 times as strong as kevlar. Bomb suits I've heard are around 10 layers of kevlar(I don't know the thinkness of those layers), so I'd think it'd take something on the order of an atomic bomb to cause a critical failure if you left reasonably excess strength in the cable.

Re:Last time this came up on /.

[The Living Fractal]

Ugh.

You're retarded.

I can't believe how stupid some of these /. people are...

Re:Last time this came up on /.

[Danse]

If all we needed was a "hanging" beanstalk, however, why attach it to the Earth at all? Just let it blow around in the wind.

Probably because you'd want it to be stable when you're sending up 20 tons worth of space gizmos.

Re:Last time this came up on /.

[cpt kangarooski]

It's pretty easy to figure out what happens. You get some physics grad students, give 'em beer and pizza, and let them work out the math.

"Guess," bah.

Re:Last time this came up on /.

[Anonymous Coward]

"Where's that dang spacehook? It was right here a minute ago!"

"I was downtown and one of those fuckin' spacehooks smacked me upside the head! I gave that fucker a good tug."

"Giant spacehook leaves trail of destruction through suburbs of Austin; film at 11."

Re:Last time this came up on /.

[Brit Aviator]

Speaking as a pilot, I think it's a bad idea. Just what I need, another damned thing to fly into. There I am, happily cruising along in my airliner and suddenly *wham!* my aircraft gets cut in twain. Knowing the damned FAA, it would probably be "pilot error" too. Hmph.

Re:Last time this came up on /.

[Anonymous Coward]

I think it would fall eastward, given the rotation of the earth (eastward) and the fact that the velocity in space would be much greater than that at the earth

Re:Last time this came up on /.

[WolfWithoutAClause]

No, this is covered in the paper. The tether would melt and reenter harmlessly above a 100km or so. Below that it would survive, but its a pretty predictable landing zone; and one of the cleverer ideas he had is building it in the sea where it won't hurt anyone.

Re:Last time this came up on /.

[Bill Currie]

Which is exactly what I did, minus the physics grad, bearn and pizza (actually, if it was a thrusday, there was pizza involved) plus electrical engineering degree and intense interest in orbital mechanics (ie, while I don't have a physics degree, I understand the math involved in orbits).

Re:Last time this came up on /.

[Bill Currie]

for one, cut, you are correct. I did MILLIONS of cuts. One every meter.

Re:Last time this came up on /.

[Bill Currie]

I honestly don't think such a critical failure is possible without the use of a rediculous number of bombs.

Re:Last time this came up on /.

[Bill Currie]

Ah, but it would be piolot error. If you can't see the nagivation hazard lights along the thing, or if you ignore the posted flight paths in the area, that's your fault.

Re:Last time this came up on /.

[Pig Hogger]

You'd have to nail it high up for there to be any "damage". If you sever it at the bottom, you wind up with a free floating base that you can reattach. The point is that the entire elevator is in stable geosync orbit (actually, it's CM is in geosync), so that if the base is snapped, it doesn't fall.

In Clarke's Fountains of paradise, the beanstalk is actually built down from a heavy base in geostationary orbit.

Re:Last time this came up on /.

[Pig Hogger]

...
and one of the cleverer ideas he had is building it in the sea where it won't hurt anyone.

How about the fish????

Re:Last time this came up on /.

[ZxCv]

Heh, no kidding. I sure as hell wouldn't want this guy piloting the plane I'm flying on.

Re:Last time this came up on /.

[PhuCknuT]

Somehow i don't think the cable will be water soluble. It would be trivial to pick up the remaining piece that landed in the water, just grab and end and reel it in.

Re:Last time this came up on /.

[dossen]

> Perl - $Just @when->$you ${thought} s/yn/tax &couldn\'t %get $worse;
would s/yn/tax/ not be the proper syntax? Don't make it worse than it is.

@a=(Lbzjoftt,Inqbujfodf,
Hvcsjt); $b="Lbssz Wbmm"
;$b =~ y/b-z/a-z/ ; $c =
" Tif ". @a ." hsfbu wj"
."suvft pg b qsphsbnnfs"
. ":\n";$c =~y/b-y/a-z/;
print"\n\n$c ";for($i=0;
$i<@a; $i++) { $a[$i] =~
y/b-y/a-z/;if($a[$i]eq$a
[-1]){print"and $a[$i]."
;}else{ print"$a[$i], ";
}}print"\n\t\t--$b\n\n";

Re:Last time this came up on /.

[WolfWithoutAClause]

Eastward in fact. The tether is rotating west to east with the earth, and the higher up bits are going faster, until at geosynchronous orbit the centrifugal force matches the gravity at that point.

If the tether snaps, the pieces drop, and keep their horizontal speed- so the tether pieces go east relative to the ground. (Actually, the bits speed up a little due to conservation of angular momentum as they fall, but not a lot.)

Re:Last time this came up on /.

[An Onerous Coward]

Hey, if they didn't read the memo, it's not our fault. They were given proper warning.

Re:Last time this came up on /.

[An Onerous Coward]

I think the purpose of building the base at sea is so that it can "drift" around somewhat. Building at sea doesn't provide any additional safety, because the cable is very long, and is going to "wrap" rather than fall straight down.

Look at me. One reading of "Red Mars" and I think I'm some sort of expert or something.

I'm not so sure about the "melting harmlessly" thing. Even if that's true (and it could be made more likely by lining the upper portion of the cable with explosives :), there's still a nuclear lot of energy being released. I wonder if it would end up frying every computer within a thousand miles of the Equator.

Re:Last time this came up on /.

[WolfWithoutAClause]

Mars and earth are completely different situations. To a pretty good approximation- Mars doesn't HAVE an atmosphere- it's only 1% of a standard earth atmosphere. Earth's atmosphere has the force of 15 bags of sugar on each square inch of your body. On Mars it would be more like 1/6 of a bag.

Above a certain altitude the reentry speeds are climbing up into the 1km/s range, that's 3600km/hour. What chance has a bit of epoxy and some thread got of reentering intact? None. Nada. Zip.

Sure, there's a lot of energy, but it's spread over an enormous distance; and that energy is going to vapourise that tether real good. You really don't need to sweat this one.

Re:Last time this came up on /.

[Brit Aviator]

Sure, now you expect me to watch where I'm going! Soon you'll actually expect me to get you to your destination on time. Will the unreasonable demands made on aviators never cease?

Re:Last time this came up on /.

[elvum]

I wonder if it would end up frying every computer within a thousand miles of the Equator.

No, because a big release of thermal energy in the upper atmosphere is not the same thing a nuclear explosion in low earth orbit (although the latter coincidentally causes the former as well as an EMP).

Re:Last time this came up on /.

[big_hairy_mama]

I Am Not A Carbon Nanotube Scientist, but I think that the tubes strength comes when they are streched (tension), but not necessarily when there are other forces. So it might be pretty easy to snip the tubes when cut from the side.

Rotational energy

[jbeams]

wouldn't sending large amounts of mass up via a space elevator have a small but measurable effect on earth's rotation? Impact?

Re:Rotational energy

[oregon]

We're already slowing down because of the moon's tidal effects - the length of a day is increasing by 1.7 milliseconds per century.

Can sending a few tons of stuff into orbit have a bigger effect than the moon?

Re:Rotational energy

[Anonymous Coward]

Another question that comes to mind is isn't raising a large mass up the cable going to slow down the orbiting sattelite?

Re:Rotational energy

[hazem]

I think the amount we send out is probably insignificant compared to the amount of dust and junk that rains down on us from space.

Does anyone know how much that is anyway?

Re:Rotational energy

[Anonymous Coward]

I regret to inform you that I have actually looked into this. Yes, I have no life. I had this hair-brained idea that the mass the debris (Forgive me this approximation, I can hit it w/i an order of magnitude...~10-100 million tons per day, and closer to the high end of that.) added to the Earth may have altered the gravity during the evolution of life and therefore affected the selection of species at various points. I ran the calculations back to the extiction of the dinosaurs, (Note to self, _never_ get rid of notes.) and the change was infintesimally small. I ran it back 4.1 billion years, (One of many guesses at the age of the Earth, but a popular one.) Still small enough to be unimportant. HTH

Re:Rotational energy

[Anonymous Coward]

So, we should be safe in assuming the amount of crap coming down far outweighs (out-masses, that is) the crap we send back up. So, we really shouldn't worry about how much stuff we put up in orbit and beyond (at least as far as it affects the orbit and rotation of the earth).

On another thought, theoretically, taking the more dense oil and coal out of the ground, then burning it and putting it up in the atmosphere should also have an affect that would slow the earth down. This is like the skater - taking mass out from closer to the middle and sending it outward.

But, again, it probably has no measurable effect.

Wasn't this already on /.?

[The Rabid Rabbit]

http://slashdot.org/article.pl?sid=01/12/19/056214 &mode=thread

Re:Wasn't this already on /.?

[J'raxis]

Last time the paper was 8MB, now its 15MB. Next time it should be at least 30MB. NASA putting their funds to good work, I see.

see what happens when one of these break...

[Zurk]

as shown in full gory detail here. note the counterweight too.

Re:see what happens when one of these break...

[wurp]

I'm sure that it would do an incredible amount of damage (I haven't done any calculations to see how much) but the counterweight would fly out into space. To function as a counterweight it would have to have a net force (centripetal + gravity) outwards, away from the earth.

Re:see what happens when one of these break...

[PhuCknuT]

That is so unrealistic it's not even funny. The cable will be at most a few meters wide at it's widest point. And most of it would burn up on reentry if the counterweight were destroyed. Even if the entire mass of the cable (sans counterweight) somehow fell in one piece and wrapped around the earth several times, it would only cause a path of damage a few meters wide (and most of that damage would be negligible, think about how something flat, wide, and very lightweight falls). I would imagine the terminal velocity of the cable would be quite slow. Similar to a piece of cardboard.

Oh not to mention that it would take quite a while to fall, and the population along the equator (which is mostly ocean) is very light. With a little warning, you could stand outside and watch it fall, and step out of the way if it was coming towards you. It would fall that slow.

Some interesting Sci-Fi interpretations of it

[moldar]

You can check out the first 5 chapters of The Web Between the Worlds by Charles Sheffield or The Fountains of Paradise by none other than Arthur C. Clarke. Both are an intereting read and were written at about the same time.

Does this cable conduct electricity?

[Decimal Dave]

The line might generate a lot of electrical potential if it didn't remain stationary relative to the earth's magnetic field... Also, wouldn't things like wind, static electricity, lightning and auroras cause problems with a 22,000 mile long cable?

Re:Does this cable conduct electricity?

[Rasta Prefect]

A carbon nano-tube cable shouldn't develop any electrical potential moving through a magnetic field. This might be a problem with any metallic cabling run along the support cable for data transmission purposes, but I really doubt they'd want to do that. Added weight and all. On the other hand, it's free power.
Wind would probably be a very minor issue - compared to supporting it's own weight, wind would provide a fairly minor amount of stress. Static electricity - Maybe just run a ground up and down to deal with that a lightning.

Re:Does this cable conduct electricity?

[Froze]

The answer is.. yes, sortof and no.
Depending on the conformation of the nanotube. Imaging a piece of hexagonal graph paper rolled into a tube. The alignment of the edges of the paper define the chirality of the tube. Some chiralities are conducting, others are semiconducting and still yet others are insulative. Chances are that the tubes used in the tether would be of a chirality that was not conductive, although it might be interesting to build a giant computer (just wires, semiconductors and insulators) out of the tether.

Now for the obligatory quip,

Imagine a beowulf cluster of them! ;-)

Why beanstalks won't happen here.

[Guppy06]

Because if it fell down, it'd be about as destructive as a thermonuclear bomb (kinetic energy's a bitch). And NOBODY would want this in their back yard after 9/11.

On the moon, Mars, any other sparsely-populated/unpopulated body in the solar system? Sure. But not here.

Re:Why beanstalks won't happen here.

[km790816]

Put in next to a large body of water and use the stablizers to crash it gracefully into the ocean.

Now you just have to worry about Green Peace.

Re:Why beanstalks won't happen here.

[kawaichan]

Rest asure, it's well be in the middle of the nowhere.

It will have to be near the equator (geosync) for this thing to work.

Sure sounds crazy, but this sounds awfully cool

Re:Why beanstalks won't happen here.

[magarity]

"On the moon"

The moon revolves much too slowly. The far end of the thing is pulling up due to centripital forces. In orbit around earth, unless it were cut up high, any saboteurs who cut it down low will just send the cable and orbiting anchor station slingshotting away into deep space/sun/anywhere but back to earth.

Re:Why beanstalks won't happen here.

[i7dude]

"Put in next to a large body of water and use the stablizers to crash it gracefully into the ocean."

crash it gracefully...

what is it about that phrase that just doesnt sit well???

dude.

Re:Why beanstalks won't happen here.

[davedoom]

This problem has been solved. In 1982 Paul Birch developed a new technique for dealing with the very long space elevator and associated problem.
http://www.paulbirch.net/OrbitalRings-I.zip
http://www.paulbirch.net/OrbitalRings-II.zip
http://www.paulbirch.net/OrbitalRings-III.zip

Re:Why beanstalks won't happen here.

[(H)elix1]

Put in next to a large body of water and use the stablizers to crash it gracefully into the ocean.

Now you just have to worry about Green Peace.

You know what a little earthquake can do to a shoreline thousands of miles away? If it fell out of the sky in the Pacific, it would take care of JavaOne this year....

Re:Why beanstalks won't happen here.

[Anonymous Coward]

...And NOBODY would want this in their back yard after 9/11.

Opposed to before 9/11, when EVERYONE wanted it in their backyard.....*shrug*

Re:Why beanstalks won't happen here.

[ender81b]

Not neccesarily. If you detach the cable from the base (Earth-Side) all that happens is you have to reattach it (Assuming the Space-Side can hold the cable in orbit.) Any prognosis of doom would have to come from detaching it from the space-side in which cause Earth's gravity would pull it down. Now, crashing an airplane into the WTC is one thing, taking down a orbiting space asteroid is quite another. (Of course in Kim Stanley Robinsons Mars series that is exactly what happened but..) And the cable itself can withstand the force of multiple nuclear explosions (has to b/c of forces acting upon it)meaning it ain't coming down easy.

If it *does* fall down it won't case all that much damage. The cable will wrap around the earth in a straight line from where it was cut. At the beginning of the impact the kinetic energy wouldn't be that much it wouldn't be until later on that you would have to worry about any serious affect. By the second time around the earth the cable will began deterioting and exploding in the upper atmosphere.

Also since this has top be placed in a geo-synch orbit it needs to be located close to the equator. I.E. if it falls it hits a whole lotta ocean and not much else. It shouldn't be too hard to figure out a spot where it nearly completely avoids populated areas. Futhermore having breakaway points on the cable itself would allow for only say 1/10 of the cable to impact the earth the rest would break and fly off into space. place it on the coast, the thing breaks off and the 1/10 impacts the pacific/atlantic ocean. Done deal.

If we can build a damm space elevator we can protect it!

Re:Why beanstalks won't happen here.

[Anonymous Coward]

First of all this isn't a Building it's a Cable the largest elevator cable ever granted, but the cable is composed of carbon nanotubes -- which puts it as 30 times stronger than steel in the first place.
Second it's in geosync orbit It's NOT a building In fact one plan puts it in the middle of an ocean attached to a ship at one end and a space platform at the other. So that means that the geosync orbit platform can keep the cable in a stable orbit even should part of the cable be sheared free. Also you can design the cable to have point where the cable can be seperated in an emergency causing only a fraction of the cable to fall to earth.
Also Considering that it's being built in the middle of international waters there is Nothing any government can do except threaten nuclear war to stop this thing going up. Keep in mind that it would go up at the equator and equatorial nations don't have nearly enough clout to stop this thing going up. So as soon as the technology (carbon nanotubes) is finished one of these could go up as soon as the money to pay for building 22,000 miles of carbon nanotube cable is organized. And once one of these things goes up it would have a virtual monopoly on space travel they chould charge half what the shuttle costs and make enough in a year or two to cover the capital expense of building the first one. There could be a dozen of these a decade after the first one is built, and the moon could be a very popular resort.

Re:Why beanstalks won't happen here.

[praedor]

Yeah! Tough shit for those annoying countries
at the northern part of S. America. And Africa, don't get me
started on Africa. Serves them right if a high-speed cable comes
crashing down across the widest part of the African continent
twice! They're lame...and so's all the African wildlife!

Anyway, they ain't rich and powerful so screw 'em. YES in
your backyard!

It's a moot point anyway. One wont be built anymore than
an Orion will.

Re:Why beanstalks won't happen here.

[Jeremi]

Now you just have to worry about Green Peace.

Barring safety issues as mentioned by the previous poster, I would think Greenpeace would be all for this. It would replace rocket launches, many of which are quite environmentally unfriendly. The environmental effects of a space elevator, on the other hand? Negligible, as far as I can tell.

Re:Why beanstalks won't happen here.

[Guppy06]

"Put in next to a large body of water and use the stablizers to crash it gracefully into the ocean."

One word for you: tsunami.

Re:Why beanstalks won't happen here.

[Guppy06]

"Rest asure, it's well be in the middle of the nowhere."

There is no such place as far as something this size is concerned.

"It will have to be near the equator (geosync) for this thing to work."

You have no idea how high up that is, do you? Measured from the surface of the earth, in order for the top to be in geostationary (I don't even want to think about putting it in geosynch, the flexing would be murder), it would be over 22,000 miles tall!!! To put that into perspective, that's about the circumference of the earth. Wrap it around the equator and it would touch itself. Even if you put it in Ecuador and it snapped cleanly in half, you'd still have pieces of it landing in the Indian Ocean with some ungodly velocity.

Re:Why beanstalks won't happen here.

[Guppy06]

"The far end of the thing is pulling up due to centripital forces."

If it were that tall, anybody at the top would be squished.

Re:Why beanstalks won't happen here.

[Guppy06]

"If you detach the cable from the base (Earth-Side) all that happens is you have to reattach it (Assuming the Space-Side can hold the cable in orbit.)"

Essentially, orbit means "centripetal force juuuust matches gravity." If the top is in geostationary orbit, then only the top is in microgravity. Every single inch below the top has a net force pulling downward. The lower your altitude, the faster you have to go to be in orbit (one revolution per day at geostationary, one revolution per hour at LEO). A break at any point in the beanstalk would bring it down.

You could make it tall enough so that the sum of the centripetal force of the end counterbalances the weight of the structure, and this would put the structure under tension instead of compression.

However, if you cut the structure anywhere between the surface of the earth and geostationary, everything below the cut will come crashing down. Fly a plane into it at seven miles, and you have a seven mile structure (about 35 times the height of the WTC) falling towards you. If the US can hit ballistic targets at a few hundred miles up with a kinetic-kill vehicle, Joe Shmoe with his suitcase nuke on a V-2 can hit a stationary target at that altitude. If there's a time-bomb on the elevator that goes off when the elevator floor is at or near geostationary, then we have 22,000 miles of material coming down.

"And the cable itself can withstand the force of multiple nuclear explosions (has to b/c of forces acting upon it)meaning it ain't coming down easy."

Tension, compression, and shear are three different things. Just because a material can withstand one or two of the three doesn't mean it can withstand all three.

And then there's a fourth factor: Heat. This was the WTC's weakness. While the steel structure withstood the airplane impacts, it couldn't survive the heat of the fire. Sure, the beanstalk might be able to survive the blast from a nuke, maybe even a shockwave if it was within the atmosphere, but nothing can survive the heat.

"The cable will wrap around the earth in a straight line from where it was cut."

No. Your main problem here is that you're assuming that all the mass will be at the top of the structure, forcing the structure below it to follow the top along as it comes down. Gravity being what it is, the center of gravity (assuming a structure of uniform density) will be somewhere between the bottom and the half-way point. And because gravity increases exponentially as you go down, taller structures will have their centers of gravity further from the midpoint than shorter ones.

So while you're correct in thinking that each unit length of cable will have to deal with tension in the cable (due to the motion of the rest of the cable) as well as gravity, you're incorrect in guessing what direction that tension will pull. For points in the structure higher than the center of gravity, the tension in the structure will be the stronger of the two forces, pulling the structure down along it's length instead of letting it spiral down in free-fall.

If anything, the top of the structure may fall along a straight line because it got snapped like the end of a whip, giving it more kinetic energy than it would have had if it were just in free-fall (and causing more damage than a free-fall would have done).

"By the second time around the earth the cable will began deterioting and exploding in the upper atmosphere."

First off, you have no idea how large these pieces may be when they break off. Second, all the kinetic energy of hundreds or thousands of miles worth of stuff has to go somewhere. If the actual mass doesn't make it past the upper atmosphere, then the momentum and kinetic energy just gets transferred to the atmosphere, which means a shockwave.

"Also since this has top be placed in a geo-synch orbit it needs to be located close to the equator. I.E. if it falls it hits a whole lotta ocean and not much else."

Tsunamis. Big tsunamis. And most of the world's population lives within 200 miles of the ocean.

Remember, something with the mass of a small island killed off the dinosaurs. What we're talking about is a structure with at least that much mass. While it may not be one big chunk, mass is mass and it's still coming down in a very short period of time.

"Futhermore having breakaway points on the cable itself would allow for only say 1/10 of the cable to impact the earth the rest would break and fly off into space."

Just for the sake of repeating myself, if the cut is anywhere between 0 and 22,000 miles up, anything below it is coming down. Period.

Re:Why beanstalks won't happen here.

[Guppy06]

"First of all this isn't a Building it's a Cable the largest elevator cable ever granted, but the cable is composed of carbon nanotubes -- which puts it as 30 times stronger than steel in the first place."

But we're not talking about something that's only 30 times bigger than the WTC, are we?

"Second it's in geosync orbit It's NOT a building"

No, the very top is in orbit. Everything below that is a building.

"In fact one plan puts it in the middle of an ocean attached to a ship at one end and a space platform at the other."

As I already went on about ad nauseum in another post, every single point in that structure between the ground and geostationary (all 22,000 miles of it) has a net force on it pointing down. I don't care how light that material is, 22,000 miles of it will sink that ship.

"Considering that it's being built in the middle of international waters there is Nothing any government can do except threaten nuclear war to stop this thing going up."

Somebody never read Sun-Tzu. If you don't like the idea, you cut off where the supplies come from.

"So that means that the geosync orbit platform can keep the cable in a stable orbit even should part of the cable be sheared free."

Any point below the top has to be going faster than the top in order to be in orbit. But instead it's fixed in relation to the surface of the earth. So all points below the top are actually going slower than the top. Which means that the net force on all points below the top is DOWN.

"Also you can design the cable to have point where the cable can be seperated in an emergency causing only a fraction of the cable to fall to earth."

Whether it comes down in one 22,000 mile long chunk or 22,000 chunks a mile long, it's still coming down.

Re:Why beanstalks won't happen here.

[bryan1945]

And most of it would burn up in the atmosphere. You may have some hundreds of depleted material hitting the ocean, but nothing like you are talking about.

Re:Why beanstalks won't happen here.

[Guppy06]

"And most of it would burn up in the atmosphere. You may have some hundreds of depleted material hitting the ocean, but nothing like you are talking about."

Burning up in the atmosphere doesn't save you from the laws of conservation of momentum and energy. If you have hundreds of thousands of tons of stuff hitting the atmosphere, whether it makes it through or not you're still going to have a very nasty shockwave to deal with. Hell, the force of the air moving alone could be enough to start those tsunamis.

Re:Why beanstalks won't happen here.

[magarity]

"If it were that tall, anybody at the top would be squished"

No, make it long enough that the anchor station's centripital force outward equals one gravity (or a little less). But it can't be nothing, duh: If that were true, one person on the ground could give a small tug on the cable and the thing would fall on them.

How do you think the thing can stay up on a *cable*? It's not a rigid tower. And it can't be in a geosynchronous orbit because that's where the forces would be equal and tugging on it would bring it down. A tethered space elevator is something for a low (think space shuttle) level orbit.

Re:Why beanstalks won't happen here.

[perky]

Keep in mind that it would go up at the equator and equatorial nations don't have nearly enough clout to stop this thing going up.

in other words, "we're America nd we don't give a shit about anyone else. I mean, what are they gonna do?". Exactly the same attitude which has seen that idiot Bush recinding on environmental treaties, shittinbg all over Alaska for the sake of his beloved oil, and Bombing the crap out of Afghanistan and then expecting the reast of the world to pick up the peices. This is why the good ol' US of A produces 25% of the world's pollution with 5% of the world's population.

Just because you can do what the hell you like doesn't mean that you should. Perhaps this is why the rest of the world hates America.

Re:Why beanstalks won't happen here.

[Guppy06]

"How do you think the thing can stay up on a *cable*? It's not a rigid tower."

If that were the case, then you'd have to make the cable long enough so that its center of gravity (as opposed to its center of mass) is in geostationary. As I pointed out in another post, if we assume a uniform density, this puts the height at 985 earth radii or so, well over 15 times the mean distance between the earth and the moon. People at the top would experience about 3 G's of outward acceleration (until the moon snapped off the top).

"A tethered space elevator is something for a low (think space shuttle) level orbit."

The lower the altitude, the faster you have to be going to be in orbit. In the example of a beanstalk with its top in geostationary orbit, only the top is going fast enough to be considered in orbit. All points below it are going to slow to be in orbit at their altitude (in fact, they're going even slower than the top).

If you put the top at 500 km, if it's stationary with relation to the ground, those at the top would still be experiencing about a full G of weight (about 9.3 m/s^2 instead of our usual 9.8 m/s^2).

Keeping the same hight but putting the top in orbit would mean having it circle the globe once every 87 minutes. Assuming you have the thing moving along with the earth's rotation, the bottom will be dragging along the ground at about 15,000 miles an hour (with all points above naturally going faster). I'd hate to think of what something that big going at about mach 20 would do to the surrounding area.

Re:Why beanstalks won't happen here.

[Anonymous Coward]

List of all the scientific and engineering advances that Greenpeace is "for":

[empty list here]

Re:Why beanstalks won't happen here.

[Anonymous Coward]

Remember, something with the mass of a small island killed off the dinosaurs...mass is mass and it's still coming down in a very short period of time.

You're forgetting about velocity. The energy of an asteroid strike isn't just the result of the mass, it's also from that mass hitting you at about 20 miles a second. The beanstalk is going to come down a lot slower than that.

Re:Why beanstalks won't happen here.

[nicklott]

...and of course no one wants thermonuclear weapons do they?

AC Clarke's Fountains of Paradise

[backtick]

That's the book he wrote about this. Worth a read, it even describes some of the projects by the US and Russia concerning this decades ago, in the appendix.

Where's the info on the counterweight?

[pcx]

You can't have the orbital part without a counterweight otherwise you have gravity pulling down on the vast majority of the cable and the whole thing falls out of the sky. So you need a mass at the end of the cable so angular momentum holds everything up. Last I heard you needed a lot of mass to do that -- like a trapped asteroid or something -- far more mass than we havet he technology to put into orbit.

Re:Where's the info on the counterweight?

[ArsonSmith]

All you need is for the cables center of gravity to be located in geosyncronus orbit This can be helped with a counter weight at one end but it is not required.

Re:Where's the info on the counterweight?

[ArsonSmith]

Damn i sure don't know how to spell though do I?

Re:Where's the info on the counterweight?

[coyote-san]

I think most serious plans suggest capturing an object already in space, not lifting it from the ground.

But even if you lift it from the ground you can still bootstrap the system. Say the cable extends an extra 20k past GEO - maybe you start with a minimal core and skimpy cars and can only lift 50 extra pounds. No problem, you just lift 50 pounds at a time for a few months. Then 100 pounds at a time. Then 200 pounds. Over time you can expand the core, improve the cars, and continue lifting additional mass into the ballast.

Re:Where's the info on the counterweight?

[RedWizzard]

No, you don't need a counterweight. If the cable is long enough so that the center of mass is in geostationary orbit it will just hang there by itself.

Re:Where's the info on the counterweight?

[NoMoreNicksLeft]

Yes, which means the actual length is 44k miles long. Cool, because the tram cars could go that much further. Launching something from it, would be as simple as traveling to the end, and letting go... the planet would hurl you out into space, with a decent initial velocity.

Re:Where's the info on the counterweight?

[DaCool42]

until you lift something big, throw of the balance, and the whole thing comes down.

Re:Where's the info on the counterweight?

[RedWizzard]

It's not hard to calculate just what sort of mass you can safely lift given the mass of the cable. Infact you could just send ever larger chucks of mass to the cable's center of mass to build up the anchor rather than trying to grab an asteroid or something.

Re:Where's the info on the counterweight?

[passion]

Makes me think of Lex Luthor's escape from prison in Superman 2 when they had to leave Otis behind as his largeness started to climb on the rope ladder into the hot-air balloon.

Re:Where's the info on the counterweight?

[Pig Hogger]

No, you don't need a counterweight. If the cable is long enough so that the center of mass is in geostationary orbit it will just hang there by itself.

And the tidal forces will keep it neatly stretched, too.

Re:Where's the info on the counterweight?

[Guppy06]

"No, you don't need a counterweight. If the cable is long enough so that the center of mass is in geostationary orbit it will just hang there by itself."

No, not the center of mass but the center of gravity, which when you're talking about structures this high is a completely different animal. Because the force of gravity drops off exponentially with altitude, the bottom is always heavier than the top and so you'll need to put more on top to get that center of gravity higher.

I did the math last night with the help of my TI-92. Assuming a structure of uniform density, to put the center of gravity of the structure at geostationary altitudes (about 22,000 miles or 6 earth radii) requires the entire structure to be about 985 earth radii (about 20 light-seconds) tall.

With a structure that high, people at the top would experience a net acceleration of about 3 g's outwards and be travelling at about 960,000 miles an hour.

Of course, this is all moot because it would only stand for a few weeks until the moon breaks most of it off at 60 earth radii.

Re:Where's the info on the counterweight?

[Anonymous Coward]

no one cares what zou think. im tempted not to wait the 20 seconds out. grr.r grr. grr. there.
fuck zou.

Re:Where's the info on the counterweight?

[Trogre]

"No, you don't need a counterweight. If the cable is long enough so that the center of mass is in geostationary orbit it will just hang there by itself."

Hmm, a blue-green planet weighing billions of tonnes on one end of the line, no counter-weight on the other end.

Where did you say the centre of mass had to be again?

.
.

Re:Where's the info on the counterweight?

[pclminion]

Because the force of gravity drops off exponentially with altitude, the bottom is always heavier than the top and so you'll need to put more on top to get that center of gravity higher.

It doesn't drop off exponentially, it drops off as the inverse square. This is an awful lot different from exponential. The universe would be much different if the force of gravity was proportional to e^(-r) ;)

It's been done in the movies...

[TrollMan 5000]

Welcome to the !

hold up...

[niekze]

they want to have a 22,000Km cable to space, but I can't get DSL because I'm 2.3 miles away...

Grrrr

Re:hold up...

[tunah]

Damn americans. Miles are *longer* than kilometres.

Re:hold up...

[L053R]

No worries, soon XXXDSL will be there, hehehehe

Re:hold up...

[Bodrius]

Yeah, remember the Mars Observer? Not even NASA can get right the metric system.

Hmmm... Now I wonder...

Re:hold up...

[Anonymous Coward]

Obviously tunah, not being a 'damn American' failed to know that the comma means thousands in the US. Maybe mister clue-by-four uses a comma as decimal point himself, but in the US people use a point for that.

Now why tunah is rated +5 funny, and you are rated -1 redundant: There are two possible explanations: Maybe the current editors themselves don't know which symbol separates thousands in the land of the mile, or they do and just think it's funny that such a clueless person thinks he's so smart he puts it in his signature.

Posting this anonymously, because I don't trust the editors to do the right thing.

Smite me.

Re:hold up...

[Anonymous Coward]

Where did you learn math? 22 thousand kilometers is a lot more than 2.3 miles...

Re:hold up...

[Anonymous Coward]

Personally I think tunah got +5 for his anti-Americanism.

Could you imagine...

[Marx_Mrvelous]

A beowulf cluster of these? haha in all seriousness, if they can build one, maybe the could build 5 or 10. What a better way to get rid of nuclear waste? Elevate it into space, then toss it towards the sun!

Okay,. who did that?!

[Psiren]

Trouble is, if someone farts in the elevator, it's a damn long wait before you can open the door... ;)

Re:Okay,. who did that?!

[limber]

if someone farts in the elevator, it's a damn long wait before you can open the door...

On the other hand, think of the positive possibilities. How does that song go? Love in an elevator...

(does that make aerosmith the purveyors of elevator music?)

(insert 'shaft' pun here).

To finish my previous post...

[TrollMan 5000]

Wonkavator (tm)!

Shoulda used "Preview"...

Yes. Re:Rotational energy

[HiredMan]

The short answer is: Yes.
Physics works everywhere all the time. When you climb a flight of stairs or walk up a hill it slows the Earth's rotation - and it speeds back up as you walk back down.

No - seriously - just as an ice skater's rotation slows or speeds as they extend or contract their arms the same principles apply to all rotating bodies. Everytime we slingshot a space vehicle around the Earth we are effectively transfering some of the planet's energy to the vehicle and that energy has to come from somewhere.

But the amounts here are so small that the effect is not measurable or "effective" in the scale of anything we could notice. It's like the fact that anything with mass has a gravatational field - but you don't notice the effect of the gravity created by your pen.

=tkk

Re:Yes. Re:Rotational energy

[Gaijin42]

Actually, its not quite like a skater...

A sakters arems and body have the same angular velocity, because her arms are attached to her body. it takes more energy to move her arms around when they are extended (further to go) and since they are attached to her body, the whole thing slows down.

In a space ship, the earth and the ship are not attached. As soon as the ship leaves the ground, the earth spins out from underneath it. Due to momentum, and air viscosity (pushing the ship in the direction of the earths rotation) this is not nocieable until the ship is quite high, but conservation of rotational inertia is not the principle you need to follow in this case.

Re:Yes. Re:Rotational energy

[Chester Abecrombe]

You neglected to factor the large amount of meteorites and space junk that is constantly falling to the Earth, thus increasing earth's energy. I think it's safe to assume that more is being added to Earth's mass than is being taken away.

Re:Yes. Re:Rotational energy

[HiredMan]

A sakters arems and body have the same angular velocity, because her arms are attached to her body. it takes more energy to move her arms around when they are extended (further to go) and since they are attached to her body, the whole thing slows down.

Sorry, maybe I was unclear, I was refering to the fact that when you climb a flight of stairs the Earth slows down. THAT effecting rotational energy is like the skater.

The slingshoting a spacecraft is more like a line of skaters in a whip. The last skater gets flung at a far greater speed - stealing energy from the whole group. But if the group is large enough it doesn't notice.

=tkk

Re:Yes. Re:Rotational energy

[uberdave]

True. However, the angular momentum that this junk contributes to the earth is not all in the same direction. Some will act to speed the earth up, some will act to slow it down. Some will act to tilt the axis. It is probably safe to assume that it averages out to zero.

Hmm... What would happen if all the Chinese started walking east?

Re:Yes. Re:Rotational energy

[Anonymous Coward]

I'm no physics major, but while raising large masses would slow the earths orbit, once it was 'released' wouldn't that actually speed the earths rotation speed, since a less massive object would spin faster?

Where to put it?

[Rubel]

is there a physics-related reason to place it in a particular spot? one of the poles? The equator?

Re:Where to put it?

[oregon]

It has to be the equator - the other end has to be in geosynchronous orbit.

Re:Where to put it?

[ZPO]

Equator as it would be the sub-satellite point.

Re:Where to put it?

[ryusen]

the article (i read the readers disgest version) said it would have to be at the equator.. my guess is that a 22,000km cable no matter what it's made of will be heavy... the only way to keep it up would be to use the force of centrepedal(sp?) acceleration of an anchor to counteract the gravity of the situation...

Re:Where to put it?

[DaCool42]

I'm afraid you have the an incorrect concept of centripital acceleration. What you are thinking of is centrIFUGAL acceleration, which is a ficticious force. It doesn't exist. Centripital acceleration is the force that holds a mass in a circular motion. It is always towards the center of the circle.

Re:Where to put it?

[ryusen]

it's been a while since i took a physics class, so i figured i wouldn't be able to explain it well .(
what i meant is that the cord will impart Centripital acceration on the anchor, which will want to fly away. if we balance the rock wanting to leave with the cord wanting it to stay then we have a happy family? i could be wrong, but it seemed to me the logical way to balance the weight of the rope...

Re:Where to put it?

[Maldivian]

On the island Gan, in the Maldives, as noted in the NASA research and AC Clarke. But, I doubt the gov of Maldives would let that happen. NASA says it might build a rig outside the 200 nautical mile zone of Maldives, but since Maldives is such a vocal environmentalist country, this might not fly too. But on a happy note, the people of Gan would welcome this, just as they welcomed the RAF base GAN in the 50's.

It's the most feasable place due to abscence of any real deadly storms and other stuff, not to mention it's on the equator.

Re:Where to put it?

[n9hmg]

"It has to be the equator - the other end has to be in geosynchronous orbit."

That's only true of a ballistic orbit. We're talking about a mechanically tethered orbit.

If you put it at a higher latitude, it'll have farther to go to get the center of mass past (PAST, NOT AT) geosync orbit, and the center of gravity of the whole earth-tether system will be offset from the line of the tether, so it will have lateral force on it... it'll bow a bit, is all. If i'm not mistaken, that should give some level of gravity all the way out, even at geosync. That might be cpositive, if the carriage can rotate to keep the passengers feet "down", and minimize space sickness.

But...

[Treskin]

Wouldn't something like this become a fairly large target for terrorism? If 2 towers sticking out of the New York skyline were so easy to hit, how about a tube rising from the ground to above the Earth probably in the middle of Nevada (I know I wouldnt want 22,000 miles of cable falling onto my house).

I guess they could shoot at anything that comes within such and such a radius of the cable but how secure could they really get such a thing...

Re:But...

[mozkill]

hmm.... lets see... this cable weighs at least a 10 pounds a foot... lets say 50,000 pounds or 25 tons per mile...at the least....what kind of damage would 500,000 tons of cable do if it hit the earth?

i wouldnt want to guess....

Re:But...

[Mandelbrute]

Wouldn't something like this become a fairly large target for terrorism?

Everyone dies, but that is no reason not to live.

IMHO the terrorist threat should be the last thing to be considered - if nothing is built in case it gets blown up then no-one will get anywhere.

Re:But...

[freerangegeek]

It really doesn't much matter where they put it, 22000 miles goes a VERY long way when it wraps over the circumference of the earth (~24,900 miles?). That's 88 percent of the way around. Let's hope the momentum carries the cable across water for most of it's journey, otherwise it's going to be one hell of a whip crack. OUCH!

Re:But...

[Anonymous Coward]

Towers want to fall down. Hit them and they crumble. 10000 people die, Americans lose their freedoms

Cable wants to fly away from Earth. Cut it at the base and everyone in the elevator sails off into space, maybe 10 people die. So what.

Think about it... Just how hard can YOU push a cable?

Re:But...

[cicadia]

You forgot about the 10000 people in the hotel and casino at the top of the elevator...

On a side note, how fast would something like this actually fly into space? Even if you could hit it at 30,000 ft with something like an airplane, roughly 99.97% of the cable's mass should still be hanging in space.

Given that the cable was held in place by its own mass originally (not by being welded to some island,) and that it was already in geosynchronous orbit, just how quickly would it start to move? Would we have time to re-anchor it before we lost the whole thing?

here's a (slow) link in html format

[headsling]

It's really slow, but it ain't pdf format http://www.niac.usra.edu/files/library/fellows_mtg /jun00_mtg/html/472Edwards/472Edwards.html

Forces?

[Izeickl]

Can you imagine the force of wind blowing on this thing (and its own weight)? Will have to be ultra aero-dynamic to not get blown over when a gust of wind blows along its 20K miles! How much would rain water add up to along a 20K mile stretch too? (Anyone have an idea at max height for rain??)

Re:Forces?

[xX_sticky_Xx]

No worries about rain at 20,000 miles (especially considering the earth's atmosphere is only a couple of hundred miles deep). Rain doesn't occur past 2-3 miles or so.

Re:Forces?

[NoMoreNicksLeft]

The atmosphere only extends 100 miles up or so. No wind above that. And rain moves up/down, not sideways... and again, not higher than the first few miles.

never will be safe

[xah]

Last December 19 on Slashdot, it was an 8 megabyte PDF, not a 15. That Slashdot article is found here.

I agree with your dire forecast. It would be terrible for such a huge thing to crash to the Earth. It could wrap around the entire Earth. Besides, this "space elevator" would be a giant, provactive, easy target for terrorists.

From the TechTV article: "Edwards admits the elevator could be a terrorist target. But, he said, "It's away from everything. There are few, if any, airline routes through there. And a few well-deployed ships would be able to protect the station, the anchor station, and the cable."

How comforting. The safety of potentially millions of people will depend on the cable being "away from everything," and on the competence of a "few" ships. How bizarrely foolish.

Among others, this "space tether" would be vulnerable to the following terrorist attacks: missle, bullet, bomb, acid, human piloted aircraft, remote controlled aircraft, ground vehicle, laser, and fire. Will those "few" ships include an aircraft carrier? Will they carry anti-missile batteries? What about the possibility of one of "our" planes accidentally running into the cable?

The true believers need to wake up. Space elevators will never be safe, and thus will never be feasible.

Re:never will be safe

[kilgore_47]

Besides, this "space elevator" would be a giant, provactive, easy target for terrorists.

If we let that stop us, then the terrorists have already won!

Re:never will be safe

[Doctor Faustus]

They're talking about a tube with ~paper-thickness walls (single layer of Carbon-60?). If something like that broke into small sections, I wouldn't think it would really crash, but just drift down sort of like a bunch of kites that lost their strings. It would be expensive to replace, but no catastrophe.

I don't have any idea what would happen if it broke free while mostly intact, but we could always make sure it breaks up in that case. If nothing else, the defense force could just shoot at it.

I think those few ships would probably just be a few missle cruisers in a ring. If there is no legitimate air traffic in that area, they have a lot more leeway to defend the elevator. Anyway, it's not like Aegis cruisers have never shot down airliners before... (U.S.S. Vincennes, late 80's)

Re:never will be safe

[shadowbearer]

Safe? Errrr.....what's that? One definite benefit I see is a project like this getting us into space for good; which would mean we could loft equipment to protect the earth from asteroid impacts. That kind of outweighs your arguments. SBearer

Re:never will be safe

[GunFodder]

Good point. Imagine the danger of strapping a few idiots to the top of a cylinder full of insanely flammable gasses to escape the Earth's atmosphere. This "rocket" could blow up and kill everyone aboard. Or it could crash and take out many other innocents. It could be shot down by missiles, bullets, bombs, etc. And worst of all, it might ignite the upper atmosphere and end life on Earth as we know it!

Re:never will be safe

[Jeremi]

The true believers need to wake up. Space elevators will never be safe, and thus will never be feasible.

Translation: "I can't imagine any solutions for these problems, therefore no solution could possibly exist".

Re:never will be safe

[h4x0r-3l337]

I agree with your dire forecast.

How unfortunate. Totally unneccessary though.

It would be terrible for such a huge thing to crash to the Earth. It could wrap around the entire Earth.

No it wouldn't.

Besides, this "space elevator" would be a giant, provactive, easy target for terrorists.

A terrorist would have to cut the cable in space in order for it to fall back to earth. Attacking the anchor-point will at most have the effect of setting the elevator adrift, away from the earth. This could be compensated for immediately by releasing ballast from the space-end of the cable, thereby keeping the elevator in place until the cable can be reattached. Worst case is when the cable is cut at very high altitude, which will cause the section below it to fall back to earth. The cable is relatively light though, and will do little damage.

Re:never will be safe

[WolfWithoutAClause]

The tether is expected to get chopped down occasionally by meteorites or space debris. It would be designed to burn up during reentry. It would not harm the earth in any way. The remaining lower length would end up in the ocean, and can probably be collected up and incinerated.

Besides. it's only 20 tonnes initially, an earth killer? I don't think so.

Re:never will be safe

[Bill Currie]

That wasn't a dire forcast. I was curious how high something would have to be up the cable for it to miss the atmosphere at 90-100km (I don't remember the numbers I used for that) and thus not come crashing down too quicly (ie, giving time to do something about the object, whether it be a wrench or chunk of cable). When I determined that it was in that 25-30 thousand km range, I realised that it's a bit of a moot point when it comes to `disaster scenarios' as 30000km worth of cable will do unpleasant things no matter what.

Note, however, that I didn't take air friction into account other than deciding on a safe/unsafe border for chunks to fall to (if they miss the atmosphere, they're not coming to the surface any time soon (days to years)). And then, most of the euator is water, and the cable would likely come down relatively gently. I still wouldn't want to be anywhere near it, but forget the world wide disasters other than maybe some minor coastal flooding and some unpleasantnes in the vicinity of South Africa (hmm, or os that north? My African geography is rusty when it comes to the equator).

Maybe I should have stated this in my post, but I'm actually for a space elevator.

Re:never will be safe

[xah]

This is racist and ignorant. What do you think the people who live on the equator will think of this? Would you care if they were white?

What about marine life? What about the environment?

I'm so disappointed by Slashdot. So many bright people, and so many closed minds.

The beliefs of Slashdot, in summary: (1) space elevators are obviously good and have no drawbacks at all; (2) there is no need for any patent or copyright; (3) people who blame their health symptoms on "RF fields" or cell phones not only are wrong in assessing blame, but obviously have no health symptom except mass hysteria; (4) RSI and ergonomic injuries are believable, in contrast to other maladies; (5) if there is a proposed technology involving computers or robots, it will obviously work; (6) if there is a proposed technology involving a potential new energy source, it will by definition never work (not because it is fraud, but because we have already discovered all of those); (7) spelling, grammar, and style in the English language is unimporant; (8) spelling, grammar, and style in the C language is crucial; (9) critics of Slashdot get a -1 offtopic or -1 overrated; (10) critics of critics of Slashdot get +1 interesting; (11) the Simpsons is funny; (12) making fun of Slashdot is not funny; (13) Star Office is good enough for word processing, because no real person needs to do more than type a two page letter; (14) technology never has a downside; (15) South Africa is on the equator; and (16) all the tech stocks like LNUX are coming back, soon, higher than ever.

Re:never will be safe

[Anonymous Coward]

looooooooooooooooooool - it's funny cuz it's true!

Re:never will be safe

[Drake42]

1) We are currently discussing drawbacks and solutions to them. Pay attention.
2) Most people here believe that the idea is needed, but the law is ineffective. Very different from believeing that the idea is not needed. Again pay attention.
3) Most people here love their cell phones. Kind of skews the audience. A technology discussion forum obviously will love technology. Pay attention to your circumstances.
4) Many people here have felt RSI. No on here I know of has felt pain from RF. Thus people are posting based on attention to their own experiences. I bet you've had sore wrists, but not cell phone cancer. With attention to your own experience what does that tell you?
5) Robots and machines are a understood problem. Most engineers feel that given sufficent time and resources most things are possible. Pay attention to the subject matter and you'll see why.
6) Pay attention to the source of the claims and you'll see why /. thinks their bunk.
7) Pay attention to your own grammer when you are condemning someone elses.
8) Most people here don't even write C. Pay attention to who is posting when you make a generalization.
9) You criticism was baseless and broad. It deserves to be modded down.
10)My cricism of your criticism is based on fact and deserved to be modded up. :]
11)No. The simpsons are no longer funny.
12)No. Making fun of slashdot IS funny. That's why so many people do it. (And bother replying to people who do it)
13)If you had paid any attention to StarOffice you'd realize it can do far more than two page letters.
14)Technology doesn't have a downside. However people's use of technology is a different matter. Pay attention to the difference.
15)The fact that you believe anyone believes this, shows that you are not paying attention to the post.
16)No one here believes that either. Pay attention to what people say, not what you think they would say if you let them get a word in.

Re:never will be safe

[Anonymous Coward]

Will those "few" ships include an aircraft carrier?

Hmm...$40 billion initial investment, just for your first low capacity cable, and you're scaling up from there...yeah, I'd say that's worth a carrier group. Maybe several. Given the enormous increase in capacity and decrease in expense compared to rockets, the cable would be by far the most strategic resource on the planet. It makes access to space cheap enough so you can do the really cool stuff - asteroid mining, powersats, etc.

15 Mb pdf

[sfraggle]

15 Mb * Slashdot effect = ....

Ouch. Thats gotta hurt.

Re:15 Mb pdf

[kilgore_47]

15 Mb * Slashdot effect = ....
Ouch. Thats gotta hurt.

Nah, I'm sure the majority of us won't download it. I know I didn't. ;-)

Damn!

[Anonymous Coward]

I guess this obsoletes my "space escalator" idea then, eh?

OT - Fiction for this scenario

[Embedded Geek]

(Yes, it's off topic... Put away your flamers)

This disaster was used (although on Mars) in the plot of in Kim Stanley Robinson's Red Mars (or maybe Green Mars... can't remember). In that case, though, the "beanstalk" was sabotaged as a weapon during a revolution. It wiped out a slice of a city, puncturing the atmosphere of a bunch of buildings, but had no casualties outside the settled areas. Can't have a tsunami in that thin an atmosphere.

Re:OT - Fiction for this scenario

[RedWizzard]

Mars is a much better place to experiment with spacehooks like this. It's easier to build them there, they don't need to be as big, and there wouldn't be the same disasterous consequences if and when something goes wrong. Larry Niven's written a fair amount about it, see for example The Barsoom Project.

Re:OT - Fiction for this scenario

[Sirch]

"" Can't have a tsunami in that thin an atmosphere""

Um, I think you're a little mixed up - maybe you're thinking of a tornado? In which case, it must still be possible, only the contributing factors to the formation of that tornado would have to be much greater than those on earth.

Or did you mean what you said? If so, then you've forgotten another thing! You cannot have tsunamis without water! (Or a similar liquid)

Of course, with a thin atmosphere, the boiling point of water would be lowered, meaning that it would be harder to have standing water on the planet, therefore making tsunamis impossible - no water, no wave! I don't know for sure how much standing water could survive on Mars...

Anyway, I've made my point. I should think that a space elevator crashing to Earth (or Mars, whatever) would probably do more than just slice through buildings etc. I'd imagine that the seismic ramifications would be significant.

Sirch

Re:OT - Fiction for this scenario

[jelle]

"It's easier to build them there"

Umm. We have only managed to send some satellites and a small electric robot to the red planet.

Now how are you going to get a construction facility, either staffed or fully automated, to mars?

I don't think at all it's easier to build anything there.

Just a pie-in-the-sky idea

[eaolson]

Sounded way too sci-fi for my taste at first

And it is exactly that, sci-fi. Sure, carbon nanotubes are incredibly strong. And they're also on the order of a few microns long. Now, this cable needs to be a few hundreds of thousands of meters long. You do the math.

It's fantasy. This is just never going to happen.

Re:Just a pie-in-the-sky idea

[mmontour]

And it is exactly that, sci-fi. Sure, carbon nanotubes are incredibly strong. And they're also on the order of a few microns long. Now, this cable needs to be a few hundreds of thousands of meters long. You do the math.

The semiconductor industry figured out how to make large single crystals of ultra-pure silicon, then pattern the surface down to a ridiculously fine resolution. The fiberoptic folks figured out how to make glass so clear that a light pulse can go through many many miles of it and still be recognizable at the other end. Molecular biologists can "amplify" single molecules of DNA into macroscopic quantities.

I wouldn't be so quick to say that we will never be able to make carbon nanotubes that are long enough to be useful as structural materials.

Re:Just a pie-in-the-sky idea

[eaolson]

OK, maybe never was too strong a word. But I bet you a nickel it never happens in our lifetime.

Here's why (I'm just estimating these numbers) I've been a bad little grad student, and have gotten a bit behind in reading up on these things, but lets say that we can currently make nanotubes about 100 microns (1E-4 m) long. Now, if we have a cable 100,000 km long, and we want each tube to run 1/1000 its length, then each nanotube needs to be 100,000 m long (1E5 m). That means we need to improve the fabrication process so that we can make them a BILLION times longer.

I just don't think that's as all feasable.

Re:Just a pie-in-the-sky idea

[Anonymous Coward]

Not true. Cotton fibers are also short, but you can make a rope long ehought to hang yourself. They just have to be oriented along the thread and they will hold by the friction forces.Those forces are strong enought as the length of the tubes is a few orders higher than their diameter.
(I wanted to add an illustration image but got a message: Lameness filter encountered. Post aborted!
Reason: Please use fewer 'junk' characters:)

Re:Just a pie-in-the-sky idea

[Anonymous Coward]

Read the paper, each tube only needs to be a couple centimeters long.

It's Been Done...

[Servo5678]

Big deal, Dr. Clayton Forrester accomplished this back in 1994...

Q: In season six episodes, M&TB and Dr. F. seem to have the ability to send objects back and forth to each other. How was that possible?
A: In episode 601- Girls Town a device was introduced that was variously called the "umbilicus," the "umbilicon" and the "umbiliport." It is, quite simply, a tube running from the SOL to Deep 13. In the first episode, it was connected to Gypsy, and objects left the SOL and arrived there through Gypsy's mouth. In later episodes, a simple oven door-like device both in the SOL and Deep 13 has served as the hatchway.

(From the Mystery Science Theater 3000 FAQ)

non teathered

[Anonymous Coward]

skyhook/space elevators are(ok would be) great for getting mass into orbit. nonteathered craft are not a problem if you can easily get mass into orbit. EG propellant, building materials. it sucks to have to send tons of support equipment in the form of rockets just to refuel a non teathered craft. but work should be done on rocketry too. besides who can make nanotubes in quantities sufficient to do anything real? last I heard manufacture cost millions of dollars and yields woudn't fill a spoon let alone stretch to low earth orbit.

Pie closer to hand

[Yurian]

Ok - The space elevator is a lovely concept, but it's only just possible with the theoretical limits of where we can go with materials technology - so its going to be pie in the sky (or lack there-of) for a long time yet.

There are some variations on the idea though,like this one, that are close to being possible with today's technology, and can even be provisionally costed. Basically the idea is to construct an elevated runway about 100km up, and use mass drivers to hurl stuff into orbit. At that altitude the saving from air resistance is huge and mass drivers become very efficient

At this stage, NASA speanding serious time thinking about space elevators is probably no more useful than daydreaming. Thinking about this kind of thing is probably more productiove though, becuase something might come of it in the medium term, and its almost as efficient as an evelator anyway - with the decided advantage of not being able to collapse and strangle the planet.

(Since I heard about this from a NASA researcher, maybe Im being a little harsh to accuse them of daydreaming)

Re:Pie closer to hand

[bryan1945]

Right, a "flawless diamond" 100km (60miles), would be so easy to do. AND cost less than $60billion, all by itself?

Yeah, it would be great to build such a thing, but the logistics are only JUST a little easier, if easier at all!

As for collapsing and "strangling the planet"(?- didn't know the earth had a neck), a 300km long ramp falling from 100km would be pretty freaking destructive! Probably a whole lot less than a (comparatively) thin wire wrapping itself around the equater (mostly ocean).

Yes, cheap access out of the gravity well is the current grail for space travel. But most of the scifi ideas to defeat the well are still mostly scifi. Carbon nanotubes, "flawless diamond" skyways, laser propelled rockets, skyhooks, and anti-grav. In time, science and engineering will probably solve these problems, but not quite yet.

Re:Pie closer to hand

[Yurian]

OK - your criticisms, are fair enough - but if you look at the facts a bit closer, a space elevator is really orders of magnitude more expensive and difficult than this elevated runway idea.

Firstly, you don't need flawless diamond - ordinary commerical artificial diamond will do fine. As for cost, well nanotubes are a bit pricy themselves - clocking in at a cool $500 per gram - so that gives you a projected cost of 33,000 trillion for an evelator at present. Just for the material, with no transport of construction costs. Steep.

The thing I love about this guy's proposal is that its close to being feasible with current tech. With existing construction methods using steel you could raise a tower 20 kilometres tall. With diamond 300km is no problem.

Obviosly, neither the elevator or this are practical while the cost of advanced materioals like nanotubes of synthetic diamond remain at current levels, but to quote from the article:

If an Apollo style (and -cost) project could do for diamond what the original one did for electronics, we could build the tower in the next decade or so. Molecular manufacturing, even of a fairly unsophisticated form, could make it economical. A mature nanotechnology would put towers within the capabilities of private enterprise, and make space travel cheap.

Materials technology are going to provide us with the right stuff sooner or later, and all Im saying is that this project is probably in the sooner catagory, while the space elevator is most definately a later thing.

As for damage, well, the mass of the elevator falling from geosyncronous orbit is going to create a thermonuclear size event. The ocean is no help, because it then creates a mega-tsumani. Some other posters have a nice outline of the possibilities. By comparison, this thing wouldn't make a dent.

Re:Pie closer to hand

[Anonymous Coward]

The paper estimates it would be doable in about ten years, if we start focusing research on it now. He is assuming we figure out how to make nanotubes a couple centimeters long, but the pace of research is awfully fast in this area, and he points to a few recent breakthroughs that suggest it may well happen.

geostationary orbits only??

[crystalplague]

well the earth rotates below the ISS and space shuttles because they remain in about the same point constantly. this means that they could never haul something up to it with a cable. their orbits would have to be geostationary, meaning the are always over the same point on earth which IIRC, takes a MUCH larger distance away from earth. also IIRC, directv satellites in geostationary orbit are 35,000km from earth.

Re:geostationary orbits only??

[kesuki]

First off 22,000 Miles is ~= 35,398 KM
So that would put it only 388 KM away from a True geosync orbit of 35,786 km. Although for counterweighting they may have to make a 23,000 mile (37,007 KM) long cable just to make it easier to hold a geosync orbit

Re:Could you imagine... Yes, I can!

[Soko]

Why stop at nuclear waste?

On the way to the sun first should be:

1. The source code and any disks containing Windows 3.11 and Win32s. Puh-leeeez! Pretty Puh-leeeeze!
2. All the AOL CDs on the planet - though that would break the damned thing, wouldn't it?
3. Hillary Rosen. (Just an elevator ride, Hil! Really!)
4. The Microsoft Marketing Department. They've made the rest of the industry go to hell, so....
5. Larry Elliston's ego. Might make the Sun go nova, so we'll have to do some calculations first.
6. Ditto for BillG, SMcNealy and SJobs.
7. All e-mail SPAM. The Internet's equivelent of nuclear waste.
8. Jon Katz stories and Cowboy Neal polls.

Did I forget everything, er, anything?

Soko

Only 20 tons?

[Junior J. Junior III]

But the weight to payload ratio sucks pretty hard. I imagine the up-front construction costs would be a lot higher than the cost of building rockets. So even if it's cheaper after, say, 10,000 uses, we might not see anyone wanting to build it.

Re:Only 20 tons?

[Rasta Prefect]

Once it's up though, we could increase the amount of stuff we could put in orbit by orders of magnitude. As one poster pointed out, we could heft Nuclear Waste up this thing and chuck it towards the sun - not something we realy want to lift out of conventional orbit on a rocket. Dirt cheap sattellites. Family vacations to orbit. Assembling something like the one-shot Mars mission would suddenly become fairly easy and considerably cheaper. Ditto for space stations. The Benefits for humanity would be immense. It would really finally open space to us in a big way.

Re:Only 20 tons?

[linzeal]

...and the state of texas can use it somehow to execute people.

Re:Only 20 tons?

[Anonymous Coward]

I want the contract for the foundation work.

Re:Only 20 tons?

[Junior J. Junior III]

20 tons is about the limit for conventional heavy lift to orbit right now, but if that's all that can be taken up at one time by what can only be described as a MASSIVE engineering project, it's going to create a pretty significant bottleneck in the long run, even if it is a considerable improvement over what we can do right now.

Re:Only 20 tons?

[WolfWithoutAClause]

If you have a project with a more or less guaranteed return on investment, people will usually lend you the money. Besides, its easily in the range that the American government can afford- they spend 10x that per year outlay on space every year.

Besides, if you build one, you can build one for other governments, cheaper than they can build one themself. So you can defray your costs by making money that way.

Re:Only 20 tons?

[Anonymous Coward]

I don't know about you, but I wouldn't want to travel on the same platform that carries spent nuclear fuel.

Re:Only 20 tons?

[kesuki]

You should have read the articles. The cost of building this beast is only equal to the cost of a Single Year of Global space launch costs. Second of all the elevator works in cloudy and even stormy weather. Something most rockets not designed to bring about the death and distruction of all humanity are capable of. And those designed to bring about the end of humanity are calculated to have an acceptable number of lost warheads should the be fired under the worst of inclement conditions.
As for the payload 20 tons of Payload is Huge! Nothing capable of carrying humans or delicate electronics can support a 20 ton payload. you're confusing the weight of the fuel with the weight of the payload. This elevator is electric and doesn't need to carry any fuel just some shielding against impacts. It could even be designed to make one-way trips with speperate rentry or to be recycled in space.
For 1-way trips it only has to average 66 miles per hour to maintain a trip every other week. That is 520 tons a year. Once they can figure out a way to bond carbon nanotubes in a strip 22,000 miles long, without comprimising strength it's a pretty safe bet that this will kill 99% of all conventional rocket traffic. Especially after more and more of these things go up.
Although consumers probably won't like a trip that takes 2 weeks to complete (1-way) so they had better figure out a way to get these things to travel 600 mph or so average (~1.7 days) just to make the trips palateable to consumers, otherwise they'll loose favor with consumers as better technology comes along.

Re:Only 20 tons?

[Anonymous Coward]

Psssst: build it with lego

Re:Only 20 tons?

[bryan1945]

Ah, but we launch maybe 3 dozen (at the most) large payloads per year? With something like the elevator we could launch maybe 1 per hour? That's nearly 9000 per year, over 5 years you have about a 44000x difference. At the proposed cost of $40 billion, then figure double it to $80 million, it comes down to about $2000 per launch. A bit better than $10,000 per pound we have now!

Re:Only 20 tons?

[cmkrnl]

Interesting concept.

Convict propelled alive off the top into space with enough momentum to take soon to be carcass away from the elevator. Clean burn up on re-entry. Reduced need for autopsy or burial. Relatives can witness the execution from the ground as the human meteorite lights the night sky up.
No need for expensive prison staff training to a basic paramedic level in order to operate the Leuchter Jab-O-Matic 9000.

Some definite advantages there. I believe NASA in Houston are starting work on a multi $Bn development program on a prototype as we speak....

Curmudgeon

Just in case some dumb gobshite takes what I said above at face value, I would recommend visiting http://www.webster.com/ and checking the meaning of the word "irony".

Re:Only 20 tons?

[Junior J. Junior III]

But if (as I'm assuming) the elevator can only support a single 20 ton payload at a time, how can you send 1 payload per hour? You'd have to find a way to move 20 tons at a rate of 22,000 mph (or was that km/h?)

Either way that's awful fast.

Re:Only 20 tons?

[markmoss]

As for the payload 20 tons of Payload is Huge! Nothing capable of carrying humans or delicate electronics can support a 20 ton payload. The shuttle was designed for a maximum of 60,000 pounds = 30 tons. However, the shuttle was also designed so that a team of thousands spends several months re-assembling it after every mission, and instead of one 30 ton load, it usually carries a number of smaller modules totalling much less than it's theoretical capacity. The beanstalk would always be hauling a load up, and the main operating cost would be the electricity to power the elevator.

How many loads a year? Assume one at a time, and speed similar to electrically powered "bullet" trains, 200km/hr (120mph). 22,000 km would take 220 hours, about ten days. So 36 "launches" and 720 tons of payload delivered a year. This probably exceeds the total payloads launched by all national and private rockets now.

Due to the lower cost, I expect there would be a considerable increase in both size and number of satellites sent up. That is, comsats now are probably around a ton, built as light as possible and limited in power because of the high per pound costs; with the beanstalk, they could afford to make them considerably larger, and to transmit at much higher power so the ground stations to pick them up could be smaller.

That will give the beanstalk a good steady revenue stream. If you want to build a 100 ton space station or interplanetary cruise ship, then you'll either have to get your five pieces in the queue right away, or else wait a few years until the waiting list for satellites on the beanstalk gets too long, so they build Beanstalk 2 with a much higher lift capacity...

Re:Only 20 tons?

[Anonymous Coward]

That's a good point that it would take a long time to climb 22,00 mile.. It is just like going around the world. I still think some kind of mag-lev rail would work the best.

Re:Only 20 tons?

[Anonymous Coward]

20 tons is just the initial payload. Given the proposed construction method (using the cable itself to lift more cable) you can scale up pretty rapidly from there. They estimate 2 years for initial construction to 20-ton capacity, and another three years to get a million kilograms capacity.

Re:Only 20 tons?

[bryan1945]

This is a good point, one which I did not catch.

But I'm still stealing your fish! :)

LOOK OUT........cable!

[Anonymous Coward]

Could this cable swing out of control at X^10 miles per hour around a city and whack it? Seems rather dangerous as we cannot even track falling debris yet be able land a moving peice of 1000+ moving parts machine on an asteroid.

D~y

The physics of collapse

[sterno]

Has anybody really sat down and worked out the physics of this thing if it were to collapse? How would the atmosphere effect it? How much of the structure would burn up? Most of the models for something colliding with the earth involve something that is one contained piece of mass. How does a big long rope like mass react during a similar collision?

Re:The physics of collapse

[lkeagle]

I promise you the physics of such a collapse has been worked out in enormous detail. A rope-like mass is usually thought of as an infinite string of coupled rigid bodies. You're never gonna get any exact analytical expressions for how a rope is going to behave under those circumstances, but you can definitely predict its behaviour.

I would imagine that any part of the rope above a certain altitude would burn up before impact. However, I would not worry much about huge destruction, as the majority of the rope would simply pile itself (relatively) peacefully at it's base. You can calculate how long it would take an object (say, the top of the rope) to fall to the earth (it's actually a tricky problem, as the bottom of the rope may have a slightly larger pull gravity, and will pull the top of the rope faster than it might fall on its own). In that time, you can easily tell how much distance the earth has moved beneath the falling rope, and therefore determine the field of damage.

Unless you expect the rope to take an entire day to fall (which I can't see happening), then there's no way it could wrap itself around the earth. The mass of the entire rope may be significant, but even if it all did hit the ground at the same time, because it's spread out along a huge length it is very unlikely that it will cause any significant damage (i.e. no tsunamis...).

~Loren

Re:The physics of collapse

[Bill Currie]

Yes, I did, but simplifying things. I assumed the cable had somehow been shattered into small enough chunks that I could treat them as point masses, neglected the moon, sun and other bodies (mind you, for this they're negligable anyway), and worked out the near point (perigee? I never remember which is which between perigee and apogee) for the orbit of an object starting at the appropriate velocity for its height along the cable. I decided that any near point above the atmosphere would cause its orbit to be thrown out as `safe' and any below as potentially dangerous (due to burning up, it might still be safe). I chose somewhere between 90 and 100 (150?) km because I know that the space shuttle has stayed up at that altitude long enough that if it was a dangerous object, something could potentially be done about it. I assumed that anything that came below that mark would make a mess. My solution for the minum safe height was somewhere between 25-30 000 km.

I didn't do any math for the damage caused by pieces below that mark, but my guess is that anything below a few km wouldn't be any worse than dropping a WWII bomb and the resulting damage would be very localized. between that and several thousand km, the chunks would fall into the water (assuming the builders were smart enough to build close to a coastline on the correct side:). There would be a region above those thousands of km where the chunks would be a bit more of a worry, but above that, they're likely to burn up when they hit the atmosphere.

Beyond all that, buggered if I know :)

Re:The physics of collapse

[speederaser]

...the majority of the rope would simply pile itself (relatively) peacefully at it's base

Sorry, no. The collapse of one of these things will be anything but peaceful.

Here's why. The radial velocity at all points of the elevator is the same, but the distance from the center of rotation (center of the earth) varies quite a bit. Assuming the bottom is at the equator, it will have a lateral velocity the same as the earth's surface, about 1040mph towards the east. The center of gravity of the elevator is positioned 22,241 miles up in geosynchronous orbit, where its lateral velocity is around 6860mph towards the east.

That means every part below a break has a higher lateral velocity than the part below it. There is nothing in space to slow the eastward velocity as the piece accelerates toward the earth, so it wraps around the earth towards the east.

Here's another way to think of it - the c.g. of the elevator is orbiting the earth at the exact speed necessary to maintain altitude. If there is a break the part below the break suddenly has a new c.g. closer to the earth, where the speed required to stay in orbit is higher than before and the speed of the part is lower than even what's required to stay in geosynchronous orbit. So the piece de-orbits like Skylab or Mir or any other space vehicle, to the east.

Re:The physics of collapse

[ZigMonty]

The spot they picked in New Scientist (maybe sciam?) was on the equator south of India. Naturally it would be an artificial structure (think big oil rig). Lots of empty ocean to fall in. Don't know about tsunamis though.

Re:The physics of collapse

[buckrogers]

Let's say that it is a calm day, absolutely no wind, and I am floating in hydrogen ballon 10 miles above the ground.

If I drop an egg or an anvil those things will fall strait down to the ground. If I hang a string down to the ground and then let go of the string, then it will also fall strait to the ground.

If I could magically float 100 miles off the ground over the same spot then if I dropped an anvil or an egg or a string, then they will also fall strait to the ground.

If you cut one of these elevators at a point below that which centrifical force can hold it up, it would fall strait to the ground. It would be a huge tangle of filliment where the station used to be.

Re:The physics of collapse

[An Onerous Coward]

If I understand your analysis correctly, you've made a couple of very important errors.

First, unless there's a mechanism built into the cable for shattering it in an emergency, then you can't treat each bit of the cable as a separate point mass. Each piece of cable is connected to each other piece of cable (very tightly, in fact. These are carbon nanotubes we're talking about).

Second, you say that anything above low-earth orbit will be "safe." If only that were the case. In fact, in order to keep the elevator as a single unit, anything below geosynchronous orbit (about 22,000 miles, if I remember) has to be traveling slower than it would if it were freely in orbit. For instance, the Space Shuttle orbits the planet every nineteen minutes, while the elevator at the same height is orbiting every 24 hours. So the bits of elevator from that height are going to fall.

It turns out that anything below the breakpoint is going to fall to Earth, while everything above the break is going to float off into the aether. Since you're dealing with 22,000 miles of cable, it's going to wrap almost fully around the equator. Given the amount of potential energy stored at the top of the cable, some serious damage would result towards the end of its fall.

Re:The physics of collapse

[Anonymous Coward]

No, you aren't actually correct. Read the parent post very carefully. I think you could get an idea of this by sitting in the middle of a merry-go-round and rolling a ball toward the edge. try to hit a target at the edge. although this isn't the same, it gives you an idea of what happens when stuff rotates.

Re:The physics of collapse

[automatic_jack]

"I never remember which is which between perigee and apogee."

Remember Apogee Games? Makers of classics as Duke Nukem, etc? Well, if they were at their lowest point, those games would have sucked a lot more than they did. That's how I remember the difference :)

Re:The physics of collapse

[Anonymous Coward]

Yes, actually, the author of the paper worked it out. He recommends using an epoxy with a low melting point, so if you get a high break the cable disintegrates in the atmosphere before it hits the ground. All you get is a bunch of 3-cm nanotubes drifting to earth. Only the lowest 400 to 4000 km of cable would remain intact, and that's going to hit with a lot less energy than the upper sections would. The minimum-size cable (20 ton lift) is small, and it's a thin ribbon, not a round cable, so it'll catch a lot of air

Playing Devil's [Luddite's] Advocate

[kisrael]

Ok, let's say that the destruction aspect of the tower isn't an issue, that the way this thing works means it could collapse in a (relatively) harmless way. I'm a little concerned with the whole idea of cheaply and easily getting things into orbit. Maybe I've read too much post-appocalypse Cyberpunk (spefically one of the stories in "mirrorshades") but it seems like there needs to be a *large* amount of regulation with what goes, because of what might be coming down... (like huge quantities of EMF blowing out pretty much everything electronic...)

Re:Playing Devil's [Luddite's] Advocate

[jo42]

Imagine the disaster a 22,000 mile long cable would cause if it ever fell back to Earth. No thank you.

Elevator music?

[ocie]

I'd imagine that they would have to do an elevator music version of 'the ring cycle' or something for such a long trip.

Re:Elevator music?

[crystalplague]

nope...Stairway (Cableway?) to Heaven.

Music?

[Slugsta]

I'm thinking that the only appropriate elevator music to play during the duration of the trip would be Jefferson Airplane/Starship

Re:Music?

[Anonymous Coward]

Well, kiss the tourist trade goodbye then

Re:Could you imagine... Yes, I can!

[Graymalkin]

9. Linux users. Puh-leeeze!

Saving some cable...

[toby360]

I hope I don't get modded down for this idea like I always do but here it goes anyways..
I've read several books which include the idea of a space elevator, and one of the key problems had to do with bringing that much cable to space, and the strength of the cable to stay together. The closer the cable gets to earth the harder the pull, the further out the "satellite" holding the cable in geo-synchronous orbit has to be. Instead of bringing the cable down to earth.. or putting it atop a very high tower, why not create a platform 50-80,000 feet up for planes to land on. This would save very large amounts of cable from being created, the satellite wouldn't have to be nearly as far out either to compensate for the gravitational pull from the cable below. Also, to compensate for the excess weight of the aircraft and payload while landing, the satellite holding the cable could move up and down to balance any weight added or removed to the cable.
Now, having a shortend cable would have added benefits too, in the event of a disaster, normally a cable attached to the earth would wrap around the planet several times causing an incredible amount of destruction. This could be minimized with my platform idea. Imagine something colliding with the cable causing immenant failure... why not create sections in the cable to automatically break off in the event of a disaster, this would minimize the amount of cable falling to earth, and the remaining cable would be either ejected into space, or depending on how an object hit, its possible the upper section could re-establish a geo-syncronous orbit after losing much of the cable.
Any pysicists out there able to agree/disagree with this? The tether would also most likely have to be conical in shape, thicker higher up, and thinner below to minimize the amount of carbon tubing used in the elevator.

Re:Saving some cable...

[Cryogenes]

Instead of bringing the cable down to earth.. or putting it atop a very high tower, why not create a platform 50-80,000 feet up for planes to land on. This would save very large amounts of cable from being created, the satellite wouldn't have to be nearly as far out either to compensate for the gravitational pull from the cable below.

Maybe you got confused my the measurement units? 50,000 feet is less than 0.1% of 22,000 km.

Re:Saving some cable...

[brunes69]

Thats a good idea, but... How do you purpose to keep the platform suspended? Is it hanging "off" the satelite? If so, won't its weight drag the satelite into a lower orbit, eventually destroying it? Or is the satelite going to be continuously firing retro-rockets, which would need enormous amounts of fuel, thereby negating the purpose of the elevator? Not to mention the wind blowing said platform around.

Re:Saving some cable...

[toby360]

That measurement is based on a cylindrical shaped cable. A conical cable would require far less cabling. A cylindrical cable would require a huge amount of ballast at the other end. Well over doubling the length (4-5x). Also, this does not take into account the possiblity of using a large near earth asteroid as "counterbalance". Saving a small amount of mass close to earth will save massive amounts of ballast many kilometres up.

Re:Saving some cable...

[Have Blue]

One objection: Stability. The Earth is a basically immovable object as far as the cable is concerned, so tying it to the ground will ensure that it doesn't move. Putting it in the ocean is also pretty good. But air? There's little to push against. Also, there's the weight issue: I don't think even carbon nanotubes could support an entire airport, which would be a very difficult airport to design because of its single support point ("Would all passengers over 100 kg please move to the south side of the terminal?")

Re:Saving some cable...

[toby360]

The centrifugal force of an orbiting satellite would compensate for any pull from cable below. In the original NASA idea, ideally it would be the best case scenario if the entire weight of the cable was supported in geosynchronous orbit. This means that at the base of the structure there would be very little force pulling either up or down on the cable, since it would "support" its self.

Re:Saving some cable...

[ender81b]

Not a physical reason why you shouldn't do this but an economic one.

The whole point of a space elevator is to get out of Earth's 'gravity well' cheaply. Nothing, and I mean nothing (well besides transporters) is as cheap as a space elevator (once you recoup building costs that is). Also, nothing is as safe as a space elevator (relatively speaking - as long as it doesn't come down on you).

Now for your scheme to build a 60-80km high tower consider how much money you would save. Virtually none. The platform isn't high enough to seriously affect a 'planes' carrying weight (at least not any more than a spacecraft or a Scram/Ram - jet powered spaceplane.

Simply put the benefits in a tower of that size can be more easily realized with two-stage to orbit spaceplanes or Scram or Ram jets.
Various Soviet Spaceplanets

Re:Saving some cable...

[cpt kangarooski]

Yeah, it'd hang at the end of the cable.

However, it's not a great efficiency saver -- now you have to pay to get stuff from the ground to the platform, and given that the cable length is about 22-44 THOUSAND kilometers, a few tens of thousands of feet ain't much.

As for the cable itself, it has to be built in space, and it is slowly lowered down. It likely stays pretty stable, given the overall mass of the thing up in space.

Re:Saving some cable...

[wildsurf]

why not create a platform 50-80,000 feet up for planes to land on. This would save very large amounts of cable from being created

Um, 50-80,000 feet is utterly insignificant compared to the the total length of the cable, like one part in a thousand. You wouldn't be saving much of anything doing it this way. And the beauty of carbon nanotubes is that they are SO strong, the cable could get away with being quite thin, probably thin enough that most parts would burn up in the atmosphere on reentry. (Especially if the tether were composed of bundles of separate nanotube fibers, surrounded by a coating of ordinary material to hold them together. If the coating burns off in the atmosphere, the fibers fly apart and disintegrate almost instantly.)

Re:Saving some cable...

[Anonymous Coward]

Ah yes, I can see why they'd mod you down for this. Dipshit.

Re:Saving some cable...

[zenyu]

Instead of bringing the cable down to earth.. or putting it atop a very high tower, why not create a platform 50-80,000 feet up for planes to land on.

I think this is a good idea, but... Planes go really fast at high altitudes... The airstrip might have to be a mile long even if it had cables to catch the planes and slow them down (it would need this anyway since the planes are both light and have very little drag at those altitudes.)

I think the weight wouldn't be a problem since you are holding up much less mass and at a lower gravity.. It might need active control since the airfield is basically a wing and a light and airodynamic one at that if you design it properly. You'd need to keep your angle of attack close to zero. Since you need all this control anyway you could just use the wing/airfield to control orbit and location...

The tether would also most likely have to be conical in shape, thicker higher up, and thinner below to minimize the amount of carbon tubing used in the elevator.
Well the cable that goes from the earth to orbit would need to be thin at the top and bottom, thick somewhere in the middle. The cable is actually part of the ballast so higher up it's not holding up the entire weight of the cable, and near the earth it's not holding much at all, but it needs some strength because air is heavy and tends to blow fiercely.

With your design it might be conical near the platform and get thinner as it goes higher, or have a fat in the "middle" profile, depending on the weight(no I didn't mean mass) of the cable.

I really think we'll have a rocket on plane solution long before the elevator, but the idea has it's charm.

I haven't read the article

[Anonymous Coward]

But the blurb does say a 22,000 mile long cable.

This Won't work - They forgot the taper factor

[szyzyg]

One big issue they missed is the fact that a carbon nanotube cable still isn't strong enough to support it's own weight without tapering the cable correctly, at the middle it has to be about 10 times thicker because the stresser are highest at geostationary orbit.

The deployment method they're using doesn't take account of the fact that you need the thickest part to always be at the middle - if you simply unroll it the way they suggest then the incorrect thickness profile will result in the cable exceeding it's breaking point and snapping.

What they need to do is unfurl a cable like this from geostationary orbit simultaneously up and down at the same time. The Mechanism to do this would have to be very delicate at unfurling the last kink or the cable will again snap.

The cool thing about this is if you figure out what kind of weight you want the cable to support then you can come up with an idea of the amount of energy stored in the tension. If the cable snapped at any point then the amount of energy released would be pretty phenomenal. From each end of the snap you'd generate a compression wave which would get stronger as it travelled along the cable, after a while of picking up energy it may turn into a shockwave and snap the cable again (essentially shattering the cable). If it doesn't then the wave will have energy equivalent to nuclear weapons when it reaches the endpoints and the waves transmit themselves into the supporting structure....

Re:This Won't work - They forgot the taper factor

[Utoxin]

Did you read the article? They aren't unfurling it all at once. They put up one strand of the cable with a shuttle, or something similar, then they use tiny robotic climbers to carry up one more strand at a time, and epoxy the new strand onto the old one.

Re:This Won't work - They forgot the taper factor

[wildsurf]

If it doesn't then the wave will have energy equivalent to nuclear weapons when it reaches the endpoints and the waves transmit themselves into the supporting structure....

On the bottom end, the atmosphere should absorb quite a bit of this energy before the shock wave hits the ground station. And on the top end, since the cable gets thicker as you go up, there should be less of a whiplike effect, I would imagine. In any case, the nuclear-weapons-equivalent energy is distributed over such a tremendous area (or distance), it probably wouldn't be too catastrophic at any one spot. Or am I missing something?

Re:This Won't work - They forgot the taper factor

[szyzyg]

THe Cable is thickest at geostationary altitude and thinnest at the anchor points, so the wave will actually concentrate as it propagates. It's like a detonation wave in explosives - the wave is powered as it passes through the material

Re:This Won't work - They forgot the taper factor

[szyzyg]

The main problem is deploying the first strand, their design doesn't balance the stresses out, so the cable will break. Later deployment must carry the cable to be deployed on a drum - they can't pull it up behind it. So I'm not sure if they can get away with the weight budget when you factor in a deployment vehicle.

Re:This Won't work - They forgot the taper factor

[Anonymous Coward]

You still haven't bothered to read the article, have you?

So many armchair quarterbacks, too many armchairs...

Re:Could you imagine... Yes, I can!

[Anonymous Coward]

Only yourself, you space-wasting karma-whoring unfunny dickhead.

Fire is DANGEROUS - STOP THE FIRE ....

[GMac]

Oh, please, go back to your caves and freeze to death why don't you!

You do realize we HAVE to leave earth or we die here! What, you think the Sun is going to burn forever? Long before that, we will get hammered by some multi km asteroid that will barbecue most of life here anyhow! Wake up, get your act in gear, it's time to colonize space while we still can.

The solution to this problem is also simple. Each piece needs to be aerodynamic anyhow, so add some flight control surfaces so it can "fly" apart under control...

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Suicyco]

Well.. Yeah but you are talking hundreds of millions of years. I'd think that even if we don't do this in the next 10,000 years, we will still eventually colonize space. Its not like we have to plan for escaping the earth any time soon, not even geologically soon.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Anonymous Coward]

You sir, are a very wise man. You should apply to NASA.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[goonies]

YES! Lets pollute this planet some more and then just go to the next one... we'll sure find some asteroid to blame...! ;)

Re:Fire is DANGEROUS - STOP THE FIRE ....

[curunir]

Whoah there...we've still got a couple of third-world countries left that we can dump in. Let's not go getting hasty with the whole "space" thing just yet...

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Danse]

We've already had several close calls with asteroids, and those are just the ones we know about. I probably won't be very long before a really big one is right on target.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Gaijinator]

Basic probability states that something not happening for a while doesn't make it any more likely to happen in the future. Close only counts in horseshoes*.

* (Well, it counts in a few other things, too)

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Bill Currie]

I wasn't clear enough. I'm not against a space elevator. I was just trying to point out an interesting factoid about what would happen if it somehow got shattered into lots of (relatively) itty bitty bits. I was actually trying to point out that I don't believe a space elevator would be as dangerous as many think.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Pig Hogger]

You do realize we HAVE to leave earth or we die here!

Earth is the cradle of mankind.
It is by leaving the cradle that one can devellop.

Konstantin Edouardovich Tsiolkowsky.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Danse]

Yes, but roll the dice for a long enough period of time, and you will eventually roll snakeyes. The probability is the same for each roll, but you gotta figure in the time factor.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[shoez]

That is what statistics and the post you are replying to argues against. just as there is no guarantee that we will never be hit by an asteriod, there is no guarantee that we eventually will. But, yes, it is irrisposible to not take precautions(but we do).

Re:Fire is DANGEROUS - STOP THE FIRE ....

[shoez]

What a load of shit. You think that the previous 3000000 years were worth nothing at all? What do you expect to find in the universe that is so superior than the benefits of quality introspection? Aliens? Don't make your life into AI, that movie sucked.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Anonymous Coward]

Ah, for me I generally prefer to take my dumps in a civilized country, much less a truck stop! Much cleaner, less _Deliverance_ action.

Re:Fire is DANGEROUS - STOP THE FIRE ....

[Anonymous Coward]

You do realize we HAVE to leave earth or we die here!

Yes, and when we go into space, we will die there. Everything perishes. Get over it.

Re:Could you imagine... Yes, I can!

[ryusen]

i thought we were talking about things that might make a difference (mass wise) like larry's ego... even if you get rid of all the linux users i don't think it will make the earth as spacious as we get rid of elison/jobs/mcnealy/gates egos...
*picks up fire retardent suit*

For a really good example of space elevators...

[devphil]

...or "beanstalks" as the insiders like to call them, read the scifi/humor novel Rainbow Mars by Niven. It features beanstalks in many places, including what happens when one pulls loose from Brazil.

Re:For a really good example of space elevators...

[shoez]

The beanstalk is the tube, not the result of the tube crashing to earth. Learn to read.

Re:For a really good example of space elevators...

[martyn s]

Maybe you should learn to read the subject line: "For a really good example of space elevators...or beanstalks as the insiders like to call them..." I think he was calling the space elevators beanstalks, not the tsunamis. Learn to read.

Bubblegum Crisis 2040

[DarkZero]

If you'd like to see a surprisingly realistic sci-fi version of this, I suggest you take a look at Bubblegum Crisis 2040, an anime series that most geeks would really enjoy anyway, even if just for the interesting sci-fi ideas and the references to American sci-fi movies like Blade Runner and Alien.

Re:Bubblegum Crisis 2040

[fifthchild]

Not to mention the often scantily-clad females. Plus, you gotta love the fact their hard-suits have high heels on them.

I don't know about 'surprisingly realistic', however. What Dark's talking about is the Space Umbrella and Sky Hook -- the former is a huge solar power station in space and the latter is the cable/elevator that joins it to Tokyo. It's cool and all, but...

All this talk reminds me of the Star Ladder and Space Ladder wonders in Civilization Call To Power and Alpha Centauri. I don't remember which was in which, but the ideas were there. One worked with the help of super prehensile solids, aka material capable of holding millions of times it's own weight. The other relied on 'smart metal' that could re-model itself if it had to move, that sort of thing. Just feel free to correct me if I'm wrong.

And check out Bubblegum Crisis, not only the newer Tokyo 2040 but the series it was based on, Tokyo 2020.

First Elevators...

[MrWinkey]

I think I would be slightly worried about this being slightly like the first elevators. I mean they were not always as fail safe as they are today. I dont think I would like to ride on the first one.

Dirt-cheap interplanetary travel

[QuickFox]

With one slingshot on Earth, another on the moon, another on Mars, another on one of Jupiter's moons... We'd get any amount of dirt-cheap super-fast interplanetary travel! Tourism, astronomical observatories, mining, exploration...

Book me on a trip to Ganymede! Book me now!

Give a man a fish and he eats for one day. Teach him how to fish, and though he'll eat for a lifetime, he'll call you a miser for not giving him your fish.

Could be made safe with nanotech

[Suicyco]

Something like this wouldn't be built for at least 20 years from now. By then simple nanomachines should be available, since much of the construction of this would probably be done at a nanoscale. If there were swarms of nanomachines all up and down the cable and if they were made to detect any abnormalities in the structural integrity of the elevator, they could simply deconstruct it. Billions of micron length strands of bucky tubes should not have that much of an impact on the ground due to friction in the atmosphere. It would simply be dust particles floating around. I'd think the deconstruction of the cable could be done in a relatively short amount of time as well. The only problem with this would be false alarms, but then again with that kind of technology it wouldn't take too long to reconstruct a new cable.

Just some thought anyway..

Atomic Train (NBC)

[coyote-san]

This reminds me of a comment my parents made after taping Atomic Train (NBC) for me since NBC felt Coloradans were too feeble-minded to deal with the plot.

A train containing an atomic (not thermonuclear) bomb crashes in the mountains 40 miles west of Denver. It detonates! What would I do?

I told my mom I would go outside to watch. An atomic detonation at 40 miles away doesn't bother me. An accident at Rocky Flats (5 miles south) when it was operational is a bit worrisome, but not a fission explosion 40 miles away with several mountain ranges between us. Even a thermonuclear explosion at that range is not the instant death portrayed in that movie.

The point is that nuclear weapons, as destructive as they are, are still largely local events. The cable smacking into the equatorial oceans would dump a lot of energy into the water, but that energy would be spread across coastlines worldwide. Millions may still die, but not billions. And that risk may well be considered acceptable if the alternatives are far worse.

Re:Atomic Train (NBC)

[Pig Hogger]

A train containing an atomic (not thermonuclear) bomb crashes in the mountains 40 miles west of Denver. It detonates!

Utter bullshit. Mechanical impact will not detonate an atomic/thermonuclear bomb.

Did you know that an atomic bomb blew up in an airforce base near San-Francisco during the Corean war, killing one general, when the B-36 bomber that carried it crashed on take-off?

The nuclear explosion is dependent on the extremely precise timing of the detonation of dozens of classic explosive charges. If the timing is slightly out of what (by mere femtoseconds), it will "fizzle" but not detonate.

And the number of safeties in the detonator "mechanism" is so awfully high that it's a wonder the things ever detonate!

So, the cinematic notion that a bomb explodes in a train crash (both in the US and in Russia*) is laughable at best, and a bad joke at worst.

-----

* What was the name of that stupid movie, anyways? You know the one where a balkan diplomat smuggles an atomic bomb detonator in the U.N. building in New-York ?

Re:Atomic Train (NBC)

[Anonymous Coward]

Just wondering- what is this "Corean War"? Is it just as fictional as this "atomic bomb [that] blew up in an airforce base near San-Francisco"?

I forget the name of the movie, but it had George Clooney and Nicole Kidman in it. It came out in the late 90's, check IMDB.

Re:Atomic Train (NBC)

[dossen]

The Peacemaker? Been a while, but wasn't the bomb in that one set off using it's detonator (or some kind of bypass circuit)?

Re:Atomic Train (NBC)

[Anonymous Coward]

And that risk may well be considered acceptable if the alternatives are far worse.

Yeah, like being stuck on this miserable planet forever.

Re:Fuck you all

[Anonymous Coward]

hahahah aol its teh coolest isn't it!!! every1 i know is online!!!!!!1 it's so coo0o0o0ol!!

Even further OT...

[Embedded Geek]

Doh! Forgot about the Dream Park novels from Niven.

Does anyone remember if Niven used a space elevator in Rainbow Mars? I think he actually had an honest to goodness giant beanstalk, but I can't remember of it actually reached orbital space.

Re:Even further OT...

[Fesh]

The concept in Rainbow Mars was a pinwheel, not a space elevator. The difference is that instead of having the cable just hang there, it instead rotates around its center of mass. However, you weren't far off thinking about the Dream Park novels. You're probably thinking of another novel he did with Steven Barnes, Descent of Anansi. In that book, a space shuttle trapped in orbit with nothing going for it but a cargo pod containing a spool of "Sinclair molecule chain" manages to engineer manages to engineer its reentry by connecting the shuttle to the pod using the cable and letting the cable spool out. I'm not clear on the physics, but it was something about the shuttle dropping into a lower orbit while the pod ascended into a higher one.

Re:Even further OT...

[Have Blue]

I'm pretty sure the Rainbow Mars elevator was fixed in place. It was destroyed when terrorists severed it from the (large) satellite used as a counterweight, destabilizing its orbit.

Re:Even further OT...

[RedWizzard]

Was Rainbow Mars the one he wrote with the space elevator trees?

Thanks...I'm about 2/3 through Red Mars

[Anonymous Coward]

Thanks for spoiling it, I'm not at the point where they build it yet - just talk about it.

Re:Thanks...I'm about 2/3 through Red Mars

[SilentOne]

Stick with it. The books are more a commentary about the social-political structure that may come out of the world that is today, with some cool Mars problems put in.

Like most good science fiction, there is substance beneath the gadgets and the like.

(But if you're almost throught the first one, then you probably know that already)

This is absurd

[Anonymous Coward]

They should just work on improving 802.11's range. Running a cable into space... Geez, the things we'll do to get Internet access to remote locations.

Dams *have* changed length of earth's days

[coyote-san]

Actually, there's strong evidence that the number of large dams constructed over the last few decades have changed the length of the earth's days. Not by a huge amount, but I think it has started to affect the introduction of leap seconds.

(The main reason the earth is slowing down, IIRC, is the tidal forces from the moon and sun. If the moon was gravitationally bound to the earth it would be falling, but since it's not it's slowly drifting away.)

Re:Dams *have* changed length of earth's days

[dgroskind]

...I think it has started to affect the introduction of leap seconds

Not likely. The proponent of this theory, Benjamin Fong Chao, a geophysicist at the Goddard Flight Center, estimates that dams have increased the earth's rotation by 8 millionths of a second over 24 hours in the last 40 years.

There were 22 leap seconds added in the 27 years before 1999. The Earth runs roughly 2 milliseconds per day behind a 24 hour atomic clock.

Re:Dams *have* changed length of earth's days

[coyote-san]

Well... I recall reading somewhere that the pattern of leap seconds was off from what was expected. Any theories on the cause, or did some reporter just get confused?

Re:Dams *have* changed length of earth's days

[dgroskind]

Any theories on the cause...

I vote for global warming. Since El Niño measurably slowed the earth's rotation, other wholesale redistributions of the Earth's airmass should have pronounced effects.

Issues that come to mind.

[NoMoreNicksLeft]

#1 Holy rollers calling it the new "Tower of Babel".

#2 Balancing this thing so that it doesn't wobble. For every pound that goes upward, we need approximately as much going down, right?

#3 Can we sit a free floating space station just a few hundred yards outside of it?

#4 If we can do that, can we build a bridge to it (of course, you'd need to do this in both directions) ?

#5 If the bridges get long enough, could they meet up with another strategically placed beanstalk?

#6 Could we wrap a bridge around the entire earth?

Just a few brain teasers... Oh, and another thing. Getting solar power safely to earth from orbit, is currently a problem. Beaming megawatts down to a basestation via microwaves is sorta nasty. But with this, we could just run an electrical line. Cool, huh?

Re:Issues that come to mind.

[Ungrounded Lightning]

#2 Balancing this thing so that it doesn't wobble. For every pound that goes upward, we need approximately as much going down, right?

No. (See my previous post. You just need to have the center of gravity a bit high and be careful about how fast you go up at any moment.)

#3 Can we sit a free floating space station just a few hundred yards outside of it?

Yes, at the geosynchronous level. (Though climbing and lowering loads will move the tether forward and backward a LONG way as they are moving up and down.)

#4 If we can do that, can we build a bridge to it (of course, you'd need to do this in both directions) ?

Yes. But if you connect them your satellite will move forward and backward as the tether is displaced by payloads moving up and down. Or else your bridge will fold up.

#5 If the bridges get long enough, could they meet up with another strategically placed beanstalk?

Yep. But this is REALLY long. (Of course it also lets you have a "slip joint" so each tether can "slide along" the bridge.)

And be careful about stability: A long thin object in orbit is in an energy valley when pointing along the line to the primary and on a ridge when at right angles to it. You need active compensation or you lose your orientation the first time anybody scratches his nose.

#6 Could we wrap a bridge around the entire earth?

Now that's REALLY long. Yes you could. But now the instability gets worse and quickly breaks up your ring or crashes it into the primary. (See "The Ringworld Engineers" by Larry Niven.)

i know where its going...

[deft]

someone wrote "Because if it fell down, it'd be about as destructive as a thermonuclear bomb (kinetic energy's a bitch). And NOBODY would want this in their back yard after 9/11.

On the moon, Mars, any other sparsely-populated/unpopulated body in the solar system? Sure. But not here."

I think the line for the elevator's going to start in afghanistan. noones going after it then...

4 problems I see with the idea...

[Papineau]

Can't read the PDF yet (downloading it), but there's three problems I can spot right away:

• One of the problems I can see is the thermal expansion and contraction due to the temperature gradient between night and day. With the length (36000 km), even a very small expansion would result in a very long difference. Say it's alpha=1e-6 and delT=100K, it's still 3.6km! Where do you put the extra length? In the ocean?
• Also, another point to keep in mind is that with such a temperature gradient between one end and the other one, it can act as a giant heat pump. At night, heat will be pumped out of the globe, probably enough to freeze the water vapour around it. During the day, it would probably radiate so much heat that it would be dangerous to approach it.
• How do you manage for the movement of the satellite? It cannot be completely compensated through the movement of the base.
• Pressure from the wind (drag). Even if the satellite is geostationnary, it doesn't mean that there's no wind around the base. Actually, with the length and the size of it, there'll be quite a drag on the lower part (assuming the majority is out of the atmosphere).

Re:4 problems I see with the idea...

[oregon]

"Where do you put the extra length? In the ocean? "

The other end is in orbit, it can easily move nearer or further the earth

big ass target

[Anonymous Coward]

... and you thought the Trade Center was a fun target for hijacked terrorist airplanes.

MP3 Interview...

[BMazurek]

The CBC Radio science program, Quirks and Quarks had an article about the space elevator on November 3rd, 2001. An MP3 of the article is available. Check it out!

StairWay to Heaven?

[bobobobo]

Wonder if Led Zepellin might try suing...

...Or you can imagine a static charge build up

[broter]

IANAP (I am not a physicist), but suppose various non-carbon dust/debris attatched to the cable, down in the low end of the atmosphere. Now imaging that the elevator spread these out over the length of the cable. Now suppose high winds created a charge on the cable that spread along the portion that had foreign materials on it.

I haven't worked out the math, but wouldn't this put a force on both the satellite and the anchor? I'm sure this could be calculated into the tol. of the cable. What about keeping the satillite in position? Would you need to extend the cable out beyond it and charge it on purpose to keep it in orbit?

Since the charge would be small, it won't have to be much, but couldn't it cause a variable drag on the satillite as it moves through the light and dark side of the earth rel. to the Sun (think magnetosphere)?

I'm a mathematician, not a physicist or planetary scientist. CAn anyone add to this?

-RB

Re:First post...

[Anonymous Coward]

Wow, that was rather funny, shame the pratt that moderated it had no sense of humour.

Fun things to try

[WillSeattle]

Bungee jumping off the Space Elevator

Hacking the Space Elevator "this is the down signal"

Getting Greenpeace to fly a very large flag from the Space Elevator "better than a smokestack"

Getting a bunch of friends to ride up with you and all sway together so it rocks ... woah!

Tossing pennies over the railings and watching them burn up on reentry

Paragliding from the space elevator

Paragliding onto the space elevator (not for the faint of heart)

Downloading images from the Space Elevator Coffee Pot webcam

Taking a dump - has to go somewhere ...

-

Re:this is scary

[confucio-licious]

this was not offtopic. Now I know slashdots' REAL agenda....completely run by spooks.

Why, when I was your age....!

[coyote-san]

I was just out of college (iirc) when the first popular discussion of beanstalks came out (Charles Sheffield, in some long-dead Baen book-zine).

The numbers were so ludicrious that he repeatedly apologized for wasting our time. Of course this was a flight of fancy, the numbers were orders of magnitude larger than the strongest known materials. Yet, if "ultronium" could be developed from some exotic material....

Then buckyballs were discovered. Then buckytubes.

The fact that this is even "just" possible with known materials less than 20 years later is mindblowing. I can only compare it to the confident RSA predictions in Scientific American (which I also remember when it first appeared) that RSA-128 would take millions of years to crack. We all know how well that prediction held up.

Given this perspective, I don't think it's unreasonable for NASA to spend some serious money considering its options if/when stronger materials become available. It's easier to believe that even stronger materials will be discovered (e.g., perhaps by putting foreign elements within the tubes to manipulate quantum properties) than that we've suddenly hit the ultimate barrier.

and the people in them?

[athagon]

Yeah, sounds great. You think standing in an elevator to go up 10 floors to your job is bad..just picture this:

You're in the space elevator. Along with Sir Flatulent, Miz CoughsALot, Mr. IForgotToPutOnDeoderant, and Ms IHaveTheFlu. Sounds great. For 22,000 miles. :P

Stuck between floors?

[Cruciform]

Argh! Damn elevator! Here, let me pry open that door so we can climb---" (Big sucking noise)

Tower of Babel.

[BRO_HAM]

Ironic of you to think of that. I was thinking the same thing, and how "dubya" would mark it as an attempt at social terrorism on america. An axis of evil's attempt to "confound our tongues", and "confuse us into defeat". I can really picture dubya warning the public about this through the idiot-box while all the hicks who voted for him sit there cleaning their guns, drooling in awe. The sad thing is, we're not to far from that.

Correction...

[Kymermosst]

I meant to insert "the apparent centrifugal force caused by the inertia of the cable due to", but hit submit before I did that.

A.C. Clarke OWNS the location where they'd put it

[Anonymous Coward]

Last I checked, Sri Lanka, the location of Clarke's home, is where they'd put the tether for this sort of operation.

think smaller

[BlueboyX]

You have the right idea, but didn't take it far enough.

If this did go down in the water, and it released the power of a nuke (or two or three) it would not produce a tsunami big enough to bug people living on the coasts. The order of magnitude simply is not the same. Think about the vast amounts of mass in the form of water that we are talking about moving; the US and Russia have conducted many nuclear bomb tests without killing millions of people in floods.

You may want to think about it another way. A clip commonly used in nuke documentories shows a test of a nuke on several old naval ships. During the whole clip, there are no truely huge waves created.Even several times the power of that nuke won't produce waves of sufficient size to make it from in the middle of nowhere to a coast.

Never happen

[John Jorsett]

People go nuts when you suggest building a new nuclear reactor. What do you think would happen if you tell them you're going to multiply the potential destructive consequences of that by many fold, and suspend it over their heads? And the potential for an accident pales in insignificance if you consider how attractive a target it would make for someone to take down on purpose. I'm as big a techno-freak as anyone (hey, bring on those nukes, we need the power), but this would worry even me.

An article about this from August 1979

[marko123]

A sci-fi/sci-fact magazine in paperback form called Destinies had a story about this in their Aug-Sept 1979 edition. The story was called "How to Build a Beanstalk" by Charles Sheffield. He did some research into the material strength required, and to get the stalk to reach down to earth, or somewhere near it required a material with a tensile strength of 2 000 000 kg/cm^2, which was 10 times the current known tensile strength of known materials at the time.

"Beanstalks, originally called skyhooks, are an idea of the 1960's whose time may at last have come. They are used as important elements of at least two novels published in 1979, Authur Clarke's 'The Fountains of Paradise' and my own 'The Web Between Two Worlds' "

chicken or the egg

[GunFodder]

True, but we would need some way to get a construction crew and materials to Mars first. We need some cheap way to ship massive amounts of stuff off of Earth. There must be some way to cheaply escape Earth gravity...

Re:chicken or the egg

[RedWizzard]

The idea would be to send mining and manufacturing equipment and set up some sort of mars base. Once you've got everything right on Mars then you look at building one on Earth.

Nope, doesn't work (yet)

[WolfWithoutAClause]

I've read this paper in full, a couple of months back. According to the paper the actual, demonstrated strength of the carbon tethers is only as strong as Kevlar- it's about 1/10 of the needed strength. The overall weight of the fiber is exponentially related to the strength, so the tether works out maybe 20,000 times heavier than his design- which makes it completely uneconomic.

OTOH, single fibers are almost strong enough, but only if you allow absolutely no 'safety factor'. Most normal engineering uses atleast 2 safety factor, and usually many times that. But as nobody knows how to splice them together into a rope, and doing so would lose atleast 25% strength, it's not enough.

He's got the best architecture I've seen for this by a long way, nice paper study. Not practical right now. Hope somebody sorts out the fibers very soon.

Re:Nope, doesn't work (yet)

[Knobby]

Carbon nano-tubes have a strength to weight ratio that is roughly 100x that of kevlar, and depending on how it's rolled can be either an insulator, a smiconductor, or a conductor.. Pretty cool stuff.. Unfortunately, they can currently only be manufactured in micron lengths..

Re:Nope, doesn't work (yet)

[crisco]

So we can have a Beowulf cluster along with our space elevator? Thats pretty cool!

already been tried (kind of)

[BlueboyX]

Nasa already tried a long cable experiment. This one was probably made of metal though. They deployed a long cable from the space shuttle (i forget how long, but it was pretty darn long) and let it 'drag' behind. The idea was that as it dragged across the Earth's magnetic field, it would produce an electric current that the shuttle may be able to use.

Well, they goofed up the math somehow. They underestimated the stresses on the cable and the thing snapped shortly after deployment, flinging it away from the shuttle. They did not retrieve the cable; one more piece of space junk.

Re:already been tried (kind of)

[Anonymous Coward]

And what's your point? That because we tried a primitive experiment using tethers once that didn't work = the whole idea is stupid and we should pursue it no more. Advances in science and technology don't mean instant gratification. That type of shortsightedness and impatience gets us nowhere.

Robinson's Mars novels

[Anonymous Coward]

In Robinson's Mars novels (Red, Green, Blue) the major reason for installing an elevator was mineral extraction on Mars. It is WAY too expensive to lift ores and the like off of a planet with a rocket. The elevator was tethered to the moon Phobos (or Deimos, I can't remember) to add the counterweight, provide the material for building the cable and act as a spacehub.
The only way an elevator would ever be built is for heavy industrial reasons. Business would love to get its hands on a fresh virgin like Mars. Think of all of that untapped iron, boxite, ect. And with no borders to contend with. It's a prospector's wet dream.

How long to travel up the rope?

[Anonymous Coward]

One thing that *nobody* is mentioning is how long it would take to ride up and down this thing. They mentioned using electric motors & rubber wheels. Okay, let's say that we can safely travel 300 mph on rubber wheels (rocket cars in the desert don't count, assume improvement over current racecar tech) - 22,000 / 300 = 74 hours = a little over THREE DAYS. The longest flight I've been on is 16 hours, and that's from here to Japan, so let's assume that 16 hours is the max limit for people to not get pissed off. This means it has to run at Mach 2 all the way to from one end to the other.
Combine this with all the other issues - the local wind effects alone at the Earth endpoint will cause all kinds of nice down-stream problems - I doubt this will be built in any of our lifetimes.

Re:How long to travel up the rope?

[mlk]

Considering the it use to take to get from one end of the planet to the other, three days to get into space is nothing.

The real problem with a space elevator

[hodeleri]

Is that you could no longer have satellites in any orbit other than geosynchronous unless their orbits were very carefully tuned to avoid hitting the cable.

BTW: A space elevator will never really fall, if you put a rocket on one end you could get it to pinwheel, but I don't think any terrorists would have the time to attach a rocket motor with sufficient thrust to get it to do this.

No really, think about it, the space elevator would be rotating about GEO at exactly one rotation per day clockwise, while the earth rotates about its center at one rotation counterclockwise. Nothing you could do at the end would allow you to make the elevator fall.

If you really wanted the elevator to fall, go to the center of mass and cut it in half. That'll bring it down quickly.

BTW, read Rainbow Mars by Larry Niven, even if it is fantasy. You'll probably agree that we really don't want a space elevator :)

Re:The real problem with a space elevator

[ptrourke]

Is that you could no longer have satellites in any orbit other than geosynchronous unless their orbits were very carefully tuned to avoid hitting the cable.

Easy enough. The station at the center of mass would be an obvious target, and the cable would be rather thin and so easy to avoid. This is not a problem - for the purposes of orbital mechanics, the cable is basically two-dimensional and orbits could easily be planned around it. Besides, I doubt that a satellite collision would do much, other than slice the satellite in half.

How the fuck. . .

[Bastian]

are we going to build that?

No, really. While we're building a 22,000 mile long cable strong enough to hold 20 tons, where are we going to put it? It's probably too big to actually /store/ anywhere, and, even if we did, imagine trying to transport the sucker.

We can't start stringing it off into space as we build it, because it'd keep tending to fall back towards earth until it were about. .. oh. . 22,000 miles long. (assuming they planned it so that 22,000 miles long would put its center of mass in a stationary orbit)

And, once we've figured out all that, how do we get it /up/ there? Build a 22,000 mile high crane? Really, I'd think that the rocket we would use to get the other end of a space elevator up there would be a greater feat of engineering than the space elevator itself, and building it in sections would probably be an even greater feat of engineering.

That said, it'd be a damn cool thing if we had it, and if a team ever succeeds in constructing one, I'll personally buy a beer for every member of the project.

Re:How the fuck. . .

[Slur]

I reckon it would have to be manufactured in space and then lowered to earth by some vehicle moving in unison with the rotation of the planet.

Re:How the fuck. . .

[Anonymous Coward]

RTFM, dude. Or article, in this case.

How does anyone transport big cables?? You roll them up. Stick your spindle in a shuttle, spit it out towards its proper orbit and you're all set.

When you're in place, you tether it to a counterweight you've prepared earlier in a stable geosync orbit and roll it out. How do you keep the cable tip pointed towards Earth? I'll let you figure it out (hint: drop something from a tall building and see what happens).

And you got modded "Insightful" for that?

Re:How the fuck. . .

[mgv]

That said, it'd be a damn cool thing if we had it, and if a team ever succeeds in constructing one, I'll personally buy a beer for every member of the project.

Thats a generous offer. Considering it takes 100 people to make a good game these days (esp if you count the game testers).

I would imagine that this sort of project would involve 1000+ people (probably a gross underestimate). At least you could probably by the beer at wholsale prices!

Michael

Re:How the fuck. . .

[ZigMonty]

Make it in space. Ship the materials up (hey, at least you can do it in pieces!) or get them from asteroids, etc. No said this was practical yet, just possible.

No they didn't.Re:... They forgot the taper factor

[WolfWithoutAClause]

The tape IS wider in the middle than the ends, the tape is very skinny at either end. And his deployment strategy works fine. Read the paper.

Science Fiction Answers all Questions...

[Donut]

This book from David Gerrold, entitled "Jumping Into Space" has a real good explanation of the logistics, economics, and politics of beanstalks.
I would highly recommend it to anyone who has questions about the safety precautions (wrapping around the planet!), communities (cities halfway up, agriculture all over it), and consequences (he who controls the stalk, controls the universe!).

Mr. Gerrold is an excellent writer, cutting his teeth on Star Trek, and then writing the excellent Ch'tor books.

OT: Apology (Spoiler Free)

[Embedded Geek]

As the other poster said - keep at it anyway. There's a lot more than that going on in the books than what I posted.

As to the (unintentional) spoiler... I read Red Mars so long ago that I honestly didn't think about it. I'd just figured either everyone had read it already or had never heard of it. So, apologies all around if it hosed you up.

Best ever

[Rand Race]

JPL's Frisbee...

I bet that's one cool frisbee.

Unfortunately, this is impossible

[BTWR]

...with this space elevator being a PERFECT target for terrorists. How could you keep Al Queda from suicide bombing one of the elevator shafts? Is it possible to really have a 15 mile perimeter around the entire elevator? How would one be able to implement this?

It's just a shame... humanity at it's best (a peaceful, cost-effective operation that would provide jobs, technological advances and allow money to possibly be diverted to humanitarian uses) is impossible because of humanity's worst traits.

Re:Unfortunately, this is impossible

[cheezehead]

Gimme a break. How do you prevent terrorists from suicide bombing the Space Shuttle? The Superbowl? Nuclear plants? The [fill in your favorite target]? It's all about security, and in the end, about acceptable risk. You can't completely eliminate all threats, just minimize them. Letting fear of a terrorist attack getting in the way of projects like this is letting the terrorists win.

Yes...

[fall-()ut]

It would be big target for a terrorist attack, but it would be rather hard to cause any major damage. First it would be located out in the middle of the ocean, and (hopefully) surrounded by warships so it would be very hard to do an september 11 style attack on it.

Secondly the tensile strength of carbon nanotubes is estimated to be 200,000,000,000 pascals (29,006,526 psi). Short of a nuke, I don't know where you would find a weapon that could break something that strong. If you did somehow manage to break it, only the portion of the space elevator below where you cut it would fall. To cause any real damage you would have to break it fairly close to the middle, and the only efective way to get there would be to ride the space elevator, and I think the would notice you sending a nuke up it.

And monkeys might fly out of my butt!

[jabber]

Really.. We can make nanotubes how long now?? And how long would one have to be?

Oh? "Theoretically possible" eh? It's also "theoretically possible" for a fully fueled 1957 Ford Fairlane to appear in my living room out of thin air - running.. With a supermodel in it..

Please, dear editors, 'might become reality' is trolling.

Re:And monkeys might fly out of my butt!

[cheezehead]

Yes, and according to some people the first trains could never carry people because all of the air would be sucked out of it at the lethal speeds of 20mph.

As I see it, there are three types of reasons that can stop projects like these from being realized.

1. Fundamental (physical) problems. Like traveling faster than the speed of light. You have to overturn the laws of physics to make it possible. Unlikely, but not completely impossible (it's been done before).

2. Engineering problems. Some things are theoretically possible, but there's a lot of work to be done before it can be realized.

3. Financial problems. If 1. and 2. are solved, you still have to find the money/resources to actually do it. Example: traveling to Mars. No fundamental problems, and the technology is there. Just add money.

It seems that this particular plan needs a lot of engineering and a lot of money. But there's nothing fundamental stopping it. And that's what is meant by "theoretically possible".

Grand Sights...

[gnovos]

NASA should really consider this. There is nothing, NOTHING that can motivate a nation and a world to tackle the endeavors of space than a 22,000 mile glittering testament to our power and ingenuity rising into the heavens.

Variation on the theme - dubious worth

[Embedded Geek]

OK, I know it doesn't settle the gravity well issue, but what if you put one of these on the moon?

• No transit time to Mars
• Much lesser gravity, allowing for an easier proof of concept.
• Like Mars, sparse population and less atmosphere would make it a safer place to experiment.

Of course, you'd actually need industry/population on the moon to make it worthwhile, but that issue is also present in the Mars beanstalk. Actually, when you think of it, the moon is an ideal place to run the (early) proof of concept...

Er, hold on. The moon is tidally locked with the Earth, isn't it? That won't generate a lot of certifical force, will it? There may be enough tension on the cable at one rotation a month to fight the moon's gravity, but it doesn't look too good...

Anyone want to correct me on this? I'd appreciate it.

Re:Variation on the theme - dubious worth

[znu]

A beanstalk needs to be anchored in geostationary orbit. There's no such thing as a geostationary orbit around a body that doesn't rotate on its own axis. So no, you can't build a space elevator on a tidally locked world. And it would be really impractical on worlds that rotate very slowly, like Mercury; you'd need an absurdly long cable.

Re:Variation on the theme - dubious worth

[buckrogers]

errrrr, the moon _does_ rotate... It spins once everytime it goes around the earth. If it didn't spin, it wouldn't always keep the same face to Earth as it orbits.

Re:Variation on the theme - dubious worth

[znu]

That doesn't help; it means that a geostationary lunar orbit would intersect with the Earth. Minor problem, that.

Re:Variation on the theme - dubious worth

[buckrogers]

Errr, no. The earth is already in geostationary orbit with the moon. (And the Moon is also in orbit around the moon, its a complexe wobbling dance.) That means that the earth is always over the same place on the moon. If anything else is also in geostationary orbit with the moon, then it would be in the same orbit, but in a different location than the earth, and so would _never_ intersect with the earth.

The earths gravity may tend to pull the satelite off course, but that is a different matter all together, and you can always put the satellite 180 degrees away from the earth on the dark side of the moon to counteract that.

There are also 5 locations called Lagrange points where the gravity of the moon and the earth balance each other out and you can place satelites there and they will tend to stay in that location. One point is exactly between the moon and the earth, 2 other points are about 20 degrees on either side of the main point, and is also a location on the opposite side of the earth from the moon and on the opposite side of the moon from the earth.

Re:Variation on the theme - dubious worth

[buckrogers]

Errrr, moon is in orbit around the Earth that is. doh!

Re:Variation on the theme - dubious worth

[Embedded Geek]

Which comes to my orignal question; Not whether it's possible to geosynch a satellite around the moon, but whether there'd be enough tension on the cable to actually haul anything up and down.

I'm starting to wonder if it might be doable, but (as with any beanstalk) boils down to specifics about materials.

hmmm

[Anonymous Coward]

First up, the terrorist thing...I doubt a beanstalk would be a target...it has very little to do with capitalism and much more with the development of mankind. Plus, I guess keeping the airspace clean in an isolated area is slighly easier than doing so in a built up area (cant very well shoot aircraft down above a city, can we now?).
But then we get to construction. We'll eventually have the materials to do this, with the correct tensile strenght needed, whatever. We might even be able to build these materials in a continual process (like when you produce a long slab of steel...you could theoreticaly make one as long as you would like) on site. And then you crash into the deployment of this thing...i.e. how do you get the cable up there? Obviously deplyment from the ground up to space is out...the cable doesn't (and can't, no matter how optimistic you are about material sciences) have the strenght to stay up. So you look at deployment from space down to earth; you get the continual proces started from the counterweight, trailing the cable underneath. Thing is, you then need to keep the counterweight in a stable orbit, but with this lenght of wire hanging from it, you'de need continuous thrust, the requirements of which go up exponentially as the canle grows longer and heavier. Remember, the system is only stable when it is tied to earth...and while you build it, it isn't tied to earth yet. I think fuel consumption to keep the counterweight in a stable orbit would be the prohibitive factor in the equasion...

Practical uses for a Space Elevator

[SWPadnos]

Somewhat off-topic, but...

There is a Sci-Fi series in which the space elevator is featured prominently, the Mars colonization series by Kim Stanley Robinson: Red Mars, Blue Mars, and Green Mars.

These are excellent books detailing many aspects of Mars colonization. (one of the quotes on the cover is something like "... these should be required reading for the next generation of mars colonists")

At any rate - if you want to read about some possible futures (without too much pseudo-science), these are an excellent bunch of books.

Re:Practical uses for a Space Elevator

[Jobby]

(one of the quotes on the cover is something like "... these should be required reading for the next generation of mars colonists")

Ironically, this quote is by Arthur C. Clarke, the author of The Fountains of Paradise, a novel detailing the construction of a Space Elevator and also metioned in the article.

By the way, why can't anyone agree on a common name for this thing? Space Elevator, Orbiital Tower, Orbital Tether, Beanstalk, Skyhook, Heavenly Ladder, "The Strand"...personally, I think we should use the term proposed by Tsiolkowsky, the Russian who had this idea originally - the Cosmic Funicular.

It's a compelling fantasy...

[matthewmichaelagee]

I studied this concept as part of a commercial space development group back when I was in college. It's quite compelling.

There're two significant challenges in implementation, though.

The fundamental flaw in the concept lies in conservation of rotational inertia. Think about a spinning ice skater - as she draws her arms in, she spins much faster. The opposite is also true - as a rotating mass extends from its center, its rate of rotation decreases.

The space elevator rotates at a constant geosynchronous rate, but as its payload is raised along that axis, the difference between its linear inertia at the surface of the earth and its linear inertia around the circumference at geosynch altitude (or any significant altitude along that axis) is absorbed by the elevator's structure.

Unless the payload applies some sort of thrust perpendicular to the axis of the elevator, that difference in inertia only works to pull the whole system back down to earth. Effectively, the amount of energy you'd have to put into the system to keep it up would equal the thrust expended to send the payload into orbit by conventional means.

Then there's the whole issue of vibrational harmonics. Accumulated shocks from winds, payloads, and even space dust would propagate up and down the string (any human structure of that incredible length would effectively be a string in tension) and create severe vibration problems. That'd take some *seriously* epic engineering to dampen.

NASA has done some experiments with tethered satellites which address the vibration issues (as well as accumulated electric charge from atmospheric drag), but they were intended more for spinning-wheel satellite applications than for space elevators.

It's a really cool idea that unfortunately is a something-for-nothing scheme. If there were some kind of cool electric thruster system which didn't rely on reaction mass, it'd be feasable, but then we're straying into Area-51 technology. ;)

[This is my first post to /. - I may have messed up initially and buried this as a reply deeper down the treads.]

Technology of Indian Snake Charming

[torklugnutz]

NASA is currently recruiting a team of flute-playing Snake Charmers to coax the cable into the air and keep it there. Send your demo tapes now!

Already done perhaps?

[niola]

LOL, Found this article at Weird NJ

WeirdNJ.com

ONE OF NEW JERSEY'S MOST BAFFLING MYSTERIES came in the form of a silver "thread" that was suspended for days over the house of Mr. and Mrs. A.P. Smith of 85 Forest St. in the quiet suburb of Caldwell in Essex County.

--Jon

Interesting, but won't it snap?

[fractaltiger]

As soon as I saw this, I couldn't take this out of mind: if you have a piece of thread and tie something to an end of it, like a sphere (the Earth) and let the sphere hang from it, the string will tense up and form a straight line. Correct?

Now, if the sphere or Earth were to rotate, your thread would be contorted by the sphere's pull on the point where the thread is tied to the sphere. So, the thread will eventually bend out of its straight shape and collapse from the mere differences in pull provided to the space end (null) and the one given by the Earth's end as it rotates constantly.

My point is, when you build something so large and want it to stand upright, it's hard. It's like trying to lift a flagpole with your bare arms and keeping it from tipping over whenever there's some wind.

Well, tell me what you think. Please, no flames from YOU, mr. Anonymous coward!

Skies of Arcadia

[Anonymous Coward]

Soon they'll be building an elevator into Deep sky ;) Did NASA get the idea from this game, d'ya think?

(Skies of Arcadia - Dreamcast)

REPOST!

[xagon7]

It has been nearly a year!

Re:Could you imagine... Yes, I can!

[Xerithane]

1. The source code and any disks containing Windows 3.11 and Win32s.
Sure.. because Microsofts engineering is so horrible that no good can come out of it. I forgot.
2. All the AOL CDs on the planet - though that would break the damned thing, wouldn't it?
And all the people who collect them like baseball cards for entertainment, and a company that really did in fact do a good thing by publicising the internet and in many ways making a space for slashdot to exist?
4. The Microsoft Marketing Department.
How have they made the industry go to hell? They were one of the main forced behind creating the "industry".
5. Larry Elliston's ego.
I don't know Mr. Elliston. I know Mr. Ellison is a hardworking individual, and deserves what he got through a good product, and a commitment to working hard.
6. Ditto for BillG, SMcNealy and SJobs
Yeah, because they didn't do revolutionary things that helped create an entire industry employing hundreds of thousands of people.

Yeah - you did forget everything. You forgot what made this industry what it is. You forgot that your sense of humor sucks ass monkeys. And you forgot that it was past your bedtime.

Hmmm, this smells bad for Taprobane...

[Pig Hogger]

Let's hope that dubya's goons won't be deployed to Taprobane to level that old temple and kick some monk-ass...

One thing he said bugged me

[Anonymous Coward]

Edwards admits the elevator could be a
terrorist target. But, he said, "It's away from
everything. There are few, if any, airline
routes through there. And a few
well-deployed ships would be able to protect
the station, the anchor station, and the
cable."

Well yeah, it's away from everything... EXCEPT THE SPACE ELEVATOR. That's like saying airports are safe from terrorism because they are outside of the city limits!

At one time

[Convergence]

Only 50 years ago, it was a tens of cubic centimeters per tube. Now, you can have 100 million in something lightweight enough to put on a finger. You can fit a billion in your pocket. They're already talking about billion-transistor chips in 10 years.

Other 'impossible' things have happened. Humanity can marshall immense resources. The interstate highway system built tens of thousands of km of highway, moved mountains, built bridges, over a country with millions of square km.

In 50 years look at the communication system we've built. Its millions of times higher bandwidth.

And, with modern productivity, you can do orders of magnitude more stuff with less effort.

THings aren't geting faster and better.. THey're getting faster and better at an ever increasing rate. There has been more change in the last 60 years than all of history put together. Some would say 30 years.

Moderators smoke crack, news at 11 !!!

[NoMoreNicksLeft]

Um, yeh. Meta-moderation can't come quick enough for me.

Re:Moderators smoke crack, news at 11 !!!

[Boiling_point_]

yeah dude, you got robbed. I love the idea of making it to a geosynchronous platform, then loading your maglev podule onto the track on the other side, pressing "GO!" and flinging yourself at Mars! That would ROCK!

Is this article a troll?

[cicadia]

NASA began considering the concept in June 1999 at the Advanced Space Infrastructure Workshop on "Geostationary Orbiting Tether 'Space Elevator' Concepts" held at the Marshall Space Flight Center in Huntsville, Alabama.

GOTSEC? Can this be real?

Re:Is this article a troll?

[Anonymous Coward]

No, but goatse.cx is ;)

scifi:

[TI-83]

I was reading The Fountains of Paradise today, by Arthur C. Clarke (published 1978). It's about a guy building a space elevator. A couple things were required, in his scheme: an equator location, so that the tower will go up perpendicular to the earth, a geosynchronus satellite, even gravity at the base site (several places were rejected, in the book, for being un-even gravity-wise), and the base was supposed to be on a mountain (to rise above some of the forces of weather, and to start higher (um, duh)). one thing that was pretty key was the "monofilament" that the elevators ran up on: carbon crystal filaments which were 'grown' in zero-g. anyways, fiction. though it does seem to match up somewhat with this discussion. and scifi writers often check their facts somewhat (along with making them up...).

this was already invented by a famous person

[CowbertPrime]

Arthur C. Clarke invented this after he invented the geosynchronous satellite. He mothballed the idea because there was no feasible material to actually do this. In his book 3001, he reintroduces the space elevator. He also points out that he unmothballed the idea because of the construction of super-strong carbon nanotubes arising from the discovery of buckyballs (C60).

Stairway to Heaven...

[psyconaut]

Wouldn't it be cool if they played Stairway to Heaven on a tape loop in this thing...

Bad Vibrations?

[rnicey]

Questions for the astro peeps here...

What would the g-forces be like on the end of this thing going around so fast at that distance? Wouldn't it be like one of those machines they stress test pilots on?

The document describes it like swinging a ball around your head, but that means you've got an oscillating force. Would it be enough to make the Earth wobble a bit? Would that be comfy? Would we need two elevators, one in each hemisphere?

Re:Bad Vibrations?

[ChaoticPup]

What would the g-forces be like on the end of this thing going around so fast at that distance? Wouldn't it be like one of those machines they stress test pilots on?

The g-forces would be negated by the earth's gravity if it were implemented properly. A pilot training centrifuge or a ball swinging overhead are not very good anologies because they lack the gravity element.

Consider a geo-stationary satellite. Is it travelling fast? Heck yeah. Now imagine lowering a long-a$$ rope out of it (ignoring or correcting for effects that the rope may have on its geo-stationary status).

When the rope lowers to the point that it's a foot off the ground, are you thinking "ball swinging over head"? Nope. Satellite is still holding its orbit, and the rope has nothing to do with the orbit. Lower the rope another couple of feet and tie it off -- does that make any difference?

--CP

after intensive research..

[..p]

..scientists have found this to be an improvement over the escalator to nowhere.

..aaaahhh... ..aaaaahh... ... ..aaaahhh...

Just use DNA

[coyote-san]

I've actually seen one analysis using DNA as the construction material!

It's not strong enough, but it has other interesting properties and could be used for related structures.

Re:Just use DNA

[Jobby]

I think this is related to the incredibly strong twisted double helix structure of DNA. Indeed, in Kim Stanley Robinson's Red Mars, the cable is about 10 metres in diameter and strengthened by a diamond double helix. This creates a poetic scene during the fall of the elevator, when the double helix is the last part to be destroyed by impact with the ground. It's strange that the people who are analysing what would happen if the cable fell didn't really take into account the sheer strength of the cable. In Red Mars, most of the cable stays intact throughout re-entry, and only the last several thousand miles distengrates on impact.

Solution to those problems.

[Ungrounded Lightning]

Unless the payload applies some sort of thrust perpendicular to the axis of the elevator, that difference in inertia only works to pull the whole system back down to earth.

Then there's the whole issue of vibrational harmonics. Accumulated shocks from winds, payloads, and even space dust would propagate up and down the string (any human structure of that incredible length would effectively be a string in tension) and create severe vibration problems. That'd take some *seriously* epic engineering to dampen.

To some extent those two are each others' solutions.

The low-frequency vibration solves the pull-back problem. Thinking discretely: The weight of the payload on the thether and the taut teather form a loaded "stringed-instrument" string:

Go up a bit, you pull the string back.

Stop and wait a bit, the string accellerates you forward.

Now go up some more while the string is still going forward, providing a "pull" backward that damps the vibration, stopping the string at the vertical position.

Repeat.

In fact you do this continuously, modulating your ascent slightly so the net result is the string stays nearly vertical. When a vibration starts to build up you adjust your speed in sync to damp it.

Similarly the tether and the weight at the end (large compared to the payload) form a pendulum. It's a much more complicated pendulum than one near the surface, due to the varying gravity and the rotating coordinate system, but that's the basic idea. Again thinking discretely:

Go up a bit. The couterweight pulls back.

Stop and hang around. The counterweight starts going forward.

Go up some more. You decelerate the counterweight and bring it to a stop near the top again.

Repeat.

Again you do it continuously, this time keeping the weight at a constant displacement behind the point over the tether's base. The slant of the tether corresponds to a forward accellerating force from the rotation of the earth, providing your angular-momentum transfer by accellerating your payload and decellerating the earth. (Coming down you push the counterweight forward to accellerate the earth and decellerate the payload.)

Now there may be one or more locations along the tether where what you have to do to damp the two modes is exactly opposite. But if you've kept it damped on your way to those spots you should be through before an oscilation builds up. Or run two or more payloads simultaneously and coordinate them so you can always damp both modes. (Multiple coordinated payloads can also provide better damping and trade off each others' effects on the tether to achieve faster travel.)

Of course you have to put your counterweight a bit further above geosync, so lift losses when it is displaced downward slightly don't turn into a positive-feedback collapse.

If you don't have enough payloads in transit you can damp higher-frequency modes against the atmosphere with a few active airfoils spotted along the tether. (REALLY high frequency stuff - like seconds-to-audio - you can damp with a couple small structures attached near the geosync level.)

Effectively, the amount of energy you'd have to put into the system to keep it up would equal the thrust expended to send the payload into orbit by conventional means.

No.

The amount you have to put in is only a small delta above the amount that you would have had to put in to run an electric elevator up an idealized stiff structure of the same height - and the delta approaches zero as your damping approaches perfection.

But once it's up you don't need to power it AT ALL, which I'll get to in another posting.

"Ring" construction

[coyote-san]

Something I haven't seen mentioned here (is the idea forgotten, or has it been proven to be flawed?) is the "construction ring" method.

Basically you launch your cable fabrication facility and create a *huge* loop of cable. Something long enough to encircle the earth at geostationary orbit. This loop is initially unstable and will require temporary station keeping engines. You don't care about north-south twists, but don't want in-out twists to grow to large. (Read any analysis of _Ringworld_ for details...)

You then turn the cable machines on their side and start laying cable towards/away from earth. The cables will follow local geopotential fields down and up, and eventually you'll have a starter cable touch down. This can be a temporary cable, designed to be discarded, that does nothing but throw mass up the cable to build the ballast and feed additional cable machines that are producing the production cables.

Eventually you have ring in geostationary orbit, plus numerous anchors along the equator. You supplement the ring at geostationary orbit with another ring a bit inside (or outside) of it so that it's always under tension.

Besides solving some construction issues, it eliminates many of the collapse modes. If the cable snaps, the upper portion is kept in place by the ring. Even if all cables are snapped, the ballast weights will keep the ring under tension and survivors can manage station keeping by dumping ballast. (Unfortunately, if all cables snap the rest of the system will have a different net orbital velocity and there could be a big jolt.) Since there are multiple anchors, there's little value to terrorists in destroying any single anchor.

I know that _3001_ mentioned a ring as an endstage after building the first beanstalk, but I thought I've seen papers suggesting they be used as a construction platform.

And the secondary benefits are huge. Let's say the ring is 250,000 km long, and there's a 500m wide band of solar cells attached to that ring. The solar constant is around 1370W/m^2, that's potentially 171 GW of pollution-free power than can be fed down superconducting cables - 540 trillion kWh/year. According to the USGS the US consumed about 9 billion kWh/year of power from all sources in 1998, so even if the ring has only 1% efficiency it would still provide every person in the world 300x more power than the average American consumed in 1998!

Re:"Ring" construction

[coyote-san]

oops - I knew I should have triple-checked those numbers! It's potentially 1500 trillion kWh/year.

Re:"Ring" construction

[jelle]

And now calculate the cost of the endeavour, don't forget the cost of getting the basic materials for such a long cable in geosynchronous orbit. Even when you do it from the moon, it's going to be more than the sum of all world-wide national debts.

Then the cost and yearly maintenance on the 125 billion square meters (approx 1375 billion square foot) of solar panel you're talking about.

Isn't that about 20 square meters per inhabitant of this planet?

Even at sea level, we can't afford such a large panel for everybody.

Getting the energy for free.

[Ungrounded Lightning]

To transport you (70 kg) up to an altitude of 200 km would take [at 100% efficiency] roughly 300 kWh of energy. At 0.30/kWh (say), that's roughly $100.

Here's how to do it for zero energy cost, once the tether is up and the first set of vehicles are "charged".

(By the way: I haven't seen this anywhere else so I may have just invented it. Dibs! B-) )

Build your tether so it goes out FAR BEYOND geosynchronous orbit.

Your vehicle consumes energy as it climbs to geosync orbit.

But as it goes further out, it is going DOWNHILL against the local apparent gravity again, experiencing increasing centripital force from the tether. It collects energy by DEcellerating itself against the tether. When it has collected enough (and released the payload at a desirable velocity) the vehicle decellerates to a stop (collecting still more energy) and starts back toward earth.

It uses part of its stored energy to "climb back down" to the geosync point. Then it continues to ground, accumulating more energy by regenerative braking against the tether (just as it did above the geosync level). It arrives at the ground with as much power as it started with, or more.

Make the tether long enough and your payload can achieve solar escape velocity and still leave you with more "charge" in the vehicle's storage than you started with. (Launch some cheap rocks to power the space terminal's parking lot lights. B-) ) Of course the tether might end up so long that, even using the extra length as the entire counterweight, you have to strengthen the lower end a bunch. (This I haven't worked out.)

With no-cost (except storage) energy, your trip only costs the ROI on the equipment. (Probably reasonably large. But still LOTS cheaper than rocket-based space shuttles.)

It's not perpetual motion: Like tidal power, you're getting your energy from the spin of the earth, slowing it down to power your system.

But if the envirowackos complain, a millenium or two later, that their watches say sunrise is a couple nanoseconds late, you can bring down some ore from an asteroid mine and balance things out.

Re:Getting the energy for free.

[Anonymous Coward]

Well, this certainly would be a much smaller fraction of environmental change than the CO2 (tens of percents, which is a huge change), so we could hope that the potential negative effects wouldn't be that bad...not that soon, anyhow (the rotation of the earth is slowing down in any case).

It's not a matter of whether someone complains, but whether there are nasty side-effects. For CO2, even if we forget about environmental effects, if you'd experience the level of change we've had in the atmosphere lately instantaneously in the air surrounding you, you'd notice that it feels significantly more difficult to breath (if you breath into a sealed bag, it's not the lack of oxygen but the large amount of CO2 that makes you feel like you're suffocating).

Pondering the Space Elevator

[flacco]

Space Elevator: Another project brought to you by NASA after a few hours with the SpaceBong 4000.

Weight of fuel vs. weight of payload

[Junior J. Junior III]

I'm pretty sure that the entire vehicle (payload + fuel) for the larger rockets weighed in at around 200 tons.

I might be confused, it's been a while since I read up on space travel. It's too bad the file in this case is 15MB.

But if I recall correctly, the largest of the Soviet Energia rockets was capable of lifting a 20 ton payload. By comparison, the US's largest heavy lift vehicle, the Saturn rockets, were capable of lifting 10 tons.

Now, if I am confused, then those numbers might be 20,000 lbs and 10,000 lbs instead of 20 tons and 10 tons, respectively. That's *still* a fairly good sized chunk of the 20 ton payload promised by this space elevator idea.

it's a trick!

[ChemEGod]

Look on page 39 of the NASA document. This is actually a plan for Dr. Evil to move the Earth out of orbit.

The Indian had done it before!

[Anonymous Coward]

The Indian had "elevated" stuff like monkey and small children into space for the last 500 hundred years! All they need was a big thick rope!

Why use cable at all?

[Anonymous Coward]

Perhaps I'm ignoring something obvious but if you're going to build a space elevator, why not just use magnetic fields to lift the payload instead of having to develop ultra-strong cable and mechanical actuators (granted, you'd have to build the supporting structure but if you're going to do that anyway, why not make things easier on yourself)?

Do you clowns ever read the articles?

[Anonymous Coward]

I agree with your dire forecast. It would be terrible for such a huge thing to crash to the Earth. It could wrap around the entire Earth. Besides, this "space elevator" would be a giant, provactive,[sic] easy target for terrorists.

Read the paper! The cable is designed as a composite with a binding agent that has a low melting point. If it were to come loose and come crashing to earth, it would heat up on reentry, and fly apart into a big dust cloud. It would not wrap around the earth, and it would not plow into and destroy large slices of cities.

Why don't you doom-and-gloomers try reading the science and finding legitimate flaws that future design teams can address, instead of making "dire forecasts" based on what you read in a science fiction novel?

$40 billion is so cheap!

[GPS Pilot]

From the TechTV article: while all this may be technically possible, it doesn't mean NASA has the money to pay for it. The price tag for the initial Earth-based space elevator is estimated to be $40 billion.

Over the past 27 years, about $150 Billion has been spent on the Space Shuttle program. What do we have to show for it? Certainly not reliable, low-cost access to space.

Hundreds of round trips per year could be made up and down the 'space elevator.' By contrast, it's a really good year if we get eight shuttle flights.

Dragon Line

[evilroot]

But can it interrupt the Dragon Line long enough for us to kill the insane boo . . . . . . nevermind.

What about a "sled"

[Anonymous Coward]

Which looks like a ski jumping platform. You start from the top, then along that arc accelerate the mass with a monorail-type magnetic levitation approach. When you hit the end you release the locks and off it goes...

Some years ago I read about this in some popular science magazine. Anyone know what became of it?

It was built on the side of a mountain. But why should it be on the side of a mountain. Why not build it underground?

Nukes not that bad.

[ZigMonty]

Actually, it's not that a nuclear rocket would normally release anything radioactive, it's what happens if it blows up. Theoretically, the exhaust is just super heated gas. If you could be sure that the nuclear fuel would survive an accident intact then you could probably use them (convincing Greenpeace would be another matter). It's not entirely relevant because it's talking about deep space missions but here's an article on nuclear rockets.

I'm sure someone must have thought of this...

[Bnonn]

...but 36,000 km is a long way. The article isn't clear on where you'd unload the payload, but unless you want to expend more fuel achieving geostationary orbit after you've hitched a ride up to LEO, it seems like you'd be going the full 36,000 km.

Now, I understand that the higher you go the less air resistance you encounter (after about 1,000 km it's pretty negligible iirc, though low Earth orbit satellites do encounter minimal air resistance), but even assuming you can average mach 2 (approximately 2,376 km/h--pretty amazing considering that you still have the friction of whatever lifting mechanism they use) that's a trip of just over 15 hours. Now, I've sat in a comfy airliner for twelve hours, and it sucked. And I have a feeling that an airliner ways a wee bit on the heavy side of 20 tons.

So is anyone else seeing the potential problem in terms of commercial use for public space trips, or did I get something wrong? I mean, great view, but hella sore arse.

tripple OT

[Kraft]

or...

Expect nothing - hope for the best.

Re:tripple OT

[Embedded Geek]

LOL!! Don't think I'll change my sig, even though your version is more realistic.

Have they thought this through?

[ZigMonty]

I can see a problem with a 300km long, 100km high *wall* on earth. I thought 100km height was the standard definition of space!

At that scale, it must affect the weather. It would act like a giant sail and catch the wind. I know it would be mostly parallel to the West-East winds but 30,000km^2 is a hell of a big sail. It would be a pretty strong force on the side of the wall. If it's tapered, you're going to be deflecting wind upwards. I haven't done the math but this *will* push down on the structure. How much? I don't know. What happens if you get a cyclone (hurricane) in the area?

Also, do we really know the effects of deflecting that much air upwards? Until we *really* understand the weather, we should probably avoid building stuff on a geological scale.

The space elevator, being thin, wouldn't have most of these problems. Has this guy really thought everything through? I'm ignoring the obvious problem of how to get half a million tonnes of diamond.

Re:Have they thought this through?

[Yurian]

I think you should read the article a little more carefully - its not a wall, exactly, its supported on stilts. Quote for the article:

The overall structure could be openwork like a radio tower, and could have approximately 60 footprints 10 km apart on the ground - if we set aside a hectare for each foot, they only occupy 0.02% of the land under the tower. The footprint foundations would each bear the weight of a small office building, no great technical challenge.

For those who use different units, a heactare is a square 100m on each side, or about 2.47 arces. So these feet are really pretty titchy. So, its not going to act like a wall/sail at all, and I doubt its not going to affect the atmosphere much more than a sky scraper, really - cetainly no more than a space elevator.

As for the obvious problem of how to get the diamond, well, its much eassier than to get a billion tonnes of 40,000km carbon nanotubes into orbit. Even the easiest part of that - capturing a carbon rich asteroid, is way beyond us at the moment, and poses an extinction level risk.

I think this thing is really a much more realistic medium-term possibility, and a damn good idea.

Re:Have they thought this through?

[Anonymous Coward]

Good lord, I wish people would read before pontificating. He disposes of the asteroid-capture scenario up front, then describes his alternative - seven shuttle launches place a satellite that extends a really thin cable down to the surface, then you use crawlers to pull ever-thicker cables into space.

Do the math

[ZigMonty]

This cable is going to be pretty thick right? It's going to be 1000s of km long right? *You* do the math and tell me how it's going to fit in a shuttle!

Gee

[usey]

Who wants to be the first to bungi jump off this?

SANTA FE (Reuters)

[Anonymous Coward]

The space elevator system that was earlier reported compromised by revolting prairie dogs has begun a rapid disintegration. While details are few, the base structure has begun collapsing, demolishing entire towns in its wake. NASA is making every attempt at predicting the path of the falling structure, which is predicted to break into smaller pieces as it fals to earth in the next 48 hours. The suggested evacuation areas include Texas, Oklahoma, Kansas, and both Dakotas in addition to all points east and west.....

The cartoonist pokes his nose in

[HTayler]

The damage on the ground depends on a couple of things: first, how much heat can the cable take before evaporating, and second, what is the length of the cable, rotational speed, etc.

The comic in question (this reference has footnotes) deals with a space elevator on a terraformed Luna sometime in the 31st century, and makes quietly implicit speculative assumptions about strength of materials. No, the strip was not rigorously researched. The research was borrowed from Kim Stanley Robinson, in whose Red Mars novel we are treated to the spectacle of a space elevator coming down hard.

The elevator in Schlock Mercenary never does come down, though. After all, Kim Robinson already DID that gag.

--Howard

22K miles won't do the trick

[GoatsNeighbor]

The cable wouldn't be long enough. Sure, the endpoint would be geosych, but the weight of the cable BELOW the geosych point would suck it back to earth like a child slurping speghetti. You need a centripital reaction equal to the sum perceived "pull". So... you'll need to either nearly double the length of the cable, or provide a "ballast" mass outside the geosync line. Since buckeytubes are mostly carbon, why not build the "factory" on a carbanacrous asteroid, start building cable, and ejecting waste materiels like a mass driver to get it to earth orbit. By the time you get here (30 years or so) you should have at least a start on enough cable built, and a nice rock to use as ballast. Now if we could just get the factory to the asteroid belt.....

North America

[Mastagunna]

I seem to remeber settlers traveling for much longer then 16 hours to get to North America. And 74 hours would have seemed like a dream to them. You can stay here on earth and not visit space, and not explore, but I know I would gladly sit on a elevator for 3 days to get there.

From the top down.

[BobBoring]

Think before you speak young one.

1. Roast rocks in space for carbon and other useful stuff.
2. Make cable from carbon.
3. Use juke left over from making cable for counter poise etc.
4. Drop loose end into atmoshpere in to pre built foundation.

Burn!

[absurd_spork]

Do carbon nanotubes burn? Carbon does.

MOD PARENT UP

[ToastyKen]

Please mod parent up.

Space Debris

[epukinsk]

My favorite part of the article is how they're going to send Commander Keen up there to blast all the space debris in low-ish orbit so it doesn't hit the space elevator.

-Erik

A good reason not to build it right away...

[Wolfrider]

Terrorism.

This type of thing would make a PERFECT sitting-duck target. As a result, it would need to be HEAVILY DEFENDED if it was built.

Now I'm not saying it wouldn't be COOL, it just won't happen any time soon.

From the book 3001.. by Arthur C Clarke

[Anonymous Coward]

The concept of a 'ring around the world' in the geostationary orbit (CEO), linked to the Earth by towers at the Equator, may seem utterly fantastic but in fact has a firm scientific basis. It is an obvious extension of the 'space elevator' invented by the St Petersburg engineer Yuri Artsutanov, whom I had the pleasure of meeting in 1982, when his city had a different name.

Yuri pointed out that it was theoretically possible to lay a cable between the Earth and a satellite hovering over the same spot on the Equator which it does when placed in the CEO, home of most of today's communications satellites. From this beginning, a space elevator (or in Yuri's picturesque phrase, 'cosmic funicular') could be established, and payloads could be carried up to the CEO purely by electrical energy. Rocket propulsion would be needed only for the remainder of the journey.

In addition to avoiding the danger, noise and environmental hazards of rocketry, the space elevator would make possible quite astonishing reductions in the cost of all space missions. Electricity is cheap, and it would require only about a hundred dollars' worth to take one person to orbit. And the round trip would cost about ten dollars, as most of the energy would be recovered on the downward journey! (Of course, catering and inflight movies would put up the price of the ticket. Would you believe a thousand dollars to CEO and back?)

The theory is impeccable: but does any material exist with sufficient tensile strength to hang all the way down to the Equator from an altitude of 36,000 kilometres, with enough margin left over to raise useful payloads? When Yuri wrote his paper, only one substance met these rather stringent specifications - crystalline carbon, better known as diamond. Unfortunately, the necessary megaton quantities are not readily available on the open market, though in "2061: Odyssey Three" I gave reasons for thinking that they might exist at the core of Jupiter. In "The Fountains of Paradise" I suggested a more accessible source - orbiting factories where diamonds might be grown under zero-gravity conditions.

The first 'small step' towards the space elevator was attempted in August 1992 on the Shuttle Atlantis, when one experiment involved the release - and retrieval - of a payload on a 21-kilometre-long tether. Unfortunately the playing-out mechanism jammed after only a few hundred metres.

I was very flattered when the Atlantis crew produced The Fountains of Paradise during their orbital press conference, and Mission Specialist Jeffrey Hoffman sent me the autographed copy on their return to Earth.

The second tether experiment, in February 1996, was slightly more successful: the payload was indeed deployed to its full distance, but during retrieval the cable was severed, owing to an electrical discharge caused by faulty insulation. This may have been a lucky accident - perhaps the equivalent of a blown fuse:

I cannot help recalling that some of Ben Franklin's contemporaries were killed when they attempted to repeat his famous - and risky - experiment of flying a kite during a thunderstorm.

Apart from possible dangers, playing-out tethered payloads from the Shuttle appears rather like fly-fishing: is not as easy as it looks. But eventually the final 'giant leap' will be made - all the way down to the Equator.

Meanwhile, the discovery of the third form of carbon, buckminsterfullerene (C60) has made the concept of the space elevator much more plausible. In 1990 a group of chemists at Rice University, Houston, produced a tubular form of C60 - which has far greater tensile strength than diamond. The group's leader, Dr Smalley, even went so far as to claim it was the strongest material that could ever exist - and added that it would make possible the construction of the space elevator.

(Stop Press News: I am delighted to know that Dr Smalley has shared the 1996 Nobel Prize in Chemistry for this work.)

And now for a truly amazing coincidence - one so eerie that it makes me wonder Who Is In Charge.

Buckminster Fuller died in 1983, so never lived to see the discovery of the 'buckyballs' and 'buckytubes' which have given him much greater posthumous fame. During one of the last of his many world trips, I had the pleasure of flying him and his wife Anne around Sri Lanka, and showed them some of the locations featured in The Fountains of Paradise. Shortly afterwards, I made a recording from the novel on a 12" (remember them?) LP record (Caedmon TC 1606) and Bucky was kind enough to write the sleeve notes. They ended with a surprising revelation, which may well have triggered my own thinking about 'Star City':

'In 1951 I designed a free-floating tensegrity ring-bridge to be installed way out from and around the Earth's equator. Within this "halo" bridge, the Earth would continue its spinning while the circular bridge would revolve at its own rate. I foresaw Earthian traffic vertically ascending to the bridge, revolving and descending at preferred Earth loci'

I have no doubt that, if the human race decides to make such an investment (a trivial one, according to some estimates of economic growth), 'Star City' could be constructed. In addition to providing new styles of living, and giving visitors from low-gravity worlds like Mars and the Moon better access to the Home Planet, it would eliminate all rocketry from the Earth's surface and relegate it to deep space, where it belongs (Though I hope there would be occasional anniversary re-enactments at Cape Kennedy, to bring back the excitement of the pioneering days.)

Almost certainly most of the City would be empty scaffolding, and only a very small fraction would be occupied or used for scientific or technological purposes. After all, each of the Towers would be the equivalent of a ten-million-floor skyscraper - and the circumference of the ring around the geostationary orbit would be more than half the distance to the Moon! Many times the entire population of the human race could be housed in such a volume of space, if it was all enclosed. (This would pose some interesting logistics problems, which I am content to leave as 'an exercise for the student'.)

Hmm. . .

[Anonymous Coward]

It occurred to me that you can get a tremendous amount of energy by sending objects down the beanstalk. Instead of saving energy we could maybe send asteroids and stuff and actually produce energy.

As for terrorists, if it gets severed the top half will fly off into space. Only the bit attached to Earth will cause damage. Unless it is damaged at a considerable height it will not do anything as bad as wrapping itself around the planet. That's unlikely in any case because it would come crashing down over all the middle east countries as well as everywhere else.