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Space Elevator Going Up
Adlopa writes "The
Guardian newspaper reports on scientists' efforts to realise the space elevator, as first described by Arthur C Clarke in his 1979 novel 'Fountains of Paradise'. Advances in materials science mean that 'a cable reaching up as far as 100,000km from the surface of the Earth' is no longer an impossibility and 70 scientists and engineers are discussing the idea at a conference in Santa Fe today."
will it have a 13th floor?
-knowles
Any excuse to hang out in Santa Fe is a good one.
At about a third of the way along the cable - 36,000km from Earth - objects take a year to complete a full orbit.
Uh oh...
~ Give me 101 plastic soldiers, and I will conquer the world.
From the story:
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A space elevator would make rockets redundant by granting cheaper access to space. At about a third of the way along the cable - 36,000km from Earth - objects take a year to complete a full orbit. If the cable's centre of gravity remained at this height, the cable would remain vertical, as satellites placed at this height are geostationary, effectively hovering over the same spot on the ground.
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Actually, at 36,000 km from earth, objects take a day, not a year to complete a full orbit. The moon takes about 28 days to complete an orbit, (one lunar cycle) and any object far enough out from the earth to require a year in order to complete an orbit would passed the instability limit, where it would be captured away by the sun's gravity, and would no longer orbit earth.
My rights don't need management.
http://www.spaceelevator.com/ About the only place I could find with all the information piled into one spot.
It would be more interesting to bind the cable to a monster truck and pull the cable down
Shredded plane. (strong cable - duh)
And the lowest note ever twanged.
though it would have to be at the poles for stability sake.
How do you propose to have a geostationary orbit at the poles?
Trolling is a art,
Imagine the fact that the tip would accelerate as it fell...most of it would end up burning up in the atmosphere. Also imagine how little of the earth's land area lies along the equator. Not much. It might cause some localized devastation, but it's not a world-breaker.
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Why would it have to be at the poles? I can't see any reason whatsoever for that restriction.
Yeah, it would be awesome to have the counterweight crashing down on top of Antarctica.
Idiot.
~ Give me 101 plastic soldiers, and I will conquer the world.
You'd have to be at the top of the cable to do anything particularly harmful to it
Think of it as a cable hanging down from geosynchronous orbit, not a tower
It's been discussed many times that if such a thing failed, damage would be minimal:
1. Depending on what happens it might simply fly into space.
2. If it falls, most of it would burn in the atmosphere.
3. If it reaches surface it'd be somewhere in the ocean anyway, so damage would be minimal.
4. Targeting a thin wire somewhere in the middle of the ocean is much harder than two giant towers.
It's not going Up until we can look up and see it...whether it is going up or down during construction.
Imagine the fact that the tip would accelerate as it fell...most of it would end up burning up in the atmosphere.
That's true, the risk of the thing falling down and crushing people is almost zero. But there is another problem: if it burns, will the resulting particles be hazardous for us to inhale? There's research going on about that.
No, actually you're thinking of the fart zone. Hold your breath for that stretch of cable.
They say the first thing to go is your penis. Well, it's either that or your brain. I forget which...
IANAUE (I Am Not An Uber Engineer), but I should hope that they'd design the thing to have a way to eject the whole thing away from earth. If there was some problem, they could detonate explosives at the base, and the whole thing would centrifugally fly away from earth rather than fall back down.
A programmer is a machine for converting coffee into code.
But But But
When a cable under stress breaks it can cut right thought metal...
When this long whip breaks, it will slice right thought the earth!!
tower of babel?
geosync orbit.
otherwise, you would have an elivator that flys through the atmosphear at amasing velocity and is almost imposable to step onto with out going fast yourself.
I am the Alpha and the Omega-3
Quote from the article:
"Until some of the basic science concerning how to connect nanotubes together and transfer load between them in a composite is understood it will remain elusive, but a lot of progress is being made."
Basically, the state of the art with carbon nanotubes is that you can build them a few centimeters long, of almost/just about the right strength (72 Gpa); but nobody has made or can make a rope even 1 foot long with the right strength (ideally 130 GPa including a 50% safety factor).
State of the art carbon nanotube ropes are down under 3GPa (less than Kevlar strength). To oversimplify the problem nanotubes are very slippery and hard to join with any strength. Splicing rope out of threads traditionally loses 20% of the strength, but nanotubes are too slippery, and not strong enough anyway for that right now.
Still, enormous progress has been made; and it looks surprisingly promising; but it's impossible right now.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"No, because it's not going to be moving thousands of miles per hour.
Thats the longest extension on a CAT-5 I've ever heard of, I'd go with wireless instead.
You'd also have God's wrath to deal with when he trips over it when going to the fridge for a midnight snack.
If you outlaw the law, only criminals will have laws
I don't mean to sound too condescending, but really, the centrifugal force of earth's rotation makes that impossible. I would have been humoured if you would have stated imagine a 100,000 km cable being hurtled at the moon when I move there. For it to fall to earth would mean the earth would stop spinning...highly unlikely given what we know.
You might be able to argue that inertia from the atmosphere would allow it to operate like a whip, but even that is farfetched. I doubt they would implement such a system without properly addressing such an issue.
Be more afraid of Near Earth Objects. Of course those things fall from roughly 4.7E17 km. Why the hell don't people imagine that?
Why would it have to be at the poles? I can't see any reason whatsoever for that restriction
Because you don't want to deal with the centrifugal force associated with stuff at the equators.
An object on the surface of the earth travels at a speed proportional to its distance from the axis that the earth rotates in. An object in geostationary object above that same object has to move at a much faster speed to keep up because it is circumscribing a bigger circle. So if you built the elevator at some point other than the poles, you have to make sure you provide transverse acceleration to any objects you send up the elevator.
On the other hand, at the poles, the whole elevator is in line with the earths axis and you don't have to worry about accelerating the objects you are sending up.
Mmmm.. Donuts
One unlikely problem could be capturing the public's imagination. "When we actually start launching this it's going to be kind of boring," Dr Edwards said. "There's no smoke, there's no pillars of fire and there's no loud rumbling noises. There's just this thing that slowly ascends the ribbon into space."
This problem would be neatly solved once the initial expense of the elevator was recouped. At this point it would be much cheaper to send objects into orbit, including people... ride up the chain, get on a space suit, get out on your own nanotube cable and float around 36,000 km above the earth without ever needing to learn how to help fly a space shuttle.
I foresee an enormous tourist interest, to the point that someday several elevators will be sent up exclusively for tourists to use.
Nasa played around with dragging wires through the atmosphere to generate static electricity.
This thing will could possibly generate HUGE amounts of SE as the atmosphere whizzes past it 24/7. Are there plans to capture and use this electricity or what??
calculating orbits by hand (this was before the advent of the PC, remember), for example. Much of our scientific and engineering achievement today was first written about by Sci Fi authors, including personal computers, world wide networks, men traveling in outerspace, satellites, genetic engineering, waterbeds and much more. I personally hope we continue building what Sci Fi writers write about. Idealism and dreams lead to greatness. Pragmatism and "being realistic" lead to boredom and stagnation.
In my universe I'm perfectly normal, it's not my fault you don't live in my universe.
Everyone is bashing this, but can you see the good in it? Elevators don't cost millions of dollers to launch. They don't explode in midflight. Most of all, they are cheap. My only problem with this is where the hell the elevator goes to. Does it just...go up?
Fuck Iraq and let's cough up roughly 12 space elevators instead.
Hate me!
But you have listened to the new about NASA during the last few months? ;)
I wouldn't trust them to change a light bulb anymore
If the cable broke, wouldn't the end attached to Earth fall back? The center of gravity has been changed and the far tip of the broken end wouldn't be moving fast enough to provide the force needed to keep the cable pulled in place.
Trolling is a art,
I swear to god, if my eyes roll any harder, they're going to fall out of my head.
It's not like we're talking about a high tension cable here. The cable's structure will be balanced by gravity -- the center of gravity will rest at the geosynchronous point, meaning that the bottom half will be falling toward Earth while the top half will be moving away at an equal rate. (Disclaimer: my degree is in English and I'm relying on this thing called "high school physics class"...)
Really, it depends on where the cable snapped and what the nature of the accident was...
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Elevator to the moon ? mars ? other galaxies ?
No GNU has been Hurd during the making of this comment.
Imagine a 100,000 km cable falling to earth.. I wouldn't want to be under it.
The cable is actually pulling up. Catastrophic failure at any point along the cable results in it leaving earth.
Basically, you put the center of gravity of the cable right at geosynchronous orbit (ideally you want it to be a little higher than that)
If it's at geo orbit, then the cable stays still even if you cut it off. A hurricane would push the cable sideways, tidal gravity is enough to keep the cable taut by itself. It's a non-stable equilibrium however; eventually the cable will drift enough to escape earth gravity. Unless it hits a mountain first. But even then, EVERYONE is under it. It'll wrap around the earth at least once before it's done falling...
I am disrespectful to dirt! Can you see that I am serious?!
Yeah it takes one day to complete a full orbit at 36000km! That's the whole point! :-)
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Am I the only person that sees the obvious negative consequences of this? How hard would it be to sabotage this elevator and have the thing either fall down on Earth, or fly away from Earth (I don't know how gravity would affect it, I'm not an expert or even a novice on that). I see it as a really bad idea because it can go wrong very easily.
"Anything that's invented after you're 35 is against the natural order of things" - Douglas Adams
New continents were found, the sound barrier was broken and even space flight was developed at the cost of human life. Yet, it was worth it.
As a species we have become too concerned about safety. We are afraid to such extent that testing new discoveries (medicinal, chemical and physical) are becoming so burdened by the hysterical safeguards, governmental red tape and the associated costs that nothing ever gets done. To my mind, this development threatens the very progess of our species.
BOO! TERRO
Pretend that I posted a lame joke about listening to elevator music for a very long time. Then mod me up as "Funny". Half of the so-called "Funny" posts aren't, so this one will fit in nicely.
It _is_ pretty scary to think about a paper thin ribbon of material falling on your head. It would probably get in your hair and necessitate a shower and a vigorous shampooing.
A space elevator would make rockets redundant by granting cheaper access to space. At about a third of the way along the cable - 36,000km from Earth - objects take a year to complete a full orbit. If the cable's centre of gravity remained at this height, the cable would remain vertical, as satellites placed at this height are geostationary, effectively hovering over the same spot on the ground.
Objects take one DAY to complete a orbit at 36,000 km... and if that orbit is in the same direction as the earth turns, then you can orbit continuously over a spot on the equator. There's actually a minor perturbation, but those forces are minor compared to the other forces a space elevator would have to deal with...
BTW, a nice recent sci-fi novel on the subject of space elevators is _Rainbow_Mars_ by Larry Niven, of _Ringworld_ fame.
I am disrespectful to dirt! Can you see that I am serious?!
From the article: "When we actually start launching this it's going to be kind of boring," Dr Edwards said.
After watching rockets (and shuttles) explode into spectacular fireballs, boring is just fine with me. Considering the majority of mass on any rocket is used to just get it to a level of orbit, this could be a nice way for us to start working toward the moon (and eventually beyond) again.
The really exciting will no longer be GETTING into orbit, but rather what we can do once we get there.
Tequila: It's not just for breakfast anymore!
It is better to remain silent and be thought a fool than to post and remove all doubt.
Guestion for you - what do YOU think would hold this thing up? Maybe you expect a bunch of Indian Fakirs to be sitting around the base blowing on flutes? (reference to Indian Rope Trick for those who were wondering...)
To answer my own question, the fact that one end of the cable is moving faster than the other end makes the part that is moving want to fly off in a straight line - but the tensile strength of the cable keeps the two hooked together. If the cable were at either of the poles, there would be a bunch less difference in speed between the two ends - and the system would be more UNSTABLE.
Acts of massive stupidity are almost never covered by warranty. --me.
...estimates it would take about $7bn (4.4bn) to turn the concept into reality...
So how exactly do you come up with a budget for a project that calls for an unknown (but massive) amount of nonexistanium, delivered to orbit no less?
1. Invent ridiculous, incorrect hypothesis about proposed system. 2. Make fun of NASA for having such a ridiculous invention. 3. ??? 4. Profit!
But there is another problem: if it burns, will the resulting particles be hazardous for us to inhale?
Carbon nanotubes are primarily, well, carbon. Burning up would create the same stuff that charcoal makes, CO2. Potentially less toxic than second hand cigarette smoke. There may be some other chemicals in there, but the whole idea is to make the tube out of a single material, the nanotubes, to make it strong. So, yes, research is good, but toxicity is probably not the biggest issue.
Tequila: It's not just for breakfast anymore!
God Damnit... because of people like you Clarke once said "the elevator will be built 50 years after people stop laughing".
Would you please document yourself, make the appropriate research, concentrate for 2 seconds on the topic at hand before you open your hole and spill out the first fearful thought that comes to your mind?
- It would be built in the middle of the ocean on a floating platform
- If it broke, most of the 100,000Km would NOT fall to earth (junior high physics can tell you that), and most of the piece that would, would burn in reentry
- What remains would be much more harmless than your poisonous, unscientific whining.
You're like those people that hear the word "nuclear" and immediately thing BAD BAD BAD
There are two kinds of people in the world: Those with good memory.
Probably. Then again, the atmospheric pollution expelled by a typical rocket launch is also hazardous for us to inhale. Very. Not to mention the crud emitted when a satellite (or, worse yet, a Space Shuttle) burns up.
Fortunately, rocket launches and re-entries are a relatively rare event, and most of their nastiness is dumped high enough in the atmosphere that it gets dispersed well before anyone breathes it in. The same would be true of burning-up bits of elevator.
From the article.... "The biggest technical obstacle is finding a material strong but light enough to make the cable; this is where the carbon nanotubes come in. These are microscopically thin tubes of carbon that are as strong as diamonds but flexible enough to turn into fibre. In theory, a nanotube ribbon about one metre wide and as thin as paper could support a space elevator."
I know the fiber is as strong as diamonds, and I understand that along it's 100,000 km length it's flexible enough to dodge objects.
But how will they protect it from, well, planes at altitudes below 100,000 feet?
It wouldn't have to equal the mass of the Earth - we're not trying to make the cable the center of an Earth-counterweight co-revolutionary system here. It just has to be massive enough that the centrifugal force on it would be enough to hold taut the cable. Tie a rock to a string and swing it around - the string remains taut, but the rock isn't your weight!
GL
It has to be over the equator in order to be in geosync orbit.
Objects that are in a distance of 36,000 km from earth will complete one orbit every 23 hrs 56 min, so if it will be over the equator and move in the same direction as earch it will be over the same position on earth
Won't ants and snails and stuff be able to climb up this thing? And what happens when they get zapped by all the radiation up there?
Actually, the nanofibres might be a health hazard on inhalation
Sigh.
Who modded THAT insightfull?
"Imagine an accident. I wouldn't want it to happen to me!" Is not insightfull.
We get these inane comments with every article about transport.
Electric cars: Imagine getting electrocuted.
Supersonic planes: Imagine a supersonic collision with a building.
Space elevator: Imagine it falling on you.
Ship: Imagine it sinks.
Train: Imagine it derails.
Etc, etc, etc.
We don't need to have those modded up! They're not saying anything original.
You can't take the sky from me...
at this 36000km mark, would be the center of gravity for the cable itself (and elevator)... so the counterweight in space needs to only equal the weight of the earth side cable and machinery. the reason they put it 1/3rd of the way along the cable is so that less weight needs to be lifted into space to act as a counterweight (16.7% less?). additionally since the cable in space does not need to support its own weight, only the tension between the counterweight and the center of gravity, it does not need to be as strong, requiring less material.
i've used weight instead of mass, because well, thats what most people understand in the vernacular, so don't bother flaming me about that.
to email me: take my
Space flight should be about space flight. Not about climbing some friggin bean-stalk.
The idea is just so - I don't know - demeaning. It's like cheating in an exam.
And God knows the concept of showering is scary enough to the average /. reader..
*You are not allowed to read this*
Nope, it should just be heavy enough that the force caused by the rotation of the weight keeps the cable straight and also any weight it might carry. ;)...
Think spinning cicles with a jojo, if you spin fast enough the jojo-string will be nearly horizontikal (and it does not matter how heavy you are
+++ MELON MELON MELON +++ Out of Cheese Error +++ redo from start +++
... Coming up with a way to make enough carbon fiber (er nanotubing?). Like an industrial process wasn't developed yet--? I'd like a response, screw karma ;)
a) Carbon nanotubes are strong but very, very light. They have a high surface area per unit mass. In the lower atmosphere, the cable would float to earth like a piece of fishing twine; in the higher atmosphere it would just burn up.
b) Not really. Airborne traffic is smart enough to deal with comms towers, skyscrapers and hurricanes. This thing does not move - all you need to do is fly around it.
c) Yes it does. In order to advance space traffic, we need to get to geosynchronous and LEO MUCH cheaper, allowing us to loft the larger masses necessary for more ambitious space missions. Getting big tonnages out of Earth's gravity well cheaper and more reliably than is currently possible would be a BIG win for space travel.
A 100,000 km cable of pure buckminsterfullerene nanotubes -- a surprisingly simple structure amenable to being built and extended by nanomachines. Nanites.
Becareful of the nanites though, eventually, they always turn sentient and demand a piece of our action!
I think there is a historical account of this early on in the Bible...
No, it would need to be a few tons. Put a blob of bluetack on the end of a string and whizz it round your head. Does if fall down? No. Is it 150lb? No.
If you read the article, they are looking at the Pacific ocean as the base of the ribbon. If there was a real problem, and they needed it, it would be possible to cut the ribbon on the earth side, and this would force the cable UP instead of down. Not necessarily the best thing to happen, but it could burn up (carbon) in the atmosphere on the way back.
This stuff is pretty light, and they are looking at a RIBBON, not a cable. So the air resistance would prevent a 100 ft piece (for example) from accellerating to a speed that will cause any major damage. At least that is how I understand it after reading the article.
Same reason if you throw a sheet of paper off a tall building, no one is hurt. You throw a marble instead, and you can split a skull.
Tequila: It's not just for breakfast anymore!
The same year that Clarke published his novel, Charles Sheffield published "the other space elevator novel," The Web Between Worlds. You can read the first few chapters at Baen Books' web site.
That's in Science vol. 151(3711), p. 682 (1966).
Interestingly, Clarke envisioned the thread leading up (or down) the skytower to be nanodiamond, while these days nanotubes are all the range. The difference in the materials is that in diamond carbon atoms have four neighbours but in tubes they have only three, as in graphite, yet at about the same formation energy. That makes their chemical bonds actually stronger than in diamond and gives nanotubes their extraordinary tensile strength at low mass - perfect for engineering a space elevator.
Yeah, becasue to keep a sling taut you need a rock that weighs as much as you. Maybe you just need enough centripetal force to counteract any weather (or other extraneous forces) since the position of the center of gravity would allow it to stay in a geosynchronous orbit disregarding forces outside of the system.
Do I contradict myself? Very well, then I contradict myself, I am large, I contain multitudes. -- Walt Whitman
The atmosphere (and the earths magnetic thing which induced the current in shuttle tethers) wont whizz past it, because the cable will not be moving relative to the earths surface. Charge from the atmosphere using the cable as a conduit is all covered in the space elevator faq's on numerous sites.
From what I've head, a space elevator is a bad idea in the sense that the atmosphere has a singificant EMF gradient between the surface of the earth and far up in the atmomsphere. Completion of such a device would case the world's largest lightning bolt ever. You'd be basically creating the largest "short" ever. :P
This thing is not going to be in a crowded, public access zone. It'll be in the middle of an ocean, hundreds of miles from anything, presumably with the US Navy's finest patrolling the surrounding area. Can't see al-Qaeda and their like getting anywhere near.
But how will they protect it from, well, planes at altitudes below 100,000 feet?
3 words: Restricted air space.
You can't take the sky from me...
According to A. Clarke himself the space elevator was invented by Jurij Artsutanov from St. Petersburg.
(3001, The final Odyssey, under sources)
Warning: This sig contains a small bug. ==> *
The cable is actually pulling up. Catastrophic failure at any point along the cable results in it leaving earth.
not if the point of failure is beyond the midpoint, causing the center of gravity to shift below GEO and draw the cable down.
that being said it wouldn't likely be dangerous due to it being lightweight, wide and thin. A sheet of flexible cardstock does about the same damage dropped from 100 feet or a 100 thousand.
-5, Ignorant of laws of physics
+1 Funny
Acts of massive stupidity are almost never covered by warranty. --me.
...about the space elevator is when the kid who launched his satellite just before you mashes every button before getting off.
It's geostationary... the atmosphere whizzes past at ~0mph.
Think about it. If it breaks at the centre of gravity, you're left with the bits being pulled down ONLY, and nothing to tension the cable from above. The outer part of the cable will indeed fly off into space, but the rest will still present a problem. Similar considerations will apply if the cable breaks somewhere else: the bit on the earth side will no longer be pulled away from the earth strongly enough.
John_Chalisque
hear hear.
The cable is only epoxied together, so anything past 100 km or so above the earth would fall apart into fibers during reentry (you'd probably blow it up into sections to help it melt correctly). Nobody knows what effect breathing these fibers in would have.
Incidentally everyone envisages the cable as being made of metal- it actually would weigh on order 1kg per kilometer, so it's not going to hurt you (although I wouldn't want to motorcycle fast at a section for obvious reasons.)
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"I can only shudder when I think about the new pick-up lines that arise once it is complete.
;)
"Hey Sweetie, wanna see my Space Elevator"
or
"Guess what is 3 feet long and DOES NOT reach into space"
and
"Let's play Space-elevator; I've got the cable, and you're gonna be the counterweight"
+++ MELON MELON MELON +++ Out of Cheese Error +++ redo from start +++
smooth, I love how you stuck that in there. Invented by Heinlein in '30's IIRC, He was trying to design a better hospital bed. I don't believe he ever actually built one, though.
And how many people thought that blacks would always be slaves, or that we would never need more than 64 K of RAM for PCs, or that women would never be astronauts?
My sister opened a computer store in Hawaii. She sells C shells by the seashore.
Look at the display: if it says 100003 ...100004....100005 you go up.
Actually the centrifugal force is -exactly- what you want. The object is accelerated by the taut cable as it climbs it, so that when it reaches geostationary orbit it is travelling at the appropriate velocity. Remember that escaping the Earth's gravity well is about velocity, not just plain altitude.
Wouldn't this idea result in the largest grass trimmer ever build ? The velocity at the outer edge must be huge. And the centrifugal force at the bottom would probably rip up a big chunk of paradise before any lifting device could ever be attached to it.
Hell, even the outer rings of Saturn are lagging.. and they weigh nada-squat..
Ok, here's another idea. Why don't they make a fleet of garbage collecting space robots that go out and find materials to make the cable on orbit? Then, they just launch the factory fleet, order them to begin work, then sit back and wait for the cable to come down in a few decades. The only real obsitcal is finding suitable materials on orbit. But there's so much junk up there, maybe it's possible.
A programmer is a machine for converting coffee into code.
The "centrifugal force" is what keeps the whole thing up. Build it at a pole and it will just come down immediately. Duh.
Finally! A year of moderation! Ready for 2019?
9/11, 3-4 stolen lear jets evading 1-2 F-16s, ground hugging L-39s, heat seaking shoulder mounted SAMs aimed at elevators climbing the cable, Sharks with friggin laser beams (mounted in van filled with salt water) ... ?
"3rd floor; stereos, TVs, radios..."
"203rd floor; binoculars, range finders..."
"56,304th floor: parachutes, hang gliders..."
"124,202nd floor; helium baloons, oxygen tanks..."
"973,404th floor; motion sickness pills, glare filters..."
"as the atmosphere whizzes past it 24/7"
Umn... whizzes? It's going the same speed as the atmosphere...
A.
...bringing you cynical quips since 1998
Space exploration has been hindered by cost and gravity, letting us only do a fraction of the exploration that we have wanted to do. Even creating a solution that cuts the cost of getting a hunk of metal into space by 10 times would revolutionize the industry.
Considering it takes a 300 million dollars to launch the shuttle, which averages about $4,600 per pound to get a hunk of metal into space, being able to reduce that to $12 a pound means you break all the bearers of financing. Futurists, and scientist have been saying that to really break into true space exploration, and the commercilization of space travel, mining etc.. you have to be able to break the $40 a pound barrier.
7B is nothing even if it costs twice that it still nothing with amount of costs it will save in the long run. All I can say is I hope I get to see it in my lifetime.
Serenity|Chaos
You're number four I disagree with. There's more than just the line itself. I'm sure the base would be fairly easy to spot and in a well-known location. After all this would be a major supply line into space.
Why are you speculating that anything would have to mass the same as the earth? The Earth orbits the sun, but doesn't mass the same as the sun!
The physics are simple: you just have a cord that stretches out beyond geostationary orbit. At geostationary, the cord's mass is in a precise orbit (zero pull towards or away from Earth); beyond that, the cord's inertia pulls it away from Earth. So you don't even need a lead weight at the end -- all you need is enough cord. As a bonus, anything that gets pulled past the geosync point will be accellerated away from Earth; so you can use it as a cosmic slingshot.
Hoist a chickenfarm to the end of the tether, and you can throw eggs at Mars!
-Billy
A valid point, but it strikes me that the types of propulsion system we'll need for deep space vs. the types needed for getting in to orbit are radically different anyways.
Most of the promising high-efficiency propulsion technologies for deep space either rely on relatively small forces applied over a long time, or nuclear propulsion. Neither is remotely suitable for launching from Earth.
that's a great idea!!! geosynchronous orbit at a pole!!!
keep on living in your own little world there buddy.
Carbon nanotubes are primarily, well, carbon. ... Potentially less toxic than second hand cigarette smoke.
What if it was made of marijuna nanotubes? Imagine a fatty from here to the moon? That would be some serious toking.
With condolences to Tommy Chong.
When information is power, privacy is freedom.
Yes, but it's still much lower than the air velocities where NASA was experimenting, or indeed the air velocities generated by aircraft props and helicopter blades (good sources of static).
Any realistic system is going to use different mechanisms above a certain level (probably just about LEO) than it uses below it. The two problems are naturally separate, they naturally need to be solved separately, and the space elevator is a Really Cool solution to one of them. It's just plain fallacious to claim that a space elevator hurts access above LEO; it makes such access much easier.
Honest question:
Is static electricity useful for anything? Can you run an electrical motor with it? I thought the answer was no, but I can not substanciate my reasons for thinking that. Can someone help me out here?
Thanks
Acts of massive stupidity are almost never covered by warranty. --me.
Because you don't want to deal with the centrifugal force associated with stuff at the equators.
Er... actually it's the centrifugal forces at the equator that make this work. If you built it at the poles, what would keep it up; gravity would just pull it all back down.
It needs to be built on the equator so that that it will circle the center of the earth, and will remain geostationary (i.e. stationary relative to the surface of the earth). The centrifugal force caused by the spinning of the earth will keep the 'rope' taught, and allow you to climb it.
I lay awake last night wondering where the sun had gone, then it dawned on me.
What happens when the earth flips on its axis and the platform becomes one of the poles and the ribbon is twisted like a giant rubberband? Have they addressed this yet?
'Same speed C but faster'
IIRC there's a space elevator figuring in Kim Stanley Robinson's Red/Green/Blue Mars trilogy.
I forgot to mention in all the talk about LEO that a space elevator actually gets you beyond LEO, and even beyond geosynchronous, to or beyond escape. The cable is centered at geosynchronous.
A shameless plug for my new hobby site:
LiftWatch
A friend and I started this site a week ago because we noticed an apparent lack of a centralized news source for space elevators and related concepts.
Please check out the site and contribute!
We're hoping to turn it into the defacto space elevator portal site.
Think that magnitude of disruption might disrupt the weather patterns a little?
Don't let THEM immanentize the Eschaton!
Static electricity, by definition, doesn't move, so it's useless. If you want a motor, you need an electric current. It is possible to turn static electricity into current though, and vice-versa--that's what a capacitor does.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Offtopic? When the FAQ at liftport is pages and pages of html dedicated to discussing what could make a space elevator fall down? When a real scenario expressed at the end of Arthur Clarke's Fountains of Paradise is large, spinning wheel shaped, orbiting space cables acting as solar trebuchets? Offtopic?
Help help! Moderator abuse!
One rigid assed, never listened to rock, thinks poems must mean literally what they say, ignorant of space elevators and science fiction j/o of a moderator.
Except that most of the ribbon is doing its acceleration in space. 40 km of atmosphere, 50,000 km of earth-side ribbon. After a few minutes, whatever section of ribbon that is entering the atmosphere will be doing so at some truly wicked velocities. Given its highly un-aerodynamic shape, though, it'll burn up at the first wisps of air.
Dyolf Knip
The estimate of 7 billions $ seems very, very, underestimated.
And I suppose all known NASA locations are not consider as potential site to build this escalator, most of them are much more to near regions where tropical storms are likely to happen. Because, what would happen to a nice 1 meter large, paper thin, 100 000 km long light weight ribbon under a tropical storm? For sure, it will be hard to align the laser beam on the vehicles.
Achille Talon
Hop!
OK. You set up the "elevator" tethered to the Earth, with a counterweight at the other end.
When you exert a force on the elevator to climb up it, won't there be an opposite force pulling the counterweight down? What will keep the counterweight in orbit? If the answer is "rockets" then the elevator will be no more efficient than a rocket, and the whole endeavour is pointless.
Presumably I'm missing something, but what?
Which equatorial country is the U.S. going to invade?
Cuba...
That would make atleast a two-in-one operation.
Just because something is made of carbon doesn't mean that it will "burn up." This is especially true for stable forms of carbon like diamonds and, say, nanotubes.
Many of the deadliest things on this planet are basically weird variations of carbon.
I suspect that such chains would break, but create a really weird dust...they would not actually burn into CO2.
Oooooooooo aaaaaaahhhhhh...
The thrill of exospheric wake boarding must exceed those of ordinary sky-diving.
Wait til one hits the cable on the way down.
They have discussed that sort of thing before. If it snaps, everything above the snap point will fly off into space. Everything below will fall. The "cable" would be more like a ribbon. A few feet across, but only a micron thick. It would have a surface area:weight ratio WAY higher than newspaper, and a dropped newspaper isn't very danagerous. A dropped STACK of newspapers may be, but they said that the design would not withstand the lateral stresses of falling down sideways (Since every inch of it would be falling at a different speed) and it would break apart. So you would get nasty black confette. You may say "Sounds danagerous, it is so thin it could cut you!" but there would be nothing to exert the force required to cut you, since it is so light.
Plus, this would have to be on the equator. So if you anchored it somewhere on a small island in the Pacific, it would mostly fall over water, anyways.ASCII stupid question, get a stupid ANSI
Now, take the same piece of string, and double the length? What is the end result... you either need to spin it faster, or put more weight on the end to keep in tight. Now, double the length again and repeat... on and on and on. You will notice that as the length of the string increases, so does the effort required to keep it tight. You either have to keep adding weight... or increasing the velocity. Now given that the earth spins at a constant speed... what choice have you got? Adding more weight is about the only option.
The blurb says "as first described by Arthur C. Clarke in 1979". Much as I respect Clarke's accomplishments, this isn't one of them.
The concept may have first been documented by Tsiolkovsky, certainly it had an early mention by Artsutanov ("V Kosmos na electrovoze", Komsomolskaya Pravda, 31 July 1960), and was described in western literature at least four years before Fountains of Paradise by Pearson (Pearson, J., "The Orbital Tower; A Spacecraft Launcher Using the Earth's Rotational Energy", Acta Astronautica, V2, 1975, pp. 785-799).
I researched the concept a fair bit for my papers on using the idea on Mars as an easy way to export Martian volatiles (eg water) to other bases or settlements in the inner solar system. (I don't really want my server slashdotted so I'm not going to post a link. A google will find it.)
-- Alastair
Static electricity, by definition, doesn't move, so it's useless.
:D
Not true. You can harness it's awesome powers to make inflated balloons stick to the ceiling, after you rub them on your head. You can generate it by running your feet on the carpet in the winter, and touching your brother, making him leap 3 feet. It makes pulling clothes out of the dryer much easier: Just grab any one piece, and the rest stick to it.
Ok, not the most useful applications, but still fun.
Tequila: It's not just for breakfast anymore!
They address the human element. Everyone can relate to the visual of some giant cable snapping at one end and it falling on you. Fear is a reality and a human constant. If our ancestors weren't the most cautious of our species we probably wouldn't be here today.
Yes I know it doesn't explain the Aussies...;-P
See Here
-cp-
They're not saying anything original.
Well, now, imagine what would happen if they had said something original! That would have stopped everyone from reading the rest of the comments because they would be entrenched in thought about the original comment, and then we would all be stuck here, on Slashdot, and unable to do anything else!
Imagine that, huh!? Oh, and while you are, imagine that the article is a dupe article.
You are checking your backups, aren't you?
If you throw a diamond in liquid oxygen, it burns. In this case though, I don't think anyone knows.
9/11, 3-4 stolen lear jets evading 1-2 F-16s, ground hugging L-39s, heat seaking shoulder mounted SAMs aimed at elevators climbing the cable, Sharks with friggin laser beams (mounted in van filled with salt water) ... ?
What in the hell are you alking about? There weren't any planes in restricted airspace on 9/11/01.
Unless you actually believe the blatant department of defense lies about what happened to them on 9/11?
Remeber, the pentagon was attacked with a car (well, truck, actually) bomb.
That what's the news said on 9/11.
You can't take the sky from me...
Remember, the cable is going to mass in the thousands, if not millions, of tons. That's gonna need to be one heckuva monster truck.
Dyolf Knip
CB
free ipod and free gmail!
I'm sure the answer is out there, but exactly how do we do this? Because any force that is applied between payload and cable to accelerate the payload along it is parallel to the cable, whereas the force needed to produce the angular velocity is normal to it. Someone who hasn't forgotten physics please explain.
Panurge has posted for the last time. Thanks for the positive moderations.
I guess you're right, even if it's going to be a bitch pulling the cable over.
Big Brother Bush is doubleplus ungood.
Same reason if you throw a sheet of paper off a tall building, no one is hurt. You throw a marble instead, and you can split a skull.
;-)
THIS is a job for: Empirical experimentation!
-1 Jailbait
You can't take the sky from me...
From liftport's faq I get the impression is the danger is more that of inhaling the microfibers. Remember a single nanotube is small, thin, rigid, ...
Think of the diseases caused by asbestos, asbestosis....
The velocity at the outer edge would be larger than orbital velocity is at that distance. That's part of the point! Just by climbing to the top of the cable and letting go, your spacecraft not only gets out of the gravity well but gets hurled completely out of orbit! centrifugal force at the bottom would probably rip up a big chunk of paradise ...
No. Tidal forces on the cable make it want to stay vertical. The center of gravity is in geosynchronous orbit; therefore the bottom end of the cable stays above one spot on the earth, even while it's still descending.
http://isr.us/spaceelevatorconference/
well, actually, the space elevator would be composed of not simply a single nanotube line, but thousands of them twined together. A single nanotube line, although stronger than steel, wouldn't be strong enough to support much weight. It could support itself, which steel can't for that length, but not a whole lot more.
So you have to imagine a rope made of lots of twine falling to earth. This would fall a bit faster than a single piece of twine, and be a lot heavier.
Otoh, most of it would probably burn up pretty quickly, and a thick thick rope falling from 50k up probably wouldn't do much damage.
Cuba...
Not only invade it, they'd also have to shift the continental plates around to move the island of Cuba some thousand miles south to the equator. No doubt would this have a devastating impact on the ability of Cuban refugees to reach Florida.
Isn't Slashdot wonderful! Not only can you get ill-informed opinions on physics but geography too!
From ISR's FAQ:
Dragons.
I read a documentary about this once. Different colored (gold, bronze, brown, blue, green) dragons shall fly around protecting us from the falling thread. They fly fast, they fly between, and the burn the elevator as it falls.
Pilots of varying genders and ages ride the dragons, communicating with them telepathically.
The close telepathic connections, the sensual relationships between dragon and human are corrupting of course to the rest of society, and eventually all become obsessed with the dragon writers of porn.
Its not Static electricty. If you run a wire loop threw a magnectic field you will generate current and a drag force, if you push current you will generate a force. This is how electric moters and generators work. So In theory if you had a big wire loop in space you could run a current threw it and use that force to speed up your orbit, which would push to you a higher orbit.
They have had tecnical problems when they have tried it but they physics is all undergrad E&M.
Erlang Developer and podcaster
Ok, I grant you the balloons, but zapping your friend requires an electric current.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Actually, yes, we are. That's why advances in materials science were necessary before they could even think about building this thing. I quote from the article:
The cable's structure will be balanced by gravity -- the center of gravity will rest at the geosynchronous point, meaning that the bottom half will be falling toward Earth while the top half will be moving away at an equal rate.
Being "balanced by gravity" means there's a huge amount of tension here. In fact, that basically says that the top half (by mass - by distance probably a very small proportion of the thing) holds up everything below the center of mass at the geosync point. (Or from the other perspective: the bottom half holds down the top half, which would fly off into space otherwise.) It does that with tension in the cable, and we're talking about a lot of tension in the cable.
Let's put concrete numbers on it: carbon nanotubes are pretty light, but we're still talking about 35,785 kilometers in the bottom half (by mass) of the elevator - that's geosynchronous orbit around the earth. Say the elevator is 1 kg / m (very conservative, I think), which we'll call lamba (normal for linear density). Now gravity changes along the length of the cable (that's sort of the point), so we need an integral to calculate the force of gravity pulling the thing down:
F = \int GM dm/r^2 = \int GM \lambda dr / r^2
(where dm = \lamba dr). From my Physics I book, r_e (the mean radius of the Earth, which is a bit higher than sea level but not too bad) is 6.37 * 10^6 m. M (the mass of the earth) is 5.98 * 10^24 kg. And G is 6.67 * 10^-11 N*m^2 / kg^2. So the integral becomes:
F = \int_{6.37 * 10^6 m}^{6.37 * 10^6 m + 3.58 * 10^7 m} (6.67 * 10^-11 N*m^2/kg^2) (5.98 * 10^24 kg) (1 kg / m) dr / r^2 = 5.3 * 10^7 N = 53 MN (mega-Newtons)
...which I think is the require tension right above that point. I can't think off-hand exactly how geosync works, but essentially the stuff above that is being sped up and the stuff below (and the Earth itself, though not significantly) is being slowed down by that tension.
Disclaimer: I'm an undergrad physics student with a headache. I very well may have made a mistake above, but I guarantee it's closer than the parent post.
Mod this parent up...way up! This is indeed the present human course that will threaten us the most.
In "2001 a space odissey" i've once red "Earth is man's craddle, but you don't stay in a craddle forever" (sorry if it's badly translated, i red it in french). A very true idea...
We need this thing, among many other uses, to build spacecrafts in orbit. If it becomes technically possible, it should be made. How many conventionnal rockets, space shuttles comprised, have crashed ? Did it stop us from using them ? How much cars did kill people ? did we all revert to walking ?
One of those Europeans...
isn't rate of descent dependant upon density and wind resistance and not weight? Thousands of nanotubes wouldn't be any denser than a single tube. I would think that the basic structure, being an elongated plane would catch a lot of resistance.
For a long time Hollands one and only astronaut Wubbo Ockels (that is if you discount Laurens van den Berg who beat Ockels into space by emigrating to the USA) was an enthusiastic proponent of the space elevator idea. One of his jobs is Professor of Space Science at Delft Technical University. However when I asked him earlier this year how the work was progressing he just grinned and then proceeded to describe a new and grandiose project consisting of whole cities in geostationary orbit that would be strung together like a string of pearls on an ultrastrong cable around the equator.
Obviously this would put far less extreme demands on the strength/weight ratio of the string material. However the problem of the elevator would remain and he was not aware of any real progress on that front. As a materials scientist I think it's all pie in the sky.
Isn't the upper atmosphere charged?
:-)
What would happen if you grounded it with, say, a huge conducting nanotube cable?
And after it'd finished grounding, making the worlds largest fish stew, would we then discover that we kinda needed it?
There, that should get the panicmongers going nicely
Well, no; it's going the same angular speed as the ground, and each point along its length is going the same horizontal speed as the air would if there were no wind. But there will be lots of wind; there always is; our atmosphere does tend to move around a bit.
Scientist 1: Can we get this to work?
Scientist 2: Sure, just need enough cable.
Scientist 1: But will it be worth it?
Engineer 1: Nope. But it sure was a good idea to get us altogether for a drink.
Nanotubes aren't all that stable. In fact, one of the design issues the engineers face is how to protect the ribbon from oxidizing.
The cable will need a protective coating of some kind, which itself probably won't survive re-entry. Also bear in mind that the cable is supposed to be very light and strong - more like a ribbon. What doesn't burn up from being dragged through the air will flutter like sheets of paper and won't accumulate enough energy to do any real damage.
For dust to become a problem, it would have to shatter or be ground up or something, but I don't see how that would happen outside of normal wear and tear.
=Smidge=
Nooo.... I thought he meant it would be an elevator made from a single molecule...
Obviously it would be bundled, it just wouldn't be all that heavy for its size.
Jeremy
damn straight. you rock.
So your saying we should just forgo possibly one of the biggest breakthroughs in space technology because there is a possiblity of a threat from some terrorists , living in caves ,that may or may not be alive?
Ah, but what about centrifugal force. If his eyes were rolling very fast the resulting heat from the friction would destroy the eye socket and the eyes would simply roll out, no longer secured to the body.
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musings on politics and technol
So...
Where will they be going?
Not to mention the fact that it'll be anchored far away from any of the regular air and sea traffic lanes. Any attempt to approach the cable (or rather, the first 10 kms of it since the rest is effectively out of reach) will be spotted well in advance.
If the unthinkable happens and someone does manage to damage or break the cable, it will either float off or come down, burning up in the atmosphere. The people contemplating this elevator have already thought out such scenarios and published them. Even the cost of replacing the cable would not be all too high, once the technology and industry to manufacture the cable is there.
If construction was anything like programming, an incorrectly fitted lock would bring down the entire building...
Cows would stop giving milk you know...
10 ?"Hello World" life was simple then
...will volunteer to do a couple of weeks sitting on the end.
AT&ROFLMAO
I live on the fourth floor of an apartment complex and it takes about 3 minutes for the elevator to reach ground floor, another 2 for it go up to the fourth floor. It's faster for me to climb the stairs. How long will it take this thing to go up to the ISS?
Learn something new.
Watch them start using them to haul garbage away from the planet. I'll call it the end of spaceflight.
Logic, macros, and more
And while my brane is full of this stuff, why are people looking solely for tensile strength?
Can't they clamp interlocking magnetic fibres/stuff together and power it with a current running up/down it?
And if people are still chickenlickening about my early comment, you can suspend a small island from the cable somewhere high enough to not ground itself, but still low enough that you can fly stuff up to it.
Kinda like Tiphares in the Battle Angel books.
(God I loved those books)
(God I'll hate the movie)
Yeah, I regularly see Palestinians slinging 70kg rocks at the Israeli tanks.
Get your own free personal location tracker
Um, not exactly*. It's not really attached to the Earth. For example, the article describes it as "the floating base platform". The base (Earth) end is essentially hanging from the center of mass at geosynchronous orbit. If you cut away part of the Earth end, the part below the cut will fall to Earth and the part above will basically stay hanging.
If you cut high enough to throw the center of mass away from geosychronous orbit, several things will happen:
Lots of stuff will far to Earth (you had to cut high enough to do this).
The whole cable will move horizontally through the air (CG beyond GEO means it is moving slower than the Earth rotates, so the hanging cable will move towards the Indian Ocean).
The whole mass will probably start to rotate relative to Earth.
It will move into an eliptical orbit meaning it will move closer and further away from the Earth as it orbits.
So essentially it should do a bunch of funny motions from our point of view. I'm not sure how air resistence at the lower end would affect it. I think it's safe to say it will not fly off into space. It is in orbit after all, it'd just be higher than GEO. *IANARS, but I do work in the space industry and have taken grad courses in orbital mechanics and dynamics. I also have not studied the actual design, so there may be some effects I've missed or misinterpreted.
And when we discover life on mars, we'll know the egg came before the chicken.
Ceci n'est pas une sig
From where the energy is going to come which will pull (pr push) the elevetor( or the objects in elevator) up? By laws of physics we are going to do (mgh) amount of work, where m is mass of satellite, g is gravity and h is height. To take something at 36000 km above earth surface, mgh is same, no matter what way you choose. Is this much energy it going to come from rockets? Then whatt's the purpose of elevator? Why not use rocket only?. Hope I am making myself clear, we anyway need something to push it up, every time. So how is a cable connected elevator going to help? Probably I am missing some point. Please enlighten me here.
It will be boring until the NASA funds dry out and no one wants to pay the price to repair the aging Space Elevator Mir, then we'll have that scene from Green Mars (by Kim Stanley Robinson) where the space elevator cable wraps around the planet crashing down like a string of atomic bombs.
Lessee, Earth's Circumference approx 40,000 Km, this things going to be 100,000 Km long, so it'd rate about a 2.5!
"What thou shalt not, I shalt did!" -Bart Simpson
Nasa played around with dragging wires through the atmosphere to generate static electricity.
Unless I'm mistaking, you're referring to them draggin wires through the earth's magnetic field to generate electricity, not through the atmosphere.
In which case there is no problem here; the space elevator is almost perfectly orthogonal to earth's magnetic field, and stationary.
I am disrespectful to dirt! Can you see that I am serious?!
Note that NASA has already done extensive studies on the subject.
But how will they protect it from, well, planes at altitudes below 100,000 feet?
The problem isn't protecting it from planes, the problem is protecting planes from it.
Think not in terms of an elevator, but in terms of a tether. Under tremendous tension. The elevator has 36,000 km worth of tide at the bottom end, and nearly twice that at the top end. The thing is under so much tension that if the edge is thin enough, you could cut steel rebar like a hot knife through butter.
And it stands that tension all day every day without even so much as a hint of a complaint. A measley plane cannot hurt it.
Now, the base station is another story...
I am disrespectful to dirt! Can you see that I am serious?!
I hope they invlude a stairway in case of a power outage.
I wasn't trying to raise alarm...just pointing out that organic compounds don't just "burn up." They continue to react with the environment. For that matter, what we call "burning up" is reacting with the environment. Burning up means a state change...and not necessarily a state change for the better.
I pretty much stick with the whole conservation of energy and conservation of mass point of view. That is, all the matter that we work with will pretty much end up back in the environment, and that you have to think about how things really react and not just say...oh, it will burn up, or, oh, we will just bury it...
Fluttering like rather strong sheets of paper sounds a lot more like what would happen. Sci Fi books often have strings of fiber which are extremely dangerous as they tend to slice through people rather quickly...aka Ringworld... The scifi alarmist would have this 3 inch pieces of string floating around in the world slicing everyone to piece...worse than asbestos in the lung.
No, I think it is possible. Just snip the cable at the top. Now instead of one object with a center of mass in geostationary orbit, you have two objects, one above GEO and one below. The only thing holding up the cable in the first place was the counterweight.
Nor would it be Earth's atmosphere causing the "whip" effect. It's simple conservation of energy. If an object is in orbit, and you push it straight down, you've done nothing to slow it in the direction of the orbit. Since it's going too fast for the orbit you tried to put it in, it simply gains altitude until it's back in the original orbit.
But in the case of the cable, it can't go back up because the downward pull never gets released, so it moves faster and faster, picking up more and more energy.
But I do agree that this issue will be properly addressed before it's built. I always figured the cable could be segmented via explosives or some chemical process, so that most of the cable pieces would simply stay in orbit.
You want the truthiness? You can't handle the truthiness!
I'd imagine that as the end of the cable gained velocity, the resulting atmospheric friction would incinerate it before it got a chance to hit.
blog |
Yes, this is all well and fine, but I want to see Spider Dan or that crazy french fellow try to climb it.
Thank you for clarifying the above. I dunno what I was thinking -- yeah, obviously, there's going to be a lot of tension on the cable. But this "slice through the earth thing" was so laughably stupid I couldn't think clearly.
blog |
Slashdot - Texas Scientists Spin Carbon Nanotube Fiber
Other promising research:
Slashdot - Scientists Crack Silk's Secret
and
Slashdot - Nanotube Applications Grow And Grow
Maybe they did discuss all this and more at the conference - I would like to hope that these scientists and researchers are aware of what is going on in this far-flung field. I only wish they would have made mention of this stuff in the article for the common man, to show that it wasn't all so much "hooey" - that it is something which may be inevitable, and will happen sooner than we all expect.
We (all of mankind) are rapidly moving in a very funky direction, technology-wise. We have carbon-nanotube fibers. We are looking into other advanced fibers and fiber processes. We have found sea-creatures that make insanely great fiber optic fibers (and with the other stuff, we will probably be able to replicate the process very soon). The gains in communications alone will cause a lot of other gains to be made, because of distributed processing amongst far-apart supercomputing centers that need more bandwidth than they already have (and they have a crapload, but not as much as they want or need). Such fibers may help in the optical-computing dept as well. Remember also the stories of "growing diamonds" - that are so pure they are almost impossible to distinguish from real diamonds - and they have DeBeers quaking at the possibilities to their "markets", maybe destroying them. But these companies don't want the diamonds for prettiness or money (well, they want them for the money, true), but to be able to use them for the substrate of computer chips, instead of silicon, for higher speeds and better heat dissipation.
Couple that with all the other "funky" advances we have seen - we are all being dragged in a very wierd direction, speeding up the computing and learning capacity of all involved (and even if you are at the edge of the network, like most of us are here, and not where the action is, you will still be pulled in)...
I don't know where to go with this - except that our current distopia (and if you don't think we are living in a distopia, one every bit as scary, strange, and awe-inspiring as science fiction can come up with - you haven't been paying attention) is going in a new and strange direction, strangely reminiscent of what the "early-years" (which are only touched on) of Neal Stephenson's "Diamond Age" might have been like.
This is all strange shit, yet very few of us are even seeing it or thinking about the real implications, for some reason...
Reason is the Path to God - Anon
The physics are simple...
Angular momentum must be conserved. As an object starting out at the top of this elevator descends, its tangental veolcity would increase by a factor equal to the outer radius over the earth's radius.
A back of the envelope calculation leads to the conclusion that the object would be going 26179 km/h faster than stationary objects on the surface of the earth when it finally made it all the way down. This is assuming that the cord leaving the earth is in geo-synch. orbit along its entire length (a necessary assumption).
In fact, I suspect that the change in obrital frequency on descent would be sufficient to cause anything to burn up while dragging the cable around the earth (a cable that could loop around the equator about 2.5 times).
I mean, 7 billion for a space elevator, and another 3 billion to put a navy around it 24/7 to protect it from FUD.
And we are still cutting education? I don't understand this place.
"What do you do with the mad that you feel when you feel so mad you could bite?" - Mister Rogers
Did you see the whole section that was replaced? They completely replaced an entire section of the building.
Yes, I saw, yes, I know.
The initial dammage was a hole the size of my living room.
The explosion started a fire, the fire spread in the building (its what fire does), and dammaged all the burned area visible in that pretty satellite picture you linked.
Now, find footage of the second plane hitting the second tower. Look (frame by frame as it hits) at the huge plane-shaped hole it punched in the building, then at the gigantic fireball it set off.
Look at your picture of the pentagon again. If that was a plane that hit, it had a pilot with incredibly good aim, no wings, no fuel, and no fuselage to be left behind.
I can't find a link to one, but theyre are pictures of jet engines and chunks of airplanes around the WTC from 9/11. Yet, the pentagon's plane mysteriously disintegrated?
You can't take the sky from me...
Personally I'd say that the opposite is true. If our ancestors weren't as bold and daring as they were, I guess we would still huddle in that secure cave somewhere in Africa.
Fear in it's current giantic dimensions seems to be a pretty recent phenomenon. I don't think the world was explored by the most cautious of persons.
Haul it up to 36k feet, and then it takes a relatively trivial amount of energy to get it to a speed for orbit, since it isn't fighting a stronger force (gravity) at the same time. Also, if you are patient, and can take a week or a month to get the unit up to speed, it will take a very small engine (ie: efficient) to build up the necessary speed.
;-)
I know it isn't intuitively obvious, but the center of gravity of the space elevator is already traveling at orbital velocity, otherwise it wouldn't be stationairy relative to a fixed point on earth. Given this, it would take no (ZERO) energy to get a satellite from that point up to speed.
Of course, I am not sure where the actual space elevator station would be located relative to the center of gravity and I suppose that could be an issue. But I would certainly think that having it located at the center of gravity would be convenient
The reason that it can be true that 1+1 > 2 is that very peculiar nonzero value of the + operator
It's not like trying to hit a 1 square meter target... It's hitting a target 1 meter wide, but for all practicle intents and purposes, infinately long.
Pilots line up to hit the center of a runway every time they land. You don't think a terrorist could easily hit this thing within the width of a given airplane?
As far as your other point, regarding the "attractiveness" of this target from a terrorists perspective, I'm with you on that one. It's not a sexy terrorism target. Very few casualties, if any... Very low visibility on most people's radar.
It'd be a waste of time and energy for terrorists.
For those that would die defending it, Freedom
has a sweet taste that the protected will never know.
You miss. You aim the plane down at the outer ring of the pentagon and accidentally undershoot by a few feet. The plane hits low on the wall of the building and most of the energy goes into the ground instead of the structure.
Nope, not what happened.
You can clearly see that the area in front, around, and behind the small portion that was hit did not suffer from giant-fireball damage nor from kinetic heavy-plane damage.
Bonus question: Why bother faking a plane strike with a truck bomb instead of just hijacking another plane?
You're mistaken on who did the plane-faking.
Hint: It wasn't Oussama or his murdering buddies.
You can't take the sky from me...
You're not going to see sliced up half-corpses littering the city streets, either. Yes, science fiction is full of things that can slice through people... but this isn't one of them. A large structure like a space elevator would be fabricated from bundles or ribbons of carbon fiber, which would be about as sharp and dangerous as a piece of clothesline.
What would happen to a space elevator cable whose counterweight broke away? If left untended, it would eventually start to fall to earth, wrapping itself around the equator. Upper portions would fall faster, in effect cracking like a giant whip, with the end of the cable moving at large multiples of the speed of sound. This isn't likely to be as bad as it sounds, though... while the cable is likely to be strong enough in tension to deal with its life as a space elevator, it's unlikely to be strong enough to resist the stresses of orbital entry... most of it will break off and either fly away, go into some sort of orbit, or burn up. The part that doesn't break off will mostly burn up long before it hits the ground... remember, this is CARBON.
If you insist on visualizing the sort of disaster that you're worried about, read Kim Stanley Robinson's) "Mars" series... in one of the books he describes a structurally massive space elevator crashing down to the Martian equator with devastating results.
--Larry
Never attribute to malice that which is adequately explained by incompetence
We're always trying to figure out what to do with hard to dispose of, toxic, non-decomposing materials.
Once a day, we could launch this stuff at the Sun as the Earth makes it's daily rotation.
It'd be the largest "sling" ever created. David would have been impressed, and had he been armed with it, Goliath might have been a no-show.
For those that would die defending it, Freedom
has a sweet taste that the protected will never know.
Not to mention remote manupulator devices, of the sort often used in nuclear experiments... they're often called "waldoes", a reference to a Heinlein story called, simply, "Waldo", where he introduced the concept.
--Larry
Never attribute to malice that which is adequately explained by incompetence
"it's going the same angular speed as the ground"
True.
The original poster seemed to be under the impression that the atmosphere would be going past at a thousand miles an hour, and I was moved to respond.
A.
...bringing you cynical quips since 1998
"I personally hope we continue building what Sci Fi writers write about."
I'm just waiting for my light-saber.
Oh lord not this again. Yes, we must not do anything that may be a target for terrorists. Dont drive your car because there might be a car bomb. Dont fly becuase the plane might be hijacked. Tell you what, why dont you hide under your bed while the rest of us continue on with life and the building of civilization.
I'm a programmer, I don't have to spell correctly; I just have to spell consistently
Yes, the earth will slow down it's rotational speed if the elevator is constructed (and made out of material here on earth, not from space).
And everything sent up the cable will slightly slow down the earth some more.
Now where does that energy that the earth lost from it's rotation go?
It goes into lifting the new object into orbit.
That's why the cable won't fall.
Fortunatly the earth has a *LOT* of rotational energy, so the losses will be immesuarably small.
...hanging from the center of mass at geosynchronous orbit...
The way I read it, this is only the initial phase (38,000 km). Teathers are sent out in both directions, making the total length 100,000 km. When it's done, there's considerable force on the base.
You make a good point about where the break in the teather is made. But if more of the teather is beyond the 38,000 km mark, there's less of a chance that even a high break would cause a problem.
Oh well. So much for arm chair orbital mechanics, right?
A programmer is a machine for converting coffee into code.
So even at 100KPH it takes 15 days up or down?
I'd imagine that theme would get old on the way up.
Baaaaaaaa....
Baaadaaaaa....
Baaaaaadaaaaa...
BAAADAAAA BUM BUM BUM BUM BUM BUM BUM
i mean jeez.
You like your new Mac more than you like me, don't you, Dave? Dave? I asked...She said Yes.
Nasa played around with dragging wires through the atmosphere to generate static electricity.
This thing will could possibly generate HUGE amounts of SE as the atmosphere whizzes past it 24/7. Are there plans to capture and use this electricity or what??
For one, it's not static electricity... it's just electricity. The current is flowing through the wire (thus it is not static). This experiment was just the shuttle dangling a very long wire from the space shuttle in order to generate electricity due to a neat effect that happends when you move a wire through an electromagnetic field (in this case, the earth's). Sadly, the wire broke and the experiment was dumped (to my best knowledge).
Since this space elevator will NOT be moving with respect to the earths magnetosphere, this will generate no (non-static) electricity.
But how will they protect it from, well, planes at altitudes below 100,000 feet?
Rockets!! Big, impressive, reusable, airplane-shaped rockets with MetalStorm cannons!
most of it would end up burning up in the atmosphere.
It had better.
Imagine the difference between a neatly wound spool of string in your kitchen drawer, and the same string unspooled and thrown in willy-nilly.
Oceanographers already deal with this problem with cable deployed instruments. Sometimes the cable tangles, and although it fit neatly onto a spool on the deck of the ship, the tangle can sometimes be several times larger than the ship.
If ten or fifteen miles of cable made it to the ground, it could still be an enormous enginering problem to clean up.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
For one thing - this is strong stuff we're talking about - incineration is garuanteed. If it breaks up that might sound like an imporovement - but the it's like being shot with a shotgun. It may be loaded with pellets, or it may be loaded with solid rounds. You may spead the impact a little, but its the kinetic energy that'll kill you - and you still get all of that.
Not scared yet? Let's put this in perspective.
according to its website the Golden Gate bridge weighs 380,800,000 kg and spans 1966m. That's probably comparable to the weight/length ratio for a space elevator. It uses hi-tech materials, but it has to support its own weight across its entire length, and its going to be long! According to Nasa (google cache) the elevator is likely reach 36,000,000m. That's 18,311 times the length of the GGB
So taking the golden gate bridge as a guide, we can estimate the total weight of the cable at 18,311 x 380,800,000kg = 6.97 x 10^12. Seven gigatonnes - lighter than I expected.
How hard is it going to hit? Well, at least terminal velocity. I say "at least because the upper reaches will be going faster and have to be slowed by the atmosphere. Also the cable will be considerably denser than a human, so we can reckon it's terminal v as being rather more than a human's. Human terminal v is about 50m/s so let's go with that for the time being. We're being conservative..
Kinetic energy = 0,5 x mass x velocity x velocity
= 6.97294 x 10^12 x 50 x 50 / 2
= 8.716175 x 10^15 joules
And to put that in perspective, one megaton comes to about 4.184 x 10^15 Joules.
So if the cable came crashing down it'd release about 2 Megatons of kinetic energy - either as heat as it burnt up, or as shockwaves on impact.
Doesn't sound like much? Well, the Hiroshima bomb is reckoned as being 20 killotonnes yeild. So 200 hundred hiroshima bombs going off in a ring around the equator in fairly rapid succession.
and it it hits faster than that... well that's a square term. 100m/s give you 4 time the energy or 800 hiroshima bombs. 200m/s (not unreasonable) gives 16 times - 3,200 x hiroshima.
Don't get me wrong - I'd love to see a space elevator. Just let's bear in mind that this is dangerous
Don't let THEM immanentize the Eschaton!
The problem there is Carbon monoxide. CO2 is not poisonous. It can suffocate you by excluding oxygen but most garages are draughty. Anyway, doesn't your car have a catalytic converter?
I'll see your Constitution and raise you a Queen.
At the pentagon, any remnants of the plane would be right there.
Right WHERE?
Look at the width of that hole (that wasn't the original damage, the original damage was much smaller, this is after the collapse during the fire). You do know that planes have wings right? Where did the wings hit? Where did the fireball go?
Look at footage of the second plane hitting the second tower. You can see what happens when a boeing hits a building, and you can see what happens aftewards.
Look at the pictures of the pentagon, you can see, with your own eyes that that isn't what happened.
I'm not telling you to take my word on it here, I'm telling you look for yourself.
You can't take the sky from me...
Actually, dropping marbles (carefully) from multi-story buildings is an amusing experiment.
You tried it?
Did you try with different sizes of marbles? Because I know the small ones are pretty hard to break, but when I was a kid I had some large ones break in my marble bag...
You can't take the sky from me...
"the floating base platform would be placed hundreds of miles from aircraft routes and shipping lanes and would be in a region of the sea where storms, lightning and high waves are rare." I understand that they are concerned about access, but in reality it's a waste of time and money. Any sufficiently useful transport technology has historically generated growth and traffic around itself. Instead of having to deal with restricted and obscure access routes, these elevators should be dropped into the major trade centers of the world. Ports bring boats, airplanes, highways and trains all into one place. The next logical step is to include access to space. If the space elevator is built in the middle of the pacific ocean, the next great challenge will be to supply a floating airport and direct shipping routes...
As an added precaution, it could be wired up with some bright red blinking LED arrays. =)
Daniel J. Kelly
The cable is under tension. I presume the bit above the break would shoot up into space. The remaining few thousand metres, below the impact, would go down. This lower part wouldn't do a lot of damage. It would be a bit tough on the people on the top end though. They would immediately fall into space!
I'll see your Constitution and raise you a Queen.
I meant "incineration is not garuanteed. Been a long week...
Don't let THEM immanentize the Eschaton!
You imply that the US military shot the plane down. If this is true, there would have been a report of a plane crash (ala the other plane (90??) that the passengers revolted on.)
Considering the media frenzy at that time, I would assume it would have been covered in the media if it happened.
The media did report it. They said it crashed on the pentagon.
</obvious>
I don't recall hearing of any such thing.
You haven't heard the story about the plane hitting the pentagon? Where have you been the last 2 years???
</sarcasm>
I don't recall hearing of any such thing.
Therefore, it did not happen.
Step right up folks! Come see the Amazing All Knowing Anonymous Coward! Only 25 cents ladies and gents! If he hasn't heard of it, it doesn't exist! Step right up!
</carnie>
You can't take the sky from me...
I only tried standard size marbles. I didn't have any of the big ones. I forget how many floors up I was. It would be interesting to see how high you could go...
Are you saying that flying a plane into will not harm it, or that the effect of destroying it will mean very little in the grand scheme of things?
The ribbon will have tremendous tensile strength, but that doesn't mean it would stand up to an impact of that sort.
For example, a fiber optic strand is very strong. Pulling on it from it's ends, it takes a lot of force to pull it apart. However, if you apply just a little force creating a narrow bend, it'll snap with almost no effort at all.
I don't know enough about carbon nano-tubes to determine how it would hold up, nor to gauge how strong they are in relation to specific types of force, and how those forces are applied.
That said, I'm pretty sure that flying a large aircraft into it at a speed upwards of 500 mph would definately cause some trouble.
For those that would die defending it, Freedom
has a sweet taste that the protected will never know.
--- I am known for the ones who want to find me on the net. Is that a privacy risk or a privilege? One might wonder..
There's also a space elevator in some Heinlein's later work. Specifically there is the 'Kenya Beanstalk' in "Friday", which was clearly an elevator.
In my universe I'm perfectly normal, it's not my fault you don't live in my universe.
OK, I did a little computation.
The height of the pentagon is ~77 feet
From these pictures under extra info at cnn. The first three explosion shots at a guessed 30/sec frame rate show an explosion expanding at one building height every 2 frames, or 77*30/2= ~1155 ft/sec, not unreasonable for a fuel air explosion. Now, the low end air speed of an approaching plane is 250 and the high end is 600 mph that means that the plane was moving at ~1000 ft/sec at the fastest and should have been viewable for three or four frames. So were are the images of the impacting plane?
Further the explosion originates at the outer edge of the building and shows no forward momentum in the debris expansion as would be expected of a frontal impact.
Your point being?
You can't take the sky from me...
Note also that all of the techniques you described could be used to attack a conventional launch of a Shuttle, too.
~Idarubicin
Karma: Excellent (My Karma? I wish...:-( )
I don't know how much you can move the base station, but it's an interesting idea.
Bad differences between this and the space shuttle. The space shuttle is really only vulnerable during launch and so we can expect to have 24x7x30 days of high security around. If we lose one that is unmanned, just sitting on the pad, then we are very angry, but it's replaceable. The elevator at $7B per (actually not that much more expensive than the shuttle) is a sitting duck, and vulnerable 24x7xforever.
Good differences: because it is on one location very far from the mainland, and vulnerable 24x7xforever, it's reasonable to sink lots of money into anti-aircraft weaponry, anti-missile weaponry and the like.
By the way, I'd love to see this thing built.
a) the pentagon was a much more dense building than the wtc. The wtc was a very lightweight construction on the interior and it makes sense that a plane hitting it would go most of the way through and some parts would come out the other side.
Indeed, you can even see debris flying out of the WTC when the second plane hits.
b) that first image you posted that is being used as evidence of there not being a big hole from the initial impact, is a picture of the area to the side of the impact, not the impact site itself. Compare some of the structual features in that pic to a pic of the whole side of the building.
Here's a better pic of the scene.
c) The pentagon was made of steel and concrete. The WTC was made of a steel outer shell and much lighter materials on the inside. The planes that hit the WTC only had to go through the outer wall then it was fairly clear sailing. The pentagon on the other hand, was much denser construction and a plane blowing through it would have been ripped to shreds. There wouldn't be any large pieces left, and what pieces there were would be buried in the rubble of the building, not laying out on the lawn for everyone to take pictures of.
Look at the above picture.
Where did the wings hit?
You can't take the sky from me...
I was lucky enough to attend Sir Arthur C. Clarke's live feed from Sri Lanka: he was in great spirits and answered a myriad of questions.
:)
My favorite was, when someone asked if he had the opprotunity to be a space tourist, where would he want to end up, and his answer was:
Mars, of course. I'm convinced that there is life on Mars. New photographs have shown what looks like possible vegetation, and where there's vegtation there's bound to be something nibbling on it.
And incredible opprotunity to hear such a legend speak so informally to a small crowd, it was worth every minute of getting up at the buttcrack of dawn to see
Tower of Babel, Religous Fundamentalisim, nuff said.
- It was the best of times, it was the blurst of times. Stupid Monkey!!
Clarke once said "the elevator will be built 50 years after people stop laughing".
This morning he was so bold as to say that this might actually be the time when people have stopped laughing, but then he promptly redacted and reducded the figure to 10 years from now instead of 50. So there is still hope, and all the conference attendees are quite excited about that hope.
It wouldn't end up "piled up"...because the earth is rotating beneath it, it would spool around the planet. And assuming that the cable was 20m thick, fell and wrapped around the Earth why not just build around it as necessary?
blog |
How do you gain traction on the cable without damaging it? Just throwing a rope up isn't enough, you need to be able to climb it as well. If you start with a 1m x 0.3m cable, then sloughing even a tiny amount of cable material as you climb or descend is going to chew though it quickly.
If you were blocking sigs, you wouldn't have to read this.
no, it doesn't. Indoor in the winter is a great time to generate enough static to POP when you touch a door knob, or someone else. It does hurt a little if you do it right. You 'almost' touch them in their under arm area, ear or nose, back of leg, or other sensitive area. If you lived where it gets really cold, you would have done this as a kid.
:D
We used to surf around the house in socks, sliding to build up static to do this, when the outside temp is low enough (making it relatively hotter in the house, thus, ultra low humidity). It works best if you are just coming inside and you are dry. You only get one or two good times, before your potential levels out. We didn't understand how, we just knew we could, and Mom would get pissed if you do it on purpose
Tequila: It's not just for breakfast anymore!
Think of the diseases caused by asbestos, asbestosis....
But its pure carbon. And its out in ocean, a thousand miles from anyone. I mean, sure, I'm all ears if you have any data, but you get worse standing in a corn field in Iowa on a clear day.
Tequila: It's not just for breakfast anymore!
... Can anyone tell me what the mass of this cable will be, and either, how we're going to get the carbon to the geosynchronous point, or alternatively how much rocket fuel it'll take us to launch all this carbon up to the geosynchronous point?
Just a thought here... maybe we want to be doing our first construction upwards for a super-high, wide-base rocketry launch tower, instead of starting in space. That way, we could minimize the amount of fuel we spend building the thing.
Sorry, I know it seems stupid, but sometimes thinking gets in the way of the reality we want. Still, it might be worthwhile to think this thing through before we beg... aaw, what the hey, let's just do it. If Arnold Schwarzenegger can ignore any significant facts, so can we.
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
Bear in mind, though, that the cable isn't guaranteed to come straight down onto the orginating point... It's going to come down at an angle, probably with the rotation of the Earth -- the lower half would, anyway.
:-)
The force of the impact will change along the length of the elevator cable, depending on two factors: the speed of that section and the mass of that section.
See, it's not all going to hit in one place at once -- an object will take a LONG time to fall from geosynchronous orbit to the surface of the Earth.
So let's say the elevator gets cut at that point. Immediately, the cable goes slack (nothing above geosynch to pull on it) and begins to collapse. Now, if it's anchored to the Earth and the Earth is rotating beneath it, the first portion of the cable is going to fall to the west, and it going to continue to fall westward. You have to view the cable, however, as a chain of points...each point having a certain mass and a certain velocity, both of which will change.
The velocity will change based on how long that segment had to fall before hitting the surface (point 0 on the cable doesn't have to fall at all) PLUS the velocity added to it as the segment before it pulls it closer to the surface. Pretty complex, eh? As an example, if the length of the cable were such that it could wrap around the equator twice and atmospheric friction were not a concern, the second wrapping of the cable would go markedly faster than the first because the remaining cable to fall would be less massive than what was already on the ground pulling on it.
In regards to mass, the acceleration due to gravity would be consistent, but the cable can still lose mass through atmospheric friction, plus the fact that large segments are already on the ground elsewhere and are not contributing to the force of the impact at a given location.
Don't get me wrong -- if this thing were to fall, it would be messy, but let's bear in mind that the energy expended would be spread out across the lenght of the cable, and not a localized effect. Would it be messy? Undoubtably. How messy remains to be seen, of course. I just think that the two factors of the velocity of the impact and the mass impacting at a given location changing over time is going to play havoc with your calculations.
But then again, I have an English degree...what do I know?
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I can't really disagree with you, but I note that liftport thinks it's an interesting question....
As I refrain from arguing with myself I note I really meant to attach that reply to the other response.
Why are you reading this?
Dude, now the terrorists know about his bed.
Actually, the original article states that the concept "first gained *widespread* attention when the science fiction writer Arthur C Clarke described it in his 1979 novel Fountains of Paradise".
The concept had been invented independently both in USA and the Soviet Union long before the book was written -Arthur C. Clarke's great contribution is bringing the concept to a wider audience. (The cosmonaut Leonov had actually made a painting depicting a space elevator, but westerners -ignorant of the concept studies being done- thought he was nuts)
BTW, I was in contact with ACC two yeras ago and asked him about this novel. He mentioned that the scientist who helped him with the facts was non other than Buckminster Fuller, the discoverer of "buckminsterfullerene".
It so happens that the carbon nanotubes which have the tensile strength to make the cable possible are simply tubular versions of buckminsterfullerene. Fuller himself was not aware of this ironic fact, the nanotubes were only produced in the lab and had their strength measured in the nineties, after Buckminster Fuller's death.
Yours Birger Johansson
From http://www.snopes.com/rumors/pentagon.htm
Anything else I can help you with?
That cable will wick the atmosphere out into space. My god, someone stop those idiots before they kill us all.
They are called the Lagrangian points.
L1-L3 are on the earth-sun line but aren't stable. L4 and L5, which lie in earth orbit +/- 60 dgrees, are! And all of them orbit earth in a year. (of course, the centers of the orbits aren't earth, they're close to the sun, but they still take a circular path arround us every year).
NASA is currently using L1 (SOHO, ACE) with plans to use L2 for deep space observations.
Of course none of these are practical for a stationary elivator because the earth spins faster than 1/year (unless the end 'dangles' over the equator and moves east-west). And they are too far away.
"You saved 1968." - Ms. Valerie Pringle to the crew of Apollo 8
From what I've head, a space elevator is a bad idea in the sense that the atmosphere has a singificant EMF gradient between the surface of the earth and far up in the atmomsphere. Completion of such a device would case the world's largest lightning bolt ever. You'd be basically creating the largest "short" ever.
If you want to stop the problem, you add a non-conductive section to the elevator every few dozen miles. This reduces your payload weight for a given size elevator (or equivalently requires a heavier elevator for a given size payload), but would let you keep the current flow in the sections between insulators low enough that it would just keep the elevator material warm.
If you want to exploit the opportunity, you put a battery in each of those insulator sections, and you use the voltage between one section and the next to recharge the battery, which in turn recharges the elevator cars as they pass it on the cable. At the least you could reduce the energy costs (which would still be several dollars per pound of payload) to run the system, and at best you could sell excess power at the base station.
I did an analysis of the tension way back when Clarks book came out. Hard to imagine that was in 79. I can still visualize buying it, like it happened yesterday. Boy I feel old :( Anyway, you need to balance the force of gravity, with angular momentum. The class of problems this belong to is called differential gravitation. Look for discusions about the analysis of "Tidal Force".
Ya know, thinking about this I don't think that in the event of some kind of failure we are going to have any kind of "re-entry burn up". IANAOrbital Mechanics Engineer but re-entry burn up is caused by something entering the atmosphere traveling in a lateral motion reletive to earth surface. This thing is in GeoSynch orbit. It has 0 lateral motion relative to surface and hence 0 motion relative to air that causes friction) it would not burn-up, Right?
What did come to mind is this thing IS going to be crossing the ionispere. With all those charged particals running around up there aren't they going to see this thing as the mother of all grounding/lightning rods?
[humor]We could ground out the entire natural earth electrical system. CHAOS! PANIC! No more schumann resonance! We will all go insane![/humor]
Seriously, what are the considerations for this? Anyone? Anyone? Class. Anyone?
I been having problems with ground faults.
Now, I have to worry about sky faults too!!
And with 75 Mega-new-Tons. If this thing gets a short, it will be Hiroshima all over again.
Make world stop, I want to get off.
There's useful web based app here which, using my previous assumptions, gives a total potential energy for the entire cable of 67 x 10^15 Joules
So, given 1 megaton is approx equal to 4x10^15. that still works out at about 16 megatonnes. The difference this time is that the calculation is of the potential energy due ot gravity of the cable. If it comes down - this is how much energy will be released.
As for speed, remember that different parts of the cable all want to travel at the orbital velocity for their height - so the earth's rotation will tend to wrap the cable around the equator, accellerating all the time as you pointed out. It might take days - I have no idea how to calculate it. I doubt it would take more than a week all told.
But my degree is in software, not hardware. Any rocket scientist want to set us both straight?
Don't let THEM immanentize the Eschaton!
100,000 km vs 3 cm? So we're only off by 10 orders of magnitude. It sounds like a bit more than "not quite there" to me. However, I don't need to worry about that problem. I'll just be kicking it at my compound in the Bahamas, counting the money that I made by selling time-shares on the space elevator to slashdotters.
I'm assuming that the "troll" rating you got earlier was a misrepresentation, since you haven't been rated as one recently.
Earth spins at a constant angular rate. By using a 100,000 km ribbon, the velocity at the end is... 7.27 km/sec. Also, you'll note that as you get further out the force from gravity decreases. At that distance, the acceleration due to gravity is around 1/500 the gravity at the surface of the earth.
You'll notice that planets further from the sun orbit at much lower angular velocities, a couple of hundredths the rate of earth.
Another example is the Moon. It is a few hundred thousand km away, but it takes 28 days to move around the earth. This thing will be a good chunk of that distance and spin 28 times faster. Seems like plenty to me.
Satellites in low earth orbit go around once every 90 minutes or so, but ones in the much higher geosynchronous orbits go around only once per day.
Don't Bogart the fish sticks
From http://www.snopes.com/rumors/pentagon.htm
also:
Also:
Aww, hell, just read the whole fricking page yerself!
On the other hand, the $7B bill is mostly for elevator-building infrastructure, not the elevator itself. Once you've built one elevator the next will be much cheaper. By the time someone sufficiently bitter and twisted destroys the first elevator, it would be an annoyance rather than a tragedy.
And, yes, I know that you certainly know that. It was a joke, too. :-)
Karma: Excellent (My Karma? I wish...:-( )
It isn't static electricity, but NASA hasn't given up on uses for cables or the energy they can harness. From the October 2003 issue of Discover Magazine: NASA is funding a joint project with the Harvard Smithsonian Center for Astrophysics to create "ProSeds." In it's simplest form, this is a wire tethered by a cable to a second stage Delta 2 rocket. The wire dangles into Earth's ionosphere and "sucks up electrons." The resulting current causes an electromagnetic "drag" - kind of like a break - that pulls the rocket into a lower orbit. By running a current the other direction, the drag could be reversed and the rocket could be "pushed" into a higher orbit. At least theoretically. There are other proposed applications for the technology, including moving a space station between orbits.
Remember: anything not compulsory is forbidden.
Your also forgetting it's uses in destroying delicate electrical equipment. This is actually a fairly serious concern for the space elevator, grounding the line.
:-) Lighting is a massive manifestation of static electricity.
Oh yeah, one other great use for static electricty is power time machines indicentally teathered to clock towers (Back to the Future)
-------- -------- Support Wesley Clark for president!!!
"we don't have organized, allowed racial hatred groups in Europe...." I just fell off my chair laughing. Nazis, what where? Neo-Nazis, no no not in Europe. Now, I don't agree with your original statement, nor the first reply. But, to say that Europe is now perfect happy little place is rediculous. You have thousands of years of experience and knowledge made up of wars, intolerance and genocide. During the last century Europe was embroiled in more than 20 separate conflicts including the World Wars. Europe was the center of all the colonization and imperial movements with the exception of the Ottoman Empire and is the cause for a myriad of major conflicts currently. Want to know why Afghanistan is still screwed up? Or the entire continent of Africa? Or hey, even the situations in the Middle-East? At the heart of every problem is a European country. Now, the USA should be better, we should use fewer resources, we should eat less, we should actually pay more lip-service to treaties like the Europeans do, and we really need to stop saving the Europeans from themselves. Europe is at a point where it can become a redeeming influence in world politics, but so far it has been content to watch from afar, letting Serbians butcher Bosnians, letting Hutsi slaughter Tutsis, and allowing the Taliban to sink Afghanistan back into feudalism. Just to name a few. Europeans have done nothing but blather and worry, and in those cases when the US has become involved you simply wait for us to make a mistake and then cry "imperialists!" at the top of your lungs. So far, Europe, I am not exactly impressed.
Anyone who whines about being modded down should be.
Nice job. However for carbon nanotubes, people have already calculated tension to be in the order of 0.1 TN (65 GN, to be exact), about three orders of magnitude larger than you estimate. I guess the culprit is not that you are using an incorrect density estimate (which won't chane the result even by a single order) but you are missing the rope's mass profile: it will be V shaped to be light at low tension regions and thick and though at high tension regions.
Please remember the cable is under TENSION, from the anchor mass. A break in the atmosphere or low earth orbit (from that plane or low orbital junk) will result in most of the mass moving away from the Earth, rather than toward it.
Second, the energy from whatever part of the cable is 'crashing down' will be dissapated over the length of the cable, and over a period of time as the cable fragment strikes the atmosphere. That is very different from the near instantaneous point release of energy of a weapon.
There are other proposed applications for the technology, including moving a space station between orbits.
Two problems with this.
First, the space station is in HIGH earth orbit. The required cable would be quite long AND extert a fair amount of drag. The rocket power required to BOOST the the cable to the station would be more than delivering the obvious to the station: rocket fuel.
Second, electricity does not make propulsion. Some more advanced technology would be necessary to turn electricity into propulsion. Dragging something with a wire is a lot different than PUSHING something with a wire. I guess it would have to be a really STIFF wire.
Beyond that, I would suspect that SOLAR power could be used to generate a LOT more electricity. Furthermore, deploying a solar sail and the correct orientation could effectivly drag a station into a higher orbit. In one orbit, it wouldn't do much, but over the course of hundreds of orbits, it would probably do pretty well. Whether it would be cheaper than PORF (Plain Old Rocket Fuel) would need analysis.
-------- -------- Support Wesley Clark for president!!!
The centripetal force is enough to keep it up there. A counter-weight on the far end dictates how much you can lift. The earth is spinning at a very fast speed. Once you put an object outside the atmosphere, it should stay in one place and be relatively stable. There will be some vibration and movement, but nothing a light set of thrusters at the top can't handle. You are right of course, if you try to pull up a weight that is heavier than the CP and the counterweight, it will pull it down.
"Curiosity killed the cat, but for a while I was a suspect."- Steven Wright
"Invention, my dear friends, is 93% perspiration, 6% electricity, 4% evaporation, and 2% butterscotch ripple."
Paint it blue?
I'd probably be more concerned about all of the junk that is whizzing around the planet above 100,000 ft.
Siggy Sig Sig? Where is the sig?
It seems to me that the splicing problem is much more than a minor obstacle. Nanotubes are connected by a lattice of covalent carbon-carbon bonds, stabilized by aromaticity. That's the reason why nanotubes have such a phenomenal tensile strength when you scale a microscopic tube to macroscopic dimensions.
When you try to make a rope out of a bunch of microscopic fibers, you have just another composite material. In order to make it work, you need to splice the fibers with multiple covalent bonds, just as strong as the fiber.
Then there's the problem of spaghetti. I forget how long DNA in a gene is when you stretch it end to end, but it's long. Why don't you see long DNA ropes? The stuff basically tangles up in a knot. I don't know what the radius of gyration of a nanotube is, but they will also flex.
The real problem is that you need a straight chain, 100,000 km long that's all covalently bound. Right now, it doesn't exist.
Then there are a huge number of other obstacles. Like where do you start building the thing?
The point of the whole concept is that it's self supporting; you can't start on Earth and go up, because it would never support itself before you get past geocentric orbit.
Therefore, you need to start at geocentric orbit and build up and down at such a rate that the whole thing stays in geocentric orbit. Then you need to keep the thing stable when gets deep enough into the atmosphere to encounter weather.
It's one thing to through a couple of hundred $K at it for a feasibility study, but if people are seriously asking for $7 billion, they're nuts.
Are advanced composite materials using nanotubes worthy of government funding? Yes. But let's scale up to rocket motors on the federal dollar with spin-offs like tennis rackets to make the technology cheap before we worry about space elevators.
A plane traveling at that speed with that much fuel would be INCINERATED upon impact.
;-)
Although airframes are very sturdy when used under standard conditions, they are acutally a lot light a tin can when exposed to "unusual" stresses. The perimeter of the pentagon is a farily thick layer of steel reinforced concrete with a facade of Indiana limestone (best in the world
Have you ever seen a rocket sled impact tests on outdated jets. It's pretty humorous because the impact surfaces aren't as wide as the jets. The internal structure of the plane vaporizes on impact. The wing tips continue without the plane as if nothing had happened.
Nothing but the strongest of structures like the data recorder would be found under these circumstances.
-------- -------- Support Wesley Clark for president!!!
You're halfway there - I envision a 100,000km vertically scrolling marquee!
Outside of a dog, a book is man's best friend. Inside a dog it's too dark to read. - Groucho Marx
Okay,
so this thing is made up of small tubes.
Has anyone thought of the consequences of anchoring this thing in the middle of the Pacific ocean??
Can anyone spell capilliary action or syphon??
You fools!!! You'd have all of these tiny tubes sucking the world's oceans dry and spewing them out into space!!!
I'm off to start stocking piling bottled water, before it too late.
Siggy Sig Sig? Where is the sig?
Similarly, if it breaks from the orbital anchor point then thge whole thing comes down.
If it breaks somewhere along its length then we get a mixture of the two. This is the most likely scenario. How many petajoules do you want to wager?
Don't let THEM immanentize the Eschaton!
OK, so these folks think they can move the base station to avoid space junk. That sounds extremely tricky already. But I wonder what they can do about meteorites and other smaller stuff that comes in much larger batches? The cable may be able to take one or two hits from these little buggers, but it's going to sustain *some* damage!
Well, we could always use it for propulsion. Make the counterweight a giant shirt and the elevator out of socks and the elevator will shoot right up there.
I'm not shy, I'm stalking my prey
Hmmm... that might be correct, that after one is built it's not nearly as big to build another. But if one does go down, whether from sabotage or accident, I can't imagine it would be just annoying.
Man, I can't imagine at all what would happen if something bad happened to one of these. If the center of mass if at geostationary orbit, would it fall over? spin off to space? Slowly fall and drag over a couple continents?
I dunno, but it would be a bit more than annoying would be my guess...
j
Linux: Imagine SCO.
Run and catch, run and catch, the lamb is caught in the blackberry patch.
Yes, but will they have an interstellar Muzak version of the "Girl from Ipanema" playing as you ride the elevator up?
Wind. Duh.
Moderate drunk! It's more fun that way!
Second, I have a Master's degree in electrical and computer engineering. I know about static electricity.
Third, the POP occurs when the charge you have built up travels to your victim. Travelling charge is a current; it is not static because--guess what--it's travelling. It is static before the POP, but if it stayed static, there'd be no POP at all.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
...15 days on the way up? Wow, that would give pleny of time to join the mile high club. And the 10 mile high club. And the 20 mile high club. And ...
Hope that helps
Cheers
Ish
While it has 0 lateral motion WRT the surface, it is still in orbit.
As sections of the cable drop lower, their orbital velocity will increase WRT the ground, and the cable will try to "wrap" itself around the planet.
By the time that most of the cable hits thicker atmosphere, it will be going at a pretty good clip, and will burn up (even the light, "fluttery" ribbon sections).
Here is an experiment that you can try in the safety of your own home to verify this:
- Evacuate all of the air from a room (to prevent stray air currents from skewing the results).
- Drop a ball from a height of, say, 6-10 ft or so.
- Note where the ball landed WRT its release point.
You will see that the ball landed several microns East of its release point (and a few microns toward the equator, as well).A few microns might not sound like much, but multiplied out to 36,000 miles, that's a lot of microns.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
You can harness it's awesome powers to make inflated balloons stick to the ceiling, after you rub them on your head.
I'm bald, you insensitive clod!
A 100,000km elevator brings a few interesting questions.
Such as,
What will happen in an emergency? - Will there be emergency escape pods every few KMs in case something bad happens
How fast is this thing going to travel? A person would hate to be trapped in an elevator for too long (if it comes to transporting persons) - you would need to bring up food/water as well.
Terrorists and acts Terrorism - Screening of people entering the elevator and aircraft (WTC anyone?)
The moon has much lower gravity, so we should build this thing on the Moon first, as a "proof of concept". The materials would not have to be as strong, nor the Elevator as long.
The really exciting will no longer be GETTING into orbit, but rather what we can do once we get there.
I remember reading a science fiction novel a loooong time ago about the effect of zero gravity on boobs. Anyone else read the same book?
Duh. Just found the answer to my own question; it was "Rendezvous with Rama", by some guy (-5, Troll), noted in the link above.
ummm. Still not getting it. Why should it increase its angular velocity. At lower orbits (ie shuttle) you have to have higher angular velocity to maintain orbit. We don't want the end of this rope to maintain orbit, we want it to lower down. the angular velocity would remain the same 360deg/day.
have any thoughts on the ionisphere issue? I'll think some more on your experment. I am thinking that it is not quite the same. It would be more like lowering a rope from the top of a tall building. A really tall building. The top of the building has a slightly faster linear velocity than the base relative the the gravity well but the same angular velocity. The rope dosen't care, it just wants to get to the bottom of the gravity well. Your ball being dropped is not being influenced by anything during transit from top to bottom (except grav) but the rope is. Hmmmm. I'm not getting this.
...we can estimate the total weight of the cable at 18,311 x 380,800,000kg = 6.97 x 10^12. Seven gigatons...
...you don't work for NASA, do you?
Except that the GGB is make of steel and concrete, and the space elevator ribbon would be made out of a nanotube/epoxy material. Which, according to ISR, would weigh only about 7.5 kg per km.
If the space elevator is 36,000km - which is kinda short if I'm not mistaken, so let's be conservative and say it's 100,000km - would weigh only 750,000 kg... (about 850 emperial tons).
Following your math: 750000 x 0.5 x 50 x 50 = 937,500,000 Joules.
So you're only off by a factor of 4.5 million.
And not only is the TOTAL energy about 0.0000002 times what you thought it was, but such a relatively light (7.5 grams per meter! That's practically tissue paper...) and FLAT, THIN ribbon would have horrible aerodynamics and dissipate much of it's energy in churning the air. I'd say a conservative terminal velocity for this stuff would be no more than 5 m/s. So now it's kinetic energy drops by another factor of 100!
Here's an experiment, with Halloween not too far away... throw a roll of toilet paper so that it unwinds and watch how fast the ribbon of paper falls even with a heavy weight (remaining roll) on one end of it. Now imagine something that has about the same density but is at least five or six times wider (not thicker)...
Given that, whatever was out in space (no air resistance) will probably reach a speed fast enough to burn up, but the majority of it will probably make it to the ground. And when it does, I think the damage would be pretty minimal...
=Smidge=
Imagine a harp with only 1 string, but some 10'000 km long and the wind as a musician. There would be a huge tension in the cable (after all it carries all the weight of the lower part), but it wouldn't be straight either, somehow more parabolic, the earth rotating the cable through the universe. If the wind is able to destroy bridges by stimulating their resonance frequency, I'm sure that this cable would vibrate a lot (like the harp string, but oscilating kilometers instead of mere millimeters)
As a boy I used to play with a steel cable going up the Swiss mountains, a kind of cable car. The cable hung freely in the air for over 1 km. I pulled with all my weight and let it go. It took some seconds and the impulse came back, so strong impossible for me to hold the cable. It run up and down the mountain many times until it vanished. Imagine the wind pulling and pushing this very long cable and all the impulses running up and down. Forget a smooth ride up there.
Well, all I know is I first heard of the concept of a space elevator in Charlie And The Great Glass Elevator. Hope they design in some protection against those vermicious knids.
- First they ignore you, then they laugh at you, then ???, then profit.
whenever I hear about bold projects, I always hate it when they are discussed. I really wish that there would be some committment. Stop the endless chatter about the "possibility" of doing it, just say we will do this. Even if it fails something most likely has been learned.
<P>Even if the project may have questionable value at the time doesn't mean that it is useless. At time of invention the airplane was pretty useless too.</P>
It has some obvious mistakes like:
> At about a third of the way along the cable -
> 36,000km from Earth - objects take a year to
>complete a full orbit.
Should be : 24 hour to complete a full orbit
>The biggest hazard could be space junk, but Dr
>Edwards said the floating platform would be moved
>around to steer the cable out of the way
Hmm. I would like to see them:
1. Tracing space junk ~0.01-1mm in size
which flies around with a speed ~10km/sec.
2. Moving platform fast enough on the ground
to avoid collision at the altitude
~200 -1000 km . At those altitudes junk
has the maximum density.
> Edwards, who estimates it would take about $7bn
> (4.4bn) to turn the concept into reality
This thing should weight no less then ISS.
Most of it flies much higher orbit:
36,000-100,000km compare to ~500km for ISS,-
READ: more expensive to get there.
Now check the web about ISS price tag.
Reminds me the story with cheap Space
Shuttle for $5.6 +/- 1.0 bn.
Either article is bad or this guy is full of @#$%.
Pessimist is a well informed optimist.
Then what happens ?
What if that guy and his group of fanatics decided to cut loose that robe ?
What type of catastrophy will that cause ?
No, I am not saying that we shouldn't innovate just because of what a bunch of loony Moslems might do, but we owe it to ourselves to think about the possible consequences ?
We _are_ living in a world where a certain world-religion is actively advocating to kill all the "infidels" - aside from what they have done in NYC that fateful day 2 years ago, they are still killing the "infidels" (aka Christians) in Indonesia and Sudan and Nigeria.
We just gotta be careful, be extra careful nowaday.
Muchas Gracias, Señor Edward Snowden !
*cough* Sep 11 *cough*
chl
The only sure-fire way to fight the terrorists is to wipe them out, completely.
There's no place in _any_ society, and no reason whatsoever, to let the terrorists continue to terrorize all of us.
The only problem we have so far is that the world community has absolutely _NO_ will to really fight the terrorists.
Terrorists won't go away just because we wish them to.
Those who were responsibled for the Bali bombing in Indonesia were still yelling "Allah the greatest" in their trial, despite having washed their hands and soul with the bloods and guts of over 200 innocent people.
And look at the PLO - I don't care what they say - killing women and children in the name of "liberation" isn't liberation at all. And killing the Jews (or whoever) in the name of their God only confirms to the world that their "God" is the Devil himself.
The only way to deal with those terrorists is to send them back to their "God" - and make them stay there, forever.
Muchas Gracias, Señor Edward Snowden !
It's much more correct to say that the only way we'll be able to detect that the elevator has fallen is by noticing that it's no longer there.
What the hell are you talking about? Last time I checked, the Earth has been rotating around the same axis since....the beginning of time?
CAn'T CompreHend SARcaSm?
You say the cable is actually pulling up. Okay, I buy that. However, once the cable breaks, the part under the break is going to go *down*, because its average orbital velocity is going to be less than that required to pull it up.
So if it breaks, the part above is going to pull up, the the part below is going to fall down.
Now, the next question is where it's likely to break. If it's breaking due to terrorist attack (a la 9-11) , then I think the effects will be minimal, except that you're going to get a burning ribbon whipping through the atmosphere in circles. First, it will pull up, and start moving with the sun, but faster (E to W). Then, due to wind currents, that's going to pull *back* on the ribbon from its expected orbital position, resulting in a rotation towards the earth, but a higher altitude. As this happens, it's going to break several more times, and start to pull farther out.
Yet this process is going to result in an elliptic orbit, since it's going to represent several unit impulses. Further, the rotation is going to bring the much larger top into the lower position. Add to that the effect of wind currents as it whips through the atmosphere, and it'll be tumbling slightly as the formerly top part of the ribbon slices into the atmosphere at high mach speeds.
At that point, it breaks again, resulting in it bouncing up again, but in an even more eliptical orbit... you see, this gets to be a bit of a mess. A very expensive mess, because it's going to be completely unusable when it's all done.
For thise reason, I still say that it is far better to use nanotube technology and pyrimiding construction techniques to build super-high launch pads, than to use normal rockets to launch materials for a ribbon elevator.
At least, if you build these up as high as you can, you can (1) have a much smaller ribbon (2) have a self-supporting structure below the broken section (3) more quickly and cheaply rebuild broken elevator ribbons.
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
Even before Heinlein and the golden age. Find a copy of the 1927 film metropolis. Written by Fritz Lang and Thea von Harbou, they've got computers, video phones, underground cities and flying cars even.
The Guardian says: "The biggest technical obstacle is finding a material strong but light enough to make the cable; this is where the carbon nanotubes come in." But what about selecting the appropriate carbon nanotubes among the 56 known varieties? Two teams of chemists from Rice University and the University of Illinois at Urbana-Champaign (UIUC) have found a way to separate and manipulate these varieties of carbon nanotubes. Obviously, it will help to build the Space Elevator. More details are available on my blog.
People seem to be genuinely worried about ~250t (the mass below GTO that can fall down) of pure carbon burning in the atmosphere into CO2. Rather ... funny ... considering the US enviromental policy during Bush administration (Kyoto, gas is not pollutant etc. etc.)
BTW wouldn't it be possible at least in theory to build similar elevator from earth to moon? The gravity center should be at the point where the gravity of each bodies cancel each other and the whole thing would rotate the same period as the moon. Moon would conveniently have the same side always towards earth so cable could be anchored there. Earth-end would have to be at altitude of LEO or higher due to delta-Vs.
Not sure if practical, would the earth-GTO and earth-moon elevators inevitably collide? Too high tension for even carbon nanotubes? Reaching the the earth-end would still require a booster but required deltaV is not very big, a supersonic jet would do if the end could be lowered to atmosphere. But the drag makes it impossible.
One more thing about the normal GTO elevator and possible threats (hurricane, terror etc). In pictures you see the cable anchored to oil rigs and such, giving the impression that there's a huge tension. In reality the original tension at ground level is nil, growing possibly to the same size as the maximum weight of climbers.
So imagine that you are the the ground (or sea) station, attach a climber to the cable that is exactly the same weight as cables tension to the station and then release the cable, what happens? Right, nothing. Now the climber is the counterweight needed to keep the cable at still. Make the climber to reel the cable in while it ascends and you have a neat way a avoid any threats at atmospheric levels. The climber might need some sort of balloons and controllable ballast in order to keep the cable's center of gravity not shifting from desirable point but that's all lowtech.
The original SF calls for an elevator - ie counterweights and elevator cages. All this is is a single line - stage 1 if you will. Initially we'll have to be shooting rocks up by rocket so we can bring them back down again as counterweight....
... and today's pet project has
Will this thing short the normal atmospheric electrical phenomena in the region? No lightnings!
I have a feeling it would be more than slightly annoying if you were one the people stuck 36K up in space with no way back down!
Assume that the Earth doesn't rotate at all, and you have a cable that is hanging from 36,000 miles, but not touching the ground.
Now, an object in higher orbit will orbit the planet more slowly than one in a lower orbit.
(For example, the space shuttle, in LEO, orbits about once every 90 minutes.)
What about an object in a severely elliptical orbit?
Its orbital period will be somewhere in between.
What causes an orbit?
The gravitational attraction of the planet pulls an object down.
The object is traveling forward.
The deflection of the forward velocity makes its path circular.
Take a rocket sitting in high Earth orbit.
Fire the rocket directly toward the Earth.
(This will be equivalent to the lower parts of the cable pulling on the upper parts.)
The rocket will travel toward the Earth, but it still has its forward velocity.
It will thus be deflected into a lower Earth orbit.
An object in a lower orbit travels faster than an object in a higher orbit, so the new (now elliptical) orbital period must be smaller (i.e., faster).
But, let's assume that this doesn't happen.
Let's assume that the cable falls straight down.
When it hits the lower atmosphere, it will start to flutter.
As it does this, it will be traveling at great velocity.
Friction with the lower atmosphere will heat it up, and it will burn up.
I guess the point is, now matter how it falls, most of the cable will be traveling at such a high velocity when it hits the atmosphere that it will burn up.
One final thing: Most pictures of the space elevator show the cable hanging straight down from its upper base.
I don't see how this is possible.
I think that the cable will hang down in an arc, and the base of the elevator will not be directly below its top.
But I don't know much about orbital mechanics, so I could be wrong.
Those who sacrifice security to condemn liberty deserve to repeat history or something. - Benjamin Santayana
Your claim completely shocked me, so I went to the site...
and was totally amazed. I had no idea the project was developed for that long. I also had no idea Gemini had become such a capable spacecraft.
What do you mean by Apollo not having "real pilot control?"
I noted, btw, that there was no mention of Gemini being a reusable craft. Any idea if a reusable capsule is a viable design?
+++ATH0
Yeah, bit like those poor souls on ISS, Mir et all that had no way back down as the elevator hasn't been built yet.
Oh wait. Ever heard of gravity? Just keep few "lifeboats" up there.
So is your english.
How we know is more important than what we know.
I'm sorry, what's the point of this again? Where are we going and what for? If we had some design for a super-lightspeed ship or had received a communication from an alien race, then I could see the point, but we dont. So why are we going back out there? Fusion fuel from the moon? We don't know how to build the reactors to use it (if we did, it might make sense to go mine some of it). Colonisation of mars? We don't know how to do that either, and even if we did, we've got enough people starving to death here on earth.
How we know is more important than what we know.
way before the operational stage, people would come from the corners of the globe just to get a look at a ribbon stretching up into space! you'd have to beat them back with a stick. expect ad-hoc floating cities surrounding the site, populated by geeks over here, pilgrims there, fanatics there, there, and there, tourists over that way, and terrorists, anyone?... the biggest problem after the engineering hurdles are gone will be security, not publicity.
"This is not a sig." -- R.
How is it stationary? The Earth's magnetosphere is asymmetric and Sun-oriented, so in fact an elevator couldn't possibly see an unvarying magnetic field as it orbits.
The real Captain Avatar is a fictional character, so I suppose he doesn't mind if I impersonate him.
You just know some prankster would keep hitting all the buttons before getting out at their stop!
Q: Why can't we just put a needle above the poles?
...
A: because objects directly above the poles don't orbit, they would just stay motionless above
the planet, so as soon as the thrust was removed to keep them there, they would just plummet
back to earth.
Q: Why do we have to have it around the equator?
A: because that is the only place you'll have a geostationary orbit. Place a satellite, say, 10-degrees north or south of the equator at a geo altitude and the satellite will oscillate
between +10 and -10 degrees of the equator.
Q: Why don't we build it on the moon first?
A: because the materials and expertise are here, and the whole point of the elevator is to slash the costs of getting materials off the surface of the earth in the first place. We need an efficient means of doing that first before we can think of building them on the other rocks in our system. The plus side is we don't have to waste so much space/weight on propellant to get a rocket up to speed to escape gravity and into orbital velocity. Instead, we would just climb up mechanically, which with photo-electric power, would use fewer resources than chemical propellant. Once up in geosynchronous orbit, the materials brought up can hang there near the elevator as more pieces are brought up, eventually assembling the pieces into a larget vehicle, better suited to long-range missions to say, mars and beyond.
Q: We couldn't use it for salvaging the space junk, they are just plain moving too fast.
A: yes and no... we would only really need small automated vehicles which could clamp onto the pieces of junk, and using maneuvering thrusters, adjust the orbits higher or lower, as well as trajectory, until they are at the level of the end of the elevator. Once at that point, the relative speeds aren't much different (although objects in a retrograde orbit might be a problem).
For that matter, vehicles assembled in space wouldn't need much more than thrusters, and perhaps a small engine for larger accellerations to get from place to place, since escaping earth's gravity isn't an issue anymore.
Q: What about 9/11 and terrorist attacks?
A: keep hiding under your bed you @#$&$#!@ coward.
Q: Wouldn't the pull of the ascending vehicle pull the counterweight down into a lower orbit, making the elevator useless?
A: It depends on how heavy the vehicle/payload is, as well as the counterweight. Only an idiot would try to ascend with more weight than the counterweight can handle (The Darwin Awards has a perfect example of this effect, about a guy working on his radio tower, sorry no URL handy). If there is more force on the counterweight trying to fling it away, than there is by the payload pulling it down, then the counterweight will stay in place...
which brings me to one point that I'm not so sure about...
It always seemed to me that you would need a very good/reliable anchoring point for something like this, and having a floating base in the water just doesn't seem to be it... get too much payload
too high on the cable, and it would add to the pull the counterweight is exerting, and you could very well yank the base out of the water and into space if the accident was catastrophic.
Suppose you have a payload that is pretty much right at the limit of what the counterweight can support. It approaches geo-point, but isn't braking fast enough, and passes geo-point. At that point, the forces switch from trying to pull the payload back down to the ground, to trying to push it further away. Eventually, it slams into the counterweight, which may or may not hold. Problem is, you now have (for an extreme example) twice as much weight on the end on the cable, exerting twice as much vertical force on the base. Add to that the inertia of the payload hitting the counterweight would "jerk" the cable upwards.
You would need a great deal of weight at the base for it to be a suitable anchor, yet you need the
base to float at the same
Cogito cogito, ergo cogito sum, cogito.
I do not claim that it is stationary wrt the earth's magnetosphere. I claim that it is stationary wrt the earth's surface (which it is), and that it is orthogonal to the earth's magnetic field at any height at which it could cause atmospheric disturbances (which it is)
These two criteria make it stationary wrt magnetic field lines, which is the important determination. Remember, magnetic field lines connect the earth's north and south poles (magnetic ones, not rotational ones)
While, as the earth rotates in the solar wind, these field lines compress and expand, no new field lines would sweep across a vertical. Remember, electricity is generated by a CHANGE in magnetic field. That wouldn't be happening here.
I am disrespectful to dirt! Can you see that I am serious?!
I was just curious about your statement that the space elevator was "invented" by Jurij Artsutanov...
t
My initial reaction was: "Waitaminute... it wasn't INVENTED; it was just THOUGHT UP/CONCEIVED by that guy. There is no physical structure and, therefore, no INVENTION."
But then I came across this:
http://www.hyperdictionary.com/dictionary/inven
Apparently in 1913, Webster said "invent" was "to contrive or produce for the first time", but today, WordNet said it is to "come up with (an idea, plan, explanation, theory, or priciple) after a mental effort".
I just thought it was interesting how the definition has changed over the years.
Karma: NaN
you ever see a yorkshire terrier spin around trying to catch its tail? put that little guy in space with a really long leash and he'll be able to maintain the needed tension on the elevator.
of course, if the leash gets caught up in his legs while something's getting transported, the whole thing's screwed.
The World's Worst Webcomic!
Last time I checked, the Earth has been rotating around the same axis since....the beginning of time?
Then we are long overdue for an axis tilt. There have been some geological discoveries that made some scientists question if there was a polar shift. I tried finding it on google but can't. It wasn't anything like the sahara once being fertile farmlands and a 1 degree change made it a desert. What I saw a few years ago talked about magnetic rock found where north didn't point to magnetic north, which made geologist think the earth did a 180. I wish I could find it.
'Same speed C but faster'
with a 1/10 g acceleration you will reach the top of the "elevator" in less than 6 hours
Another poster hypothesized that the "track mechanism will presumably be some sort of magnetic suspension," thus speeds must be kept down to 400 - 500 km/h, to prevent a catastrophic failure in case the vehicle brushes against the nanotube ribbon.
For all I know, the "track mechanism" may be even simpler than that -- such as opposing rubber wheels tightly gripping the ribbon. (I wish I could be at that conference to see what mechanisms are actually being proposed!) In which case speeds will also have to be kept pretty low in order to prevent damage to the ribbon.
That that is is that that that that is not is not.
What I've been wondering:
.5 KM/sec= 1800km/h
When you have a cable this long and you swoop it around to get it geo-stationary (and not let it tie up the Earth two-and-a-half times), doesn't Einstein kick in? The speed of the tip is far greater than the speed at the bottom, which -TMK- makes the end slow down in relative time, compared to the 'stationary' part that's located on Earth.
A small calculation:
-Earth is revolving at
-we ignore the speed of the Earth around the sun (and the speed of our Solar system, etc)
-(so) the center of the Earth doesn't move
Triangular geometry shows us that at a distance of 100,000km, we have a speed of 28350KM/h (roughly) for a geo-stationary tip-of-the-cord. That's a difference in speed of 26550 km/h between bottom and top. (Am I still correct?)
Now, it's not by far as fast as the speed of light, so time will not stand still when you reach the end. Still, I do wonder what happens to an object that is so big and has such a difference in speed at the opposing ends. Does time slow down -relatively- when you reach the end? If you stay at the end of the cord for a month, did you age less than you twin brother on Earth? If so, how much younger are you?
Ponderingly yours,
Eelko
you have to use the cable for propulsion, otherwise you have just invented a strange kind of tethered rocked and you are not saving any energy.
It's not "a strange kind of tethered rocked." Not by a longshot.
First of all, the elevator, unlike a rocket, need not carry any propellant. Right there you have reduced the size and complexity of the vehicle by 97%. Do a little research on the "rocket equation," and learn how the need to accelerate tons of propellant to hypersonic speeds leads to exponential increases in vehicle size, as well as the need for complex staging mechanisms.
It also need not carry its own energy source. Power will be beamed to the vehicle by laser or microwave.
A final way to realize the elevator's superiority to a rocket is to consider that 100% of the energy expended by the elevator serves to increase the elevator's potential energy in the earth's gravitational field. But not all of the energy expended by a rocket increases the rocket's potential energy -- especially when it has just left the pad and is traveling slowly. In the extreme case, consider how a rocket needs to expend enormous amounts of energy just to "hover" at a constant altitude. The elevator, on the other hand, can simply clamp on to the ribbon and hang there, expending zero energy to hover.
That that is is that that that that is not is not.
I would expect that once you get the cable past 36,000 km above the earth the cable would mostly pull itself up from that point on.
Your understanding is pretty close.
What will actually happen is that a big "spool" of ribbon will be launched into geosynch orbit. Shortly after you begin to deploy the ribbon out of the spool, the "gravity gradient" effect will create tension in the ribbon, and it will actually begin to pull itself out of the spool. To date, experimental space tethers have only been a few km long and generated a relatively modest tension. But a tether long enough to reach Earth's surface will generate high tension; the "spool" will have to contain a powerful brake to keep the ribbon from unreeling itself at out-of-control speeds.
Keep in mind that as the ribbon deploys in one direction, the spool will automagically move in the opposite direction, such that the system's center of mass remains in geosynch orbit. That's why the overall length of the ribbon must be longer than the altitude of geosynch orbit. (And that's a big bonus for launching an interplanetary vehicle; it can ride the elevator to a point well above geosynch orbit.)
That that is is that that that that is not is not.
If it's breaking due to terrorist attack (a la 9-11) , then I think the effects will be minimal, except that you're going to get a burning ribbon whipping through the atmosphere in circles.
You seem to be assuming the terrorism takes the form of idjit flying an airplane into the base of the skyhook; yes, this scenario causes a bit of local damage and a large spaghetti nuisance in orbit. However, trivial non-airplane sabotage scenarios (left as exercises for the student) can cause breaks higher up. A break at, say, 80% up the ground-to-geostationary distance results in a beanstalk trying to wrap itself from Quito to Gabon by way of Indonesia, and dumping a sizable chunk of (a) kinetic energy and (b) oxidized carbon into the atmosphere-- *IF* you're lucky. Buckytubes also show some thermal superconductor tendencies, depending on type. Dropping one kilo from geostationary yields about the same bang as half a stick of dynamite in pure kinetic energy; this doesn't factor in the kinetic energy of the flaming ribbon. How grams of carbon per meter ribbon length are we talking again?
In my more heartily American A--hole moods, I greatly regret that Mecca isn't 20 degrees further south; it would substantially reduce the risk of Islamic terrorist attacks on our hypothetical Indian Rope Trick.
//Information does not want to be free; it wants to breed.
OK, OK. So the cable snaps. Which way does it fall (east or west)? I predict that the land value close to the equator will fall drastically if there's any chance that a snapped cable could land in your backyard, so to speak.
The NSA: The only part of the US government that actually listens.
Why should it increase its angular velocity.
Constant linear velocity. Decreasing radius. Therefore increasing angu;lar velocity.
The equator is travelling at about 1000 mph (24000 miles circumferencce, one day to get back to the start point. Something on the end of a peice of stringis travelling faster, just to stay above the same point on the earth. As it falls, it doean't lose that speed, so it will get ahead of the original fastening point.
Consciousness is an illusion caused by an excess of self consciousness.
Its not the earth which flipped, it is the magnetic field. Every now and again, the eaths magnetic field drops to zero and re-emerges the other way up. Irrecularly, but about every 125000 years and taking about 5000 years to do it.
Continental drift might be more of a problem - in a hundred million years or so we might have to move it out of the way as Australia motors past. However, I think this one is far enoug off that we can leave it to the next generation
Consciousness is an illusion caused by an excess of self consciousness.
And the lowest note ever twanged.
Sorry, somebody got lower. Apparently there are a couple of galaxies way out there hooting at a frequency of one cycle every 10 million years and a wavelength of 30,000 light years. Now that is Bass.
Consciousness is an illusion caused by an excess of self consciousness.
Would a 10,000 km long razor thin cable, falling 9.8 m/s^2 for 10,000 km towards the earth do just a _bit_ of damage when it landed? How many safety precautions have been taken with this thing? Or would they just build the thing out in the middle of the ocean or something just in case?
I swear to god, if my eyes roll any harder, they're going to fall out of my head.
/.
Really, considering the near-symmetric encompassment of your sockets around your eyes, and the juicy friction-reducing fluid your eyes are lubricated with, I fail to see how any angular momentum of your eyeballs would result in translational motion away from your head.
Yes, this is exactly the type of reply I would expect here on
Keep it up guys!
The purpose of life is to find the purpose of life.
There is no such thing as centrifugal force.
There is centripetal force, which is the force of the string accelerating the rock towards the center, and there is the inertia of the rock resisting that force which is tangential to its orbit. Centrifugal force, which would be force directed from the center to the rock, pushing it outwards, is an illusion produced by your mind's incorrect interpretation of the rock's inertia.
Under capitalism man exploits man. Under communism it's the other way around.
You did not read the first half of the sentence you quoted. We are in fact in violent agreement.
Finally! A year of moderation! Ready for 2019?