Space Elevator Going Up 684
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."
what i really want to know is... (Score:5, Funny)
Re:what i really want to know is... (Score:5, Funny)
Seems like (Score:2, Insightful)
What what what (Score:4, Funny)
Uh oh...
Huh? Re:What what what (Score:2)
Re:Huh? Re:What what what (Score:3, Informative)
Oh hell, I will help you:
At about a third of the way along the cable - 36,000km from Earth - objects take a year to complete a full orbit.
You are right, "it takes one day to complete a full orbit at 36000km", BUT THAT IS NOT WHAT THEY SAID!
Error in article: (Score:5, Informative)
----
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.
------
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.
Re:Error in article: (Score:2)
Re:Error in article: (Score:5, Funny)
Indeed, the article should be talking about space elevators, not escalators.
Re:Error in article: (Score:2)
Yeah, that bit made me wonder, too. Glad I wasn't the only one to catch it.
Re:Error in article: (Score:4, Funny)
For more info on Space Elevators (Score:5, Informative)
Re:For more info on Space Elevators (Score:4, Informative)
Re:For more info on Space Elevators (Score:4, Informative)
Not an impossibility? (Score:5, Informative)
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.
Re:Not an impossibility? (Score:3, Interesting)
Any one know of any projects using an organic approach instead of a chemical approach (which is what I think is being used now?)
Re:Not an impossibility? (Score:3, Insightful)
Just because it's made of carbon doesn't make it easy to build. I don't know of any organism that makes diamond either (although if I did, I probably wouldn't tell anyone anyway :-) ).
Re:Not an impossibility? (Score:3, Informative)
Re:Not an impossibility? (Score:3, Informative)
If you read that article really carefully you'll note that they said it was stronger than steel, but tougher than any material. Steel isn't massively strong (Kevlar is stronger), however toughness is journalistic speak for 'how much energy can it absorb before it snaps'. That's cool, but for an elevator you need tensile strength, not energy absorption; you're not catching flies with it :-)
(And don't even think about catching space junk- it's going way to fast for that!)
Wow (Score:4, Funny)
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.
Re:Wow (Score:2)
Brings a whole new meaning to "satellite broadband", too.
"Where d'you want us to send the cable into your house?" "Oh, just drop it straight down through the chimney, same as everyone else."
Re:Wow (Score:2)
So far as I know the data connection technology for the car has not been speced yet, so I don't know how they intend to get Slashdot :-)
harnessing the public interest (Score:5, Interesting)
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.
Re:harnessing the public interest (Score:5, Informative)
Re:harnessing the public interest (Score:3, Interesting)
The ascent is going to be very very slow. Imagine going at 100km/h, a speed that would impress most normal elevator designers. 15 days for the ascent, 15 more for the descent. (Admittedly the descent could be done quicker).
It isn't going to be even close to 15 days to get to the top. Some very simple physics tells us that if we accelerated at 1 g for 1 second we would be traveling at a velocity of 9.8 meters per second (gravity on earth equals 9.8 m/s/s). If we then traveled at that constant speed we would reach the top of the cable in a little more than 11 days (do the math and see). Since we are operating under the influence of the earth's gravitational well we couldn't just accelerate for one second and then coast at constant velocity.
However, much more likely is that we will accelerate the "elevator" at 1/10 g to the halfway point and then decelerate it at 1/10 g to the top. And if we have two "elevators", one going up and one going down, it will be basically a system with little to no external energy requirement. Initially we have to invest the amount of energy required to lift one elevator and the other components needed for the station in orbit. Then we have to expend the energy to put the cable in place. Once that is done we start the top elevator down and voila we have the energy to start the bottom elevator accelerating up. There's a bunch of engineering involved to do this, but it's overall pretty basic physics.
If you do the math you will see that if we accelerate at 1/10 g to the halfway point, then decelerate at 1/10 g to the top, it will take a very short time to travel 100,000 km to the top of the elevator.
Let's round 9.8 m/s/s to 10 m/s/s to make our life easy. This isn't accurate, but it makes the equations much simpler. So, 1/10 g is 1 m/s/s. The formula for velocity while accelerating is:
.5 * 1 m/s * t^2
:-).
v=a*t where v=velocity, a=acceleration and t=time.
So, while accelerating at 1/10 g after 10 seconds we are traveling at a velocity of 10 meters per second, or 36 kilometers per hour, or 21.6 miles per hour. The next question is how far have we traveled? That formula is:
d=.5*a*t^2 where d=distance.
So at the end of those same 10 seconds we have traveled 50 meters. So, how do we figure out how long it takes to get to the halfway point? Simple substitution:
50,000 km =
Now solve like any other algebra equation. Remember to convert kilometers to meters.
t^2 = 50,000,000/.5*1
So t= 10,000 seconds, or roughly 2.8 hours traveling at a velociy of 10,000 meters per second (36,000 km/hr or 21600 mph). When we decelerate everything becomes negative and it takes the same amount of time to go from a velocity of 36,000 kph to 0 as it did to accelerate to that velocity. If you aren't sure just substitute a negative value for acceleration of -1 m/s/s and check me
Bottom line, with a 1/10 g acceleration you will reach the top of the "elevator" in less than 6 hours, assuming constant acceleration. In all likelihood we won't accelerate constantly because our vehicle would burn up in the atmosphere. Probably we will boost to a constant velocity, flip at the halfway point and decelerate when needed. Even doing that we will reach the top in less than a day.
And we will generate all the energy needed for acceleration and deceleration within the system. Pretty neat!
Re:harnessing the public interest (Score:4, Interesting)
Eek. We have enough trouble building a horizontal railway that travels faster than a few hundred kilometres per hour--now you want us to build a vertical one that reaches a speed thirty times greater? One little hiccup in your track mechanism (presumably some sort of magnetic suspension) and the moving cargo drags against the elevator cable at ten kilometres per second. Suddenly, you have a much shorter cable...
I'm prepared to accept a slow and stately climb at four or five hundred km/h, even if it means it will take ten days to ascend.
Re:harnessing the public interest (Score:3, Insightful)
Actually you do. It's the whole point of having the cable there at all. You need something to push off of. The only alternative is to throw stuff backwards really fast. The purpose of building a cable is to avoid that method.
Re:harnessing the public interest (Score:4, Informative)
The envisioned plan doesnn't have two "shafts". Nor do I believe such a arrangement would be possible.
Rather the designers have envisioned a laser based power transmission system. The moveable platform would likely contain a nuclear reactor to power a very powerful laser. The laser would be beamed to the climber which would contain a receiver that converted the intense laser light into elecotricity.
Of course adaptive optics used by the miliatary for exotic anti-missle systems would probably be necessary to hit the spot accurately on a rapidly ascending climber. Additionally, the ribbon cable would also likely be "flapping" in the air so a sophisticated tracking system would be necessary.
As you've pointed out, the descent stage needs no power. However, apparantly venting heat will be a problem at high speeds.
The material science will likely need a lot of work. However, I don't believe that the auto industry will invent the necessary processes. Rather, I believe that the defense industry will invent the processes to turn raw carbon into super-light, super-tough armor for aircraft, ships and tanks.
The last century was the century of steel. The next century will be the century of carbon. Remember the new diamond sythesis techniques that are currently practical. Expect a lot of work in these areas.
Re:harnessing the public interest (Score:3, Insightful)
This just means we have to reverse the viewing of the 'launch' to be from a camera mounted from the object. It'd be really neat to see the world as this climbs up above it.
As for tourists, I imagine this could put that miniscule 'Space Needle' to shame.
Re:harnessing the public interest (Score:3, Funny)
Yeah, but imagine the security screening they'll have to go through... Probably make an alien abduction feel like a casual glance....
What about the static electricity it will generate (Score:5, Interesting)
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??
Re:What about the static electricity it will gener (Score:5, Informative)
Re:What about the static electricity it will gener (Score:3, Funny)
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.
Re:What about the static electricity it will gener (Score:4, Informative)
They have had tecnical problems when they have tried it but they physics is all undergrad E&M.
Re:What about the static electricity it will gener (Score:4, Funny)
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.
7 billion USD? (Score:4, Insightful)
Fuck Iraq and let's cough up roughly 12 space elevators instead.
Re:7 billion USD? (Score:5, Funny)
Okay, done. What's the next step?
TWW
Re:7 billion USD? (Score:3, Insightful)
Insert lame joke here. (Score:3, Funny)
Correction (Score:5, Informative)
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.
Boring is ok with me (Score:5, Insightful)
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.
Re:Boring is ok with me (Score:4, Interesting)
Well, ya, but the purpose of the velocity to begin with is to get beyond the majority of gravity. 25k footpounds I believe. If you want to get a satalite to orbital velocity, it is much cheaper to do so once it is in orbit, free of 98% of the earth's gravity than it is to do this along the way.
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.
Also, for probes headed toward the moon/mars/space, orbital speed may not be a factor, except as needed to 'slingshot' the unit. IAMARS (i am not a rocket scientist) but it seems to me that you would have to save 70% of the energy needed by going to 36k km slowly, then positioning. The most important feature is that not only do you save the weight of the extra fuel, but you also the save the extra fuel needed to move that extra fuel. It may actually be more than 70% of the fuel.
Another interesting question: What fuel is used for getting the unit into space (36k km) to begin with: To power the elevator? Obviously it will not be rocket fuel. The cool thing is, if they used technology [scjai.com] that harnesses [pacpubserver.com] ocean waves [dailycal.org] then they would not need oil generation units
The secondary benefits of this space elevator could eventually be greater than just cheaper satalite launches.
Looks like the pointy haired boss at work again (Score:3, Interesting)
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?
Re:Looks like the pointy haired boss at work again (Score:5, Insightful)
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?
The same way that NASA came up with the budget for the space program in the early 50's and 60's. They had to create a huge number of things that did not exist in order to put a man on the moon. From things as mundane as food and drink and holders that could be used while weightless to as science fictiony as computers small enough to fit in an Apollo space craft. Somehow they managed to not only do all of that, but to budget for it as well. Not only that, all of that R&D was very good for the economy, returning, depending on who you believe, as much as $7 to the economy for every dollar spent.
Re:Looks like the pointy haired boss at work again (Score:5, Interesting)
Defending a one meter wide cable below 60,000 feet (Score:5, Interesting)
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?
Re:Defending a one meter wide cable below 60,000 f (Score:4, Insightful)
3 words: Restricted air space.
Re:Defending a one meter wide cable below 60,000 f (Score:3, Insightful)
Re:restricted airspace (Score:3, Insightful)
I would dare say it's built like a fort.
Re:Defending a one meter wide cable below 60,000 f (Score:5, Funny)
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.
Sources (Score:3, Informative)
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.
caution: atmospheric EMF (Score:4, Interesting)
Re:caution: atmospheric EMF (Score:4, Insightful)
Re:caution: atmospheric EMF (Score:5, Insightful)
Not unless you made it out of superconducters! Even the best conductor we know is going to have a significant amount of resistance along the kinds of lengths we're talking about.
And depending on the exact carbon nanotube technology they settle on, the elevator won't be all that conductive to start with... it could very well end up being less conductive than the air around it...
Clarke didn't invent this!!! (Score:5, Informative)
According to A. Clarke himself the space elevator was invented by Jurij Artsutanov from St. Petersburg.
(3001, The final Odyssey, under sources)
The thing that really sucks... (Score:5, Funny)
Going up... (Score:3, Funny)
"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..."
Re:Going up... (Score:3, Interesting)
I know you were just joking, but I found that number kind of put it all in perspective for a second.
How cheap is... (Score:5, Insightful)
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.
The conference site is (Score:5, Informative)
What I don't understand... (Score:4, Interesting)
Slashdot - Texas Scientists Spin Carbon Nanotube Fiber [slashdot.org]
Other promising research:
Slashdot - Scientists Crack Silk's Secret [slashdot.org]
and
Slashdot - Nanotube Applications Grow And Grow [slashdot.org]
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...
Elevator Music (Score:5, Funny)
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.
Access and Traffic (Score:3, Insightful)
I don't get it (Score:4, Interesting)
What about little space junk? (Score:4, Interesting)
Sorting Carbon Nanotubes Will Help the Space Eleva (Score:3, Informative)
Re:So what happens (Score:2, Funny)
And the lowest note ever twanged.
Re:Kind of scary. (Score:5, Insightful)
Re:Kind of scary. (Score:5, Funny)
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.
Re:Kind of scary. (Score:5, Insightful)
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.
Re:Kind of scary. (Score:3, Funny)
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. [thedailyjournal.com]
Re:Kind of scary. (Score:4, Funny)
When a cable under stress breaks it can cut right thought metal...
When this long whip breaks, it will slice right thought the earth!!
Re:Kind of scary. (Score:5, Insightful)
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...
Re:Kind of scary. (Score:5, Funny)
Re:Kind of scary. (Score:5, Informative)
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.
Re:Kind of scary. (Score:3, Funny)
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.
Re:Kind of scary. (Score:5, Informative)
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.
Re:Kind of scary. (Score:5, Insightful)
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.
Re:Kind of (not so) scary. (Score:2)
Re:Kind of scary. (Score:2, Insightful)
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 [nasa.gov] Earth [nearearthobjects.co.uk] Objects [harvard.edu]. Of course those things fall from roughly 4.7E17 km. Why the hell don't people imagine that?
Re:Kind of scary. (Score:4, Informative)
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...
Re:Kind of scary. (Score:3, Informative)
Re:Kind of scary. (Score:3, Informative)
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.)
Re:Kind of scary. (Score:2, Funny)
Re:Kind of scary. (Score:3, Informative)
Would you please document yourself, make the appropriate research [www.isr.us], 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
Re:Kind of scary. (Score:3, Insightful)
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.
Re:this would be sweet (Score:3, Interesting)
Re:this would be sweet (Score:2)
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.
Re:this would be sweet (Score:3, Informative)
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.
Re:hmm (Score:2)
Re:Idealism... (Score:5, Insightful)
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.
Re:Waterbeds! (Score:3, Informative)
And waldoes (Score:3, Informative)
Re:Idealism... (Score:5, Insightful)
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.
Re:Um...... (Score:2)
Re:Um...... (Score:2)
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.
Re:Um...... (Score:5, Informative)
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
Re:what about Newton's third? (Score:4, Interesting)
The question I want to know is what are the osilation modes going to look like. You have a massive string under tention, it is going to vibrate. I'm sure you could figure it out if you had some clue as to the properties of the material.
Re:1st lift (Score:5, Insightful)
Re:1st lift (Score:5, Funny)