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Space Elevators Face Wobble Problem

ScuttleMonkey posted more than 6 years ago | from the all-part-of-the-ride dept.

Space 244

NewScientist is reporting that while the strength of the tether has long been considered the main problem in building a space elevator, a new study suggests that a dangerous wobbling problem may also be a serious obstacle. "Previous studies have noted that gravitational tugs from the Moon and Sun, as well as pressure from gusts of solar wind, would shake the tether. That could potentially make it veer into space traffic, including satellites and bits of space debris. A collision could cut the tether and wreck the space elevator."

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A collision could cut the tether... (5, Funny)

kcbanner (929309) | more than 6 years ago | (#22898786)

A collision could cut the tether and wreck the space elevator.
Not to mention hurling whomever/whatever is the payload into space with the force of the largest man-made slingshot.

Re:A collision could cut the tether... (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22898890)

Hey peeps, Has anybody tried installing Solaris on a MacTV for use as a RAIDZ NAS device? Wondering if it would work or not.

Re:A collision could cut the tether... (0)

Anonymous Coward | more than 6 years ago | (#22898944)

The fun part is that it depends on where the break happens. One could get a cable whipping through the atmosphere of the earth, for example. Or, the payload could come back to earth. Thankfully, most theoretical designs have placed the station along the equator on an island, so that we can minimize such messy events.

With your scenario, it would definitely be youtube quality footage if we could record the space lift payload colliding with one of our astrological neighbors!

Re:A collision could cut the tether... (4, Interesting)

zippthorne (748122) | more than 6 years ago | (#22899568)

No, most designs specify a thin ribbon. So, no matter where it breaks, it won't impact the ground at more than terminal velocity for thin, burnt sheets.

The design that specified steel cable did so specifically to show how impractical it would be to attempt a cable using existing materials.

Re:A collision could cut the tether... (1)

TheWanderingHermit (513872) | more than 6 years ago | (#22899200)

Not to mention hurling whomever/whatever is the payload into space with the force of the largest man-made slingshot.

Sounds like something I remember seeing as a kid. So the passengers either end up on a planet very much like Earth, but where they're tiny and everyone else is a giant, or they end up lost on an alien planet with a mechanical sounding robot and stow-away agent who's scared of everything (including work).

Then why not a space escalator? (4, Funny)

CaptainPatent (1087643) | more than 6 years ago | (#22898788)

Because escalators don't break... they just become stairs.

Re:Then why not a space escalator? (5, Funny)

eln (21727) | more than 6 years ago | (#22898922)

A broken space escalator would become a stairway to heaven, and if Led Zeppelin has taught us anything, it's that a Stairway to Heaven doesn't make any damn sense at all unless you're already so high you're practically in space already.

Re:Then why not a space escalator? (3, Funny)

Chris Burke (6130) | more than 6 years ago | (#22899136)

if Led Zeppelin has taught us anything, it's that a Stairway to Heaven doesn't make any damn sense at all unless you're already so high you're practically in space already.

Well it makes perfect sense to me!

Re:Then why not a space escalator? (1)

Ethanol-fueled (1125189) | more than 6 years ago | (#22899426)

Any articles about space elevators should be part of the "Sci-Fi" or "humor" section. Space elevators make as much sense as trans-continental conveyor belts.

Re:Then why not a space escalator? (3, Funny)

mweather (1089505) | more than 6 years ago | (#22899444)

Or a tunnel from England to France.

Re:Then why not a space escalator? (0, Troll)

Ethanol-fueled (1125189) | more than 6 years ago | (#22899792)

I can swim from England to France.

Why don't you propose building a gondola lift [wikipedia.org] between the US and England? The rest of us, who live in the real word, will fly there. Rocketships and space-planes aren't the most effecient forms of space travel but, come on...a fucking space elevator? Sheesh.

Re:Then why not a space escalator? (4, Funny)

operagost (62405) | more than 6 years ago | (#22899432)

No Stairway? DENIED!

Re:Then why not a space escalator? (1)

JrOldPhart (1063610) | more than 6 years ago | (#22899580)

The RIAA will demand payment.

Re:Then why not a space escalator? (2, Funny)

Tribbin (565963) | more than 6 years ago | (#22898946)

Elevators don't break; they just become spaceships.

Re:Then why not a space escalator? (1)

Kynmore (861364) | more than 6 years ago | (#22898954)

RIP Mitch Hedberg. His comedy wasn't the most unique, but it was damned funny shit.

Re:Then why not a space escalator? (1)

drquoz (1199407) | more than 6 years ago | (#22898980)

Speaking of space stairs, what would happen to this elevator in case of a fire?

Re:Then why not a space escalator? (1)

call-me-kenneth (1249496) | more than 6 years ago | (#22899192)

what would happen to this elevator in case of a fire?
Naturally, the incredibly strong and light Notinventedyettium with which it will be built will also be highly fire resistant.

Re:Then why not a space escalator? (1)

gwait (179005) | more than 6 years ago | (#22899822)

And able to withstand direct lightning hits!

Re:Then why not a space escalator? (0)

Anonymous Coward | more than 6 years ago | (#22899314)

In space, no one can hear you burn.

Re:Then why not a space escalator? (2, Interesting)

TheWanderingHermit (513872) | more than 6 years ago | (#22899250)

Sounds like this is a job for the Tower of Kalidasa [wikipedia.org] .

dysfunction (0)

Anonymous Coward | more than 6 years ago | (#22900082)

Solar wind around Uranus, shaking and tugging your tether, both could cause dysfunction when getting your elevator up.

So it would be just like (0)

Anonymous Coward | more than 6 years ago | (#22898804)

riding the rickety elevators at my alma mater!

First Post (-1, Offtopic)

ZlatanZ++ (978060) | more than 6 years ago | (#22898808)

First one, and it was rubbush!

Re:First Post (1)

Tribbin (565963) | more than 6 years ago | (#22898850)

The space-time continuum has not been kind to you.

Re:First Post (0)

Anonymous Coward | more than 6 years ago | (#22898862)

First one, and it was rubbush!
You've got fail.

Just let it wobble! (1)

Tribbin (565963) | more than 6 years ago | (#22898812)

You'll end up somewhere very improbable.

Re:Just let it wobble! (0)

Anonymous Coward | more than 6 years ago | (#22898956)

So... it sounds safer to just use a worm-hole.

Re:Just let it wobble! (2, Funny)

cloakable (885764) | more than 6 years ago | (#22899614)

No, in that case you'll end up in Hell, or Earth will be invaded, with a silent scientist armed with a crowbar as our only hope.

This is awesome (2, Funny)

Apoorv Khatreja (1263418) | more than 6 years ago | (#22898830)

Why would somebody want to prevent that? Free fall would be the most amazing part of the ride.

Re:This is awesome (2, Funny)

Pojut (1027544) | more than 6 years ago | (#22899222)

Once, when I was about 8 years old, I asked my step-dad if jumping off a cliff hurts. His answer?

"It's not the jumping part that hurts...it's the sudden stop at the end."

In good company (2, Interesting)

xPsi (851544) | more than 6 years ago | (#22898848)

Funny that. Another piece of science fiction engineering, Ringworld, is unstable too [wikipedia.org] . Nevertheless, I still think the space elevator is a ponder-worthy pipe dream.

When will it become a reality? (5, Interesting)

genesus (1049556) | more than 6 years ago | (#22898860)

During a speech he once gave, someone in the audience asked Arthur C. Clarke when the space elevator would become a reality.

"Clarke answered, 'Probably about 50 years after everybody quits laughing,'" related Pearson. "He's got a point. Once you stop dismissing something as unattainable, then you start working on its development. This is exciting!"

http://science.nasa.gov/headlines/y2000/ast07sep_1.htm [nasa.gov]

It's easier to postulate than actually engineer (3, Insightful)

EmbeddedJanitor (597831) | more than 6 years ago | (#22899366)

"I predict flying cars by year 2000^h^h^h^h2010^h^h^h^h2020". Prediction is the easy bit. Actually engineering a flying car or space elevator or whatever is the hard bit. There are a lot of very significant obstacles to overcome.

The old well worn bridge analogy: In theory it's pretty easy to built a bridge, but you need to only look at the Tacoma Narrows bridge to see that engineering a viable structure takes a bit more than str theory is prettSame deal with a space elevator. The theory is pretty straightforward, but the actual engineering to make a reliable structure is something else.

Re:When will it become a reality? (1)

StikyPad (445176) | more than 6 years ago | (#22899648)

Holy space bees, the space elevator is heading straight for our space truck! If we don't get some space between it and us, we're gonna be turned into space bloats! Man, it's space times like this I wish I'd sprung for those space engines instead of relying on space-slings. Buckle your space belts!

Of course it's going to wobble! (2, Interesting)

The Ancients (626689) | more than 6 years ago | (#22898868)

any who has ever seen cartoons as a kid would know this :p

News flash! (1)

LWATCDR (28044) | more than 6 years ago | (#22898880)

Space Elevators are not simple to build!
I never saw that one coming!

I am more concerned about the static problem (3, Interesting)

Black Art (3335) | more than 6 years ago | (#22898886)

I would be more concerned about the space elevator becoming a giant van degraff generator. Something that long would present some very interesting problems. Huge frikin lightning rod might be a better description.

Re:I am more concerned about the static problem (1)

call-me-kenneth (1249496) | more than 6 years ago | (#22899002)

That is but one of a large number of failure modes that have the potential to be terribly entertaining to watch on TV (until the part where the flesh boils off your bones as the atmosphere is superheated by billions of tons of nanotubes failing to burn up and merely getting very very hot as it re-enters the atmosphere, anyway.)

Re:I am more concerned about the static problem (2, Interesting)

Naughty Bob (1004174) | more than 6 years ago | (#22899038)

It would be cool if we could harvest that built up charge to help run the damn thing.

Re:I am more concerned about the static problem (1, Flamebait)

geekoid (135745) | more than 6 years ago | (#22899268)

Lighting rods repel lighting, not draw it.

Re:I am more concerned about the static problem (1)

Changa_MC (827317) | more than 6 years ago | (#22899436)

Lighting rods repel lighting, not draw it.
Nope, sorry. Lightning Rods [wikipedia.org] attract electrical current, thereby drawing it away from other structures that would be damaged by it.

This is why wooden lightning rods are a bad idea, kids.

Re:I am more concerned about the static problem (4, Informative)

JesseMcDonald (536341) | more than 6 years ago | (#22899550)

Lighting rods repel lighting, not draw it.

Nope, sorry. Lightning Rods attract electrical current, thereby drawing it away from other structures that would be damaged by it.

They do both. As the storm builds up the lightning rods help to diffuse the charge. This is one reason why they have sharp ends; electrons leave a charged conductor more readily at points of higher curvature. The pathway thus created then becomes the preferred (low-resistance) route to ground in the event of an actual lightning strike.

Re:I am more concerned about the static problem (1)

Wavebreak (1256876) | more than 6 years ago | (#22899442)

This place needs a -1: Wrong.

Re:I am more concerned about the static problem (3, Funny)

ma1wrbu5tr (1066262) | more than 6 years ago | (#22899964)

Did ya go to one of those "intelligent design" science classes?

The also face "really dumb idea" problem (0)

Anonymous Coward | more than 6 years ago | (#22898900)

n/t

The Great Glass Elevator (1)

ninjapiratemonkey (968710) | more than 6 years ago | (#22898920)

seemed to work fine for getting Charlie and Wonka into space. although it wasn't supposed to do that...

Re:The Great Glass Elevator (1)

PotatoFarmer (1250696) | more than 6 years ago | (#22899864)

Very true. Clearly, the same solution applies here - simply tether the space elevator to skyhooks and quickly change the subject if anyone asks what the other end is connected to.

weebles (1, Funny)

Anonymous Coward | more than 6 years ago | (#22898932)

Make the elevator teether out of weebles.

Next.

Re:weebles (2, Funny)

call-me-kenneth (1249496) | more than 6 years ago | (#22899122)

Thanks... I've always wanted to know if I could spray dry-roasted peanuts out of my nose the way some people do coffee.

Re:weebles (1)

Tobenisstinky (853306) | more than 6 years ago | (#22900068)

Mod UP! funny as hell! PS do they still make weebles?

Of course it's not easy (5, Insightful)

TheCoders (955280) | more than 6 years ago | (#22898948)

I don't think anybody really thought building a space elevator would be as simple as reeling out some cable and strapping on a cabin. There are a million complications, even before we get to solar winds or tidal pulls. How about something as simple as airplane traffic? Birds? Squirrels, for goodness sake!?

Plus a million things we haven't thought of, and won't think of until the product is built. When train tracks were first laid down, they were too close together, because nobody had heard of the Bernoulli effect. Trains were getting slammed against each-other by their own created air pressure. What did people do? They learned from it, and moved the tracks further apart. We take trains for granted, but they were not without their technological hurdles to overcome.

Of course something like a space elevator is not an easy accomplishment. Does that mean we shouldn't try?

What do you think?

Re:Of course it's not easy (4, Insightful)

Gat0r30y (957941) | more than 6 years ago | (#22899180)

Of course something like a space elevator is not an easy accomplishment. Does that mean we shouldn't try?
I think we should and probably will at least give it a shot. Also, as you note, there are a LOT of complications. Complications I look forward to seeing innovative and cool solutions to. First and foremost though, we gotta get the material engineering issue solved, until we have a material which can withstand the forces involved, were stuck with regular elevators. Nanotubes look promising, and this gives us an excuse to invest in the research.

Re:Of course it's not easy (0)

Anonymous Coward | more than 6 years ago | (#22899858)

>I don't think anybody really thought building a space elevator would be as simple as reeling out some
> cable and strapping on a cabin.

          Unfortunately, there are people out there who do think that.

Shurely shome mishtake!! (2, Funny)

call-me-kenneth (1249496) | more than 6 years ago | (#22898958)

You really mean to tell me this batshit crazy idea that requires massive advances in materials science even to become technically feasible might just possibly not be entirely practical?? Say it ain't so.

Re:Shurely shome mishtake!! (1)

TripMaster Monkey (862126) | more than 6 years ago | (#22899188)

Yup...just like powered flight and space travel...pipe dreams all, right?

Re:Shurely shome mishtake!! (1)

call-me-kenneth (1249496) | more than 6 years ago | (#22899412)

Well, space travel, sure, that's absolutely a pipe dream. Oh wait, you're talking about the sort of thing where a huge industrial nation spends 5% of it's GDP for a decade in order to prove a point to a geopolitical rival, rather than actual practical spaceflight? Well, whatever, let's not go there.

Anyway as Professor Sagan famously remarked, they laughed at Bozo the Clown, too. When someone's built a functioning prototype...

Y'know, the 60s "Way We'll Live Tomorrow" book I had as a kid said we'd be living in huge colonies on the bottom of the ocean in the 21st century. When there are cities in the Gobi Desert, which is far more accessible and rich in valuable resources than anything out of LEO[1], I'll start taking space elevators seriously.

([1] excluding the simple coolness factor of pure research into planetary science, performed with robotic vehicles of course. I'm a total obsessive over such stuff for 25 years, anyway. Are you following Cassini, Messenger, the MERs, Phoenix, etc? Really incredible stuff that can be done today for what amounts to chump change from the national budget. Dream all the dreams you want, of course, just don't bore the rest of us with them the next day, you know? ;)

Weight Loss (1)

AioKits (1235070) | more than 6 years ago | (#22898964)

I lost 50 pounds due to the wobble!

Thanks space elevator!

Re:Weight Loss (1)

WarJolt (990309) | more than 6 years ago | (#22899108)

A little lighter and a little flatter due to the forces made by the largest slingshot on this planet or near this planet for that matter.

Multiple tether points in space? (1)

Naughty Bob (1004174) | more than 6 years ago | (#22898990)

IANASEE (...Space Elevator Engineer). But it would seem that the solution to this particular issue would be multiple end-points in space. It would dampen the wobble, and also provide a degree of redundancy...

Re:Multiple tether points in space? (1)

call-me-kenneth (1249496) | more than 6 years ago | (#22899152)

IANASEE (...Space Elevator Engineer).
Neither is anyone else, grasshopper.

Re:Multiple tether points in space? (1)

Naughty Bob (1004174) | more than 6 years ago | (#22899230)

We are all in the gutter, but some of us are looking at the stars.

Re:Multiple tether points in space? (1)

geekoid (135745) | more than 6 years ago | (#22899302)

Yes, but a space elevator is fiction. The technology to make it is fiction, and it poses a high risk even when it become feasible.

Look at the stars, but not so hard your brain falls out.

Re:Multiple tether points in space? (1)

call-me-kenneth (1249496) | more than 6 years ago | (#22899494)

s/when/if ever/, otherwise I totally agree. Nothing wrong with looking at the stars, especially if you're lucky enough to have dark skies - I myself harbour long-cherished dreams of getting myself a nice Meade LX200 16" Schmidt-Cassegrain when I win the lottery as it goes - but I just wish more people would keep in mind the boundary between science fiction and something that is technically feasible and might one day be attempted, like say a tunnel from Alaska to Sibera, a mile high building, robots generating enough power for a lightbulb for eight hours to last four years on the surface of Mars, whilst having their entire OS and application stack upgraded remotely multiple times for less than a hundredth of the salary of the best-paid US CEO, terabyte USB sticks,.. - you know, the sort of thing that genuinely inspires. As opposed to a cool 40 minutes of TV once or twice a week, which is great and all, but... it's just TV.

Re:Multiple tether points in space? (1)

Naughty Bob (1004174) | more than 6 years ago | (#22899562)

Yes, but a space elevator is fiction.
Well, I was kinda acknowledging that in my original post-

...it would seem that the solution to this particular issue...
But don't you think that by exploring wacky ideas, we might come up with something cool, or that is usable in some other context? A boy can dream, after all.

"I think" Engineering (5, Insightful)

iamlucky13 (795185) | more than 6 years ago | (#22898998)

.But Perek says that may not be enough. "Previous proposals for a passive tether controlled from the ground do not seem stable to me," he told New Scientist. Anders Jorgensen of the New Mexico Institute of Mining and Technology in Socorro, US, who has previously studied the problem, agrees that stability is a concern for space elevators. But he says the new paper does not provide a quantitative analysis of the issue, and is not convinced that thrusters would be needed to stabilize the cables.

Basically, the problem has been noted before this Perek guy's paper, but not studied in any detail. Perek reiterates and perhaps expands upon the concern, but doesn't do any analysis to establish the actual likelihood of a problem. It's basically an opinion.

Atmospheric oscillations should be extremely well damped by drag. Oscillations due to gravity from the sun and moon may be a greater concern, because there is no drag, although including conductive paths in the cable may allow the earth's magnetic field to suitably damp the oscillations.

An IEEE article on the topic discussed the related issue of harmonics. If these oscillations propogate through the cable at a rate that syncs up well with the rotation of the earth, gravity of either the moon or sun may amplify them. The tensile component can be tuned by adjusted the mass and tensile stiffness of the cable, and even better, the mass of the counterweight, allowing you to tune it by changing the tension, like an incredibly huge guitar string. The will also be a pendulum like motion due to the fact that the earth is on a tilted axis. This seems to be the concern discussed in the article.

I personally am not at all convinced that oscillation of the cable alone (waves) is a problem due to it's low density, but oscillation of the combined cable and counterweight (pendulum) may be. If so, thrusters on the counterweight are much simpler to attach and refuel than they would be at intermediate altitudes on the cable.

Re:"I think" Engineering (0)

Anonymous Coward | more than 6 years ago | (#22899406)

The best is the last line of the abstract: "Extensive numerical simulations will have to be performed in order to determine elements of the thrusters and their control system." So the article is what, a statement that he's found an interesting problem to work on?

Anyone have access to the article to verify it's freedom from facts (FFFtm)?

You think too (0)

Anonymous Coward | more than 6 years ago | (#22899540)

Perek reiterates and perhaps expands upon the concern, but doesn't do any analysis to establish the actual likelihood of a problem. It's basically an opinion.
..

Atmospheric oscillations should be extremely well damped by drag. .. I personally am not at all convinced that oscillation of the cable alone (waves) is a problem

Opinions on both sides, it seems. I guess we'll have to build one and see what happens.

Re:You think too (0)

Anonymous Coward | more than 6 years ago | (#22899758)

Hehe...good catch. Basically what I'm saying though, is that the paper says nothing substantial about the feasibility of a space elevator. Neither do mine, but I'm not writing a paper or news article about it.

If we really want to have a meaningful discussion, however, we'd get into the material and power transmission problems, which are definitively quantified as real.

wreck the elevator (4, Insightful)

alta (1263) | more than 6 years ago | (#22899032)

Looking at the sheer size of this, I'd say that 'wreck the elevator' is a major understatement. Look at all the other stuff that would be wrecked. I remember reading a Ben Bova book a while back where terrorists sabotaged an elevator. They went to the top and severed the connection to the counterweight. The rest of the thing toppled like a flimsy tree, wrapping itself 1/2 way around the earth. Yeah, scifi, but it could happen.

Re:wreck the elevator (1)

argent (18001) | more than 6 years ago | (#22899198)

They went to the top and severed the connection to the counterweight. The rest of the thing toppled like a flimsy tree, wrapping itself 1/2 way around the earth.

It was even more spectacular when Kim Stanley Robinson did it to Mars.

Re:wreck the elevator (1)

ArsonSmith (13997) | more than 6 years ago | (#22899204)

actually no, Just like how the WTC Towers didn't fall over they collapsed on them selves. The cable would just turn into a giant mount of cable, probably at the bottom of the sea.

Re:wreck the elevator (5, Interesting)

alta (1263) | more than 6 years ago | (#22899308)

Actually, no. The rotation of the earth would cause the ribbon to wrap around the earth in an easterly direction. To refute myself as well: http://en.wikipedia.org/wiki/Space_elevator#In_the_event_of_failure [wikipedia.org] says that most of it would burn up on re-entry and that which doesn't will have less force than a piece of paper. So, please disregard my statements, but it sounded impressive the first time I said it ;)

Re:wreck the elevator (1)

Otter (3800) | more than 6 years ago | (#22899416)

Wouldn't you get a whip-cracking effect at the end of the tether? And it seems like the "would burn up" and the "terminal velocity would be really slow" contradict.

Re:wreck the elevator (1)

wattrlz (1162603) | more than 6 years ago | (#22899428)

Yeah, but think of what all that CO2 would do to the global climate.

Re:wreck the elevator (1)

bill_mcgonigle (4333) | more than 6 years ago | (#22899532)

So, please disregard my statements, but it sounded impressive the first time I said it ;)

Hey, somebody has to play this role every time a space elevator article gets posted, and they get modded all the way up.

We typically point them to Wikipedia and write them off as 'the new guy'. Hey, wait a second!

Re:wreck the elevator (2, Funny)

VoltCurve (1248644) | more than 6 years ago | (#22899548)

Do not worry. I have modified the wiki entry to fit better with your version of reality. You are welcome.

Re:wreck the elevator (4, Insightful)

merreborn (853723) | more than 6 years ago | (#22899726)

Actually, no. The rotation of the earth would cause the ribbon to wrap around the earth in an easterly direction
If what you propose were true, a pin balanced on its end would always fall over to the east as well, as would a perfectly symmetrical tree, or a falling skyscraper.

They don't, because all these things, a space elevator included, travel through space at the same speed as the earth's rotation. Why would it suddenly, magically lose that momentum, were it severed from its counterweight?

Re:wreck the elevator (0)

Anonymous Coward | more than 6 years ago | (#22899978)

No, it couldn't. Most of the cable would lie above the atmosphere, and if pulled down, would gain enough velocity due to gravity to burn up in orbit. The bottom 1% of the cable actually inside the atmosphere would fall with the terminal velocity of a sheet of paper.

And you thought it was bad (3, Funny)

Lucas123 (935744) | more than 6 years ago | (#22899046)

getting stuck in an elevator in a NYC skyscraper, imagine a brownout halfway between here and the moon.

Little equipment problem (1)

No2Gates (239823) | more than 6 years ago | (#22899070)

Yeah, something like that could ruin your day.

"Honey, yeah, I'm going to be home later than I thought. Don't wait up for me, little elevator problem"

Easy to fix (1)

Kim0 (106623) | more than 6 years ago | (#22899076)

Just absorb wobbles when they reach the ground station, by moving it.
The elevator string behaves like a one dimensional wave, and they can be completely absorbed at a point.
It could also be steered by that point, the ground station.

Kim0

space elevators will not co-exist with satellites (1)

secPM_MS (1081961) | more than 6 years ago | (#22899264)

From the reference point of the earth, a space elevator will stay above its base on earth, co-rotating with it and vibrating somewhat(we hope). The problem is that satellites orbit the earth and gradually sweep across all earth spots allowed by their inclination (in general). Thus, given long enough, satellites (other than geo-sync ones) may cross the elevator.

A practical elevator is going to need a lot of armor to protect it from debris for a considerable portion of the low earth orbital space.

Yet another possible solution. (1)

wattrlz (1162603) | more than 6 years ago | (#22899272)

Couldn't we just hook up adjustable tuned mass dampers every few hundred meters? It works for cars and skyscrapers.

Re: Yet another possible solution. (1)

Kohath (38547) | more than 6 years ago | (#22899326)

Too heavy.

Re: Yet another possible solution. (1)

FridayBob (619244) | more than 6 years ago | (#22899654)

Nope. That would weigh it down too much. The whole concept is only possible because, even if it's many thousands of kilometers long, a carbon-nanotube tether is still strong enough to support its own weight. Sure, it will be possible for it to support a few such counterweights if necessary -- a few more as extra tethers are added for strength -- but never as many as you suggest.

Re: Yet another possible solution. (1)

Omnius (1242594) | more than 6 years ago | (#22899674)

Couldn't we just hook up adjustable tuned mass dampers every few hundred meters? It works for cars and skyscrapers.
It seems to me that the cars (or whatever they end up being called) that travel the ribbon would have to have some sort of damper on them or any oscillation in the cable would make the occupants quite ill (even if the oscillation wasn't damaging the cable). Maybe that would be enough to dampen the cable itself.

I could easily see an oscillation in the cable that was essentially nil to the cable (meaning the oscillations cancel out when measured for the length of the cable) but are quite significant to the ants crawling up the cable.

Space Janitors (0)

Anonymous Coward | more than 6 years ago | (#22899310)

Looks like we just created a new job - cleaning up the crap and satallites orbiting in the right-of-way that the cable will require. Who's gonna hold the Hefty while I sweep this up?

What about the alternatives? (1)

Wavebreak (1256876) | more than 6 years ago | (#22899320)

I realize that the space elevator has a coolness factor, on a scale of 1-10, of about 14, but still, why is it all we ever hear about? There are other designs for low-cost orbital launch systems that would likely to be a lot more feasible in practice. Namely, http://en.wikipedia.org/wiki/Launch_loop [wikipedia.org] , http://en.wikipedia.org/wiki/Space_fountain [wikipedia.org] or http://en.wikipedia.org/wiki/Orbital_ring [wikipedia.org] , altho the orbital ring variant would be a larger construction, but should pose fewer engineering issues.

Who needs CNTs? (1)

sqrt(2) (786011) | more than 6 years ago | (#22899334)

Just make it out of Scrith, that should be strong enough to withstand debris impacts.

Re:Who needs CNTs? (1)

JrOldPhart (1063610) | more than 6 years ago | (#22899886)

A hole in the scrith is what generated the eye storm.
Then there was the mountain with the hole in it which was from an opposite direction hit.

Energy & momentum conservation (1)

redelm (54142) | more than 6 years ago | (#22899440)

Conservation of energy and momentum would require the orbital "head-end" to slow down as a elevator ascends. This is easy to see with a self-propelled payload.

What is less clear is how eneregy and momentum would be recovered on a payload descent. Perhaps balanced by an ascending load on pulleys.

Re:Energy & momentum conservation (1)

JrOldPhart (1063610) | more than 6 years ago | (#22900024)

Slower = down faster = up, so, top moves down on ascent and moves back up on decent.
I'm getting a headache.

Kids pressing all the buttons... (5, Funny)

MrSteveSD (801820) | more than 6 years ago | (#22899454)

is surely the biggest problem :)

The wobble would be small or low in frequrency (1)

billsf (34378) | more than 6 years ago | (#22899460)

The resonate frequency of the 'wobble' would be extremely low. Therefore, it would be possibly be imperceptible without the use of instrumentation. However, over time this resonance may build up over time, requiring an extremely small amount of thrust to correct. The (cycle) period would be in days and depending on design, harmonic and overtone activity would be lower than the fundamental by a considerable amount, at least six dB an octave. (Which would be very serious if only odd harmonics were produced.;) Clearly this has been simulated (and its quite easy) on a computer before?

Personally, while I respect the editorial staff of New Scientist greatly, people do make mistakes and since NS allows some types of advertising, a little bit of sensationalism can have its leeway. Somehow it might be tied to a very low tech product that is all over the pages of NS: The automobile.

       

Firs7 Post (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22899512)

this po5t up. [goat.cx]

What "the Doctor" had to say about it. (2, Funny)

jameskojiro (705701) | more than 6 years ago | (#22899564)

"Yo, I was like going up in da space elevator with my hommies and E-lek-tronic Dawg when the whole thing started goin' all Wibbly Wobbly like. I pulled out my Sa-honic Screwdriv'ah an dun popped a sonic cap it the monofiliment resonator. After that is was all like that bitch Sarah Jane, smooth as her backside was 30 years ago when she was still hawt, ya' know what I mean G? "

Because rocket flights are cheaper? (1)

LuminaireX (949185) | more than 6 years ago | (#22899626)

I'm no rocket scientist, but the article cites a concern that this wobbling cause space elevators to become more expensive and difficult to build. OK, I'll give you that adding a thruster system will increase the cost of your project, as feature creep often does, but wouldn't the cost of doing so be vastly exceeded by the very rocket launches that this elevator intends to replace? Wouldn't the costs of added complexity and materials be vastly exceeded by the cost of repeated rocket launches?

God almighty! (1)

exp(pi*sqrt(163)) (613870) | more than 6 years ago | (#22899714)

This is like worrying now about what to wear on your 250th birthday. We won't see space elevators in my lifetime, in your lifetime, or in the lifetime of your grandchildren. We can't even come close to constructing even a tiny fraction of a percent of the material of the required strength for a space elevator. A bit of wobble is neither here nor there. And when we do have the technology to make such material in bulk, we'll have already figured out countless solutions to the problem of wobble and most humans will probably think of space elevators as a fun way to get *down* to the old planet their ancestors used to live on rather than as a cheap way to get stuff into space. Next up, the impact of proton decay on the stability of your home.

launch loops (4, Informative)

nguy (1207026) | more than 6 years ago | (#22899834)

It seems to me that, at this point, launch loops [wikipedia.org] are a much more realistic and practical choice for a launch structure than space elevators.

Unlike space eleveators, launch loops require no exotic materials (just iron and steel), are essentially self-erecting, are anchored, and accelerate people quickly through the radiation belt.

We could probably build a launch loop in a decade or two, if we embarked on an Apollo-like program.

The Stealth Fighter and Bomber Are Unstable, Too (3, Interesting)

curmudgeon99 (1040054) | more than 6 years ago | (#22899842)

The Stealth Nighthawk fighter could not be controlled by a human, it is so aerodynamically unstable. But with the help of some good software, that plane flies. The same is true of the B-2 Batwing bomber, it only flies because a computer stabilizes it.

There will be controllable vanes (for the atmosphere) and thrusters (for space) to control the car's behavior. The wobble would be predictable and all the traffic would be required to avoid it, in the same way power boats are required to steer around sailboat.

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