MSNBC: Space elevator prizes stay out of reach
A competition to develop space exploration tools for NASA produced no grand prize winners on Sunday, but officials said the event successfully sparked interest in aerospace technology.
Order of Kilopi
MSNBC: Space elevator prizes stay out of reach
A competition to develop space exploration tools for NASA produced no grand prize winners on Sunday, but officials said the event successfully sparked interest in aerospace technology.
Order of Kilopi
For those of you who keep pushing the idea of the elevator...see...see...see.
We're not there yet, and we have a long way to go.
(Just to re-iterate: I'm not against developing a SE, I just don't like to hear that it's within our grasp)
Newbie
Folks:
After reading the article I gather there is quite a ways to go with the idea of a space elevator. But on the other hand remember the first DARPA robot car race was a smashing, uh sorry for the pun, failure. This year's event went much better with several cars finishing the new course. So only time will tell.
I still think the low-ball quotes in one of the recent articles on space elevators (sorry, my brain is failing me - I think it was in an engineering journal?) do more harm to the cause than good. I really think its going to cost quite a bit to build a space elevator and we should expect more than a few setbacks along the way.
Marc
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I'd say it'll be 50 years before an SE is even possible. And it'll still be very, very expensive.
But I still think that it's a good idea.
Established Member
Regarding the cost issue, the initial cost would be a large number. What makes the SE attractive is that, ideally, the cost of putting any given pound into LEO is next to nothing.. over a fairly short term, the cost savings would pay for the SE.Originally Posted by The Supreme Canuck
However, aside from the elevator 'car', there are two significant issues - one that's solvable, one that, as far as MY imagination goes, doesn't seem to be.
1) Solvable: what the heck are you going to make the tower/teather out of? It has to be very strong, very light, and able to last a significant time in both atmosphere and vacuum (with all of the incumbent issues involved there)
2) maybe not solvable: the anchor point. I'm not an engineer, but I've read from one that the anchor-point stresses for something like this would be high enough to destroy a large mountain.. i.e. - any anchor would likely pull right out of the ground. I suppose we could dig a huge hole and fill it full of some solid metal - enough to counterweight the entire tower.. (maybe that's a good use for all the vehicles in junkyards right now...)
Maybe if we built the elevator to go out to geosync this wouldn't be an issue...
I admit, I'm rather fond of Dr Forward's variation on the SE... I believe he calls it a Rotovator. Elevator strand in orbit, rotating end over end. When one end point is at its maximal distance from the surface, the other is (obviously) at its nearest point. This point would be at some altitude above the surface - say.. 50K feet. Surface to elevator craft would transit that distance, carrying passengers and cargo. As elevator orbits earth, it could serve... um... I think it was 6.. 'spaceports'
Lurch
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How's the air down there?
Newbie
I'm not disagreeing with anyone, I think if it works the space elevator will be a HUGE boon to mankind. But, as the man said, the Devil is in the details . . .
I somehow get a feeling of deja vu, remember the "power too cheap to meter" claims for nuclear power way back when? Or, more on subject, the claims for the utility of the Space Shuttle vs. the reality - it sort of worked, but it certainly wasn't cheap. I suspect a space elevator is going to prove to be rather expensive to run, but I'm not really sure why.
Marc
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I really don't see how it would be expensive to run. I mean, there aren't really any moving parts. Building the thing, though...
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And when the thing breaks down, what's your alternate until you get it back up. At least with the shuttle, there's another one...er, um, well, a soyuz...
Established Member
Must be a misunderstanding. Basically there is no force on the anchor point at all. You could leave the elevator dangling in mid-air (say at 1 foot above ground level) and it would simply stay there because it is fully balanced around its centerpoint (which is in geostationary orbit, the counterweight is at 100.000 km). Of course, there are some forces introduced by wind and waves in the cable but that's a relatively minor issue.
Note that every SE with a fixed anchorpoint HAS to go to stationary orbit. An SE that does not have a fixed anchorpoint (and doesn't go to stationary orbit) is called a skyhook and its basepoint travels through the sky at pretty high speed. If you connect a skyhook to an anchor point it will pull the thing from the sky.
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Yeah right, if there weren't an atmosphere, maybe. Whip that bad boy up with a few strong breezes at higher altitudes and you've got a 23,000 mile long bullwhip on your hands. Secure anchoring to the ground and tension placed by the orbiting station might attentuate that a little, but woe to the person near the ground anchor when that baby goes TWANG!
The space elevator is a nice system on paper, but its ultimately impractical. Its too fragile, even compared to the space shuttle. You could take it out with a wing clip from an aircraft without any effort whatsoever, so unless you're ringing this thing with SAMs under orders to shoot down anything that gets within 10 miles, you're going to have some unstable whack job going after it eventually, whether for international terrorism or because its just so (expletive) cool at that particular moment. If the material's even slightly conductive, you can count on lightning strikes at every possible opportunity. And lets not forget the orbital debris field its passing through. You're not ducking and juking this thing to avoid every object over 4 inches in diameter you can track, at some point, somewhere, its going to take a direct hit. Unless you are totally disconnected to reality imagining we can clean up space or will just "get lucky", you're counting on this thing having an unknowable, but definitely limited lifespan before a major calamity unfolds.
Regrettably, a static target is just that, a target. The minute you start building it, its going to be in someone's crosshairs, be it a person of malicious intent or fate.
Established Member
Pardon my very limited knowledge on this, but it was my understanding that puting something into orbit required speed as well as altitude. If you released a satellite from a SE at ~200 miles up, wouldn't it drop straight back down?
Newbie
NorthGuy:
As far as I can recall, no one was suggesting that satellites be released at such a low altitude, I thought it was mainly aimed at geostationary satellites and launching things out of Earth's gravity. I would assume, however, it would be possible to build a package of a payload plus a (relatively) small booster rocket to bring the payload/satellite to its proper velocity. Remember, it already has some velocity due to the Earth's rotation (at least I think I got that right).
I'm not sure what the exact mechanics of such a system would be, I wouldn't want a rocket of whatever size igniting right next to the cable and its elevator. From the GEO point the payload could be moved to the support platform the cable is suspended from and launched from there. I also suspect it might be easier to start from the GEO platform and boost down towards the proper orbit, remember its downhill from GEO as far as gravity is concerned . . .
Marc
Established Member
I guess I was taking the over-simplistic approach since the proposed cost was "next to nothing." So are you're saying that puting satellites into low earth orbit via SE would still require some rocket-like technology? That still implies some amount of cost per launch. Or would "dropping" it from a high enough point, letting gravity do all the work, allow it to acheive orbit?
The great majority of launches, I believe, are to put satellites into Earth orbit. If we are looking to cut the cost of these launches to "next to zero," then I'm asking if that's really doable from an elevator. I guess I've worked in the busines and accounting world too long. If this thing gets built, I want to know the rate of return on investment.
Member
I agree that we are still quite a ways off from actually building a space elevator, but I don't think were as far off in developing the actual technology as some people think. It is my hope that in 10 years we will have worked out the developmental "kinks" and can start working on developing actual hardware. Another ten years and we can have a working elevator.
I also agree that this will no doubt be an expensive project especially the initial "first strand". If this can survive long enough to run multiple payloads up then it will decrease in cost from there.
The initial cable will be very fragile and precautions will need to be taken to prevent some nutjob from flying into it. I hope this will become less of a concern once redundancy is built into the system and multiple tethers can support the entire elevator. That way if one or more tethers are severed the whole thing won't come down and force us to start over.
Established Member
The beauracratic cost will be a nightmare, regardless. Think about how much trouble SpaceShipOne had getting permission to take off (regulatory hurdles). I'm sure the elevator will require thousands of staff handling all the paper work.
Mind you, if the SE actually is viable from an economic standpoint, then this "job creation" will only decrease its profitability - but the economy will still certainly benefit from its presence.
Member
In my opinion the space elevator is space technology that will become
obsolete before it is built- it is useless for travel to the stars
Igor
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Nope. As the payload goes up, it gains horizontal energy. When you release it in geostationary orbit, it'll sit right there, in orbit.
Established Member
The question was about releasing it at 200 miles up where the horizontal component of its velocity is not sufficiently large. It would drop unless it had a means of attaining the correct horizontal velocity component.When you release it in geostationary orbit, it'll sit right there, in orbit.
There may be additional forces contributed by sections of the ribbon that have velocities not commensurate with the "free fall" velocities of their respective altitudes. Also lack of precise circularity and Earth equatorial alignment of the orbit of the center of mass of the SE and the variation of the combined gravitational effects of the Sun and Moon will cause the forces on the ribbon to vary. As any substantial load is raised, it must be counterbalanced to avoid the center of mass being displaced from the GEO altitude or adequate compensation of the additional tension provided.
It is not clear how we deal with wind and/or lightning nor, if the anchor floats, how we deal with rogue waves or passing tsunamis.
Last edited by GOURDHEAD; 2005-Oct-26 at 01:10 AM.
Order of Kilopi
Oh, crud. I read ~20 000 miles, not ~200. Disregard...
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And you still need a big rocket to put it up there.
Established Member
Did you read what the competition goals were? One (at least) of the prizes was for a non-rocket method of ascent. Don't need a rocket, if one of these universities crack the problem.
Established Member
But it is perfect for travel from the Earth to the beginnings of space. It is a much better launch platform, not a space travelling machine, and if you want to travel to the stars, you'll need a launch platform (unless some extremely new technology is developed like Stargates and so on, but I wouldn't count on those). So I don't see why it would become obsolete.
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In my opinion, the fist thing to tackle is the tether. Right now we don't have anything that can support its own weight over such a length. A copper wire breaks at 1.3 km length due to its own weight IIRC. Geostationary is 32000 km. I read there must be a counterweight at 100000 km. That's almost 100000 times larger strength/weight ratio than a solid copper wire, and then there's still no load hanging on the tether! I know that copper is not really strong, but it's just a comparison.
Please correct me on any wrong numbers/reasoning, as this is just from memory.
Last edited by Nicolas; 2005-Nov-10 at 08:05 PM.
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We will see anti-gravity work before we ever see a space elevator.
Member
About the tether, what material can be used? I thought carbon nanotubes were the main candidate. They can be 100 times stronger then steel, but in a documentary, Dr. Edwards from Carbon Designs Inc. suggests 30 times will do the job. Is that the absolute minimum in strength for building a space elevator?
http://www.azonano.com/news.asp?newsID=808
"LiftPort Group, the space elevator companies, has announced plans for a carbon nanotube manufacturing plant, the company's first formal facility for production of the material on a commercial scale." April 28 2005
http://www.azonano.com/details.asp?ArticleID=1108
http://www.liftport.com/
http://www.nanotech-now.com/nanotube...ball-sites.htm
Order of Kilopi
I don't think it can be expressed only in strength. The weight of the tether is also of big importance, as most materials break under their own weight at a length shorter than a space elevator. Possibly CNT tethers have a strength/weight ratio large enough to permit space elevator use, but I'm not sure about that.
Currently, the only material suitable for building a space elevator tether is unobtanium as it seems...
Order of Kilopi
This is what they say about CNT wrt space elevators. Let's hope the eleavtor works with theory and not with practiceCarbon nanotubes (CNT), discovered in 1991, are almost certainly strong enough. Theory says that they are 3-5 times as strong as we need them to be, and laboratory measurements of their strength, though very difficult to do and not yet definitive, have shown more than half the strength we need.
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