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Continued Success for Space Elevator Tests
Jacki O writes "According to their Web site the Space Elevator company Lifport recently managed to get their platform and climbing robot to the mile-high mark over the Arizona desert." From the announcement: "A revolutionary way to send cargo into space, the LiftPort Space Elevator will consist of a carbon nanotube composite ribbon eventually stretching some 62,000 miles from earth to space. The LiftPort Space Elevator will be anchored to an offshore sea platform near the equator in the Pacific Ocean, and to a small man-made counterweight in space. Mechanical lifters are expected to move up and down the ribbon, carrying such items as people, satellites and solar power systems into space."
A little progress is better than no progress.
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Regardless of how many descriptions of a space elevator I read, I can not grasp a visual of the process. Anyone have a video of something like the post topic?
Bury me in mashed potatoes.
The eventual plans are for a 62,000-mile cable. So they've made it 1/62,000th of the way there, or .00161% of the way. Keep walkin', boys.
One issue I have yet to see addressed is the issue of speed. Rockets make it up to geosynchronous orbit (22,240 miles) very quickly by moving really, really fast. Somehow, I don't think a robot climbing a ribbon will be very fast. Even at 1,000 mph, it'll take almost an entire day to get there. I don't know what the actual expected speeds will be, but I don't think that anything over 100 mph will be practical in the atmosphere due to wind resistance. And once you get out of the atmosphere, you have no easy way of dissipating the heat from friction.
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Perhaps the point is that the first mile is significantly more difficult than the next 61,999?
Far from it. All of the components of a space elevator will be revolutionary, not just the ribbon. The climber's mechanical parts have to work flawlessly for about 100,000 km. The actual problem of gripping a cable isn't trivial, either. And it needs to be very low weight. Oh, and very low power. And just to make things even more fun, it'll need to work in vacuum as well.
If you read some of the papers on concerns for the climber at the space elevator conference, you realize that there's nothing easy about this. It's unsurprising that the climber is seeing the most progress first, but that first concern (perfect reliability over 100,000 km) will take a long time, so better to start now.
Speed is largely irrelevant. For most payloads, humans won't be required. For a significant portion of payloads where humans are required, imagine that the "counter-weight" is actually a space station. With humans on board that space station, most payloads won't need to send humans up the line.
The cost savings are significant, which may lead to greater use (even from countries without space programs of their own), which may lead to economies of scale and the production of additional space elevators.
What I want to know is how they're going to manage to avoid all that space debris.
there would be plenty of time to recover and string a new tether.
What I have always wondered is if anyone has calculated how much the Earth's rotation is expected to slow down once we start sending mass up that thing. You know, like the ice skater who sticks her arms out to slow down and pulls them in to speed up? There's no such thing as a free ride, and the energy "savings" will eventually become apparent, it will have come from the Earth's angular momentum. I wonder what climate trouble we will have then.
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> Perhaps the point is that the first mile is
> significantly more difficult than the next 61,999?
Er...except it's not. As you leave the atmosphere there's temperature extremes...radiation...vacuum. Not to mention every mile you extend the elevator increases the strain the structure must support. The first mile is the *easiest*.
Chris Mattern
Only another 99.99954% of the way to go! . Wohooo!
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Really? Are you sure? Can you build a bearing for a 20-cm wheel that will be able to turn 500 million times with zero chance of failure? And can you do it lightly? And in vacuum?
While we don't have the ribbon yet, we don't have the climber, and we don't have the power delivery system either. That's why it's called inventing. They're doing something that hasn't been done before.
And when you've got multiple independent difficult problems, you might as well work on all of them at once. Which they are doing.
Go and read the talks on building the climber at the last space elevator conference before you call it "trivial".
Personally I'm surprised no one has tried just shooting things into space.
Oh, and I didn't see this. Fundamentally, this is a bad idea. First off, the idea of a modified Howitzer? That's just explosive propulsion. This is fundamentally the same idea as a rocket - it's just that a rocket is far, far more effective in terms of thrust per unit mass.
You could imagine electromotive propulsion - a rail gun - but the problem with that is that you're imparting all of your momentum in the thickest part of the atmosphere, at which point it would just be bled away as air resistance. You'd need to supply a ridiculous amount of energy to do it, and the craft would have to have a ridiculous amount of stress support and heat resistant material. It gets to the point where there is no way that it would ever be economically feasible.
On an atmosphere-free planet, though, it does become pretty feasible, though a space elevator is likely to be more generically useful for large cargo.
It will depend on where it breaks. Cut it at the counterweight and it will wrap itself around the earth pretty fast. The top will burn on re-entry, the bottom would be going so slow that it will be easy to get out of its way and even then it would no cause much damage, kinda like falling leafs since it is so light and has such a big section. You cut it at the base (on earth) and it will jump up by whatever tension it had at the bottom and if it goes high enough from the dense bottom part of the atmosphere then it may be possible to reattach it. If not it just may end up as a whipping mass but still with its CG in geostationary orbit. Cut it anywhere else and you get a mix. The stuff over the cut will go higher based on how much tension was at that point, and the stuff under will fall. It would make a VERY tempting target given the amount of money that would go into it and how little you'd need to make all that dissapear.
The challenges of a space elevator aren't in the climber; they're in the cable.
... well, large, but not unreasonably large. It would just cost a lot more.
C'mon. That's not true. The main reason it seems like this is because you think you know how to build the climber, but you have no idea how to build the cable. Ask a materials scientist who's working on carbon nanotubes, and they might disagree with you.
Plus, you do not need a 100 GPa cable. You need a 100 GPa cable for a small taper. At 50 GPa the taper becomes
There are a lot of issues with the climber design. A lot. Speed, reliability, weight, and power. Reliability in particular will take a lot of time to nail down. It makes sense to tackle that one first, because it can be done in parallel with the cable design, and in addition, the third major challenge (power delivery) can't really be done until the climber design is finalized.
So you've got three difficult tasks - the cable, the climber, and the power delivery system. The last two are coupled. What makes sense is having two separate tasks, one of which handles the cable, the other the climber, and then the power delivery system. Oh look! That's exactly what they're doing.
Given our lack of experience in building cheap vehicles that can travel 100,000 km with zero failures (with low power, in vacuum) I think it's safe to say that all parts of the elevator are difficult.
As much as the idea of a Space Elevator thrills me, the jaded side of me says this is just asking for trouble. It'll end up being way too big and tempting of a target for the next fanatical group. All that money and resources, taken down by a single looney with a bomb. Or a country/group group with a missile, maybe nuclear tipped (Anti-missile defense? Naw, we don't need to develop anything like that). Can't wait to see countries start arguing over control of the elevator, or some whacko regime take it out so that no one can have it.
No security is ever perfect, after all.
You have no idea how to build the cable
You're telling this to a person who's followed every bit of news she can get her hands on about SWNTs (and to a lesser extent, MWNTs and non-carbon nanotubes, plus novel interlinked structures).
50 GPa
You only get *realistic* taper factors at over 100GPa. I encourage you to check out spelsim or the gizmonics calculator. A 50GPa elevator weighs ten times as much as Edwards' calculation, and Edwards' calculation wasn't cheap. Even 50GPa isn't realistic, however. The strongest *individual* SWNT tested thusfar was just over 60GPa.
The cable is *not* realistic present-day. The climbers are. Hence, the climbers are non-issues until the cable becomes within the realm of possibility, which may be approximately around the year two-thousand-and-never. Try on a pair of my teleportation shoes - you'll like them.
You can't change that... by gettin' all... bendy.
I word things very carefully. Read it again. I said "planes can pretty much do that." I was actually thinking about commercial airlines, which fly above 72% of the atmosphere.
But, of course, there's this nugget from Wikipedia:
Balloons typically reach altitudes of 100K feet, which is above all but a fraction of a percent (it's a few Torr).
simply by building our velocity high enough to escape velocity while in the atmosphere and letting inertia take us out.
Ignoring that whole "air resistance" and "speed of sound" thing.
And curiously, if it wasn't for those two things, we could do that right now.
We use rockets for velocity, not altitude. If you doubt me, consider that the Space Shuttle's two solid rocket boosters shut off at lower altitudes than the X-15. Why don't we use a jet to boost the Shuttle to that altitude? Because the SRBs get the Shuttle to a much, much higher speed.
There's nothing "special" about Geosynchronous orbit which means you can "get the velocity from the Earth".
I get velocity from the Earth all the time. It's called standing on the ground. (Curiously enough, if I didn't, I would start flowing in these little circly patterns, called Hadley cells, which are what happens when you have a viscous medium gravitationally sitting on top of a rotating sphere. If the atmosphere extended enough, it essentially wouldn't be rotating.)
That's what special about geosynchronous orbit. Orbital velocity is slow enough that I can use the Earth's rotation to supply it.
You DO have velocity.
Which I got... from the Earth. Like, when a plane lands, after heading west, how the Earth speeds it up in a matter of seconds?
The idea is at that height, escape velocity is negligable.
It's not "negligible" - it's two thousand miles an hour (curiously, roughly 1 km/s). It's just neglible in the rotating frame of the Earth.
Nanotube ropes are *far* weaker than individual tubes, usually at somewhere between 5 and 15 GPa. They're weakly bound together by VdW and pi bonding. I could go into more detail on the other ways your analogy is flawed (we're talking about tensile stress, not shear; we're talking about gram per gram; we're talking about linearly staggered over a long distance, instead of continuous elements; and we're talking about nanoscale, not macroscopic for starters).
Liftport doesn't have a "get out of physics free" pass.
You can't change that... by gettin' all... bendy.
Your post makes me incredibly glad I learned physics using only metric units.
Megainches??? Do real scientists seriously use such a measurment?
-- If you try to fail and succeed, which have you done? - Uli's moose
So they spun it as a success because they bet their last lame effort.
They still have some way to go to make 62000 miles.
Centrifugal and Coriolis forces don't exist in an inertial reference frame, but are a necessary addition to real forces to make Newton's laws of motion work in a rotating reference frame. They are not only used by laymen; if it's easier to understand or calculate something in a rotating reference frame then scientists will use them. I've read that the calculation of the Lagrange points is easier done that way.
This quote from http://en.wikipedia.org/wiki/Centrifugal_force is perhaps instructive:
"Because rotating frames are not vital for understanding mechanics, science teachers often de-emphasize the fictitious centrifugal force that arises in a rotating reference frame. However, in their zeal to stamp out the misunderstanding of the term in this one case, they may try to expunge it from the language entirely."
I think it's a bit funny that every time centrifugal forces are mentioned, someone pops out of the woodwork to complain that they don't exist, but no one seems to mind explanations citing a Coriolis force. Both are pseudo-forces and have equal legitimacy.
a,e,i,o,u and sometimes w and y (at be if of up cwm by)
Thank goodness having 60,000km of 10E6psi cable floating around the earth, crossing the path of geosynchronous satellites used for a good portiona of all communications on this planet, wouldn't cause any foreseeable problems.
Is it just my observation, or are there way too many stupid people in the world?
it appears to me that you hold the belief that if you go straight up from the Earth, you'll keep rotating in line with the point you launched from on the surface.
:)
I will if I keep holding onto a giant pole. Which is what this is.