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Space Elevator Challenge
MattSparkes writes "For the second year in a row, no team has won the $200,000 prize in the Space Elevator Challenge at the Wirefly X Prize Cup. Three teams were disqualified before the contest even started. Another competition at the event has been held up by confusion. Incredibly, it seems the organisers of the competition are not sure whether the ribbon used was 50 or 60 metres long, and whether any team completed the climb fast enough to win."
Maybe so, but I don't see anything here which will realistically form a part of a real space elevator system. Its a bit like building a railroad but starting out with model trains.
http://michaelsmith.id.au
The structure of the elevator isn't the only technology that has to be developed. We also have to make a climber that can go up a thin strand of material and hold wait, as well as a way to power it. Not all of these require carbon nanotube robes to build.
Does a line appended to your comment give your post meaning in and of itself, or only in relation to those without?
I think that the material to make the ribbon can't actually be produced yet, and a 50-60 metre long section is about all that can be used. However, for the purposes of a test like this, it will suffice. The competition is more to do with getting the elevator technology advancing than actually putting together a working device.
Matthew Sparkes
No such structure could withstand the tensile stress generated from being pulled at opposite ends 25,000 miles apart. Just to put some perspective here, a the length of a space elevator, depending on which source you quote is at the minimum over 3 times the diameter of the Earth itself!
I've been in the research & development business for pretty much my entire adult life. This, more or less, is what we do except on a different scale. I don't see anything wrong with building models of things in order to understand them more fully. Rather than attempting to solve the whole of the problem in one go they are trying to solve the parts of the problem that are solvable with today's material technology. Given a few more years doubtless the material engineering will begin to catch up and you will see things that realistically could be used in true space elevators.
Nothing in the world is more dangerous than sincere ignorance and conscientious stupidity.
So you are saying that tether might be possible to be made so light and strong - but no way simple tower construct would achieve the same??
Yes. The tether is kept under tension, rather than compression. Different material properties in question. As I said, a tether with an orbiting counterweight has to support less of its own weight than a compressional tower does, due to the centrifugal force.
While a material with appropriate tensional properties for a tether is hard to achieve, a material with appropriate compressional properties for a tower is even harder to achieve.
But how heavy it would have to have?
That depends on the design. Some designs have counterweights on the order of 100-1000 tons.
I shiver to even think that thing might alter (or even de-orbit) Earth.
It's in high orbit (above geosynchronous). It can't just "deorbit" and fall on us; there isn't any atmospheric friction to speak of. It would require enormous energy to alter its orbit to intersect the Earth. You might as well worry about the Moon falling on us.
It kind'a reminds me of other problem, since again we forget about balance.
What the hell are you talking about?
In theory, that's true. In practice, however, science fiction has been a pretty good predictor of technology to come. It's not 100% (yet), but quite often, the 'super high tech' stuff of sci-fi is developed a few hundred years *before* the sci-fi predicted it would be. As for most of the rest? Well, we're running a bit late on actually *using* flying cars, but the technology for them exists.
You too can try the experiment!
Step 1: you need a long pendulum with a heavy bob, hanging a string from the suspended ceiling at work is a good plan, and you stapler is about the right weight.
Step 2: you need another heavy weight about 2 feet up from the first to simulate the wieght of the station. Borrow your neighbor's stapler too.
Step 3: get the pendulum swinging at least a yard in either direction. Now try to stop it from swinging, but you're only allowed to push on the middle of the string, and you have to push in the same direction for several back-and-forth cycles of the pendulum.
Step 4: OK, that was a bad place for your monitor, pick it up off the floor and put it on a different spot on your desk. It probably still works.
Step 5: explain to your boss the redeeming scientific value of this important experiment!
If we ever want to build an elevator on Mars, we'll just have to grab Phobos and use it as the counterweight, because sadly the elevator will be swinging in the wrong plane to dodge Phobos.
Socialism: a lie told by totalitarians and believed by fools.
Those are loose nanotubes. I have another experiment for you: Get a 3" square of some copper screen, made with a fairly small wire. Try to melt the center of it with a lighter; experience defeat. Now pull one wire out of the mesh, and try to melt it with a lighter. You will succeed. In that moment, the student will be enlightened.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
The presence of a 1000-ton mass beyond geosynchronous orbit will have an utterly, utterly negligible effect on the Earth's center of gravity or on tidal forces.
Take tidal forces, for instance. The distance geosynch orbit is about 40,000 km (I'm rounding up to 1 sig fig); the radius of the Moon's orbit is about 400,000 km. Since the counterweight is 10x closer to the Earth than to the Moon, that increases its tidal strength by the cube root of 10, or about a factor of 2. However, that is offset by a 10^20 reduction in mass. So the tidal forces due to the counterweight would be almost a billion trillion times weaker than those of the Moon.
The counterweight used in many space elevator designs is not that much more massive than the International Space Station. That certainly doesn't produce significant gravitational effects, despite being in low Earth orbit instead of geosynch. Hell, even a typical-size asteroid in low Earth orbit wouldn't produce significant gravitational effects at the Earth's surface.
Once the payload is released from the cable, it will need additional thrusters to move it away from the elavator, adjust it's orbital height, orbital plane, and LAN.
First, there actually *is* friction. So it's obvious the elevator would not swing forever. Second, you claimed that each cargo sent up would tend to strengthen the swinging, until something breaks. That's also not true. That *would* be true if the cargo was sent up and released at the worst possible moment.
In the best case, two following cargoes cancel exactly. Like this:
First cargo goes up, presses top eastwards, whereafter the top swings westwards to neutral, and *would* overshoot to go an (almost) equal distance westward. Except you send up cargo 2 with such timing that it's eastward pressure cancels the westwards motion of the elevator, so that at the moment you release cargo 2, the elevator is both vertical, and at rest.
In practice, there's likely to be many cargoes on the way up at any given time, this acts a lot more like a *constant* eastwards pressure. (in the limit, infinitely many infinitely small cargoes, it *would* be a constant pressure)
You *do* need to take care that you don't put energy *into* the standing waves that will inevitably build quicker than the energy dissipates. That can be taken care of in two ways (or a combination thereof).
Put less energy in. (by timing, by size of cargo, by equal-symetrical-shipping whatever)
Or make the energy dissipate faster, by passive means (increase friction, dampeners) or active means (ion-trusters at top , or movement of the bottom-point that actively work against the waves, for example)